claim: “The jet stream forms a boundary between the cold north and the warmer south, but the lower temperature difference means the winds are now weaker.
evidence: The feedback due to water vapor is a major factor in determining how much warming would be expected to occur with increased atmospheric concentrations of carbon dioxide, and all existing computer models assume positive feedback — that is, that as the climate warms, the amount of water vapour held in the atmosphere will increase, leading to further warming.