Here AFP looks at how climate change produces extreme heat, how scientists evaluate heatwaves and the risks to human health:
What is extreme heat?
Extreme heat is defined from a baseline of the average temperature in any one location, which varies widely across the world.
So a temperature of 25 degrees Celsius (77 degrees Fahrenheit) could be record-breaking in parts of Canada in spring, but might be below average for the same period in the Middle East.
What role does climate change play?
"Greenhouse gases trapping heat are at the root of the problem," said Martin Jucker, a lecturer at the University of New South Wales' Climate Change Research Centre.
Gases like carbon dioxide, methane and nitrous oxide play a crucial role in stopping heat from being reflected or lost from our atmosphere.
When this process is balanced, it keeps the planet at a livable temperature.
But an unsustainable increase in the amount of greenhouse gases in the atmosphere means more heat is being trapped, creating an overall global warming effect and other climate anomalies.
For example, warming air holds more moisture, which produces stronger and more frequent storms.
Overall, climate change is strengthening the duration, intensity and geographical reach of heatwaves, scientists say.
What about human interventions?
The problem is made worse in some places by the way cities are built -- the so-called heat island effect, where urban conglomerations are warmer than surrounding rural areas.
This happens because cities with too little greenery and too much concrete, asphalt and other building materials absorb heat and often offer insufficient shade.
The use of cooling technologies like air conditioners creates surging demand for energy, including the fossil fuels that are behind the climate crisis in the first place.
Are all heatwaves linked to climate change?
To determine climate change's role in any given event, experts use a technique called attribution science.
They simulate a world with and without climate change, using historical and more recent measurements, or computer models.
Comparing the two then "gives us a measure of how much more likely a given extreme is under climate change", Jucker told AFP.
Findings for over 500 events have been collected by the organisation Carbon Brief, with most shown to have been made more severe or more likely because of climate change.
Just a handful, including some floods, droughts and extreme cold, have been found to have no clear link to human activity, while in other cases experts found the evidence inconclusive.
"Every heatwave in the world is now made stronger and more likely to happen because of human-caused climate change," according to Friederike Otto, a scientist at Imperial College London and pioneer of attribution methodology.
How does extreme heat affect people?
Exposure to higher-than-normal temperatures produces health problems ranging from heatstroke and dehydration to cardiovascular stress.
Those with pre-existing heart conditions are especially vulnerable, as the body's response to heat is to pump more blood to the skin to help with cooling.
Risk is also unevenly distributed, with the elderly and the unwell more vulnerable, and those who work outdoors or live in places without air conditioning more likely to suffer.
The deadliest heat combines soaring temperatures with high humidity -- the moist air undermines the body's ability to cool off by sweating.
In May, a study warned a fifth of the world's population would be exposed to extreme and potentially life-threatening heat by the end of the century on our current climate track.
"For every 0.1C of warming above present levels, about 140 million more people will be exposed to dangerous heat," the study published in Nature Sustainability warned.
Greta Thunberg backs climate group shut down by France
Paris (AFP) June 21, 2023 -
Swedish climate activist Greta Thunberg on Wednesday gave her backing to a climate group shut down by the French government amid accusations it foments violence.
The government issued a decree earlier on Wednesday outlawing Uprisings of the Earth (SLT), saying it had encouraged violence in a series of demonstrations, including one that saw fierce clashes with police over an irrigation project.
SLT condemned the shutdown and called for protests in dozens of cities across France starting Wednesday.
The group also won the swift backing of Thunberg who was in Paris on the sidelines of a summit on green finance.
"This is about the right to protest and this is about defending life," Thunberg told a news conference with members of the organisation and supporters.
"I hope there'll be more people who stand up against these things that are happening now, and stand up for the right to protest," said the 20-year-old who regularly calls on world leaders to act fast against climate change.
Following Wednesday's weekly cabinet meeting, Interior Minister Gerald Darmanin said that "under the claim of defending the preservation of the environment... (SLT) encourages sabotage and property damage, including with violence".
SLT is part of a new wave of more radical climate activist groups, including Extinction Rebellion, that say direct action is needed in response to insufficient efforts to combat climate change and global warming.
The dissolution procedure for SLT was launched in March after around 5,000 protesters battled with more than 3,000 police officers during a protest against a giant irrigation reservoir near Sainte-Soline in western France.
Two protesters were left in a coma afterwards and about 30 officers were injured.
But Darmanin has drawn fire from left-wing opponents and rights groups for branding the actions of some protesters "eco-terrorism", noting that SLT's dissolution is based on a new law targeting extremist ideologies.
"It should not be used in a context of civil disobedience, where the freedom of expression and assembly takes precedence," Greenpeace France said in a statement.
Greenpeace added that it would support SLT if it contested the dissolution decree before the State Council, which rules on the legality of French laws.
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