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Heat waves have discernible impacts on mortality and morbidity, infrastructure, agricultural resources, the retail industry, ecosystem and tourism and consequently affect human societies. A new definition of socially relevant heat waves is presented and applied to new data sets of high-quality homogenized daily maximum and minimum summer air temperature series from 246 stations in the eastern Mediterranean region (including Albania, Bosnia-Herzegovina, Bulgaria, Croatia, Cyprus, Greece, Israel, Romania, Serbia, Slovenia, Turkey). Changes in heat wave number, length and intensity between 1960 and 2006 are quantified. Daily temperature homogeneity analysis suggest that many instrumental measurements in the 1960s are warm-biased, correcting for these biases regionally averaged heat wave trends are up to 8% higher. We find significant changes across the western Balkans, southwestern and western Turkey, and along the southern Black Sea coastline. Since the 1960s, the mean heat wave intensity, heat wave length and heat wave number across the eastern Mediterranean region have increased by a factor 7.6 ±1.3, 7.5 ±1.3 and 6.2 ±1.1, respectively. These findings suggest that the heat wave increase in this region is higher than previously reported.
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Heat wave changes in the eastern Mediterranean since 1960
F. G. Kuglitsch,
1,2
A. Toreti,
1,2,3
E. Xoplaki,
1,4
P. M. DellaMarta,
5
C. S. Zerefos,
6
M. Türkeş,
7
and J. Luterbacher
8
Received 25 November 2009; revised 13 January 2010; accepted 19 January 2010; published 17 February 2010.
[1] A new data set of highquality homogenized daily
maximum and minimum summer air temperature series from
246 stations in the eastern Mediterranean region (including
Albania, BosniaHerzegovina, Bulgaria, Croatia, Cyprus,
Greece, Israel, Romania, Serbia, Slovenia, Turkey) is
developed and used to quantify changes in heat wave
number, length and intensity between 1960 and 2006. Daily
temperature homogeneity analyses suggest that many
instrumental measurements in the 1960s are warmbiased,
correcting for these biases regionally averaged heat wave
trends are up to 8% higher. We find significant changes
across the western Balkans, southwestern and western
Turkey, and along the southern Black Sea coastline. Since
the 1960s, the mean heat wave intensity, heat wave length
and heat wave number across the eastern Mediterranean
region have increased by a factor of 7.6 ± 1.3, 7.5 ± 1.3
and 6.2 ± 1.1, respectively. These findings suggest that the
heat wave increase in this region is higher than previously
reported. Citation: Kuglitsch, F. G., A. Toreti, E. Xoplaki, P. M.
DellaMarta, C. S. Zerefos, M. Türkeş, and J. Luterbacher (2010),
Heat wave changes in the eastern Mediterranean since 1960,Geophys.
Res. Lett.,37, L04802, doi:10.1029/2009GL041841.
1. Introduction
[2] Heat waves have discernible impacts including rise in
mortality and morbidity [e.g., Knowlton et al., 2009], an
increased strain on infrastructure (power generation, water
supply, transportation) [e.g., SmoyerTomic et al., 2003] and
consequent impacts on society. Further impacts may include
effects on agricultural resources, the retail industry, eco-
system services and tourism [Ferris et al., 1998; Ciais et al.,
2005]. Large financial losses due to crop shortfall, forest
fires or increased mortality highlight the strong impact
potential of heat waves on our environment, society and
economy [e.g., Kovats and Koppe, 2005; Poumadère et al.,
2005; Intergovernmental Panel on Climate Change, 2007].
In the 21st century the Mediterranean area is expected to be
one of the prominent and vulnerable climate change hot
spots[Giorgi, 2006; Diffenbaugh et al., 2007] that will
experience a large number of extremely hot temperature
events, an increase of summer heat wave frequency and
duration [e.g., Türkeşet al., 2002; Founda et al., 2004;
Kostopoulou and Jones, 2005; DellaMarta et al., 2007] and
increasing summer temperature variability [Xoplakietal.,
2003; Jones et al., 2008]. These studies focus either on
changes in mean monthly maximum temperatures [Türkeşet
al., 2002], dirunal temperature ranges [Türkeşand Sümer,
2004], temperature percentiles [Diffenbaugh et al., 2007],
count series above absolute or percentile based thresholds
[Founda et al., 2004; Kostopoulou and Jones, 2005], and do
not specifically focus on changes in heat wave number, length
and intensity. Moreover, previous studies often lack a rigor-
ous application of inhomogeneity detection and correction
techniques of station data. In order to make our heat wave
analyses applicable to the assessment of climate impacts (e.g.,
human health and the economy) we use (1) a combination of
daily maximum (TX) and minimum air temperatures (TN)
and (2) define temperature thresholds to estimate the begin-
ning and the end of heat waves [Karl and Knight, 1997;
Hémon and Jougla, 2003; Grize et al., 2005; Gosling et al.,
2008]. The importance of considering TN was highlighted
by Karl and Knight [1997] who concluded that three or more
consecutive nights with no relief from very warm nighttime
(minimum) temperatures may be most important for human
health impacts. However, they focused on absolute values i.e.
the annual worst heatevent and did not study periods when
temperature exceeds longterm and locationspecific tem-
perature percentiles which were identified to have crucial
impacts [Meehl and Tebaldi, 2004; Diáz et al., 2006; Della
Marta et al., 2007; Gershunov et al., 2009]. This study uses a
combination of the heat wave definitions (see Chapter 2 for
details) and consequently focuses on heat events when both
TX and TN exceed location specific temperature percentiles
for three or more days. This allows (1) a better and more
reliable comparison of heat waves, and (2) a better identifi-
cation of the spatial extent of longterm heat wave trends. The
detection and analyses of heat waves require high quality and
homogenized instrumental daily data [Kuglitsch et al., 2009].
