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Changes in mean and extreme climate in southern South America under global warming of 1.5 °C, 2 °C, and 3 °C

Authors:
Carla Gulizia at Centro de Investigaciones del Mar y la Atmósfera (CIMA/CONICET-UBA)
Carla Gulizia
Gabriela A. Raggio at University of Buenos Aires
Gabriela A. Raggio
Ines Camilloni at Centro de Investigaciones del Mar y la Atmósfera (CIMA/CONICET-UBA)
Ines Camilloni
Ramiro Saurral at Barcelona Supercomputing Center
Ramiro Saurral
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This study provides a regional assessment of mean and extreme temperature and precipitation over South America south of 20°S under global warming of 1.5 °C, 2 °C, and 3 °C above pre-industrial level. A particular analysis is performed over four sub-regions: southeastern South America (SESA), Pampa, southern Patagonia (SPat), and northern Patagonia (NPat), where special interest is given to the differences in impacts between the global warming targets under analysis. Results indicate that the ongoing global warming will maintain and even stress the observed trends in the region. SESA is the region projected to experience the largest increases in both mean and extreme temperature and precipitation, and the magnitude of change becomes larger under the warmer global warming targets. The Patagonian regions are expected to suffer robust reductions in the frequency of frost days (fd) and ice days (id), and there appears to be a relationship between the target and the magnitude of decrease in fd and id over these regions. The present study shows that the degree of global warming will play a key role in determining the intensity and frequency of the climate extremes which could significantly affect the socio-economic activities in the selected climatic sensitive regions over southern South America.
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Vol.:(0123456789)
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https://doi.org/10.1007/s00704-022-04199-x
ORIGINAL PAPER
Changes inmean andextreme climate insouthern South America
underglobal warming of1.5°C, 2°C, and3°C
CarlaN.Gulizia1,2,3 · GabrielaA.Raggio2,3· InésA.Camilloni1,2,3· RamiroI.Saurral1,2,3
Received: 22 November 2021 / Accepted: 29 August 2022
© The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature 2022
Abstract
This study provides a regional assessment of mean and extreme temperature and precipitation over South America south of
20°S under global warming of 1.5°C, 2°C, and 3°C above pre-industrial level. A particular analysis is performed over four
sub-regions: southeastern South America (SESA), Pampa, southern Patagonia (SPat), and northern Patagonia (NPat), where
special interest is given to the differences in impacts between the global warming targets under analysis. Results indicate that
the ongoing global warming will maintain and even stress the observed trends in the region. SESA is the region projected
to experience the largest increases in both mean and extreme temperature and precipitation, and the magnitude of change
becomes larger under the warmer global warming targets. The Patagonian regions are expected to suffer robust reductions
in the frequency of frost days (fd) and ice days (id), and there appears to be a relationship between the target and the magni-
tude of decrease in fd and id over these regions. The present study shows that the degree of global warming will play a key
role in determining the intensity and frequency of the climate extremes which could significantly affect the socio-economic
activities in the selected climatic sensitive regions over southern South America.
1 Introduction
There is robust evidence supporting the fact that human-
induced greenhouse gases emissions have led to significant
alterations in the frequency, intensity, spatial extent, timing,
and duration of some weather and climate extremes com-
pared to pre-industrial conditions, in particular regarding
warm events (Seneviratne etal.2021). This has resulted in
unprecedented extremes over different parts of the globe
such as the mid-latitudes of the Northern Hemisphere (Gross
etal.2020), Antarctica (Saurral etal.2020), or southern
Asia (Yaduvanshi etal.2021). Even more so, over regions
like the Arctic the rapidly evolving warming pattern has
turned events previously considered as extremes to become
routinary nowadays, and this trend is expected to persist in
the upcoming decades (Landrum and Holland2020).
The mid-latitudes of South America have also seen sub-
stantial changes in the intensity and frequency of extreme
events during the last decades (Rusticucci and Barru-
cand2004; Doyle etal. 2012; Skansi etal.2013; Rusti-
cucci etal.2017; Collazo etal.2019a, 2019b; Garreaud
etal.2020; Rivera etal.2021). Temperature-wise, the most
significant trends have been detected in the minimum tem-
perature indices, including positive (negative) trends in the
number of warm (cold) nights over Argentina as well as over
most land regions (Rusticucci 2012; Collazo etal. 2019a,
2019b), although at the same time the frequencies of warm
days have been decreasing in some regions (Rusticucci and
Barrucand2004; Alexander etal. 2006; Donat etal. 2013).
