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Ken Caldeira - Carnegie Institute - Stabilizing Carbon Emissions Only Option
Posted on 29 Feb 2008
Ken Caldeira talks to Beyond Zero Emissions about his latest study on zero emissions as soon as possible being the only safe target for our policy makers, our public and the planet.
Ken Caldeira podcast
Miwa Tominaga: This morning on Beyond Zero we're interviewing Ken Caldeira of the Department of Global Ecology at the Carnegie Institution of Washington. He is the author of the first peer reviewed study to be published in the Geophysical Research Letters which investigated what level of carbon dioxide emissions would be needed to prevent further warming of our planet.
Ken Caldeira: Good Morning.
Scott Bilby: Could I just ask you an opening question? My name is Scott. Last week on our show we talked to James Hansen and he's calling for a range of emissions somewhere between 300 and 350ppm. He said that's what we need to start cooling the planet. What are your views on that?
Ken Caldeira: I think it's very difficult to specify specific targets for atmospheric CO2 concentrations. The way I look at it is that each CO2 emission produces additional environmental risk. There is a lot of uncertainty in the climate system. We don't know exactly how much the Earth will warm as a result of a doubling of CO2, we don't know exactly when the ice sheets will collapse, we don't know when we will lose the arctic biome and we don't know when coral reefs will disappear exactly, but we know that each emission of CO2 brings us a little bit closer to each of those events. So rather than focusing on specific stabilisation targets I think the science is increasingly pointing to the idea that we need to try to eliminate carbon dioxide emissions as rapidly as we can and I don't really think in terms of stabilisation targets, I think in terms of emissions targets and I think the right emissions target is zero.
Scott Bilby: The right emission target being zero, do you agree with the idea that with the melting of the arctic ice we've already passed the tipping point so that even ultimately zero emissions will not be enough.
Ken Caldeira: I'm not an expert on ice sheet dynamics. I know there are some experts who think that southern Greenland at least is already collapsing and there are others who disagree with that. But to me that says at least that the southern Greenland ice sheet at the very minimum is at a great risk of collapsing. The way I see it is there's just so much uncertainty in the system that we can't predict with any confidence what the environmental consequences of our CO2 emissions will be. So, a risk averse or environmentally prudent strategy would say, 'Well, if we don't know what the result of doing this is going to be then we shouldn't do it.'
Philip Sutton: Hi Ken. It's Philip Sutton speaking, I was just wondering, you mentioned earlier that we need to fairly rapidly bring down the CO2 emissions and presumably other greenhouse gas emissions as well. Do you have a sense of the appropriate speed for that, or is it a similar thing to what you're saying about the emissions targets, that it's just better to do it faster than slower?
Ken Caldeira: Well, if it was up to me, and no one has appointed me king of the world yet...
Matthew Wright: Well, we'll give you a nomination.
Ken Caldeira: I think an appropriate analogy is World War II. In World War II we started that war flying biplanes and in response to the Nazi threat we developed jet air planes, integrated circuits and radar and in the space of just a few years had a real transformation of a wide range of technologies.
I think if we would take this problem with the same sense of gravity, that within just a few years we could develop the necessary technologies. For example electric cars, they basically exist, and even with existing batteries, instead of having gasoline filling stations, you can have swappable batteries where you swap out an old battery and put in a new battery. And there's no reason why we need to making any more gasoline powered cars even today.
While there does need to be technology development, if people knew they just weren't allowed to build carbon emitting devices, cars, power plants, etc. that emit carbon dioxide, that would be great incentive to develop the new technologies.
I don't know whether it should be next year or 5 years from now or maybe 10 years that we don't make any more CO2 emitting devices, but it should be within the next couple of years we should ban it. I mean it should basically be against the law to make anything that emits carbon dioxide into the atmosphere.
Philip Sutton: Yes, I think that makes a lot of sense. In the work that we've been doing, we've been looking at the Arctic sea ice melt as a bit of a reference point. And we've tried to get some estimates of the likely increased warming that might trigger. And at the moment a number of people we've talked to in the scientific community think about a third of a degree globally might be relevant. In other words, we might get an extra third of a degree from losing, or getting the albedo ice flip. What we are wondering is, how quickly you'd have to change the system to actually recover the arctic ice.