Here we use for the first time quality controlled and
homogenized TX and TN series of 246 stations across the
eastern Mediterranean covering the period 19602006.
Temperature adjustments due to data homogenization are
usually smaller than 1°C but are crucial for any reliable heat
1
Institute of Geography, Climatology and Meteorology, University
of Bern, Bern, Switzerland.
2
Oeschger Centre for Climate Change Research, University of Bern,
Bern, Switzerland.
3
Istituto Superiore per la Protezione e la Ricerca Ambientale,
Rome, Italy.
4
The Cyprus Institute, EEWRC, Nicosia, Cyprus.
5
Federal Office for Meteorology and Climatology, MeteoSwiss,
Zurich, Switzerland.
6
Biomedical Research Foundation, Academy of Athens, Athens,
Greece.
7
Physical Geography Division, Department of Geography, Faculty
of Sciences and Arts, Çanakkale Onsekiz Mart University, Çanakkale,
Turkey.
8
Department of Geography, Climatology, Climate Dynamics and
Climate Change, JustusLiebig University of Giessen, Giessen, Germany.
Copyright 2010 by the American Geophysical Union.
00948276/10/2009GL041841$05.00
GEOPHYSICAL RESEARCH LETTERS, VOL. 37, L04802, doi:10.1029/2009GL041841, 2010
L04802 1of5
wave study [cf. Kuglitsch et al., 2009] (see auxiliary
material).
1
The analyses of trends of shorter and smaller
scale events give results that differ significantly depending
on the use of homogenized or raw data [DellaMarta et al.,
2007; Kuglitsch et al., 2009]. The present study investigates
the evolution of summer heat waves in the eastern Medi-
terranean since 1960s focusing on the number, length and
intensity of the heat waves based on new highquality and
homogenized TX and TN datasets.
2. Data and Methods
[3] Homogenized daily extended summertime (JJAS) TX
and TN series recorded at 246 stations in the eastern Medi-
terranean region are used. Most of the series cover the period
1960 to 2006. The data set contains data from the European
Climate Assessment and Dataset (ECA&D) [Klein Tank et
al., 2002], the Turkish State Meteorological Service and the
Hellenic National Meteorological Service. The most com-
plete time period is identified between 1969 and 1998 and
used as the reference period in the data homogenization and
the heat wave analyses. The full data set is quality controlled
(see Kuglitsch et al. [2009] for details) and homogenized
using highly correlated neighbouring series (see Figure S1
for the stations used, the length of the time series and the
detected break points). Based on the new homogenized TX
and TN data sets, summer heat wave numbers, lengths and
intensities are calculated. As there is no universal definition
to quantify heat waves based on both TX and TN, we
developed a new characterization (based on work by Meehl
and Tebaldi [2004] and DellaMarta et al. [2007]) consid-
ering only periods of three or more consecutive hot days and
nights. A hot day/night is defined as a day/night when the
daily TX/TN exceeds the longterm (19691998) daily 95th
percentile within the JuneSeptember season (122 days).
For each JuneSeptember day, a 95th percentile is calcu-
lated from a sample of 15 days (seven days on either side
of the respective day [DellaMarta et al., 2007]) using data
over the 1969 to 1998 period. A heat wave (HW) is
defined as a period of three or more consecutive hot days
and nights not interrupted by more than one nonhot day
or night. Figure 1 provides a schematic overview of heat
waves detected for the station of Ankara (Turkey) for the
summer of 2006. For estimating the heat wave intensity we
compute the local TX exceedances (i.e. degree days in °C).
Since TX and TN are highly correlated we replace TN
with TN conditional (TNc) on TX (TNc = TN|TX) and
sum the TX exceedances with TNc exceedances, obtain-
ing the local summertime heat wave intensity index,
HWI95 ¼P
i
maxðTXiTX95;i;0ÞþP
i
maxðTNciTNc95;i;0Þ,
for iranging from June 1 to September 30, resulting in an
annually resolved time series at each station. The new var-
iable TNc is derived from estimating the relationship between
TN and TX, i.e. TN =f(TX)+". A penalized spline smoothing
with a restricted maximum likelihood parameter estimate
[Krivobokova and Kauermann, 2007] is applied to each
series. Moreover the maximum heat wave intensity index
(HWMAXI
95
, in °C), of the longest heat wave per summer is
calculated. We also focus on changes in heat wave number
(HWN
95
) characterizing the number of summer heat waves
per year, and the heat wave length (HWL
95
, in days) of all
summer heat waves, and maximum heat wave length
(HWMAXL
95
, in days) per summer season. For comparison
purposes, the 95th percentile for TX (TX95perc) and TN
(TN95perc) are calculated for the entire summer season as
shown in Figure 1 (thin black dashed line). Linear trends of
TX95perc,TN95perc,HWN
95
,HWL
95
and HWI
95
and their
significance are estimated using the ordinary least square
technique (OLS) and the MannKendall rank correlation test
for the period 1960 to 2006.
3. Results and Discussion
[4] In the eastern Mediterranean region 61% and 74% of
the TX and TN time series are affected by artificial break
points caused by site displacements, new instrumentation or
landuse changes. This underlines the importance of data
homogenization for analyzing extreme events (cf. Figure S1).