Efforts towards attributing some of these recent extreme
temperature events have found a significant role played by
global warming due to anthropogenic activities (Hannart
etal. 2015; Rusticucci and Zazulie 2021).
Additionally, positive trends in extreme rainfall have been
observed over southeastern South America (Re and Bar-
ros2009; Penalba and Robledo2010; Doyle etal. 2012;
Donat etal. 2013; Zandonadi etal. 2016; Cerón etal.
2021), while decreasing trends were found over other South
* Carla N. Gulizia
gulizia@cima.fcen.uba.ar
1 Facultad de Ciencias Exactas Y Naturales, Departamento de
Ciencias de La Atmósfera Y los Océanos, Universidad de
Buenos Aires, BuenosAires, Argentina
2 Centro de Investigaciones del Mar Y La Atmósfera (CIMA),
CONICET – Universidad de Buenos Aires, BuenosAires,
Argentina
3 Instituto Franco-Argentino Para El Estudio del Clima Y Sus
Impactos (IRL 3351 IFAECI), CNRS – IRD – CONICET –
UBA, BuenosAires, Argentina
/ Published online: 7 September 2022
Theoretical and Applied Climatology (2022) 150:787–803
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... According to these studies, annual mean precipitation projections through the 21st century indicate decreasing precipitation over the northeastern Andes (eastern Colombia and western Venezuela; Almazroui, Ashfaq, et al., 2021;Arias, Ortega, et al., 2021;Ferreira et al., 2023), the southern Andes (Almazroui, Ashfaq, et al., 2021;Ortega et al., 2021;Salazar et al., 2024;Thaler et al., 2021;Zazulie et al., 2018), and tropical South America (Barkhordarian et al., 2018). In contrast, projections suggest increasing precipitation over southeastern South America (Almazroui, Ashfaq, et al., 2021;Avila-Diaz et al., 2023;Ferreira et al., 2023;Gulizia et al., 2022;Lovino et al., 2021;Ortega et al., 2021;Veiga et al., 2023). However, most of these changes are within the range of variability observed since 1950 (Almazroui, Ashfaq, et al., 2021). ...
... Northeastern South America has projections of increasing (decreasing) CDD (consecutive wet days [CWD]; Almazroui, Saeed, et al., 2021;Reboita et al., 2022) becoming a future hotspot of extreme dry days (Vogel et al., 2020). For southeastern South America, projections indicate higher frequency and intensity of daily precipitation extremes, including indices like the number of consecutive wet days (CWD) and RX5day, during the 21st century Gulizia et al., 2022;Lagos-Zúñiga et al., 2022;Reboita et al., 2022). ...
... Also, increases in extreme hot temperatures in southeastern South America and reductions in the frequency of frost days and ice days in Patagonia are projected, which become stronger under higher GWLs (Gulizia et al., 2022). The analysis of CMIP5 projections show increases (decreases) in warm (cold) extremes over southern South America, and changes are more pronounced for the daily minimum temperature-based indices (Rusticucci & Zazulie, 2021 Feron et al. (2019) find that, under a moderate emission scenario, extremely warm summer days and the number of heatwaves per season are expected to increase by the mid-21st century at locations close to the Equator and in the Atacama Desert, while increases are expected to be less pronounced in southern South America. ...
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Weather and climate in South America are influenced by a large variety of processes, including land–atmosphere and ocean–atmosphere interactions, orographic effects, and land use distributions. In addition, human activities are inducing climate change in South America in several ways. The contribution of the Working Group I (WGI) to the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) provides a comprehensive assessment of the scientific evidence published up to 2021, regarding the observed and projected climate changes in South America. An updated synthesis based on results from General Circulation Models (GCMs) of the main projections of climate change in South America published after the IPCC AR6 WGI shows that although GCMs have considerably improved their representation of different aspects of regional climate, they still exhibit systematic errors like the Double Intertropical Convergence Zone bias as well as dry and warm biases in the Amazon and the Andes, respectively. The number of published scientific studies for South America, focused on the physical aspects of regional climate change, has considerably increased since 2021. The most recent literature confirms many of the projections presented in the IPCC AR6 WGI but expands on projections for different aspects of the regional atmospheric circulation and compound extremes. Despite the increasing amount of peer-reviewed literature since 2021, it is important to highlight that projections of annual and seasonal precipitation in South America exhibit large spread and uncertainty. Therefore, the necessity of producing high-resolution projections in South America is key, as is the importance of applying fit-for-purpose analysis focused on the models with physically consistent simulations of regional climate. This could be helpful in the building of the assessment of the physical aspects of climate change in South America to be presented in the next IPCC Assessment Report (AR7).
