Just about two years ago, Chemistry Nobelist, and atmospheric scientist Paul Crutzen opened a huge can of worms by suggesting that, since the world doesn’t seem to be getting its act together to significantly reduce CO2 emissions, it would be prudent to think about emergency measures in which we engineer ourselves out of the crisis by monkeying directly with the Earth’s solar radiation input instead of dealing with the CO2 content of the atmosphere. The specific proposal was to inject chemicals into the stratosphere that would form sulfate aerosols and hence block sunlight. Crude estimates suggest that the aerosol fix (if it is indeed a fix and doesn’t create more problem than it solves) is more technologically feasible than sci-fi dreams of sunshades at the Lagrange point. Not to say technologically feasible, necessarily, but not so far out as the other schemes. Crutzen’s idea, and related geoengineering proposals, have been discussed here on RealClimate. The subject is once more in the news, thanks to this chipper little op-ed by Ken Caldeira, which appeared in the New York Times this week.
Update: I just noticed that our original RealClimate piece was done before Crutzen’s article was published. You’ll find his article here (subscription not required).
The attraction of the proposal is that we are already conducting an uncontrolled experiment on aerosol-based geoengineering, through the sulfate aerosols injected into the troposphere by dirty coal plants. Along with a lot of nasty health and environmental consequences, this has had some inadvertent benefits in restraining some aspects of global warming. As coal plants get cleaned up in the future some of the cooling aspect of the tropospheric aerosols will be lost. Since aerosols last much longer in the stratosphere than they do in the rainy troposphere, the amount of aerosol-forming substance that would need to be injected into the stratosphere annually is far less than what would be needed to give a similar cooling effect in the troposphere, though so far as the stratospheric aerosol burden goes, it would still be a bit like making the Earth a permanently volcanic planet (think of a Pinatubo or two a year, forever). It might make sense to take a small portion of the aerosol that would have been dumped into the troposphere by retired dirty coal plants, and inject that directly into the stratosphere where it will restore the lost cooling effect while (hopefully) doing less harm than the old stuff dumped into the lower atmosphere. To go farther, though, and count on offsetting the entire unrestrained CO2 production of the coming century with engineered aerosols is fraught with peril.
Scientists just love to think about this kind of stuff, and I’m no different.Harvard is hosting a small workshop on aerosol-based geoengineering, and I have to say I’m looking forward to it. It’s like having a shiny new toy, and the chance that you might actually get to use it to play around with the real Earth and see what happens has a certain fatal attraction to it. Then, too, science thrives on a spirit of free inquiry, and it would be anathema to say that there are some things that just shouldn’t be thought about (though there are certainly some things that, once thought about, shouldn’t be built). But, there’s a real danger of jumping the gun and giving the impression that we already know we have a way out if things get too bad. Ken Caldeira’s Op-Ed is a case in point. “Which is the more environmentally sensitive thing to do: let the Greenland ice sheet collapse, or throw a little sulfate in the stratosphere?” is the way he frames the issue. To be sure, Ken only gets 400 words to make his case (which seems to be that the folks who work on this sort of stuff ought to get some more money), but those 400 words leave little room to explain the vast array of problems that need to be resolved before we can even begin to think of this as an out. Caldeira’s Op-Ed makes it seem like a slam-dunk, needing maybe only a diversion of 1% of climate research funds in order to do the trick.
Here are a few of the problems that need to be worked out: There’s the issue of the effect of the aerosols on stratospheric chemistry (think how unanticipated the chemistry of the Ozone Hole was), and the question of just where the aerosols would go once injected. There’s the question of the effect of the aerosols as cloud-condensation nuclei if they work their way into the tropical upper troposphere — an increase in high cirrus clouds could well lead to warming. Then, there’s the full range of possible effects on the atmospheric circulation. Held and collaborators (PNAS 2006) have implicated the joint effect of aerosols and greenhouse gases in the trend towards Sahel drought, and generally there are issues in what inhomogeneous aerosol forcing might do to things like the North Atlantic Oscillation. Also, a planet with a dim Sun and high CO2 is not the same thermodynamically as a planet with brighter Sun and lower CO2, because the reduced sunlight at the surface is not able to sustain as much evaporation, which has consequences for global rainfall. In a recent essay in Le Monde, Edouard Bard has pointed out additional problems with geoengineering.
