A study from researchers at the U.K.’s National Oceanography Centre has reached a paradoxical conclusion – global warming may cause a lowering of European temperatures, and it could happen very quickly.
The research team’s conclusions, as reported in the scientific journal Nature, are based on observations of the Gulf Stream over a period of 50 years. They’ve concluded that the current is weakening, and, as a result, less warm water, and consequently less heat, is being transferred from the mid-Atlantic towards the North.
While the study focused almost exclusively on possible changes in Europe’s climate, it also mentioned a rather ominous consequence for the mid-Atlantic/Caribbean area. The gulf current not only flows north and south, but also in a circle across the Atlantic and back. If less heat is going north, more will be retained in this oceanic movement, which could well result in further raising the water temperature and, as a result, the atmospheric temperature, in the Caribbean and along the southeastern coast of the U.S. That in turn could well increase the frequency and intensity of the tropical storms – Katrina et. al. – that have caused severe damage and loss of life.
The study, a joint project of the U.K.’s National Environment Research Council (NERC) and Project Rapid, a group examining the possibility of rapid climate change, explains that the Gulf Stream operates somewhat like a conveyor belt. It carries warm water north, which gradually cools and sinks, as it gets colder, a process referred to as “overturning.”
“It’s like a radiator giving its heat to the atmosphere,” Harry Bryden from the National Oceanography Centre (NOC) at Britain’s Southampton University, said in a BBCinterview.
This cooled water then flows back south at greater depths. NOC researchers concentrated on the colder water, and found that over the last half century, these currents have changed markedly. “We saw a 30 percent decline in the southwards flow of deep cold water,” Bryden told the BBC. “And so the summary is that in 2004, we have a larger circulating current [in the tropical Atlantic] and less overturning.”
The rapid melting of the Arctic ice cap is apparently affecting the mechanism. As the northeastern branch flows, it gives off heat to the atmosphere, which in turn warms European land. less heat equals less warming.
The Rapid Project’s bulletin notes: “If global warming shuts down the Atlantic heat conveyor – known to oceanographers and climate scientists as the Atlantic thermohaline circulation or THC, and to the rest of us somewhat inaccurately as the Gulf Stream,” the U.K. in particular and the rest of Europe in general could face a “future of freezing winters, late springs and early autumns.”
The bulletin explained why, as follows: “The ocean is a moderating influence on climate in Western Europe. Warm water from the Caribbean and Gulf of Mexico flows north and east across the Atlantic. Heat from the tropics is released to the atmosphere and makes our climate warmer and wetter than expected from the latitude we’re at. Were this flow to stop our winters would become like those at similar latitudes on the shores of the Pacific and western Atlantic. Just a slow-down would have serious consequences. It has happened before. Possibly more than once since the last ice age. And paradoxically at least one of these events was a direct result of the Earth becoming warmer.”
The explanation for that – given by the BBC – is: “As Arctic ice melts and Arctic rivers flow faster – trends which have both been documented – the northern oceans become less saline. Less salinity means a lower density; the waters then cannot sink, so the conveyor weakens. Computer models have predicted that if it turned off completely, Europe would cool by perhaps four to six degrees Celsius (app. 7.2 to 11 F).”
How soon could this happen? The estimates vary from never – different variables could reverse the process – to very soon, i.e. within 10 years or so, if the melting of the Arctic ice cap increases substantially.
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