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... Climate change has led to an increase in global temperature that will, with high confidence, continue during the upcoming years modifying different aspects of the climate system (Almazroui et al. 2021;Gulizia et al. 2022;Collazo et al. 2022;De Luca and Donat 2023;Avila-Diaz et al. 2023;Engdaw et al. 2023;Alexander and Arblaster 2017). However, assessing the differentiated patterns and rates of change in a regional scale is of utmost importance to set up well-informed policy strategies of adaptation and mitigation of the observed and future local changes (IPCC 2021). ...
... Notwithstanding, for both variables, the dispersion within each set of simulations (RCMs and ESD models) was similar and smaller in relation to the RAW CMIP5 ensemble. Furthermore, the mean changes detected here in Tx and Tn, were in agreement with previous works over the region, which identified a future warming amplification over the subtropical Andes and northern Argentina when using CMIP5 and CMIP6 RAW simulations and RCMs for mean surface temperature (Blazquez and Solman 2023;Bustos-Usta et al. 2021;Gulizia et al. 2022;Coppola et al. 2021;Almazroui et al. 2021;Pabón-Caicedo et al. 2020;Zazulie et al. 2018); for extreme temperature indices (Lagos-Zúñiga et al. 2022;Reboita et al. 2022) and compound temperature-rainfall events (Olmo et al. 2022a;Collazo et al. 2023). ...
... The ESD models considerably reduced this dispersion, and also the RCM simulations for the CMIP5 simulations. A pronounced decrease of the number of cold days was detected in the Patagonia region (R5), in line with the results of Gulizia et al. (2022) for the index frost day using CMIP5 RAW simulations. In particular, this reduction could represent a significant impact for the region in terms of snow availability and the conservation of glaciers (Zazulie et al. 2018). ...
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Argentina is a country with a variety of climates, where an increase in mean and extreme temperatures is currently on-going, demanding regional climate information to design and implement effective strategies for climate change adaptation. In this regard, the use of empirical statistical downscaling (ESD) procedures can help provide tailored climate information. In this work, a set of ESD models were tested and applied to generate plausible regional climate projections for daily maximum and minimum temperatures (Tx, Tn) in Argentina. ESD models were applied to an ensemble of CMIP5 and CMIP6 global circulation models (GCMs) to downscale historical and future RCP8.5 and SSP585 scenarios. The plausibility of the ESD projections was analysed by comparing them with their driving GCMs and with CORDEX regional climate models (RCMs). Generally, all ESD models added value during the historical period, in mean values as well as in extreme indices, especially for Tx. The climate projections depicted an extended signal of warming (both in the mean and in the frequency of extremes), consistent between all simulations (GCMs, RCMs and ESD) and strongest over northern Argentina. ESD models showed potential to produce plausible projections, although, depending on the technique considered (for Tx) and the predictor configurations (for Tn), differences in the change rates were identified. Nevertheless, the uncertainty in future changes was considerably reduced by RCMs and ESD when compared to their driving GCMs. Overall, this study evidences the potential of ESD in a climate change context and contributes to the assessment of the uncertainty on the future Argentine climate.
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... EMTs in Chillán and Los Ángeles are more significant compared to Santiago and Talca, with projections suggesting EMTs nearing 40 • C and 41 • C, respectively. Chile has experienced an uninterrupted sequence of dry years since 2010, known as the Mega Drought (MD), the longest drought event recorded in the country [56][57][58][59]. This prolonged water deficit has led to drier soils, which may amplify EMTs through evapotranspiration feedback mechanisms [60,61]. ...
