Perhaps the most visible sign of climate change is the Arctic's shrinking sea ice cover. Concerns are growing that we are reaching a point at which the transition to an ice-free Arctic Ocean in summer becomes a rapid one.
Projections of how the climate will change in the 21st century, as humans load the atmosphere with greenhouse gases, are based largely on numerical models.
Even our early climate-change models developed in the late 1970s told us that the Arctic would suffer most from the surface warming that came with adding carbon dioxide to the atmosphere and that this would be intimately tied to the shrinking of its sea ice cover.
This is called Arctic amplification and when we look at our climate records, that is exactly what we see: the climate warming, with the strongest rises in temperature in the Arctic, and those rises linked to the loss of sea ice cover – just as projected 30 years ago.
We view the emerging Arctic amplification recorded in this study as but a harbinger of a more pronounced signal that will appear in the near future, with impacts that may extend well beyond the Arctic Ocean.
Mark Serreze is a researcher for the National Snow and Ice Data Centre, University of Colorado