The earth is surrounded by an atmosphere which not only provides us with the oxygen we need to breathe but enables the earth not to become, too warm in the day or too cold at night.  This atmosphere is not uniform either in height or in latitude.  The first layer is the troposphere which is where the air circulates. To understand the implications of climate change means understanding the circulation of air around the globe. Because of its closer proximity, the sun radiates more heat at the equator than at the poles. As air is heated, it becomes lighter and it rises while air that is cooled is heavier and sinks. The zone of cold air is high pressure whereas the zone of hot air is low pressure. A convection cell is thus established. On the earth surface the cold air in the poles pushes the air towards the equator; within the upper level of the troposphere the warm air is drawn into the vacuum created by the circulation of the cold air. However, that model conceived by the British scientist Hadley in 1735 was too primitive. As the earth rotates the north to south air circulation would have been blowing from east to west (Coriolis Effect). However the navigators had established that, whereas the winds would blow from east to west in the northern and the equatorial regions, the winds in the temperate regions blew in the opposite direction. More than a century later, the American scientist Ferel stated that there should be an intermediate cell, to account for the variation of the winds. The meteorological world was now settled with three different circulation cells that were divided for practical purposes in thirty degrees latitude. These can be seen in the drawing below.

As can be seen the Cell at the equator has a much higher ceiling than the polar cell as it has to cope with much larger volumes of air. The airmass in the tropical zone is warmer than that in the temperate zone which is itself warmer than in the polar zone. These temperature gradients are translated in pressure gradients and wher the zones meet there are violent zones of winds that circulate around the globe.

these are are known as the jetstreams. Another interesting fact is that the presence of high ridges (the Rocky Mountains in the US for example or the Himalayas in Asia) will send a jet stream higher and in the process deviate it from it straight course.

As can be seen on drawing, instead of circumvallating the earth in a straight line, the Jetstream oscillates like a wave around the globe.

Whereas polar jets flow at an altitude of  9–12 km above sea level, the weaker subtropical jets flow at 10–16 km. Because of the speed of rotation of the earth surface at the tropics the Tropical jet speeds are slightly higher (80-150 knots), whereas the polar jets run at a speed of 80 to 130 knots. At times these jets can interact and create special weather patterns but the resulting patterns have yet to be clearly identified.

During summer months the path of the Jet streams moves to more northern latitude and in winter it swings back southwards. The areas below the wave crests tend to be calm and warmer, whereas the areas above the troughs of the waves are stimuli for storms. The varying speed of the jet stream and the position of throughs and crests are very difficult to predict and meteorologists before the advent of satellites were prone to gross errors. Even today, they can be fooled in spite of much greater information. However, what is noticeable is not the warming itself, which is only measured in hundredths of degrees but the sudden violent changes in temperatures. These can be observed in temperate zones, within a given season, when temperatures shift in a range of 10 to 20 degrees centigrade in a matter of days.  This is due to the amplification of the meanders of the jet stream. This has the effect of slowing the circumvallating speed of the jet stream around the earth. At times the system stalls and the crest or the trough of the jet stream is blocked in one area. The areas below the wave crests tend to be calm and warmer, whereas the areas above the troughs of the waves are stimuli for storms. When the system blocks in one area for too long, it means droughts in areas immediately below the crest and flooding due to excessive precipitations above the troughs. This is what is known as extreme weather.

Another disturbing factor is the rapid melting of the Arctic polar cap and, even more disturbing for inhabitants of low land coastal areas, the melting of the ice crust of Greenland. It would appear that, even if all important industrial nations adhere to the terms of the 2015 Paris agreement and by some miracle manage to limit the average rise of the temperature to only one additional degree, the temperature in the arctic is likely to rise by 5-9 degrees above the 1986-2005 average.

Already in the past 30 years, the area of sea ice in the arctic has declined by 50% and its mas by 75%. As can be seen on those maps there is now, in the summer months, an unrestricted sea passage through the Northern Passage. Whereas, until recently, scientists expected a summer ice free arctic by 2070, the date has been advanced to 2040. The global warming which precipitated the melting of the arctic, and for that matter of the Antarctic ice caps, has had an unexpected effect particularly perceptible in the arctic. As the polar cap area reduces, the reflective action of the cap is diminishing. The ice does not absorb all the heat from the sun but sends it back to the atmosphere, whereas the water in the vicinity of the ice absorbs all the heat. As the water becomes warmer, it accelerates the melting of the ice. The reduced ice cover means less heat reflection outside the atmosphere and increased heat from the water, thus accelerating the melting process. Another pernicious effect is the melting of the permafrost, which will release vast quantities of methane gas, one of the six main greenhouse gases, and will in turn further compound the greenhouse effect caused by the excess of CO2 in the atmosphere.

This in effect means that the most northern area near the North Pole is warming fast and that the difference in temperature of the air masses, between the most northern regions and the temperate regions are decreasing. This should decrease the friction at the confine of the two zones and therefore the jet stream should slow down. Scientists are linking the amplification of the meanders of the jet stream to the melting of the ice cap and of the ice crust of Greenland. This is disputed by other scientists who assert the movements of the jet stream to changes in pressures.

It would seem that Panama, being in the tropical zone, should be immune from such variations and yet the climate here is changing, the differences between the dry and wet seasons are less distinct. The hurricane season starts earlier but fortunately Panama is too far south to have a major hurricane although it may be subject to secondary effects. The more disturbing phenomenon is El Nino, which creates a shortage of rain when it occurs, and la Nina which create excess rain but over too short a period for the Lake Gatun to benefit.

The El Nino effect is a blocking of the cold Humboldt Current along the east coast of South America while, at the same the trade winds keeping the warm water masses in the western Pacific near Australia and Indonesia, die down permitting those hot water masses to flow towards South America and Panama.

But these are the mechanisms and science is not advanced enough to demonstrate what the triggering effect of these phenomena is. Some scientists postulate that sub-surface temperature anomalies, first develop along the off equatorial central North Pacific. They may induce further anomalies in the equatorial waters and then propagate eastward south of the equator triggering the mechanisms previously described. Others attribute the triggering to the south flowing Bering Strait cold current being cut off by extreme cold periods reducing cold air flow to the south. All these events may be caused by variations of the jet stream. What is worrying is that the frequency of El Nino in the 0.5 degree range effects is increasing. The large el nine effects are still occurring with a frequency of 15 to 20 years but their intensity is increasing. If the triggering effect is the Jetstream it could prove very damaging for the Canal operations unless additional reservoirs are created.

  Domenico Koumoundouros  


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