Weather and Climate Extremes

Sustainability of African weather and climate information can only be ensured by investing in improved scientific understanding, observational data, and model capability. These requirements must be underpinned by capacity development, knowledge management; and partnerships of co-production, communication and coordination.

Climate extremes threaten the land carbon sink and it is important to understand their impact in a changing climate. A recent study provides new insights on reduced forest carbon uptake during the severe 2022 drought and heatwave across Europe.

Weather-related disasters result from complex interactions between vulnerability and exposure through inequality, economic pressure and conflict and intensifying weather extremes in a changing climate, and they should be reported accordingly, suggest a synthesis of the causes and impacts of disasters in 2021 and 2022.

Climate model ensemble boosting can yield physically coherent storylines for record-shattering climate extremes such as the 2021 Pacific Northwest heatwave. Combining information from storyline approaches with process understanding can inform planning for future extremes of unprecedented intensity.

The authors show that a regularly used temperature extreme metric leads to a systematic underestimation of the expected extreme frequency of up to − 75% and propagates to other derived metrics. A simple bias correction is presented to eliminate this error.

The summer jet stream above East Asia has become more variable in recent decades, leading to weather and climate extremes across Eurasia. The authors show that a Scandinavian Pattern in preceding February is driving the strong variability.

Speleothems from the Savanna region in Brazil documents the occurrence of an unprecedented long-term drought driven by anthropogenic forcing. Staring in the 1970´s the current drought is the most severe that has struck the region in the past 700 years.

Changes in atmospheric circulation have reduced the intensity of heat extremes in the midwestern United States since 1979, whereas they intensified warming trends in western Europe, according to analyses of observations and Earth system model simulations.

Extreme heat and drought typical of the end of the century could occur earlier and repeatedly over Europe, and are more likely when they coincide with a warm North Atlantic, according to 100 simulations with an Earth system model.

Heat extremes in Western Europe have increased by an outstanding amount in the last 70 years. Climate models simulate weaker trends. This is largely due to atmospheric circulation trends, favouring heat, missed by climate models.

This paper highlights the potential for improved monitoring and physical understanding to identify windows of opportunity for more confident seasonal forecasts and early warnings of regional climate extremes, such as the Pakistan floods of 2022.

The global risk of record-breaking heatwaves is assessed, with the most at-risk regions identified. It is shown that record-smashing events that currently appear implausible could happen anywhere as a result of climate change.

A warm-season atmospheric river moved from Southeast Asia across the North Pacific in June 2021 and contributed heat and moisture to an ongoing heatwave in western North America, according to analyses of observation-based data and numerical weather prediction model output.

Regional climate warming amplified the exceptional heatwave on the Antarctic Peninsula observed in February 2020, suggest analyses of atmospheric flow analogs.

Climate projections at km-scale show that local hourly precipitation extremes in the UK become 4-times more frequent by 2070, while they do not intensify gradually with warming, but tend to cluster in time.

This study shows prominent synchronous co-evolution of drought events in drought hubs in sub-tropical regions, influenced by sea surface temperature patterns and teleconnections. Such simultaneous occurrence of droughts may have detrimental impacts.

The authors show that robust analyses of high-impact compound weather and climate events require many samples. Thus, they argue that large ensemble climate model simulations should be used to provide the best available information on climate risks.

The performance of streamflow and groundwater drought forecasting depends on catchment properties, the number of months of precipitation accumulation, and drought propagation, but is reduced by river discharge and aquifer management, according to a modelling approach solely driven by precipitation data.

Heat extremes occur more frequently with global warming. Here the authors show that short-term heat extremes play a critical role in shaping long-term dynamics of lake surface temperature, contributing 36.5% of the warming trends in Chinese lakes.

The authors disentangle uncertainty in rainfall projections, revealing regions where multiple global climate models agree on future drying and wetting patterns with implications for one to two thirds of the world’s population.

Urban heat islands have the greatest acute impacts on human mortality risk during extreme heat. However, protracted cold seasons result in greater annually integrated protective effects in most European cities under the current climate.

Climate change effects on wildlife may occur through both gradual changes and extreme events. Here, the authors quantify the impact of cold snaps and heatwaves on reproductive success in 24 common bird species in North America over the last few decades.

Heat and moisture stress can reduce carbon uptake by forests. Here, the authors quantify this effect for the extreme 2022 European summer drought. The widespread reduction of photosynthesis exceeded the large local carbon release by intense fires.

The risk of heat-mortality is increasing sharply. The authors report that heat-mortality levels of a 1-in-100-year summer in the climate of 2000 can be expected once every ten to twenty years in the current climate and at least once in five years with 2 °C of global warming.

Storm severity indices of European winter storms in climate models show future increased storm losses in northwestern Europe, caused by changes in the location and intensity of storms, and increasing population.

The 2021 unprecedented Pacific Northwest heatwave broke temperature records by extraordinary amounts. Impacts included hundreds of deaths, mass-mortalities of marine life, increased wildfires, reduced crop and fruit yields, and river flooding.

Forest dynamics are monitored at large scales with remote sensing, but individual tree data are necessary for ground-truthing and mechanistic insights. This study on high temporal resolution dendrometer data across Europe reveals that the 2018 heatwave affected tree physiology and growth in unexpected way.

Flash droughts are projected to become more frequent under all global warming scenarios, with flash drought risk over croplands increasing particularly sharply over Europe and the US, according to analyses of climate model simulations.

Future drought impacts are expected to be highest in the Mediterranean, the Amazon, southern Africa and Central America, but exposure and socioeconomic risk could be reduced with sustainable development, suggests an analysis that integrates information on precipitation, runoff and soil moisture.

Ecosystem productivity losses associated with hydroclimatic extremes increased in northern mid-latitudes but decreased in pantropic regions between 1982 and 2016, according to an analysis of gross primary production data from observations and models.

Extreme ice sheet melt events in northeast Greenland occur after intense water vapor transport into northwest Greenland by atmospheric rivers. Through the foehn effect, the air becomes warmer and drier as it descends the ice sheet slope.