VALPARAISO | If the butler didn't do it -- but he's found standing over the warm, bloody body holding a smoking gun covered in his fingerprints -- then those wanting to pin the act on some unlikely suspect miles away still need to account for the butler.
And they can't deny the body on the ground.
That was the analogy guest lecturer David Archer used at Valparaiso University last week to describe what he called carbon dioxide's undeniable role in global warming.
Archer, a professor of geophysical sciences at the University of Chicago, compared carbon dioxide released through human activity to a butler who couldn't escape connection to the "body" of global warming.
Eschewing the euphemism "climate change," Archer said global warming has begun and its impacts will last for millennia, not just centuries.
The greenhouse theory of the earth's atmosphere trapping heat is nothing new, Archer told his audience of about 100 students, faculty and area residents. As early as 1827, French mathematician and physicist Joseph Fourier described the greenhouse effect, he said.
And Swedish chemist Svante Arrhenius calculated in 1896 that doubling carbon dioxide in the atmosphere would warm the Earth by 4 to 6 degrees Celsius, Archer said.
The smoking gun on global warming, he said, is the rise in temperature measured since the 1970s that can only be attributed to carbon dioxide and other greenhouse gases produced by combustion of fossil fuels.
Predictive models that don't factor in greenhouse gases don't reproduce actual measured temperature increases, Archer said. Only models that factor in the human activity-generated gases do, he said.
The rapid rise in global temperature could be the result of some unknown factor, Archer said, but at the moment, carbon dioxide is "the only game in town."
Technologies exist for limiting carbon dioxide emissions, he said, but the question is a social one of whether people will take steps to change their energy consumption habits.
Burning all the world's coal by the year 2300 could result in a sea level rise of 50 meters, Archer said. That would flood 3.5 percent of earth's land, home to more than one tenth of the world's population, he said.
Archer described a natural release of carbon dioxide 55 million years ago comparable to the current potential of the burning of fossil fuels. That spike resulted in warming that took the planet 100,000 years to recover from, he said.
Effects of that release, such as extinctions of species, were not as widespread as might be expected, Archer said, perhaps because the earth was still recovering from the phenomena leading to the die-off of dinosaurs 10 million years earlier.
Still, Archer noted, "it probably wasn't a good time to be alive."