Climate Change: We have met the enemy and they are us
According to McGill University physics professor Shaun Lovejoy, we have no one to blame but ourselves for global warming in the industrial era. Lovejoy and his research team have just completed an analysis of temperature data covering more than 500 years. This study all but rules out the possibility that global warming is just a natural fluctuation in the earth's climate.
Lovejoy used a new approach in questioning whether global warming in the industrial era was caused by man-made emissions from fossil fuel burning or some other natural phenomenon involving long-term variations in temperature. The study is published online in the journal Climate Dynamics on April 6.
"This study will be a blow to any remaining climate-change deniers," Lovejoy says. "Their two most convincing arguments â€“ that the warming is natural in origin, and that the computer models are wrong â€“ are either directly contradicted by this analysis, or simply do not apply to it."
Lovejoy's study applies statistical methodology to determine the probability that global warming since 1880 is due to natural variability. His conclusion: the natural-warming hypothesis may be ruled out "with confidence levels great than 99%, and most likely greater than 99.9%."
To assess the natural variability before much human interference, the new study uses "multi-proxy climate reconstructions" developed by scientists in recent years to estimate historical temperatures, as well as fluctuation-analysis techniques from nonlinear geophysics. The climate reconstructions take into account a variety of gauges found in nature, such as tree rings, ice cores, and lake sediments. And the fluctuation-analysis techniques make it possible to understand the temperature variations over wide ranges of time scales.
For the industrial era, Lovejoy's analysis uses carbon-dioxide from the burning of fossil fuels as a proxy for all man-made climate influences â€“ a simplification justified by the tight relationship between global economic activity and the emission of greenhouse gases and particulate pollution, he says. "This allows the new approach to implicitly include the cooling effects of particulate pollution that are still poorly quantified in computer models," he adds.
Lovejoy says, without the use of huge computer models to estimate the magnitude of future climate change, his findings complement those of the International Panel on Climate Change (IPCC). His study predicts, with 95% confidence that a doubling of carbon-dioxide levels in the atmosphere would cause the climate to warm by between 2.5 and 4.2 degrees Celsius. That range is more precise than â€“ but in line with -- the IPCC's prediction that temperatures would rise by 1.5 to 4.5 degrees Celsius if CO2 concentrations double.
Read more at McGill University.
Global warming image via Shutterstock.