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Monday, September 28, 2015

Sept 2015 is hotter in Chennai ~so also Globally excepting south of Greenland

The September is about to close ~ Sunday was hot and sweltering; few hours out in the noon – one felt very thirsty and felt like drinking more cool drinks.  It is time South-west monsoon would fade.

One felt that summer is not yet over perhaps as days are hot and one needs airconditioners in the night – has the weather pattern changed completely.  We hear people say that every year that Chennai was never like this before and it is much hotter than it was last year.  Is that true ?  IMD statistics reveal that in Tamilnadu this season had rains of 237.5 mm against 289.2 mm representing 20% short.  In Chennai, it is relatively better with 8% shortage only.

Well, it is not our perception – but is a scientific fact ~ it is hotter not here alone, but globally too.  Scientists have a theory about why the planet is going through a record warm stretch except for one  area near Greenland.  An interesting report in ‘Washing Post’ states that it  is an extremely warm year for our planet.

Only recently, the  National Oceanic and Atmospheric Administration revealed that the first eight months of 2015 were the hottest such stretch yet recorded for the globe's surface land and oceans, based on temperature records going to 1880. It's just the latest evidence that we are, indeed, on course for a record-breaking warm year in 2015. Before reading further  - see this interesting illustration of land and ocean temperature percentiles from January to August 2015. Source :  National Oceanic and Atmospheric Administration's National Centres for Environmental Information

It shows that the World is getting hotter, but yet in one part, in the North Atlantic Ocean, south of Greenland and Iceland, the ocean surface has had very cold temperatures for the past eight months.  First of all, it's no error. Deke Arndt, chief of the climate monitoring branch at NOAA's National Centres for Environmental Information, confirmed what the map above suggests - some parts of the North Atlantic Ocean had record cold in the past eight months. As Arndt said in an email: "For the grid boxes in darkest blue, they had their coldest Jan-Aug on record, and in order for a grid box to be 'eligible' for that map, it needs at least 80 years of Jan-Aug values on the record."

"It's pretty densely populated by buoys, and at least parts of that region are really active shipping lanes, so there's quite a lot of observations in the area," Dr Arndt said. "So I think it's pretty robust analysis." So, the record seems to be a meaningful one - and there is a much larger surrounding area that, although not absolutely the coldest it has been on record, is also unusually cold.

While there may not yet be any scientific consensus on the matter, at least some scientists suspect that the cooling seen in these maps is no fluke but, rather, part of a process that has long been feared by climate researchers - the slowing of Atlantic Ocean circulation. In March, several top climate scientists, including Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research and Michael Mann of Penn State, published a paper in Nature Climate Change suggesting that the gigantic ocean current known as the Atlantic Meridional Overturning Circulation, or AMOC, is weakening. It is sometimes confused with the "Gulf Stream" but, in fact, that is just a southern branch of it.

The current is driven by differences in the temperature and salinity of ocean water. In essence, cold salty water in the North Atlantic sinks because it is denser, and warmer water from further south moves northward to take its place, carrying tremendous heat energy along the way. But a large injection of cold, fresh water can, theoretically, mess it all up - preventing the sinking that would otherwise occur and, thus, weakening the circulation. In the Nature Climate Change paper, the researchers suggested that this source of fresh water is the melting of Greenland, which is now losing more than a hundred billion tonnes of ice each year.

It is stated that the fact that a record-hot planet Earth coincides with a record-cold northern Atlantic is quite stunning. The accelerated melting of the Greenland ice sheet will continue to contribute to this decline by diluting the ocean waters." It's not clear that all climate scientists agree with this interpretation of what's happening in the North Atlantic - but clearly some important ones do, and they have published their conclusions in an influential journal.

Washington Post in another article states that a hundred years from now, humans may remember 2014 as the year that we first learned that we may have irreversibly destabilized the great ice sheet of West Antarctica, and thus set in motion more than 10 feet of sea level rise. Meanwhile, 2015 could be the year of the double whammy — when we learned the same about one gigantic glacier of East Antarctica, which could set in motion roughly the same amount all over again. Northern Hemisphere residents and Americans in particular should take note — when the bottom of the world loses vast amounts of ice, those of us living closer to its top get more sea level rise than the rest of the planet, thanks to the law of gravity.

 “The idea of warm ocean water eroding the ice in West Antarctica, what we’re finding is that may well be applicable in East Antarctica as well,” says Martin Siegert, a co-author of the study and who is based at the Grantham Institute at Imperial College London…………. … ..and they do sound alarming for the humanity.

With regards – S. Sampathkumar
28th Sept. 2015.


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