Al Gore’s An Inconvenient Truth (AIT) and Martin Durkin’s The Great Global Warming Swindle (TGGWS) are two documentaries presenting two very different perspectives on the current level of the scientific understanding of the Earth’s complex climate system.
AIT presents the science as being settled and computer models as being reliable. Everything bad in the world is caused by man-made CO2, from more intense hurricanes, tornados, rising sea levels, melting glaciers, floods, droughts, heat waves, and disease, to drowning polar bears.
The main thrust of TGGWS is that the science isn’t settled and there is an alternative explanation. The “enhanced greenhouse effect” isn't behaving as climate models suggest that it should, and climate change is being used as a vehicle for an anti-human, anti-capitalist, anti-mobility agenda by groups masquerading as “green.” Others are making a living by perpetuating the global warming industry, while bandwagon politicians seek to raise “green” taxes, control enterprise, mobility, and lifestyles via energy policy.
Scientists who subscribe to the claimed “consensus” view have described AIT as having the science “about right”. TGGWS, on the other hand, has been subjected to intense scrutiny and attacks from the day it was first shown on the UK’s Channel 4 TV.
Let’s examine some of the contentious points starting with Al Gore’s 600,000-year graph of temperature and CO2 derived from ice cores. Gore fails to mention that the graph shows CO2 lagging temperature by hundreds of years, rather than CO2 driving temperature, a point that was made in TGGWS. The ice core data tells us little or nothing about the sensitivity of climate to man-made CO2.
Israeli Physicist Nir Shaviv, who appeared in TGGWS, has published his empirical calculation of climate sensitivity of a maximum of 1C to 1.5C for the iconic doubling of CO2 to 560 parts per million. Contrast this with the Intergovernmental Panel on Climate Change (IPCC) computer modelled scenarios of 1.1C to 6.4C.
The infamous “hockey stick” graph of temperatures for the past 1,000 years is another point of disagreement between Gore and Durkin. It consists of a horizontal “handle” of reconstructed “proxy” data showing a stable temperature, onto which modern day instrumental measurements have been grafted to show a rapid 20th century rise in global temperatures.
The use of these two different types of data alone is ample cause for concern, yet this graph was the “poster child” of the IPPC 2001 report and replaced the one the IPCC used in their 1995 report, which clearly showed a Medieval Warm Period (MWP), followed by a cooler period known as the Little Ice Age, a version of which was used to illustrate the point in TGGWS.
Research published by Steve McIntyre and Ross McKitrick (2003, 2005) showed that the hockey stick shape was the result of seriously flawed methodology. The 2006 US National Academy of Sciences (NAS) panel upheld the major criticisms made by McIntyre and McKitrick including the advice that strip-bark bristlecone pines should not be used in climate reconstructions.
However, the controversy over the global extent of the MWP continues, given that there are regional differences in the way the world warms or cools. The temperature rise in Australia over the past 500 years is only about half of that experienced by the continents in the Northern Hemisphere during the same period.
Both the CO2 and solar theories seem to have suffered from a correlation breakdown or “divergence”. There was a period of global cooling from the 1940’s to the 1970’s despite increasing levels of atmospheric CO2. Solar activity also fell during this period suggesting a solar link.
Claims by CO2 driven warming proponents that the cooling was caused by sulphate aerosol pollution reflecting sunlight don’t really stand up to scrutiny, given the fact that emissions from developing countries have increased markedly since the late 1980’s.
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