The extent of Arctic sea ice has dipped below where it was at this time of year in 2007, the worst year recorded for sea ice. Within the next few months, we will see whether it goes on to set a new record low. If so, perhaps it could be the sort of dramatic event that drives people to take climate change more seriously.
It is important to understand that the maximum extent of sea ice during the winter is a less important climatic indicator than the minimum extent in summer. The Arctic is always going to be cold and dark in the winter, when it is hardly receiving any sunlight. As a result, at least a thin layer of ice will form, establishing a large extent of frozen ocean. What is vanishing is the multi-year ice, which endures from year to year. Climate deniers trumpeted how the maximum extent of ice this year was close to the 1979 to 2000 average, yet the major trend in ice extent and volume is ever downwards.
If the Arctic ends up ice-free in the summer, there will be numerous consequences. Species that depend on sea ice – including narwhals, seals, and polar bears – will be threatened. Also, migration between the Pacific and Atlantic will likely allow the emergence of invasive species. Because losing summer sea ice means losing a big white sheet that reflects sunlight back into space, it would also cause further warming.