[OPINION] The geoengineering temptation

Unlike the questions surrounding climate change and its consequences, all of which can be answered by scientists, what we want to do about it depends on values -- that is, what is important to us. The choices, singly or in combination, are: 1) nothing (the current response); 2) mitigation (reducing emissions of greenhouse gases); 3) attempted adaptation to the ongoing climate changes; and 4) geoengineering.

If you are a big oil or coal company, your choice will be nothing. You would choose to continue to make as much money as possible, while the consumers of your products use the atmosphere as a sewer, with no sewerage charge. And you would spend money on public relations firms and charlatans to try to confuse the public about the science so that you could continue this as long as possible, just like tobacco companies did recently about the safety of smoking. (Indeed, you would use some of the same firms and charlatans.)

But if you are like me and want to minimize the damage to people and all other living things on Earth, then you choose mitigation and, where necessary, adaptation. As for geoengineering, we do not yet have enough information to decide, but preliminary studies show that it presents more problems than it solves.

There are basically two quite different and separate types of actions that have been labeled geoengineering. One, carbon dioxide reduction (CDR), involves removing from the atmosphere the main gas that is causing global warming. In general, this is a good idea, but so far it seems rather expensive and nobody has yet designed a system to then sequester the carbon and keep it out of the atmosphere.

CDR proposals include artificial trees that use chemicals to capture the CO2, and then pump it underground or under the ocean; planting fast-growing trees and then burying them; and fertilizing the ocean with iron to make plankton grow faster, hoping they will fall to the ocean bottom. This last idea has not been shown to work and may severely damage the entire ocean ecosystem, but the first two are being worked on.

The other geoengineering idea, solar radiation management (SRM), envisions cooling Earth by putting mirrors in space, pumping salt spray from ships into clouds to make them brighter, or filling the stratosphere with a sulfuric acid cloud, just as volcanic eruptions occasionally do. But volcanic eruptions teach us that, while a cloud in the stratosphere would indeed cool the planet and stop ice from melting and the sea from rising, it would also destroy ozone and produce regional droughts.

There are other potential problems with SRM in the stratosphere. For example, it would do nothing to stop ocean acidification. More importantly, there is no way for us to decide what temperature Earth should be. Whose hand would be on the thermostat?

What if Russia and Canada wanted Earth to be warmer and sinking islands in the Indian Ocean and Pacific want it to be cooler? What if the technology was used for military purposes or a big multinational corporation had a large role? Would you be happy with no more blue skies (but nice yellow and red sunsets), or never being able to see the Milky Way? If we somehow lost the will or means to continue to produce the stratospheric cloud, temperatures would skyrocket, much faster than they are increasing now.

All this underscores the need for further study. We have to be able to quantify the benefits, risks and costs of geoengineering and compare them to the benefits, risks and costs of our other options so that we can make an informed decision. SRM might be needed in a planetary emergency -- say, if continued warming rapidly accelerates ice-sheet melting and sea-level rise, or if it accelerates methane and CO2 emissions from thawing tundra, which would then accelerate the warming itself.

But geoengineering is not a magic solution to global warming. Right now, it looks even more dangerous. So we must redouble our efforts to shift our economies to a post-carbon world, while still allowing the billions of people without adequate food, water and education to improve their lives.

This offers tremendous economic opportunities, if we can just put a price on the dangers to the planet of current carbon emissions. So long as governments begin to push the world in this direction, we have a good chance to save our planet without geoengineering.