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  March 27, 2017

Study Links Extreme Weather Events to Climate Change

Dr. Michael Mann says the way climate change affects the jet stream is intensifying and increasing the regional scale of droughts and flooding
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Dr. Michael E. Mann is Distinguished Professor of Meteorology at Penn State University, with joint appointments in the Department of Geosciences and the Earth and Environmental Systems Institute (EESI). He is also director of the Penn State Earth System Science Center (ESSC).


KIM BROWN: Welcome to The Real News Network in Baltimore. I'm Kim Brown.

Unprecedented summer warmth, flooding, forest fires, drought and torrential rain –- extreme weather events are occurring more and more often. But now, an international team of climate scientists have found a connection, between many extreme weather events, and the impact climate change is having on the jet stream. Jet streams are fast-flowing air currents found in earth's atmosphere.

To discuss this significant new study, titled, "Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events," which is published in the peer-reviewed journal, Nature.

We're joined by its lead author Dr. Michael Mann. He is the author of the book titled, "The Hockey Stick and Climate Wars." His latest book, co-authored with Tom Toles, is titled, "The Madhouse Effect: How Climate Change Denial is Threatening Our Planet, Destroying Our Politics, and Driving Us Crazy."

Michael, we appreciate you joining us again, here on The Real News. Thank you.

DR. MICHAEL MANN: Great to be here.

KIM BROWN: More and more, scientists have been connecting the dots of human-caused global warming, and extreme weather events. Tell us about the role of the jet stream, and what you've found.

DR. MICHAEL MANN: Yeah. We know climate change is leading to more extreme weather events of certain types, obviously more heat waves, more intense heat, and more drought, because of the... As you bake the earth with record temperatures, you dry out the soils. You get record levels of drought, and a warmer atmosphere holds more moisture, so you can get record flooding as well. All of that is related to just the basic attributes of the atmosphere getting warmer, the earth getting warmer.

What our study shows, is that there's an additional factor that is leading to more extreme weather. Climate change, is changing the behavior of the jet stream, in a way that makes it not only more likely to get stuck in place, so that you have low pressure centers, and high pressure centers, sort of stuck in the same place. Warm temperatures, or cold temperatures, stuck in the same place, wet conditions or dry conditions, stuck in the same place.

But climate change is actually amplifying the jet stream waves, in a way that leads to larger regional weather anomalies. Larger amounts of rainfall, of sustained rainfall, more sustained drought, more sustained heat. So, there's this additional factor, in how climate change is changing the jet stream that is intensifying many of these extreme weather events even further, beyond what we would expect, just from the direct effects of global warming.

KIM BROWN: Talk more about how we know that there is a heavy influence of human-caused, or anthropogenic climate change, to extreme weather events, and not just El Niño, or La Niña, or natural changing weather patterns, as climate deniers would have us believe.

DR. MICHAEL MANN: Yeah. That's right. What we looked at, was what is the pattern of temperature that leads to this particular configuration of the jet stream. Where it gets sort of stuck in place, and where the waves, the troughs and the peaks of the jet stream become amplified, so you get very large regional weather anomalies? And because the jet stream is stuck in place, individual regions continue to get rained on for weeks at a time, or continue to get baked by sunshine, and unprecedented warmth for weeks at a time.

It's those very persistent anomalous weather patterns that give us the extremes that we've seen in recent years: the 2011 Texas and Oklahoma drought, where they lost 25% of their cattle, and agriculture was devastated, the 2010 Moscow heat wave and wildfires, the 2015 California wildfires. Each of these events, it turns out, occurred when the jet stream was in that particular configuration.

What we've shown, using climate models, is that global warming is making that jet stream configuration more frequent. And it's making it more frequent because it's changing the pattern of temperatures, in a way that favors that pattern in the jet stream. The bottom line is, that global warming leads to amplified warming in the poles, where you melt away sea ice in the Arctic, so you get even more warming in the Arctic.

And that means you decrease the gradient, as we call it, in temperature, the change in temperature, from the warm tropics to the cold poles. We decrease that difference in temperature by warming the poles so much, and when you do that, you actually change the pattern of the jet stream. And you change it in a way that, projects onto that particular pattern that leads to these unprecedented weather anomalies.

