CAUSE OF WARMING
In general the planet warms as surface pressure increases in low and mid latitudes.
The chain of causation runs like this: Increased surface pressure is associated with increased geopotential height, extra warmth in the atmospheric column and a consequent reduction in the quotient of moisture held in the very expansive ice crystal form. As cloud cover diminishes more solar radiation reaches the surface of the planet. When energy is absorbed by the ocean it is stored to depth and, by virtue of ocean currents, re-distributed, fortuitously warming those parts that receive little solar energy.
In contrast, when solar energy falls on land it is swiftly, in the main overnight, returned to the atmosphere. The warming of the atmosphere that is occasioned in northern summer, due to the extensive land masses of that hemisphere, results in a global deficit of cloud cover in the middle of the year producing the annual maximum in planetary temperature when the Earth is furthest from the sun and solar irradiance 6% diminished by comparison with January. It should be obvious (how did climate scientists miss this?) that the primary dynamic determining surface temperature is the temperature of the atmosphere in relation to the moisture that it contains.
Please inspect the map below. The planetary winds drive ocean currents that mix cold waters from high latitudes and the ocean deep into the warm waters of the tropics. This is evident on the eastern margins of the oceans and particularly so in the southern hemisphere. The Indian Ocean is the odd man out with a weak cold current on its western margins and a warm, southward travelling, current on its eastern margin. The consequence is a relative backwater that is less affected by the mixing of cold with warm water.
It follows that the circulation of the oceans results in a very different thermal regime in each basin according to the the ocean currents that are primarily driven by the winds. As the winds evolve, so do the currents.
The table below documents the extent of the temperature increase over the last 68 years according to latitude and longitude in the three major ocean basins. For economy I focus on those latitudes that are warm enough to be relatively hospitable to man.
It is obvious that the bulk of the Pacific Ocean has not warmed to the same extent as the Indian and Atlantic Oceans. In terms of basin averages, in January the Indian Ocean has warmed by 0.87°C, The Pacific by 0.42°C and the Atlantic by 0.46°C. In July the Indian has warmed by 0.84°C the Pacific by 0.12°C and the Atlantic by 0.6°C. It is in July that the contrast between the oceans is strongest.It is the Indian Ocean that has warmed to the greatest extent.
THE SURFACE PRESSURE DYNAMIC
If we are to understand the differences in the rate of warming of the Ocean basins we need to comprehend to role of polar cyclones in high latitudes. Enhanced polar cyclone activity in the Antarctic circumpolar trough (red and orange in the map above) has, over the period of record, shifted atmospheric mass into low and mid latitudes from latitudes south of the 50° parallel. In consequence the high latitude west wind drift that is coextensive with the circumpolar trough, that drives cold water into the tropics, has accelerated. The flow is restricted at the Drake Passage between the Pacific and the Atlantic. Accordingly the Pacific Ocean cooled in parts and generally warmed at a much reduced rate when compared to the Indian and Atlantic Oceans.
The Indian Ocean is like the canary in the coalmine, a companion to the miner to warn him of a change in the quality of the air. The evolution of surface temperature in the Indian Ocean offers a glimpse of unfettered reality in terms of the march of surface temperature across the globe as it is forced by change in cloud cover associated with shifts in atmospheric mass and the change in the planetary winds.
The remainder of this chapter explores the shift in atmospheric mass from high southern latitudes and its relationship to surface pressure in the rest of the globe and the Indian Ocean in particular.
The discussion is is not based on the hypothetical constructs of a climate model or the abstruse mysteries of so called ‘planetary forcings’. Rather it is grounded in observation and measurement based on data as presented in the reanalysis work of Kalnay et al accessible here.
The graph below represents the evolution of surface pressure in the Indian Ocean south of the equator.We must to answer the question: Why is it so?
The entire southern hemisphere has not warmed in the month of December in the last 68 years. If surface temperature were being forced by increased back radiation from the atmosphere the southern hemisphere should warm in all months. There is no reason to expect the degree of warming due to a hypothetical increase in back radiation to be different in one month to another. We therefore discard the hypothesis that temperature at the surface is driven by the carbon dioxide content of the atmosphere. We look for other mechanisms to explain the flux in surface temperature. Radiation theory is all very well but in the real world, inoperable. The concept of anthropogenic warming is a distraction from fairyland. We can, to advantage, be more discriminating in what we choose to believe.
