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Diurnal temperature range over Europe between 1950 and 2005


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It has been widely accepted that diurnal temperature range (DTR) decreased on a global scale during the second half of the twentieth century. Here we show however, that the long-term trend of annual DTR has reversed from a decrease to an increase during the 1970s in Western Europe and during the 1980s in Eastern Europe. The analysis is based on the high-quality dataset of the European Climate Assessment and Dataset Project, from which we selected approximately 200 stations, covering the area from Iceland to Algeria and from Turkey to Russia for 1950 to 2005. We investigate national and regional annual means as well as the pan-European mean with respect to trends and reversal periods. 17 of the 24 investigated regions including the pan-European mean show a statistical significant increase since 1990 at the latest. Of the remaining 7 regions, 2 show a non-significant increase, 3 a significant decrease and the remaining 2 no significant trend. The long-term change in DTR is governed by both surface shortwave and longwave radiation, the former of which has undergone a change from dimming to brightening. Consequently, we discuss the connections between DTR, shortwave radiation and sulfur emissions which are thought to be amongst the most important factors influencing the incoming solar radiation through the primary and secondary aerosol effect. We find reasonable agreement between trends in SO2 emissions, radiation and DTR in areas affected by high pollution. Consequently, we conclude that the long-term trends in DTR are mostly determined by changes in emissions and the associated changes in incoming solar radiation.
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Atmos. Chem. Phys., 8, 6483–6498, 2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.
and Physics
Diurnal temperature range over Europe between 1950 and 2005
K. Makowski, M. Wild, and A. Ohmura
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Received: 6 March 2008 – Published in Atmos. Chem. Phys. Discuss.: 9 April 2008
Revised: 13 June 2008 – Accepted: 30 September 2008 – Published: 13 November 2008
Abstract. It has been widely accepted that diurnal temper-
ature range (DTR) decreased on a global scale during the
second half of the twentieth century. Here we show however,
that the long-term trend of annual DTR has reversed from
a decrease to an increase during the 1970s in Western Eu-
rope and during the 1980s in Eastern Europe. The analysis
is based on the high-quality dataset of the European Climate
Assessment and Dataset Project, from which we selected ap-
proximately 200 stations covering the area bordered by Ice-
land, Algeria, Turkey and Russia for the period 1950 to 2005.
We investigate national and regional annual means as well
as the pan-European mean with respect to trends and rever-
sal periods. 17 of the 24 investigated regions including the
pan-European mean show a statistical significant increase of
DTR since 1990 at the latest. Of the remaining 7 regions, two
show a non-significant increase, three a significant decrease
and two no significant trend. Changes in DTR are affected by
both surface shortwave and longwave radiation, the former of
which has undergone a change from dimming to brightening
in the period considered. Consequently, we discuss the con-
nections between DTR, shortwave radiation and sulfur emis-
sions which are thought to be amongst the most important
factors influencing the incoming solar radiation through the
primary and secondary aerosol effect. We find reasonable
agreement between trends in SO2emissions, radiation and
DTR in areas affected by high pollution. Consequently, we
conclude that the trends in DTR could be mostly determined
by changes in emissions and the associated changes in in-
coming solar radiation.
Correspondence to: K. Makowski
1 Introduction
Satellite and ground based measurements for Europe show
that the mean surface air temperature has increased overall
during the second half of the last century (Trenberth et al.,
2007). For the 1950s and 1960s, a characteristic phase of
roughly no increase or even decrease is apparent. Since the
late 1970s an accelerated increase in the mean temperature
was observed. The slow increase of the mean temperature
followed by a rapid increase is especially evident during the
summer months (Trenberth et al., 2007) where the incoming
shortwave radiation is one of the most dominant factors for
the daily temperature development. This leads to the hypoth-
esis that changes in the incoming solar flux at the surface had
a discernible influence on the mean temperature development
between 1950 and 2000 (Wild et al., 2007). Measurements of
shortwave radiation at the surface, from stations around the
globe, have shown that the incoming flux has significantly
decreased and subsequently increased in many of the inves-
tigated stations within the last 4 to 5 decades (Ohmura and
Lang 1989, Gilgen et al., 1998, Liepert and Kukla, 1997;
Stanhill and Cohen, 2001; Roderick and Farquhar, 2002;
Pinker et al., 2005; Wild et al., 2005).
The diurnal temperature range (DTR) is considered a suit-
able measure to investigate the counteracting effects of long-
wave and shortwave radiative forcing, because the diurnal
minimum is closely related to the longwave radiative flux,
while the diurnal maximum is predominantly determined by
shortwave radiation (Fig. 1a). It is known that the DTR
has been decreasing since the 1950s on a global scale due
to a strong increase of the diurnal minimum (Karl et al.,
1984, 1993; Kukla and Karl, 1993). Comparison of GCM
simulations with observations have shown that the DTR de-
crease has been underestimated due to a strong increase in
the modeled maximum temperature (Braganza et al., 2004).
The change in DTR has formerly been addressed mainly
as consequence of cloud cover development, precipitation,
Published by Copernicus Publications on behalf of the European Geosciences Union.
6484 K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005
Figure 1. Sketch of mean diurnal temperature (T) cycle under a) weak anthropogenic
radiative influence, dominant radiative processes are denoted by arrows, b) enhanced
shortwave radiative cooling – “global dimming” (represented by the black arrows) and
long-wave radiative warming (represented by the grey arrows), and c) weakening
shortwave radiative cooling – “global brightening” (thinner black arrows) and continued
long-wave radiative warming.
(DTR: diurnal temperature range; T-MAX/-MIN: daily mean maximum/minimum; T-
MEAN: daily mean temperature, SW: shortwave, LW: longwave, ¨ T1/3: overall amount
of warming from state a) to c) or e.g. 1950 to 1990 respectively)
a) c) b)
Fig. 1. Sketch of mean diurnal temperature (T) cycle under (a) weak anthropogenic radiative influence, dominant radiative processes are
denoted by arrows, (b) enhanced shortwave radiative cooling – “global dimming” (represented by the black arrows) and long-wave radiative
warming (represented by the grey arrows), and (c) weakening shortwave radiative cooling – “global brightening” (thinner black arrows) and
continued long-wave radiative warming. (DTR: diurnal temperature range; T-MAX/-MIN: daily mean maximum/minimum; T-MEAN: daily
mean temperature, SW: shortwave, LW: longwave, 1T1/3: overall amount of warming from state (a) to (c) or e.g. 1950 to 1990 respectively).
change in irrigation and surface albedo or water vapor feed-
back (Stenchikov and Robock, 1995; Easterling et al., 1997;
Dai et al., 1997, 1999; Stone and Weaver, 2002; Vose et al.,
2005; Engelhart and Douglas, 2005). Many of the cited pub-
lications have concluded that neither of these factors alone is
likely to be the unique explanation of the observed changes in
DTR (Easterling et al., 1997). We argue that shortwave radia-
tion directly or via feedbacks is a major factor for the changes
in DTR since only the shortwave radiation – modulated by
the atmospheric aerosol burden – could exert a strong and
sufficiently homogeneous effect to change DTR on a global
scale (Liu et al., 2004; Wild et al., 2007).
The decrease of the solar flux and its relative cooling ef-
fect can been seen as a blocking action against the increase of
temperature caused by the greenhouse effect. Consequently
the diurnal maximum temperature remains constant while the
diurnal minimum is forced to increase (Fig. 1b). The re-
covery of surface solar radiation results in a removal of the
blocking on diurnal temperature development thus leading to
an increase of DTR and daily maximum respectively, thereby
revealing the full extent of global warming (Wild et al., 2007)
(Fig. 1c).
In the present study a detailed investigation of this issue
is conducted focusing on the European area where the best
coverage with observational data can be found.
2 Data and methods
We chose the data products of the European Climate Assess-
ment and Dataset Project (ECA&D-P) for an internally con-
sistent investigation of the DTR evolution during the recent
decades. It contains freely available data for more than 600
stations with minimum and maximum temperature measure-
ments in daily resolution for different periods between about
1800 and today (Klein Tank et al., 2002).
Because the change of incoming radiative flux at the sur-
face is considered very important to DTR development and
is measured since the 1950s, the complete second half of the
last century is investigated in this study. From the ECA&D-
P dataset, all stations with data for the period 1951 up to
2003 (or up to 2005 where available) were selected and na-
tional means were calculated. The time series of a station
was dismissed if it had more than five years with data gaps
or if two or more consecutive years were affected by these
gaps. In addition, each time series was checked for jumps
in the DTR. If jumps of more than half degree were caused
by filled data (from neighboring stations, performed during
ECA&D-P), then the value was replaced by an interpolated
value, on monthly basis, if the measurement from the original
site was available in the previous and following year. In total
less than 0.5% of the monthly values used in this study were
interpolated due to missing data. Systematic errors probably
due to data submission were found in all stations in Iceland,
Denmark and Romania. For Iceland all data after 1998, for
Denmark all data after 2002 and for Romania all data had to
be discarded and these were replaced by data which we ob-
tained directly from the respective national meteorological
service. For the region of the former Republic of Yugoslavia
(FRY) all data prior to 1956 had to be dismissed due to qual-
ity issues. For Poland, data are available only since 1966.
The temporal coverage was still considered sufficient to in-
vestigate decadal changes in DTR.
To obtain a sufficient number of stations for the calculation
of regional annual means (Fig. 2), station measurements were
grouped either nationally or by averaging over several small
nations. Netherlands, Luxembourg and Belgium were drawn
together as BeNeLux, likewise the states of the FRY; Estonia,
Lithuania and Latvia were grouped as Baltic States, Slovakia
and the Czech Republic to former Czechoslovakia (FCZS).