Results from the daily temperature homogeneity analysis
suggest that many instrumental measurements in the 1960s
are warmbiased and agree with findings by DellaMarta et
al. [2007] and Kuglitsch et al. [2009] for other European
and Mediterranean regions. The mean correction (°C ±
standard error) of these biases results in an overall reduction
in TX95perc (0.05°C ± 0.03°C), TN95perc (0.07°C ±
0.02°C), HWN
95
(0.2 ± 0.01), HWL
95
(0.5 days ± 0.02 days)
and HWI
95
(2.0°C ± 0.11°C) in the 1960s compared to
the raw data. The corrections made to the series in this
period have a substantial influence on the overall heat wave
trends. Figure 2 summarizes the impact of data homogeni-
zation on longterm HWN
95
trends and indicates that 24%
of the series show a significant change in trend when using
homogenized data. During the 1960s many station screens
were changed in terms of type, size and ventilation, the latter
making measured temperatures closer to the ambient tem-
perature [e.g., Aguilar et al., 2003]. Since the 1960s the
temperature of hot summer days and nights (expressed as the
seasonal TX and TN 95th percentile) and the number, length
and intensity of heat waves have increased significantly.
Yeartoyear variability of HWN
95
, HWL
95
and HWI
95
are
highly correlated with each other (r
2
> 0.97). However, since
2000 the increase of HWI
95
proceeds stronger than those
of HWL
95
and HWN
95
(compare Figure S2). The reduced
increase of HWL
95
and HWN
95
can be explained by longer
Figure 1. Schematic overview of heat wave detection. The
thick black lines (thin dashed black lines) indicate the daily
(seasonal) 95th percentile and daily values of 2006 (thin
black lines) for TX and TN for the station of Ankara,
Turkey. Red areas characterize hot days and nights. Red dotted
frames indicate the three 2006 heat waves.
1
Auxillary materials are available in the HTML. doi:10.1029/
2009GL041841.
KUGLITSCH ET AL.: HEAT WAVES IN THE EASTERN MEDITERRANEAN L04802L04802
2of5
and merging heat wave events. Moreover, TX95perc has
increased stronger than TN95perc since 1990 (not shown)
[Moberg et al., 2006]. This trend is expected to continue in
the SRES A2 emission scenario until the end of the 21st
century [Diffenbaugh et al., 2007]. Regional climate model
(RCM) projections [e.g., Meehl and Tebaldi, 2004;
Diffenbaugh et al., 2007; Founda and Giannakopoulos,
2009; Zanis et al., 2009] agree on the intensification, higher
frequency and longer duration of heat waves by the end of
the 21st century for Mediterranean regions. However, their
assumptions are only based on TX95perc and TN95perc, two
parameters which in our case explain heat wave number,
length and intensity by only 63% and 60%. Therefore a
projection of future heat waves using only these parameters
might not give a full description of changes in number, length
and intensity.
[5] Linear trends (°C/decade ± mean standard error of the
trend of the mean TX95perc; OLS method) of the seasonal
TX and TN 95th percentile (TX95perc, TN95perc) show a
significant (MannKendall test) increase for most of the
series analyzed (Figure S3). The mean estimated trend in
TX95perc (+0.38 ± 0.04°C/decade) over all stations is
higher than in TN95perc (+0.30 ± 0.02°C/decade). These
trends agree with findings for other European regions and
the western Mediterranean [Moberg et al., 2006]. While the
TX95perc increase is highest in continental areas, the
maximum increase of TN95perc is found generally in
coastal areas. Only along the Turkish Mediterranean coast-
line and in parts of southeastern Anatolia TN95perc in-
creased more than TX95perc. Overall, the strongest increase
(>+0.63°C decade) of TX95perc and TN95perc are found
across the western Balkans, southwestern and western
Turkey, and along the eastern parts of the Turkish Black Sea
coastline (Figure S3, dark red dots). The smallest changes
in both, TX95perc and TN95perc are prevalent around the
western Aegean, eastern and southeastern Anatolia. A sig-
nificant decrease in TX95perc is found at Anamur (0.27 ±
0.05°C/decade) and Finike (0.20 ± 0.04°C/decade) along
the south coast of Turkey. A significant decrease (0.19 ±
0.04 to 0.58 ± 0.14°C/decade) in TN95perc is detected in
Kjustendil (Bulgaria), Tanagra, Tripoli (Greece), Egirdir,
Erzincan, Sariz and Urgup (Turkey). These stations show
0.61.6°C higher temperatures in the 1960s compared to the
last 10 years and are either located in higher altitudes (900
1,500 amsl) or very close to sea level. Significant differ-
ences in temperature and heat wave trends in terms of alti-
tude are not found. It is notable that stations showing
negative temperature trends are highly exposed and strongly
influenced by topography driven local climate effects. This
might increase the uncertainty of the homogenization pro-
cedure and cause underestimated temperature adjustments in
the 1960s [Kuglitsch et al., 2009]. Between 1960 and 2006
a significant increase in regional mean HWI
95
(+1.33 ±
0.06°C/decade), HWN
95
(+0.17 ± 0.01/decade) and HWL
95
(+0.85 ± 0.02 days/decade) is found for 56%, 47% and 37%
of all stations, respectively (Figure 3). A significant increase
in HWMAXI
95
(+1.42 ± 0.03°C/decade) and HWMAXL
95
(+0.70 ± 0.01 days/decade) is found for 46% and 19% of all
stations, respectively. We identify hot spotsof heat wave
change across the western Balkans, southwestern and
western Turkey, and along the Turkish Black Sea coast-
line. There, trends of HWI
95
, HWN
95
and HWL
95
exceed
+2.0°C/decade, +0.4/decade and +2.0 days/decade, respec-
tively. Stations that show nonsignificant heat wave changes
cluster in continental parts of the Balkan Peninsula, Greece,
parts of western Turkey, eastern Anatolia and higher alti-
tudes. Areas with strongest heat wave trends generally agree
with areas affected by largest TX95perc and TN95perc
trends, however many stations across the Balkan Peninsula
and eastern Anatolia show a significant increase of daytime
and nighttime temperatures but do not show significant
changes in heat wave trends (Figures S3 and 3). The eastern
Mediterranean has experienced an increase of HWI
95
,
HWL
95
and HWN
95
by a factor 7.6 ± 1.3, 7.5 ± 1.3 and 6.2 ±
1.1, respectively, by comparing the 1960s with the period
19972006 (compare Figure S1). HWMAXI
95
and
HWMAXL
95
have increased by factor 5.6 ± 1.1 and 5.4 ± 1.0.
