AS an ex-geography teacher, people keep asking me about global warming, saying: “Why is it colder then?”

The recent cold weather is part of the global warming scenario. Briefly, the Gulf Stream is a broad current of warm water coming from the Gulf of Mexico.

It travels through the Straits of Florida northwards, parallel to the US east coast. It merges with the North Atlantic Drift roughly opposite Washington DC.

It is moved by the direction of the prevailing winds, ie a south-west air stream coming from warmer climes, passing over the surface water of the Atlantic drift, then bringing warmth inland to influence the West European climate, especially the UK.

Now, when pollution stops the sun’s heat escaping over the northern polar regions, including Greenland (similar to cloud overnight keeping heat in), the melting ice water moves south, making sea surface temperatures lower, so the colder air stream over the water moves with it, causing cooler air over north-west Europe.

Thomas Driver, Ascot Way, York.