The long view of change in surface pressure (due to a redistribution of atmospheric mass) can be derived only from the reanalysis record located here and reproduced below. We look at change by the decade.
In the Arctic surface pressure peaks in March, April and May with a secondary peak in October-November due to ozone heating in the southern hemisphere. The fact that the Arctic peak occurs in March rather than in December-January relates to the presence of the Eurasian land mass where very cold conditions attract atmospheric mass in December and January. By March, the land mass warms slightly allowing a shift of atmospheric mass to the now relatively colder Arctic. However, surface pressure is most variable in January and February and this is when northern hemisphere surface temperature is most variable. I explore the nature of surface temperature variability here.
Above we see that, at the heart of the Antarctic continent, surface pressure peaks in mid winter. Winter surface pressure has declined by about 10 hPa over the period of record reflecting a an increase in the ozone content of the air that drives enhanced polar cyclone activity. The consequence is a gradual shift of atmospheric mass to other parts of the globe and in particular to the mid latitudes of the southern hemisphere where surface pressure has risen in direct response.
The westerly winds have strengthened over time as surface pressure falls in high latitudes and rises in mid latitudes.
Due to the increase in the strength of the westerly winds there has been a shift to higher latitudes of the band of cloud that is associated with frontal activity, consequent cooling in high southern latitudes in spring and early summer, an increase in Antarctic ice mass in winter and spring and change in rainfall patterns in the mid latitudes. West coast Mediterranean type climates that rely on winter rainfall have become more arid. However the increase in the carbon dioxide content of the atmosphere enables plants to thrive on less water and vegetative mass has actually increased despite the decline in rainfall as reported here and here. In some parts of Australia rainfall has increased.
On the margins of the Antarctic continent where the atmosphere is relatively rich in ozone, not so much in relation to the very high levels of ozone in the northern hemisphere but certainly by comparison with the air over the Antarctic continent, there is a marked trough in surface pressure in October when ozone partial pressure is at its seasonal maximum.
At 60-70° south surface pressure has declined by 10 hPa over the period of record. The secondary peak in January is due to ozone heating in the northern hemisphere.
As the atmosphere moves away from high latitudes there is an increase in atmospheric pressure in mid and low latitudes. This is accompanied by an increase in the temperature of tropical waters between 20° north and 20°south latitudes as seen in the diagram below. In assessing this relationship we should not forget that volcanic eruptions can throw dust into the stratosphere increasing the Earth’s albedo. Secondly, the oceans absorb energy and give it up slowly so that surface pressure leads as temperature increases and leads again in the decline phase.
The rate of transfer of energy by the atmosphere from low to high latitudes increases as the pressure differential between the equator and the poles increases.
The system gains energy as surface pressure increases via a reduction in albedo in the mid latitudes as described here.
The decline in surface temperature in the tropics after 1998, as surface pressure falls away suggests that the system does in fact gain and lose energy according to change in albedo that is causally related to the surface pressure dynamic.
In high latitudes the wide swing in the temperature of the air between summer and winter reflects the influence of the vortex of mesospheric air with substantially increased inflows in Antarctica, much more so than in the Arctic. This is the dominant influence on the ozone content and the temperature of the Antarctic stratosphere and indeed the ozone content of the southern stratosphere.
CHANGE IN THE TEMPERATURE OF THE ANTARCTIC STRATOSPHERE AS OZONE HAS PROLIFERATED
The change in the temperature of the stratosphere over Antarctica since 1948 reflects a change in the partial pressure of ozone in the air necessarily involving a change in the distribution of ozone at various pressure levels. Since ozone heats the air, it reduces its density and local contrasts in density result in ascent of the low density air, albeit mixed with air from the troposphere and from the mesosphere. The change in the mobility of the air changes the vertical distribution of ozone in the stratosphere. It is natural that the temperature of the air increases to a greater extent at the more elevated pressure levels because this is where ozone accumulates as a result of the process of uplift.
