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The National Academies Take On Global Warming

Do we really need more sweeping scientific reports about global warming? At this point we've been deluged with studies and assessments and summaries and reviews, and anyone who's still deep in denial about the problem probably isn't going to be convinced by yet another fat volume of graphs and citations. Nevertheless, the National Research Council—a wing of the country's main scientific advisory body—has just released, at Congress's request, three big new reports on climate change, and there are quite a few interesting tidbits scattered throughout worth highlighting.

The first report, "Advancing the Science of Climate Change," recaps the known facts about man-made global warming—the Earth's getting hotter, human activity is the primary cause, and we can be awfully confident that higher temperatures are going to wreak havoc on water supplies, sea levels, coral reefs, and so forth. But the report also stresses that there are still plenty of processes that are tough to model, like fine-grained regional effects or how ice sheets will behave. (Though, as James Hansen has pointed out, the fact that scientists aren't fully sure about how ice sheets will react to hotter temperatures isn't heartening in the slightest.) It's also very difficult to forecast how humans will react to big environmental disruptions—a theme I explored in this piece on the national security aspects of global warming.

Usefully, the report recommends setting up a single new federal entity that can coordinate climate research across a wide variety of different disciplines. That makes sense. There's still plenty of "hard" climatology research still to do in studying ice cores and pinning down the planet's sensitivity to greenhouse gases and improving models and whatnot. But there's also an enormous range of other topics that need to be folded, from epidemiological research on how diseases might spread to, say, studies on how different farming methods can sequester soil carbon. The NRC report is pretty clear that there are still plenty of gaps in our knowledge about the climate system, but rather than use that as an excuse to stop obsessing—as many skeptics would urge—it sensibly suggests that maybe we should try to fill in those gaps.

The second report, "Limiting the Magnitude of Future Climate Change," lays out a path for cutting U.S. greenhouse-gas emissions without sending ourselves into the poorhouse. Most of the strategies discussed here should be familiar, even mundane, by now: slap a price on carbon, root out energy waste, boost R&D for fancy new clean-tech gizmos. It might have been helpful, though, if the report had recommended a precise target for reducing emissions. Instead, all it does is suggest that the rough goals outlined by the White House and Congress—17 percent below 2005 levels by 2020, 80 percent cut by 2050—are "reasonable."

One critical point from the report: "The longer the nation waits to begin reducing emissions, the harder and more expensive it will likely be to reach any given emissions target." That should be obvious, but it often gets lost. The longer we wait, the more greenhouse gases accumulate in the air, and the deeper (and costlier) our eventual cuts have to be if we want to limit warming below the 2°C mark. It's sort of like filling a bathtub. If the tub's still fairly shallow, you can turn off the faucet slowly and gradually. But if the tub's on the verge of overflowing, you have to shut the spigot very quickly. (Our tub's pretty full, for the record.) Dave Roberts smartly pointed out the other day that this is why it makes more sense to pass an imperfect climate bill now rather than piddle around for years in the hopes that a better legislative option will present itself.

The third NRC report, meanwhile, is all about adaptation. After all, even if the world gets its act together and limits future warming to no more than 2°C, that's still a whole lot of extra heat, and we're still likely to see a number of severe effects (coral bleaching is an obvious one). In fact, we could zero out all the carbon emissions in the world tomorrow and would still have to find ways to make agriculture more resilient or brace our coastal areas for some modest amount of sea-level rise. The debate about responses to global warming can sometimes get framed as adaption vs. mitigation, but in fact, we'll need both.