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Extreme maximum temperatures in summer present a significant risk to agroindustry as crops and their ecological interactions have critical thermal limits that can affect their performance and microorganisms-related. Gray mold disease caused by Botrytis cinerea is the most critical disease affecting crops worldwide. In this sense, the impact of temperature on agricultural productivity is well documented in the Northern Hemisphere; the risk of extreme temperatures on the infection rate of B. cinerea in Central Chile is limited. This study analyzes historical climate data from January and February between 1951 and 2023 for the cities of Santiago, Talca, Chillán, and Los Ángeles. The aim was to examine trends in extreme maximum temperatures (EMTs) and develop a simple model to estimate the infection rate of B. cinerea. Linear trend analyses were conducted, as was analysis of the probability of occurrence. Additionally, five-year averages were calculated, and a generic model was presented to assess the effects of warming on the infection rate. The analysis shows positive growth in extreme maximum temperatures in January and February, with projections for 2024, 2025, and 2026 at 70%, 80%, and 80%, respectively. February showed the most significant thermal increase among all stations, with Chillán and Los Ángeles recording higher increases than Santiago and Talca. Projections suggest temperatures near 40–41 °C. The five-year averages for Chillán and Los Ángeles exceeded 37 °C in the 2016–2020 period, the highest values during the analyzed time frame. Trends for 2021–2026 indicate upper limits above 38 °C. These trends, combined with dry summers, could increase the severity of infections and modify the optimal thermal conditions for the pathogen. The results suggest that thermal changes could reduce the infection risk by B. cinerea on fruit crops in Central Chile, and a theoretical approach is proposed to develop predictive tools to facilitate risk assessment in a warming environment.
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... Esta tendencia al calentamiento en las temperaturas medias serían las causantes del retroceso generalizado de glaciares entre los 37° S y 55° S (Camilloni 2018). Además, a nivel estacional se ha observado que los veranos tienden a ser más prolongados y los inviernos más moderados, con una disminución en la ocurrencia de heladas y un incremento en la frecuencia de olas de calor (TCNCC 2015, Gulizia et al. 2022). ...
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... In southeastern South America (SESA), consistent with global patterns, hot temperature extremes have significantly increased since 1960 (Almazroui et al. 2021a;Dereczynski et al. 2020;Reboita et al. 2022), with robust evidence of a human contribution (Seong et al. 2021;Wang et al. 2017). Furthermore, the intensity and frequency of hot events are projected to increase at 1.5 ℃, 2 ℃, and 4 ℃ of global warming (Gulizia et al. 2022;Li et al. 2021). Precipitation extremes-including events such as heavy rainfall, precipitation excesses, and droughts-do not show significant trends, and there is low confidence about the human contribution to observed trends (Avila-Diaz et al. 2023;Lovino et al. 2018a;Regoto et al. 2021). ...
Multi-hazard Assessment of Extreme Hydrometeorological Events in Southeastern South America
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View
... Over our study region in particular, positive trends have been identified in the frequency of heavy precipitation events and heatwaves over the last decades (eg Cerón et al. 2021;Collazo et al. 2019;Doyle and Barros 2012;Rusticucci et al. 2017;Vera and Díaz 2015). At the same time, outputs from dynamical models forced with increased greenhouse gases indicate significant surface warming over most of SSA and more precipitation, particularly over northern Argentina Gulizia et al. 2022;Zaninelli et al. 2019). However, most of the studies have concentrated on individual climatic processes or variables with limited focus into compound events within the region. ...
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... To specifically evaluate crossing times, the IPCC AR6 10 adopted a 20-year mean, whereas, the IPCC Special Report on Global Warming of 1.5°C 9 adopted a 30-year mean, which is also the minimum period for WMO climate normals 13 . Twenty year means have also been regularly used in recent academic literature 14,15,16 . While different methods of accounting for natural fluctuations and long-term trends generally give similar results 3 the level and timing of peak temperature change under strong mitigation scenarios will be sensitive to the length of averaging period used. ...
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... Researchers and farmers should take this into account because it raises the demand for crop water, which in turn puts more strain on the GRB aquifer, which is already over-exploited. Our findings are consistent with the previous research carried out based on CMIP5 and CMIP6 models (Koteswara Rao et al., 2022;Gulizia et al., 2022;Gupta et al., 2020;Almazroui et al., 2020;Li et al., 2020). Zone-1 (Western Himalayan Region) was found to be highly affected by the extreme weather and climatic conditions as results are changing drastically throughout the zone with an increase in the level of warming. ...