Conversely, Germany was divided into an eastern and a
western part according to the border line from the pre-1989
Atmos. Chem. Phys., 8, 6483–6498, 2008
K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005 6485
a c d b
e g h f
i k l j
q s t r
m o p n
u w x v
Fig. 2. Time series of annual mean DTR for each investigated region. All y-axes are scaled to 3 degrees Celsius for a better comparability.
Graphs are geographically arranged – except: surrounding regions of Europe as well as European mean are in the last row. The order of the
best suitable polynomial trend model according to Table 1 is indicated in brackets next to the name of the region and the investigated period.
Thick, grey, solid line presents 7 year running mean. The thick, black, dashed line shows the fitted trend model, if no black line is plotted
none of the models was significant above the 90% level.FCZS – former Czechoslovakia, FRY – Former Republic of Yugoslavia. Atmos. Chem. Phys., 8, 6483–6498, 2008
6486 K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005
Fig. 3. Distribution of statistical significant, fitted DTR trend models. Blue – linear (all trends are negative), red – second order (all trends
show first a decrease, then an increase), green – third order (all trends show first an increase, then a decrease, then an increase) orange –
forth order polynomial. Numbers are the year of reversal from decrease to increase in the 7 year running mean, derived from the annual
mean DTR of region/country where denoted. The uncertainty of the actual year of reversal can be inferred from Fig. 4. The trend model is
not significant (>90%) if the numbers are in brackets, consequently the investigated region is also not color-coded (Spain, Eastern-Germany,
Benelux). Blue crosses represent stations investigated.
period. This is to take account of the different development
of atmospheric aerosol burden in the two countries, which
depends mainly on the industrial emissions within the range
of some tens to hundreds of kilometers upstream. The overall
resulting data coverage is indicated by the small blue crosses
shown in Fig. 3, identifying 189 (168 with coverage 1956–
2003) out of the original 604 ECA&D-P stations satisfying
the criteria described above.
Subsequently these national annual mean time series were
fitted by polynomials up to fourth order, to facilitate the char-
acterization and quantification of the DTR trend (Fig. 2).
The rational for fitting polynomial trend models was investi-
gated by applying multiple regression analysis and control of
lagged autocorrelation within the residuals to assure station-
ary white noise. The regression analysis, followed by calcu-
lation of statistical significance level (1 – P-values; given in
%) based on a standard T-test was performed for every co-
efficient for fits between first order (linear) and fourth order
polynomials as summarized in Table 1 (for further details see
reading example, Appendix A1).
For most regions R2increased together with the statistical
significance of the fitted model, hence making it easy to de-
cide which of the investigated models performs best. If the
comparison of R2and p-values (significance levels) showed
an ambiguous result (see e.g. Table 1, line 5, Denmark), the
residuals were checked in more detail and the model with
the lowest autocorrelations in the residuals was selected (not
shown). Note that only models with no significant autocor-
relations were accepted. The annual mean time series to-
gether with the fitted trend curve and the seven year running
mean trend for all investigated regions as well as the Euro-
pean mean are shown in Fig. 2.
Further information for each time series was obtained by
estimating the year of reversal from decreasing to increasing
DTR (applies not to regions with linear trends). The estima-
tion was performed by calculating the minimum in the seven
year running mean (Fig. 2) for the period 1965 to 1995. For
the example of Finland (Fig. 2c), the running mean given as
gray bold line shows a clear local minimum in 1989 (com-
pare year given in Fig. 3 and diamond at the row “Finland”
in Fig. 4). The particular period 1965 to 1995 was chosen
since it embraces the whole era of reversal from dimming to
brightening (Wild et al., 2005). The results are presented in
Fig. 3 and Fig. 4. The numbers displayed in Fig. 3 give the
year of the minimum of DTR. If they are printed in brackets
no significant trend could be estimated (compare Table 1).
In addition to the minimum DTR value between 1965 and
1995, all values within the lowest 10% of the difference be-
tween maximum and minimum (7 year running mean) value
within that period have been calculated to give additional in-
formation on the distinctness of the reversal. In Fig. 4 the
years below and equal to the 10th-percentile are marked with
dashes, diamonds show the minimum (for further details on
the method see detailed example, Appendix A2).
Atmos. Chem. Phys., 8, 6483–6498, 2008
K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005 6487
Table 1. Data for each investigated region, including overall Europe and each trend type. Order: Western Europe N–S; Eastern N–S,
surrounding regions, Europe; Columns from left to right: (1) Name of the region, (2) R2and significance codes for each coefficient (–: <90%,
o: 90%–95%, x: 95%–99%, xx: 99%–99.999%, xxx: >99.999%), columns (3) to (5) equal to column (2) but for higher order polynomial
fits, (6) number of stations for the mean calculations, and (7) data period (for more details see example in Appendix A1). R2’s in bold denote
the best suitable model according to R2, significance and residuals (not shown), which was subsequently used in Fig. 2. FCZS – former
Czechoslovakia, FRY – Former Republic of Yugoslavia.
1st 2nd 3rd 4th No. Period
Norway 0.15 xx 0.17
0.26 o
0.32 x
4 51-05
Sweden 0.15 xx 0.15
5 51-03
Finland 0.01 0.25 xxx
xxx 0.27
3 51-05
Great Britain <0.01 0.14 xx
xx 0.14
3 50-05
Denmark 0.06 o0.18 xx
x0.30 –
5 50-03
East Germany (DDR) <0.01 <0.01
12 50-05
West Germany (BRD) <0.01 0.12 x
13 51-05
BeNeLux <0.01 0.02
9 51-05
Alpine 0.01 0.24 xxx
xxx 0.25
2 50-05
France 0.02 0.11 x
25 50-05
Italy 0.03 0.42 xxx
xxx 0.52 xxx
4 51-03
Spain 0.02 0.05
9 51-05
Portugal 0.05 o0.05
0.12 –
3 50-05 Atmos. Chem. Phys., 8, 6483–6498, 2008
6488 K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005
Table 1. Continued.
1st 2nd 3rd 4th No. Period
Russia & Belarus 0.02 0.02
0.22 xx
36 50-03
Baltic States 0.13 xx 0.15
9 50-04
Poland 0.07 o 0.17 o
2 66-05
FCZS 0.02 0.03
0.16 x
3 51-04
Ukraine 0.37 xxx 0.37
9 51-05
FRY 0.08 x0.11
0.26 x
4 56-04
Romania 0.01 0.05
0.13 x
19 61-05
Iceland 0.07 o0.07
0.18 x
4 51-05
Algeria 0.17 xx 0.19
0.37 xx
0.37 o
3 50-05
Turkey <0.01 0.04
0.13 –
3 50-04
Europe 0.01 0.14 x
168 56-03
3 Results
In the following section we discuss annual means of the
DTR records, starting with the regional averages as described
above, followed by a description of the European mean. The
data records and polynomial fits determined in this analysis
are compiled in Fig. 2.
By the use of regional averages we aim to underline the
hypothesis that DTR is affected by changes in regional emis-
sions influencing shortwave radiation reaching the ground.
Detailed information for each country or region can be found
in Table 1 and Figs. 2–4. A complete description of all re-
gions (except the European mean, see below) shown in Fig. 2
is provided in Appendix B.
Atmos. Chem. Phys., 8, 6483–6498, 2008
K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005 6489
For most of Western Europe a distinct reversal from de-
creasing to increasing DTR is visible. The fitted polynomial
trends are significant in the Great Britain, Germany, Poland,
Finland, France, Italy and Switzerland/Austria. For Spain
and the Benelux an alike development of decrease and in-
crease in DTR can be seen from the running mean but the
fitted polynomial trends miss the 90% significance level.
Circumjacent countries, as Portugal, FRY, FCZS and Nor-
way show trends significant at the fourth order polyno-
mial with pronounced periods of increasing DTR in recent
decades. In North-Eastern Europe a region covering Sweden,
the Baltic States and the Ukraine, with a continued decrease
in DTR can be identified. All decreasing linear trends are
significant at the 99% level.
The countries located farther away from central Europe,
namely Russia, Belarus, Turkey, Algeria and Iceland show
trends which are best described by a third order polynomial.
All coefficients for all trends are significant at the 95% level
except for the first (not significant) and second coefficient
(90% level) of Turkey. In addition to the presently increasing
DTR a prominent feature in the annual mean time series of
the above mentioned countries is a second, earlier increase
in DTR between 1950 and 1960 which is addressed in more
detail in the discussion section.
Overall, the farther away the country is located from cen-
tral Europe the more recent is the time of reversal from de-
crease to increase of DTR. The earliest can be found in the
UK (1967) and Germany (1967), the latest in Iceland (1987),
Turkey (1990) and Russia (1992). From Fig. 4 extended pe-
riods of reversal can be seen in Romania, Norway and Den-
mark. For Romania, which is an outlier compared to the sur-
rounding nations, the early appearing of the lowest value in
the 7 year running mean is put more into perspective by the
“error bars” in Fig. 4, equally true for the late reversal in
Norway and the early one in Denmark.
For the European geographical mean between 1956 and
2003, 168 stations were used. To avoid biases, series shorter
than this period have been excluded. The European trend
is best described by a second order polynomial (Fig. 2x).
Both coefficients are significant at the 95% level. The rever-
sal from decrease to increase takes place in the early 1980s.
This overall character of the averaged European DTR is even
strengthened if shorter data series such as those from Roma-
nia and Poland were included (alternative mean not shown).
4 Discussion
The extent of the DTR is determined by many different fac-
tors, such as surface solar radiation or sunshine duration,
cloud cover connected with changes in large scale circula-
tion or aerosols, soil moisture and water vapor content of the
Change in water vapor for example leads to an asymme-
try in the DTR (Stenchikov and Robock, 1995) by changing
Fig. 4. Reversal of 7 year running mean DTR trends. Diamonds
represent the year of reversal of DTR as calculated from 7 year run-
ning mean trend. Dashed lines show additionally the period covered
by values within the lowest 10% of the amplitude of maximum DTR
minus minimum DTR (of seven year running mean values) for the
period 1965–1995. For more details see example in Appendix A2.
