Tag Archives: blackcap.Sylvia atricapilla

Less predictable ramifications of global warming

This all seems a mite anachronistic now, but at the end of March when things appeared to be warming up and becoming rather more in keeping with the calendar this happened:

Snow capped post box at the front of my garden on March 23rd!

I often here folk grumbling that global warming often doesn’t feel that way, and, of course, the reason for that is that the average global temperatures are rising which can result in higher highs, but also lower lows, as more heat energy is sequestered in the atmosphere and the oceans causing altered patterns and much greater unpredictability. ‘Climate change‘ therefore seems the more accurate description.

From the point of view of the UK, our weather system is complicated because we are at the edge competing systems, from the south and west Atlantic, east from Europe and north from the Arctic. A major determinant of which of these systems dominates is the jet stream. This is a ribbon of fast flowing air, around 100mph (160kph), formed at the barrier between cold arctic air and warmer mid-latitude air, around 6-6.5miles (11000m) up, and moving from west to east. It’s position can wobble northwards and southwards and in the winter it tends to be south of the UK so we are dominated by cold polar air and in the summer it migrates further north so warmer conditions can predominate. But due to climatic variability in recent years the position of the jest stream has not conformed to tradition and has remained much further south so our summer weather has been much colder and wetter in the last few years.

Hence snow at the end of march…

A male great tit, Parus major, wondering what’s going on!

The unseasonal weather over the last few years has caused real problems for wildlife. Numbers of bees and butterflies have been down and hibernating creatures such as hedgehogs can struggle to find food when they eventually arise from the winter slumber.

A male blackcap, Sylvia atricapilla, nibbling on frozen fatballs

The blackcap pair which arrived in my garden in January made their last appearance during the March snow and then disappeared. I think they must have been overwintering here in the UK and when the really cold weather finally ended they headed back on their long flight to central Europe in time for the breeding season.

We’re now at the end of June and the jet stream has moved north allowing high pressure systems to move in from the Atlantic to the west and bring some warm weather. Long may it last!

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