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Image source, Reuters
By Mark Poynting and Esme Stallard
BBC News Climate & Science
Climate change is the most likely explanation for why Dubai has been experiencing increasingly heavy rainfall events, a new study says.
Here are four ways that climate change is linked to extreme weather.
1. 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.
Scientists assess whether individual extreme weather events can be attributed to climate change by taking account of natural and human causes.
In the case of the intense rainfall which fell in Dubai, the United Arab Emirates (UAE) and Oman in April 2024, it was difficult to conclude exactly how much of a role climate change played. That's because heavy rain in this region is rare, giving scientists fewer historical comparisons.
But these types of events have become 10-40% heavier, and climate change is the most likely explanation, according to the World Weather Attribution (WWA) group.
It's too early to say exactly what role climate change played in that event. But heavy rainfall in the same region in October and November 2023 was worsened by a combination of climate change and a natural weather phenomenon known as the Indian Ocean Dipole, the WWA found.
Image source, AFP
Image caption,The mayor of Derna in northern Libya suggested as many as 20,000 may have been killed as a result of the flooding
Globally, heavy rainfall events have become more frequent and intense over most land regions due to human activity, according to the UN's climate body, the IPCC.
This pattern will continue with further warming, the IPCC says.
2. Hotter, longer heatwaves
Even a small increase to average temperatures makes a big difference to heat extremes.
The distribution of daily temperatures shifts to warmer levels, making hotter days more likely and more intense.
In early April 2024, temperatures in Mali hit 48.5C during an extreme heatwave across the Sahel region of Africa, which has been linked to increased hospitalisations and deaths.
This level of heat would not have been possible without human-caused climate change, the WWA found, and will become more common as the world continues to warm.
In the UK, temperatures topped 40C for the first time on record in July 2022, causing extensive disruption across the country. This would have been extremely unlikely without climate change, the WWA says.
Heatwaves are also becoming longer in many places, including the UK.
This can happen as a result of heat domes, which are areas of high pressure where hot air is pushed down and trapped, causing temperatures to soar over large areas.
3. Longer droughts
Linking climate change with specific individual droughts can be difficult.
The availability of water depends on more than just temperature and rainfall, with natural weather systems also playing a key role. This was the case with drought in southern Africa in early 2024.
But heatwaves fuelled by climate change can worsen droughts by drying out soil. This makes the air above warm up more quickly, leading to more intense heat.
During periods of hot weather, increased demand for water, especially from farmers, 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. This displaced 1.2 million people in Somalia alone.
Climate change has made droughts like this at least 100 times more likely, according to the WWA.
And human-caused warming was also the main driver of the Amazon rainforest's worst drought in at least half a century in the second half of 2023.
4. More fuel for wildfires
Fires happen naturally in many parts of the world. It's difficult to know if climate change has caused or worsened a specific wildfire 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, the IPCC says.
Extreme, long-lasting heat draws more moisture out of soils and vegetation.
These tinder-dry conditions provide fuel for fires, which can spread at an incredible speed, particularly if winds are strong.
Canada experienced by far its its worst wildfire season on record in 2023.
Image source, Reuters
Image caption,Canada experienced by far its worst wildfire year on record in 2023
Climate change more than doubled the likelihood of the extreme "fire weather" conditions in eastern Canada in May and June 2023, which helped fires to spread, the WWA says.
Rising temperatures may also increase the likelihood of lightning in the world's northernmost forests, triggering fires.
Extreme wildfires are projected to become more frequent and intense in future globally, according to the UN Environment Programme (UNEP). This is due to the the combined effects of shifting land use and climate change.
The number of the most extreme fires may rise by up to 50% by 2100, UNEP suggests.