KIM BROWN: Michael, you used both computer simulations, and observational and historical data, going back to records from as early as 1880, and roughly 50 climate models from around the world. What did you deduce from these recordings, and these models?

DR. MICHAEL MANN: The first thing we did, was to look at the climate models and project forward in time, over the historical period, and see what happens to this particular temperature pattern that we know is associated, with these anomalous jet stream conditions, that give us these extreme weather events.

We were able to show, that very consistently, among nearly all of the climate models that pattern of temperature change becomes more and more frequent, and, again, it becomes more frequent, in large part because you're warming the poles so much. That makes that particular temperature pattern that gives you these jet stream conditions more frequent. And that's happening in the climate models.

Well, then we looked at the observations to see what was happening to this temperature pattern, in the historical surface temperature observations. And exactly the same thing is happening: that pattern is getting more common over time. We know that's happening in the observations, and in the observations, we know that that it's tied to many of these extreme weather events we've seen in recent summers. What the climate models tell us is that that change is due to increasing greenhouse gas concentrations.

KIM BROWN: What other key takeaways from your study should we know, in your opinion, Michael?

DR. MICHAEL MANN: What we should know, is that many of the extreme weather events that we've seen, particularly in the summer season. The mechanism that we're looking at is primarily relevant to the warm part of the year. The spring, the summer, the early fall, and so when we think of many of these extreme heat waves, and droughts, and flooding events we've seen in Europe and North America in recent years, many of these events are indeed associated with this unusual pattern in the jet stream.

What we've done is, to connect the dots and say, that pattern in the jet stream is being made more common by human-caused climate change. So, we've sort of connected the dots from many of these extreme weather events that we've seen in recent years, to human-caused warming of the planet.

KIM BROWN: In terms of practical application, you looked at the historical atmospheric observations, to document the conditions under which extreme weather patterns form and persist. Does this mean that we could get to the point where we can know an extreme weather event will arrive long before it actually happens?

DR. MICHAEL MANN: Yeah. There's a good chance that we can identify in advance, with weather models, when the atmosphere appears to be getting locked into one of those configurations, that favors these extreme persistent weather events. It doesn't mean we could predict the precise weather events. But we can predict when we are likely to see an increase in these extreme weather events, in the northern hemisphere. So, there's some potential predictive capacity there.

KIM BROWN: You know, Donald Trump released his budget, and it contains a barrage of cuts to federal agencies, particularly to the EPA, to NASA, to NOAA. What do you think about these budget cuts that Trump has proposed across all government agencies, on anything related to climate change, effects important research such as yours that might actually aid in human survival on a warming planet? Your thoughts about that.

DR. MICHAEL MANN: Yeah, it's dangerous. It's, frankly, dangerous. The cuts that he is proposing in NOAA, in NASA's Earth Science Program, the Satellite Programs that help us measure what the atmosphere and ocean and ice are doing, that forecasters use to help us understand the threat from hurricanes and extreme weather events.

It's, to me, his de-funding of many of the basic scientific programs that are there to measure, to monitor what's happening with the climate, is sort of like having a child who is suffering from a very high fever, and then deciding to just stop measuring their temperature, stop taking their temperature. That's effectively what he is doing. But not just with a single human being –- with our entire planet –- and it's a threat to all of us.

It's a threat to companies and corporations, and stakeholders that rely upon this information, for assessing risk and making important decisions. And obviously it's a threat to all of society, which will suffer from the lack of information that we will have, and the lack of our ability to make, to take certain precautionary and adaptive steps, to protect ourselves from the impacts that climate change is having.

KIM BROWN: The name of the report is titled, "Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events."

We've been joined with Michael E. Mann. He's a doctor, he's from Penn State University, he's also the lead author of this. If you'd like to check out this report, we will have a link to it at the bottom of this interview.

Michael, we appreciate you joining us, and good work on this report. Thank you very much for your contributions to this.

DR. MICHAEL MANN: Thank you, always a pleasure to talk with you.

KIM BROWN: Thank you, and we appreciate you all watching and supporting The Real News Network.




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