The climate crisis is driving heat waves and forest fires.  This is how

The climate crisis is driving heat waves and forest fires. This is how

In addition to rising temperatures above 40 Celsius (104 Fahrenheit), forest fires are raging across southern Europe with evacuations in cities in Italy and Greece.

The scorching heat is part of a global pattern of rising temperatures, which scientists attribute to human activity.

Climate change makes heat waves warmer and more frequent. This is the case for most land regions, and has been confirmed by the UN Global Panel on Climate Research (IPCC).

Greenhouse gas emissions from human activity have warmed the planet by around 1.2 Celsius since pre-industrial times. The warmer baseline means that higher temperatures can be reached during extreme heat events.

“Every heat wave like the one we are experiencing today has become warmer and more frequent due to climate change,” said Friederike Otto, a climate scientist at Imperial College London, who also heads the World Weather Attribution research collaboration.

But other conditions also affect heat waves. In Europe, atmospheric circulation is an important factor.

A study in the journal Nature this month found that heat waves in Europe have increased three to four times faster than in other northern latitudes such as the United States. The authors linked this to changes in the jet stream – a rapid west-to-east air flow in the northern hemisphere.

To find out exactly how much climate change affected a specific heat wave, researchers are conducting “attribution studies”. Since 2004, more than 400 such studies have been conducted for extreme weather events, including heat, floods and droughts – to calculate the role of climate change in each.

This means simulating the modern climate hundreds of times and comparing it to simulations of a climate without man-made greenhouse gas emissions.

For example, researchers with the World Weather Attribution determined that a record heat wave 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.

The heat waves will continue to get worse

Global warming is already leading to extreme heat events.

“On average on land, heat extremes that would have occurred once every 10 years without human impact on the climate are now three times more frequent,” said ETH Zurich climate scientist Sonia Seneviratne.

The amount of Greenland ice that melted last weekend can cover West Virginia in a foot of water

Temperatures will only stop rising if humans stop adding greenhouse gases to the atmosphere. Until then, the heat waves will worsen. Failure to cope with climate change will cause extreme heat to escalate even more dangerously.

Countries agreed under the 2015 global Paris agreement to cut emissions quickly enough to limit global warming to 2 ° C, and aim for 1.5 ° C, to avoid the most dangerous consequences. Current policy will not cut emissions fast enough to achieve any of the goals.

A heat wave that occurred once a decade in the pre-industrial era would occur 4.1 times a decade at 1.5 ° C with warming and 5.6 times at 2 ° C, says the IPCC.

Allowing warming to exceed 1.5 ° C means that most years “will be affected by hot extremes in the future,” Seneviratne said.

Climate change drives forest fires

Climate change is increasing heat and dry conditions that help fires spread faster, burn longer and rage more intensely.

In the Mediterranean, this has contributed to the fire season starting earlier and burning more land. Last year, more than half a million hectares burned in the EU, making it the block’s second worst forest fire season recorded after 2017.

Warmer weather also drains moisture from the vegetation, turning it into dry fuel that helps fires spread.

“The warmer and drier conditions right now, it just does [fires] far more dangerous, “said Copernicus senior researcher Mark Parrington.

Countries such as Portugal and Greece experience fires most summers, and have the infrastructure to try to deal with them – although both have received emergency aid from the EU this summer. But warmer temperatures also push forest fires into areas that are not used to them, and thus less prepared to cope.

Forest management and sources of ignition are also important factors. In Europe, more than nine out of ten fires are ignited by human activities, such as arson, disposable grills, power cords or lit glass, according to EU data. But the climate crisis usually creates conditions that make the effects of these fires much worse.

Countries, including Spain, face the challenge of shrinking the population in rural areas, as people move to cities, leaving smaller labor forces to clear vegetation and avoid “fuel” for forest fires that build up.

Some actions can help limit severe fires, such as setting up controlled fires that mimic low-intensity fires in natural ecosystem cycles, or introducing holes in forests to stop fires that spread rapidly over large areas.

But scientists agree that without sharp cuts in greenhouse gases that cause climate change, heat waves, forest fires, floods and droughts will worsen significantly.

“Looking back at the current fire season in a decade or two, it will probably seem mild in comparison,” said Victor Resco de Dios, a professor of forestry at Lleida University in Spain.

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