FCZS – former Czechoslovakia, FRY – Former Republic of Yu-
longwave and shortwave downwelling fluxes. A continued
increase in water vapor due to anthropogenic influence would
lead to a slightly reduced downwelling shortwave and in-
creased downwelling longwave radiation at the surface. This
would consequently lead to a continued reduction of DTR
which, however, we did not observe in the investigated area,
and therefore do not consider water vapor as a major factor
influencing DTR in Europe.
Soil moisture plays an important role by damping the DTR
as energy is consumed by evaporation during the daytime and
released by condensation during the nighttime. However, ac-
cording to Robock and Li (2006), long-term changes in soil
moisture are coupled to changes in solar radiation and tro-
pospheric air pollution respectively at least on regional scale
in Russia and the Ukraine, where long-term records of soil
moisture data are available.
For the inter-annual variability of DTR the total amount of
cloud cover as well as the cloud optical properties play an im-
portant role again by altering longwave and shortwave down-
welling fluxes (Karl et al., 1993). Clouds alter DTR mostly
by damping the daytime maximum via a strong reduction of
surface solar radiation, while the influence on the nighttime
minimum seems to be rather small (Dai et al., 1999). Apart
from local convection, long-term changes in cloud cover can
be connected to large scale circulation patterns and aerosols.
However, the correlation between DTR and cloud cover in
Europe for the period 1910 to 1990 is only 0.35 according to
Dai et al. (1997). Atmos. Chem. Phys., 8, 6483–6498, 2008
6490 K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005
For the long-term influence of changes in large scale cir-
culation Sanchez-Lorenzo et al. (2008) show that in Western
Europe on a seasonal scale, circulation may have an influence
on the long-term development of sunshine duration, which
can be used as proxy for surface solar radiation (Stanhill and
Cohen, 2005). Still for the overall annual mean long-term
trend in sunshine duration, they identified changes in sur-
face solar radiation from anthropogenic aerosol emissions as
a more likely explanation.
To sum up, factors influencing surface solar radiation and
factors that are influenced by surface solar radiation seem
to account for the most of the changes in DTR in Europe.
Consequently, we consider changing surface solar radiation
as a major cause for the different types of DTR development.
Since solar radiation incident at the top of atmosphere
has not changed substantially during the investigated period
(Beer et al., 2000), two different candidates are likely to have
influenced surface shortwave radiation, namely clouds and
aerosols (first and secondary effect). Norris and Wild (2007)
showed that by removing the cloud cover influence from
surface solar radiation data, the reversal from dimming to
brightening becomes even more pronounced for most of Eu-
rope. Consequently cloud coverage changes acted as a dis-
guise rather than a cause for the variations in surface solar
A much more likely candidate for the varying surface so-
lar radiation and DTR trend types and their time shifted
reversals are different patterns of emissions, leading to re-
gionally differentiated backscattering of solar radiation by
aerosols. A reduction of incoming radiation has been re-
ported by Liepert and Kukla (1997), Gilgen et al. (1998)
and Abakumova et al. (1996). Wild et al. (2005) reported
a reversal from global dimming to brightening in mid to late
1980s at widespread locations throughout the world. From
Abakumova et al. (1996), a reduction in incoming shortwave
radiation until at least 1990 is evident for the specific region
of Russia. These results indicate that changes in surface so-
lar radiation were found in many regions though they do not
have to be necessarily simultaneous. The global background
signal and forcing from aerosol as presented by Mishchenko
et al. (2007), showing a general decrease during the 1990s,
can be dominated by local influence as described by Alpert
et al. (2005). Publications from Stern (2006) and Lefohn et
al. (1996) assume that a reversal from increase to decrease
of Eastern European emissions (dominated by Russia) takes
place in the late 1980s or early 1990s. In contrast, West-
ern European emissions are peaking already during the early
1970s according to Smith et al. (2004), Streets et al. (2006)
and Stern (2006). This is confirmed in Mylona (1996) and
Vestreng et al. (2007) who have shown that the maximum in
SO2emissions from fossil fuel for early industrialized coun-
tries, such as the UK or the former Federal Republic of Ger-
many, can be as early as the second half of the 1960s.
4.1 DTR, radiation and emissions – the biggest European
In the following section we discuss the qualitative connection
between trends in SO2emissions, sunshine duration, radia-
tion and DTR in several examples. We included the annual
sunshine duration in this section as a proxy for surface solar
radiation (Stanhill and Cohen, 2005), which is only available
for a sufficient number of sites since the 1960s. Sanchez-
Lorenzo et al. (2007 and 2008) provide data for sunshine
duration in Western Europe between 1938 and 2004. SO2
emissions at land level are available from Mylona (1996) and
Vestreng et al. (2007). Vestreng et al. (2007) is partially a
succeeding work of Mylona (1996) and both provide SO2
emission estimates for every fifth year. Therefore, we com-
bined the estimates to one time series if they cover the same
source region. Data from Mylona (1996) are available be-
tween 1880 and 1990, Vestreng et al. (2007) provide data be-
tween 1980 and 2004. For the overlapping period between
1980 and 1990 the data from Vestreng et al. (2007) were
favored for the following analysis. Further SO2estimates
can be derived from Lefohn et al. (1996). They provide an-
nual estimates of sulfur emissions between 1850 and 1990.
Obviously not all sulfurous emissions will be in the form of
SO2but still we converted all sulfur into SO2for the gain of
a much simpler comparison against the Mylona (1996) and
Vestreng et al. (2007) data. Valuable information on trans-
boundary fluxes and trend development of SO2since 1980
can be obtained from Klein and Benedictow (2006). Data
from long-term surface solar radiation measurement can be
found in Ohmura (2006). A recently submitted paper from
Gilgen et al. (2008) provides additional information on rever-
sal years and overall trends from gridded data of the Global
Energy Balance Archive. To make the characteristics of the
DTR time series more easily comparable against the rather
slow changes of emissions and the low pass filter data of sun-
shine duration, we calculated the eleven year running mean
of the annual DTR time series. The miss weighting at the
edges was indicated by using dashed lines (Figs. 5 and 6).
The emissions of SO2were plotted upside down to indicate
the potential sulfate aerosol forcing on DTR.
According to Berge et al. (1999) the 10 biggest emitters
(in total t/a) in Europe are: Bulgaria, France, Germany, Italy,
Poland, Spain, Great Britain, Ukraine, Russia and the Czech
Republic (or FCZS). Except for Bulgaria and Italy all coun-
tries above were analyzed with respect to their DTR trends
and will be discussed subsequently in more detail beginning
with the Eastern European countries, from south to north.
The best fitting trend for the Ukrainian DTR time series
is a linear trend with a slope of 0.014C/a, emphasizing a
continuous decrease (Fig. 2l). A more detailed inspection of
the running mean in Fig. 2l and Fig. 5a reveals, however, a
tendency towards an increase around 1978 which is reverses
to a continued decrease from 1987 onward. Data for emis-
sions are available from 1980 (Mylona 1996 and Lefohn et
Atmos. Chem. Phys., 8, 6483–6498, 2008
K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005 6491
Figure 5. Sketch of mean diurnal temperature (T) cycle under a) weak anthropogenic
radiative influence, dominant radiative processes are denoted by arrows, b) enhanced
shortwave radiative cooling – “global dimming” (represented by the black arrows) and
long-wave radiative warming (represented by the grey arrows), and c) weakening
shortwave radiative cooling – “global brightening” (thinner black arrows) and continued
long-wave radiative warming.
Fig. 5. Time series of annual mean DTR and SO2emissions. Eleven-year running means of DTR, expressed as relative (rel.) deviations from
the 1971–2000 mean, are plotted as solid black line. Differently weighted first and last five years of the time series are denoted as dashed
black lines. SO2emissions from Mylona (1996) (2) and Vestreng et al. (2007) (2) were plotted up side down, to indicate the presumed
forcing. Estimated sulfur emissions from Lefohn et al. (1996) (3) were converted to SO2 equivalent and also plotted upside down. All SO2
estimates are expressed in megatons per year.
al., 1996 estimated their values for the Union of Soviet So-
cialist Republics – USSR), showing a distinct decrease since
1990 which is not reflected in the DTR data. However, the
previously described short increase and decrease of DTR is
reflected in a short decreasing and increasing period of SO2
emissions. Surface solar radiation measurements for Odessa
show a decrease from 1960 until 1987 (end of data). The
described short increase in DTR between 1978 and 1987 is
mirrored as well in the radiation time series plot (Abaku-
mova et al., 1996 (Fig. 4), most evident between 1977 and
1983. To summarize, the continued decrease in DTR since
1980 cannot be explained by a continued increase of national
emissions. However, the findings are not contradictory with
respect to the connection between DTR and radiation (for
further details on the Ukraine, as an example for linear de-
creasing trends, see Sect. 4.3).
For the FCZS, data of emissions are available for the
whole period from Mylona (1996) and Vestreng et al. (2007).
The highest values occur around 1980 in line with the re-
versal of DTR from decrease to increase which is calculated
around 1977 (Fig. 4 and Fig. 5b). In Gilgen et al. (2008) the
reversal of surface solar radiation from dimming to brighten-
ing is estimated between 1978 and 1983.
Daily maximum and minimum temperature for Poland is
available since 1966. The reversal from decrease to increase
is calculated at 1977 in the seven year running mean. The
running mean of the Polish time series (Fig. 2g and Fig 5c)
shows a short increasing and subsequently decreasing period
between 1975 and 1986. The reversal of the second order
polynomial fit to DTR which omits the described hump is
between 1980 and 1985, this is close to the peaking of emis-
sions in 1985. Consequently, both reversals are consistent
with the reversal in incoming shortwave radiation in 1980.
