Record heatwaves combined with severe drought are igniting fierce and frequent wildfires in North America and Europe. The intensity of these wildfires could make 2021 the worst wildfire season in history. Record-setting heat across southern Europe has sparked extreme wildfires in Turkey, Greece, Italy and Spain.

In the US this year, over 3.5 million acres have burned, already one million more than last year and fire season is far from over. Firefighters are battling multiple blazes across California where more than twice the amount of land has already burned this season compared to the five-year average.

The wildfires sweeping across the globe are not only wreaking local damage and sending choking smoke into the atmosphere, but they are also affecting the climate itself in important ways that will long outlast the flames. When trees get burned, carbon is released into the atmosphere. Wildfires release carbon that has been stored in forests for decades and can decrease the amount that forests can absorb until they can regenerate.

Scientists estimate that wildfires emitted about 8 billion tons of CO2 per year for the past 20 years. According to the NOAA, a very large, very hot fire destroying 500,000 acres could emit the same total amount to CO2 as six large coal-fired power plants in one year.

As wildfires become more frequent and intense, the carbon emissions they release exacerbates the progression of climate change, leading to a feedback loop—more warming leads to more fires, which release more carbon, which causes more warming.