We are aware that heat wave trends can be biased by one
extreme event and OLS method is not most suitable to
model variations of heat waves over time since there is little
variability in the period 19601985. However, the linear
trends give an indication of the heat wave change. As we use
Figure 2. Differences in linear trends of HWN
95
(homogenized data minus nonhomogenized data) from 1960 to 2006
using the OLS method. Red(blue) colored dots indicate a significant increase (decrease) of HWN
95
trends at the
5% significance level (MannKendall test) after the data homogenization. Red(blue) colored open circles characterize
nonsignificant positive (negative) trends. Grey colored open circles indicate stations with no change in trend.
KUGLITSCH ET AL.: HEAT WAVES IN THE EASTERN MEDITERRANEAN L04802L04802
3of5
a combined heat wave definition based on TX and TN a
comparison with other studies is not possible.
4. Conclusions and Outlook
[6] TX and TN series of 246 stations across the eastern
Mediterranean region have been homogenized and used for
estimating changes in heat wave number, length and inten-
sity. After data homogenization, the increase of temperature
and heat wave indices is significantly enhanced due to
overall negative temperature adjustments in the 1960s.
Averaged over the whole area, hot summer daytime
(TX95perc) and nighttime temperature (TN95perc) have
increased by +0.38 ± 0.04°C/decade and +0.30 ± 0.02°C/
decade, respectively since the 1960s. The mean heat wave
intensity (HWI
95
), heat wave length (HWL
95
) and heat wave
number (HWN
95
) across the whole eastern Mediterranean
region have increased by a factor of 7.6 ± 1.3, 7.5 ± 1.3 and
6.2 ± 1.1, respectively. Hot spotsof heat wave changes
are identified along the eastern parts of the Turkish Black
Sea coastline, in western, southwestern and central Turkey,
and across the western Balkans. The increase in HWI
95
and
Figure 3. Linear trends of (a) HWI
95
(°C/decade), (b) HWL
95
(days/decade) and (c) HWN
95
(number/decade) from 1960
to 2006 using the OLS method. Red(blue) colored dots indicate significant positive (negative) linear trends at the 5%
significance level (MannKendall test). Open circles characterize nonsignificant trends.
KUGLITSCH ET AL.: HEAT WAVES IN THE EASTERN MEDITERRANEAN L04802L04802
4of5
HWL
95
is much more pronounced than changes in the
longest heat wave intensity (HWMAXI
95
) and length
(HWMAXL
95
). This implies that the eastern Mediterranean
is more affected by an accumulation of short (<6 days) but
more intense heat wave events compared to past decades. At
many stations the longest heat wave event per year has not
lengthened and intensified, yet, however a trend of merging
i.e. longer lasting and more intense events have been detected
since 2000. Further investigations will focus on single heat
wave events, their relation to large scale atmospheric circula-
tion, landuseatmosphere interactions, and impacts on human
health, livestock, ecosystem vitality, agricultural production,
water supply, power generation and the comparison with
RCMs at daily time scales.
[7]Acknowledgments. We are grateful to G. van der Schrier and
partners from the ECA&D at the KNMI, the Hellenic National Meteorolog-
ical Service, O. M. Gokturk, and the Turkish State Meteorological Service
for providing data. This research was funded by the 6th EU Framework
Programm CIRCE (#036961). JL acknowledges support from the 7th EU
Framework program ACQWA (#212250) and MedClivar (http://www.
medclivar.eu/). The reviewers made useful comments and suggestions
and helped to improve the quality of this study.
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Türkeş, M., U. M. Sümer, and I. Demir (2002), Reevaluation of trends and
changes in mean, maximum and minimum temperatures of Turkey for
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P. M. DellaMarta, Federal Office for Meteorology and Climatology,
MeteoSwiss, Kraehbuehlstr. 58, CH8044 Zurich, Switzerland.
F. G. Kuglitsch and E. Xoplaki, Institute of Geography, Climatology
and Meteorology, University of Bern, Hallerstr. 12, Bern CH3012,
Switzerland. (franz.kuglitsch@giub.unibe.ch)
J. Luterbacher, Department of Geography, Climatology, Climate
Dynamics and Climate Change, JustusLiebig University of Giessen,
Senckenbergstr. 1, Giessen D35390, Germany.
A. Toreti, Istituto Superiore per la Protezione e la Ricerca Ambientale,
Via Vitaliano Brancti 48, I00144 Rome, Italy.
M. Türkeş, Physical Geography Division, Department of Geography,
Faculty of Sciences and Arts, Çanakkale Onsekiz Mart University,
Terzioglu Campus, 17010 Çanakkale, Turkey.
E. Xoplaki, The Cyprus Institute, EEWRC, P.O. Box 27456, CY1645
Nicosia, Cyprus.
