Terraforming Earth

Aerosol particles can have multiple effects on clouds, which affect the climate indirectly

NASA's Johnson Space Center.

The term geoengineering is relatively new. It follows and alters the word terraforming, coined by a science fiction writer 70 years ago to denote the act of making another planet more Earth-like. When I was writing my own Mars trilogy of novels in the 1990s, I described the deliberate alteration of that planet to give it an Earth-like biosphere; as I did so, it occurred to me that we were already doing to Earth what my characters were doing to Mars.

But to say that we were ?terraforming Earth? was painfully ironic, suggesting as it did that we had damaged our home planet so badly we now needed to take drastic steps to restore it to itself. When geoengineering entered the lexicon, many bristled at the word?s hubristic implication that we had the knowledge and power to engineer anything so large and complex as our planet. Still, the term has stuck, and it has essentially come to mean doing anything technological, on a global scale, to reduce or reverse the effects of climate change.

Defined this way, the idea makes almost everyone uneasy?including the scientists who introduced it, most of whom agree that the best solution to our climate problem remains rapid decarbonization. But these scientists have also noticed that our progress on this front hasn?t been good. We lack the political mechanisms, or maybe even the political will, to decarbonize. So people are right to be worried, and some of them have therefore put forth various geoengineering plans as possible emergency measures: problematic, but better than nothing.

Objections to geoengineering appeared immediately. Many people have expressed doubt that the proposals would work, or believe that a string of negative unintended consequences could follow. Merely discussing these ideas, it has been said, risks giving us the false hope of a ?silver bullet? solution to climate change in the near future?thus reducing the pressure to stem carbon emissions here and now.

These are valid concerns, but the fact remains: Our current technologies are already geoengineering the planet?albeit accidentally and negatively. Consider that significant percentages of the world?s wetlands have been drained, and large swaths of its forests cut down. Ecosystems have been devastated by overdevelopment. We?ve raised atmospheric CO₂ levels by about 100 parts per million, and average global temperatures have gone up accordingly. Our oceans have soaked up so much of the carbon we?ve dumped into the atmosphere that the seas have measurably acidified. On land, hundreds of species have gone extinct. And far worse damage is sure to follow if this inadvertent geoengineering campaign of ours is allowed to continue.

For the rest of history, we will be required to work at repairing the damage we?ve already done to the biosphere. Geoengineering, then, has become our ongoing responsibility to life on this planet, including all human generations to come. All of which leads to the question: Can we actually design and accomplish any geoengineering projects that would mitigate or reverse climate change? Putting aside issues of political capability, are any of these projects physically possible?

The answer appears to be: yes, some of them are. Maybe.

Some of the most talked-about proposals entail removing CO₂ from the atmosphere or not letting it enter in the first place. One of them calls for trapping it and storing it deep underground. The concept behind carbon capture and sequestration has already been demonstrated to work; many scientists think it merits further study. And to those who say our most urgent goal is holding atmospheric carbon levels as close as possible to 350 parts per million, it?s attractive for obvious reasons.

Another oft-discussed idea involves shooting sulfur dioxide particles into the upper atmosphere in order to reflect incoming sunlight back into space. While this, too, would appear plausible from a mechanical standpoint, the veneer of plausibility only adds to serious concerns about unknown secondary effects, as well as worries that by taking an action such as this one, the root issue?our need to curb carbon emissions?would remain unaddressed. As a result, this is one of the most controversial geoengineering plans to date. It practically glows with the hubris of weird science; it scares people.

Source: http://feeds.slate.com/click.phdo?i=181a4b7cf0aaa53eadb1bc557f96d563

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