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Scripps: Black Carbon Levels Linked To Climate Change Declining

black carbon
Scripps: Black Carbon Levels Linked To Climate Change Declining
GUEST:Veerabhadran Ramanathan, Professor of climate science, Scripps Institution of Oceanography, UC San Diego

CAVANAUGH: Our top story on Midday Edition, the effort to clean up California's air may be helping in the effort to slow down climate change. A new study reports that the reduction of black carbon or soot levels since the 1980s is comparable to taking four million cars off the roads. It has been the focus of much research by my guest. Ran Ramanathan is a distinguished professor of life and climate sciences at Scripps institute of oceanography. He led the study on the impact of black carbon on California's climate. RAMANATHAN: Thank you very much for having me here. CAVANAUGH: I'd like you if you would to explain your focus on black carbon as a contributor to global warming. What is it and what produces it? RAMANATHAN: They used to call them soot. It's basically the dark stuff which comes out of diesels and fires. It's basically soot. One of the major components of that is what we call black carbon. It is the black carbon, a solid particle, that's what gives color, the dark color. And it's dark because it absorbs most of the sunlight hitting it. It's one of the most per pound, most efficient trappers of sunlight. So it heats the air directly. But it also has immense health effects. CAVANAUGH: And largely the efforts to contain and reduce the amount of black carbon or soot in the air has been to improve the air quality. But you also find that black carbon plays a role in global warming. What kind of a role? RAMANATHAN: This is most of what we have done over the last ten years, using satellites, ship observations and aircraft, we have discovered is that it is the second largest contributor to global warming next to carbon dioxide. And that's the bad news. The good part of it, in its lifetime is only about two weeks. It's removed by rainfall. Just falls on the surface. So as a result, if you take actions to cut that down, they're gone within a few weeks. The effects on public health is gone in a few weeks. And so it's very effective on global warming. CAVANAUGH: So it has a short lifetime. But how much do we produce? Is black carbon one of the big pollutants produced worldwide? If you look at it in terms of actual mass of what we produce of black carbon, that's put out in the air, in terms of climate, the mass is not the key issue. But nevertheless, it's on the order of millions of tons per year. To be compared to 30 billion tons of carbon dioxide we put out. However, 1 ton of black carbon has the same effect as the 1,000 tons of carbon dioxide. So we can't get fooled by the actual mass. But at the same time, we should talk about there's a climate effect, there's an air pollution effect, in terms of transportation from diesel, black carbon is the major source of particulate pollution. So it's got two diabolic effects. CAVANAUGH: Now, we -- when we speak about climate change, we hear almost exclusively the emphasis on CO2 emissions. Why don't we hear more about these other pollutants? RAMANATHAN: For a very good reason. Once we put the CO2 in the air, for example, I drove from my university to come to your studio, 50% of the carbon dioxide will stay for a century. 20% stays for 1,000 years. So carbon dioxide accumulates, and if you're focused on long-term climate change, 50-100 years from now, we have to start cutting carbon dioxide now. But as you know we are in a grid lock. We don't know how to bring it down. Political reasons. But there is a knob we can dial down. That knob has four pollutants, one is black carbon. And this is where California, the California story is one of the best news I have had in 35 years of research, there are technologies to cut them down now and immediately. So there is a hope for slowing down global warming while we are figuring out how to bring down carbon dioxide. CAVANAUGH: We're about to start really talking about this study you oversaw about the impact of black carbon on California's climate. So what did your study find about our efforts to reduce these emissions in California? RAMANATHAN: The study was conducted three institutions, university of California San Diego, the Lawrence Berkeley laboratory, and another DOA lab in Washington state. What was remarkable about this study, we started to look into what role this black carbon is playing in present climate. That was our focus. Then we started digging into the data, we found this rapid decrease over time so we focused on that. We found is that California had excellent monitoring stations, otherwise we couldn't have done the study. So we found from 1980s onward, California's black carbon concentration had come down by a factor of 2. Then we had other data to go back in time, visibility type studies. So we went back in time to 1960. And we were really surprised. It was a huge, pleasant surprise. It was cut by 90% from the 1960s. And what was remarkable about that is that is that 90% reduction was not because we asked people to stop driving. We improved the technology. We improved the fuel. So the actual diesel consumption went up by a factor of 4, but the pollution went down by 90%. So that was -- yeah. CAVANAUGH: I'm just wondering, so if I'm understanding this correctly, if we had been considering the amount of population increase and so forth, if we had been admitting as much black carbon per unit, per diesel engine today as we were in 1960, we would see a profoundly increased climate