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Research Shows How Climate Change Is Fueling California Wildfires

 July 16, 2019 at 1:58 PM PDT

Speaker 1: 00:00 And the last couple of years, California has seen some of the most disastrous wildfires in recent history. It's caused scientists to ask, could climate change be fueling fires? A new study gives confirmation to what's been long suspected. The warming climate has been the deciding factor and many but not all cases of wildfires as part of coverage from the KPBS climate change desk. Alexander Gershwin of who is with the Scripps Institution of Oceanography, and it was among many scientists who coauthored this study, joined us to talk about the findings. Alexander welcome. Thank you Jay. Nice to be with you. So do the results of this study change what we know about climate change in wildfires or or does it put it into focus? Speaker 2: 00:42 It confirms a what we knew in certain cases, but it basically gets at the mechanisms that are responsible for the changes. Hmm. So what are some of those mechanisms? Well, so in California are different climate regimes, different ecosystems and different wildfires themes. And in a mountainous forest, for example, wildfires typically burned in the summertime. They're typically started by lightning and in a coastal ecosystems, wildfire season is fall because that's when dryness coming out of the long dry summer coincides with the beginning of the Santa Ana wind season. Uh, and it's, uh, the winds that, that really fanned those fliers in coastal regions. And so the climate influence isn't going to be a somewhat different in these different regimes. Speaker 1: 01:38 Okay. So hotter drier climate equals a, an elevated risk for wildfires. Speaker 2: 01:45 Well, so, um, that, that is a, the mechanism by which a climate change impacts wildfire regimes in the mountains. Uh, in coastal ecosystems, it's quite different. Uh, the vegetation is, uh, is pretty much always dry enough to burn after the long dry summer. Uh, and it's the beginning of the Santa Ana winds season in the fall, uh, that occurred before the first rains of winter. They drive the most catastrophic wildfires and coastal ecosystems. And you know, in northern California they have the Ablow winds, uh, in southern California, Santa Ana's. But the coastal wildfire regime is really determined by dry fuels coinciding with dry gusty warm winds. And we know that, uh, Santa Ana winds really peak in December. They start typically in October, but we're also losing precipitation, especially in the fall and spring as climate change progresses. And that allows the vegetation to persist in the dry state into the peak of the Santa Ana wind season in southern California. Uh, and then you get, uh, events like the Thomas fire, which burned for most of December and into January, um, a couple of years ago. And, uh, that was really due to the fact that there hadn't been any rain until really January. And it was an atmospheric river that finally put out the smoldering remains of the Thomas fire in early January and actually added insult to injury by causing debris flows from the burn scars. Speaker 1: 03:26 Hmm. And this study found that most, but not all wildfires can be linked to climate change. Can you clarify what that means? Speaker 2: 03:35 This study looked at tendencies in wildfire activity, uh, not necessarily specific wildfires. And so, uh, what we mean by most is that, uh, in certain ecosystems, uh, climate change is the dominant force of change. And, uh, that would be in mountain forest ecosystems in, um, coastal zones, uh, where wildfires are typically found by drag gusty winds. We expect not necessarily in increase in wildfire activity, but a land thing of the season further into winter. And that's, that's when we have a better chance to have back to back Santa Ana winds fanning wildfires that burn longer. Hmm. Now we have also studied Santa Ana winds in a different paper that was recently published. And, uh, we can see that, uh, Santa Ana wind activity is expected to decrease somewhat, uh, with climate change. And, uh, that's, that decrease is most pronounced in the fall and spring, not so much in the winter. And, um, so we, uh, put, putting all this information together is complicated, but it, it indicates that we're likely to have wildfire season migrating from the early fall into the winter as time goes on. Speaker 1: 05:01 So how were you able to directly and definitely connect climate change as the cause for certain wildfires? Speaker 2: 05:08 The paper really looked at, uh, observations. So we looked at the historical changes, but we also put them in the context of what we expect to occur in the future. And, uh, uh, it's really matching, uh, the observations to those expectations that allows us, uh, to determine what is consistent with climate change and what is. Speaker 1: 05:32 Hmm. And what did the study findings mean for the potential of wildfires over the coming decades? Speaker 2: 05:37 Findings would mean a somewhat different things for different, uh, regions and the ecosystems and climate zones of California, uh, in a and ecosystems. They strongly suggest that wildfire activity will continue to be on the rise for the coming decades and, uh, in coastal ecosystems, we're more likely to see a shift of wildfire activity gradually from the early fall into the early winter. I've been speaking to Alexander Gersh Unov, who is joining me by Skype from the scripts institution of oceanography. Alex, thank you so much for joining us. My pleasure, Jane. Speaker 3: 06:18 Uh.

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A new study finds climate change has already had an impact on California wildfires.
KPBS Midday Edition Segments