PRESIDENT TRUMP assured the nation over the weekend that he is "closely monitoring" the disaster in Texas. "We have an all out effort going, and going well!" he tweeted.
Scientists are habitually cautious about attributing a single weather event to the long-term increase in global temperature that human beings have begun, and they cannot say with reasonable certainty that climate change caused Hurricane Harvey. In fact, they are still sorting out exactly how global warming affects hurricane formation. It seems likely that an increase in North Atlantic hurricanes is linked to climate change, but scientists cannot confidently rule out some other factor.
What they can say — and have, emphatically, since this hurricane slammed into Houston — is that "Harvey was almost certainly more intense than it would have been in the absence of human-caused warming," as climate scientist Michael E. Mann wrote in the Guardian. The surge of water this storm churned up out of the Gulf of Mexico was half a foot higher than it would have been without the rising sea level, he reckoned. This storm surge not only endangered coastal-zone communities such as Galveston, but local experts report it also blocked water drainage from inland areas that heavy rains have inundated.
Warmer surface water temperatures — and they have been very warm in the Gulf of Mexico lately — mean more water vapor in the atmosphere. "This means that when we get the right circumstances for very extreme rainfall to occur, climate change is likely to make these events even worse than they would have been otherwise," Andrew King, climate extremes research fellow at Australia's University of Melbourne, explained. " Wetter skies mean more intense rain."
Water below the surface is warm, too. That subsurface warmth appears to have helped fuel Harvey even as it approached land, where storms typically begin to struggle.
Houston is an example of what happens when public officials ignore experts and refuse to take natural risks seriously. As the country's fourth-largest city expanded, replacing prairie with impermeable surfaces such as pavement and concrete, the land was rendered less and less capable of absorbing floodwater. Without proper adaptive measures, this made an already flood-prone place more vulnerable. A ProPublica and Texas Tribune investigation found last year that those who have overseen Houston's flooding issues discounted scientists' warnings as "anti-development." In the coming months and years, the city may pay a high price for such shortsightedness.
Those officials had the fate of only one city in their hands. Mr. Trump has the fate of the whole world.
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