According to the Naval Postgraduate College people, we could lose the Arctic ice completely within possibly even as soon as 5 years time. Doesn't seem to me that that's a very good situation to stay in in terms of the stability of the Greenland ice sheet. Obviously we don't exactly know how long Greenland will take to melt but if you get an extra warming from the albedo flip in the Arctic, that will be a problem. One of the questions I guess I've got for you, because you've gone on record about issues of using geo-engineering, and a lot of people react with caution to that of course; I was just wondering if you did a very fast reduction in CO2 emissions, in other words we stopped using fossil fuels in power stations and cars and what have you, presumably we'll get a quick reduction in the aerosols, the soot and the dust and what have you, then a slower reduction in the atmospheric levels of CO2, and I'm just wondering whether that spike would need to be offset in some way?
Ken Caldeira: Again, I think the climate system is very difficult to predict, but you're right that if we were to go cold turkey today and just turn off every power plant, that the immediate response of the system would be to warm things up, as the sunlight reflecting aerosols, the sulphate aerosols, that power plants emit fell out of the atmosphere. We did a calculation that actually the average coal-fired power plant cools the Earth for about the first 7 years because it's sulphate emissions have a cooling influence more than the CO2. But then after seven years the CO2 accumulates enough to overwhelm that sulfate cooling, and then of course the CO2 levels remain high in the atmosphere for many thousands of years. So you're right there'd be a short term warming.
Now with regard to geo-engineering, the thing that I'm most afraid of with geo-engineering is not really the direct climate effects but its political effects. That if people see it as an alternative to emissions reduction then I'm against it. So as long we're building coal fired power plants and building big sports utility vehicles and things like that, that if you do geo-engineering under those circumstances it's just allowing those people, allowing us, to continue living that kind of way, living in a CO2 emitting energy economy. And so I think I would be against geo-engineering, unless we are already pretty far along the road to eliminating CO2 emissions and then decided that that's not enough to prevent the environmental problems.
One thing about ice sheets is they take a while to collapse and so if it's just a decade of warming and then you cool again, with ice that's not going to be time enough to melt the ice sheet. You're right though that if you stop CO2 emissions completely the Earth will warm somewhat and that warm state will last many centuries, so it is a concern.
With regards to even the sea ice, I was at a meeting a couple of months ago and the question of once the sea ice melts, if you cool things off, how much would you need to cool things off to bring the sea ice back, if things have already warmed up enough to melt the sea ice? And there's some dynamicists who think with the melted sea ice, that the winds would change in a way that would result in dynamical effects blowing the water in ways that would prevent the sea ice from returning until the Earth got much cooler, and again other people think the sea ice would come back as soon as you cooled things down again. So there is great uncertainty about what would happen with that system and whether it's metastable.
Philip Sutton: Seems like that might be a subject for some fairly urgent research to get a handle on that.
Ken Caldeira: You would think that there would already be big research programs addressing those kind of issues. As far as I know there's certainly been no published study on the metastability of the Arctic sea ice and you know I was in this meeting with some of the top scientists from around the world and it was the subject of idle speculation and nobody had really done simulations to really nail it down.
For one thing, the Arctic ocean is pretty poorly represented in most climate models. A lot of our climate models are grids that converge at the north pole and that presents numerical problems in simulations and there are other models that don't do that but often the Arctic ocean's not that well represented in the models.
Matthew Wright: We're interested in particular about the study you've published in the Geophysical Research Letters Journal titled, 'Stabilising Climate Requires Near Zero Carbon Emissions' and that's been released I think this week in the United States.
Ken Caldeira: I don't have the timeline yet, but the actual publication date got pushed back because it took them more time in production than we thought. It's coming up March 7th now.
The basic idea of that paper, and we've all seen curves of how when you emit CO2 into the atmosphere at first the concentration is high but then it gets absorbed by the ocean and the land biosphere the concentration in the atmosphere goes down, and then I'm involved in another project looking how long it takes. So within some decades to a century a good fraction of that gets removed from the atmosphere, then that remaining portion that's in the atmosphere takes many thousands of years to go out of the atmosphere and so most people have assumed that the warming influence of a CO2 emission will follow that same curve, that there'd be a lot of warming at first then it would rapidly diminish so that on a century time-scale there wouldn't be much warming from any individual release of CO2.
