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How climate change worsens heatwaves, droughts, wildfires and floods How climate change worsens heatwaves, droughts, wildfires and floods
(2 months later)
More than 70 million people in the US are under heat alerts this week, with extreme temperatures as high as 105F (41C) forecast in some areas. In many places around the world, extreme weather events are becoming stronger, and happening more often, due to climate change.
Scientists say many extreme weather events are becoming more frequent and intense as a result of climate change. This trend is likely to continue unless countries make steep cuts to emissions of the greenhouse gases - such as carbon dioxide - that are heating up the planet.
1. More extreme rain A simple guide to climate change
For every 1C rise in average temperature, the atmosphere can hold about 7% more moisture, external. A simple guide to climate change
This can result in more droplets and heavier rainfall, sometimes in a shorter space of time and over a smaller area. 1. Hotter, longer heatwaves
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, external.
It says this pattern will continue with further warming.
Scientists assess whether individual extreme weather events can be attributed to climate change by considering both natural and human causes, external.
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.
Heavy rain in this region is rare, which offers researchers 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.
In May 2024, southern Brazil experienced heavy rains which lead to widespread flooding, displacing about 150,000 people.
The Rio Grande do Sul region that was hit is particularly vulnerable to heavy rains, as it is the meeting point of tropical and polar air masses.
But climate expert Francisco Eliseu Aquino told the AFP news agency that "these interactions [have] intensified with climate change".
The mayor of Derna in northern Libya suggested as many as 20,000 may have been killed as a result of the flooding
The mayor of Derna in northern Libya suggested as many as 20,000 may have been killed as a result of the flooding
Scientists believe the heavy rainfall which caused deadly flooding in northern Libya in September 2023 was made up to 50 times more likely by climate change.
Years of political instability in the region also hampered preparations for such events.
2. Hotter, longer heatwaves
Even a small increase in average temperatures makes a big difference to heat extremes.Even a small increase in average temperatures makes a big difference to heat extremes.
As the range of daily temperatures shifts to warmer levels, hotter days are more likely and more intense. As the range of daily temperatures shifts to warmer levels, hotter days become more likely and more intense.
In April 2024, temperatures in Mali hit 48.5C during an extreme heatwave across the Sahel region of Africa, which was linked to increased hospitalisations and deaths. Scientists use computer models to simulate how individual extreme weather events unfold in two scenarios:
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. today's world with around 1.2C of human-caused warming
In the UK, temperatures topped 40C for the first time on record in July 2022, causing extensive disruption. This would have been extremely unlikely without climate change, the WWA says. today's world with around 1.2C of human-caused warming
Heatwaves are also becoming longer in many places, including the UK, external. a hypothetical world without human influence on the climate.
This can happen as a result of heat domes, external, which are areas of high pressure where hot air is pushed down and trapped, causing temperatures to soar over large areas. a hypothetical world without human influence on the climate.
One theory suggests that higher temperatures in the Arctic - which has warmed nearly four times faster than the global average, external - are causing strong winds called the jet stream to slow, increasing the likelihood of heat domes, external. That way, they can estimate, external how much a particular heatwave, drought or storm was affected by climate change.
A heat dome is expected to hit the western part of the US later this week - affecting more than 34 million residents across California, Nevada, Utah and Arizona. In April 2024, temperatures in Mali rose above 48C during an extreme heatwave across the Sahel region of Africa which was linked to increased hospitalisations and deaths.
Forecasters predict temperatures to be 5.5-11C (10-20F) above normal, potentially posing a risk to human health and the environment from resulting wildfires. This level of heat would not have been possible without human-caused climate change, according to scientists at the World Weather Attribution (WWA) group.
Such temperature spikes will become more common in many places, external as the world continues to warm.
In the UK, temperatures topped 40C for the first time on record in July 2022, causing extensive disruption. This would have been extremely unlikely without climate change, the WWA said.
Heatwaves can happen as a result of heat domes, external, which are created when an area of high pressure stays over the same area for days or weeks, trapping hot air underneath.
One theory suggests that higher temperatures in the Arctic - which has warmed nearly four times faster than the global average, external - are affecting the fast band of winds high in the atmosphere known as the jet stream, which could be making heat domes more likely.
Is the UK getting hotter?Is the UK getting hotter?
Is the UK getting hotter?Is the UK getting hotter?
Life at 50 degreesLife at 50 degrees
Life at 50 degreesLife at 50 degrees
2. More extreme rain
For every 1C rise in average temperature, the atmosphere can hold up to around 7% more moisture, external.
With more moisture available, rainfall can become heavier.
In September 2024, deadly floods hit much of central Europe, including Poland, the Czech Republic, Romania, Austria and Italy.
The intensity of the rainfall over four days in mid-September was made twice as likely by climate change, according to the WWA.
Between October 2023 and March 2024, the UK experienced the second-wettest such period on record. This level of rainfall was made at least four times as likely by human-caused warming, the WWA says.
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, external.
It says this pattern will continue with further warming.
3. Longer droughts3. Longer droughts
Linking climate change with specific individual droughts can be difficult. Linking climate change with specific individual droughts can be difficult, because there are lots of different factors that affect the availability of water.
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. Natural weather systems, for example, can play a key role, as 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. But climate change is shifting global rainfall patterns. While some of the world is getting wetter, other parts are becoming drier, which can make them more prone to drought.
And heatwaves fuelled by climate change can worsen dry conditions when they do occur, by increasing evaporation from the 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.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, external 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, external alone.In parts of East Africa, there were five failed rainy seasons, external 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, external alone.
Climate change has made droughts like this at least 100 times more likely, external, according to the WWA. Climate change has made droughts like this at least 100 times more likely, according to the WWA.
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. Human-caused warming was also the main driver of drought in the Amazon rainforest in the second half of 2023. This was the region's worst drought since modern records began.
4. More fuel for wildfires4. More fuel for wildfires
Fires happen naturally in many parts of the world, external. 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. Fires happen naturally in many parts of the world, external. It is difficult to know if climate change has caused or worsened a specific wildfire because other factors are also relevant, such as changes to the way land is used.
But climate change is making the weather conditions needed for wildfires to spread more likely, the IPCC says, external.But climate change is making the weather conditions needed for wildfires to spread more likely, the IPCC says, external.
Extreme, long-lasting heat draws more moisture out of soils and vegetation.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.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.Canada experienced by far its its worst wildfire season on record in 2023.
Canada experienced by far its worst wildfire year on record in 2023Canada experienced by far its worst wildfire year on record in 2023
Canada experienced by far its worst wildfire year on record in 2023Canada 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, external.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, external.
Rising temperatures may also increase the likelihood of lightning in the world's northernmost forests, triggering fires. Rising temperatures may also increase the likelihood of lightning in the world's northernmost forests, which can in turn trigger more fires.
The combined effects of shifting land use and climate change mean extreme wildfires are projected to become more frequent and intense in future, external globally, according to the UN Environment Programme (UNEP). The combined effects of shifting land use and climate change mean extreme wildfires are projected to become more frequent and intense globally, according to the UN Environment Programme (UNEP), external.
The number of the most extreme fires may rise by up to 50% by 2100, UNEP suggests.The number of the most extreme fires may rise by up to 50% by 2100, UNEP suggests.
How do wildfires start?How do wildfires start?
How do wildfires start?How do wildfires start?
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