Irma, and the rise of extreme rain
It stands to reason: Warmer water produces greater rainfall
Warm air can carry more water than cool air. You may understand this intuitively. The greater moisture of warm air explains why your skin gets less dry in the summer and why the forests of the sweltering Amazon get a lot more precipitation than those in northern Canada.
About 40 years ago, the earth’s surface temperatures began to break out of their recent historical range and kept climbing. Not coincidentally, the number of storms with extreme rainfall began to increase around the same time. They’re up more than a third since the early 1980s, according to research by Kenneth Kunkel of the North Carolina Institute for Climate Studies.
Mr. Kunkel’s threshold for an “extreme” rainstorm varies by region, depending on how much rain a place typically receives. It’s a count of storms that would ordinarily occur only once every few years — the type of storms that stretch a community’ s capacity to cope.
The main reason these storms seem more frequent is global warming. Gabriel Vecchi, a Princeton researcher, compares warmer air to a bigger bucket: It can carry more water from oceans and then dump that wateron land.
Yes, the connection between weather events and climate change can be complicated. Even as most places get more rain, for example, some dry places have sufferedmore droughts.
Yetthere is overwhelming evidence that climate change is altering the weather. Irma and Harvey weren’t caused by climate change, but they almost certainly would not have been so powerful if the air and the seas fueling them hadn’tbeen so warm.
And the rise of extreme rainstorms isn’t limited to hurricanes. “Heavy precipitation events” in most parts of the U.S. have increased, says the latest draft of the National Climate Assessment, written by scientists who are careful not to overclaim. “There is strong evidence,” it continues, “that increased water vapor resulting from higher temperatures is the primarycause.”
The changes in weather already are doing damage, and they will accelerate as theplanet warms.
Look at Florida. Irma, thank goodness, made a late turn and caused less damage than feared. Yet Florida faces problems much bigger than any one storm. The increased rain is falling into seas swollen by melted ice caps. Florida is also the flattest state, barely above sea level. As a result, floods and severe “king tides” have becomemore common.
The city of Hallandale Beach has closed drinking wells inundated by saltwater. In 2013, Miami Beach elected a mayor who ran a campaign ad that showed him getting ready to commute by kayak. The Coral Gables mayor worries about boats ramming into bridges because of rising canals.
Welcome to the era of extreme rain. We can continue to pretend it’s all a coincidence and watch the consequences mount. Or we can start to do something about it — by using less of the dirty energy that’s changing the climate and by preparing for a future that’s guaranteed to be hotter and rainier.