Learning to Live With Climate Change Will Not Be Enough

The awareness that humans could alter the climate of Earth has dawned slowly on our consciousness. In 1896, Swedish chemist Svante Arrhenius deflected his anguish over a failed marriage into remarkably tedious and, as it turned out, accurate calculations about the effect of CO2 emissions on climate. It was an oddly therapeutic thing to do, but it had no more effect on public attention than the smallest cloud on a distant horizon.

Another 69 years would pass before scientists warned a U.S. president of the potential for serious climate disruption, and still another 30 years before the first report from the Intergovernmental Panel on Climate Change.

Now, facing climate destabilization, our choices for action are said to be adapting to a warmer world or mitigating the severity of climate change by sharply reducing greenhouse gas emissions. Of course, neither adaptation nor mitigation alone will be sufficient, and sometimes they may overlap. But in a world of limited resources, money, and time we will be forced often to choose between the two. In making such choices, the major issues in dispute have to do with estimates of the pace, scale, and duration of climatic disruption. And here the scientific evidence tilts the balance strongly toward mitigation.

The argument for adaptation to the effects of climate change rests on a chain of logic that goes something like this: Climate change is real, but will be slow and moderate enough to permit orderly adaptation to changes that we can foresee and comprehend. Those changes will, in a few decades, plateau around a new, manageable stable state, leaving the gains of the modern world mostly intact -- albeit powered by wind, solar, and as-yet-undreamed advanced technologies.

In other words, the developed world can adapt to climatic changes without sacrificing much. The targets for adaptation include developing heat- and drought-tolerant crops for agriculture, changing architectural standards to withstand greater heat and larger storms, and modifying infrastructure to accommodate larger storm events and rising sea levels, as well as prolonged heat and drought. These are eminently sensible and obvious measures that we must take.

But at some point there are limits to what can be done and the places in which such measures can be effective. With predicted changes in temperature, rainfall, and sea level rise, it is unlikely that we can "promote ecosystem resiliency" or adapt to such changes with "no regrets," as some have suggested. On the contrary, ecological resilience and biological diversity will almost surely decline as climatic changes now underway accelerate, and going forward we will surely have a great many regrets -- chiefly of the "why did we not do more to stop it earlier" sort.

Accordingly, more extreme adaptive measures called "geoengineering" are being discussed. These include proposals to fertilize oceans with iron to increase carbon uptake, or injecting sulfur dioxide into the upper atmosphere to increase the reflective albedo and thereby provide temporary cooling. But since the effects of geoengineering are largely unstudied and its risks largely unknown, it is a "true option of last resort" in the words of one analysis. Accordingly, "the best and safest strategy for reversing climate change is to halt the buildup of greenhouse gases," as a recent article in Foreign Affairs suggests.

Proponents of mitigation, on the other hand, give priority to limiting the emission of heat trapping-gases as quickly as possible to reduce the eventual severity of climatic disruption. The essence of the case for mitigation is that:

• Growing scientific evidence indicates that the effects of climate change will be greater and will occur faster than previously thought.
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