Abstract
The Paris Agreement calls for global warming to be limited to 1.5–2 °C. For the first time, this study investigates how different regional heatwave characteristics (intensity, frequency and duration) are projected to change relative to increasing global warming thresholds. Increases in heatwave days between 4–34 extra days per season are projected per °C of global warming. Some tropical regions could experience up to 120 extra heatwave days/season if 5 °C is reached. Increases in heatwave intensity are generally 0.5–1.5 °C above a given global warming threshold, however are higher over the Mediterranean and Central Asian regions. Between warming thresholds of 1.5 °C and 2.5 °C, the return intervals of intense heatwaves reduce by 2–3 fold. Heatwave duration is projected to increase by 2–10 days/°C, with larger changes over lower latitudes. Analysis of two climate model ensembles indicate that variation in the rate of heatwave changes is dependent on physical differences between different climate models, however internal climate variability bears considerable influence on the expected range of regional heatwave changes per warming threshold. The results of this study reiterate the potential for disastrous consequences associated with regional heatwaves if global mean warming is not limited to 2 degrees.
Highlights
The Paris Agreement calls for global warming to be limited to 1.5–2 °C
Global climate models project that annual minimum temperatures over the Arctic will reach 5.5 °C warmer than the regional preindustrial climate[24], whereas annual maximum temperatures over much of the Northern Hemisphere, Central America and South Africa will be at least 3 °C warmer[24,25]
Over southern Australia and South America, a median of 4–8 extra heatwave days is expected for each degree of global warming
Summary
This study investigates how different regional heatwave characteristics (intensity, frequency and duration) are projected to change relative to increasing global warming thresholds. Some regions where intense heat is already common may become inhabitable 16, while tropical regions will experience extremely large increases in heatwave frequency due to low interannual variability[17,18]. Larger increases in temperature extremes are expected respective to 2 °C mean global warming, with considerable regional variation[24]. By 2 °C global warming, increases in annual maximum temperatures over 50% of land regions are expected to be almost 2 standard deviations (σ) warmer than pre-industrial conditions, with some tropical regions experiencing regular 3σ events[25]. Recent research suggests that soil moisture-temperature feedbacks further amplify increases in warm extremes, in addition to the effect of increasing global temperature[27]
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