C. S. Zerefos, Biomedical Research Foundation, Academy of Athens,
4 Soranou Ephessiou, GR115 27 Athens, Greece.
KUGLITSCH ET AL.: HEAT WAVES IN THE EASTERN MEDITERRANEAN L04802L04802
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... For future projections from 2071 to 2100, an increase of 1 C in summer temperatures is expected in the spring and autumn seasons in this region (Türkeş, 2012). Many studies have indicated the increase in the average and extreme temperatures over Turkey and/or the eastern Mediterranean (Arseni-Papadimitriou and Maheras, 1991;Kadıo glu, 1997;Kadıo glu et al., 2001;Türkeş et al., 2002;Xoplaki et al., 2003;Türkeş and Sumer, 2004;Kostopoulou and Jones, 2005;Diffenbaugh et al., 2007;Alpert et al., 2008;Giorgi and Lionello, 2008;Hertig et al., 2010;Kuglitsch et al., 2010;Acar Deniz and Türkeş, 2011;Karabulut, 2012;Toros, 2012;Acar Deniz, 2013;Simolo et al., 2014;Acar Deniz and Gonencgil, 2015;Bayer Altın and Barak, 2017;Aksu, 2021). Climate modelling studies have indicated that warming is expected to continue at a higher rate in the Mediterranean Basin until the end of the twenty-first century (Mariotti et al., 2015). ...
... Since various synoptic systems dominate the weather of Turkey in summer and winter as well as for the transitional seasons, the change in these systems interacts with Turkey's climate. The eastern Mediterranean region's mean heatwave intensity, heatwave length, and number of heatwaves have all increased since the 1960s (Kuglitsch et al., 2010). The least change in the winter season can be an indicator of the least change in polar air mass characteristics affecting Turkey, such as Icelandic low pressures and Siberian high pressures. ...
Article
Significant changes in the onset, length and thermal characteristics of seasons have been reported all over the globe in recent decades; however, the spatiotemporal changes of seasonal characteristics in Turkey have received little attention in relation to seasons delineation. In this study, the changes in the characteristics of Turkish seasons have been examined from 1965 to 2020 by considering the daily average temperature data obtained from 65 meteorological stations. A non‐static definition of season onset was used to delineate the seasons. The study also presents the response of seasons timing and thermal characteristics affected by climate change. All over Turkey, the beginning of summer was determined to be 2.1 days/decade from 1965 to 2020, while the beginning of winter has shifted forward at many stations in southeastern Anatolia. All the seasons have experienced increases in average temperatures. The maximum increase was in summer seasons and occurred at up to a rate of 0.7°C/decade. There has been almost no change in winter temperatures over the Mediterranean region. Eastern Marmara with the western and middle Black Sea regions experienced an extension of spring as well as a shortening of the autumn season. It was noted that the change in the beginning of summer occurred all over the country. However, the extension of spring and shortening of the autumn season was mainly limited to the western Black Sea regions. The seasons, defined by considering climate change and variability, showed significant trends for length, average temperature and their onset. To the best of the author’s knowledge, the delineation of seasons using a dynamic approach is the first attempt of its kind in this study area.
... The rise in extreme heat events under the intermediate and high GHG emissions scenarios could affect the countries of Mediterranean and Eastern Europe significantly, even by the middle of the century, where the heat-related mortality could increase by a factor of 1.8 and 2.6, respectively, compared to the 1971-2000 period [4]. Generally, the region around the Mediterranean basin, including Southeastern Europe, appears to be one of the most vulnerable to climate change, with an increasing intensity of extreme weather and heat events [1,21,26,27] and a further increase in the previously observed summer heatwaves' frequencies and durations [28][29][30]. In southern Europe, prolonged hot weather periods are a typical summertime phenomenon due to the warmer climate and larger-scale atmospheric dynamics that favor the thermodynamic processes and land-atmosphere feedback [26,31]. ...
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Many studies in the last few years have been dedicated to the increasing temperatures and extreme heat in Europe since the second half of the 20th century because of their adverse effects on ecosystems resilience, human health, and quality of life. The present research aims to analyze the spatio-temporal variations of extreme heat events in Southeastern Europe using daily temperature data from 70 selected meteorological stations and applying methodology developed initially for the quantitative assessment of hot weather in Bulgaria. We demonstrate the suitability of indicators based on maximum temperature thresholds to assess the intensity (i.e., magnitude and duration) and the tendency of extreme heat events in the period 1961–2020 both by individual stations and the Köppen’s climate zones. The capability of the used intensity-duration hot spell model to evaluate the severity of extreme heat events has also been studied and compared with the Excess Heat Factor severity index on a yearly basis. The study provides strong evidence of the suitability of the applied combined approach in the investigation of the spatio-temporal evolution of the hot weather phenomena over the considered domain.
... S3, S4). These findings highlight that heat extremes have become and will become more intense, frequent, and longer lasting with changing climate (Ga 2004;Kuglitsch et al. 2010). Similarly, less than 10% of the locations experienced more frequent heat extremes (lower end) for at least one index, mainly in parts of Northern Europe and the Mediterranean region. ...
Article
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With global warming, many climate extremes are becoming more frequent, often co-occurring, or repeatedly occurring in consecutive years. However, only limited studies have investigated these changes of climate extremes together. We study these changes in Europe for the last seven decades (1950–2019) based on 39 climate indices to identify climate extreme hotspots and coldspots. These indices belong to the four climate index groups: cold, heat, drought, and precipitation. Compared to the first half of the study period (1950–1984), most of our study locations faced heat extremes that are more frequent and occurring in consecutive years in the second half (1985–2019). However, the number of cold extremes has decreased in most locations. Simultaneously, some locations, mainly the Mediterranean region, faced an increase in droughts while others, e.g., parts of Eastern Europe and Northern Europe, experienced more intense precipitation. Two or more of these cold, heat, drought, and precipitation extremes have also co-occurred in a few locations of our study area in the same year. Our study highlights that climate extremes are becoming more frequent, co-occurrent, and persistent in Europe. These changes in climate extremes are associated with climate change. Therefore, we could infer that climate change mitigation is crucial for limiting these extremes.
