How climate change worsens heatwaves, droughts, wildfires and floods

Damaged vehicle is stuck debris after the floods caused by the Storm Daniel ravaged disaster zones in Derna, Libya on September 12, 2023
Parts of northern Libya have been hit by devastating flooding after extreme rainfall caused two dams to collapse

Extreme weather is becoming more frequent and more intense in many places around the world because of climate change.

Scientists say this will continue whilst humans keep releasing planet-warming greenhouse gases.

Here are four ways climate change is linked to extreme weather.

1. Hotter, longer heatwaves

Even a small increase to average temperatures makes a big difference.

This is because the whole distribution of daily temperatures shifts to warmer levels, making hotter days more likely and more extreme.

"A small shift makes a big difference". A line chart showing how small changes in the climate increases the probability of more hot weather and more extreme weather.

Scientists use computer simulations to assess whether extreme weather events have been made more likely by warming caused by humans.

For example, the intense heatwaves that hit southern Europe and the southern US and Mexico in July 2023 would have been "virtually impossible" without human-caused climate change, according to the World Weather Attribution network (WWA).

But these events are no longer rare. If global warming reaches 2C above the pre-industrial period - before humans started burning fossil fuels at scale - these events are expected to happen every 2-5 years, the WWA warns.

In the UK, temperatures topped 40C for the first time on record in July 2022. This would have been "extremely unlikely" without climate change, the WWA says.

As well as happening more frequently, heatwaves are becoming longer and more intense in many places, including the UK, where 2022 was the warmest year on record.

This can happen as a result of "heat domes" - an area of high pressure where hot air is pushed down and trapped in place, causing temperatures to soar over large areas.

One theory suggests higher temperatures in the Arctic - which has warmed more than four times faster than the global average - are causing strong winds called the jet stream to slow, increasing the likelihood of heat domes.

A graphic showing how heat domes are formed. 1) A mass of warm air builds up in still and dry summer conditions 2) High pressure in the atmosphere pressures the warm air down 3) The air is compressed and gets even hotter

2. Longer droughts

Linking climate change with specific individual droughts can be difficult. The availability of water depends on more than just temperature and rainfall.

But longer and more intense heatwaves can worsen droughts by drying out soils. This makes the air above warm up more quickly, leading to more intense heat.

Increased demand for water from humans and farmers in hot weather puts even more stress on the water supply.

In parts of East Africa, there were five failed rainy seasons in a row between 2020 and 2022, as the region suffered its worst drought for 40 years.

Climate change has made droughts like this at least 100 times more likely, according to the WWA.

A man walks in front of a sandstorm in Dollow, southwest Somalia. People from across Gedo in Somalia have been displaced due to drought. 14 April 2022.
The East African drought hit agriculture and food security hard, displacing nearly 1.2 million people in Somalia alone, according to the World Meteorological Organisation.

3. More fuel for wildfires

Fires happen naturally in many parts of the world. It's difficult to know if climate change has caused a specific wildfire to spread because other factors are also relevant, such as changing land use.

But climate change is making the weather conditions needed for wildfires to spread more likely, according to the UN's climate body, the IPCC.

Extreme and long-lasting heat draws more and more moisture out of the ground and vegetation.

These tinder-dry conditions provide fuel for fires, which can spread at an incredible speed, particularly if winds are strong.

Canada is experiencing its worst wildfire season on record, with 176,000 sq km (43.5 million acres) already burnt.

Climate change more than doubled the likelihood of the extreme "fire weather" conditions in eastern Canada that allowed the fires to spread, according to the WWA.

Bar chart showing area burned in Canada each year since 1983. In 2023, 17.6 million hectares has been burned already. No previous year had reached 8 million hectares.

There have also been severe wildfires in Greece, Chile and Australia in 2023.

Global fire trends are complicated because of the significance of changing land use, but many regions have seen increases in the area burnt by extreme wildfires in recent decades, including the western US and Canada.

Wildfires are projected to become more frequent and intense in future across the globe due to the the combined effects of shifting land use and climate change, according to a recent report by the UN Environment Programme.

It suggested that the number of the most extreme fires may increase by up to 50% by 2100.

4. More extreme rain

For every 1C rise in average temperature, the atmosphere can hold about 7% more moisture.

This can result in more droplets and heavier rainfall, sometimes in a shorter space of time and over a smaller area.

A chart showing how record temperatures cause extreme rainfall. 1) More heat from sun causes greater evaporation 2) More moisture forms clouds 3) Heavier rain

Recently, parts of northern Libya have been hit by devastating floods as a result of extreme rainfall and two major dam collapses. The heavy rainfall was made up to 50 times more likely by human-caused climate change, according to the WWA.

The destruction was exacerbated by social and political instability in the country, which hampered efforts to adequately prepare for and respond to such storms - for example dam maintenance.

Not all extreme rainfall events can be attributed to climate change, as other factors including changes to land use can play a role. For example, the WWA says that climate change only had a "limited" role in the heavy rainfall that hit northern Italy in May 2023.

But globally, the frequency and intensity of heavy rainfall events has increased over most land regions due to human activity, according to the IPCC.

And heavy precipitation will generally become more frequent and intense with further warming, the IPCC says.