Russian emissions peak at 1975 according to Vestreng
et al. (2007). Other emission estimates as e.g. from Stern
(2006) and Lefohn et al. (1996) suggest that the decrease
of emissions started much later namely in the late 1980s
(Fig. 5d) with the breakdown of the former Soviet Union.
However, the significant decrease of emissions after the col-
lapse of the Eastern Bloc is reflected in all cited emis-
sion estimates. The DTR decrease for Russia lasts until
1990 consistent with the decrease in surface solar radiation Atmos. Chem. Phys., 8, 6483–6498, 2008
6492 K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005
Figure 6. Sketch of mean diurnal temperature (T) cycle under a) weak anthropogenic
radiative influence, dominant radiative processes are denoted by arrows, b) enhanced
shortwave radiative cooling – “global dimming” (represented by the black arrows) and
long-wave radiative warming (represented by the grey arrows), and c) weakening
shortwave radiative cooling – “global brightening” (thinner black arrows) and continued
long-wave radiative warming.
Fig. 6. As Fig. 5. In addition, sunshine duration series from Sanchez-Lorenzo et al. (2008) (4) and Sanchez-Lorenzo et al. (2007) (5) are
plotted as solid grey line. Plotted data are low-pass filtered values (11-year window 3 year σGaussian low-pass filter) expresses as relative
deviations from the 1961–1990 mean.
(Abakumova et al., 1996) measured at Moscow. Likewise,
the observed increase of surface solar radiation at Moscow
(Wild et al., 2005) is mirrored in an increasing DTR. Both
are potentially caused by the strong decrease of SO2emis-
sions reported from various estimates.
In Western Europe the biggest emitters during 1985 and
1995 are France, (West) Germany, Great Britain and Spain
(Berge et al., 1999). The DTR for all four regions is best
described with a second order polynomial trend, significant
above 95% except for Spain with p-values of 0.35, 1st coef-
ficient) and 0.21 (2nd coefficient) (not shown). For the com-
parison of DTR against SO2emissions and sunshine dura-
tion we used in addition the low-pass filter time-series from
Sanchez-Lorenzo et al. (2007) for Iberia to compare it to our
DTR data of Spain. In Sanchez-Lorenzo et al. (2008) the
same authors provided annual means of sunshine duration for
most of Western Europe, split into six regions. Here we also
used the low pass filtered data of sunshine duration for the
regions NC (north central), CW (central west) and CE (cen-
tral east). We compared NC to Great Britain, CW to France
and CE to West Germany according to their spatial coverage
given in Fig. 1 of Sanchez-Lorenzo et al. (2008).
For Great Britain a reversal in DTR is apparent around
1965 simultaneously to the emissions from Mylona (1996)
of SO2which are peaking in 1965, according to Lefohn et
al. (1996) emissions reach their maximum already around
1960. The annual sunshine duration from Sanchez-Lorenzo
et al. (2008), which covers the central to south-eastern part of
the UK, shows a reversal from decrease to increase in the late
1960s. Subsequently, sunshine duration increases along with
DTR and the decreasing emissions until the present (Fig. 6a).
In the former Federal Republic of Germany, the DTR re-
versal is calculated at 1967 by the 7-year-running mean.
Reversal of SO2emissions is in 1965 according to My-
lona (1996). The most dominant increase of DTR and de-
crease of SO2respectively, however begins during the 1980s
which is in line with the end of the decrease in surface solar
radiation in Germany (Liepert and Kukla, 1997 (Fig. 2) and
a strong increase in sunshine duration (Fig. 6b). Notably the
horizontal visibility increased already since the second half
of the 1960s in most of the Western German stations investi-
gated by Liepert and Kukla (1997). These results point to a
decrease of turbidity and thus a reduction of aerosol burden
of the troposphere.
In France the DTR reversal is calculated at 1980 while SO2
emissions estimated by Mylona (1996) start to decrease from
Atmos. Chem. Phys., 8, 6483–6498, 2008
K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005 6493
1975, Lefohn et al. (1996) in contrast determine the highest
value of emissions not until 1980 (Fig. 6c). The reversal in
shortwave incoming radiation is between 1980 and 1986 ac-
cording to Gilgen et al. (2008). Sunshine duration reverses
between 1980 and 1985. The maximum lag of about one
decade between radiation and SO2emission (form Mylona
1996) reversals can be explained by the method used to de-
termine the year of reversal. Gilgen et al. (2008) used a sec-
ond order polynomial fit to define the period of reversal. The
reversal in the DTR retrieved from the fitted second order
polynomial would be similar, namely around 1980 to 1982
(Fig. 2s).
Spain as the most southern representative of the largest
emitters in Europe has reduced its emissions remarkably
since 1980 (Mylona, 1996). The reversal of DTR derived
from the 7 year-running mean is at 1977 (Fig. 2r and Fig. 4).
According to Sanchez-Lorenzo et al. (2007) the reversal for
sunshine duration for the whole Iberia Peninsula is in 1982
most evident during spring and summer, with mostly clear
sky situations. The period where all three independently in-
vestigated measures (namely emissions, DTR and sunshine
duration) show a reversal in their long-term behavior lies
consequently within 5 years (Fig. 6d).
To summarize on the section with the biggest emitters in
Europe we would like to point to the good qualitative agree-
ment between the low frequency trends in DTR and SO2
emission estimates in six (four in Western, two in Eastern
Europe) of the eight regions analyzed.
The long-term evolution of sunshine duration from
Sanchez-Lorenzo et al. (2007 and 2008) supports our con-
clusions for Western Europe. The biggest disagreement be-
tween DTR and SO2emissions can be found for Eastern Eu-
rope, namely in Russia and the Ukraine. However, trends
in surface solar radiation from Abakumova et al. (1996) for
these regions support our results for long-term DTR devel-
opment. To conclude that though we found good agreement,
more work involving chemistry climate models with an ap-
propriate input and transport of pollutants is required in order
to improve our understanding of the relation between DTR
and air pollution in the future.
4.2 Long range effects on DTR and radiation
According to the previous section a further feature which has
to be discussed is the inconsistency in the DTR reversal com-
pared to the reversal in emissions in a number of regions such
as Finland. The running-mean curve for the DTR in Finland
(Fig. 2c) shows a reversal in the early 1990s, in line with
the surface solar radiation measurements, taken in Sodankyla
in the north of Finland (Ohmura, 2006, Fig. 9). Accord-
ing to Gilgen et al. (2008) 1990 is the year of reversal from
dimming to brightening, for the mean of seven stations in
southern Finland. Emissions, however, peaked around 1975
(Vestreng et al., 2007). It can be seen from the EMEP (Co-
operative program for monitoring and evaluation of the long-
range transmission of air pollutants in Europe) Report 1/06
(Klein and Benedictow, 2006) for Finland that for 2004 about
80% of the oxidized sulphur deposition originates from out-
side Finland. Biggest contributor is Russia with as much as
23% for overall Finland. This implies that the influence on
DTR especially for stations in the North and East of Finland
is likely to be dominated by Russian emissions, thus giving
a possible explanation for the reversal in DTR and surface
solar radiation as late as 1989 (Fig. 4).
Similar to Finland, other countries in Northern Europe,
such as Sweden, Norway, Iceland, Latvia, Lithonia and Den-
mark contribute no more than 10% to their total of oxi-
dized sulphur deposition, leaving these regions as dependent
on neighboring countries such as Great Britain, Germany,
Poland, Estonia, Ukraine and Russia and their patterns in
matters of emissions (Klein and Benedictow, 2006).
4.3 Linear downward trends of DTR
Another interesting feature is the linear downward trend of
the DTR in Sweden, the Baltic States and Ukraine. It is note-
worthy that they seem to build a north-west, south-east ori-
entated zone between Eastern and Western Europe (Fig. 3).
The linear decreasing DTR trend is not explainable by the na-
tional emission trends of the corresponding regions, since the
emissions for all above mentioned countries have declined at
least since 1990. Surface solar radiation for southern Swe-
den and the Baltic States started to increase in the late 1980s
(Ohmura, 2006; Gilgen et al., 2008), subsequently DTR in
both regions levels-off or increases slightly as well. How-
ever, during the 1990s DTR stopped increasing which re-
sulted in a significant decreasing linear trend for the whole
period. The continuous decrease of DTR in Ukraine cannot
be explained by a continued increase of emissions. Also, no
radiation data is available for further interpretation. Support
for the findings on an overall decreasing DTR can be found
from soil moisture measurements. Robock and Li (2006)
have shown that between 1958 until the mid 1990s soil mois-
ture increased significantly for the Ukraine. They state that
precipitation and temperature alone could not have caused
this development. Using a land surface model they show
that a reduction in downward shortwave radiation could have
caused the observed increase in soil moisture, which is in line
with the DTR decrease noted above.
4.4 Early increase in DTR and radiation
The final feature we want to discuss in detail is the early in-
crease of DTR during the 1950s and 1960s, visible in dif-
ferent regions all over Europe but mainly in the northern,
eastern and the periphery regions, namely Norway, Russia,
the Baltic States, FCZS, FRY as well as Iceland, Algeria
and Turkey. The early increase visible from the different
DTR time series might be due to an “earlier brightening”
during this period. The hypothesis of an earlier brightening Atmos. Chem. Phys., 8, 6483–6498, 2008
6494 K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005
in Eastern Europe during the 1950s and 1960s is again sup-
ported by soil moisture measurement. Figure 3 of Robock
and Li (2006) suggests that soil moisture in Russia decreased
slightly between 1958 and 1970, indicating an increase in ra-
No radiation data is available from the above mentioned
regions prior to 1960. Still we can assume a similar techno-
logical development for Eastern Europe as for Western Eu-
rope but with a time shift of one to two decades as indicated
by a later reversal in emissions and radiation during the pe-
riod since 1960.
