A MAFFS-equipped Air National Guard C-130 Hercules drops fire retardant on wildfires in southern California. Credit: Wikimedia Commons

In some parts of the Western United states, its 2 to 2.5 degrees F warmer in the forest at summer compared to 1950. This has led to longer, harsher dry spells that make forests vulnerable to fire. A new study made by researchers at the University of Idaho and Columbia University confirmed what we knew all along: forest fires have intensified in the past three decades in the western part of the continent. What the researchers brought new to the table is a quantitative analysis of global warming’s contribution to this woodland purge.

“Anthropogenic climate change has emerged as a driver of increased forest fire activity,” the report says.

“We know that our fire season is getting longer,” Idaho Forester David Groeschl, who was not involved in the research. “We know that we’re seeing more and longer fires, and we know that we have increasing fuels out there as well.”

Groeschl is referring to what experts call “fuel aridity”, a measure of dryness that leads to these massive blazes. The researchers found 55 percent of the “fuel aridity” measured between from 1979 to 2015 can be put on the shoulders of global warming, while the rest of 45 percent is due to natural variability.

9 of the worst 10 years for acres burned have occurred since 2000

From 1984 to 2015, Western forests lost 16,000 square miles because of global warming or roughly half of all the burned woodlands.

The effect of increased fuel is self-evident. Last year, for instance, was a record year for wildfires in the U.S. with over 10 million acres burned. The first quarter of this year was also off the charts as wildfires burned through 1.3 million acres of forest — that’s double the average for that time.

Things are expected to get only worse as the CO2 levels increase in the atmosphere, driving more warming. Its effects aren’t linear, but exponential. In other words, the next degree of warming should cause more additional damage than the degree before it.

This pattern is expected to continue until there’s simply no more fuel to burn. Roughly by the middle of this century, scientists expect fewer wildfires but only because there will be so few trees left.

The findings published in PNAS serve as a wake-up call for policymakers, some who are still oddly debating whether climate change is happening or if humans cause it or not. We need to act now before wildfires, droughts, and extreme weather becomes the new norm.