Europe is in the grip of a record-breaking heatwave and wildfires are raging across the Mediterranean. Here’s how climate change drives these events.
Hotter, more frequent heatwaves
Climate change makes heatwaves hotter and more frequent. This is the case for most land regions, and has been confirmed by the UN’s global panel of climate scientists (IPCC).
Greenhouse gas emissions from human activities have heated the planet by about 1.2 Celsius since pre-industrial times. That warmer baseline means higher temperatures can be reached during extreme heat events.
“Every heatwave that what we are experiencing today has been made hotter and more frequent because of climate change,” said Friederike Otto, a climate scientist at Imperial College London who also co-leads the World Weather Attribution research collaboration.
But other conditions affect heatwaves too. In Europe, atmospheric circulation is an important factor.
A study in the journal Nature this month found that heatwaves in Europe have increased three-to-four times faster than in other northern mid-latitudes such as the United States. The authors linked this to changes in the jet stream — a fast west-to-east air current in the northern hemisphere.
Fingerprints of climate change
To find out exactly how much climate change affected a specific heatwave, scientists conduct “attribution studies”. Since 2004, more than 400 such studies have been done for extreme weather events, including heat, floods and drought — calculating how much of a role climate change played in each.
This involves simulating the modern climate hundreds of times and comparing it to simulations of a climate without human-caused greenhouse gas emissions.
For example, scientists with World Weather Attribution determined that a record-breaking heatwave in western Europe in June 2019 was 100 times more likely to occur now in France and the Netherlands than if humans had not changed the climate.
Heatwaves will still get worse
The global average temperature is around 1.2C warmer than in pre-industrial times. That is already driving extreme heat events.
“On average on land, heat extremes that would have happened once every 10 years without human influence on the climate are now three times more frequent,” said ETH Zurich climate scientist Sonia Seneviratne.
Temperatures will only cease rising if humans stop adding greenhouse gases to the atmosphere. Until then, heatwaves are set to worsen. A failure to tackle climate change would see heat extremes escalate even more dangerously.
Countries agreed under the global 2015 Paris Agreement to cut emissions fast enough to limit global warming to 2°C and aim for 1.5°C, to avoid its most dangerous impacts. Current policies would not cut emissions fast enough to meet either goal.
A heatwave that occurred once per decade in the pre-industrial era would happen 4.1 times a decade at 1.5°C of warming, and 5.6 times at 2°C, the IPCC says.
Letting warming pass 1.5°C means that most years “will be affected by hot extremes in the future,” Seneviratne said.
Climate change drives wildfires
Climate change increases hot and dry conditions that help fires spread faster, burn longer and rage more intensely.
In the Mediterranean, that has contributed to the fire season starting earlier and burning more land. Last year more than half a million hectares burned in the European Union, making it the bloc’s second-worst forest fire season on record after 2017.
Hotter weather also saps moisture from vegetation, turning it into dry fuel that helps fires to spread.
“The hotter, drier conditions right now, it just makes far more dangerous,” Copernicus senior scientist Mark Parrington said.
Countries such as Portugal and Greece experience fires most summers, and have infrastructure to try to manage them — though both have received emergency EU help this summer. But hotter temperatures are also pushing wildfires into regions not used to them, and thus less prepared to cope.
Climate change isn’t the only factor in fires
Forest management and ignition sources are also important factors. In Europe, more than nine out of 10 fires are ignited by human activities, like arson, disposable barbeques, electricity lines, or littered glass, according to EU data.
Countries, including Spain, face the challenge of shrinking populations in rural areas, as people move to cities, leaving smaller workforces to clear vegetation and avoid “fuel” for forest fires building up.
Some actions can help to limit severe blazes, such as setting controlled fires that mimic the low-intensity fires in natural ecosystem cycles, or introducing gaps within forests to stop blazes rapidly spreading over large areas.
But scientists concur that without steep cuts to the greenhouse gases causing climate change, heatwaves, wildfires, flooding and drought will significantly worsen.
“When we look back on the
current fire season in one or two decades’ time, it will probably seem mild by comparison,” said Victor Resco de Dios, professor of forest engineering at Spain’s Lleida University. — Reuters
A firefighting plane drops flame retardant to extinguish a fire in Guillos also in the Gironde region of southwestern France. (Reuters)
Health risks of extreme heat
What are the risks?
Heat affects health in a number of ways.
Heat exhaustion, which can include dizziness, headaches, shaking and thirst, can affect anyone, and is not usually serious, providing the person cools down within 30 minutes.
The more serious version is heatstroke, when the body’s core temperature goes above 40.6 degrees Celsius (105 degrees Fahrenheit). It is a medical emergency and can lead to long-term organ damage and death. Symptoms include rapid breathing, confusion or seizures, and nausea.
Who is at risk
Some people are more vulnerable, including young babies and older people, as well as people who have to stay active or are more exposed, such as homeless people.
Existing conditions, including respiratory and cardiovascular diseases, as well as diabetes, can also heighten risk — and be exacerbated by heat.
“When you see a hot day such as today, there is likely to be a spike in mortality in all of these disease groups,” said Shakoor Hajat, an environmental epidemiologist at the London School of Hygiene and Tropical Medicine.
Globally, just under half a million deaths a year are estimated to be due to excess heat, according to a study last year in The Lancet, although data is lacking from many low-income countries. Far more die of cold, but that is forecast to change, the researchers said.
Less obvious risks
Air pollution also increases during heatwaves, the World Meteorological Association warned last week, with adverse health affects.
Heat also can lead to low birth weight and premature birth for pregnant women and babies, a number of studies have shown.
There are less obvious risks, too. Lawrence Wainwright, an environment lecturer at the University of Oxford, said suicide rates and mental health problems often rise during heatwaves.
Scientists said that there was no evidence yet of any impact on Covid-19 or long Covid patients.
Experts say more deaths occur earlier in the summer, when people’s bodies have not had chance to acclimatise.
Location matters, too; people are at higher risk in places where they are not used to such heat, including in parts of Europe.
However, there are limits, and people all around the world are at risk in extremely hot weather caused by climate change, particularly people who have to continue to work in physical jobs, for example.
“In all of the places I’ve seen in the world that we have data, there’s an increase in mortality risk when people are exposed to high temperatures,” said Eunice Lo, a climate scientist at the University of Bristol, in western England.
What you can do
A number of European public health agencies have issued advice on keeping cool, including avoiding exertion where possible and staying hydrated.
Heatstroke is a medical emergency and requires immediate medical attention.
They also advise checking in on the vulnerable. In the European heatwave in 2003, when more than 20,000 people are thought to have died, many of them were older and isolated.
Last updated: July 21 2022 11:13 PM
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