The explanation for ozone volatility given here is very different to the Brewer Dobson narrative that sees ozone being transported from the tropics to accumulate in high latitudes. In fact the circulation is in the reverse direction with whole of atmosphere ascent in high latitudes and descent in the mid latitudes.
The protective mechanism that allows the increase in ozone partial pressure in high latitudes in winter is the reduced incidence of destructive short wave radiation due to the longer atmospheric path as the sun sinks towards the horizon, disappearing entirely during the polar night. A secondary advantage that accrues in the winter hemisphere resides in the reduced uplift of NOx and water vapour from the lower atmosphere outside tropical latitudes.
The ozone hole in spring is a product of convection that brings destructive NOx into the lower stratosphere over the Antarctic continent where it is trapped by the still persisting descent of mesospheric air until November. The hole is not new. It was first encountered in 1956 when a Dobson Spectrometer was taken to the British base at Halley Bay in Antarctica but it was smaller at that time. Its enhancement is due to enhanced convection. Bear in mind the negative correlation between ozone partial pressure outside the ‘hole’ and inside the ‘hole’ indicating that the hole is a natural feature of the circulation rather than a product of ‘new chemistry’ that is a threat to the presence of ozone throughout the stratosphere. This dynamic and the very different situation in the Arctic will be covered with rigour in later chapters.
Below we see that the temperature of the air at 10 hPa vacillates most in October, the month when the ozone hole manifests in the lower stratosphere. This is also the month when surface pressure descends to its annual minimum at 60-70° south latitude due to the contrast in ozone partial pressure on either side of the chain of polar cyclones that is generated as a result of the density differential. The increase in the temperature of the polar cap in October represents ozone enhancement over time. With enhanced partial pressure of ozone aloft there will be a commensurate tendency for descent in the mid latitudes in October/November that is very much part of the ENSO dynamic. The trough in surface pressure at 60-70° south in October adds atmospheric mass to the mid latitudes expanding the area occupied by relatively cloud free high pressure cells. Together these influences add an El Nino bias to the climate system.
This increase in atmospheric ozone in springtime and lack of depletion at any other time of the year flies in the face of the many ‘ozone at risk’ narratives that have been foisted on an unsuspecting and compliant public by attention seeking ‘scientists’ over the years.
The diagram below records the degree of variability in 10 hPa temperature by latitude in the southern hemisphere over the period since 1948. The data represents the difference between the coolest and warmest month within the period.It is plain that extreme variability is associated with the months when the Antarctic ozone hole develops in the period from June through to December.
CHANGED TEMPERATURE PROFILE IN THE MID LATITUDES OF THE SOUTHERN HEMISPHERE INVOLVING A WARMER UPPER TROPOSPHERE
In the mid latitudes the strongest winds manifest between 300 hPa and 50 hPa where cyclones and anticyclones are characterised by marked differences in their ozone content. The increase in the temperature of the air in the mid latitudes at 200 hPa in 1976-78 is associated with increased surface pressure. The increase in the temperature at 200 hPa relates to the increase in the temperature of the stratosphere generally.
SOURCES OF VARIABILITY IN THE PARTIAL PRESSURE OF OZONE IN THE STRATOSPHERE
1. The rate of influx of ozone deficient mesospheric air over the southern pole is surface pressure dependent and is the primary factor affecting the ozone status of the entire stratosphere. Stronger descent of mesospheric air is primarily a winter phenomenon. Even so, when surface pressure falls away at any time of the year the mesospheric tongue retracts and the stratosphere is seen to warm as ozone rich air takes its place. The most energetic changes are associated with the build up in ozone partial pressure from June through to October. Enhanced variability in spring is due to the relationship between ozone content of the atmospheric column and surface pressure. This relationship was well appreciated prior to the 1950’s. It has been ignored since that time. Ozone acts as a multiplier and an accelerator for surface pressure change originating from external influences.
2. The degree of uplift of NOx from the troposphere is plainly a potent influence on the ozone content of the stratosphere, especially in low latitudes but also over Antarctica in spring.
