The Path to Zero

An article in today’s Washington Post reported on new scientific research suggesting that emissions of greenhouse gases must be reduced to zero by mid-century, in order to prevent global warming that could persist for hundreds of years, perhaps eventually producing average temperatures higher than for millions of years. As the climate debate focuses increasingly on policy, the impact of such findings on efforts to craft practical frameworks for reducing US and global emissions becomes as important as the scientific result itself. The implication of the need for truly radical change contained in this latest report might either galvanize action on capping our emissions, or convince us that none of the current pathways for reducing emissions is truly worth pursuing.

The goalpost for stabilizing the climate has been moving for some time. A few years ago, moderating emissions to stabilize the atmospheric CO2 concentration at about twice its pre-industrial 280 parts per million (ppm) was widely regarded as adequate to the task. Further modeling suggested that 550 ppm wouldn’t do the trick, but that 450 ppm might. Then we heard from NASA’s James Hansen that we need to shoot for 350 ppm, a level we unfortunately exceeded in the late 1980s. Now Matthews and Caldeira’s paper in Geophysical Research Letters indicates that if we wish to avoid continued, dramatic climate change over the very long haul, our real goal must be zero net emissions, with as rapid a return as possible to pre-industrial levels. It’s enough to make you throw up your hands in futility.

I don’t think you need to be an economist or a climate skeptic to appreciate just how sweeping the changes in our entire global economy would have to be, in order to achieve zero emissions worldwide by mid-century. Of the current US cap-and-trade proposals, neither the bill now before the Congress nor the proposals of any presidential candidate would get us close to that. Even if the EU and US cut emissions by 80%, the toughest target now on the table, global emissions will continue to grow for at least several more decades and would probably still be above 50% of current levels in 2050.

What does zero emissions mean in practical terms? Well, among other things it doesn’t mean “zero emission vehicles” that merely shift the point of emissions from the tailpipe to the smokestack. And while it’s possible to imagine getting a large part of the way toward a 70% or 80% emissions reduction through greatly-improved efficiency and conservation, we simply can’t conserve our way to zero. Instead, it implies the elimination of essentially all combustion of fuels, other than in facilities that capture and sequester all the CO2 they produce, or of biofuels that absorb in cultivation as much CO2 as they emit when processed and burned. Otherwise, we’re talking about an entirely electrical world, with power generated exclusively by wind, solar, geothermal, hydro, and nuclear sources. Those sources currently meet only 14% of the world's energy needs. For those of us grounded in the realities of fleet, capital stock and infrastructure turnover, the cost associated with changes on such a scale makes adaptation to a warmer world seem like the more attractive option.

As overwhelming as all this seems, however, I see two positive nuggets embedded in this report. One is the timescale for reductions and the other is the notion of zero net emissions. Fifty years is a long enough interval in which to develop entirely new technologies from fundamental scientific discoveries, fine tune them, and roll them out on a massive scale. If we can at least stop making the problem bigger in the meantime, the actual means of reducing our emissions to zero might emerge from an unexpected quarter within the next decade, or from a novel application of some existing technology. And with enough cheap, clean energy at our disposal—perhaps from space solar power—we could even reduce our net emissions below zero, by extracting CO2 from the air and storing it in geological formations or as carbonate rock.

At this point, I believe we ought to be cautious about this new finding. Even ignoring the possibility that the authors’ modeling results won’t hold up, pushing a complete zero-emission agenda now, before we’ve even begun reducing global emissions, seems premature. Combine the implications of zero emissions with the new debate about “global cooling”, and we could have the recipe for another decade of policy gridlock. In the meantime, however, we should be pondering what this research suggests about the proper balance between incremental change and transformation, where the latter is a realistic option. That might seem like a highly esoteric topic in the current economic climate, but in the years ahead climate policy and the economy will likely be increasingly inter-connected.