After Hurricane Katrina leveled much of New Orleans, many authorities spoke about the folly of building at or below sea level.

“They talk about New Orleans, but the sad truth is that nearly all our infrastructure is below sea level,” Gov. Andrew M. Cuomo said this week. Thinking out loud, he suggested the construction of huge sea gates. Mayor Michael R. Bloomberg said Thursday he didn’t think they were realistic.

That they disagreed, and did so in public, is one of the healthiest developments in civic life this year.

The consensus of scientists globally is that climate change has taken place and has contributed to the rise of sea levels by close to a foot over the last century. Some forecasts suggest that in the years ahead, the increase will be more than 10 times greater. Yet climate change has been close to unmentionable during the presidential campaign. The agenda has been set by minority voices, some of them quietly financed by industries that might be threatened by measures to curb greenhouse gases.

Somehow, by denying the existence of climate change, they managed to shut down debate over what to do about it. That is why a disagreement between the governor and the mayor about sea gates is so refreshing. The climate change issue led Mr. Bloomberg to endorse President Obama on Thursday.

Wherever the debate goes nationally, New York will have to look hard at where and how it stands in the natural world. “We haven’t thought about redesigning for radically higher sea levels,” said Adrian Benepe, who recently left city government after three decades of service, most recently as commissioner of parks and recreation. Mr. Benepe, now an executive with the Trust for Public Land, said he had been intrigued by proposals included in “Rising Currents,” a 2010 exhibition at the Museum of Modern Art. “It may be that for the city to exist for the next century,” he said, “we’re going to have think in ways that we haven’t before.”