But what we found was something very much different, that the ocean is a large body that can absorb a lot of heat, and in order to heat up the atmosphere you really need to heat up the ocean. And when CO2 is first emitted to the atmosphere it traps outgoing heat radiation and that trapped heat at first mostly goes into warming of the ocean.
So it takes a few decades for the ocean to warm up and then once the ocean is warmed up, when you warm the entire ocean through the time-scale, for the entire ocean to cool off is about 1000 years or so. Our simulations only went out 500 years. At the end of 500 years you more or less have as much warming as you had as the maximum warming after the CO2 emissions, so this idea that a CO2 emission warms the Earth and then in a century, or two centuries, it's mostly away, it's really the wrong picture. It's more accurate to say that each emission of CO2 produces an increase in temperatures which remains pretty much level for many centuries and then decays away over many thousands of years.
In a way that kind of simplifies the discussion because each increment of CO2 emission leads to another increment of warming, and so it's obvious then if each CO2 emission leads to another increment of warming then if you don't want more increments of warming then you can't have any more CO2 emissions. It's pretty straight forward.
Scott Bilby: Ken, Scott again, recently the United Nations Environment Program said that, in a similar theme, what we do over the next decades has the potential to affect ocean chemistry for tens of thousands of years and marine life for millions of years. Can you...
Ken Caldeira: You know why they said that? Because I was just at the UN Environment Program in Monaco and I was the one who said that.
Scott Bilby: Ah ha, that's fantastic! So can you tell us a bit about the acidification of the oceans and how it affects some of the marine life there?
Ken Caldeira: Yes, you know just to go do a little bit of background. For my dissertation work, I looked at what happened to ocean chemistry at the time when dinosaurs became extinct. At that time a meteorite slammed into the Yucatan Peninsula and released all kinds of sulphur and carbon compounds that reigned down on the ocean and acidified the surface ocean and coral reefs disappeared along with many other marine organisms. And it took around 2 million years for coral reefs to come back and so my dissertation work was really looking at what happened after that major extinction event.
And then just because I was working at a Department of Energy Laboratory and we were looking at the possibility of storing carbon in the ocean and people were doing studies on what would be the biological affects of putting carbon in the ocean and the original studies thought maybe while right next to the nozzle where somebody was releasing CO2 things would be bad but once it was diluted things would be ok. But the experiments showed that even at low concentrations carbon dioxide was deleterious to the growth of many marine organisms. Even the relatively dilute concentrations that are found near the surface ocean as a result of the ocean absorbing CO2 from the atmosphere would be enough in several decades, I think, to make the ocean acidic enough such that there would be no place in the ocean left with the kind of chemistry where coral reefs were found growing naturally before the start of the industrial revolution.
And since I come from a geologic background, the first question is 'when was the last time that ocean chemistry changed as much as we may do in the coming decade if we don't change our emissions habits?' I think you need to go back to the extinction of the dinosaurs to find something comparable. When atmospheric C02 changed in the glacial - interglacial cycles of the ice ages, right now atmospheric CO2 is increasing about 100 times faster than the rate during those glacial, interglacial cycles and if we were emitting the carbon dioxide 100 times slower than today, then maybe the natural buffering systems of the oceans could maintain ocean chemistry in some kind of buffered state. But when we're putting out so much carbon dioxide the surface waters don't even have time to reach the sediments and get buffered and so we're just loading all this CO2 into the system and it's experiencing a pH change that I think it hasn't seen since the dinosaurs became extinct.
