Guest Opinion; Dr. Tim Ball
The only place in the world where CO2 increase causes a temperature increase is in climate models, including those of the Intergovernmental Panel on Climate Change (IPCC). The assumption that a CO2 increase causes a temperature increase is central to the anthropogenic global warming (AGW) hypothesis. If incorrect, failure of this assumption alone should guarantee rejection of the hypothesis. In proper scientific procedure if the hypothesis is rejected the null hypothesis is considered. In this case, the null hypothesis is that CO2 is not causing global warming. The IPCC never considered the null hypothesis. Ironically and unwittingly, James Hansen proved the null hypothesis in his first major attempt to push his agenda that CO2 is causing global warming or climate change.
The first IPCC Report appeared in 1990, but the more orchestrated push of the AGW hypothesis occurred with the 1995 Report. Four years later an Antarctic ice core record produced by Petit et al., was published in Nature. The article included a graphic that juxtaposed temperature, CO2, methane, and insolation (Figure 1).
It appeared to provide support for the anthropogenic global warming (AGW) hypothesis. It looked like temperature increase preceded CO2 increase. I recall one of the authors, Jean Jouzel, warning in an interview not to rush to judgment. He noted it was 420,000 years plotted on a 10 cm long graph, complicated by a 70-year smoothing average that masked much detail. He was prescient. AGW advocates ignored the warning and used the graph as support for their hypothesis. It effectively became the forerunner to the ‘hockey stick’ in grabbing media and public attention.
However, in proper scientific tradition Hubertus Fischer, of the Scripps Institution of Oceanography was already questioning the cause and effect relationship with a 1999 paper. In 2001, Manfred Mudelsee published another paper that challenged the relationship in Quaternary Science Review.
Lowell Stott followed with a 2007 paper in Science titled, Southern Hemisphere and Deep-Sea Warming Led Deglacial Atmospheric CO2 Rise and Tropical Warming. Sherwood and Craig Idso maintain the best website on all issues related to CO2. They provide a list of papers that yield further evidence that the relationship is opposite to the IPCC assumption. None of this ever received mainstream media attention.
Failed predictions, which began with the 1990 IPCC Report, were one of the first signs of problems. Instead of revisiting the assumptions and science of their hypothesis they made the first political adjustment by creating projections to replace predictions. They compounded their duplicity by allowing the media and public to believe they were predictions. Hansen et al,
produced a forerunner of the projection scenarios in 1988, the same year he appeared before the US Senate committee to kick-start the entire AGW deception. Figure 2 shows the original graph from that article.
In an incisive article on Hansen’s model Anthony Watts provided a modified version of Figure 2 with actual temperatures added (Figure 3).
Hansen et al, postulated three scenarios,
A: increase in CO2 emissions by 1.5% per year
B: constant increase in CO2 emissions after 2000
C: No increase in CO2 emissions after 2000
Naturally, the mainstream media focused on the temperature projections of scenario A. Some of us knew Scenarios A and B were unrealistic, and now we know how wrong they were. I had many discussions in the 1990s with Canadian ice core expert Fritz Koerner about his Arctic Island cores. He told me they showed temperature increasing before CO2. In retrospect, scenario C is more interesting and more telling.
Hansen presents it as the ideal scenario. He is telling political leaders and media what will happen if humans stop adding CO2 to the atmosphere. Salvation! Temperatures will stop increasing. Ironically, this is equivalent to running the model as if CO2 was not causing warming. In doing so, it effectively presents the null hypothesis to the AGW hypothesis. It shows what would happen if CO2 was not the cause of warming. It approximates reality.
Figure 4 shows similar scenario projections from the IPCC AR4 2007 Report overlain with actual CO2 increases. The difference with Hansen is in the low scenario. The IPCC say in AR4,
Model experiments show that even if all radiative forcing agents were held constant at year 2000 levels, a further warming trend would occur in the next two decades at a rate of about 0.1°C per decade, due mainly to the slow response of the oceans.
Figure 4 appears to show that the “Best” and “High” projections are primarily a function of the increase in atmospheric CO2 levels. Even the “Low” projection diverges from the actual temperature trend shown for the surface (HadCrut) and satellite (UAH) records. Besides confirming the null hypothesis the results show that the IPCC claim of continued increase because of slow ocean response is also incorrect.
Hansen limited his research and climate models to human causes of climate change. He produced two projections that argued CO2 would continue to increase. In doing so, he predetermined the outcome. He confirmed his hypothesis that continued human production would cause global warming, but only in the models. However, apparently driven by his political agenda, he had to convince politicians that a reduction in CO2 output would solve the problem. To do this, he ran his model to show what happens with no CO2 increase. It produced a curve that fits the actual temperature trend in the intervening 27 years. This is the result you expect if you accept the null hypothesis that CO2 from any source is not causing global warming. Thanks, Jim, enjoy your retirement.