Global temperature extremes
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Global Trends in Temperature Extremes
Research shows that both the frequency and duration of global temperature extremes—extreme heat events (EHE) and extreme cold events (ECE)—have changed significantly over recent decades. There is a clear pattern of increased warm extremes and decreased cold extremes across most regions, with strong seasonal and spatial variations. For example, high frequencies and durations of EHE are observed in the Antarctic during its summer and winter, and in the Arctic Ocean during the boreal winter. Conversely, high ECE frequencies are found in the Nearctic and Palearctic during the boreal winter and in the Arctic Ocean during the boreal summer. These trends are especially pronounced in terrestrial environments and show strong seasonal variation, with positive trends in EHE duration particularly notable in marine environments during summer months in both hemispheres. These changes present significant challenges for both human and natural systems as climate change progresses .
Acceleration and Regional Patterns of Extreme Heat
The highest annual temperatures have increased globally at a rate of 0.19°C per decade over the past 50 years, accelerating to 0.25°C per decade in the last 30 years. This rate of increase is faster than that of mean annual temperatures. Regions such as Eurasia and Australia have experienced even higher rates, exceeding 0.60°C per decade. In large cities, where heat-related health risks are greatest, the average increase is 0.33°C per decade, with some cities experiencing even more rapid warming . The year 2023 and early 2024 saw unprecedented global temperature records, with every month from June 2023 to June 2024 setting new highs. The annual average for 2023 approached 1.5°C above pre-industrial levels, driven by both long-term warming and natural variability, such as El Niño events .
Observed Changes in Daily Temperature Extremes
Analysis of daily temperature data from 1951 to 2003 reveals a significant decrease in cold nights and a significant increase in warm nights across more than 70% of the global land area. Some regions have seen more than a doubling of these indices, indicating a positive shift in daily minimum temperatures. Daily maximum temperature extremes have also increased, though to a lesser extent. These changes are consistent across all seasons, though they are least pronounced from September to November .
Temperature Extremes During the Global Warming Slowdown
Even during periods when the rise in global mean temperatures slowed, such as the so-called "global warming hiatus" after the late 1990s, both summertime warm and wintertime cold extremes increased over land. The increase in cold extremes was linked to specific atmospheric circulation patterns, while the rise in warm extremes was associated with sea surface temperature patterns. This highlights that the factors driving temperature extremes can differ from those influencing global mean temperatures .
Future Projections of Global Temperature Extremes
Projections using advanced machine learning models indicate that global temperature extremes will increase substantially under high-emission scenarios. Regions such as Greenland, the Tibetan Plateau, and the Arctic Archipelago are identified as future hotspots for temperature extremes. These findings underscore the urgent need for strong emission reduction commitments to mitigate the risks associated with more frequent and intense temperature extremes .
Predictability and Risk Reduction for Temperature Extremes
Many regions, especially in the extratropics and tropics, show both strong seasonality and short-term predictability for heatwaves and coldwaves. Nearly 5 billion people live in areas where early warning systems and seasonal preparedness plans could effectively reduce risks from temperature extremes .
Impact of Warming Limits on Extreme Event Risks
Limiting global warming to 1.5°C instead of 2.0°C would significantly reduce the probability and intensity of extreme temperature events. For example, the probability of a warm extreme that currently occurs once every 20 years is projected to increase by 130% at 1.5°C warming and by 340% at 2.0°C. The relative increase is even greater for rarer, more extreme events, emphasizing the importance of ambitious climate targets . In sensitive regions like the Arctic, Antarctica, and the Tibetan Plateau, limiting warming to 1.5°C could reduce the intensification of temperature extremes by up to 66% compared to a 2.0°C scenario .
Comprehensive Metrics for Global Warming and Extremes
Surface equivalent potential temperature, which combines air temperature and humidity, provides a more complete picture of global warming and its impact on weather extremes than air temperature alone. From 1980 to 2019, this metric increased nearly twice as much as surface air temperature, especially in the tropics. Projections suggest that, without emission reductions, the frequency of heat extremes could increase 14- to 30-fold by 2100, with corresponding increases in extreme precipitation and deep convection .
Conclusion
Global temperature extremes are increasing in frequency, duration, and intensity, with the most rapid changes occurring in recent decades and under high-emission scenarios. These changes are evident across both land and marine environments, with significant regional and seasonal variations. Limiting global warming to lower thresholds, improving early warning systems, and using comprehensive metrics are essential strategies for reducing the risks and impacts of temperature extremes on societies and ecosystems worldwide 1234+6 MORE.
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