... With respect to other types of extremes (e.g., extreme precipitation), there is high confidence in the human contribution to the observed increases of heat extremes in the broader region (IPCC, 2021). In the past decades, extreme weather events' characteristics, including the frequency, duration, and intensity of heatwaves, have amplified across the EMME (Abbasnia & Toros, 2019;Ceccherini et al., 2017;Donat et al., 2014;Hochman et al., 2022;Kostopoulou & Jones, 2005;Kuglitsch et al., 2010;Lelieveld et al., 2016;Nashwan et al., 2018;Tolika, 2019). Particularly in the Middle East, the observed trend of cumulative heat (i.e., the product of all seasonal heatwave days, including heatwave frequency and average heatwave intensity) is +50% per decade, being among the highest in the world (Perkins-Kirkpatrick & Lewis, 2020). ...
Article
Full-text available
Observation-based and modelling studies have identified the Eastern Mediterranean and Middle East (EMME) region as a prominent climate change hotspot. While several initiatives have addressed the impacts of climate change in parts of the EMME, here we present an updated assessment, covering a wide range of timescales, phenomena and future pathways. Our assessment is based on a revised analysis of recent observations and projections and an extensive overview of the recent scientific literature on the causes and effects of regional climate change. Greenhouse gas emissions in the EMME are growing rapidly, surpassing those of the European Union, hence contributing significantly to climate change. Over the past half-century and especially during recent decades, the EMME has warmed significantly faster than other inhabited regions. At the same time, changes in the hydrological cycle have become evident. The observed recent temperature increase of about 0.45°C per decade is projected to continue, although strong global greenhouse gas emission reductions could moderate this trend. In addition to projected changes in mean climate conditions, we call attention to extreme weather events with potentially disruptive societal impacts. These include the strongly increasing severity and duration of heatwaves, droughts and dust storms, as well as torrential rain events that can trigger flash floods. Our review is complemented by a discussion of atmospheric pollution and land-use change in the region, including urbanization, desertification and forest fires. Finally, we identify sectors that may be critically affected and formulate adaptation and research recommendations towards greater resilience of the EMME to climate change.
... Recent projections indicate that such a surge in the frequency of MHWs could persevere for the whole current century [5] as the consequence of the persisting global ocean warming. Over the last two decades, several MHWs have been recorded globally [3,7], including in the Mediterranean Sea [8][9][10]. Being a miniature, shallow and warm ocean more prone to climate change than the open oceans [11], the annual mean SST of the Mediterranean basin is expected to increase from +1.5 • C to +3 • C by the end of the 21st century, fostering MHWs' occurrence [9,12]. ...
Article
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Since rising temperature (T) will enhance biochemical reactions and coastal marine sediments are hotspots of carbon cycling, marine heatwaves’ (MHWs’) intensification caused by climate change will affect coastal biogeochemistry. We investigated the effects of MHWs on sediment organic matter (OM) in a nearshore locality (NW Sardinia, Mediterranean Sea) receiving an artificial warm water plume generating T anomalies of 1.5–5.0 °C. Sediments were collected before and after 3 and 11 weeks from the initial plume release. Both MHWs influenced sedimentary OM quantity, composition, and degradation rates, with major effects associated with the highest T anomaly after 3 weeks. Both MHWs enhanced sedimentary OM contents, with larger effects associated with the highest T anomaly. Phytopigment contents increased in the short term but dropped to initial levels after 11 weeks, suggesting the occurrence of thermal adaptation or stress of microphytobenthos. In the longer term we observed a decrease in the nutritional quality of OM and a slowdown of its turnover mediated by extracellular enzymes, suggestive of a decreased ecosystem functioning. We anticipate that intensification of MHWs will affect benthic communities not only through direct effects on species tolerance but also by altering benthic biogeochemistry and the efficiency of energy transfer towards higher trophic levels.
... In the summer, there is a noticeable decrease in precipitation, and rising temperatures are expected as a result of climate change [17]. Furthermore, the magnitude and frequency of heatwaves [18], as well as the daily temperature limits, are increasing as a result of projection estimates [19]. A change is expected in winter precipitation [20] and daily temperatures, together with a decreasing trend in the number of frosty days [21]. ...
Article
This paper focuses on climate change in Turkey caused by energy consumption using an Autoregressive Distributed Lag and Toda-Yamamoto causality analysis. The motivation and aim are: Finding evidence of causality for the relationship between energy consumption, growing economies and climate change depending on parameters that vary over time, which are observed and argued through political implications. Temperature and precipitation are the dependent variables for climate change; energy types and Gross Domestic Product per capita are the independent variables for economic determiners. Data was collected annually from various institutions between 1980-2019. According to the Toda-Yamamoto tests, a negative relationship is determined between renewable energy consumption and temperature in both the short and long term. The results reveal that a 1% increase in renewable energy reduces the temperature by 0.031%. The increase of renewable energy may help in decreasing temperature. Precipitation and non-renewable energy consumption have a positive relationship in both the short and long term, with a 1% increase in non-renewable energy consumption causing a 0.175% increase in precipitation, indicating a negative effect on climate change. Encouraging renewable energy consumption through government incentives can be a powerful solution to decrease the negative effects of climate change in Turkey.
