IRA FLATOW: This is Science Friday. I’m Ira Flatow. Back in December of 2015, 195 of the world’s nations took their first steps down a long, unclear road to addressing climate change. In signing the Paris Climate Agreement, nations agreed to keep the increase in global average temperature to quote, well below 2 degrees Celsius, a critical point at which the planet gets locked into a future of catastrophic impacts, such as rising sea levels, more devastating floods and droughts, widespread food and water shortages, and more powerful storms.

And to ensure that we don’t get too close to that 2 degree tipping point, the agreement asks countries to limit the temperature increase to just 1.5 degrees Celsius. But how much does half a degree save us from the most devastating impacts of climate change? A new report from the Intergovernmental Panel on Climate Change– the IPCC– this week has shed some light on that. It highlights a number of climate change impacts that could be avoided by limiting global warming to 1.5 degrees compared to 2 degrees or more.

The conclusion, every bit of warming– even that 0.5 degrees– matters. Here to break down the report and tell us how world nations have been doing trying to curb emissions over the last three years is Dr. Kelly Levin. She is senior associate with the World Resources Institute. Dr. Levin, welcome back to Science Friday.

KELLY LEVIN: Thank you so much. Great to be with you.

IRA FLATOW: We want to send out a shout out to our listeners with this question. As we barrel toward a one and a half degree increase in global temperature, are you worried? Are you worried about climate change impacting where you live?

Give us a call, our number 844-724-8255, 844-724-8255. You can also tweet us @SciFri. So Dr. Levin, the goal is to prevent a 2 degree increase in average global temperatures. But this report tells us that even a 1.5 degree increase is going to bring some pretty big changes.

KELLY LEVIN: Yeah, that’s absolutely right. So the Paris Agreement actually has these two goals, as you said, to limit warming well below 2 degrees, and pursue efforts for 1.5 degrees Celsius of warming. And that was because for some of the most vulnerable countries– you can think about small island developing states– 1.5 degrees Celsius is also going to harm well-being to a tremendous extent.

So what this report did was look at what are the differences between warming of 1.5 degrees Celsius and 2 degrees Celsius of warming? And how much harder is it to get to 1.5 degrees Celsius as opposed to 2 degrees Celsius? And they found that indeed, we are definitely not on track. And the half a degree of warming actually can make a tremendous difference.

IRA FLATOW: For example?

KELLY LEVIN: So for example, what they’ve found is they looked across a number of different systems, and they found for example, for extreme heat, the percentage of the global population exposed to a severe heat wave, which we’ve already started to experience with one degree of warming, at least once every five years is 2 and 1/2 times worse with two degrees of warming instead of 1.5 degrees Celsius of warming. If you think about sea ice free arctic in the summer, when you don’t have any ice on top of the Arctic, this could happen at least once every 100 years with 1.5 degrees Celsius of warming, but at least once every decade under 2 degrees Celsius of warming. And that can impact climate change even further, because you have a dark service that opens up underneath the ice and it absorbs more warmth.

Sea level rise is 0.06 meters more with 2 degrees as opposed to 1.5 degrees. And while that doesn’t sound like a lot, that translates to millions more people being impacted. Species loss is two times worse for both plants and vertebrates that lose at least half of their range under 2 degrees of warming as opposed to 1.5 degrees of warming, three times worse for insects. Almost 40% worse under 2 degrees versus 1.5 degrees for the amount of permafrost that would thaw in the Arctic.

So these are some really big numbers. One of the most devastating and surprising ones to me was for coral reefs where the report found that under 1.5 degrees Celsius of warming, we would see 70% to 90% of a further decline in coral reefs. With 2 degrees, more than 99 percent, which is just tremendous.

IRA FLATOW: Does it look like there’s any way we’re going to be able to stay under that 2.0 degrees?

KELLY LEVIN: So what the report finds is that both 2 degrees Celsius of warming and 1.5 degrees Celsius of warming is technically feasible. There have been a lot of modeling studies where analysts come together and see what would have to happen to make that transition happen. Right now, emissions are roughly 52 gigatons of carbon dioxide equivalent. They’re projected to increase, even with the climate change commitments that we’ve made under the Paris Agreement, by 2030.

Instead, we essentially need to halve that amount and go down to 25 to 30 gigatons of carbon dioxide per year by 2030. And then we actually need to phase out net emissions altogether by mid-century. So this is a tremendous transformation and decarbonization rates that are truly unprecedented at the scale of what we’re talking about.

