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Sunday 7 February 2010


The north eastern part of the USA has experienced heavy snowfalls for the second time this winter, and another colder spell of weather is forecast for the UK – particularly the north and east. This will no doubt be picked up by the climate change denial lobby as evidence against global warming, but some consideration of what are transient weather patterns should prove instructive.

The snowfall in the USA and the looming cold snap in the UK are connected: both are due to an intensifying area of high pressure extending south and east from Greenland, which was also in place during the previous bouts of severe weather experienced by the two countries. This condition can be observed by checking out the synoptic chart made available by the Met Office.

The high pressure area effectively puts a block in the way of weather systems which usually move from west to east across the Atlantic, changing the wind direction across the UK from the milder south-westerly to a north-easterly, the latter being very cold in winter, as it brings air off the cold continental land mass. Moreover, those weather systems coming out of North America get stuck, so a snowfall that may have been a brief event becomes persistent, with the effect as seen.

Why is this happening? Well, one reason is that the Atlantic Jet Stream, which is accepted as a strong influence on the movement of weather systems, is right now tracking much further south than usual. Thus the weather systems are also tracking further south. In other words, this is a natural phenomenon.

Climate change science is not debunked by transient weather patterns.

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