Climate scientist discusses this summer’s extreme weather and long-term trends

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• Geoff Bennett:

  Extreme weather is hitting Europe, with catastrophic consequences. At least eight people have died there after severe storms.

• Amna Nawaz:

  In Brazil, at least 31 more people died from flooding. And here in the U.S., more than 80 million Americans are living through blazing temperatures and yet another heat alert.

  It all comes as the planet reached an alarming milestone this summer.

  William Brangham has the story.

• William Brangham:

  In Southeastern Europe, torrential rains brought havoc.

  Flash flooding in Central Greece has destroyed entire streets, flooded homes, and destroyed cars. In some Greek towns, over 20 inches of rain fell in just 10 hours.

• Vasilis Batsios, Greece Resident (through interpreter):

  This has never happened before here. There was a lot of water, and for many hours. For 24 hours, it was nonstop. The amount of water was unbelievable.

• William Brangham:

  Greek authorities say this storm, dubbed Daniel, brought the most extreme rainfall on record, up to nearly 30 inches in one day in some places.

  In Turkey, rescuers on boats had to save people stranded by the floods. Officials say the city was pounded by one month's worth of rain in less than six hours. Like toys in a bathtub, people's vehicles floated through the streets. One man's furniture shop was destroyed after water swept cars into his store.

• Erkan Gurer, Store Owner (through interpreter):

  We came here after our neighbors called us. When we got here, there was water up to the ceiling of our store. There was nothing we could do. We were helpless.

• William Brangham:

  In neighboring Bulgaria, an overflowing river wiped out a campsite, sweeping trailers into the Black Sea. And in South America, where it's winter now, a storm in Southern Brazil brought deadly flooding that inundated entire towns.

• Joseline Giraldi, Shoe Factory Worker (through interpreter):

  I was able to climb to a neighbor's apartment. It was frightening. People on roofs were asking for help. It was like a scene from a horror movie.

• William Brangham:

  It's all part of a larger pattern of meteorological extremes, disasters that climate scientists say are becoming more frequent and more intense as the Earth continues to warm.

  Just days ago, Greece saw the end of weeks of deadly wildfires, and Western Europe is in the midst of an unusual September heat wave. The U.N.'s weather agency says this is the hottest summer ever recorded in the Northern Hemisphere. It reported that August was 2.7 degrees Fahrenheit warmer than pre-industrial averages.

  So let's delve a little deeper into this extreme weather and its calamitous impacts. For that, we are joined again by climate scientist Gavin Schmidt. He's the director of NASA's Goddard Institute for Space Studies.

  Gavin Schmidt, very nice to have you back on the "NewsHour."

  In addition to these extreme weather events we're seeing, we're also getting a better understanding of how a warming world is harming human health. There was a recent analysis by The Washington Post and CarbonPlan that indicated that, in just seven years, half-a-billion people globally will be exposed to extreme heat for at least one month a year, even if they can get out of the sun.

  A study in "Lancet" found that the number of heat-related deaths of elderly people rose by 68 percent in recent years. I mean, it seems that we are making life on Earth increasingly hazardous in ways that we are not at all prepared for.

  Do you think that that's overstating it?

• Gavin Schmidt:

  No, I think that's exactly right.

  We have systems and infrastructure in place that help us deal with the climate that we had. But climate is changing. We are pushing our living space into areas, into temperatures that we have never experienced. And we're seeing that this summer, particularly.

  We're seeing this kind of in the long-term trends. We are moving out of society's comfort zone. And that means that places that were prepared for a certain spread of temperature and a certain number of extremes are now being hit with larger extremes. They're being hit with higher temperatures, more intense rainfall.

  And the structures that we have, the infrastructure that we have is just not being able to cope with that.

  But what we're seeing now is that those things that were one-in-100-year events are now one-in-50-year, one-in-30-year, once-a-decade, and soon conceivably could be an every-year or an every-couple-of-year event.

  And that's the difference. It's not that these things have never happened before. It's not that we have never had a heat wave. It's not that we have never had strong rainfall or droughts. But the frequency and intensity of these features is increasing. And we can see that in the statistics around the globe.

• William Brangham:

  I want to ask you about our understanding about the role that climate change plays in all of this, because, just as you're saying, we have had hot summers and forest fires and flooded areas well before climate change came along.

  But we know warming world is increasingly complicit. How do you counsel people to understand those connections?

• Gavin Schmidt:

  Well, we have noise, the weather noise that has always been there, a function of atmospheric dynamics, a function of El Nino events in the Tropical Pacific.

  But we have a shifting baseline. Every decade in the — for the last 50 or 60 years, the planet has warmed. And we have been talking about this, scientists have been talking about this for many, many decades. And so we're talking increased intensity and frequency of heat waves.

  We're talking about increased intensity of rainfall events. When we have a drought, we're talking about ever-drier soils, because the air is taking out more moisture from the soils. We're talking about increases in sea level, both because the water itself is expanding as it gets warmer, but it's also because we're melting ice around the world.

  And that's adding to the total mass of the ocean. And so slowly, but surely, and acceleratingly, we're seeing sea levels rise. And we're seeing the consequence of that in nuisance flooding and storm surge damage.

• William Brangham:

  Given all of that, I mean, it does seem that cutting our use of oil and coal and gas is increasingly critical. And, as we have reported and others have, that there is a genuine revolution under way in renewable energy globally that is going on.

  Do you think that, even if we hit our most optimistic projections for controlling emissions and controlling warming, how much of this damage is still baked in?

• Gavin Schmidt:

  So, good news/bad news, right?

  If we stopped emitting carbon into the atmosphere tomorrow, which obviously is not going to happen, then temperatures would not rise any further, right? So, that means that any further increases from where we are now are really under our control. We have agency. What we choose to do as a society makes a difference to how much warmer it's going to get.

  Unfortunately, it's very hard to go back, right? So it's very hard to now suddenly cool the climate back to where it was in the 1980s or in the 20th century. And so what we're seeing now, in some sense, may be baked in.

  But we're not baked into further increases and further acceleration in that system.

• William Brangham:

  Gavin Schmidt of the Goddard Institute, thank you so much for being here.

• Gavin Schmidt:

  Thank you very much for having me.