A few people asked me to respond to Boris Johnson’s column on Monday about whether the snowy weather is “the start of a mini ice age”. I didn’t, but Prof Joanna Haigh of Imperial College did on our letters page, so I thought it was worth publicising more widely:
I’m delighted that the Mayor maintains his interest in weather and climate, but he should be wary of drawing generalised conclusions from his observations. He suggests that the cold weather in London is due to declining solar activity – but actually the Sun is more active now than it has been since 2009, and about the same as it was in 2004 and 1998.
On longer timescales – decades to century – the Sun may be very slowly declining in activity but this can’t explain year-to-year variations in UK winter weather. The Mayor makes an interesting point about the weather during the Maunder Minimum in sunspots and, although the cooler weather then was largely confined to north-west Europe, that may quite likely have been influenced by the Sun. But at that time solar energetic output was considerably lower than it is today.
What we have is the lovely variability and uncertainty of British weather sitting on top of a long-term global average warming due to greenhouse gas increases. This is not an issue of opinion but one of basic physics. We just don’t need to invoke mysterious effects of solar particles to understand long-term trends in global temperatures.
Prof Joanna Haigh
Professor of Atmospheric Physics
Faculty of Natural Sciences
Imperial College London