The study, led by McGill physics professor Shaun Lovejoy, analyzed temperature records since 1500 and concluded that global warming is not due to a natural fluctuation of Earth's climate cycles.
"This study will be a blow to any remaining climate-change deniers," Lovejoy told McGill Reporter. "Their two most convincing arguments - that the warming is natural in origin, and that the computer models are wrong - are either directly contradicted by this analysis, or simply do not apply to it."
Lovejoy applied statistical methods to calculate the probability that global warming, which started in the 1880s, might be due to the Earth's climate variations. After analyzing his data, he concluded that global warming is not due to natural tendencies and is 99.9 percent sure of his conclusion.
To find out the extent of variability before human intervention was introduced to nature, he used the "multi-proxy climate reconstructions" to gather data on previous temperature levels as well as to analyze the fluctuations of the Earth's climate over the years. These reconstructions involve a lot of natural factors such as ice cores, tree rings, and lake sediments.
As for the industrial era, he incorporated in his analysis the levels of carbon dioxide produced by fossil fuel as a representative of all man-made interventions in nature. This was governed by the proven idea that climate change is heavily influenced by greenhouse emissions.
"This allows the new approach to implicitly include the cooling effects of particulate pollution that are still poorly quantified in computer models," Lovejoy explained to McGill Reporter.
Although Lovejoy's study does not use any computer models like most climate change studies, his findings are in line with the conclusions made by the International Panel on Climate Change (IPCC). In his study, Lovejoy predicted, with 95 percent confidence, that a 50 percent increase in carbon dioxide emissions will cause a temperature increase by 2.5 to 4.2 degrees Celsius.
Further details of this study were published in the April 6 issue of Climate Dynamics.
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