It also would require behavioral and technological shifts across the board. So for example, by 2050, we’re talking about renewables projected to supply 70% to 85% of electricity to be able to meet 1.5 pathways. We’re talking about reducing energy demand, increasing the efficiency of food production, changing dietary choices, a lot of different measures which we’re just starting to do in certain locations, but not at the scale we need.

IRA FLATOW: You know the president said he wanted to know, quote, who drew the report. I won’t go there with that. Can you answer at least who commissioned it, what data they use?

KELLY LEVIN: Sure. So the way that the IPCC works is in this particular case, under the Paris Agreement, there was an accompanying decision. And that decision requested the IPCC– the Intergovernmental Panel on Climate Change– to put this report together. And what the scientists do– they commissioned about 100 different scientists. And had a very lengthy review process, of several different drafts being publicly reviewed. And I was one of the reviewers for that. The scientists basically assess all of the recent literature– and in this case, on 1.5 degrees Celsius– and see what the science says– up to a certain cutoff point, where the literature is published. And then they put together a detailed technical analysis.

Interestingly, in this case, there’s an accompanying summary for policymakers, which was agreed upon in Korea about a week ago. And that, all of the governments signed onto, including the United States. And that is actually something that negotiators come, make sure that they feel comfortable with the implications for policymakers. So in this case, part of the answer is that the United States did actually endorse this report.

IRA FLATOW: We have a lot of people who want to talk about it. I’m going to go to the phones, to Janice, in South Carolina. Hi, Janice.

CALLER: Yes, hello. So I’m agriculture. And I think what ends up confusing people, when you talk about 1.5 degrees, people aren’t real excited about it. What really hurts us in agriculture is the high temperatures– the record highs. So for example, in the Midwest, if corn gets over 95 degrees Fahrenheit at night it kills the pollen, and greatly reduces yield. Or in the Central Valley of California, when tomatoes– when the temperatures get very high, over 100 degrees, that kills the pollen. And so this is really critical, the highs, not just the average temperatures.

And we can fix this by growing more plants. That’s what the Little Ice Age was about. The North American forest grew back, for 150 years after Columbus. And all these trees took so much CO2 out of the atmosphere it cooled the planet off so much we had a Little Ice Age. And I wish more of the scientists would talk about that. Because we can substitute a lot of our renewables– can be biofuel, biogas, other things like that, that will make us grow more plants. And we can have them for food, feed, and fuel.

IRA FLATOW: Are you a farmer?

CALLER: No, I’m an ag researcher, actually, but I have a small farm. And I’m the developer of the Energy Tuber, which makes food, feed, and fuel– all on the same acre. And it uses little water and nitrogen. You know, everybody thinks we’re going to have some– you know, put CO2 into the atmosphere. All the plants will take it up, if we switch to the renewables using plants.

IRA FLATOW: All right. Let me get a comment. Thanks for your call. What about that? Can we suck some of the CO2 out, and reverse some of this?

KELLY LEVIN: Thanks. Some really good points here. I think, first, as you had mentioned, the 1.5 degree goal is for global average temperature increase. So temperature increase at any one location, especially on any one particular moment in time– as well as its impacts– are going to vary. And that’s an incredibly important point.

Interestingly, the report does talk extensively about carbon removal. And says that not only do we need to pull out all the stops on emission reductions, but we actually have to remove carbon from the atmosphere– and at a scale that we need to ramp up significantly.

The models do look at the different ways in which that can be achieved. Some of them are with afforestation, for example– with planting trees. There are a number of technological options for carbon removal. For example, bioenergy, plus carbon capture and storage– where you use bioenergy and capture some of the carbon associated with it, and store it.

Also, direct air capture and storage. Where, basically, these are huge machines, that you have air passing through. You collect the carbon dioxide, and then you store it. There are some challenges with bioenergy, and bioenergy plus CCS. And it’s important to ensure that bioenergy crops don’t displace other land uses, so that they have the carbon effect– and don’t raise food prices and disturb ecosystems. But, certainly, managing our lands and soils in a way that they can suck out carbon much more efficiently is going to be critically important.

IRA FLATOW: But we’ve talked about energy usage in the past. It’s cheaper to make things more efficient, so they don’t use up as much energy, than it is mitigating the problem later. Is the same thing true of carbon? It’s better to keep it from being emitted– it’s much more efficient to do that than to try to suck it out of the air later?

KELLY LEVIN: That’s for sure. Absolutely. Certainly, reducing energy demand, energy efficiency, these are all going to be critically important. Efficiency of industrial processes, and changing some of the behavioral changes that would lead to a more low-carbon society, would be very critical.

