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Met Office Washout Claims Get A Cool Reception

Gabrielle Monaghan, The Sunday Times

Some climate change scientists are getting hot under the collar over last week’s claims that we are facing a decade of washout summers.

One Irish climatologist is predicting that the freak weather conditions may end as soon as next year.

Stephen Belcher, head of the Hadley Centre for climate research at the UK’s Met Office, foresees a cycle of wetter summers for up to a decade, as a result of changes in ocean surface temperatures known as the Atlantic multidecadal oscillation (AMO).

Speaking at a scientific workshop in Exeter last week, Belcher did stress it was far too early to be certain about a “very experimental forecast”.

While Ireland has so far experienced higher summer temperatures than many parts of Europe, the previous six summers have been wet and cool.

John Sweeney, a professor of geography at NUI Maynooth, does not believe future summers will be at the mercy of the AMO cycle, which increases the prospects of rain.

“I do not think we are stuck in a 10- to 20-year cycle of wet summers and cold winters,” he said. “I think we will revert back to a more normal climate this year or next.

“We’ve warmed up by 0.7 degrees in the past 50 years, but the past three years have been anomalous. I don’t think this is the beginning of a new trend.”

After last week’s workshop, the UK Met Office complained that some of the media coverage did not “capture the science” of its press briefing.

Climate scientists from the University of Reading had partly blamed the higher odds of wetter summers over the next decade on a warm stage of the AMO cycle in the north Atlantic which began in the late 1990s.

Belcher said this cycle of contrasts between warm and cold water may be steering the jet stream, a meandering ribbon of air high in the atmosphere that typically brings settled weather to Ireland during the summer by keeping rainstorms further north.

The jet stream shifted its position to the south of the UK and Ireland last summer and this spring.

Sweeney said researchers need to investigate whether the jet stream being “locked in unusual positions for long periods” and the AMO are having a short-term effect on Ireland’s climate.

“The jet stream changes are more linked to human activity, and oceanic temperatures are more about natural variability,” he said. “You’re getting two competing processes and we don’t know yet which one is going to break first.”

Ray McGrath, head of research at Met Eireann, agrees with Sweeney. He said indications from EC-Earth, a European project that uses computer models to simulate climate change, point to warmer, drier summers over the next 30 years as a result of climate change, with some exceptions due to natural variability.

“We’ve had a few rough years of bad summers and winters but I don’t see that continuing in the future, though you can’t rule out the odd bad year,” said McGrath, who sits on EC-Earth’s steering committee.

Some Irish climatologists also take a pessimistic view of the AMO’s influence on summer weather. Kieran Hickey, a climate-change expert at NUI Galway, has predicted the AMO’s warming stage is likely to produce more wet summers by 2020.

McGrath believes there have been too many factors involved in unusual seasons over the past three years to discern one cause.

“It’s been said [last year’s] bad summer was caused by the jet stream being too far south, but you could just as well say the jet stream being south was a symptom of the bad summer,” he said.

“There is a lot of speculation about what’s driving the extreme conditions, but it is not easy to determine the root cause of it. It’s a thorny issue.”

The Sunday Times, 23 June 2013