May 3rd 2017, June 17th 2016

The seasons are on a seesaw; there’s no smooth forward motion. Thus it was that we found ourselves dipped back into winter a couple of weeks ago, sometimes in and out a few times within a single day. The sun was warm, warm enough to animate hoverflies which emerged to vigorously defend their own favourite sunspot, but the air temperature hovered at around 10 degrees.

Lurking not far above was even colder air, since Britain was balanced on the magic 528hPa atmospheric thickness line. On the ‘thin’ side of the line, precipitation is increasingly likely to fall as snow. When an afternoon shower came on heavy the chill air dragged down with it soon allowed craggy half-melted snowflakes to make it all the way to the surface. By the time I had walked 5 minutes from bus stop to station my coat carried a sheet of ice on the front.  After 15 minutes on the train I alighted at Newbury under a blue sky, where the short walk home was almost long enough for my coat to dry again.

At higher latitudes or altitudes – towards the winter world – these interludes happen later into the year. Last June we rode the Rhaetian Railway to the peak of the Bernina Pass. At 2256 metres above sea level it’s as high as the European rail network gets, discounting specialised dead-end mountain railways. Fresh snow lay an inch thick on the ground, smothering spring flowers and adding an air of appropriateness to seeing our first snow finches.

Species evolved to cope with these vagaries of seasonal weather, at least for short periods. One of the chief threats from climate change is that these odd interludes might be more regularly sustained, or more extreme. Add energy to the system and weather signals are amplified, the peaks higher and the troughs lower. In this way we may still see record-breaking cold snaps despite an overall warming trend, something the American politician James Inhofe was clearly ignorant of when he infamously brandished a snowball on the Senate floor during a debate on climate change.

Back in the present, we still may not be past the last frost. To paraphrase Martin Luther King, the arc of the year is long but it bends towards summer. The swifts are back and for now, despite the many changes we are wreaking on the planetary system, the world is still working.

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