By investigating radiation and radiation related measure-
ments for Western Europe prior to 1950 we can consequently
find potential explanations for the observed early increase of
the DTR. Evidence for an early brightening period (increase
of incoming shortwave radiation) in Western Europe is pre-
sented in Ohmura (2006). The surface solar radiation data in
Fig. 1 of Ohmura (2006) for Wageningen, Stockholm, Davos
and Potsdam increases until the 1950s. For Wageningen
this is supported from De Bruin et al. (1995). In Sanchez-
Lorenzo et al. (2008) sunshine duration for Western Europe
increases from 1938 (earliest value of plot) until 1950.
5 Conclusions
We investigated annual mean DTR for the period 1950 until
2005 for 23 different countries and regions in and around Eu-
rope as well as Europe as a whole. A total of 16 out of these
23 regions as well as the European mean show a statistically
significant period of decrease and a subsequent increase in
DTR. Two additional regions (BeNeLux, Spain) show an in-
crease, which however is not statistically significant in the
multiple regression analysis. Of the remaining five regions,
two (East Germany, Portugal) show no specific trend and
three (Sweden, Baltic States, Ukraine) regions show a con-
tinuation of the decreasing trend. The trend analysis is lim-
ited by the lack of a standard homogeneity procedure and by
the limited number of available measurement sites and their
spatial distribution.
The connection between DTR, shortwave radiation and
SO2emissions has been qualitatively discussed with respect
to a common trend reversal. The period of reversal of DTR
from decrease to increase is in most cases in line with social
and economic development as indicated by SO2-emissions or
deposition, respectively. All reversals of DTR were shown
to take place between 1965 and 1990. This is consistent
with the change from decrease to increase of incoming short-
wave radiation (“Global Dimming” to “Global Brighten-
ing”). Consequently, we conclude that the long-term trends
in DTR are strongly affected by changes in incoming short-
wave radiation, presumably largely influenced by direct and
indirect effects of aerosol from sulphurous emissions.
This may suggest that in more regions around the globe
DTR will increase if the surface solar radiation continues to
increase on a widespread basis.
Appendix A
A1 Illustrative example how to read Table 1
The example of Denmark, (Table 1, line 5) reads as follows:
the first column contains the name of the region. The second
column contains the R2between the time series and the best
fitted trend of the form:
f (x) =f1x+f o (A1)
Following the R2a small “o” indicates that the linear coef-
ficient is statistically significant above the 90% level or in
more common words: it is 90% likely that the linear coeffi-
cient cannot be zero if the time series should be represented
by the given equation. Column three contains again the value
for the R2. However, now the comparison is performed be-
tween the time series of annual mean DTR of Denmark and
the best fit of the type:
f (x) =f2x2+f1x+f o (A2)
Following this R2two lines of coding symbols contain the
information that the linear coefficient (f1)is now 99% sig-
nificant (two “x”) and the quadratic trend is different from
zero at the 95% significance level (one “x”). For the third or-
der polynomial, shown in the fourth column, the R2increases
again to now 0.3. The three lines of symbols following the
R2indicate that the cubic coefficient is now significant at the
99% level, the quadratic at the 95% level but the linear co-
efficient misses the 90% level and is marked consequently
with a small “–”. In the 5th column the R2increases to 0.33
thus explaining already 33% of the given annual mean time
series. However the polynomial of the form,
f (x) =f4x4+f3x3+f2x2+f1x+f o (A3)
overestimates for the given time period.
A2 Explanatory example Fig. 4
The method underlying Fig. 4 can be illustrated comparing
Figs. 2f (Denmark) and 2o. The highest value for the seven
year running mean during the given period for FRY appears
in 1991 with 9.8C, the lowest is 8.98in 1977. The absolute
difference is 0.82; 10% of 0.82is 0.082. Consequently all
years with a seven year running mean value of the time series
of FRY within the range of 8.98and 9.06have been marked
with a dash in Fig. 4, line 6 (1975, 1976, 1978). These dashes
consequently give a sort of error bar for the calculated year
of reversal. For the reversal in the annual mean time series of
Denmark, a much bigger uncertainty range is given, namely
between 1981 and 1987. The highest value in the period 1965
Atmos. Chem. Phys., 8, 6483–6498, 2008
K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005 6495
to 1995 of the seven year running mean of the annual means
from Denmark is 5.75(1970) the lowest is 5.21(1981). So
the difference between the two extremes is 0.54which is
only two thirds of FRY difference. This fact gives credit to
the different overall variability of the investigated time series.
After adding 10% of 0.54to the minimum of 5.21all years
within the range of 5.21to 5.26(1982–1987) are marked
with a dash (Fig. 4, line 14).
Appendix B
Addititonal, detailed information on the
regional annual means
B1 Western Europe
Norway. The mean DTR, predominantly governed by
stations around 60N, shows an increase during the 1950s
followed by a significant decrease until the late 1980s.
Starting in 1987 DTR increases, but is then interrupted by a
dip around 2000 (Fig. 2a). This dip reduces the significance
of the fitted polynomial, still the third and forth order
polynomials are significant above 90%.
Sweden. The averaged time series for Sweden shows
a highly significant negative linear trend (Fig. 2b). The
selected stations are all located south of 64N, representing
southern Sweden (Fig. 3). The DTR appears to level off
since the late 1980s. However, when reducing the Swedish
data to cover only stations for the period until 2005, a
tendency to an increase became apparent, this trend was
not significant in any model. Also the selection would have
given even more weight to the most southern part of Sweden.
Finland. The data for Finland consists of three stations,
evenly divided from north to south, namely Helsinki,
Jyvaskyla and Sodankyla. The national trend is best repre-
sented by a second order polynomial trend significant above
the 99% level (Fig. 2c).
Denmark. Though one of the smaller countries, Denmark
contributes 5 equally distributed stations to the dataset
(Fig. 3). The best fitting trend model is the third order
polynomial (Fig. 2f). The second and third order coefficients
are significant at 95% level, whereas the linear term shows
only p-value of 0.18 corresponding to approximately 80%
confidence level.
Great Britain. Only three stations met the demanded
quality requirements of temporal coverage up to 2003,
namely Oxford, Wick and Waddington. The former two are
located in the industrialized southern area of the UK and
show a distinct DTR reversal from decrease to increase.
Wick is situated at the northern tip of the British mainland
showing a general decrease. Despite this the fitted second
order polynomial is significant at the 95% level, indicating a
trend from decrease to increase (Fig. 2e). An early reversal
around 1965 is visible from the 7-year running-mean.
BeNeLux. Belgium and Luxembourg each contribute only
one station to the selected dataset, hence they were analyzed
together with the seven stations from the Netherlands. The
analysis of the BeNeLux region showed no significant trend.
The best fit however is a second order polynomial with
p-values around 0.23 (Fig. 2m). The seven year running
mean trend shows an overall increase since 1980.
East Germany. No significant trend is apparent. Best
fit is the second order polynomial (Fig. 2j). P-values are
in general above 0.7 (confidence level, below 30%) in all
models and coefficients.
West Germany. For the mean of the 13 stations a distinct
reversal from decrease to increase is visible in the national
mean time series. Consequently the second order polyno-
mial trend is significant at the 95% level in both coefficients
(Fig. 2i).
France. The 25 selected stations are distributed equally
over France (Fig. 3). Similar to West Germany the second
order polynomial is significant at the 95% level emphasizing
the DTR development form decrease to increase with the
reversal period between 1965 and 1985.
Alpine Region. There are only two stations, one from
Austria and one from Switzerland. Most Swiss stations had
to be rejected due to homogeneity issues. Problems were
caused by change of location and instrumentation. The only
Swiss station that met the quality requirements is Basel-
Binningen. For Austria only one station (Kremsmuenster)
with complete data coverage from 1950 to 2005 is provided
in ECA&D-P. The mean trend derived from the two stations
is best described by a polynomial of the second order
(Fig. 2n). The main contribution to this shape is given by
the Basel-Binningen station which shows a distinct decrease
and increase.
Italy. The mean trend for Italy is calculated from four sta-
tions. The best fitting polynomial is second order (Fig. 2t).
Overall a strong decrease and subsequent increase is visible.
Spain. For Spain a slight decrease in the seven year running
mean up to 1977 is visible. Thereafter an equally slightly
visible increase in DTR can be seen (Fig. 2r). However, the
statistical analysis shows no significant trend on the 90%
confidence level. The p-values for Spain are, 0.36 for the
linear and 0.22 for the cubic coefficient. Atmos. Chem. Phys., 8, 6483–6498, 2008
6496 K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005
Portugal. A total of three stations are sufficient according
to the demanded quality requirements .Braganca shows an
overall increase for the whole period while Lisboa (Lis-
bon) and Porto show a continuous decrease in DTR (Fig. 2q).
B2 Eastern Europe
Former Republic of Yugoslavia. The reliable period for
the FRY region is from 1956 to 2004. The best fitting trend
model for that time series is a fourth order polynomial trend
with p-values below 0.05 for all coefficients. Consequently
the development shows more than a single period of decrease
and increase. From 1956 to about 1965 the DTR increases
this is followed by a distinct decrease up to around 1980.
From 1980 until 1990 a second and more emphasized
increase is dominant with a subsequent phase of more or
less constant development until 2004 (Fig. 2o). However,
the most pronounced feature in this period is the decrease
and then subsequent increase in DTR from 1965 to 1991.
Romania. The best fit is a third order polynomial with
p-values of about 0.03 for the first and second coefficient,
the p-value for the third coefficient is slightly higher with
0.051 and therefore misses the 95% confidence boundary.
From the seven year running mean a period with a distinct
decrease from 1961 to 1971 is visible, followed by a longer
period of increasing DTR lasting until 1990, subsequently
the running mean shows a constant development (Fig. 2p).
