Some Science on Arctic Warming
by William Kininmonth

The Polar Regions are regions of net radiation loss to space. The temperatures of the Polar Regions are regulated not by local radiation balance but by the transport of energy from the tropics by the atmosphere and ocean circulations. If it were only local radiation, then the poles would be much colder than they are!

Current global energy generation is about 13 terawatts and is expected to rise to 30 terawatts by the middle of the century. This is to be compared to the current average transport of energy from the tropics to the poles in each hemisphere of about 6,000 terawatts by the atmosphere and the oceans. The transport varies with season and from year to year (ENSO, etc). A one-percent increase in the annual average transport in the Northern Hemisphere, if sustained, would transport additional energy sufficient to melt the Arctic Ocean sea ice in about 7 years (and computer models cannot simulate the poleward transport of energy with such accuracy!). Of course, as the Arctic sea ice melts, there is an increase in the radiation loss to space that is proportional to the fourth power of temperature. This latter is not generally spoken about when we are being terrified by the impact of reduction in albedo and increase in absorption of solar radiation (for how long is the sun shining compared to the increased emission to space?)

The oceans, particularly, are fluids in motion and each basin gyre and the overall overturning have natural periods of oscillation. The motions are largely wind-driven and the basins are connected and interacting. My limited fluid-dynamics training suggests to me that the natural periods of the oceans, the flywheels of the climate system, will cause the poleward transport of energy to vary on timescales from decades to centuries. What we currently observe is a period of an enhanced poleward transport of energy since the 'climate shift' of the middle 1970s.

We should not be too concerned about recent rises in temperatures over the Arctic. There will not be a runaway warming because the region is reliant upon transport of energy from the tropics to maintain its 'warmth'.

And over the tropics? This is a region of excess solar radiation where the excess is absorbed in the land and ocean surface (the troposphere is continually losing energy by radiation processes and cooling). The surface temperature is regulated by the rate at which the excess energy from solar insolation is exchanged with the overlying atmosphere, primarily by way of evaporation and conduction. Over forest areas and the oceans (most of the area) the surface temperature is kept relatively cool by evaporation. As atmospheric carbon-dioxide concentration increases and less energy is lost from the surface by radiation emission, the difference will largely be taken up by increased evaporation with little increase in temperature (evaporation rate increases nearly exponentially with temperature).

The shape of the Earth and basic laws of physics suggest to me that runaway global warming is a myth. However global temperatures, particularly over the poles, can vary as a consequence of the changing rate of transport of energy from the tropics to the poles. We do not know the magnitude of the envelope of variability nor its impact on the extent of polar ice-mass variation. It is natural, and we need to prepare. However as long as the research community is fixated on greenhouse gases and are tuning their models accordingly, we will not be prepared for the potential speed and magnitude of natural change.
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William Kininmonth has a career in meteorological science and policy, spanning more than 40 years. For more than a decade (1986-1998) he headed Australia's National Climate Centre with responsibilities for monitoring Australia's changing climate and advising the Australian government on the extent and severity of climate extremes, including the recurring drought episodes of the 1990s.