As wildfires sweep through swaths of the West, turning forests, grasslands and even homes into charred ruins, many scientists say the destructive blazes are linked to climate change.
And, they say, things are only going to get worse unless carbon emissions are reduced.
“The frequency of hot days and hot periods has already increased and will increase further,” said Michael Oppenheimer, professor of geosciences and international affairs at Princeton University, during a conference call June 28 with media members.
The call was timed to coincide with the release of a report called, “Heat Waves and Climate Change.” The peer-reviewed report, which summarizes work by numerous researchers, was produced by Climate Communication, a non-profit funded by the Rockefeller Brothers Fund and the Climate- Works Foundation.
Oppenheimer was one of three researchers featured in the call who made the case that the world is growing warmer, and humans are the cause.
“What we’re seeing is a window into what global warming looks like,” Oppenheimer said. “It looks like extreme heat. It looks like fires. It looks like this type of environmental disaster.”
The conference call came on the same day that fire managers in Colorado Springs, Colo., announced that 346 homes had been burned during the catastrophic Waldo Canyon Fire on that city’s western edge.
On that same day, 42 large, active wildfires were burning in the West, according to the National Interagency Fire Center – including eight in Colorado, five in Utah, and three in New Mexico. A total of more than 800,000 acres was involved.
The fire center increased its national preparedness level, a measure of the seriousness of wildfire activity, to PL 4 that day – only the third time in 22 years it had been at PL 4 in June. The other years were 2002 and 2008.
Having a heat wave
The researchers on the panel predicted that in coming decades in the United States, heat waves will be more frequent and wildfires will be more common – so much so that ecosystems may be changed.
“We are seeing a big increase in the number of days over 100 and that’s expected to continue, especially if business-as-usual emissions continue,” said Susan Joy Hassol, director at Climate Communication, who moderated the panel.
During the last week in June, much of the nation baked in a suffocating heat wave that shattered records.
Colorado Springs, Colo., hit an all-time record high of 101 degrees on June 26, according to the Weather Channel, and Denver set an all-time high of 105 that same day. Both cities have records that date back to the late 1800s.
The heat wave stretched from the Rockies across the Midwest to the East and South. June 29 was the hottest June day ever in Washington, D.C., which hit 104. Atlanta’s high of 106 on June 30 was an all-time record for the state of Georgia.
Over two dozen cities across 10 states set or tied all-time record highs on June 29 and 30.
“Since 1950 the number of heat waves worldwide has increased, and heat waves have become longer,” states the report.
The report also says:
• The hottest days and nights have become hotter and more frequent.
• In the past several years, the global area hit by extremely unusual hot summertime temperatures has increased 50-fold.
• In the contiguous United States, new record-high temperatures over the past decade have outnumbered new record lows by a ratio of 2 to 1.
But scientists admit that a single heat wave doesn’t equate to a trend.
“Can we say this heat wave is a smoking gun for climate change? No,” Glen Mac- Donald, the director of the UCLA Institute of Environment and Sustainability, said in an interview with the Los Angeles Times. “But … it’s consistent with what we would anticipate.”
More red on the map
Most climate and weather scientists worldwide believe that climate change is occurring and that it is at least partially caused by a human- driven increase in carbon-dioxide emissions. Ninety-seven percent of scientists agreed “greenhouse gases have been responsible for most of the unequivocal warming of the Earth’s average global temperature in the second half of the twentieth century,” a 2010 report in the Proceedings of the National Academy of Sciences journal found.
But climate-change skeptics are numerous. They say the data on which the globalwarming theory relies are questionable and don’t go back far enough. They say the urban “heat island” effect is what’s causing cities to warm, as asphalt and concrete retain heat at night. They point out that there have been severe hot spells and droughts in the past, such as the one in the late 1920s and early 1930s in Oklahoma, Texas, and neighboring states.
Nearly half of Americans believe “the seriousness of global warming is exaggerated,” according to a recent Gallup poll.
However, scientists say computer models are growing ever more reliable, and they indicate that warm seasons are growing longer, droughts are becoming more common and minimum temperatures are rising.
The panelists agreed. Certainly there have been heat waves in the past, they said, such as the searing drought and high temperatures of the Dust Bowl. And it’s true that not every part of the world is seeing record highs.
But, Oppenheimer said, the different temperatures are like dots on a map, or pixels in a photograph. Different things happen in different pixels.
The global average offers a less-dramatic picture than individual pixels, “but we’re seeing a gradual change as more and more of the pixels get redder, and this is a pretty red one. This is an example of the sort of thing that happens as the global-warming trend continues.”
Added Hassol, “What we’re seeing now when we look at the global temperatures is, more of the map is red. Back in 1934 when the U.S. was having a tremendous heat wave and it was the Dust Bowl, there was a bright red spot over the U.S. and Russia, and the rest was blue.”
According to “Heat Waves and Climate Change,” statistical analysis of the Russian heat wave of 2010 shows there was “an approximate 80% probability” that the record heat would not have occurred without climate change, “or alternatively the probability increased by a factor of five.”
The report also states, “Globally, extremely warm nights that used to come once in 20 years now occur every 10 years. And extremely hot summers, those more than three standard deviations above the historic average, are now observed in about 10% of the global land area, compared to 0.1 to 0.2% for the period 1951 – 1980.