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Even if the thresholds set out in the Paris Agreement are reached, several impacts on the climate system are still inevitable, generating new vulnerabilities and amplifying those that already exist. In this sense, the objective of this work was to analyse the impact of a global warming of 1.5 and 2°C in the regional climatological patterns of the near‐surface air temperature and precipitation over South America, locating the most affected regions and briefly discussing the possible impacts to be faced on biodiversity and agriculture. The simulations and projections of 26 General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Phase 5 were used, forced in four different Representative Concentration Pathways (RCPs) scenarios. Projections for 1.5 or 2°C global warming indicate a local increase even higher, of at least +0.5°C, in almost the entire South American continent. Regarding precipitation, a similar pattern was also found between the two thresholds of global warming. GCMs project an increase of about 100 mm year⁻¹ in the southern region of Brazil and in the northern portion of the Brazilian Northeast, in northern Argentina, Uruguay, and parts of Peru, Ecuador, Colombia and Venezuela; while the areas between the south of Chile and Argentina and the extreme north of South America show reductions of up to 150 mm year⁻¹. In addition, both the temperature and precipitation patterns were practically similar between the four analysed RCPs scenarios. The results presented in this study indicate that even if the Paris Agreement is very successful, South America will still suffer several impacts and will need to take effective adaptation measures in the short term. This may have pervasive implications for the biodiversity and genetic resource base of the subcontinent, as well as may impair agricultural productivity or incur into considerable adaptation costs for the sector.
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Comparative Assessment and Future Prediction Using CMIP6 and CMIP5 for Annual Precipitation and Extreme Precipitation Simulation
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  • Jun 2021
This study assesses the improvement of the latest Coupled Model Intercomparison Project Phase 6 (CMIP6) over Coupled Model Intercomparison Project Phase 5 (CMIP5) for precipitation simulation. Precipitation simulations under different future climate scenarios are also compared in this work. The results show that: 1) CMIP6 has no overall advantage over CMIP5 in simulating total precipitation (PRCPTOT) and maximum consecutive dry days (CDD). The performance of CMIP6 increases or decreases regionally in PRCPTOT and consecutive dry days. But it is slightly worse than CMIP5 in simulating very wet days (R95pTOT). 2) Comparing the trend test results of CMIP5 and CMIP6 in the future, there are more areas with significant trend based on Mann–Kendall test in CMIP6 compared with that of CMIP5. The differences in PRCPTOT are mainly found in Amazon Basin and Western Africa. The differences between the R95pTOT trends mainly noticeable in South America and Western Africa, and the differences in CDD are mainly reflected in Central Asia, Sahara Desert and central South America. 3) In Southern South America and Western North America, the PRCPTOT changing rate of CMIP6 in the future under various scenarios is always greater than that of CMIP5; in Alaska, Western Africa, Southern Africa, the PRCPTOT changing rate of CMIP6 in the future under various scenarios is always less than that of CMIP5. In Southern South America, the R95pTOT changing rate of CMIP6 in the future under various scenarios is always greater than that of CMIP5; in Alaska, East Asia, North Asia, the R95pTOT changing rate of CMIP6 in the future under various scenarios is always less than that of CMIP5. In almost half of the regions, the CDD changing rate of CMIP6 is less than that of CMIP5 under all scenarios, namely Australia, Amazon Basin, Southern South America, Central America, Western North America, Central North America, Eastern North America, Central Asia, Tibet.
