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Dr. John Abatzoglou and Dr. LeRoy Westerling explain how a warming earth has exacerbated the impact of forest fires, and how climate action could save lives

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DHARNA NOOR: Welcome to The Real News Network. I’m Dharna Noor coming to you from Baltimore. Firefighters finally gained ground on the deadliest wildfires in California history on Sunday. The wind eased up while searchers combed charred ruins from more victims of the blazes that have claimed at least 40 lives. Another 75,000 have been displaced. More than 5,700 structures have been destroyed by more than a dozen wildfires, which ignited about a week ago and have consumed an area larger than New York City. The city of Santa Rosa lost entire neighborhoods. What’s getting far less attention in the media is the evidence linking the historically catastrophic wildfires to the effects of human-induced climate change. With us to discuss this and how we might prevent more wildfires in the future, we’re joined by two expert guests. We have John Abatzoglou, who’s an associate professor at the Department of Geography at the University of Idaho and we’re also joined by Dr. Leroy Westerling, who’s an associate professor of management at UC Merced and the co-director of the Center of Climate Communication. Thank to both of you again for joining. The 40 confirmed fatalities make these fires in California the deadliest since record keeping began. This surpasses the 29 deaths from the Griffith Park fire in 1933 in Los Angeles. How do we know human-caused climate change has contributed to these horrific events? What are the so-called fingerprints of climate change that scientists are identifying. Let’s start with you, Professor Abatzoglou. I understand that in one of your studies, you found that human-caused climate change nearly doubled the amount of area taken by forest fires between the mid-80s and 2015. J. ABATZOGLOU Yeah, so I think the way to think about this is we go back to sort of the ingredients you need for sort of having a campfire and those ingredients are fairly simple. There’s three of them: you need to have enough fuel, you need that fuel to be dry enough and then you need an ignition source. If we’re thinking about our forested regions across the western United States, as well as other areas globally, usually there’s enough fuel there but usually what limits fires, especially large fire seasons is that the moisture is typically wet enough. Things that end up altering reducing the vegetation in fuel, whether that’s a recession in mountain snowpack, warmer summer temperatures that draw more moisture out of fuels, those things can begin to allow forests that used to be sort of more resilient to fire to become fire prone. We have seen a substantial warming in temperatures. We’ve seen the fingerprints of losses in mountain snowpack and collectively, these things have increased fuel dryness in the summer time. There is a pretty strong link between the amount of area that burns in our forests, particularly at mid to higher elevations and warm and dry summers. In our study, we found that basically of those three ingredients, manmade climate change was acting to increase fuel dryness, creating basically a longer window of the year when fuels could be receptive as to igniting and carrying fire. DHARNA NOOR: Professor Westerling, your research has also shown that wildfires have risen. It’s shown that they’ve risen by over 500% on public land since the last 1970s. Is this increase in wildfires tied to the effect of climate change as well? L. WESTERLING Actually, so if you’re looking at the most recent decade, it’s over 1,200% increase since the 1970s… DHARNA NOOR: Wow. L. WESTERLING … in the area burned in federal forests in the western United States. It’s most strongly linked to changes in the time in the spring and warmer temperatures. We have really diverse set of ecosystems across the western United States, even within forest areas and they have different sensitivities to increasing temperatures and changes in the timing of spring. The places that have shown the largest increases linked to those changes in spring timing and warmer temperatures, are places where the forests have been pretty cool and wet historically. The warming that we’ve experienced and kick them up into a different regime where they can burn more often. The dry season in the summer gets longer when you melt the snow out earlier and you have more evaporation driving fuel aridity that can increase fire. DHARNA NOOR: Dr. Westerling, are there other effects other than climate change such as deforestation or fire suppression that’s creating the conditions for more extreme fire events? L. WESTERLING: Yeah, so what’s really been compounding the risk or the vulnerability of climate change has been the increase in fuels and forests in parts of the west due to fire suppression. There’s been some of that all around the west at different elevations depending, but some of the areas that are being most affected int the southwest and just to a little bit lesser extent, California. The mid-elevation Sierra-Nevada forests. If you think about it, prehistorically I should say, these might have been really open canopy forests where the fire very often would be down at the surface burning grass and things like that and not as much in the canopy of the forest because of the spacing between the trees. Fire suppression allowed those forests to grow much more densely in California, Sierra-Nevada, in southwest and some other parts of the west. That has actually made it more vulnerable to climate change because as you warm those forests up and backward moisture every year, you’re creating sort of competition for moisture between the individual trees and the drought effects are more severe on them. When you get fire, now it’s burning through your canopy and it’s not as bad at the surface. DHARNA NOOR: We just saw that NASA posted satellite images of the California wildfires as seen from space. Let’s take a look at those. Are there any concerns about wildfires being a contributor to climate change from all the burning carbon and could this set up a sort of feedback loop, which would lead to higher temperatures and therefore more disasters? Let’s start with you, John. J. ABATZOGLOU: Yeah, so wildfires are part of the Earth’s system and fire is a natural process that we have to remember when talking about this but at the same time when we see fire burn, they’re burning above ground carbon and a lot of that is getting back up into the atmosphere and contributing to the atmospheric carbon burden. To some effect, these forests do recover and as they recover, they can take up carbon dioxide, et cetera. How those things actually play out through time is yet to be determined. We have seen a substantial increase in fire activity across the west, across much of Canada and Alaska and we’ve seen a lot of carbon coming off of these landscapes. I think that Leroy’s done some work on this, particularly with the carbon perspectives. He might have a better take on it. DHARNA NOOR: Dr. Westerling, would you like to weigh in? L. WESTERLING: Yeah, with my colleague and a student of his, we’ve been looking at integrating statistical models that I do of how fire changes in response to the changes in climate with ecosystem modeling. The interesting thing that we saw is that as you warm things up and you increase the frequency of large fires in the Sierra-Nevada, you get shifts over time where more and more of the forest becomes a source of carbon and that course of carbon to the atmosphere instead of in that sync. In recent past, these forests have been in that sync. They’ve been growing faster than they have and taking up carbon faster than they’ve been releasing it. As you warm things up and increase the pace of fire, they start shifting so some parts get deforested and other parts are just younger forests and they don’t get a chance to replace the lost carbon before they are affected by disturbances. We actually had to run the models out about 500 years. There’s a real lag between changing climate now and when the ecosystems fully respond into the future. Really, the biggest change in carbon, we’re not in the 21st century in this modeling, but in the 22nd century. DHARNA NOOR: Okay, Dr. Abatzoglou and Dr. Westerling please just stick around for part two and we’ll continue to discuss these devastating forest fires in California. Thanks so much for joining us and thank you for joining us on The Real News Network. Stick around for part two.

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Dr. LeRoy Westerling is Associate Professor of Management at UC Merced and Co-Director of the Center for Climate Communication. His research interests include applied climatology and seasonal forecasting for wildfire management, climate change impacts on wildfire and related aspects of mountain hydrology, paleo reconstructions of climate-wildfire interactions, and simulation of extreme events for risk assessment and adaptation planning.

Dr. John Abatzoglou has been at the University of Idaho since 2009, after receiving his bachelor's degree in Atmospheric Science from UC Davis and doctorate in Earth Systems Science from UC Irvine. John's academic interests are centered around climate and weather of the American West and their impacts to people and natural resources of the West.