Last winter’s weather might have been extreme but according to a new report it was within ‘normal variability’
THE HEAVY rainfalls and the resultant floods they caused last November were not triggered by climate change. Nor does the big chill that froze things solid at the turn of the year mean that global warming has somehow passed us by.
Both events – though certainly extreme – were within the range of “natural variability”, according to a study published this morning by the Royal Irish Academy.
The widespread flooding along the west coast from Galway down to Cork sparked considerable public concern. There were fears that submerged homes would now be the norm due to climate change.
These fears are misplaced however, according to Prof Ray Bates, chairman of the RIA’s climate change sciences committee.
“We are not saying global warming is not significant, it is very significant,” he said in advance of the report’s launch. Climate change induced by human activity remains “a long-term threat”, he says.
The Academy’s committee decided to produce the report because of fears that the November events would become a regular feature, he said.
The report was authored by Ray McGrath and Tom Sheridan of Met Eireann and Rowan Fealy of NUI Maynooth, all members of the Academy’s climate committee.
“The idea came from Ray McGrath after a lot of calls started to come in to Met Eireann after the floods,” Bates says.
Then there were the climate-change sceptics who pointed to the freezing conditions in January as a sign that the earth was no longer warming due to human activity.
The committee feared that the whole message about the long-term threat posed by climate change could be “undermined” by sceptics. It therefore put together this morning’s report to clarify the reality of the situation, Bates says. Certainly the report accepted the rain that caused the flooding was out of the ordinary. That month saw rainfall figures range from two to three times normal monthly amounts and many records were set.
“The report says that what happened in November 2009 was a very extreme event, something you would expect to see happen once every 500 years. It was an out-of-the-blue extreme event,” Bates says.
The report also accepts the current view we will likely see heavier rainfall here as a result of human-induced climate change.
Even so, the analysis of decades of weather records indicates the event was not outside the possible range of rainfall. “It is likely to be linked to natural climate variability, combined with a small expected increase in rainfall due to [human] driven climate change,” the report says.
The contribution currently made by climate change is small, so much so that it could not have been seen amid the wash of rain that fell in November. Bates estimates that we should expect about a 6 per cent increased rainfall for every degree rise in average temperatures. This would have been invisible against the up to 300 per cent higher rainfall that occurred that month.
The freezing weather that came late in 2009 and ran on into January 2010 also represented natural variability, Bates says as highlighted in the RIA report.
While it was the most extreme weather seen in many parts of the country since 1963, it was in line with that year and other cold snaps that took place in the 1940s, 1970s and 1980s. It was caused by a weather phenomenon known as the “Arctic Oscillation” which comes when the normal pattern of air pressure changes. It brought clear skies with cold Arctic air flowing down over us.
While temperatures for the month were two to three degrees below normal here and across much of northern Europe, in global terms the month was the fourth warmest January on record since 1880, the report says. This means that while we did experience exceptional cold global warming continues apace.
The reason for the research was to put people’s minds at rest, Prof Bates said. “I hope it allays some people’s concerns that we will see these floods every year.”
See the full report at: ria.ie
Twitter: @dickahlstrom
