3.2 Extreme weather events

The atmosphere reacts very rapidly to temperature rises over the land and sea. The extra heat turbo-charges the atmosphere, and excess heat and moisture is distributed around the globe. Unusual and extreme weather events are an early warning of such changes and are hard to ignore because of their damaging impacts. They damage ecosystems as well as our health and wellbeing, economies and infrastructure. In recent years, every region of the world has experienced impacts from record weather extremes: record temperatures and dangerous heatwaves, including marine heatwaves; sudden droughts; more intense storms and rainfall and damaging floods; and widespread wildfires in areas previously unaccustomed to them. For example, in 2023, high temperatures, low humidity and continuous winds caused extreme ‘megafires’ in Canada on an unprecedented scale, burning 18 million hectares of land – 10 million more than previous records (NASA, 2023; WWA, 2023)

Although the impacts of climate change are experienced across the world, some regions have experienced larger changes than others. Modelling shows that global warming will occur unevenly: the continents will heat up about twice as fast as the oceans, and polar regions will heat much faster than those near the equator. A global warming of 2 °C, for example, would mean that on average land surfaces would warm by 3 °C and the oceans by 1.5 °C, but more northern latitudes could warm by considerably more (WMO, 2023b). This is exactly what has been happening in recent decades. Figure 10 gives a snapshot of global warming for 2015–2019 (note that it uses a baseline of 1951–1980). Note in particular the extreme warming of the large land masses around the Arctic. By 2022, Europe had warmed by 2.3 °C above the 1850–1900 baseline – twice the global average rate – while parts of the Arctic warmed by three times the global average (WMO, 2023b).

Thus while temperatures are hottest near the equator, where higher temperatures and humidity can approach the limits of habitability of many species (including us), in more temperate climates the changes can be larger and ecosystems and societies may be less adapted to extreme heatwaves, for example. Heatwaves are becoming more frequent and more intense globally, and they now occur in temperate and boreal regions, such as Siberia, Alaska and Northern Canada, where they used to be unusual. This is also true for wildfires – particularly for forest fires in boreal regions, which have increased dramatically in intensity with rising temperatures.