Czechoslovakia. As for the area of the FRY, the former
Czechoslovakian states are best fitted by a fourth order
polynomial (Fig. 2k). All tested coefficient of the fourth
order polynomial are above the 95% significance level
(p-values <0.05). The decreasing period lasts until 1977
according to the seven year running mean, then the DTR
increases until it stops around 1992. This is followed by a
stable to slightly decreasing period until 2004.
Poland. Only two stations with data from 1966 to 2005 are
available, Leba and Siedlce these both show very similar
long-term trends. The best fit is a second order polynomial.
p-values for the coefficients are 0.083 and 0.046. For Poland
a decreasing period is visible from 1966 to 1980 and an
increasing period from 1986 to 2005 (Fig. 2g).
Baltic Region. A strong increase is visible in the seven year
running mean up to 1966, followed by a decrease, leveling
off in 1991. A short increase starting in 1990 come to an end
by 1996 and then becomes a continued decrease (Fig. 2h).
The result of this is an overall linear decrease in the fitted
trend model significant at 95% level.
Ukraine. The nearly monotonic drop of the Ukrainian
mean DTR lasts over the whole period from 1951 to 2005
(Fig. 2l). The linear trend is significant above 99%. The
two most westerly located stations, L’Vov (Lwiw/Lemberg)
and Uzhgorod show a dominant increase since the middle of
the 1970s. For the two biggest cities of Ukraine, Khrakov
and Kyiv (Kiev) a decrease in DTR until the mid-1990s is
dominant follow by a leveling off or increase thereafter.
Russia. The largest region of the so called Eastern-European
section is the European part of Russia with Brest (Brestzon-
alnaya) as only representative station for Belarus included.
The mean DTR development for the overall 36 stations is
best described by a third order polynomial. p-values are
around 0.001 the R2is 0.22. Assuming that none of the
high frequency is caught by the polynomial this is a quite
high value. The seven year running mean describes an in-
crease until 1966 followed by a continuous decrease until
1992 and thereafter an equally uninterrupted increase until
2003 (Fig. 2d).
B3 Surrounding regions
Iceland. The best fit for the DTR time series is the third
order polynomial (Fig. 2u). All coefficients are above
95% significant. Equal to Denmark and Finland, Iceland
is considered to be a mixture of the Western and Eastern
European trend type.
Turkey. The shape of the mean data series of the three
stations is best described by a third order polynomial. The
seven year running mean describes a distinct increase from
1950 until 1963, then a subsequent decrease is disturbed by
a short period of increase between 1974 and 1984, thereafter
the long-term decrease is continued until 1990. Finally
an increase until 2004 is visible from the smoothed 7 year
running-mean curve. The described interruption causes a
reduction in the significance of the trend model, p-values are
0.150 (1st), 0.053 (2nd) and 0.027 (3rd). When smoothing
the described period the p-values are: 0.03 (2nd) and 0.009
(3rd). The linear coefficient never becomes statistically
significant since there is no overall decrease or increase in
the series.
Algeria. Three stations are available which are distributed
roughly evenly along a north south transect (Fig. 3). All sta-
tions, namely Alger-Dar el Beida, El Golea and Tamanras-
set, present a similar trend best described with a third order
polynomial. The significance of coefficient is above the 99%
level. The seven year running mean is dominated by an in-
crease from 1950 to 1963, followed by a decrease lasting
until 1986. Finally, an increase can be noted up to 2004. The
peek in 2001 is a prominent feature of the mean and can be
equally found in each of the contributing stations.
Atmos. Chem. Phys., 8, 6483–6498, 2008
K. Makowski et al.: Diurnal temperature range over Europe between 1950 and 2005 6497
Acknowledgements. We would like to thank Royal Netherlands
Meteorological Institute for access to the ECAD-P data set and
the meteorological services of Romania (Sorin Cheval), Nor-
way (Elin Lundstad, Eirik Forland, Knut A. Iden) and Iceland
(Trausti Jonsson) for providing additional data. Discussions with
Thomas Peter, J¨
org M¨
ader and Andreas Roesch were highly
appreciated. Paul Southern’s proofreading is very gratefully
acknowledged. The work was funded by ETH Zurich, Polyproject:
“Variability of the sun and global climate” – Phase II. MW and AO
acknowledge NCCR Climate funded by the Swiss National Science
Edited by: J. Quaas
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... (ii) It decreased on a global scale from the 1950s onwards, at the time when the mean Global temperature started to increase markedly (Global Warming). DTR has in it therefore a number of (oen dependent) climate parameters and these could be, in principle, CR dependent (see [8] for details of DTR for Europe for the range 1950-2005). ...
... (i) e source of the DTR change itself is claimed to be "changes in (terrestrial) emissions and the associated changes in incoming solar radiation" [8]. us, changes in the solar irradiance are preferred. ...
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Following on previous work by others, which gave evidence for few days’ changes in the European Diurnal Temperature Range (DTR) apparently correlated with Cosmic Ray Forbush Decreases, we have made an independent study. We find no positive evidence. An analysis has also been made of the Fourier components of the time series of the DTR value (taken as deviations from a ±10 day running mean). Evidence for a number of interesting periods is found, including one at about 27 days, albeit with a variability with time. The same period of solar irradiance (particularly in the UV) is favoured as the explanation.
... Owing to this, the diurnal temperature range (DTR) which is a derived variable representing the difference between daytime maximum temperature and night-time minimum temperature is preferred to mean temperature as an indicator of climate change in a region (Karl et al., 1991;Braganza et al., 2004) and has been used in climatic extremes researches. Also, DTR is used to investigate the counteracting effects of long wave and shortwave radiative forcing, because the diurnal minimum and maximum temperature is closely related to the long wave and short wave radiative flux (Makowski, Wild and Ohmura, 2008). ...
Diurnal temperature range (DTR) is an important derived variable used in detecting signature of observed climate changes. Understanding its changes in recent time is important for managing and coping with climate change induced risks. This study analysed the long term trend and abrupt changes in diurnal temperature range over Nigeria from 1960 to 2019. Descriptive statistics, Mann-Kendall trend test, Sen’s slope and Pettit’s tests were used to assess the characteristics, trend, abrupt change and significance in annual DTR time series. Pearson correlation was used to examine the spatial relationship between DTR and minimum temperature, maximum temperature, precipitation and cloud cover. Results showed that mean DTR amount varied across spatio-temporal scales with steady increase from the coastal region, coupled with a weak inter-annual variability (CV < 3%). The trend analysis showed a significant decreasing DTR in most grid points (GP) and regions of Nigeria, with the exception of Enugu, Ado-Ekiti and Warri. Also a significant negative trend was observed at the Guinea, Sudan and Sahel savanna regions. Abrupt changes occurred in the 1970s in the entire regions and most of the GPs with Ado-Ekiti, Calabar, and Enugu occurred in 1991 while Maiduguri and Jos experienced such changes in 2011. Furthermore, significant abrupt changes were observed at the following GPs and regions; Ikeja, Kaduna, Kano, Katsina, Sokoto, Yelwa, Yola, Guinea, Sudan and Sahel Savannas. This decrease in DTR over most of the GP and the entire region indicate that the climate of Nigeria is becoming warmer possibly due to environmental changes with precipitation and cloud cover being the major drivers of DTR variability in Nigeria. Thus, proper climate actions should be taken through adaptation and resilient planning for the sustainable development of socio-economic and natural systems.
... Symptom recovery; early manifestations of dark green islands (DGIs), which indicate islands of un-infected leaf areas surrounded by systemic infections; or initiation of systemic infections in resistant plants exhibiting a hypersensitive response, were several reported contradictory manifestations that could be associated with the fluctuating surrounding conditions [19][20][21]. Importantly, the statistically significant higher diurnal temperature range (DTR), measured since the 1990s [22], exposes field grown crops to short-time temperature waves. We have recently shown that new early manifestations of CGMMV disease occurred in cucumbers following a recovery stage induced by an abrupt temperature raise from 25 °C to 32 °C. ...
Conference Paper
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Greenhouse‐grown cucumber plants inspected during and following extreme variations in environmental temperatures showed new characteristics of cucumber green mottle mosaic virus (CGMMV) disease manifestations. An increasing occurrence of CGMMV disease recovery has been associated with a new phenotype identified at early stages of a reemerging disease. Symptoms of bright yellow islands (BYIs), conspicuous amid a dark green surrounding tissue (DGS), were detected in up to 10% of symptomatic plants in net‐houses showing 50–60% recovery following an extreme temperature wave. Importantly, similar CGMMV disease initiation stages were observed in infected cucumber plants exposed to low temperatures of ~16 °C, under conditions of both controlled growth chambers and a net‐house exposed to environmental temperature fluctuations. Apparently, a wide range of fluctuating temperatures evoked gradual manifestations of a reemerging disease.
... Among temperature, humidity, and wind speed, temperature had the most obvious long-term relationship with pollutants in the corresponding study area [9]. The factors that affect the diurnal temperature range are complex, and some studies have noted that there is reasonable agreement between the trend of SO 2 emissions and the diurnal temperature range in highly polluted areas [28]. On a sunny day, the temperature varies greatly, and the vertical air convection is strong, which can make the inversion layer quickly disappear, which is conducive to the diffusion of pollutants [29]. ...
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Sulfur dioxide (SO2) is a serious air pollutant emitted from different sources in many developing regions worldwide, where the contribution of different potential influencing factors remains unclear. Using Shandong, a typical industrial province in China as an example, we studied the spatial distribution of SO2 and used geographical detectors to explore its influencing factors. Based on the daily average concentration in Shandong Province from 2014 to 2019, we explored the influence of the diurnal temperature range, secondary production, precipitation, wind speed, soot emission, sunshine duration, and urbanization rate on the SO2 concentration. The results showed that the diurnal temperature range had the largest impact on SO2, with q values of 0.69, followed by secondary production (0.51), precipitation (0.46), and wind speed (0.42). There was no significant difference in the SO2 distribution between pairs of sunshine durations, soot emissions, and urbanization rates. The meteorological factors of precipitation, wind speed, and diurnal temperature range were sensitive to seasonal changes. There were nonlinear enhancement relationships among those meteorological factors to the SO2 pollution. There were obvious geographical differences in the human activity factors of soot emissions, secondary production, and urbanization rates. The amount of SO2 emissions should be adjusted in different seasons considering the varied effect of meteorological factors.
