Just a year ago we were dealing with an historically devastating Atlantic hurricane season. It was marked by the strongest hurricane – Irma – ever observed in the open Atlantic, the near total devastation of Puerto Rico by a similarly powerful category 5 monster Maria, and Hurricane Harvey – the worst flooding event in US history. At the time, I commented here and elsewhere about the role climate change had played in amplifying the destructive characteristics of these storms.
Not to be outdone, the 2018 Atlantic hurricane season, initially predicted to be quiet – quelled by an incipient El Niño event and cool, early summer ocean waters – has suddenly erupted. If the current disturbance in the western Gulf of Mexico known as “95L” earns the status of tropical storm, the 2018 season will be the second time in recorded history that we’ve seen five tropical storms simultaneously present in the Atlantic basin (the last time was in 1971).
What happened to cause all of this? An early autumn ocean “heat wave” has brought sea surface temperatures in the western Atlantic to bathtub-level warmth. Just as summer heat waves on land are greatly increased in frequency and intensity by even modest overall warming, so too are these ocean heat waves becoming more frequent and more extreme as the oceans continue warm. All else being equal, warmer oceans mean more energy to intensify tropical storms and hurricanes.
But when it comes to coastal threat, it hardly matters how many tropical storms there are over the course of the season. A single landfalling hurricane can wreak havoc and destruction. Think Katrina in 2005, Irene in 2011, Sandy in 2012, either Harvey or Maria in 2017 and now Florence in 2018.
In this sense, the sometimes fractious debate about whether we’ll see more or fewer storms in a warmer world is somewhat misplaced. What matters is that there is a consensus we’ll see stronger and worse flood-producing storms – and, in fact, we’re seeing them already. That brings us to Hurricane Florence: a climatologically-amplified triple threat. [Continue reading…]