Environmental engineers Mikhail Chester and Arpad Horvath at the University of California at Davis say that when these costs are included, a more complex and challenging picture emerges.
In some circumstances, for instance, it could be more eco-friendly to drive into a city -- even in an SUV, the bete noire of green groups -- rather than take a suburban train. It depends on seat occupancy and the underlying carbon cost of the mode of transport.
"We are encouraging people to look at not the average ranking of modes, because there is a different basket of configurations that determine the outcome," Chester told AFP in a phone interview.
"There's no overall solution that's the same all the time."
The downside of the cool weather is that it has left crops in general well behind schedule, he said. The Alberta canola crop is two to three weeks behind development, Pauly said, while the Canadian Wheat Board estimated on Monday that Western Canada wheat and barley crops are at least 10 days behind.
One researcher, Roy Spencer, a professor at the University of Alabama-Huntsville, noted that the IPCC did not adequately calculate how clouds play a major role in ground temperatures.
Skepticism over climate science is hardly new. Indeed, skepticism has always been a part of scientific discourse and has been around global warming since the 1970s, when the theory first gained credence.