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Assessment of CMIP6 Performance and Projected Temperature and Precipitation Changes Over South America
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  • Jun 2021
We evaluate the performance of a large ensemble of Global Climate Models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) over South America for a recent past reference period and examine their projections of twenty-first century precipitation and temperature changes. The future changes are computed for two time slices (2040–2059 and 2080–2099) relative to the reference period (1995–2014) under four Shared Socioeconomic Pathways (SSPs, SSP1–2.6, SSP2–4.5, SSP3–7.0 and SSP5–8.5). The CMIP6 GCMs successfully capture the main climate characteristics across South America. However, they exhibit varying skill in the spatiotemporal distribution of precipitation and temperature at the subregional scale, particularly over high latitudes and altitudes. Future precipitation exhibits a decrease over the east of the northern Andes in tropical South America and the southern Andes in Chile and Amazonia, and an increase over southeastern South America and the northern Andes—a result generally consistent with earlier CMIP (3 and 5) projections. However, most of these changes remain within the range of variability of the reference period. In contrast, temperature increases are robust in terms of magnitude even under the SSP1–2.6. Future changes mostly progress monotonically from the weakest to the strongest forcing scenario, and from the mid-century to late-century projection period. There is an increase in the seasonality of the intra-annual precipitation distribution, as the wetter part of the year contributes relatively more to the annual total. Furthermore, an increasingly heavy-tailed precipitation distribution and a rightward shifted temperature distribution provide strong indications of a more intense hydrological cycle as greenhouse gas emissions increase. The relative distance of an individual GCM from the ensemble mean does not substantially vary across different scenarios. We found no clear systematic linkage between model spread about the mean in the reference period and the magnitude of simulated sub-regional climate change in the future period. Overall, these results could be useful for regional climate change impact assessments across South America.
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Present‐day and future climate over central and South America according to CMIP5/CMIP6 models
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In tropical regions, particularly in Central and South America (CSA), the projections of climate seasonality under climate change are still uncertain. This is especially true for ecologically‐relevant variables such as precipitation and temperature. However, assessments of model‐based projections of seasonal climate for this region are scarce. We analyzed the simulation of seasonal precipitation and air surface temperature in CSA and six sub‐regions within from 49 models included in the Coupled Intercomparison Project Phase 5 (CMIP5) and 33 models from CMIP6. In general, continental patterns and seasonality of both variables are moderately well resembled, while most models show systematic biases over the oceans, producing unrealistic spatial patterns. To quantify how well CMIP5/CMIP6 models simulate these variables, we used Taylor diagrams with respect to TRMM for precipitation and ERA5 for temperature. Precipitation shows the largest spread among models. Conversely, temperature shows a better simulation. CMIP5/CMIP6 models exhibit a better performance simulating both variables during December–January–February and March–April–May than during the other seasons. This is partly due to the reduced model biases in representing the Intertropical Convergence Zone during these two seasons. In general, biases are reduced in the CMIP6 models with respect to CMIP5. Regarding regional evaluations, precipitation patterns for Mesoamerica, Cerrado and Chaco regions are better reproduced compared to TRMM, while the annual cycles for the Andes hotspot, Central Chile and Guianas are not well simulated, mainly during their wet seasons. However, these biases are reduced in CMIP6 models. In regard to precipitation projections, models only agree over most of the regions with decreasing precipitation. Conversely, temperature exhibits a general consensus on persistent warming even during the historical period, with an average increase of 6°C by the end of the century, according to the CMIP6 models.
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Colombian climatology in CMIP5/CMIP6 models: Persistent biases and improvements
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  • May 2021
Northern South America is among the regions with the highest vulnerability to climate change. General Circulation Models (GCMs) are among the different tools considered to analyze the impacts of climate change. In particular, GCMs have been proved to provide useful information, although they exhibit systematic biases and fail in reproducing regional climate, particularly in terrains with complex topography. This work evaluates the performance of GCMs included in the fifth and sixth phases of the Coupled Model Intercomparison Project (CMIP), representing the annual cycle of precipitation and air surface temperature in Colombia. To evaluate this, we consider different observational and reanalysis datasets, including in situ gauges from the Colombian Meteorological Institute. Our results indicate that although the most recent generation of GCMs (CMIP6) show improvements with respect to the previous generation (CMIP5), they still have systematic biases in representing the Intertropical Convergence Zone and elevation-dependent processes, which highly determine intra-annual precipitation and air surface temperature in Colombia. In addition, CMIP6 models have larger biases in temperature over the Andes than CMIP5. We also analyze climate projections by the end of the 21st century according to the CMIP5/CMIP6 simulations under the highest greenhouse gases emission scenarios. Models show projections toward warmer air surface temperatures and mixed changes of precipitation, with decreases of precipitation over the Orinoco and Colombian Amazon in September-November and increases over the eastern equatorial Pacific during the entire year.
