Extreme heat, which is characterized primarily by how unusually hot or humid conditions are for a given area, is now occurring longer, more frequently and with greater intensity around the world. Unfortunately, it is all too often underestimated that heat waves are among the most dangerous natural disasters.
What are the negative impacts of heat waves?
From 2000 to 2019, there were approximately 489,000 heat-related deaths each year. The following areas of life are particularly at risk from extreme heat. These include:
- health systems
- emergency services
- water demand
- energy supply
- transport infrastructure
- power shortages
- blackouts
- crop losses
- livestock losses
- food security
- livelihoods
Understanding the mechanisms behind heatwaves
In summer, weather systems move more slowly, so there is a greater chance of long periods of high pressure. The jet stream weakens in summer, which is why weather systems move more slowly in the warmer months.
What are the consequences of high pressure?
The presence of high pressure at ground level leads to heatwaves forming. When high pressure builds up over an area, the air sinks through the atmosphere. This compresses and heats the air as it moves downwards.
High pressure can also bring about a heat dome, thereby intensifying the heatwave. A heat dome forms when a high-pressure system lingers over an area for several days, trapping warm air beneath it like a cap. This traps air that would otherwise rise and cool before returning to the surface, makes the air hotter and hotter and reduces the likelihood of rain.
Heat wave formation explained
Why are heatwaves increasing?
The occurrence of heatwaves has always been a natural part of normal weather variability. Nevertheless, their frequency and intensity are currently rising, primarily due to human-induced climate change. Now, one might argue that the increasing frequency of these heat waves is due to natural climate variability. Thanks to climate attribution science, we are able to determine the extent to which climate change has contributed to a specific extreme weather event, such as a heat wave.
How human-caused climate change intensifies heat waves
Higher global temperatures are now the new baseline
The Earth has warmed significantly since the 1950s due to greenhouse gas emissions, with the overall temperature distribution shifting upwards. What used to be an ‘extreme outlier’ is now much more frequent. Record temperatures are being broken more often. In addition to becoming more frequent, heat waves also begin at a higher temperature level.
Significantly higher likelihood of extreme heat
The statistics on heat events are subject to alteration due to climate change. Extreme heat now occurs many times more frequently. Events that used to be extremely rare, such as ‘once-in-a-century heat’, now happen much more frequently. Studies by World Weather Attribution consistently demonstrate this: Many current heatwaves would have been virtually impossible without climate change.
Heat waves on land are made more intense by warmer oceans
The oceans store a large amount of excess heat. Warmer air is caused by higher ocean temperatures. Warm air masses move over continents, and as they do so, they cause changes in temperature and humidity levels. The oceans are losing their cooling effects.
Climate change is intensifying droughts, and thus extreme heat
Human-induced climate change is changing the water cycle. Precipitation patterns are shifting. Drying out is becoming a more regular occurrence in relation to soils. The process of cooling via evaporation is being lost. The creation of a feedback loop is the result.
Climate change is messing with the big jet streams out there
The decrease in the temperature difference between the pole and mid-latitudes is a result of the rapid warming of the Arctic (Arctic amplification). The jet stream becomes sluggish. It also becomes more unstable. The result is the stalling of weather patterns and the lengthier duration of heat over a region.
Extreme heat podcast episodes
Totally Cooked Podcast
How is climate change impacting our weather?
Description excerpt: How is climate change impacting our weather? As the planet gets warmer, we’re entering uncharted territory for the climate and weather. We’re already seeing temperature …
The podcast episode details how climate change is altering global weather patterns, making extreme weather events, like heatwaves, more likely.
The Climate Conversation Podcast
Hot Today, Hotter Tomorrow: Policy Solutions to the Dangers of Extreme Heat
Description excerpt: Extreme heat is the silent killer out of all climate-related disasters. …
References
[1] Climate change and heatwaves. (2023, September 27). World Meteorological Organization. https://wmo.int/content/climate-change-and-heatwaves
[2] Contributor, G. (2022, August 11). Geo explainer: What causes heatwaves? Geographical. https://geographical.co.uk/science-environment/geo-explainer-what-causes-heatwaves