After looking at one too many projections of global-warming disasters — computer graphics of coasts swamped by rising seas, mounting death tolls from heat waves — I was ready for a reality check. Instead of imagining a warmer planet, I traveled to a place that has already felt the heat, accompanied by Bjorn Lomborg, the Danish political scientist and scourge of environmentalist orthodoxy.
It was not an arduous expedition. We went to an old wooden building near the Brooklyn Bridge that is home to the Bridge Cafe, which bills itself as "New York's Oldest Drinking Establishment." There's been drinking in the building since the late 18th century, when it was erected on Water Street along the shore of Lower Manhattan.
Since record-keeping began in the 19th century, the sea level in New York has been rising about a foot per century, which happens to be about the same increase estimated to occur over the next century by the Intergovernmental Panel on Climate Change. The temperature has also risen as New York has been covered with asphalt and concrete, creating an "urban heat island" that's estimated to have raised nighttime temperatures by 7 degrees Fahrenheit. The warming that has already occurred locally is on the same scale as what's expected globally in the next century.
The impact of these changes on Lower Manhattan isn't quite as striking as the computer graphics. We couldn't see any evidence of the higher sea level near the Bridge Cafe, mainly because Water Street isn't next to the water anymore. Dr. Lomborg and I had to walk over two-and-a-half blocks of landfill to reach the current shoreline.
The effect of the rising temperatures is more complicated to gauge. Hotter summer weather can indeed be fatal, as Al Gore likes us to remind audiences by citing the 35,000 deaths attributed to the 2003 heat wave in Europe. But there are a couple of confounding factors explained in Dr. Lomborg's new book, "Cool It: The Skeptical Environmentalist's Guide to Global Warming."
The first is that winter can be deadlier than summer. About seven times more deaths in Europe are attributed annually to cold weather (which aggravates circulatory and respiratory illness) than to hot weather, Dr. Lomborg notes, pointing to studies showing that a warmer planet would mean fewer temperature-related deaths in Europe and worldwide.
The second factor is that the weather matters a lot less than how people respond to it. Just because there are hotter summers in New York doesn't mean that more people die — in fact, just the reverse has occurred. Researchers led by Robert Davis, a climatologist at the University of Virginia, concluded that the number of heat-related deaths in New York in the 1990s was only a third as high as in the 1960s. The main reason is simple, and evident as you as walk into the Bridge Cafe on a warm afternoon: air-conditioning.
The lesson from our expedition is not that global warming is a trivial problem. Although Dr. Lomborg believes its dangers have been hyped, he agrees that global warming is real and will do more harm than good. He advocates a carbon tax and a treaty forcing nations to budget hefty increases for research into low-carbon energy technologies.
But the best strategy, he says, is to make the rest of the world as rich as New York, so that people elsewhere can afford to do things like shore up their coastlines and buy air conditioners. He calls Kyoto-style treaties to cut greenhouse-gas emissions a mistake because they cost too much and do too little too late. Even if the United States were to join in the Kyoto treaty, he notes, the cuts in emissions would merely postpone the projected rise in sea level by four years: from 2100 to 2104.
"We could spend all that money to cut emissions and end up with more land flooded next century because people would be poorer," Dr. Lomborg said as we surveyed Manhattan's expanded shoreline. "Wealth is a more important factor than sea-level rise in protecting you from the sea. You can draw maps showing 100 million people flooded out of their homes from global warming, but look at what's happened here in New York. It's the same story in Denmark and Holland — we've been gaining land as the sea rises."
Dr. Lomborg, who's best known (and most reviled in some circles) for an earlier book, "The Skeptical Environmentalist," runs the Copenhagen Consensus Center, which gathers economists to set priorities in tackling global problems. In his new book, he dismisses the Kyoto emissions cuts as a "feel-good" strategy because it sounds virtuous and lets politicians make promises they don't have to keep. He outlines an alternative "do-good" strategy that would cost less but accomplish more in dealing with climate change as well as more pressing threats like malaria, AIDS, polluted drinking water and malnutrition.
If you're worried about stronger hurricanes flooding coasts, he says, concentrate on limiting coastal development and expanding wetlands right now rather than trying to slightly delay warming decades from now. To give urbanites a break from hotter summers, concentrate on reducing the urban-heat-island effect. If cities planted more greenery and painted roofs and streets white, he says, they could more than offset the impact of global warming.
The biggest limitation to his cost-benefit analyses is that no one knows exactly what global warming will produce. It may not be worth taking expensive steps to forestall a one-foot rise in the sea level, but what if the seas rise much higher? Dr. Lomborg's critics argue that we owe it to future generations to prepare for the worst-case projections.
But preparing for the worst in future climate is expensive, which means less money for the most serious threats today — and later this century. You can imagine plenty of worst-case projections that have nothing to do with climate change, as Dr. Lomborg reminded me at the end of our expedition.
"No historian would look back at the last two centuries and rank the rising sea level here as one of the city's major problems," he said, sitting safely dry and cool inside the Bridge Cafe. "I don't think our descendants will thank us for leaving them poorer and less healthy just so we could do a little bit to slow global warming. I'd rather we were remembered for solving the other problems first."