Canwest News Service: The hundreds of academics who sign warnings for politicians to delay action on slashing greenhouse gas emissions do not have the same expertise as those who say human activity is causing global warming, says a new study to be released Tuesday in the Proceedings of the U.S. National Academy of Scientists. “Despite media tendencies to present both sides in (the causes of global warming) debates, which can contribute to continued public misunderstanding regarding (human-caused climate …