IRA FLATOW: I’m Ira Flatow. This is Science Friday, from WNYC Studios. I mentioned some of the things we’re watching now– rising sea level, and the levels. We have more devastating floods. And we had a hurricane, that’s now gone off the scale this week, for some measurements. Are we not seeing, is it not fair to call these consequences of climate change, or evidence, more or less, of climate change?

KELLY LEVIN: Absolutely. I think what’s important– and I think one of the reasons why this report is really hitting home to people is that everyone is seeing the devastating impacts of just one degree of warming. And now we’re talking, with current climate change commitments– even if they were fully implemented– were slated for 2.7 to 3.7 degrees Celsius of warming. So that’s a world that we don’t know what that looks like.

Certainly, that’s better than without the climate change commitments. But we are talking about tremendous changes across systems. And certainly, we have lots of evidence that the impacts unfolding around us have human fingerprints. And we can see the impacts of human activity in a number of different changes, including in storm activity– in terms of the amount of time that storms are sticking around, in the Atlantic– the frequency, the intensity of storms. The sea-level rise basically gives a higher onboarding for coastal inundation. So we’re definitely already seeing a lot of impacts unfold around us.

IRA FLATOW: The amount of rainfall that’s coming out of these–

KELLY LEVIN: That’s right.

IRA FLATOW: –storms. It’s just amazing. But you scared me a little bit when you just said, we don’t even know what it would look like above a 2 degree Celsius increase.

KELLY LEVIN: So what we do have is we have some models, that look at what the projected impacts would be. And for some of these impacts, we have more certainty. And for others, we have less certainty. There are also these so-called wild cards, that probably are low probability, but would have very high impact. And where those thresholds lie, for some of those, we are not completely sure. So if you think about shifting of ecosystems from a tropical forest to a Savannah-like state, because you have such extreme drought, that would be not only catastrophic for the ecosystem, and biodiversity, and services, but also for carbon– for carbon storage.

IRA FLATOW: I’m frequently struck by people who say, you know, it’s going to cost us money. It’s going to cost taxpayers money to implement some of these things we’re talking about. But the other side of the argument never gets talked about it– what’s it going to cost in terms of lives, and capital, and movement of populations and farming, if we don’t do any of these things? it’s so totally unbalanced on the other side.

KELLY LEVIN: That’s absolutely right. And, interestingly, the report found that economic losses are actually much greater as temperatures rise. And with middle-income countries– so in Africa, Southeast Asia, India, Brazil, Mexico– projected to be affected the most, they looked at global GDP losses for 1.5 versus 2 degrees. And found that it was significantly different. A lot of these losses sometimes aren’t even in the calculations to begin with. And, certainly, if you have short-termism, where you don’t value later economic impacts, as well as those that are harder to quantify, it doesn’t get into the equation.

IRA FLATOW: So we’ll just have to wait and see what happens, because it’s not a pretty picture, the way we’re headed.

KELLY LEVIN: It’s not a pretty picture. But there’s a lot we can do, and we must do. First, in terms of the international process, governments in 2020 are invited to up their commitments, and to increase the ambition of their commitments. And that’s going to be really important.

What we know is the current commitments are not good enough, to get us on track. So I think making sure that there is an expectation and a pressure for governments to do that. But also, for people not to throw up their hands. Because there is an incredibly important role for everyone to play– not only governments, but the private sector. And also, individuals– and a lot of different things that individuals can do, for sure.

[INTERPOSING VOICES]

IRA FLATOW: What’s the single biggest thing an individual can do?

KELLY LEVIN: I was going to say, the single biggest thing is to get out and vote. Because I think we need to make sure that decision makers are taking climate change incredibly seriously, and really turning the emissions trajectory around.

IRA FLATOW: Get out there and vote. Thank you very much, Dr. Levin. Dr. Kelly Levin is a senior associate with the World Resources Institute. Thanks for taking time to be with us today.

KELLY LEVIN: Thank you.

IRA FLATOW: Charles Bergquist is our director. Senior producer, Christopher Intagliata. Our producers are Alexa Lim, Christie Taylor, and Katie Hiler. We had technical and engineering help from Rich Kim, Sarah Fishman, in New York. And Duncan Lively, here at KCLU. We want to thank all the great folks here at KCLU, who made us feel so welcome in their studios today.

We’re active all week on Facebook, Twitter, Instagram– all the social media. You can even ask your smart speaker to play Science Friday so every day, sort of now, is Science Friday. In Thousand Oaks, California, I’m Ira Flatow. Have a great weekend.

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