Potsdam this year is 7F warmer than it averaged in the century before 1980. Berkeley is now Santa Barbara: Stefan Rahmstorf: Europe’s freak weather, explained: "Naive.... The smoothed curve shows... global warming... the scattering of the grey bars... random variations of the weather.... Slightly more than half of the 4.3 degrees would be due to global warming, the rest to weather. That... likely underestimates the contribution of climate change...
...Not only is the current outlier by far the biggest, there is growing evidence that the “rest of the weather” is not just random but has already been altered by climate change too. This is currently one of the hottest topics in climate research. The basic idea is that the jet stream—a band of high winds around the Northern Hemisphere that significantly influences our weather in the mid-latitudes—is changing... has... slowed down... undulates more. The cause is probably the strong warming of the Arctic, as the jet stream is driven by the temperature contrast between the tropics and the Arctic.... A certain wave pattern in the jet stream, meandering from north to south, settles for a long time and brings heat and drought or continuous rain, depending on where you are in this pattern. Such a persistent jet stream pattern has played an important role in the weather extremes of recent weeks, connecting the extremes around the Northern Hemisphere....
Ocean circulation may also have played a role, in particular the Gulf Stream System.... Particularly cold surface water in the subpolar North Atlantic favors summer heat in Europe, again by changing the pattern of highs and lows in the atmosphere and thus the undulations of the jet stream. This happened in the “summer of the century” in 2003 and the heat wave of 2015. The reality of global warming is catching up with us fast, and no longer an issue for future generations. That year even saw the coldest temperatures on record in the subpolar Atlantic—the only region on Earth that has defied global warming and cooled instead. Such cold in the North Atlantic is occurring more and more frequently because the Gulf Stream System is weakening, as has been predicted by climate models in response to global warming.
Climate change does not just mean that everything is gradually getting warmer: It is also changing the major circulations of our atmosphere and ocean. This is making the weather increasingly weird and unpredictable. The reality of global warming is catching up with us fast, and no longer an issue for future generations. We will need to prepare for more unpleasant surprises in the coming years, and we need to urgently cut down emissions to prevent further destabilizing our climate system...
#shouldread
#globalearming
