Warming pause 'not unexpected'

The current "pause" in global warming is not unexpected and does not alter the overall picture of rising temperatures, climate scientists have said.

Heat going into the deep ocean is part of the reason global average surface temperatures have increased at a lower rate in the past 10 to 15 years than in previous decades, experts said.

Recent low solar activity and volcanic eruptions, which send particles into the atmosphere that reflect heat, have also contributed to a slowing in temperature rises, while natural climate variations also play a part. Global warming has not stopped but the average rate of warming was just 0.04C per decade between 1998 and 2012, compared with 0.17C per decade from 1970-1998.

Recent measurements of deep-ocean temperatures indicate heat is being absorbed at lower levels, which the researchers suggest could be due to a period of more circulation within the ocean, taking heat into the deep where it is "hidden from view".

But Met Office experts and climate scientists said periods of slow-down or "pauses" in surface warming are not unusual in temperature records and are predicted in climate models, which suggests such periods could occur at least twice a century because of natural variation.

Computer models for how the climate could change have not predicted the current slow-down, although Dr Richard Allan of the University of Reading said long-term projections do show decades of slower warming but could not be expected to exactly match when they occur in real life. Over a 50-year period, the world could expect to see one period of extra rapid temperature rises, Dr Allan said.

The temperatures seen in recent years fall within the range previously predicted, and if models for future rises take into account temperatures from the last 10 years, the most likely warming is reduced by 10%, the experts said.

This would mean that the world would see rises of 2C above pre-industrial temperatures, beyond which the worst impacts of climate change are expected to occur, and only around five to 10 years later than currently predicted.

Professor Piers Forster, at the University of Leeds, said: "If we do continue on this emissions trajectory we're currently on, we'll reach 2C in 2060 or so. I think it puts it back by five to 10 years."

Dr Peter Stott, of the Met Office Hadley Centre, said: "We expect to get periods of slower warming. This is absolutely what we expect. Global temperatures remain high: 12 out of the 14 hottest years on record have occurred since 2000."