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The Mediterranean has been identified as a ‘climate change hot spot’, already experiencing faster warming rates than the global average, along with an increased occurrence of heat waves (HWs), prolonged droughts, and forest fires. During summer 2021, the Mediterranean faced prolonged and severe HWs, triggering hundreds of wildfires across the region. Greece, in particular, was hit by one of the most intense HWs in its modern history, with national all-time record temperatures being observed from 28 July to 6 August 2021. The HW was associated with extreme wildfires in many parts of the country, with catastrophic environmental and societal consequences. The study accentuated the rarity and special characteristics of this HW (HW2021) through the analysis of the historical climate record of the National Observatory of Athens (NOA) on a centennial time scale and comparison with previous HWs. The findings showed that HW2021 was ranked first in terms of persistence (with a total duration of 10 days) and highest observed nighttime temperatures, as well as ‘cumulative heat’, accounting for both the duration and intensity of the event. Exceptionally hot conditions during nighttime were intensified by the urban heat island effect in the city of Athens. Human exposure to heat-related stress during the event was further assessed by the use of bioclimatic indices such as the Universal Thermal Climate Index (UTCI). The study points to the interconnected climate risks in the area and especially to the increased exposure of urban populations to conditions of heat stress, due to the additive urban effect.
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Increasing popularity of oat were accompanied with the introductions of many new cultivars for the last few decades. Aim of this study were to characterize the growth and developments of Kahraman, Küçükyayla, Yeniçeri, Sebat, Otağı and Diriliş oat cultivars using sigmoidal growth models. Growth data comprised of weekly observations of dry weights and growth stages with three samplings for two consecutive years. Results indicated that the growing season were the determining factor for the dry matter accumulation until the stem elongation stage since genotype differences became apparent only in the later stages. Sigmoidal growth models successfully fitted to the growth data and allowed for further evaluations. Goodness of fit statistics implied that Logistic, Logistic Power and Ratkowsky models were the best fitting growth models to explain dry matter accumulations of oat cultivars. Analysis also showed that Otağı, Yeniçeri and Sebat cultivars reached the highest dry matter accumulations. Point of inflections on the Logistic models indicated that Küçükyayla and Kahraman were the earliest cultivars in the Marmara region. Comparison of cultivars by using the growth models proved to be informative in terms of understanding the genotypic variation.
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Extreme heat events are becoming more frequent and more severe in the Pacific Northwest and in comparable dry-summer climates worldwide, increasing the occurrence of heat-related illness and death. Much of this risk is attributed to overheating in multifamily dwellings, particularly in neighborhoods with abundant asphalt, few trees, and limited financial resources. Air-conditioning expansion is problematic, however, because it creates vulnerability to operational costs and power outages, while expelled hot air intensifies urban heat island effects. In contrast, passive cooling strategies that deflect solar radiation and recruit the cool night air typical of Mediterranean, semi-arid, and arid climates are quite promising, but their abilities to improve residential survivability during extreme heat have not yet been explored. To understand this potential, here we investigate the extent to which well-controlled shading and natural ventilation, in some cases with fan assistance, could have diminished the hours in which indoor heat index levels exceeded ‘caution’, ‘extreme caution’, ‘danger’, and ‘extreme danger’ thresholds during the June 2021 heat wave in the Pacific Northwest; building thermal performance was simulated in EnergyPlus under conditions experienced by Vancouver BC, Seattle WA, Spokane WA, Portland OR, and Eugene OR. Strikingly, we find that in Portland, where the highest temperatures occurred, integrated shading and natural ventilation eliminated all hours above the danger threshold during the 3-day event, lowering peak indoor air temperatures by approximately 14 °C (25 °F); without cooling, all 72h exceeded this threshold. During the encompassing 10-day period, these passive measures provided 130–150h of thermal relief; baseline conditions without cooling provided none. Additionally, passive cooling reduced active cooling loads by up to 80%. Together, these results show the immediate, substantial value of requiring effective operable shading and secure operable windows in apartments in mild dry-summer climates with rising heatwave intensity, as well as public health messaging to support the productive operation of these elements.
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Marine Heatwaves (MHW) and Cold Spells (MCS) in the Mediterranean Sea have been extracted from an SST dataset from which the annual warming trend had been removed. The number of events per year (max 6) and their intensity resulted stable, indicating that the increasing occurrence of actual MHW in the last decades is mainly due to the warming rate. The extent (daily mean around 10% of the basin surface) and duration of events (around 36 days per year) decreased at a rate of -15% and -13% per decade, respectively. The decrease, concentrated in summer for MCS and in winter for MHW, explains the difference between the summer and winter warming rates of the basin. The decrease of summer MCS and winter MHW is probably caused by the shorter duration of extreme atmospheric events.
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The deadly heat wave of July 1995 that affected much of the U.S. midwest, most notably Chicago, Illinois, has been put into historical perspective. The heat wave has been found to be remarkably unusual, but only partially because of the extreme high apparent temperatures (an index of the combined effect of temperature and humidity on humans), where the authors calculate a return period of the peak apparent temperature of 23 yr. Of greater significance were the very high temperatures that persisted day and night over an extended 48-h period. Analysis presented here indicates that for Chicago such an extended period of continuously high day and night apparent temperature is unprecedented in modern times. The 2-day period where the minimum apparent temperature failed to go below 31.5°C (89°F) is calculated to be an extremely rare event (probability of occurrence
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(1) We find that elevated greenhouse gas concentrations dramatically increase heat stress risk in the Mediterranean region, with the occurrence of hot extremes increasing by 200 to 500% throughout the region. This heat stress intensification is due to preferential warming of the hot tail of the daily temperature distribution, with 95th percentile maximum and minimum temperature magnitude increasing more than 75th percentile magnitude. This preferential warming of the hot tail is dictated in large part by a surface moisture feedback, with areas of greatest warm-season drying showing the greatest increases in hot temperature extremes. Fine-scale topographic and humidity effects help to further dictate the spatial variability of the heat stress response, with increases in dangerous Heat Index magnified in coastal areas. Further, emissions deceleration substantially mitigates heat stress intensification throughout the Mediterranean region, implying that emissions reductions could reduce the risk of increased heat stress in the coming decades. Citation: Diffenbaugh, N. S., J. S. Pal, F. Giorgi, and X. Gao (2007), Heat stress intensification in the Mediterranean climate change hotspot, Geophys. Res. Lett., 34, L11706, doi:10.1029/2007GL030000.
