Arctic warming is happening at twice the average level of global warming in a process called arctic amplification, where more warming occurs as ice is lost because less of the sun’s energy is reflected back into space.
A new report from the National Research Council (NRC) details the findings of recent Arctic research: Arctic sea ice in all seasons is declining and the rate of loss is increasing. Multiple lines of study show this is impacting weather outside of the Arctic. Increased energy (heat) in the Arctic is slowing the progress of the jet stream around globe, allowing weather systems to linger, increasing the risk of severe weather happening more often in any one place. Increased warmth also means increased moisture in the Arctic - which increases the amount of snow, which in turn causes the jet stream to concentrate winter weather in North America and Eurasia.
The tone of the NRC report is embodied in the lead workshop presentation by Dr. James Screen of Exeter University in the UK. Because of the uncertainties associated with research in this rapidly evolving field, Screen proposed an “ACID” test to validate research findings. The test asks if research findings are: "Attributable to Arctic forcing; Corroborated by multiple lines of evidence; Informed by mechanistic understanding; and Detectable in the real world."