The contrast of the current March weather to Spring last year could hardly be a greater swing (Daily Mail: What a difference a year makes: Mother’s Day daffodils delayed by the cold weather…) to the coldest March in 50 years in the UK. This year has certainly bucked the supposed climate change-induced trend towards warmer and earlier Springs.
In the final week of his tenure as the government’s chief scientific adviser Sir John Beddington perpetuated the extreme weather meme:
“The [current] variation we are seeing in temperature or rainfall is double the rate of the average.”
Well, he might like to consider a graph posted last week by The Telegraph showing March temperatures (HADCET) over the last 100 years. Does anything strike you about it?
Look at the period from the early 1960s to the mid-80s. Isn’t the relative stability of the [cooler] temperatures noticeable? Observe the see-saw year-to-year swings in temperature from the late 1930s to the early 60s – what did Britain experience in those years and would it count as ‘extreme weather’ now?
Climate science of course has an explanation (from The Guardian interviewing Jennifer Francis a research professor at Rutgers):
“…the Arctic ice loss adds heat to the ocean and atmosphere which shifts the position of the jet stream – the high-altitude river of air that steers storm systems and governs most weather in northern hemisphere.
“This is what is affecting the jet stream and leading to the extreme weather we are seeing in mid-latitudes,” she said. “It allows the cold air from the Arctic to plunge much further south. The pattern can be slow to change because the [southern] wave of the jet stream is getting bigger. It’s now at a near record position, so whatever weather you have now is going to stick around,” she said.
The heavy snowfall and freezing temperatures which have marked March 2013 across the northern hemisphere are in stark contrast to March 2012 when many countries experienced their warmest ever springs. The hypothesis that wind patterns are being changed because melting Arctic sea ice has exposed huge swaths of normally frozen ocean to the atmosphere would explain both the extremes of heat and cold, say the scientists.
But hang on, what about that earlier period of swings and see-sawing March temperatures? Didn’t we have less ice in the Arctic in the 1930s/40s (although in this period it was less well quantified). This does tend to be glossed over, but perhaps, just perhaps, it could be related to the temperature swings then.
Here’s the Atlantic Multidecadal Oscillation, plotted with March CET (source: Met Office HADCET) overlaid:
Although the fit is hardly perfect, the highlighted AMO positive anomalies do coincide with warmer March average temperatures and periods of greater extremes. I looked at other months; none show this pattern of temperature variation, except perhaps November.
Oh I do hate the tendency of climate science to forget the past and view changes as irreversible and in one direction.
Looking out my window, forlorn snowmen and small heaps snow from path clearing still sit in neighbourhood gardens ten days after the recent snowfall; icy dirt clings by the roadsides, and lifting my eyes to the hills I have every sympathy for the farmers struggling in the glittering whiteness.
They say ‘what you lose on the swings, you gain on the roundabouts’. Here’s hoping the passage round the sun this year brings us a warmer drier summer than last year. It wouldn’t be hard.