change in our little section of the world, and we would have contributed to the rate of climate change throughout the world. RAMANATHAN: Excellent question. If we had used the same technology since 1960s, continually increased use of diesel combustion, the amount of soot in the air would be a factor of 10 larger. What an order of magnitude! And we would see our skies, brownish skies everywhere. And the heating from that, we found already the black carbon in 1960s heated the air by about 3-4% more. But the scary scenario you're proposing, if we continued that, yeah, that could have made a huge massive heating of the air. We would have seen our snow packs impacted because black carbon settles on the snow pack and directly melts it and makes it darker. And I think the more devastating part would have been the number of premature deaths you would have witnessed. CAVANAUGH: Today we just heard the U.S. Supreme Court has limited an effort at the L.A. port district to redistrict the use of old dirty diesel trucks, which produce smog, black carbon. Is that kind of a ruling, do you see that as a setback? RAMANATHAN: Well, I need to know the details of it to see what in place they were proposing. But I can say based on scientific evidence, ships are a major source of soot, black carbon, we know that. The black stuff comes out of ships. And the second thing is, trucks and vehicles parked in a place with the engine on is a major source of diesel combustion. So that's what I need to know, what they said. If a massive amount. Diesel trucks are parked next to the port with engines on, it is a huge health hazard. CAVANAUGH: And now you've got the numbers to show that these clean air carbon-reducing restrictions actually have an impact. RAMANATHAN: Oh, it's a huge impact. Yeah. CAVANAUGH: A few years ago, doctor, you produced a list of some relatively simple efforts that people and nations could do to dramatically reduce the level of short-term climate changing pollutants. And I wonder where that's gone. I know that open-fire cooking was on that list. This was a global initiative that you took. Do you feel that your efforts have been heard? Have they been -- had any success? RAMANATHAN: Thank you so much, Maureen, for asking this question. In terms of the shortlived climate warmers, black carbon is one, methane, and the HFCs used as refrigerants. And I am pleased to tell you in large part, not only my work, but work done at the university of California San Diego, Secretary of State Hillary Clinton from this climate and clean air coalition last year, and now it has membership of over 30 nations. The World Bank has joined. The European Union has joined. And we just heard last week President Obama and President Xi from China signed an agreement to phase down one of the important shortlived climate pollutants, HFCs. So I am amazed at how fast things are moving. I'm very hopeful we're going to be able to slow down climate change. CAVANAUGH: You're very hopeful about that. Do you have any estimates on how much we might be able to slow down climate change? RAMANATHAN: Yes. So just targeting, let's start one by one. If California's experience, technology and policies can be replicated worldwide for diesel transportation, that alone could slow down global warming by about 15%. And if President Obama, President Xi's agreement of the phase-down is joined by other countries, India, Brazil, and Europe, that will give us another 10%. So all these nickels and dimes start adding them. And then methane, the sad thing about methane is so much of it leaks from our landfills and our Mira Mar airforce has taken a pioneering role taking the methane out of the junk and using it for power. So methane alone, that would give us another 50%. So we can slow down global warming by about 50% within the next 30, 40 years. And the other 50% has to come from carbon dioxide emissions. We are on track to -- unfortunately, we have already put another global warmers out there in the air. The planet is going to heat up by about 2 degrees by the end of the century. Sadly, that's something we don't see how that could -- but we can keep it under that 2 degrees. And that is where these other pollutants -- and fortunately the political leaders are able to grasp on this short-lived climate pollutant -- there is traction there. From the bottom up. My own initiative has been one of the major sources of soot is residential, cooking with firewood and cow dung. It's a shocking statistic. 3 billion people in the world have no access to fossil fuels. So they burn whatever they can get their hands on. And if you can provide them clean cook stoves, you not only solve their poverty problems, their standard of living, but four million die every year inhaling the smog. So the short lived climate pollutants is really a story of short solutions. CAVANAUGH: Thanks so much. RAMANATHAN: Thank you.

The effort to clean up California's air may be helping slow down climate change.

A new study commissioned by the California Air Resources Board finds that the reduction of black carbon, or soot levels since the 1980s is comparable to taking 4 million cars off the roads of California.

The study examining the impact of black carbon on the state's climate was led by professor of climate and atmospheric sciences Veerabhadran Ramanathan at Scripps Institution of Oceanography, UC San Diego.


"If California's efforts in reducing black carbon can be replicated globally, we can slow down global warming in the coming decades by about 15 percent, in addition to protecting people's lives," said Ramanathan.

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