Climate change amplifies threat of wildfires

Climate change creates ideal settings for fire, amplifying the threat  Warmer temperatures and drier conditions increase the chances of a fire starting and encourage it to spread. These conditions also contribute to the spread of the mountain pine beetle and other insects that can weaken or kill trees, building up the fuels in a forest. Climate change may also alter storm patterns, directly affecting the number of lightning-caused fires. Wildfires have significant impacts on human health and the economy, especially in the California and the western U.S.

Higher temperatures lead to more frequent droughts and longer wildfire seasons 

Wildfire season has gotten almost 20 percent longer over the past 35 years worldwide as a result of rising global temperatures and fewer rainy days. While fire risks are projected to increase globally, temperate forests in North America are among the regions most threatened by wildfires. In the U.S., climate change has led to fire seasons that are now 78 days longer on average compared to 1970. Nine of the 10 years with the largest acreage burned occurred since the year 2000—coinciding with many of the warmest years on record—and the six worst fire seasons since 1960 have also occurred since 2000. Over the next 25 years, the U.S. National Climate Assessment predicts the area burned by wildfires will double nationwide as global warming leads to higher temperatures, longer wildfire seasons and more frequent droughts. By the end of the century, models project that burned area in North America could increase 2 to 5.5 times.

Wildfires are a danger to health and incredibly costly

Wildfires are costly for governments to control and are dangerous to human health. The impacts of wildfire on human health are very solidly documented, with the increase in wildfire frequency worsening air quality and harmful health effects, according to the U.S. National Climate Assessment.

Wildfire costs are also increasing fast. U.S. wildfires have seen significant growth both in terms of acreage burned and in financial costs to property owners and communities. The 2015 fire season set a new record as the earliest the number of national acres burned reached more than 7 million. The U.S. Forest Service spent more than half its budget in 2015 preparing for and fighting fires, compared to just 16 percent in 1995. Average annual fire suppression costs increased to $3 billion from $1 billion in the 1990s. By the early 2000s, the area burned each year doubled from 3.6 million acres to 6.5 million. A report places the average annual burned area in the U.S. between 7 and 9 million acres.

Western states face the greatest threat

California fires in 2015 were extremely volatile and spread rapidly due to ongoing drought and heat throughout the state. In 2014, California burned through its $209 million annual wildfire-fighting budget in the first three months of its fiscal year and was forced to tap into a reserve account for $70 million in additional funding. In 2013, the wildfires during the summer were extremely intense for some areas, especially the Rim Fire near Yosemite National Park that burned over a quarter of a million acres of forest. The Rim Fire was among the top three largest wildfires in California’s history, and is emblematic of this sort of increasingly common mega-fire. These examples are only some of the latest in an emerging trend. By one estimate, $4 billion was spent combating wildfires in California from 2003-2012, more than in any other state.

In Oregon and Washington, which have experienced record fire seasons in recent years, research shows a link between wildfire activity and climate change. According to the research, minimum temperature, average maximum temperature, and average dewpoint increased significantly after the 1990s, corresponding to “a significant increase in total hectares burned for the same time period.”

In 2015, Washington had its worst wildfire season on record in terms of total acres burned, and the state saw its largest fire on record. Oregon also saw a record year in terms of the number of homes consumed by fire. In 2014, Oregon and Washington logged 4,567 fires that scorched 1,371,601 acres on federal, state and private lands. That’s 18 percent higher than the 10 year average of 3,877 fires in both states and almost three times greater than the 10 year average for burns, which is 452,039 acres. Washington’s 256,108 acre Carlton Complex was the state’s largest-ever blaze, while Oregon’s was the Buzzard Complex, which burned 395,747 acres in southeastern Oregon.

Further North, Western Canada got an early start to its 2015 wildfire season, with two large blazes forcing oil sands producers to curtail 230,000 barrels, or 10 percent of daily output, for several days. A study analyzing historical wildfires in Alberta, Canada, from 1961 through 2010, found the number of wildfires and average area burned grew during this time alongside temperature rise.

For more information on increased wildfire risk including the state of scientific understanding, relevant news and specific impacts, visit Climate Signals.