California wildfire

The year the West was burning: How the 2020 wildfire season got so extreme

If 2020 has proved anything, it is to expect the unexpected.

More than 4 million acres of California went up in flames in 2020 – about 4 percent of the state's land area and more than double its previous wildfire record.


Five of the state's six largest fires on record were burning this year.

In Colorado, the Pine Gulch fire broke the record for that state's largest wildfire, only to be surpassed by two larger blazes, the Cameron Peak and East Troublesome fires.

Oregon saw one of the most destructive fire seasons in its recorded history, with more than 4,000 homes destroyed.

What caused the 2020 fire season to become so extreme?

Fires thrive on three elements: heat, dryness and wind. The 2020 season was dry, but the Western U.S. has seen worse droughts in the recent decade. It had several record-breaking heat waves, but the fires did not necessarily follow the locations with the highest temperatures.

What 2020 did have was heat and dryness hitting simultaneously. When even a moderate drought and heat wave hit a region at the same time, along with wind to fan the flames, it becomes a powerful force that can fuel megafires.

That's what we've been seeing in California, Colorado and Oregon this year. Research shows it's happening more often with higher intensity, and affecting ever-increasing areas.

Climate change intensified dry-hot extremes

We are scientistsandengineers who study climate extremes, including wildfires. Our research shows that the probability of a drought and heat wave occurring at the same time in the U.S. has increased significantly over the past century.

The kind of dry and hot conditions that would have been expected to occur only once every 25 years on average have occurred five to 10 times in several regions of the U.S. over the past quarter-century. Even more alarming, we found that extreme dry-hot conditions that would have been expected only once every 75 years have occurred three to six times in many areas over the same period.

We also found that what triggers these simultaneous extremes appears to be changing.

During the Dust Bowl of the 1930s, the lack of rainfall allowed the air to become hotter, and that process fueled simultaneous dry and hot conditions. Today, excess heat is a larger driver of dry-hot conditions than lack of rain.

This has important implications for the future of dry-hot extremes.

Warmer air can hold more moisture, so as global temperatures rise, evaporation can suck more water from plants and soil, leading to drier conditions. Higher temperatures and drier conditions mean vegetation is more combustible. A study in 2016 calculated that the excess heat from human-caused climate change was responsible for nearly doubling the amount of Western U.S. forest that burned between 1979 and 2015.

Worryingly, we have also found that these dry-hot wildfire-fueling conditions can feed on one another and spread downwind.

When soil moisture is low, more solar radiation will turn into sensible heat – heat you can feel. That heat evaporates more water and further dries the environment. This cycle continues until a large-scale weather pattern breaks it. The heat can also trigger the same feedback loop in a neighboring region, extending the dry-hot conditions and raising the probability of dry-hot extremes across broad stretches of the country.

All of this translates into higher wildfire risk for the Western U.S.

In Southern California, for example, we found that the number of dry-hot-windy days has increased at a greater rate than dry, hot or windy days individually over the past four decades, tripling the number of megafire danger days in the region.

The U.S. Drought Monitor is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration. (Credit: NDMC)

2020 wasn’t normal, but what is normal?

If 2020 has proved anything, it is to expect the unexpected.

Before this year, Colorado had not recorded a fire of over 10,000 acres starting in October. This year, the East Troublesome fire grew from about 20,000 acres to over 100,000 acres in less than 24 hours on Oct. 21, and it was nearly 200,000 acres by the time a snowstorm stopped its advance. Instead of going skiing, hundreds of Coloradans evacuated their homes and nervously watched whether that fire would merge with another giant blaze.

This is not "the new normal" – it's the new abnormal. In a warming climate, looking at what happened in the past no longer offers a sense of what to expect in the future.

"The growth that you see on this fire is unheard of," Grand County Sheriff Brett Schroetlin said of the East Troublesome fire on Oct. 22. "We plan for the worst. This is the worst of the worst of the worst."

Credit: Alizadeh, et al, Science Advances 2020

There are other drivers of the rise in fire damage, as well. More people moving into wildland areas means there are more cars and power lines and other potential ignition sources. Historical efforts to control fires have also meant more undergrowth in areas that would have naturally burned periodically in smaller fires.

The question now is how to manage this "new abnormal" in the face of a warming climate.

In the U.S., one in three houses are built in the wildland-urban interface. Development plans, construction techniques and building codes can do more to account for wildfire risks, including avoiding flammable materials and potential sources of sparks. Importantly, citizens and policymakers need to tackle the problem at its root: That includes cutting the greenhouse gas emissions that are warming the planet.

Mojtaba Sadegh is an assistant professor of Civil Engineering at Boise State University; Ata Akbari Asanjan is a research scientist at the Ames Research Center, NASA; Mohammad Reza Alizadeh is a Ph.D. student at McGill University.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Banner photo: California National Guard fighting a wildfire in September. (Credit: The National Guard/flickr)

Brandon Moffatt: Climate Action 2.0 starts with certainty and access to capital green economy leaders

Climate Action 2.0 means acknowledging Canada is now in a competition with other advanced nations that are building their own foundations to attract the top talent of the green economy.

Senator Whitehouse & climate change

Senator Whitehouse puts climate change on budget committee’s agenda

For more than a decade, Senator Sheldon Whitehouse gave daily warnings about the mounting threat of climate change. Now he has a powerful new perch.

NY finalizes list of ‘disadvantaged communities’ first in line for climate change funds

New York State has finalized the list of so-called “disadvantaged communities” to be targeted for extra funding and cleanup in the state’s ambitious multibillion-dollar climate plan.

California's big melt is set to revive a lost Tulare Lake

California's blockbuster wet season, with another powerful bomb cyclone currently swirling off the coast, has built up a near-record-large Sierra Nevada mountain snowpack.

How daylight saving time could help fight climate change

Setting clocks forward was introduced to reduce the need for artificial lighting, but it turns out to reduce the need for air conditioning as well.

Proposed coal mines a climate disaster, experts warn

Experts warn that approving proposed coal mines across the country would cause almost 18 billion tonnes of greenhouse gas pollution to be emitted.

Cop28 host UAE tries to weaken global shipping's climate ambition

Campaigners said the UAE’s opposition to zero emissions by 2050 was “alarming” given the country will host Cop28 climate talks in December.

In small-town Colorado, gas interests fight electrification

Local communities like Gunnison want to electrify, but national natural gas providers are redirecting proposed polices.
From our Newsroom
oil and gas wells pollution

What happens if the largest owner of oil and gas wells in the US goes bankrupt?

Diversified Energy’s liabilities exceed its assets, according to a new report, sparking concerns about whether taxpayers will wind up paying to plug its 70,000 wells.

Paul Ehrlich

Paul Ehrlich: A journey through science and politics

In his new book, the famous scientist reflects on an unparalleled career on our fascinating, ever-changing planet.

oil and gas california environmental justice

Will California’s new oil and gas laws protect people from toxic pollution?

California will soon have the largest oil drilling setbacks in the U.S. Experts say other states can learn from this move.

popular stories 2022

Our 5 most popular reads from 2022

A corpse, woodworking dangers, plastic titans ... revisit the stories that stuck with our readers this past year.

Stay informed: sign up for The Daily Climate newsletter
Top news on climate impacts, solutions, politics, drivers. Delivered to your inbox week days.