Conditions are perfect to send this year’s tropical storms off the charts
Tropical storms get the majority of their power from sea surface temperatures. As a storm travels over the surface of the sea, it picks up ever more heat to fuel its intensity from the surface waters. Heat is the engine that gives a hurricane its incredible force, fuelling higher and higher wind speeds.
The past eight years have been the eight warmest years since we first started using thermometers to measure temperatures and keep records. They’re also the warmest in at least 125,000 years before that, and they’re getting warmer much faster than natural processes changed things in previous climate shifts. We’ve already crammed a lot more warming into the pipeline than Earth has seen in tens of millions of years, which hasn't caught up to us yet but is inescapably on its way. The imminent return of El Niño will push temperatures yet higher. 90% of warming is going into our oceans, so sea surface temperatures are also breaking records, ready to turbocharge megahurricanes. Once El Niño begins, stronger wind shear occurs over the Caribbean and Northern Atlantic. That can inhibit hurricane formation, which is why we don’t necessarily expect a greater number of hurricanes, but it won’t prevent hot surface waters from adding to the intensity of tropical storms that do occur. Nor will it impede storm formation in the Pacific.
As heat drives the speed of a hurricane’s punch, all the water it carries provides the mass of its impact. A warmer atmosphere holds more water. Heat the air by one degree Celsius, and it can carry 7% more moisture. Already warming the entire planet’s atmosphere by 1.2º C means more than a thousand cubic kilometres of extra what-goes-up-must-come-down in the sky over our heads. Hurricanes can now arrive with a million watery tons of extra fury. That’s how hurricane Harvey could dump a deluge of rainfall over parts of Texas as much as 153.87 cm (60.58 inches) deep. Records for flooding are toppling over and over again so frequently that South Carolina actually had six “once in a thousand year” rainfall events in less than six years.
Harvey’s astonishing deluge was also made possible because it stalled in place for days, subjecting…