Draft versions of a forthcoming working group report from the United Nations Intergovernmental Panel on Climate Change — set to be formally released Sept. 27 — have already found their way into the hands of certain news media,  and the outlook isn’t pretty.

The panel of more than 800 experts now projects that sea levels could rise by between one foot and three feet by the end of the 21st century if greenhouse gas emissions continue at their current pace. That compares to the panel’s earlier projection in 2007 of 7 inches to two feet in sea level rise this century.

The report’s authors also reported even greater confidence (95 to 100 percent confident) that human activity is the dominant contributor to global warming. That’s up from 90 percent in the panel’s 2007 report, 66 percent in 2001 and just 50 percent in 1995.

There are, of course, legitimate questions about the degree to which that confidence is justified. While sea temperatures and concentrations of atmospheric carbon have actually exceeded scientists’ models, surface temperatures have not, and the rate of warming has slowed noticeably since 1998.

The IPCC panelists reported “medium confidence” that the slowing pace of warming was a temporary phenomenon due to a combination of natural weather variations and such factors as an increase in volcanic ash, an ebbing low point in the 11-year solar cycle, greater than anticipated absorption of heat by the deep oceans (not necessarily the bright spot it might appear, given the impact this could have on ocean ecosystems) and, finally, the potential that climate may be less sensitive to build-ups of atmospheric carbon than the models would suggest.

Even without those caveats, we wouldn’t expect the news to necessarily persuade many climate skeptics of the urgency of action, any more than earlier studies have. A survey published earlier this year in Environmental Research Letters found that more than 97 percent of 12,000 climate studies published over the past two decades finger human activity as a significant cause of global warming.

And yet, despite that overwhelming scientific consensus, according to an April poll by the Pew Research Center, just 42 percent of the American public believes human activity causes global warming, with 27 percent saying there is no evidence of global warming at all. Among Republicans, just 19 percent say human activity is causing global warming, and among conservative Republicans, just 16 percent agree.

But as strange as it might sound, when it comes to public policy around disaster preparedness and, specifically, flood risks, there is a very real sense in which the debate over climate change and rising seas isn’t actually the most important question.

That insight is highlighted in a separate report appearing last month in the journal Nature. Researchers looked at the flood risks faced currently by the 136 largest coastal cities worldwide — including Miami, New York, New Orleans, Tampa-St. Petersburg and Boston – and how they are estimated to change in coming decades. The first three of those cities currently combine for roughly a third of flood losses around the globe, while China’s Guangzhou contributes another 12 percent.

The report includes the expected apocalyptic headline number that is apt to open some eyes while causing others to roll, namely that global flood losses could eventually top $1 trillion a year if there were no changes in flood management or adaptation. Read a little further, and one finds the more sober analysis that, even with significant investment in flood defenses, annual global flood losses still would be expected to rise to between $60 and $63 billion by 2050, compared to the current $6 billion.

But what’s truly striking about the paper is that the researchers project average global flood losses will rise to at least $52 billion a year by 2050 “with projected socio-economic change alone.” That is to say, flood risks will spike almost tenfold based solely on economic development and growth in coastal populations, ignoring the expected effects of climate change.

This insight – that in the near-to-medium term, the effects of growing populations in risk-prone areas will likely outpace even the effects of climate change in terms of putting more people at risk – should be an obvious one to guide public policy in the decades to come. Its implications should be similarly uncontroversial. Both those on the left and right should agree on that we must withdraw all government subsidies for coastal development. Don’t create any new beach house bailout programs; move risks currently borne by government insurance plans – whether it’s the National Flood Insurance Program or state residual markets and wind pools – into the private sector; and allow private sector insurers to charge risk-based rates. Finally, we should invest in mitigation, encourage strong building codes and, where needed, offer lower-income residents assistance to raise or harden their homes, or relocate to higher ground.

Thankfully, some politicians appear to get it. Just this week, New Jersey Gov. Chris Christie vetoed legislation that would have allowed for residential and commercial development in “coastal high-hazard areas” on piers along the Hudson River. This week also saw the long-awaited release of the White House Hurricane Sandy Rebuilding Task Force‘s report, which includes 69 recommendations to “help homeowners stay in and repair their homes, strengthen small businesses and revitalize local economies and ensure entire communities are better able to withstand and recover from future storms.” Some key recommendations include:

Some of these steps we would probably give higher priority than others, and the value of some are highly contingent on the details of implementation. But they represent a decent starting point for how to think about rebuilding in catastrophe-prone areas and could be applied in other regions as well.

Combine a “do no harm” approach of removing subsidies to coastal development with smarter, safer planning, and the result should be communities that are much better prepared to withstand whatever impacts climate change does — or doesn’t — throw at them.

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