In my mind, the most serious peril of sulfate geoengineering is one that stems from a problem that is not at all in dispute: the fact that the lifetime of CO2 in the atmosphere is centuries to millennia, whereas the lifetime of aerosols in the stratosphere is at best a few years. That means committing the future generations to continue the aerosol injection basically every year more or less forever. We’re banking a lot on confidence in future stability and prosperity of the world here. A patrician in the glory days of the Roman Empire might well have expected the Pax Romana to go on forever, but really nobody expects a Dark Age.
One also has to wonder whether the international treaties and organizations needed to agree on and execute a geoengineering scheme are significantly easier to realize than the agreements needed to decarbonize the energy future, which would offer safer and more durable climate protection. And once you open the Pandora’s box of geoengineered climate, what do you do if nations disagree about what kind of climate they want, or if some poor nation objects to suffering drought in order to cancel heat waves in Chicago? Great fodder for science fiction novels about climate wars, but I’d prefer not to have to think about it happening for real.
The problem is that geoengineering a sunshade is being sold as insurance long before anybody has any idea whether it would work and what the unintended consequences would be. It’s not really insurance. It’s more like building a lifeboat, but a lifeboat based on a design that has never been used before which has to work more or less perfectly the first time the panicked passengers are loaded into it. The problem is that by the time we know enough to have any confidence at all in this lifeboat, CO2 may have risen to the point where the lifeboat becomes not just a backup, but a necessity. Would diverting 1% of the world’s climate research funds into this problem clarify the issues in time? I doubt it. Would devoting 10% a year to the problem be worth it? I doubt that, too, in comparison to more pressing research needs.
Now, can we please get back to the serious business of trying to figure out how to economically reduce global CO2 emissions?
I asked KEn Caldeira these question on the 5th of september 2007, may be someone can answer them over here.
“With great interest I have read the articles (or article) about adding SO2 into the atmosphere, in order to cool the Earth.
I agree that the best way to counter global warming in the long term is to immediately cut the emission of greenhouse
gasses, but as you have stated in other articles this is unlikely to happen, even with the most recent proposals.
20 billion ton of CO2 emitted somewhere during this century per year means we will almost triple the current emission rates…
I do not agree with you remark (if you were stated correctly) that adding SO2 into the atmosphere is a last resort and
should only be deployed when we have reached some point of no return. I wonder if SO2 is any good by the way, given the current
acidification of the worlds’ oceans by CO2. I don’t know if the amounts of SO2 needed to cool the Earth will have an significant
effect on the acidity of the oceans. Do you?
A point is: what qualifies as a point of no return? To me personally this point is already reached for instance. If we look at the
current situation at the North Pole and the effects of such a small amount of sea-ice (area) and the feedback mechanism involved
over there, a further melt in itself is dangerous as it will accelerate global warming. Ice-bears that drown really are so awful to see
or hear about. But that is just my point of view.
But I see many advantages in cooling the Earth (after thorough research and experiments on the downsides of each mechanism
deployed!):
– A cooler world is better in absorbing Co2
– Absorbing more CO2 means a slowing of acidification of the seas
– Methane hydrates and other methane sources become increasingly unstable in a warmer world,
which could result in catastrophic warming if a huge amount of destabilized methane hydrates
would be released into the atmosphere (which seems to have happened in the past)
Another thing is that the economy is adapting (or will adapt) to the change. People will start to grow other crops and
become dependent on it (it is already happening now). Other opportunities will arise. If we would suggest to change
it back all of a sudden in 2050 (of instance), this probably would lead to yet another argument of economists and therefore
politicians not to do anything. I am afraid it takes nothing short of a catastrophe before anyone will accept changes that could be detrimental
to the economy
The richest countries are situated in the temperate zone. Many people like a warmer climate over there. In Holland, this
years’ summer has been only somewhat warmer than normal and it has been rainy. Many people think of it is a very bad summer.
If cooling the Earth would lead to summers that where normal from 1951-1980, people would not accept it. Although it is far away,
I think it is reasonable to think that people would not vote for politicians that would suggest cooling back to the
1951-1980 standard. If we look at the current reasons why people vote for someone or don’t, in general, it is their
personal lives. Many people believe money equals happiness and many politicians aim at that thought in order
to get people voting for them. I believe that we are too opportunistic to look beyond what we believe is good for
ourselves and start looking what is good for life on Earth. The best predictor for future behavior is someone’s past
behavior….
I see great difficulty in practice in deploying geo engineering schemes only when things get out of hand, because the
perception of what is “out of hand” is clearly different among scientists as compared to the general public and most politicians….
