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Study: Geo-engineering to Mitigate Global Warming Could Backfire

Simulated surface air temperature (a) and annual rate of temperature change (b) for business-as-usual (red), geo-engineering beginning in 2000 (blue), failure of geo-engineering in 2025 (green), failure in 2050 (orange), and failure in 2075 (purple). Runs with doubled climate sensitivity are plotted as dashed lines. Click to enlarge.

Geo-engineering attempts to mitigate global warming by blocking sunlight could succeed and drastically cool the planet, bringing global temperatures back to around year 1900 levels—but could just as easily worsen the situation if these projects fail or are suddenly halted, according to a new computer modeling study.

The study, described in an open access paper in the 4 June early online edition of The Proceedings of the National Academy of Sciences, modeled possible outcomes if society tries to slow global warming by geo-engineering a solar filter while greenhouse gas emissions continue on a business-as-usual basis rather than reducing carbon dioxide emissions.

Given current political and economic trends, it is easy to become pessimistic about the prospect that needed cuts in carbon dioxide emissions will come soon enough or be deep enough to avoid irreversibly damaging our climate. If we want to consider more dramatic options, such as deliberately altering the Earth’s climate, it’s important to understand how these strategies might play out.

—co-author Ken Caldeira, Carnegie Institution’s Department of Global Ecology

Although the term “geo-engineering” describes any measure intended to modify the Earth at the planetary scale, the current study focuses on changes that reduce the amount of solar radiation that reaches the planet’s surface. Several methods to accomplish this have been suggested, from filling the upper atmosphere with light-reflecting sulfate particles to installing mirrors in orbit around the planet.

According to the model, the global climate system responds quickly to artificially reduced insolation; hence, the researchers conclude, there may be little cost to delaying the deployment of geo-engineering strategies until such a time as “dangerous” climate change is imminent.

However, the study also finds that if any hypothetical geo-engineering program were to fail or be cancelled for any reason, a catastrophic, decade-long spike in global temperatures could result, along with rates of warming 20 times greater than we are experiencing today.

If we become addicted to a planetary sunshade, we could experience a painful withdrawal if our fix was suddenly cut off. This needs to be taken into consideration if we ever think seriously about implementing a geo-engineering strategy.

—Ken Caldeira

The authors concluded that lower temperatures in a geo-engineered world would result in more efficient storage of carbon in plants and soils. However, if the geo-engineering system failed and temperatures suddenly increased, much of that stored carbon would be released back into the atmosphere. This, in turn, could lead to accelerated greenhouse warming.

Reduced solar radiation not only affects temperatures in the simulations, but also global rainfall patterns. In a model run with no simulated geo-engineering, warmer temperatures resulted in more rainfall over the oceans, while increased carbon dioxide levels caused a decrease in evaporation from plants’ leaves, and consequently a decrease in rainfall over tropical forests. In contrast, the geo-engineering scenario—which had lower temperatures but the same high levels of carbon dioxide—resulted only in a decrease in tropical forest rainfall.

Many people argue that we need to prevent climate change. Others argue that we need to keep emitting greenhouse gases. Geoengineering schemes have been proposed as a cheap fix that could let us have our cake and eat it, too. But geo-engineering schemes are not well understood. Our study shows that planet-sized geo-engineering means planet-sized risks.

—Ken Caldeira




Even without geo-engineering the blame game is starting to intensify eg inhabitants of some disappearing Pacific Islands saying developed countries owe them the right to immigrate. That could be far worse such as suing to recover losses from crop failures due to freaky weather. Governments around the world would have to pass legislation preventing lawsuits before geo-engineering could even be considered .


Isn't this like sweeping the dirt under the rug? It doesn't really solve the problem at all. Sure it feels good for a little while but ... as in taking over the counter drugs which mask symptoms .. can be quite deadly if it leads to ignoring the source of the problem in the first place.


Beside orbital mirrors and aerosols what about iron fertilization of the oceans?


According to scientists from the Abrupt Climate Change Strategy group, there is one kind geo-engineering that is low-risk and far more feasible: bio-energy with carbon storage (BECS). This is a carbon-negative energy system that can be implemented on a planetary scale.

More here: referring to the same study as in this article, but also to the BECS option.
and here: Abrupt Climate Change and geo-engineering the planet with carbon-negative bioenergy.


I sure would hate to see us try any of these geo-engineering "fixes" that can't easily be removed if it turns out they have unintended consequences. e.g. seeding the upper atmosphere with sulphates. If you put the stuff up and it goes wonky (unintended climate,biological or chemical effects), how do you get it back?


You solve the problem by stopping the cause of the problem. You reduce CO2 emissions by cleaning up power plants and cars.You don't create more problems in an attempt to solve this one. This is where technology can not solve all problems but can create others if it is not used wisely.


Even if this tech did work it would require a long-term commitment to funding. When have we ever seen that happen?


Does anyone really believe our governments are going to pay for a system
to shield the really poor people of the world , ie sub saharan africa , after
the dismal faliure of the recent G8 summit !
This is just total bull**** a distraction away from the real issues that they
have niether the strength or the intelligence to face


More shmoke and mirrors - why not turn down the solar thermostat while at it?


Biochar/terra preta/agrichar


I wasn't aware of this research, but I've been saying the same thing:  geoengineering is only a palliative, and we have to address the greenhouse gas problem directly.


I first got a load of this idea from the August 2005 issue of Popular Science. It was the new White House plan for climate change.

Their plan?
Don't build large wind turbines to generate CO2 free power, build HUGE wind scrubbers to filter out the CO2 after the fact.
Don't put a solar power satellite in orbit to beam clean energy back to earth, put an even bigger mirror there to block the sunlight.
Don't put clean energy producing OTEC plants out in the oceans, put cloud boosting plants out there instead.

Can you say "idiots?"

G. R. L. Cowan, boron combustion fan

Silicates-to-carbonates is geoengineering that is obviously entirely prudent.

If the others are like coming to a house to house-sit, turning on what you think is a light-switch and hearing a loud grinding noise suggestive of progressive structural damage, and flipping a number of other switches in hopes of cancelling it, silicates-to-carbonates is like flipping it back.

Does anyone think that talk about geoengineering that seems not to be cognizant of the above is not a stupid waste of time?


All I can say is wow...

I can't believe that anyone could seriously consider such a program. I'm in the aerospace industry, and anything that is space based usually interests me, but do the advocates of this plan have ANY idea how expensive it is to launch payload into space. On the order of 10K per KILOGRAM of material. and how many hundreds of tonnes of payload will need to be launched to even marginally decrease solar radiation on the surface will be needed. Honestly, I'm always keen on finding high tech solutions to these problems, I'd much rather push technology further, rather then step back into the past, but this is pure nonsense.



The point is that this is a classic case of stepping over a dollar to pick up a dime.
And it is not meant to be a solution, it is designed to maintain the status quo.


--Posted by: Tom | Jun 11, 2007 5:26:01 AM
what about iron fertilization of the oceans?--

Thats even more dangerous

There's 7 billion tons a year (BTY) of carbon going up every year.

800 in the air right now.

And there's 40,000 in the ocean.

Screw up the ocean, and we're either going to freeze or burn.

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