July 22, 2013 8:24 pm

UK climate scientists say oceans hold key as global warming slows

As the UK basked in the results of its latest record – its longest heatwave for 18 years – climate scientists, for their part, were presenting details about the recent slowdown in global warming.

Scientists from the Met Office’s Hadley climate centre and some UK universities said on Monday that the oceans appear to hold the key to one of the biggest puzzles in climate change science.

The rise in global average temperatures at the earth’s surface has been smaller in the past 15 years than in previous decades, even though emissions of the greenhouse gases that warm the atmosphere have continued to soar.

Climate change sceptics say this shows global warming is not as big a problem as has been thought and may even be stopping.

There is no evidence to support this theory, the UK scientists said, pointing to the long-term warming trend dating back to 1860 that includes similar periods of slowing temperature rises, and additional evidence of global warming such as rapid Arctic sea ice melting and rises in sea levels around the world.

A range of factors have been pinpointed for what has come to be called the “hiatus” or “pause” in warming, which the scientists said they expected to be temporary.

These include small airborne particles known as aerosols from volcanic eruptions that have a cooling effect as they reflect sunlight back into space; the impact of the regular cycle of solar activity; the sensitivity of the climate to greenhouse gases, and the way the oceans absorb heat.

“We don’t fully understand the relative importance of these different factors,” Professor Rowan Sutton of the University of Reading said at a briefing with Met Office scientists in London.

But as sea temperature measuring becomes more advanced, it is becoming clear that absorption of heat in the deepest part of the oceans is likely to be a part of the explanation, the scientists said.

A network of robotic probes that float around and down into the ocean has shown some evidence of warming as far down as 2,000m and below, though the Met Office scientists say much more research will be needed to be certain about exactly what has caused the slowdown.

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