Today, as in recent years, we see ample evidence that extra heat in the atmosphere and oceans can severely alter weather around the world.
We are seeing the impacts in Brazil where Sao Paulo reservoirs are now at 4.5 percent capacity and millions are suffering from inadequate and dwindling water supplies. We see similar stress in California where the worst drought in decades is forcing some communities to truck in water. In Syria the situation is even more dire — on the scale of a humanitarian nightmare — where a multi-year drought has destabilized government and spurred violent extremism to surge through an already troubled region.
(Sao Paulo region of Eastern Brazil clearly visible through a mostly cloudless but smoke-filled satellite shot on October 15. Note both the dessicated, browned land of a normally green region together with the steely gray smoke funneling in from wildfires both near Sao Paulo and further north in the drying Amazon rainforest. Intense heat and lack of rainfall combines with fires to create a pallor of smog over much of Brazil also visible here. Image source: LANCE-MODIS.)
In a warming world, drought and deluge are far more common. The added heat increases the rate of evaporation and amplifies the hydrological cycle such that the atmosphere holds 6 to 7.5 percent more moisture per each degree Celsius of heating. This is roughly equal to an increase in the rate of evaporation and precipitation by 6 to 7.5 percent as well. So where droughts occur, they will tend to be more severe and where strong storms develop, they will tend to dump even heavier volumes of rainfall. And a warming of the polar regions coincident with snow and ice loss, plays havoc with both the Jet Stream and traditional storm tracks even as the increased instability generates ever-more-powerful storms.
For a Europe facing off against an Atlantic and Arctic undergoing these wrenching changes, the story is altogether related. Sections of Southern France over a recent six week period received enough rain for an entire year. The Mediterranean waters off this region had heated to between 3 and 4 C above average dumping an intense load of moisture into a hungry upper level low that delivered storm after storm to the beleaguered regions. One spate of deluge dumped a full six months of water from the skies in just three hours.
(Monster storm that bombed out to 952 mb on Wednesday lashes the UK and Ireland with rain and gales on Friday and Hurricane Gonzalo threatens Bermuda. Gonzalo is set to make an eastward turn across the Atlantic and will possibly impact the UK as a tropical storm by Monday or Tuesday of next week. Image source: LANCE-MODIS.)
This week, one such storm swelled to extraordinary intensity in the North Atlantic. On Tuesday and Wednesday it bombed out to a powerful 952 mb monster, filling up most of the Ocean between Newfoundland, Greenland and Europe, casting gales on into the UK and Ireland. It sent storm surges up rivers — forcing them to top their banks, lashed the isles with rainstorms that flooded Belfast, damaged hundreds of homes and sent officials scrambling to assure an already storm-weary public that they were better prepared for such events than last year.
The current storm is expected to rake through the UK and Ireland throughout this weekend before fading off toward the north. As it lifts, hurricane Gonzalo — now packing 125 mph winds and threatening Bermuda — is forecast to surge into the UK with tropical storm intensity come Monday or Tuesday of next week.
(Forecast path for Gonzalo shows a tropical storm off Ireland by Monday morning. Image source: NOAA.)
The 1-2 punch is reminiscent of a relentless series of storms that battered the UK this past winter. A sequence spurred by extraordinary and unprecedented changes to the North Atlantic climate including a slowing of the Gulf Stream, a powerful warming of surface waters in the Arctic, major losses to sea ice in almost all Arctic seas, and increasing cold, fresh water outflows from Greenland. The net effect is to enhance storm track intensity across the Atlantic as warmer waters and airs surge northward coming increasingly into contact with cold polar air and generating powerful and intense storms during the winter, fall, and spring seasons.
With global temperatures flirting with new record highs and with El Nino possibly flaring to life in the Pacific, the end of 2014 and the start to 2015 is altogether likely to see a continuation of such intense, extreme weather. Weather that is severe enough to cause damage and disruption in some areas or even powerful enough to throw whole cities and regions into instability.
Just a few of the tragic results of a warming climate as we approach the 1 C above 1880s temperatures mark.
Hat Tip to Colorado Bob
Hat Tip to Bernard