Climate change slowdown is due to warming of deep oceans
A recent slowdown in the upward march of global temperatures is likely to be the result of the slow warming of the deep oceans, British scientists said on Monday.
Oceans are some of the Earth's biggest absorbers of heat, which can be seen in effects such as sea level rises, caused by the expansion of large bodies of water as they warm. The absorption goes on over long periods, as heat from the surface is gradually circulated to the lower reaches of the seas.
Temperatures around the world have been broadly static over the past five years, though they were still significantly above historic norms, and the years from 2000 to 2012 comprise most of the 14 hottest years ever recorded. The scientists said the evidence still clearly pointed to a continuation of global warming in the coming decades as greenhouse gases in the atmosphere contribute to climate change.
This summer's heatwave, the most prolonged period of hot weather in the UK for years, has not yet been taken into account in their measurements.
Peter Stott of the Met Office said computer-generated climate models all showed that periods of slower warming were to be expected as part of the natural variation of the climate cycle, and did not contradict predictions. Given that variation, current temperatures are within expectations. As well as the heating of the deep oceans, other factors have played a significant part in slowing temperature rises. These have included the solar minimum - when the sun is less active and generating slightly less heat, as occurred in 2008/2009 - and a series of small volcanic eruptions, including that of Iceland's EyjafjallajÃ¶kull volcano in 2010. Ash from volcanoes reflects light back into space, and major eruptions in the past have had a severe, albeit temporary, cooling effect.
Despite the slowdown in warming, by 2060 the world is still likely to have experienced average temperatures of more than 2C above pre-industrial levels - a threshold that scientists regard as the limit of safety, beyond which climate change impacts are likely to become catastrophic. Prof Rowan Sutton, director of climate research at the National Centre for Atmospheric Research at Reading University, said the current pause would only delay reaching this point by five to 10 years.
Continue reading at The Ecologist.
Ocean image via Shutterstock.