TRNN viewers ask questions and challenge two prominent climate scientists about the relationship between increased carbon emissions and global warming
PAUL JAY, SENIOR EDITOR, TRNN: Welcome to The Real News Network. I’m Paul Jay in Baltimore. And we’re continuing our series of discussions with climate scientists, answering your questions about climate change and the environment.
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Now joining us to continue our climate-change discussion, from Paris: ValÃ©rie Masson-Delmotte is a French paleoclimatologist. She holds an engineering degree from the Ã‰cole Centrale Paris in physics and fluid transfer. Since 1997 she’s been a senior scientist at the French nuclear energy commission. She’s served on numerous national and international projects, including the Intergovernmental Panel on Climate Change.
And joining us from Colorado is Jeff Kiehl. Jeff is a senior scientist at the National Center for Atmospheric Research, where he heads the Climate Change Research section. He’s published over 100 articles on the effects of greenhouse gases on the Earth’s climate, the effects of stratospheric ozone depletion on the climate, and the effects of aerosols on the climate system. He’s also co-author of Frontiers of Climate Modeling. Thank you both for joining us.
JEFF KIEHL, SENIOR SCIENTIST, NATIONAL CENTER FOR ATMOSPHERIC RESEARCH: Thank you.
JAY: So, as you know if you’ve been watching this series, I’m reading questions that you, viewers, have sent. And here’s a question. So writer writes:
We’re already actively helping out the process and we don’t even know it. The biggest carbon sink on the planet are the oceans, and they do that because of algaeâ€”and other plant life that grow there, but mostly the algae. In modern times, we’ve started pumping fertilizers and growth aids into the water supply, causing huge increases in the rate of growth of these algae populations. This is just a side effect from us trying to feed everyone, but it’s increased the rate the oceans are absorbing and storing carbon. I think at the current rate it stores about a half to a third of the carbon we put out. If we actively try to start storing carbon, we could scrub it out of the atmosphere in 50 years.
Jeff, so what do you make of that?
KIEHL: Well, I wish it were that easy, but there are a number of problems with the argument. First of all, the oceans take up about a quarter of the carbon dioxide that’s emitted into the atmosphere by burning fossil fuels, not a half. And so the effect that he’s referring to in terms of the algal blooms, that’s a coastal phenomenon. Indeed, as we’ve increased fertilization of agricultural land, some of that fertilizer runs into rivers that then runs into oceans. And along those coastal regions where the rivers run into the oceans, you do get these blooms. But the problem is that those are fairly limited in extent, areal extent or coverage. The ocean is a vastâ€”you know, 70 percent of the earth is covered by the oceans, and it’s that vast surface area of the oceans and its ability to take up carbon dioxide that leads to the quarter of emitted carbon dioxide going into the oceans. Theâ€”I’ll just leave it at that.
JAY: ValÃ©rie, do you want to add something?
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VALÃ‰RIE MASSON-DELMOTTE, PALEOCLIMATOLOGIST, Ã‰COLE CENTRALE PARIS: Yeah, just one point. It’s the fact that for chlorophyta to grow in ocean water, there are limiting factors. One is the availability of iron, for instance. And so there are limitations to the magnitude of blooms that can take place in the open ocean. And one example is that we know from the past, based on ice core and deep sea sediment records, there were periods in the past during glacial climates when there were huge amounts of dust rich in iron that were spread in the Southern Ocean, and we know that the changes in atmospheric composition in CO2 were of the order of magnitude of about 20 ppm during these events. So this gives an idea that this type of process has a limited impact with respect to the magnitude of the ongoing perturbation.
And my last comment is the fact that in a warming climate, the processes that allow oceans to take up carbon dioxide may slow down. In a warmer ocean, the more stratified ocean at the global scale will have different physical and chemical processes, and it’s likely that the ability of the ocean to absorb CO2 will decrease.
KIEHL: It’ll be even harder for the oceans to take up carbon dioxide as we warm.
JAY: Well, given the sense of urgency climate scientists are telling us we are facing and that by the end of the century we’re talkingâ€”you know, they used to say 2 degrees would be terrible, and now I think we’re hearing the possibility of three, four, and even more degrees warming before the century is overâ€”and given the political paralysis of all of this in the sense of trying to restructure the way the world does business and produces, seems to be the pace of change is either slow to zero. I guess that’s part of why people are looking for some other alternative to reducing human-made carbon emissions and kind of focusing on what can be done, if anything, with nature to do more absorption. Jeff, is there a path there?
KIEHL: Well, certainly. I mean, this falls under the general topic of what’s called geoengineering. That is, can we develop technologies or change certain technologies so that we actually draw carbon dioxide out of the atmosphere more quickly than nature is doing now? And then, once we get it out of the atmosphere, we’d actually have to bury it somewhere so that it would stay sequestered or, you know, buried away for a very long time. If it just got back into the atmosphere on a short timeframe, we really wouldn’t be helping the problem that much.
So indeed there are different strategies people have proposed, from putting particles into the stratosphere that would reflect sunlight and therefore cool the planet, toâ€”that’s not pulling CO2 out of the atmosphere, but that is a geoengineering approachâ€”to ones that are directed at reducing the amount of carbon dioxide in the atmosphere, like increasing the number of trees or plants that would draw carbon dioxide down on the landmasses, and then the one that actually ValÃ©rie noted that we know took place in the past because it’s in the ice core records, and that is, if you threw more iron particles into the ocean, you could perhaps create these blooms that would draw down more carbon dioxide in the atmosphere. And people have proposed large-scale, you know, experiments to do that. But there areâ€”I mean, the people that have looked at this find that there are limitations, as ValÃ©rie has noted, as to how much one would expect to get from such an iron fertilization geoengineering approach.
So I’m actually somewhat reticent about investing billions to trillions of dollars into fixing the carbon dioxide, the amount in the atmosphere, because we don’t know how long the carbon dioxide would actually stay buried if we could bury it somewhere. And I’m more interested in finding ways to reduce how much we put into the atmosphere, because that’s the other solution to this, is rather than sucking it out of the atmosphere and burying it, we could perhaps figure out ways thatâ€”where we emit less carbon dioxide in the atmosphere to begin with, which would indeed lead to a reduction in atmospheric carbon dioxide.
JAY: Well, we’re going to be debating that issue in a whole ‘nother series about what to do and how to reduce carbon. But, ValÃ©rie, do you want to address this issue of geoengineering before we wind up?
MASSON-DELMOTTE: Yeah. I wanted to comment on two points. The first one is that there are technologies linked with agricultural methods and forestry and preservation of primary forests, which are carbon sinks, that can help at least to store more carbon on the land surface. But the magnitude of what should be done to control the atmospheric concentration, given the magnitude of the human impacts, is really several orders larger than what can be done in a reasonable approach. Like, reforestation is not possible, as we’re aware, because we have to produce food, for instance. You know. So there are clearly limitations on what can be done. But there are ways of doing things better than what we do now.
Regarding geoengineering, it’s very important to assess the benefits and the risks of each method that has been [incompr.] with the same way that we assess the risks linked with emissions of greenhouse gases. And one of my main worries is the following. If you continue to add CO2 in the atmosphere and make the oceans more acid, acting on climateâ€”for instance, by injecting aerosols in the atmosphereâ€”can be efficient on the short term. But if for one reason or another one you cannot sustain that effort, then you will have the cumulative effects of these greenhouse gases that will be concentrated on a very short period. So you in fact increase the risk of aggregate climate change if you cannot sustain these type of geoengineering methods.
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Thanks for joining us on The Real News Network.
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