... Aerosols have a large influence on DTR. A study [Makowski et al., 2008, "Diurnal temperature range over Europe between 1950 In monsoon season (June-September) rainfall is increasing in Haryana (+1.0 to +6.0 mm/year) and decreasing in Punjab (-0.01 to -2.0 mm/year). In winter season mixed trends have been observed in all the stations under study. ...
... The RF linking model proposed by Zhao et al. [58] and Zhao et al. [26] is based on the assumption that incident solar radiation dominates the morning warming process and this factor can accurately represent the close relationship between the daily LST and surface solar radiation [26,58,80,81]. In this study, for daytime MODIS Aqua-Terra LST's reconstruction, the incident solar radiation was also taken into account and was estimated by cumulating the CLDAS shortwave radiation data on surface warming process from sunrise time to satellite sunrise time. ...
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Generating spatiotemporally continuous land surface temperature (LST) data is in great demand for hydrology, meteorology, ecology, environmental studies, etc. However, the thermal infrared (TIR)-based LST measurements are prone to cloud contamination with missing pixels. To repair the missing pixels, a new XGBoost-based linking approach for reconstructing daytime and nighttime Moderate Resolution Imaging Spectroradiometer (MODIS) LST measurements was introduced. The instantaneous solar radiation and two soil-related predictors from China Data Assimilation System (CLDAS) 0.0625°/1-h data were selected as the linking variables to depict the relationship with instantaneous MODIS LST data. Other land surface properties, including two vegetation indices, the water index, the surface albedo, and topographic parameters, were also used as the predictor variables. The XGBoost method was used to fit an LST linking model by the training datasets from clear-sky pixels and was then applied to the MODIS Aqua-Terra LSTs during summer time (June to August) in 2017 and 2018 across China. The recovered LST data was further rectified with the Savitzky–Golay (SG) filtering method. The results showed the distribution of the reconstructed LSTs present a reasonable pattern for different land-cover types and topography. The evaluation results using in situ longwave radiation measurements showed the RMSE varies from 3.91 K to 5.53 K for the cloud-free pixels and from 4.42 K to 4.97 K for the cloud-covered pixels. In addition, the reconstructed LST products correlated well with CLDAS LST data with similar LST spatial patterns. The variable importance analysis revealed that the two soil-related predictors and the elevation variable are key parameters due to their great contribution to the XGBoost model performance.
... In addition, recent studies of cucurbit transcriptome and microRNA profiles induced by CGMMV infections [29][30][31][32] as well as profiles of vsiRNAs, regulating plant gene expressions 33,34 , have emphasized the necessity of a precise description of the early stages of CGMMV disease establishment. A comprehensive study of annual DTRs in various countries over the past several decades has shown a trend toward an increasing temperature range, documenting statistically significant higher annual DTRs in Europe since the 1990s 11 . The impact of cucumber plant exposure to extreme temperatures, daily, on CGMMV disease symptom initiation and progression, was the subject of our current study. ...
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Studies of early stages of cucumber green mottle mosaic virus (CGMMV) disease have been recently focused on plant molecular responses. However, extreme diurnal environmental temperatures, characteristic of global climate changes, could affect plant susceptibility and disease phenotype progression. Our studies of CGMMV disease progression, under simulated extreme temperature waves, have revealed two new disease initiation phenotypes that developed gradually, preceding severe symptom manifestations of post-recovery CGMMV systemic infections. 'Early post-recovery stage' bright yellow islands (BYIs) with defined boundaries amid asymptomatic leaf blades were first emerging followed by 'late post-recovery stage' BYIs with diffused boundaries. A deduced CGMMV disease progression scheme, postulating BYI symptom occurrence time-windows, revealed BYIs in field grown cucumber plants exposed to extreme diurnal temperatures. Profiling ontology of cucumber differentially expressed genes in BYIs vs the associated dark-green surrounding tissues disclosed activation of jasmonic acid (JA) pathway in 'early post-recovery stage' BYIs. JA signaling was inactivated in 'late post-recovery stage' BYIs concomitant with increasing expressions of JA signaling inhibitors and downregulation of JA responsive phenylpropanoid pathway. Our results disclosed a new phenotypic description of CGMMV disease initiation, characteristic of cucumbers grown under extreme environmental temperature fluctuations. The BYI phenotypes could define a time-window for CGMMV disease management applications.
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Snow cover affects many natural processes, including determining and regulating the water balance, determining spring runoff. The aridity of the climate in the southern Rostov region causes water scarcity in the region. The purpose of this work is to study the variability of snow cover in the settlement Gigant for the period from 1961 to 2019. The main task is to determine the changes in the dynamics of snow cover, analyze the number of days with snow and the average snow height for the study period. The analysis included the height of the snow cover, the number of days with snow, and the average annual temperatures. The data of route snow-measuring surveys were statistically analyzed. A decrease in the number of days with snow was revealed, which is explained by frequent thaws and instability of negative temperatures. There is a tendency to decrease the snow cover in winter and an increase in the number of thaws.
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Background Increased mortality risk is associated with short-term temperature variability. However, to our knowledge, there has been no comprehensive assessment of the temperature variability-related mortality burden worldwide. In this study, using data from the MCC Collaborative Research Network, we first explored the association between temperature variability and mortality across 43 countries or regions. Then, to provide a more comprehensive picture of the global burden of mortality associated with temperature variability, global gridded temperature data with a resolution of 0·5° × 0·5° were used to assess the temperature variability-related mortality burden at the global, regional, and national levels. Furthermore, temporal trends in temperature variability-related mortality burden were also explored from 2000–19. Methods In this modelling study, we applied a three-stage meta-analytical approach to assess the global temperature variability-related mortality burden at a spatial resolution of 0·5° × 0·5° from 2000–19. Temperature variability was calculated as the SD of the average of the same and previous days’ minimum and maximum temperatures. We first obtained location-specific temperature variability related-mortality associations based on a daily time series of 750 locations from the Multi-country Multi-city Collaborative Research Network. We subsequently constructed a multivariable meta-regression model with five predictors to estimate grid-specific temperature variability related-mortality associations across the globe. Finally, percentage excess in mortality and excess mortality rate were calculated to quantify the temperature variability-related mortality burden and to further explore its temporal trend over two decades. Findings An increasing trend in temperature variability was identified at the global level from 2000 to 2019. Globally, 1 753 392 deaths (95% CI 1 159 901–2 357 718) were associated with temperature variability per year, accounting for 3·4% (2·2–4·6) of all deaths. Most of Asia, Australia, and New Zealand were observed to have a higher percentage excess in mortality than the global mean. Globally, the percentage excess in mortality increased by about 4·6% (3·7–5·3) per decade. The largest increase occurred in Australia and New Zealand (7·3%, 95% CI 4·3–10·4), followed by Europe (4·4%, 2·2–5·6) and Africa (3·3, 1·9–4·6). Interpretation Globally, a substantial mortality burden was associated with temperature variability, showing geographical heterogeneity and a slightly increasing temporal trend. Our findings could assist in raising public awareness and improving the understanding of the health impacts of temperature variability. Funding Australian Research Council, Australian National Health & Medical Research Council.
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The signal of temperature change has emerged from background variations over most tropical regions in boreal summer over decadal-centennial timescales, but not in northern-central India (NCI). In this study, we investigated the reason for the limited temperature changes in NCI. We found that internal variability, largely caused by the Interdecadal Pacific Oscillation (IPO) on a ~20-year timescale, has the potential to mask the temperature change signal. Besides, local response to external forcing, linked to non-greenhouse gas (GHG) forcings, strongly overrides GHG warming in NCI, which results in little trend in the temporal evolution of external variability. The internal variability related to IPO and the limited warming arising from the competition between multiple forcings result in the smallest signal-to-noise ratio, and thus the temperature change signal fails to emerge from the background variations.
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Monthly mean maximum and minimum temperatures for over 50% (10%) of the Northern (Southern) Hemisphere landmass, accounting for 37% of the global landmass, indicate that the rise of the minimum temperature has occurred at a rate three times that of the maximum temperature during the period 1951-90 (0.84°C versus 0.28°C). The decrease of the diumal temperature range is approximately equal to the increase of mean temperature. The asymmetry is detectable in all seasons and in most of the regions studied.
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Changes in the global water cycle can cause major environmental and socioeconomic impacts. As the average global temperature increases, it is generally expected that the air will become drier and that evaporation from terrestrial water bodies will increase. Paradoxically, terrestrial observations over the past 50 years show the reverse. Here, we show that the decrease in evaporation is consistent with what one would expect from the observed large and widespread decreases in sunlight resulting from increasing cloud coverage and aerosol concentration.
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From the 1950s to the 1980s, a significant decrease of surface solar radiation has been observed at different locations throughout the world. Here we show that this phenomenon, widely termed global dimming, is dominated by the large urban sites. The global-scale analysis of year-to-year variations of solar radiation fluxes shows a decline of 0.41 W/m2/yr for highly populated sites compared to only 0.16 W/m2/yr for sparsely populated sites (<0.1 million). Since most of the globe has sparse population, this suggests that solar dimming is of local or regional nature. The dimming is sharpest for the sites at 10°N to 40°N with great industrial activity. In the equatorial regions even the opposite trend to dimming is observed for sparsely populated sites.