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Attribution and projections of temperature extreme trends in South America based on CMIP5 models
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Temperature extreme indices were analyzed for five continental regions of southern South America defined according to their climatic characteristics. Gridded observations, reanalysis, and global‐coupled climate models from CMIP5 were used with the approach of temperature extreme trend attribution analysis on fixed‐threshold and percentile‐based temperature extremes indices defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). The largest positive trends are exhibited in the tropical nights index, and a clear anthropogenic signal is evident in the subtropical region. In the subtropical central Andes, there is a decrease in the frost days index and increases in the tropical nights and summer days indices, and an anthropogenic signal is evident. In the Patagonian region, all trends from the historical runs were significant, while the ones from the natural experiment were nonsignificant, showing the marked effect of anthropogenic forcing in this region in the extreme temperature events. Projected changes in extreme indices for the 21st century are consistent with a warming climate, and larger changes are expected in the warm nights index.
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A Decade of Hydrological Drought in Central-Western Argentina
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  • Mar 2021
Most of the water used for the development of the main socio-economic activities in Central-Western Argentina (CWA), an arid to semi-arid region, home to most of the Argentinean wine production, relies on surface streamflow from several snow-fed rivers. During the last decade (2010-2020), reduced snow accumulation over the higher elevations of the Andes mountains triggered the occurrence of hydrological drought over CWA, affecting winter tourism, restricting water use for irrigation and domestic use, and leading to socio-political disputes. This study provides a detailed description of the recent hydrological drought conditions through the use of streamflow records from 15 river basins, which were complemented by precipitation, snowpack and water equivalent thickness measurements to provide a comprehensive picture of the water losses over the last decade. Hydrological drought indices derived from the threshold level method and the standardized streamflow index allowed characterizing the unusualness of this dry period in the context of the last 49 years. The hydrological deficit over the last decade highlighted the challenges faced by the water managers to provide water for irrigation in the main agricultural oases, with a likely overexploitation of the groundwater resources to supplement the limited surface runoff. The hydrological drought severity increased since 2017, with record-breaking levels in several basins, particularly during the period between July 2019 and June 2020 for the rivers located between 35° and 36°S. We identified the main hydrological drought impacts in CWA, as well as the need for improved mitigation strategies to cope with current and future drought conditions. We also analyzed the current limitations in terms of snow and groundwater observations, highlighting the necessity for an effective hydrological drought monitoring system, together with an improved forecast of snow accumulation in the headwaters, which can contribute to better regional water management plans.
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Environmental issues and challenges confronting surface waters in South America: A review
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  • Feb 2021
This study entailed a review of 80 scientific articles on different environmental issues and challenges confronting the rivers, streams and running water in South America. The diversity of issues identified in the review is categorised based on themes that were widely addressed in the studies. Six themes of these are grouped into the following categories: pollution; contamination; climate changes, global warming and/or drought; anthropogenic/human impacts, urbanisation, land use; sedimentation and flooding. Pollution and contamination are the most environmental issues addressed by most of the research work reviewed in this study. These are followed by the impacts of climate vulnerabilities and anthropogenic activities, sedimentation and flooding respectively. These issues transcend one single country but cut across many countries in the continent. This review provides useful information and synthesised insights that support current and future bibliography queries, research and studies of rivers and streams of South America. It is also noted here that both indices of natural and anthropogenic processes are dictating various environmental challenges confronting surface water systems, and the knowledge of the processes and their effects are very important if a proper plan is to be made in addressing those challenges. It is expected that this study serves as a resource for understanding the dynamics of different surface water systems of the continent and as filling the knowledge gap on synthesising the various environmental issues affecting the surface water systems.
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Changes in fire weather climatology under 1.5°C and 2.0°C warming
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The 2015 Paris Agreement led to a number of studies that assessed the impact of the 1.5 ◦C and 2.0 ◦C increases in global temperature over preindustrial levels. However, those assessments have not actively investigated the impact of these levels of warming on fire weather. In view of a recent series of high-profile wildfire events worldwide, we access fire weather sensitivity based on a set of multi-model large ensemble climate simulations for these low-emission scenarios. The results indicate that the half degree difference between these two thresholds may lead to a significantly increased hazard of wildfire in certain parts of the world, particularly the Amazon, African savanna and Mediterranean. Although further experiments focused on human land use are needed to depict future fire activity, considering that rising temperatures are the most influential factor in augmenting the danger of fire weather, limiting global warming to 1.5 ◦C would alleviate some risk in these parts of the world.
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