SURFACE PRESSURE DYNAMICS
Figure 1 compares the evolution of sea level atmospheric pressure in the Antarctic circumpolar trough to all latitudes south of 50° south. It is plain that the relatively short term fluctuations in surface pressure in the larger entity are greater than in the ‘trough’. In point of fact the trough expands and contracts across the parallels affecting surface pressure in adjacent latitudes and in particular across the Antarctic continent. The agent of change is polar cyclone activity that is energised by differences in atmospheric density between very different parcels of air that meet in the region of the trough in the very broad interface between the stratosphere and the troposphere between about 400 hPa and 50 hPa. It is in this region that the strongest winds are to be found. Polar cyclones are generated aloft. This is the nature of the ‘coupling of the troposphere with the stratosphere’, a concept that is a postulate of conventional climate science but remains a mystery so far as its modes of causation is concerned. If one is wedded to radiation theory it limits the mind.
In figure 2 we compare the evolution of surface pressure south of the 50° south parallel of latitude with surface pressure north of that same parallel. If the total mass of the atmosphere were to be invariable we would expect a strictly reciprocal relationship. As pressure falls on one side of the 50th parallel it should rise on the other. Plainly, the increase, decrease and subsequent increase in surface pressure in concert, between 1948 and 1964, is evidence of a planetary evolution in the quantum of atmospheric mass perhaps associated with enhanced loss in very active solar cycles and incremental gain in quiet cycles. That is a subject for another day.
Plainly, since 1964 it is the reciprocal transfer relationship that dominates. When atmospheric mass is lost south of the 50th parallel it moves north the 50th parallel and vice versa.This process of exchange is referred to as the Antarctic Oscillation.
In figure 3 we compare the evolution of surface pressure in the Indian Ocean south of the equator through to 30°of latitude with that north of the 50th parallel.
Figure 4 presents the same information as in figure 3 but on two axes with independent scales. It’s plain that broadly speaking the Indian Ocean south of the equator gains and loses atmospheric mass in parallel with all points north of the 50th south parallel but there are short term differences. These discrepancies are likely due to complex interactions between the southern and the northern hemispheres where, depending on the time of the year the Arctic Oscillation imposes change in the southern hemisphere or in the reverse, the Antarctic Oscillation imposes change on the northern hemisphere, tending to produce ‘mirror image’ results. Short term variations in these two data series can be in opposite directions.
In figure 5 we compare the evolution of sea surface temperature in the Indian Ocean north of the equator with that south of the equator. The data is a twelve month moving average of monthly means so as to remove the seasonal influence. It is plain that the more extreme variations occur north of the equator. Nevertheless the series are very similar in their evolution with generally coincident peaks.
In figure 6 we compare the evolution of sea level pressure in the Indian Ocean to the south of the equator with the evolution of sea surface temperature in the Indian Ocean north of the equator. Sea surface temperature tends to lag surface pressure by a few months. Plainly the Antarctic Oscillation affects sea surface temperature via coincident heating of the atmospheric column as reflected in increased geopotential height driving a reduction in cloud cover.
Figure 7 looks at the relationship between geopotential height and sea surface temperature. Note that geopotential height is strongly related to sea surface temperature but the relationship is not proportional. It is not the increase in sea surface temperature that drives the increase in geopotential height but warming of the air column due to the increase in the ozone content of the air within descending columns of air. These air columns reflect in their temperature the increased surface pressure, the increased warming at the surface and the increase in the ozone content of the descending air. At 200 hPa the air is warmer in winter than in summer due to enhanced ozone content in winter. The temperature of the air is independent of the temperature of the surface over which it lies.
In figure 8 we focus on monthly data. Shown is the departure of a particular month’s data from the whole of period average for that month.
This graph reveals a climate system that is capable of swinging between a sea surface temperature anomaly of about -0.3°C and +1.2°C in an interval of between one and six years. The amplitude of this variation is almost double the increase in temperature that has occurred in the Indian Ocean over the last 68 years. In this circumstance we should simply move on. There is nothing exceptional about this increase in temperature. There is no need to invoke new modes of causation to explain this phenomenon.
Why has surface pressure and sea surface temperature in the Indian Ocean increased almost continuously since 2011? The answer lies in the forces that determine polar cyclone activity in the Antarctic circumpolar trough. Those circumstances relate to the changing nature of the atmosphere in the area of overlap between the stratosphere and the troposphere in high southern latitudes.
As Gordon Dobson observed back in 1925, surface pressure is a by-product of total column ozone. Low pressure cells have more ozone aloft and exhibit a lower tropopause than high pressure cells.
Ultimately polar cyclone activity and surface temperature together with wind direction and intensity and the extent of mixing in the ocean are a function of the ozone content of the air in high latitudes.