Investigacions recents de Stephan Rahmstorf i d’altres demostren que els huracans són cada vegada més forts a causa del canvi climàtic causat per l’home. Malauradament, aquest no és l’únic impacte en la destrucció. A causa de canvis en la circulació atmosfèrica, la velocitat dels huracans també està disminuint. El que fa que els seus efectes destructius durin més temps en una regió determinada.
Segons les noves investigacions publicades per Nature i escrites per James Kossin, la velocitat d’avenç dels huracans en els tròpics s’està alentint. Aquesta disminució és impulsada per un debilitament de la circulació atmosfèrica tropical. Aquest afebliment ha estat identificat per estudis climàtics durant dècades i s’associa amb un clima d’escalfament.
Recent research by Stephan Rahmstorf and others shows that hurricanes are growing stronger due to human-caused climate change. Unfortunately, this is not the only destruction-enhancing impact. Due to changes in atmospheric circulation, the forward speed of hurricanes is also slowing down. Which makes their destructive effects last longer over a given region.
(Stronger, slower hurricanes means longer-lasting destructive impacts.)
According to new research published by Nature and written by James Kossin, the forward speed of hurricanes in the tropics is slowing down. This slow-down is driven by a weakening of tropical atmospheric circulation. Such weakening has been identified by climate studies for decades and is associated with a warming climate.
As the Earth warms, the Hadley Cell expands and slows, the poles warm faster than the lower latitudes generating more blocking patterns in the middle latitudes, and the Walker Cell also slows down. The net effect is that steering currents for hurricanes are weaker, which reduces their forward speed.
(Observed reduction in hurricane forward motion since 1950. Image source: A global slow-down in tropical cyclone translation speed.)
Reduced forward speed means that hurricane impacts such as strong winds and heavy rain persist for longer periods over a given area. Such longer persistence produces more damage and higher rainfall totals.
Since storms are already increasing in intensity due to warming ocean surfaces, rainfall rates and wind speeds are on the rise. However, these much more powerful storms are becoming brutally slow. The net effect is a pretty terrible combination for cities and regions facing the climate change enhanced storms of today and tomorrow.
(Not a fluke event. The catastrophic flooding produced by Hurricane Harvey is much more likely to occur in a warming world as storms intensify and persist for longer periods over a given region. Image source: The National Weather Service.)
With the world having already warmed by about 1.1 C above 1880s averages, and with the oceans continuing to gain a tremendous amount of heat, we have already seen substantial changes to hurricane severity. However, if fossil fuel burning continues, that severity — both in terms of storm strength and persistence, is likely to continue to increase along with their related catastrophic effects.