Another thing is that we do not know what is exactly needed to reverse a system that has spinned out of balance so
much to get it back again. Suppose Greenland starts to melt, or the West Antarctic ice sheet because of a warming of
2 K over 100 years. Is a cooling of 2 K in 10 years enough to stop this process?? Or do we need 3K cooling, or 4 K?
If it is 3 K (for whatever reason), consider this: some or many species will adapt ( I hope so) to the warming we witness
and will witness in the near future. Now if adapting to the current rate of warming is indeed a great task for many
species, how do you suppose nature will react if we would deploy a geo-engineering scheme that would drop the
temperature in Earth by 3K (for instance, what is unacceptable warming? What is needed? When will we need it?)
over a decade or two??
In short I think deploying geo engineering only when some imaginary threshold has been reached near, 2050 (for instance),
could very well have very big practical, political and natural implications. In many recent publications on this subject
(at least the ones I have read), these have not been taking into account. Many rush to state it is a last resort and thus these
things should only be deployed when we have no other option. Many state that the best thing is to cut emissions now.
True, but it won’t happen (fast enough). We do not have the influence we want to, because the general public is oblivious about
science, knows little about research and is not too impressed by scientists in general.
I question whether politicians will see it as an option by then.
Whether the general public will see it as an option and if deployed but then, the implications are not much worse that doing it now.
Simply put: adaptation to small changes in general seem more easy than to big changes. We should research and deploy geo engineering
schemes to cool the Earth as soon as possible.”
That is what I asked him. Sorry for the errors in English.
Researching geo engineering seems very logical to me, just look how much we have done till now and what the results are: kust an ongoing continuing rise and politicians who are as keen as ever on explioting more oil (Putin in the Artic, new oilfields in Brazil etcetcetc).
Best regards,
Jorge Sereno
It seems to me that the argument for doing research into geoengineering approaches to mitigate warming is a compelling one, for the following reasons:
* the scientific evidence suggests that we need to make real cuts in emissions, real soon. Ultimately, we have to get down to near-zero net emissions. Otherwise, we get really, really unacceptable consequences.
* Progress thus far suggests that we will not make such cuts. Maybe this will chance once George W. Bush hauls his sorry backside out of the White House, maybe not. Clinton/Gore couldn’t get substantive action on climate change done either.
* Therefore, we are left with two alternatives – a) take the really, really unacceptable consequences, b) or apply some kind of geoengineering.
I would prefer “neither”, but given the choice I’d sure like option b) to be available.
As a non-expert, ultimately, the only geoengineering approach I really like is sucking CO2 out of the atmosphere and sequestering it, but it’s likely to take decades to deploy on the kind of scale necessary. But an approach that reduces insolation for a few decades might buy us that time.
So, yes, I reckon there should be considerable amounts of money to see whether there are emergency geoengineering approaches available to us that aren’t worse than the disease.
It kind of amazes me how quickly “skeptics” move from saying we don’t understand enough about climate to attribute the current warming trend to CO2–the portion of the climate system we probably understand best–to saying we need to start geo-engineering with aerosols–where we have greatest uncertainty.
They go from “warming is better than cooling” to “let’s start squirting SO2 into the atmosphere to cool the climate” on a dime.
Isn’t it interesting how they go from saying “We don’t trust the models” to advocating actions that we cannot even begin to model with confidence.
It would seem that they can advocate only two courses–dangerous inaction or reckless intervention.
Re #203
I thought one of the reasons for confidence in the models was that they predicted the results of pinatubo so well.
As for uncertainty, I’d say iron fertilization is probably a good deal more unpredictable than an artificial volcanic eruption.
This isn’t geoengineering, but it may be in the right direction:
http://www.duke-energy.com/news/releases/2007112001.asp
“… Integrated gasification combined cycle technology uses a coal gasification system to convert coal into a synthesis gas (syngas). The syngas is processed to remove sulfur, mercury and ash before being sent to a traditional combined cycle power plant ….. regulators also were supportive of Duke Energy studying capture and sequestration of a portion of the plant’s carbon emissions. If the study is successful, carbon dioxide capture and sequestration equipment could be added to the plant….”
And the ash, presumably, can be mined for heavy elements that don’t come out in gas form as sulfur and mercury do. Nice idea, first try I gather, hope it works.
In disclosure, my family bought a little Duke Energy stock decades ago; I’ve hung onto it hoping they get smart about the future.
Re 205 and ocean fertilization with iron:
New research discredits a $100 billion fix to global warming
I recall also seeing work on ocean sediments indicating that during the dusty-dry climates when lots of windblown dust is in the air, plankton did not bloom in the oceans in proportion to the added minerals.
