ARI SHAPIRO, HOST:

Let's turn now to Brenda Ekwurzel. She's a co-author of the report and director of climate science for the Climate Energy Program at the Union of Concerned Scientists. Thanks for being here.

BRENDA EKWURZEL: Thank you.

SHAPIRO: We just heard from Rebecca Hersher that we already see the impacts of climate change in natural disasters that are more intense and more frequent than before - hurricanes, forest fires and so on. Do we also today see the impacts of climate change in less extreme, dramatic ways - in American cities that are not being decimated and on the front page of newspapers?

EKWURZEL: That's a very good question. What we see is that the costs of climate change are rising - for example, our infrastructure, our roads, our bridges. You may feel you're living far away from the seas. But in fact, there might be an extreme precipitation event that's holding more water than - and creating flash floods that are overwhelming the infrastructure - our roads, our bridges that were built for the climate of the past century.

SHAPIRO: We're also often told that a particular extreme weather event can't be blamed on climate change. How do you balance that statement with the statement that extreme weather events are happening more often and to a greater degree because of climate change?

EKWURZEL: Well, one of the things you'll see in this report and others - in the past few years, scientists have made extremely big advances in understanding extreme weather events, such that we can study in events such as Hurricane Harvey and figure out that it's three times more likely in the year that it occurred than if it happened a century ago.

SHAPIRO: So you're saying that line that we cannot attribute a specific extreme weather event to climate change might now be obsolete?

EKWURZEL: You're right. As scientists, we now no longer say that. It's more about the probability of risk. In fact, when Hurricane Florence was coming, scientists were looking at the background conditions. And they can figure out how much more likely Hurricane Florence was at its severity if you have the climate change we have today with heat-trapping gases. We can also remove those heat-trapping gases from the atmosphere and see would it have been as severe. It would not have been.

SHAPIRO: So if the U.S. makes a hard pivot tomorrow to cut carbon emissions, are we still going to see hurricanes like Harvey and forest fires like the Camp Fire - they just won't be as much worse as they would have been if we kept on the path that we're on? Or will we actually start to see fewer of those extreme weather events that we're seeing now?

EKWURZEL: Unfortunately, it's going to get worse. We're going to have to adapt to the worse climate change. However, the difference between keeping the world at one and a half to two degrees Celsius and three, four, five degrees Celsius is a very scary difference. It's an exponential curve. The impacts get way worse really fast. Therefore it's never too late to work on climate change.

SHAPIRO: So this is not a question of whether things will get better or whether they'll get worse. It's a question of whether things will get worse or a whole lot worse.

EKWURZEL: Yes, that's what we're fighting for. And it makes the difference that the cost in the United States for global emissions reductions are very real. And that's why you see in the report we emphasize lots of the cities, the states that are taking action. They have a mix of portfolios. Some have incentives. Some have a cap on carbon, renewables, nuclear. They have incentives for transportation. All of these are ways that the U.S. is trying to keep the temperature from increasing as fast as it could if we didn't take these steps. And there's momentum that's building.

SHAPIRO: You talk in the report about the cities, the states, the corporations that are taking steps to limit climate change. If the goal is to limit global temperature increases to one and a half to two degrees Celsius, is that possible with just state, local and corporate initiatives? Or does it require the federal government to do more than it's currently doing?

EKWURZEL: It makes it much harder to reach those targets without the U.S. federal government encouraging it. And one thing we know is that every year we have about over 40 billion tons of carbon dioxide going into the atmosphere, and the U.S. was responsible for eight - in the past, ten gigatons. So what we do in the U.S. really matters for global climate impacts.

SHAPIRO: So if this moment that we're looking at now is late but not too late to take action, when is too late?

EKWURZEL: I would be upset if after 10 years we did not roll out immense decisions about the infrastructure that last 50, 60, 100 years - for example, power plants, big-ticket capital items - infrastructure decisions that don't make Americans and people living in the U.S. safer and more resilient, as well as around the world.

SHAPIRO: Brenda Ekwurzel, thanks so much for talking with us today.

EKWURZEL: Thank you.

SHAPIRO: She's director of climate science for the Climate Energy Program at the Union of Concerned Scientists and one of the coauthors of the new climate report. Transcript provided by NPR, Copyright NPR.