This week, in its long awaited 2013 report, the U.N. Intergovernmental Panel on Climate Change made the bold proposal that no more than a trillion tons of carbon should be burned and released into the atmosphere by humanity—with about a half trillion tons already having done so, and the remaining half trillion expected, at current rates, to be burned by 2040. Unfortunately, this bold proposal, already vilified by climate-change deniers, is not bold enough.
The current problem is two-fold: First, the carbon we burn now will stay in the atmosphere for hundreds of years. Stopping the burning of all fossil fuels today would not remove the cumulative carbon burden that has already raised CO2 abundance in the atmosphere to a level not seen on earth in the past five hundred thousand years, a span over which we have direct data. Second, because we continue to burn carbon, every year that we delay significant reductions would require even more extreme reductions in the following year.
For example, current estimates suggest that to have a sixty-seven per cent chance of attaining the I.P.C.C.’s goal of keeping global warming to less than 3.6 degrees, it would have required 3.7 per cent reductions per year, had reductions begun in 2011. If they begin in 2015, reductions would have to be 5.3 per cent per year. If we wait until 2020, reductions would have to occur at the currently unimaginable rate of nine per cent per year.
Such reductions are not going to happen anytime soon. New inventories of natural gas, combined with new drilling techniques and direct and indirect subsidies for oil and gas exploration, meant that global emissions of carbon dioxide reached record highs in 2011 and 2012.
In the face of these obstacles, we have two choices: Give up and resign ourselves to living on Earth 2.0, with the possibility of vast and disastrous social and political upheavals due to changing temperatures, rising sea levels, and the like; or try and do something about the carbon that is already in the atmosphere. We made the mess, and it is our responsibility to clean it up for future generations.
Efforts to achieve this goal have focussed mostly, thus far, on capturing CO2 and sequestering it at the source of its production. A group of the world’s leading geoscientists, physicists, and climate scientists which convened at my institution earlier this year, and a similar group assembled independently at Oxford University this week, both came to the same conclusion: a more effective global strategy would be to remove carbon dioxide directly from the atmosphere. Remarkably, this sensible and direct approach has received almost no R. & D. support to date, compared to the tens of billions of dollars devoted to increasing fossil-fuel production. (For more, see Michael Specter’s piece in the magazine, from 2012, on geoengineering and climate change.)
Direct-air capture—deliberate extraction of CO2 from our atmosphere using empirically proven technologies—may turn out to be more expensive than carbon capture at the emission source, but it has several important possible advantages. It doesn’t have to be close to a hundred per cent efficient; it can be usefully done by a single country, or a “coalition of the willing”; and units could be deployed away from population centers in dry wastelands located above geologic strata suitable for storage of the captured CO2. Finally, because air capture is independent of the source of the CO2, direct-air capture would not have an impact upon “economic competitiveness,” a buzz term for many who now claim that the potential economic costs of energy transitions argue against changing the status quo.
Other supposed geoengineering solutions, including injecting other materials into our atmosphere, have been proposed to moderate the effects of anthropogenic climate change. They, however, treat symptoms, not the disease, and come with huge uncertainties associated with their possible impacts.
Whatever approach we may take to try to achieve a sustainable CO2 level in the atmosphere will require bold and dramatic initiativ