“These trends cannot be explained by natural variation alone. Only with the inclusion of human influences can computer models of the climate reproduce the observed changes.”
A warming earth would have benefits. Last winter’s mild temperatures, for instance, meant lower heating costs throughout much of the United States.
The down side of global warming would be considerable, however. Parts of the planet now occupied might become uninhabitable if summer days and nights stay hotter longer, the researchers said.
“Respite from the heat is very helpful in coping, even just for a few hours,” said Howard Frumkin, dean of the School of Public Health at the University of Washington, during the conference call.
“That low temperature is the key way people are able to cope, and as the minimum temperatures rise, people lose the ability to get respite during the evening hours. . . When the ambient heat around a person becomes significantly higher than body temperature, it becomes difficult to dissipate heat.”
Poorer regions of the globe will have more trouble adapting to a warmer climate,
Frumkin said. “It depends on resources and other factors. Places with air-conditioning are going to be more resilient to extreme heat than paces like Delhi [in India].”
A fuels build-up
While the veracity, causes and possible impacts of climate change are hotly debated, of particular concern in the West is the effects a continuous warming trend could have on wildfires.
Colorado is seeing its worst fire season since the drought year of 2002. New Mexico is recovering from two record fires — one that burned 465 square miles and another that destroyed more than 240 homes.
Experts say the number of major wildfires and the length of the fire season has increased over the past 25 years, according to the Associated Press.
“There’s some evidence that the forestfire frequency has increased in the West, even where humans aren’t the direct factor in terms of ignition,” Oppenheimer said.
As summer temperatures go up, evaporation increases, said Steven Running, director of the Numerical Terradynamic Simulation Group at the University of Montana Department of Ecosystem Sciences.
“A couple degrees of increased temperature increases evaporation,” he said. “It also lengthens the fire season. We are having major wildfires and it’s not even the season yet.”
Asked whether a fuels build-up in Western forests is also to blame, Running said it is certainly a factor.
“It’s a combination of decades of fire suppression, less active fire management and reduced harvesting,” he said.” We have a lot of forests in the West that have a lot of fuel built up.
“In the East, a dead tree rots away. In the West it doesn’t rot away. You find fence posts that are 100 years old. Dead trees literally sit there until a fire comes along.
“When you add accelerating tree mortality from the pine-beetle epidemic you have millions of dead trees standing there. You certainly can’t have a fire without fuel.”
But the experts said climate change is a factor as well in recent catastrophic wildfires. For one thing, warmer winter temperatures are allowing more pine-beetle larvae to survive into spring.
“That means those beetle populations wake up in the spring and can start the attack that much sooner and that much more aggressively, which provides that many more dead trees,” Running said.
Various types of bark beetles have devastated an estimated 40 million acres of forest nationwide.
Warmer nights exacerbate fire behavior as well. “Our night temperatures typically have been low in the Mountain West,” Running said, “and we now have night temperatures that will stay above 60 and even 70 sometimes. That really gives the fire energy through the night. It used to really lay down when it got dark and cold.”
He said firefighters and fire managers have told him they are seeing dynamics they’ve never seen, such as fires moving rapidly downhill and flaring up at night.
“I think it definitely starts with having so much more dead fuel and dead trees than we have ever had before,” Running said. “Across whole landscapes we have areas where threequarters of the trees are dead. I think that’s part of the differing dynamic.
“With the warmer temperatures at night and more evaporation, you have fuels that are just drier. A couple [less] percent of moisture content in wood makes the flammability go up.”
But Running and the other panelists refused to give a numerical estimate about how big a factor climate change is in wildfires. “It would be really dangerous to lob out a number,” Running said. “It wouldn’t be based on the kind of analysis and statistical rigor we wanted to put out.”
“Most of the scientists I talked to say it’s a contributing factor and that’s all we can say,” Hassol agreed.
A 2011 study by researchers at the University of California, Merced, published in the Proceedings of the National Academy of Sciences found that global warming will likely cause more severe forest fires in the future. By 2050, years without major conflagrations will be rare, the researchers predicted, and forest fires are likely to cause “a major shift in the Greater Yellowstone Ecosystem.”
The conference-call panelists agreed that wildfires and warmer temperatures could transform ecosystems.
“I think we’re going to see a fair bit of the Western landscape change in composition,” Running predicted.
“As these fires burn off large areas of landscape, something different is going to grow back. Areas of forest cover may return as sagebrush or chaparral shrub.”
Also of concern is the cost of future “superfires,” as they have been dubbed.
The percentage of the Forest Service’s budget devoted to firefighting has risen from 13 percent in 1991 to 48 percent in 2009, according to the Denver Post. That year it was nearly $2 billion.
“They can spend a couple million dollars a day on the size of fires we’re seeing in Colorado,” Running said.
Wildfires have many other costs in terms of homes destroyed, impacts to health from smoke and soot, and emotional impacts, the panelists said.
The National Oceanic and Atmospheric Administration estimated the total costs associated with heat, drought and wildfire last summer at $12 billion, Hassol said.
“Climate change is already affecting extreme weather,” the “Heat Waves” report concludes. “The National Academy of Sciences reports that the hottest days are now hotter. And the fingerprint of global warming behind this change has been firmly identified.”