My posting on Sunday's Discovery Channel global warming documentary elicited some sharp comments on the efficacy of our available responses. I think this issue merits a posting of its own, building on yesterday's. At issue is whether any program of conservation and transformation aimed at reducing our emissions can succeed at averting further warming, or if these measures are so futile that we should abandon them and either live with the consequences, or focus on counteracting them on the macro level via planetary reengineering. In my view, the answer lies somewhere in the middle.
We should start with what we think we know, as distinct from assumptions and suppositions about political and economic hurdles. My understanding from extensive reading and discussions on the subject is that:
- Further warming appears to be "baked in", even if we stopped emitting CO2 altogether, because of the delayed consequences of the greenhouse gases we've emitted to date, and the persistence of those gases in the environment. However, this warming would likely not be permanent: temperatures would rise, plateau, and then later fall back to "normal", as excess CO2 is absorbed into seawater and carbonates. Total timeframe, a couple of centuries. That's long for us, but short for nature.
- Continued growth in global emissions on the current trend line would more than double pre-industrial CO2 levels and likely increase temperatures by much more, up to 10 deg. F on average by 2100, vs. the 1 or 2 degree rise that is essentially predetermined.
That much is consistent with the data and models, though one of the key analyses of the historical, or "paleoclimate," the so-called "hockey stick" graph of Mann, et al, has been challenged again, this time by a panel of statisticians commissioned by the US Congress. Their findings, which are not widely accepted in the climate science community, don't undermine the conclusion that the earth is warming significantly, but they could change our understanding of the context of that warming, particularly if claims that the decade of the 1990s was the warmest in 1000 years turn out to be unsupportable. Even if current global temperatures are no greater than those in the Middle Ages, with part of the last century's warming merely a natural recovery from the Little Ice Age of the 17th-19th centuries, the extent and present rate of increase could still overshoot those earlier highs and take us into some very uncomfortable territory.
The combination of these facts (or at least current conclusions from available data) leads me to think we need a multi-fold strategy:
- Continue to expand our knowledge of climate processes and refine climate models.
- Reduce emissions below the status quo trend-line, in order to moderate the increases and buy time for the development and deployment of truly low-emission energy technologies.
- Investigate and plan adaptation measures to mitigate the impact of unavoidable warming, particularly in low-lying coastal areas and islands.
- Investigate the means of eventually intervening to restore the climate to pre-warming levels, and in particular to short-circuit the feedback mechanisms that some scientists speculate could create a "runaway greenhouse."
The first two measures are underway, guided by the UN Framework Convention on Climate Change and other international and national bodies. The third point remains controversial in some quarters but will probably prove necessary, if we are to avert humanitarian crises that could overwhelm our ability to respond. The fourth strategy is still viewed as fringe, or even irresponsible, but I wonder how many of us would hesitate to attempt this, if the alternative were the breakdown of global civilization or worse.
Ultimately, no one can predict whether we will be able to overcome the political, economic and social obstacles to mounting a meaningful response to global warming, or whether, if we do, it will be sufficient to prevent really bad outcomes. I still think the best way to look at all of this is as a global insurance policy, the premium for which shouldn't exceed the expected value of the cost.