Fire and floods: Did climate play a role in this fall's disasters?

Wildfires. Floods. Hurricanes. Earthquakes.

In a disaster-filled fall, it’s no wonder some people are feeling like Mother Nature is in an all-out assault against humanity.

Predictably – and perhaps, rightly – it’s led to renewed outrage about the dangers of climate change and the need for better disaster planning. But is this really a sign of what we can expect going forward? Yes, and no.

Most climate scientists say the warming climate has affected conditions such that we can expect more extremes of certain sorts: heat waves, heavy rainfall, droughts. Sea-level rise has worsened storm surge and sunny-day flooding. And significant, but still controversial, research has started to tease out climate change’s role in contributing to more severe storms and hurricanes as well as lengthening the wildfire season and creating hotter, drier conditions in which fires can flourish.

But there’s also no solid research at this point linking any of this fall’s specific prominent disasters to climate change (such studies will surely come, but it’s too soon to know what their conclusions will be), and experts caution that all of these disasters are also relatively “normal” events that have occurred throughout history. Trying to see patterns or apocalyptic trends in such events is a human impulse, but not a very scientific one.

“The Earth is a dangerous place, and there are extremes of all sorts that happen all the time,” says Roger Pielke Jr., a University of Colorado political scientist, author of “The Rightful Place of Science: Disasters and Climate Change,” and a tempering voice when it comes to attributing weather events to climate change. “One of the challenges that everyone faces in understanding disaster is that you’re not paying attention to disasters when you’re taking the kids to school, so it’s very easy to not get a sense of the patterns in history.”

Asking the right questions

The disasters this fall have been severe and prominent, and have caused widespread damage. As those in California’s Wine Country are still battling fires and assessing the extent of both lives and buildings lost, Puerto Rico is only beginning to restore power and water to its residents, and Houston is still cleaning up and facing a daunting rebuilding project from the floods from hurricane Harvey.

Last week, the National Oceanic and Atmospheric Administration (NOAA) announced that through September, the number of US disasters costing at least $1 billion in damages had hit 15, tying with 2011 for the most billion-dollar disasters since 1980 for the first nine months of the year – and that was before the wildfires hit Northern California.

“It is possible that 2017 will tie or surpass 2011 in terms of the number of billion-dollar events, and either closely match or exceed 2005 in terms of total cost,” says NOAA scientist Adam Smith in an email, noting that the incredible hurricane impacts of 2005 and 2017 put those years in a class of their own (at least since 1980) in terms of total costs.

Such measures, of course, are also influenced by where people choose to build and the amount of wealth concentrated on coastlines, along with the severity of disasters, and critics like Professor Pielke have questioned how much they really tell us about disaster trends.

Dr. Smith agrees that increases in population and material wealth are an important factor in the trends, as well as the fact that building codes are often insufficient for reducing damages in the vulnerable areas – like coasts or floodplains – where population centers are. But he adds that “climate change is playing a role in amplifying the frequency and intensity of some types of extreme weather that lead to billion-dollar disasters.”

Increasingly, the rapidly developing field of “attribution” research – the science of teasing out the role played by climate change in certain types of weather events and, in some cases, in individual ones – bears that out.

But those scientists are generally the first to caution that asking “Did climate change cause X event?” is entirely the wrong question.

“The question is, ‘Are we seeing more or less frequency? Greater or less severity?’ ” says David Titley, a meteorology professor and the director of the Center for Solutions to Weather and Climate Risk at Penn State University. “Attribution of a single event turns out to be pretty hard.”

Professor Titley likes to compare weather events to waves at a beach and climate to the rising tide, so that waves are coming in from an ever higher baseline.

Titley, who chaired the US National Academies committee that produced “Attribution of Extreme Weather Events in the Context of Climate Change” a year ago, is far from certain there will be a clear role for climate change in some of the most prominent individual events from this fall. Global warming has a very direct link to extreme precipitation, for instance, but the biblical amounts of rainfall that submerged Houston are primarily due to the storm stalling out over the city – something that is harder to explain with climate models.

“So the question is, are the weather patterns changing so that the chances of a hurricane stalling along the coast have become greater?” says Titley. “Are the wind patterns impacted, is the jet stream being changed? That’s probably the most interesting, but it’s also the most tenuous, at the edge of where the science is right now.”

But he also thinks people tend to be too caught up in that question of individual events. “I tell people we’re down looking at the twigs on individual trees, and ... we need to back up and look at the forest again.”

The research that has been done on the links between climate change and extreme weather shows the clearest role in certain types of events: heat waves, extreme precipitation events, and droughts. It’s much harder, say Titley and others, to tease out the role of climate change in individual storms, tornadoes, hurricane, or wildfires, in part because they’re so complex.

Finding opportunity in disaster

That said, many fire experts also say there is also clear connection between wildfire trends and climate change, as well as other human-caused factors, like management plans that favor fire suppression.

“We’ve known about the link between climate change – a warmer, drier climate – and wildfires for over a decade,” says University of Colorado Prof. Tania Schoennagel, citing a 2006 study that showed that temperatures have increased about 2 degrees F in the Western United States since the 1970s, and that fire season has increased by almost 3 months in most places.

“As a consequence, the number of large fires burning in the West was about 20 in the 1970s, and now is well over 100 large fires per year,” says Professor Schoennagel. The 10 largest fire years – in terms of acres burned – since the National Interagency Fire Center began collecting data in 1960 have all occurred since 2000, she adds. (The data prior to 1983 is considered less reliable.) About 8.5 million acres have burned in the US this year, mostly in Montana, Nevada, California, Idaho, and Oregon. “The climate is changing, and it is making wildfires more common and frankly inevitable in the West,” Schoennagel says.

John Abatzoglou, a geography professor at the University of Idaho, agrees, though he adds that the changing climate conditions play out against a legacy of fire suppression and land management decisions which have allowed fuel in many areas to both build up and dry out.

“There’s a really interesting interaction here whereby the legacy of fire management has made our landscape more susceptible to climate variability and climate change,” he says.

It’s also notable that people – rather than lightning – started 84 percent of fires over the last two decades.

Professor Abatzoglou helped author a National Academy of Sciences study that found that human-caused warming caused about half of the increase in dryer fuel, and suggested that about twice as many acres burned between 1984 and 2015 as would have been expected to burn without that warming.

“Regardless of whether people’s beliefs are that climate change is behind this, or not being allowed to log, or the legacy of forest management, some of the solutions are the same,” says Abatzoglou. Among those: more prescribed burns, education about the dangers of reckless activities in causing fires, and better decisions about where, how, and whether to build in the wildland-urban interface – the areas where people and houses abut up against forests and grasslands.

Looking to those lessons, as opposed to feeling a sense of apocalyptic doom or arguing about the role of climate change, is where a lot of agreement can be found.

“The scary thing is, none of these [disasters this fall] are really the worst-case scenarios. There are worse scenarios for earthquakes. Miami could have had a direct hit [from hurricane Irma], but didn’t. These should be wake-up calls: No, the world is not ending, but this is how the world operates,” Pielke says.

Titley, from Penn State, agrees.

“There is no evidence I’ve seen from any climate scientist that says hurricanes are going to get weaker, or seas will come down, or air is going to get drier,” he says. “And a lesson from the past eight weeks is, we are not ready for today’s weather, let alone tomorrow’s weather.”

Pielke suggests that we should have the same sort of post-mortem on disasters, and what can be done better, that we have for airplane crashes. In that sense, he says, “A disaster is an opportunity.”

[Editor's note: This article has been updated to clarify the description of Roger Pielke's work to more accurately describe his position on attribution science.]