And what happened at that time with the corals, actually a lot of the individual species, nearly half the species survived, but they survived not as reefs, they survived maybe as individual polyps or small, tiny things in other eco-systems, and we're just inferring this because they don't show up anywhere in the geologic record. But it took something like 2 million years for them to repopulate the coast, so there's an ecological time-scale of the coral reefs re-establishing themselves, and my modelling work which I did for my dissertation looked at what's the time-scale for chemical recovery of the ocean after an event like that and the time-scale is some tens of thousands of years. And I'm involved in a project right now that's trying to quantify that a little better. It looks like it will take tens of thousands of years, or at least many thousands of years, for the ocean chemistry to more or less recover from what we're doing but the evidence at least from the geologic record is that at that time it took the plankton around half a million years to re-evolve its eco-systems and it looks like it took the coastal ecosystems around 2 million years to come back. So what we're doing in the next decade, as I said in Monaco last week, that it will affect ocean chemistry for tens of thousands of years and will affect the marine biota for millions.
Also when it comes back, I mean when the dinosaurs became extinct, mammals came in. So when I say come back, it's not necessarily the same eco-systems coming back. Things are killed off, we open up new niches, and other species come in and so maybe we achieve the same levels of biodiversity at some point. And the geologic record suggests it takes around 10 million years to achieve the same level of biodiversity that existed before a mass extinction event. Basically, I see us as generating a mass extinction event, that you need to go back to something like the extinction of the dinosaurs to find something more dramatic. And it's not just climate change, of course it's also land cover change, chopping down the rain forests and replacing that with pasture land.
Scott Bilby: Yes yes, we certainly as humans we seem to be making a lot of changes in a wide variety of areas. Just for listeners I'll say that you're on Beyond Zero, a climate change awareness program, the time is 8:55am and Philip, I believe you have a question for Ken?
Philip Sutton: Ken, just going back to your comments about how quickly the temperature would actually revert to normal after the CO2 emissions fall. In the current situation where we are right now, do you have a sense if for example we were able to magically wave a wand and cut our emissions to zero in ten years, do you have a sense from your modelling work, how long it would take for the temperature to actually fall down to a safe level.
Ken Caldeira: I don't know exactly you call a safe level, but if we were to cut emissions to zero today I think 500 years from now it would still be almost as warm as today. Maybe at least 80% as warm as today and that it would probably take well over a 1000 years after that to get down to half that amount of warming. I don't know what you consider safe or dangerous, but I think the timescales that we need to think about is that the temperature as a result of CO2 emissions more or less stays constant for a century then trails off over 1000's of years.
Philip Sutton: If you also were to draw down actively, humans took action to draw down CO2 for example, by production of biochar on a huge scale, how much would the temperature then respond? For example, if you could take 20 or 40 parts per million of CO2 out of the air, would you find the temperature then following that down reasonably fast?
Ken Caldeira: Yes, you would because you can think of, in the same way that the positive emission, and positive in the sense of a plus sign, warms things up for a couple of decades and then stays warm for a long time, if you remove CO2 from the atmosphere that would have the effect of cooling things down over a couple of decades and then you know would remain cool for a long time. And so it would take some time, in the order of decades, for the climate system to fully respond to withdrawing CO2 from the atmosphere.
Philip Sutton: Ok, there's a bit of hope for us there.
Ken Caldeira: I had an opportunity to brief some congressmen, this was now a couple of years ago on this issue, and I was asked the same questions about the stabilisation targets that you started off with and I said the same thing about we need to think in terms of emissions targets. And they said, 'Well, what's the right emission target?' and I said 'Zero', and they laughed and I said, 'If you think emitting carbon dioxide is wrong, then zero is the obvious target', and I used a metaphor, I said, 'look, if you think mugging little old ladies is wrong, you don't ask, oh what's our target for the rate of mugging little old ladies, you say well, we think it's wrong and we're going to try to eliminate the rate of mugging little old ladies and I think it's a similar thing'.
Scott Bilby: Ken, unfortunately we've run out of time, and we've got people from the next show madly looking at us through the window,wanting to get in, we're trying to batten down the hatches here and keep them out, but they're going to get in and do their show anyway. So, we'd like to say thank you very much for that interview, it's been wonderful talking to you and we'd love to get you on the show again sometime.
Ken Caldeira: Sure.
Scott Bilby: Thank you very much.
Ken Caldeira: Ok, great, thanks a lot.
All: See you then.
Miwa Tominaga: You've been listening to Beyond Zero, a climate change awareness program aired weekly on 3CR community radio at 8:30am and from myself, Scott, Matthew and Philip I'd like to say good bye.
Transcript by Ana
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