3.The manner of the accumulation of ozone in the northern hemisphere, and land/sea geography create a very different dynamic to that in the southern hemisphere. The singularly ozone rich air from the Pacific sector rises in the atmospheric column like a nuclear dust cloud, warming the stratosphere above 30 hPa. Changing pressure dynamics shift the high pressure cells that tend to locate over east Asia in early winter to the Arctic in spring, or alternately to the Scandinavian or the Hudson’s Bay/Greenland sector. The mesospheric vortex brings cold air to the surface where it streams southwards, particularly in the negative phase of the Arctic Oscillation associated with high surface pressure over the Arctic. In other words, the vortex in the northern hemisphere, unlike the southern hemisphere, has no fixed address. The Jet Stream wanders accordingly.
3. The composition of mesospheric air that is introduced into the winter stratosphere would be expected to vary with solar activity and in particular the partial pressure of the oxygen hungry products of the disassociation of nitrogen.
4. The density of mesospheric air and the upper atmosphere in general varies with the intensity of ionising short wave solar radiation probably affecting the effective rate of interaction between the mesosphere and the stratosphere.
5. The electromagnetic properties of the solar wind are known to impact the distribution of the atmosphere that has its own electric and magnetic field. Ozone is diatomic and will react to electromagnetic stimuli. The atmosphere over the pole is particularly susceptible to movement when the stratosphere is warm because cosmic rays (charged particles) penetrate to greater depth at that time. At times when the aurora light up the heavens under the pressure of the solar wind, the atmosphere is likely to be very responsive to electromagnetic stimuli.
6. Ionisation due to cosmic rays may be involved in the synthesis of ozone at the poles.
It is apparent that all these factors place conditions on the extent to which the sun drives shifts in atmospheric mass that are comprehensively amplified by the Earth system itself. The chief deterministic condition as to the scope of influence of external influences and the manner of their expression is the susceptibility of the winter hemisphere rather than the summer hemisphere due to ozone enhancement in winter.
A SUMMARY OF THE ORIGINS OF NATURAL CLIMATE CHANGE
Ozone proliferates in the winter hemisphere, probably due to the manner in which the wave lengths that are responsible for the photolysis of ozone are attenuated as the angle of incidence of the sun moves away from the vertical, especially in winter.
The inflow of mesospheric air that depletes ozone varies with surface pressure and is strongest in winter. In winter, stronger contrast in air density drives the generation of polar cyclones and enhances the jet streams.
Polar cyclone activity drives variations in surface atmospheric pressure shifting mass to and from high latitudes towards the mid latitudes and across the hemispheres. This changes the planetary winds and affects cloud cover in zones of high surface pressure via the well observed relationship between surface temperature and geopotential height at 500 hPa.
Hypothetically the solar wind (geomagnetic activity) acts as a trigger for change and establishes an equilibrium about which the climate system oscillates. The climate system itself provides a strong amplifier to change in surface pressure initiated by an external source because any reduction in surface pressure in high latitudes promotes further loss of surface pressure per agency of ozone.
The signature of polar processes affecting the ozone content of the air is written in the surface temperature record. Temperature changes according to the origin of the air in a manner that is well documented as the Arctic and the North Atlantic Oscillations of the northern hemisphere. The El Nino Southern Oscillation is a surface pressure driven phenomenon waxing and waning with the strength of the Trade Winds. It reflects change in the rate of mixing of very cold waters into the warm waters of the tropical Pacific and the rate at which warm waters from the tropics are driven towards higher latitudes. In other words, the temperature of the surface waters is by and large a result of change in the nature of the water that is present, much like the change that occurs when a person dons new garments. Things seem to change at the surface but underneath there is no change at all. But in the case of the Earth system there is actually a change in cloud cover outside the ENSO monitoring regions as surface pressure falls in high latitudes. It is predominantly in the mid latitudes over the oceans where high pressure cells naturally form that cloud cover is affected. Cloud cover falls away as atmospheric mass shifts to the mid latitudes strengthening the pressure differentials that drive the planetary winds.
The signature of natural climate change, the only game in town, is written into the surface temperature record. It is tied to shifts in atmospheric mass.