With the risk of fuelling another five year debate on climate change I would like to comment on Eric Alexander’s unscientific belief that man-made warming drives the jet stream.

There are four jet streams, two in the southern hemisphere and two in the northern hemisphere all of which circulate around the planet. I assume that Eric is referring to the north polar jet stream.

Contrary to popular belief the jet stream does not cause weather, but is the result of weather. It is caused by the collision of warm moist air from the equatorial regions colliding with cold drier air from the Polar Regions. The resulting air flow caused by the release of heat energy in the moist air is then bent by the Coriolis forces (due to the earth’s rotation) to flow in an easterly direction around the planet.

The polar jet stream exists in the upper layer of the troposphere at around 35,000 to 40,000 ft. It was the Americans who confirmed its existence with the high altitude flying of Second World War aircraft like the B29 Super Fortress. Aircraft flying from the US to Europe covered the ground much faster than aircraft flying west across the Pacific. The jet stream can blow as strongly as 200 miles per hour. Today commercial aircraft hitch a ride on the jet stream coming east thus saving fuel and reducing the journey time flying from North America to Europe.

Low pressure systems form on the northern flank of the polar jet stream. So if the jet stream sinks south, which it has been doing frequently in the last six years and the UK is on the cold side of the jet stream we get wet, cold, windy weather in summer and cold snowy weather in winter.

Since 2003 the jet stream has become sluggish and instead of blowing in an undulating line across the Atlantic to the north of the UK it has wandered about sometimes entering Western Europe as far south as Southern Spain. Since 2007 the UK has experienced five consecutive poor summers and four winters with severe cold spells. This phenomenon occurred in the 1950s and 60s, a period identified with cooler wet summers and colder winters, notably 1947 and1963. Records also indicate that a similar performance of the jet stream prevailed during the Little Ice Age of the late 16th Century.

There are many unproven theories on what affects the position and strength of jet streams. Clearly, the warmists will seek the opportunity to blame it all on manmade global warming without any scientific proof whatsoever. What we do know is that sun spot activity is in rapid decline and the Little Ice Age coincided with the Maunder minimum. A period when sun spot activity reduced to zero.

Anthony Weeden, Bockmer End, Nr Marlow