Well, I said it was unpredictable, didn’t I? :)
The scary thing is, if it’s a bloom of poisonous algae, it might well prevent feeding by larger animals, perhaps even zooplankton. Wouldn’t that be a can of worms.
It’s too bad, because I really want this solution to work. Planktos has this amazingly seductive marketing about regrowing the “floating forests” and increasing ocean biomass hugely. If only…
Martin and I have been discussing variously wacky solutions, and I have one that’s almost as visionary as Space Solar Power, and arguably more wacky:
Artificial hurricanes.
By that I mean an artificial mountain, created of air-inflated graphite reinforced polycarbonate (or cheaper equivalent), perhaps 17 kilometers tall and a third or half that in diameter at the base. There is a hollow tube up the center, perhaps 250 meters in diameter at the base, and a kilometer at the top. It’s open at the top, and saturated air at the bottom is pulled upward by the low pressure 2-5 Km up, condensing and following the pseudo-adiabat until it equalizes with the pressure at 17 Km.
At a throat velocity of 50 meters/sec, and a pressure drop of 1/10th atmosphere at the bottom, that’s a potential 25 gigawatts of wind energy, continuous. Capturing most of the precipitated water, it yields ~30 tons/sec of fresh water. Assuming capture at a height over 5 Km, that yields 1.5 gigawatts hydropower, a mere drop in the bucket (but every little bit counts).
By controlling the mixing activity at the top, cirrus formation could probably be almost completely suppressed, helping to mitigate the effects of CO2 forcing.
Of course, you might want to shut it down during the dry part of the Madden-Julian oscillation. Maybe you could build several dozen of them, spaced so you always have the same number running.
This way, you could get carbon-free power, fresh water, and CO2 mitigation all from the same installations. With luck you could also reduce the number and power of destructive storms. By using a large portion of the energy for pumping water to where it’s needed, you can reduce the impact of intermittency (as long as you maintain an appropriate reservoir at the target end). Note this last point also applies to combined solar power/desalination plants in general.
As for the cost of building such huge structures out of plastic and pressurized air, the cost of such things could be expected to drop substantially due to economies of scale, and by being made “smart”, they could be much lighter, using much less material, and still be able to respond to major storms without self-destructing.
RE artificial hurricanes in 210, check out the Atmospheric Vortex Engine.
Clever stuff — I wouldn’t mind having one in my backyard.
Thanks, Jim.
I like it, but if you’re going to get real power out of it, your vortex has to reach the tropopause, which means, in the tropical seas, an artificial hot tower at best. Preventing the updraft at 2-5 Km height from skipping away would be a real challenge, since the entire energy generating process is working at that height. I suspect enclosing it in an artificial mountain would be easier than dynamic control from steering the air movements at the base.
OTOH, have you ever seen a dust devil with a little cumulus on top? They can run from several hundred meters to several km tall, and are powered by the updraft in/under the cumulus. The Atmospheric Vortex Engine might be able to create and maintain a stable version of that.
Of course, I could be wrong about the control issue. If so, it might be possible to create such large power stations at a much lower cost.
Let me try to understand this: We had cooling of the earth from 1945 to about 1975 when we started reducing sulfur emsission for local pollution reasons. Taking apart what nature had put together. Now we have a warming trend very similair to what we had from 1910 to 1945 and most of it is being caused by CO2 because the feed back I get from scientists is that the 1910 to 1945 temperature data can not be trusted and most of the rise was thought to be solar. Some models say if we remove sulfur from the fuels we burn we can expect it’s contribution to warming about equivalant to that for a doubling of CO2. Should we then be looking at how to add back natures cooling compound at high elevations. Burning high sulfur jet fuel when at altitude might be one option. China is presently burning more coal than the US and Europe combined and some of it is said to have up to 5% sulfur. Could they be the reason for the nearly flat global mean surface temperature for the last ten years.
It is really amazing the I found very few comments above about going to nuclear power when it has the best chance to stop CO2 emission from expanding.
The other somewhat neglected subject for reducing CO2 is the planting of trees. One source I found showed that young pine tree’s growth rate increase 248% with CO2 increasing from 300 to 600 ppm. The uptake of CO2 in forest near the equater and above 40 degrees N is increasing based CO2 concentration at strategic locations. China is planting 200,000,000 trees and South Africa has an active pine forest industry on old grass land. Yes fires happen, but the burned pine trunks are being farmed and used to make caskets for those dying of AIDS. With northern forest having 25 to 50 year cycles and most wood going into structures this should give time for solar power to take hold.
Conclusion-the world will warm from the removal of sulfur and we should at least develop a reasonable system to use it while nuclear and solar power get perfected.