BRUSSELS: Europe is once again battling scorching temperatures this summer, with wildfires blazing across the continent from the Mediterranean to Spain. 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 United Nations’ global panel of climate scientists, the Intergovernmental Panel on Climate Change (IPCC).
Greenhouse gas emissions from human activities have heated the planet by about 1.2 degrees Celsius since pre-industrial times. That warmer baseline means higher temperatures can be reached during extreme heat events.
Every heatwave being experienced today has been hotter and more frequent due to climate change, said Friederike Otto, a climate scientist at Imperial College London who co-leads the World Weather Attribution global research collaboration.
But other conditions affect heatwaves too. In Europe, atmospheric circulation is an important factor.
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 1.2 degrees Celsius 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, according to ETH Zurich climate scientist Sonia Seneviratne.
Temperatures will only stop 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 degrees Celsius and aim for 1.5 degrees Celsius, 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 degrees Celsius of warming, and 5.6 times at 2 degrees Celsius, the IPCC says.
Letting warming pass 1.5 degrees Celsius means that most years “will be affected by hot extremes in the future”, Seneviratne said.