Most people are under the impression global warming has risen by about 0.8 degrees C since the dawn of the industrial age. Unfortunately, mean temperatures have risen much further when account is taken of the short-term masking effect of aerosols emitted from coal and oil, mainly sulphur dioxide and its oxidized products. Moreover, since 2005 (the last year on which the IPCC-2007 report is based) Arctic Sea ice melt has resulted in lowering of the Earth reflectance of solar radiation back to space. As sea ice melts, exposure of open water to solar radiation results in the absorption of thermal infrared radiation and thereby further warming of the oceans.
Thus, according to the IPCC AR4-2007 report (figure SPM.2), the total anthropogenic greenhouse effect since 1750 AD, which is equivalent to about +2.3 degrees C, is masked by a compensating aerosol albedo effect equivalent to about -1.1 degrees C. However, given the short-lived residence time of sulphur aerosols in the atmosphere, this masking effect dissipates within periods up to a few years.
Currently continuing emission of SO2 maintains the aerosol albedo effect, preventing further sharp temperature rises. But in a situation akin to methadone addiction, proposed reduction of sulphur emissions would lift this barrier, enhancing global warming.
A dissipation of aerosols and the melting of polar ice would raise polar temperature anomalies to levels exceeding even the current 4 to 5 degrees C warming in parts of the Arctic circle, Siberia and west Antarctica. Such high degrees of warming result from ice melt/water interaction feedback processes.
The climate change trend is highly irregular, representing an increase in climate variability with global warming, reflected by variations in the El Nino — La Nina Southern Oscillation cycle (ENSO). Sharp ENSO anomalies include the 1998 El-Nino peak (near +0.55C) and the 2007 La Nina trough (near -0.7C). Mean global temperature continued to rise during 1999-2005 by about 0.2 to 0.3C.
- Reduction in the Arctic Sea multi-year ice cover from about 4.2 to 2.5 million square km during 2000-2009;
- Increase in Greenland September ice melt area from 350,000 to 550,000 square km during 1997-2007;
- Warming of the entire Antarctic continent by 0.6C and of west Antarctic by 0.85C during 1957-2006, reflected by collapse of west Antarctic ice shelves.
Variations in temperature and sea ice cover around Antarctica are effected by several factors, including (1) the shrinking polar wind vortex, which results in higher wind speed chill factors, (2) decrease in tropospheric ozone concentrations, ozone being a greenhouse gas this results in cooling, and (3) decreased in stratospheric ozone levels, which results in increased UV radiation.
By contrast, the solar sun-spot cycle effect is responsible to small variations at about +/-0.1 degrees C, an order of magnitude less than the global warming effects of greenhouse gases.
Ongoing global warming may lead to the release of methane from frozen polar and subpolar soils (permafrost), collapse of the Gulf Stream (the North Atlantic salty warm current), high-energy weather events and yet little-specified shifts in atmospheric states (tipping points).
The progress of climate change may include periods of cooling, as may be indicated by the current slow-down of Greenland glaciers. In a recent paper by Dakos et al. (2008), abrupt climate changes in the past are shown to have been preceded by quiet periods.
The implications of climate change for ecosystems are illustrated in the new book Heatstroke: Nature in an Age of Global Warming by Anthony Barnosky, of Yale University, who states:
I think probably the biggest cause for worry is we really are seeing the disappearance of whole ecological niches, which means extinctions. By the year 2100, earth will be hotter than it’s been in 3 million years. Three million years ago, probably not one species that you’re familiar with on earth today was alive. So, yes, there were species, there will be species in the future, but the problem is that the earth that people have adapted to and are familiar with will be very different in the future. We will be outside the bounds of anything humanity has ever experienced.
Given that warnings by climate scientists have proven correct, as contrasted with watered-down reports percolating upward through bureaucracies, there is little evidence the Rudd government is listening to the recent dire warnings by climate scientists, including several petitions and requests for meetings between climate scientists and ministers.
The decline by CSIRO to report directly to the recent Senate climate inquiry, reminiscent of Howard era practices, has only been saved by the courage of individual scientists, one of whom compared Labor’s targets to ‘Russian roulette with the climate system with most of the chambers loaded’.