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Decadal changes in shortwave irradiance at the Earth's surface are estimated for the period from approximately 1960 through to 2000 from pyranometer records stored in the Global Energy Balance Archive. For this observational period, estimates could be calculated for a total of 140 cells of the International Satellite Cloud Climatology Project grid (an equal area 2.5° × 2.5° grid at the equator) using regression models allowing for station effects. In large regions worldwide, shortwave irradiance decreases in the first half of the observational period, recovers from the decrease in the 1980s, and thereafter increases, in line with previous reports. Years of trend reversals are determined for the grid cells which are best described with a second-order polynomial model. This reversal of the trend is observed in the majority of the grid cells in the interior of Europe and in Japan. In China, shortwave irradiance recovers during the 1990s in the majority of the grid cells in the southeast and northeast from the decrease observed in the period from 1960 through to 1990. A reversal of the trend in the 1980s or early 1990s is also observed for two grid cells in North America, and for the grid cells containing the Kuala Lumpur (Malaysia), Singapore, Casablanca (Morocco), Valparaiso (Chile) sites, and, noticeably, the remote South Pole and American Samoa sites. Negative trends persist, i.e., shortwave radiation decreases, for the observational period 1960 through to 2000 at the European coasts, in central and northwest China, and for three grid cells in India and two in Africa.
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Changes in sunshine duration (SS) measured in the conterminous United States during the past century were used as a proxy to explore changes in shortwave forcing at the earth’s surface when and where accurate measurements of global irradiance (Eg) were not available. Yearly totals of SS from the 106 Weather Bureau stations with 70 or more years of complete measurements between 1891 and 1987 were analyzed after establishing that the two changes in instrumentation during that period had not significantly influenced the measurements. Annual totals of SS were highly correlated (r2 = 0.86) with annual totals of global irradiance (Eg↓) measured at the 26 U.S. pyranometer stations during the 1977–80 period when the Solar Radiation Network (SOLRAD) was operating at its maximum accuracy. The linear relationship between annual totals of Eg↓ and SS was highly significant (P < 0.001), with each additional hour of sunshine duration equivalent to an increase of 0.0469 ± 0.002 W m−2 (or 1.48 ± 0.07 MJ m−2 solar radiation per year). The error term of annual values of Eg↓ estimated from SS was 5%. Almost half of the sunshine series showed significant linear time trends in SS. At 27 sites it increased significantly with time; at 21 sites it significantly decreased. Regionally, in the northwest quarter of the U.S. landmass (>36°N, >98°W), SS increased at nine sites and decreased at three; in the three other quarters of the United States, the numbers of sites with increasing and decreasing trends were equal. After 1950, a larger proportion of series showed decreases in sunshine duration, and more sites showing decreasing SS were found in the Northeast and in the West and South of the United States, but these regional differences were not significant. Normalized annual anomalies of SS averaged for all of the U.S. series showed no significant linear time trend during the last century, but the running 11-yr average values indicated clear peaks in the fourth and sixth decades of the last century and troughs in the first, fifth, and seventh decades; the peaks coincided with those reported for continental air temperature, and the troughs coincided with those for continental rainfall. A significant periodic component (with a median period of 10 yr) was found in half of the SS series; however the peak spectral density averaged for the United States, occurring at a period of 11.25 yr, was not significantly above that expected for the white noise level. An analysis of long-term records from outside the United States showed that the sensitivity of SS to Eg↓ was dependent on both astronomical and climatic factors, and the implications of this site dependence on the accuracy of this proxy relationship is discussed. A decline in SS followed major volcanic eruptions in North America. In the case of El Chichon, this change was calculated to have resulted in a negative shortwave radiative forcing of 6.4 W m−2 for the United States, some 3 times greater than the value calculated from the direct effect of the increase in aerosol loading. It is concluded that the U.S. sunshine duration database shows little evidence for a significant trend in solar forcing at the earth’s surface during the twentieth century. To reconcile this discrepancy with reports of decreases in Eg↓ measured in the United States during the last half century requires a more detailed understanding of the influence of clouds and aerosols on sunshine duration.
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This work analyzes sunshine duration variability in the western part of Europe (WEU) over the 1938-2004 period. A principal component analysis is applied to cluster the original series from 79 sites into 6 regions, and then annual and seasonal mean series are constructed on regional and also for the whole WEU scales. Over the entire period studied here, the linear trend of annual sunshine duration is found to be nonsignificant. However, annual sunshine duration shows an overall decrease since the 1950s until the early 1980s, followed by a subsequent recovery during the last two decades. This behavior is in good agreement with the dimming and brightening phenomena described in previous literature. From the seasonal analysis, the most remarkable result is the similarity between spring and annual series, although the spring series has a negative trend; and the clear significant increase found for the whole WEU winter series, being especially large since the 1970s. The behavior of the major synoptic patterns for two seasons is investigated, resulting in some indications that sunshine duration evolution may be partially explained by changes in the frequency of some of them.
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We examine multidecadal changes in surface downward shortwave (SW) radiation flux, total cloud cover, SW cloud effect, and related parameters over Europe during 1965-2004 using monthly gridded data from the Global Energy Balance Archive (GEBA), synoptic cloud reports, and the International Satellite Cloud Climatology Project (ISCCP). One key issue is distinguishing the effects of natural cloud variability from long-term anthropogenic aerosol influences on surface SW flux. Accordingly, we introduce the concept of cloud cover radiative effect (CCRE), defined as the change in downward SW flux produced by a change in cloud cover. The correlation between pan-European time series of CCRE anomalies and GEBA solar radiation anomalies is 0.88, indicating that cloud cover variability and associated changes in cloud albedo dominate SW radiation variability on monthly to decadal timescales. After these weather-related cloud effects are removed by subtracting CCRE anomalies from GEBA solar radiation anomalies via linear regression, a distinct decreasing trend followed by a distinct increasing trend remain in the residual time series. Depending on the method of trend calculation, pan-European residual flux declined by a statistically significant 2.7-3.5 W m-2 per decade during 1971-1986 and rose by a statistically significant 2.0-2.3 W m-2 per decade during 1987-2002. The fact that independent grid boxes exhibit mostly negative trends in the earlier period and mostly positive trends in the later period demonstrates that these long-term variations in SW flux are real and widespread over Europe. Changes in cloud cover cannot account for the trends in surface SW flux since cloud cover actually slightly decreased during 1971-1986 and slightly increased during 1987-2002. The most likely explanation is changes in anthropogenic aerosol emissions that led to more scattering and absorption of SW radiation during the earlier period of solar ``dimming'' and less scattering and absorption during the later period of solar ``brightening.''
A historical emission inventory for sulphur dioxide has been compiled for Europe covering the period 1880–1991. The estimated emissions have been used as input to the sulphur module of the EMEP/MSC-W acid deposition model. The aim was to show the way and the extent to which the historical development of anthropogenic sulphur dioxide emissions alone has affected the concentration and deposition fields of oxidised sulphur in Europe. Although acknowledged, effects exerted by the meteorological variability and the changing oxidising capacity of the atmosphere over the years have not been taken into consideration. Long-term emission estimates reveal that combustion of coal was the dominant emission source before World War II in all countries and combustion of liquid fuels thereafter in most. Releases from industrial processes were relatively small. National sulphur dioxide emissions peaked mainly in the 1960s and 1970s, whilst emission control measures resulted in gradual reductions in most countries in the 1980s. In Europe as a whole, coal combustion remained the major emission source throughout the century. Total anthropogenic releases increased by a factor of 10 between the 1880 s and 1970s when they peaked at approximately 55 million tonnes of sulphur dioxide, followed by a 30% decline in the 1980s. Uncertainties in national emission estimates due to uncertain sulphur contents in fossil fuels are within ± 30% for 22 out of 28 countries and ± 45% for the rest. The location of emission sources in Europe has shown over the years a progressive detachment from the coalfields towards a widespread distribution, accompanied in the last decades by considerable emission reductions over north-western and parts of central Europe and substantial increases in the south and south-east. Modelled air concentrations and depositions reflect to a great extent the emission pattern, revealing two- to six-fold increases between the 1880 s and 1970s. Maximum sulphur loadings are confined over parts of north-western and central Europe. Accumulated depositions over the period 1880–1991 in these areas reach 600 g (S) m −2 . Emissions are principally in the form of sulphur dioxide, so that comparable concentrations of particulate sulphate in low emission regions indicate the importance of long range transport. Assuming a constant ecosystem sensitivity throughout the period, depositions sufficient to cause ecosystem damage may have occurred before 1880 in many areas of north-western and central Europe. Nevertheless, in large parts of eastern and southern Europe depositions are still below these critical loads. DOI: 10.1034/j.1600-0889.1996.t01-2-00005.x
[1] The diurnal range in surface temperatures (DTR = maximum − minimum temperature) has been widely used as one indicator of potential climate change. On hemispheric space scales DTR trends over about the last half-century tend to be decreasing. This paper analyzes regional scale trends in DTR for Mexico (1940–2001). Our principal finding is that in recent decades (post-1970) DTR trends over Mexico are positive as maximum temperatures are warming at a significantly higher rate than minimum temperatures. Regional land use and land cover changes (LCCs) are identified as potential forcing mechanisms responsible for at least part of the observed DTR behavior.
Global average trends in solar radiation reaching the Earth's surface show a transition from dimming to brightening that occurred in about 1990. We show that the inter-annual trend in solar radiation between 1980 and 2000 mirrors the trend in primary emissions of SO2 and black carbon, which together contribute about one-third of global average aerosol optical depth. Combined global emissions of these two species peaked in 1988–1989. The two-decadal rate of decline in aerosol loading resulting from these emission changes, 0.13% yr−1, can be compared with the reported increase in solar radiation of 0.10% yr−1 in 1983–2001. Regional patterns of aerosol and radiation changes are also qualitatively consistent. We conclude that changes in the aerosol burden due to changing patterns of anthropogenic emissions are likely contributing to the trends in surface solar radiation.