William Kininmonth: Don't be Gored into going along

Global warming militants don't know what they're talking about
September 12, 2006
CLIMATE change is again making headlines as the world becomes mesmerised in the public relations glare of Al Gore's movie An Inconvenient Truth. For critics and reviewers alike, the movie is further proof in their minds that we are heading for a climate catastrophe. But what's missing from the debate is sober, rational analysis of some scientific facts.
Climate change attracts attention because weather and climate extremes account for 70 per cent of natural disasters. Also, the historical evidence is that climate goes through gyrations that are beneficial or destructive for civilisations.
The periods of the Roman Empire, medieval Europe and the past 200 years were all of remarkable warmth. The Dark Ages of the first millennium and the Little Ice Age of the second were characterised by cold, by advanced mountain glaciers and by social turmoil.
For the past 10,000 years, the Earth has been near peak warmth in the climatic roller-coaster that has characterised the past million years. Yet only 20,000 years ago, great ice sheets covered much of North America and Europe; permanent glaciers were also present over southeastern Australia and Tasmania. The sea level was 130m lower than today and land bridges connected New Guinea and Tasmania with the Australian mainland. The Great Barrier Reef was but limestone cliffs bordering the Coral Sea.
The former US vice-president and his fellow travellers would have us believe that the actions of our civilisation are leading to dangerous climate change, as if climate is not inherently dangerous. There are many inconvenient truths about climate that are being ignored in the scare campaign that is being waged with relentless determination by sections of the community.
Start with carbon dioxide. As a greenhouse gas, it is a spent force for climate change; its present concentration is slightly less than 400 parts per million. Calculations show that 66 per cent of the greenhouse effect of CO2 is caused by the first 50ppm. With each doubling of concentration, (from 50 to 100, then to 200 and 400ppm), the incremental advance of the greenhouse effect is reduced.
Even for a further doubling to 800ppm, as projected by 2100 in the case of unabated fossil fuel usage, the increase in the greenhouse effect will only be 10 per cent of the present component attributable to CO2. Overall, CO2 is a relatively minor contributor to the greenhouse effect, which is dominated by the varying water vapour and clouds of the atmosphere.
Increasing the CO2 concentration will have little additional effect.
Evaporation of water vapour will constrain the Earth's temperature and prevent a runaway greenhouse effect. Back radiation from the atmosphere because of greenhouse gases (water vapour, CO2 and so on), clouds and aerosols raises surface temperatures. But surface temperatures are also constrained by evaporation of water from plants, moist soil and the oceans. The tropical oceans generally do not exceed 30C and it is only over the arid inland that daytime temperatures exceed 40C. Any increase in back radiation because of increased CO2 will largely be offset by additional evaporation that will constrain the rise of surface temperature.
The oceans are the flywheels of the climate system. The warm tropical oceans are but a thin lens about 100m in thickness that overlay the cold abyss, extending to depths averaging about 5km. We are familiar with El Nino events, when changed upwelling modifies the entrainment of cold sub-surface water into the warm surface layer of the equatorial Pacific Ocean. As US climatologist Michael Glantz has noted, the changed surface temperature patterns modify the atmospheric circulation and spawn natural disasters such as floods, droughts and storms across the globe.
Global warming is constrained by the need to warm the ocean in advance. The polar ice sheets of Greenland and Antarctica are fundamentally stable. Ice cores recovered from there confirm that the ice sheets have survived previous interglacials and have likely existed for more than one million years. The surface elevation of the ice sheets is more than 3km above sea level across much of their extensive plateaus and temperatures remain below minus 10C during the brief summer. It is only at the lower elevations of the coastal margins that temperatures rise above freezing for a few months and the strong solar radiation causes ice-melt.
Collapse of the polar ice sheets and a sea level rise of several metres is an unlikely scenario.
There are predictions, based on computer models, that Australia's rainfall will decrease as CO2 concentrations rise. According to published Bureau of Meteorology data, Australia (except for the southwest corner) was wetter during the second half of the 20th century than during the first. Against the prediction, as CO2 concentrations increased, there was an increase in continent-wide rainfall. These trends are likely to be no more than coincidence in the cycles of climate variability.
The Earth's climate system is extremely complex and we have only limited knowledge of many of its aspects. International collaboration is slowly unravelling some of the secrets and providing the basis for preparation and adaptation to change.
Scientists' continuing inability to predict with confidence a season in advance should be cause for hesitation when projections of decades to centuries are made. Computer models are not reality and alarmist predictions have no sound basis.
William Kininmonth, a former head of the National Climate Centre and a consultant to the World Meteorological Organisation, is author of Climate Change: A Natural Hazard (Multi-Science Publishing Co, 2004).