claim: Maximum warming occurs over the surface during winter while less surface warming is found in summer when heat is being used to melt sea ice.
evidence: The international community began the long process towards building effective international and domestic measures to tackle GHG emissions (carbon dioxide, methane, nitrous oxide, hydroflurocarbons, perfluorocarbons, sulphur hexafluoride) in response to the increasing assertions that global warming is happening due to man-made emissions and the uncertainty over its likely consequences.