Flurry of facts

Geoff Moore doubts the reality of climate change, and cites the snowy winters of 2009 and 2010 in support of his view (Letters, 10 July). The claim that climate change is a myth is a common response to a heavy snowfall event.

In fact, extreme snowfall is actually regarded as a consequence of a warmer world. This may seem paradoxical, but that’s because we assume that cold weather is the only requirement for snow.

Not so. Heavy snow also requires another vital component – a high level of atmospheric moisture.

That moisture builds up in pockets of warm air, since the atmosphere can carry 7 per cent more water vapour every time its temperature rises by 1C.

These pockets of warm air are increasing as a result of climate change, hence the unexpected extreme snowfall events which took place on the US east coast last year.

Becausetheatlanticoceanis getting warmer, the air above the ocean is unusually warm and moist. When that air met cold, dry air from the Arctic, the result was a winter storm, with abundant snowfall.

Both the beginning and end of winter are predicted to be warmer across the Northern Hemisphere in future, so any precipitation will fall as rain, rather than snow.

This will result in shorter snow seasons, but “extreme” snow events could still happen, given the right conditions.

Here in the UK, where winters are never as extreme as they can be in the US, the same principle applies.

Heavy winter snowfalls have indeed become rarer, which is why the winters of 2009 and 2010 were such an exciting event for children. 2010 has also been cited as the warmest year on record, right across the globe. CAROLYN TAYLOR

Wellbank Broughty Ferry, Dundee