Chapter
Although heat waves are rare events, they are associated with significant mortality impacts. A range of measures are available that potentially reduce the impact of extreme temperature episodes on mortality and morbidity, including health promotion, building design, urban planning, and heat wave early warning systems. The effectiveness of health interventions in response to heat waves has not yet been formally evaluated, although there is evidence that they have been effective during major events in the United States. Populations are likely to acclimatize to the changes in mean climate forecast by global climate models. However, it is not known how the frequency or intensity of heat waves will change in the future. Heat deaths are of concern because many populations are aging and the elderly are the most vulnerable to heat-related mortality. The impact of climate change on the exposure to heat stress in urban areas may be exacerbated by increases in the urban heat island effect and other environmental changes.
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Most of the great California-Nevada heat waves can be classified into primarily daytime or nighttime events depending on whether atmospheric conditions are dry or humid. A rash of nighttime-accentuated events in the last decade was punctuated by an unusually intense case in July 2006, which was the largest heat wave on record (1948-2006). Generally, there is a positive trend in heat wave activity over the entire region that is expressed most strongly and clearly in nighttime rather than daytime temperature extremes. This trend in nighttime heat wave activity has intensified markedly since the 1980s and especially since 2000. The two most recent nighttime heat waves were also strongly expressed in extreme daytime temperatures. Circulations associated with great regional heat waves advect hot air into the region. This air can be dry or moist, depending on whether a moisture source is available, causing heat waves to be expressed preferentially during day or night. A remote moisture source centered within a marine region west of Baja California has been increasing in prominence because of gradual sea surface warming and a related increase in atmospheric humidity. Adding to the very strong synoptic dynamics during the 2006 heat wave were a prolonged stream of moisture from this southwestern source and, despite the heightened humidity, an environment in which afternoon convection was suppressed, keeping cloudiness low and daytime temperatures high. The relative contributions of these factors and possible relations to global warming are discussed.
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Spring wheat (Triticum aestivumL., ‘Chablis’) was grown under field conditions from sowing until harvest maturity, except for a 12-d period [70–82 days after sowing (DAS) coinciding with anthesis] during which replicated crop areas were exposed to a range of temperatures within two pairs of polyethylene-covered temperature gradient tunnels. At 82 DAS, an increase in mean temperature from 16 to 25 °C during this treatment period had no effect on above-ground biomass, but increased ear dry weight from 223 to 327 g m-2and, at 83 DAS, reduced root biomass from 141 to 63 g m-2. Mean temperature over the treatment period had no effect on either above-ground biomass or grain yield at maturity. However, the number of grains per ear at maturity declined with increasing maximum temperature recorded over the mid-anthesis period (76–79 DAS) and, more significantly, with maximum temperature 1 d after 50% anthesis (78 DAS). Grain yield and harvest index also declined sharply with maximum temperature at 78 DAS. Grain yield declined by 350 g m-2at harvest maturity with a 10 °C increase in maximum temperature at 78 DAS and was related to a 40% reduction in the number of grains per ear. Grain yield was also negatively related to thermal time accumulated above a base temperature of 31 °C (over 8 d of the treatment from 5 d before to 2 d after 50% anthesis). Thus, grain fertilization and grain set was most sensitive to the maximum temperature at mid-anthesis. These results confirm that wheat yields would be reduced considerably if, as modellers suggest, high temperature extremes become more frequent as a result of increased variability in temperature associated with climate change.
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The European summer of 2003 was exceptionally warm, and there is evidence that human influence has at least doubled the risk of such a hot summer. It is possible that by the 2040s, summers over southern Europe will be as warm or warmer 50% of the time. Because of the related socioeconomic impacts, there is growing interest in investigating changes in climate extremes across the world and how they may change in the future. We examine observed and simulated summer temperatures over a set of regions covering the Northern Hemisphere. Simulated changes are consistent with observed changes over the vast majority of regions when the climate simulation includes changes in anthropogenic and natural influences. We detect the dominant influence of anthropogenic factors on observed warming in almost every region, which has led to a rapidly increasing risk of hot summers. We show that hot summers which were infrequent 20-40 years ago are now much more common and that our projections indicate that the current sharp rise in incidence of hot summers is likely to continue.
Article
The 105-year (1897–2001) surface air temperature record of the National Observatory of Athens (NOA) has been analyzed to determine indications of significant deviations from long-term average features in the city of Athens. The analysis of the whole record reveals a tendency towards warmer years, with significantly warmer summer and spring periods and slightly warmer winters (an increase of 1.23 and 0.34 °C has been observed in the mean summer and mean winter temperature, respectively). The tendency is more pronounced for the summer and spring maximum temperature, but marginal for the minimum temperature of the cold season. On a monthly basis, a statistically significant (at the 95th confidence level) warming trend has been observed in the average maximum temperature of May and June. The trend analysis for the last decade of the record (1992–2001) revealed a significant increase for both warm and cold seasons, yet maximum and minimum temperature. Extreme temperatures (high/low temperatures above/below a certain threshold value) and extreme events (prolonged extreme temperatures) have also been studied. The number of hot days as well as the frequency of occurrence and duration of warm events have significantly increased during the last decade, while a negative trend is observed in the frequency of low temperatures and the duration of cold events especially after 1960.