The cost of making a Type II error could in this case be as high as the destruction of humankind, Tsigaris said.
"It is obvious that a Type II error—being unaware that global warming is caused by humans and maintaining our current [lifestyles]—is much more serious than a Type I error, which argues that humans are the cause when they are not, in terms of the costs," he said.
George Koch, a climate change researcher at Northern Arizona University in Flagstaff, agrees with Tsigaris' argument.
"We don't ignore a [person's] rising fever because we don't know the cause," Koch said. "There are ways to reduce the fever and help the patient, even if those ways are not completely or directly related to the cause—known or not."
Other experts are more cautious about taking action before proving that humans are to blame.
Timothy Ball chairs the Scientific Advisory Committee for the Natural Resources Stewardship Project, a federally incorporated nonprofit in Canada.
He says his skepticism is based on assumptions about global warming that have never been confirmed.
"In this case it is assumed carbon dioxide is a greenhouse gas that will trap heat in the atmosphere, that the levels of atmospheric carbon dioxide will increase because of human industrial activity and specifically the burning of fossil fuels, and that atmospheric carbon dioxide will double," he said.
Ball said that this hypothesis became fact before the research had begun, "because it fit a political agenda and the views of the environmentalists."
He contends that humans have already spent inordinate amounts of money to research and fight global warming, including billions of dollars in Canada alone.
If no action occurs, "nothing untoward will happen to the climate. Climate will continue to change as it always has and always will. It is good if we do nothing," he added.
Reason for Optimism
Meanwhile, the 2006 Government Economic Service report offers hope—if we take action soon.
"The risks of the worst impacts of climate change can be substantially reduced if greenhouse gas levels in the atmosphere can be stabilized" at a level just higher than what's being released now, the authors wrote.
That would require emissions to drop about 25 percent by 2050. Ultimately, stabilization would require annual emissions reductions of 80 percent.
But side benefits would include cleaner air and cost-saving efficiency, and such action will yield jobs and business opportunities.
Otherwise, the report paints a picture of worldwide floods, droughts, storms, and starvation that would hit the poorest countries and populations first. (Related news: "Warming May Spur Extinctions, Shortages, Conflicts, World Experts Warn" [April 6, 2007].)
"Rising sea levels, temperature, and precipitation caused by human lifestyles will have an impact on our health, agriculture, forestry, water, and coastal areas, as well as on other species and natural areas," Tsigaris said.
Tsigaris hopes for specific measures to reduce global emissions, including a carbon tax or a market for carbon-emitting rights with mandatory and enforceable targets on emission reductions.
He would like to see a global audit system with progress checks every five years. And he advocates cleaner, low-carbon technologies in energy usage and transportation.
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