The Jet Stream

The Jet Stream

The latest news on Global Warming seems to be the Jet Stream. Around four years or so ago we were told that the UK was in the process of becoming so dry that there would be permanent hosepipe bans and that lakes and reservoirs would never be replenished.We were advised to expect a permanent water shortage. But the Jet Stream wasn’t thought to be involved. Then suddenly the weather changed.. Until recently we didn’t hear a great deal about the Jet Stream in the context of Global Warming, but now it’s in the news all the time and some experts talk as if they knew all along that the Jet Stream was involved. The Jet Stream drives the weather systems worldwide, and it’s the Jet Stream that’s historically responsible for the British Isles’ special climate. The UK and Ireland have in recent millennia been much warmer that they should be according to our latitude. Similar latitudes to the East and West of the British Isles, like Southern Scandinavia, and parts of Canada seem almost arctic by comparison. And it s the Jet Stream, that makes the weather in the British Isles so variable and temperate.

jet streamThe Jet Stream

The Jet Stream is a narrow band of high wind speeds but which can extend many thousands of miles long. Jet Streams are found around six miles up on the atmosphere and owe their existence to big temperature differences occurring between conflicting air masses. Ribbons of high velocity winds known as Jet Streams occur in different parts of the globe and meteorologists study their positions and forecast their effect on the weather. Jet Streams also affect the progress of aircraft and pilots have to take account and Jet Stream speeds of up to 200 miles an hour when flying aircraft. The fuel consumption of aircraft and he flight times are significantly affected by Jet Stream direction, position and speeds. The Climate Change effect of the Jet Stream which arrives from North America to the UK is thought by some to be a factor in the extreme weather conditions which affected the UK at the end of 2013 and the beginning of 2014 although the UK’s changeable climate continues to confound experts with open minds. Some say that there is no definitive answer as to whether Climate Change and its interaction with the Jet Stream is responsible for the variations and changes in direction in the Jet Stream which is now mooted to have been the cause of the storms. There is no evidence to counter the basic premise that a warmer planet will lead to more intense daily and hourly weather events. More than 130 severe flood warnings were issued from December 2013 to February 2014 compared with nine for the whole of 2012. But sceptics persist in questioning whether it’s man made global warming that’s affecting the Jet Stream. After all they point out that during dry periods Global Warming is also said to be the cause and no warnings of wetter weather to come were forthcoming during droughts not so long ago. The public were warned that Global Warming meant dryer weather and droughts and the  effect on the Jet Stream was rarely referred to.

Global Warming and the Jet Stream

But those who warn that the information the experts keep delivering is wrong are not usually what are known as Global Warming Deniers. There is in fact a surprising level of agreement amongst all that the world has been getting warmer. The debate actually lies in whether this Global Warming is man made and the speed at which it is likely to continue. There is also no real agreement on what effect warming is having on the weather, .or on the Jet Stream. There is no doubt that there has been a variation on the direction and speed of the Jet Stream very recently. But such fluctuations happen from time to time. One of the difficulties with predicting the weather let alone the Jet Stream is the fact that proper weather records go back only a few decades. All sorts of extreme weather events have occurred in the past often more serious than recent ones, and it may all be part of a much longer and more erratic weather cycle. Something may well be happening to the climate but is difficult to tell in what direction its going in and what the cause of it is. Even the most committed experts do not see recent instances of odd single variations in the Jet Stream as conclusive evidence of anything in particular. The public are always sceptical about experts who cl.aim to have all the answers. Expert opinion about almost everything is wrong as often as it’s right and when received opinion changes different experts appear to replace discredited ones. On occasions the same experts just carry on as before but now claim conditions, the opposite of what they foresaw, as being evidence that they were right all along. Hence some of the recent comments about the Jet Stream. But the world’s weather system is a phenomenally complicated and unpredictable process

Slight Changes in Jet Stream Direction

Great Britain’s weather patter is changeable because of the Jet Stream. Owing to it’s fast moving air the Jet Stream causes the weather to change more quickly than it otherwise would. Successions of ever changing weather systems in the Atlantic arrive in quick succession and so the weather changes fast. But this system tends to mitigate against serious extremes in temperature and weather. So the Jet Stream brings heavy gusts of wind and rain from the West but the weather doesn’t last as long as it might otherwise do without the Jet Stream. It’s the same with periods of dry weather. Researchers however have noticed towards the end of 2013 that the Jet Stream has started taking a longer more meandering path. The result was that when weather arrived it lasted for much longer than it otherwise would have done. Hence the prolonged bouts of rain and heavy winds which are now attributed to the Jet Stream. It appears that temperatures in the Arctic have been rising faster than they were further in temperate latitudes, and that fact has reduced the temperature differential between the two regions. So the temperature difference which drives the Jet Stream is  reduced. If the differential s large the Jet Stream speeds up like a river flowing down a steep incline. But if the differential is lower as it now appears to be wind speeds slow down and the Jet Stream’s effect on the weather dissipates. The Jet Stream loses its capacity to drive through obstacles such as areas of high pressure and takes the form of a river flowing along a near flat surface. It is clear that if this situation persists then there will be changes in the weather patterns. Without a fast moving Jet Stream the UK will be in for longer periods of the same weather before the weather changes to something else. This will be particularly serious for flooding because prolonged periods of heavy rain even if total rainfall does not increase in the long term will me more than drainage systems can cope with. Prolonged periods of drought caused by a slow Jet Stream will have a different unwelcome effects

Reductions in the speed of the Jet Stream also results in colder weather moving South and warmer weather moving North. In recent times it has not just been the UK which has been affected by colder weather. Scandinavia has become warmer. But this is the type of effect that sceptics change sceptics are concerned about. This particular effect was not necessarily the outcome that Global Warming experts forecast even recently. Received opinion was that all would get warmer. So careful consideration has to be given to what the effect of warmer Scandinavia and a cooler (say) Spain will actually have on human well being. Some argue that expected Global Warming effect on the UK has also be changed completely. The received expert opinion was until recently that Global Warming meant drought. A sensible view may be that it is too soon to tell. Other effects of the Jet Stream may also be arising from the loss of Sea Ice cover in the Arctic which is allowing heat from the sea to rise into the upper atmosphere.

Flooding Somerset levelsJet Stream and exceptional Weather

The UK had suffered its most exceptional period of rainfall for 248 years. But what exactly does that mean. It means that 248 years ago the weather was wetter and that was when the climate was cooler and before hardly any of the carbon dioxide  or dense pollution associated with the Industrial Revolution had been emitted. And in Global terms is 248 years long enough to consider the weather patterns let alone what effect the Jet Stream, has been having.. To be able to attribute these changes to anthropogenic Global Warming (Global Warming caused by Humans) will require much more sophisticated computer climate models sufficient in their resolution to encompass storms and the rainfall that comes with them. They will have to be more complicated still to deal with the Jet Stream and how it specifically affects the weather at any given time. At the moment these models are not available but they soon will be in a form that might have some benefit. One of the latest contributions to the debate seems to have come from David Cameron who says he ‘suspects’ that Global Warming might be the cause. of recent events. He did however clarify his remarks later to say that we should all have an open mind and no one should be distracted by any suspicions that Global Warming is ‘mumbo jumbo’. (His words).

If the KCS Advice Site finds out anything new about the Jet Stream or anything else associated with matter, we will ‘mumbo jumbo’ or not be the first to report it. In the meantime if anyone has any comments about Global Warming, Climate Change or the Jet Stream we would be pleased to receive and report them