Researchers Say U.S. Hurricane Tab of $14 Billion and Counting Result of Global Warming

Climate change has added billions to the toll of hurricane strikes on the U.S., according to a study that challenges the prevailing scientific view that the rising cost is mainly because more buildings, towns and businesses are in the way.

Stronger, more frequent storms may have accounted for as much as $14 billion of hurricane damage in 2005, the year Hurricane Katrina slammed into the Gulf Coast, according to research published Monday in the journal Nature Geoscience. The cost, as much as 12 percent of total U.S. damage that year, is over and above what can be explained by coastal development alone, the scientists said.

“The main message is we have to be more cautious with climate change and reassess our estimates of how much it’s going to cost us,” lead author Francisco Estrada, an economist at National Autonomous University of Mexico, in Mexico City, said in a telephone interview. “The conclusion that there is no climate change signal in extreme events is no longer valid.”

While scientists are virtually unanimous in saying humans are warming the planet, there’s less certainty about the resulting effect on hurricanes. A study published in May said warmer ocean temperatures may decrease the number of tropical storms but make those that do form more powerful. There’s equal debate about how much blame should be tied to climate change for rising storm costs in the U.S., which increased at the rate of $136 million a year over the last century, according to Estrada.

Past studies have concluded that the higher costs are mainly a function of building more homes and businesses along the coast, as well as the rising value of that property, and not due to storms juiced up by global warming.

In the paper, Estrada and two European researchers say previous studies ignored the fact that more development often comes with added protection against hurricanes, from sea walls and stricter building codes to better early-warning systems. Those protections tend to reduce damages and may hide the effect of weather getting stronger, the scientists said.

“Increases in wealth and population alone cannot account for the observed trend in hurricane losses,” the researchers wrote.

“If you look at the scientific literature, the consensus is the climate change signal won’t appear in hurricanes until the end of this century,” Estrada said. “What we are saying is that it’s already there.”

The findings “re-open the largely discounted debate on the role of climate change in hurricane losses,” World Bank economist Stephane Hallegatte said in an editorial accompanying the study. It confirms the need to cut greenhouse gases and “reduce the very uncertain long-term risks that would be created by an unabated change in climate.