Let’s start with what can be observed. Tahiti lies within the margins of a large zone of high surface pressure that tends to be centered over the Pacific Ocean to the west of Chile.
The extent of upwelling of cold water in tropical latitudes, that account for 36% of the surface of the Earth, conditions global surface temperature. The litmus test for the current state of the atmosphere that is thought to determine the extent of this upwelling, is the difference in atmospheric pressure between Tahiti and Darwin that is encompassed in the Southern Oscillation Index. However, as we see in the diagram above there is a strong inverse relationship between atmospheric pressure in Tahiti and sea surface temperature in the Nino 3.4 region. As pressure increases, temperature falls. The third element shows that pressure swings more widely in January than in September. However, pressure in September exceeds that in January and the peaks in September frequently precede the peaks in January. In Nautical terms Antarctica generates the swell while the Arctic is responsible for the chop.
The distribution of atmospheric mass, determining local surface atmospheric pressure, is driven from the winter hemisphere. January and September are the months of greatest variability on inter-annual, decadal and longer time scales. The handover months, when variability is least, are November and April. Essentially, as pressure falls in the Antarctic trough, the Icelandic or the Aleutian Low, it increases everywhere else. This governs the differential pressure that drives the Trade Winds and the Westerlies and determines whether cold air outflows from the poles or warm air displaces cold air in the Arctic and the Antarctic. As surface pressure increases in the mid and equatorial latitudes, colder water appears at the surface in the tropics. Local sea surface temperature varies inversely with local surface atmospheric pressure as is evident above and below. As pressure rises (downwards on the right hand axis), sea surface temperature falls away. This is the La Nina condition that affects tropical latitudes.
As surface pressure declines in high latitudes it increases strongly in the mid latitudes, 20-40 degrees of latitude encompassing the bulk of the high pressure cells that form over the Ocean all year round expanding to include cold land masses in winter. As surface pressure increases, albedo falls away allowing more solar radiation to reach the surface of the ocean where the energy is absorbed to depth. The temperature of the surface of the sea does not reflect the extent of the energy transfer that is occurring. Over the ocean, because the energy is absorbed to depth, the surface temperature response is restrained. Where a cold current intrudes, the energy transfer can be entirely masked.
When insolation increases over land, the surface temperature increases strongly, and the resulting atmospheric heating drives a further decline in albedo accelerating the increase in surface temperature. This phenomenon is best illustrated by considering the evolution of temperature for the globe over a year.
The different heating rates of land and sea delivers a maximum surface temperature for the globe in July because albedo falls away with the heating of the northern land masses. The Earth is actually further from the sun in July and irradiance is 6% weaker than in January. Weak sun, warm Earth, reason is the decline in albedo.
The direct relationship between pressure and temperature brought about by a change in albedo is illustrated below. In September surface pressure is highest in the mid latitudes and lowest in the Antarctic trough. The location takes in the east of the Pacific Ocean between Sydney and Auckland and about as much ocean again, to the east.
Wintertime polar cyclone activity in high latitudes, that determines surface pressure there, and everywhere else, changes on centennial and longer time scales. If we wish to describe a climate in terms of mean or median conditions, the computation requires at least two hundred years of data. We can see in the figures above that there is both warming and cooling, pressures increasing and decreasing within the space of seventy years. It makes no sense to refer to an anomaly with respect to the mean state for any thirty year period within the cycle of change.
This flux in surface pressure is described as the Annular Modes phenomenon, in enlightened circles, acknowledged as the prime cause of inter-annual and decadal climate variation. This is the elephant in the room of climate change that activists who beat the climate change drum, choose to ignore.
The temperature of equatorial latitudes drives the global temperature statistic because tropical latitudes constitute 36% of the total area. But in terms of understanding the Earths energy budget what happens in the tropics is simply a
mixing phenomenon. Its a smoke and mirrors trick played by the winds and the ocean.
The real action is happening in the mid latitudes. So far as high latitudes are concerned temperature is simply a function of where the wind is coming from, the variability occurring in winter, another smoke and mirrors trick.
It is in the mid latitudes that high pressure cells form, delivering cloud free skies and fine weather, the extent of this phenomenon governing the flux in the Earth’s albedo. The dynamics are well disguised because the Ocean is always in a state of movement, driven by the winds, mixing cold water into the warm.
The proportion of carbon dioxide in the air is of no account. Look at the figure below. The Southern hemisphere is no warmer in January than it was in the 1970s. Conflicting data should trump theory. When you disrespect the data, you are practicing religion, not science. Apparently, religion is as popular as ever, just substituting the god of ecology for former gods now on the nose, due to the behaviour of their priests and disciples. A similar fate awaits the believers in the ‘carbon problem’.
What really matters is the long cycle in the Earths albedo. January is the middle of summer in the Southern Hemisphere where I live. The southern hemisphere is cooler in January at every latitude than the same latitude in July in the Northern Hemisphere. I’m not looking forward to the cooling that is coming. But I guess its all part of the rich texture of climate change. Natural climate change.
Let’s give mankind a break.
That big El Nino of 1996-7, when tropical waters hit the temperature ceiling, occurred in the trough of the most recent cooling cycle of the southern hemisphere as a whole. Notice how quickly temperature can descend.
Due to the configuration of the landmasses, warm tropical water is channeled mostly into the northern hemisphere. The Gulf Stream is illustrative. That means the Northern Hemisphere gets most of the benefit of the warmth that is taken up by the Oceans of the Southern Hemisphere. I’m for warmth. As you can see from the last graph but one, the temperature in September is limiting for plant growth. Without plants, there is no food.
Am I irritated with the climate change worriers, the United Nations Organization, the Australian Government, the carpetbaggers promoting unreliable sources of energy, academia, the ABC, the BBC, Bill Gates, Twiggy Forrest, the poor unfortunate Poms, the EEC, the Greens and the unquestioning press? You bet.
Next post: Perhaps, the evolution of the Trades and the Westerlies.