|The white area is the Arctic sea ice |
extent in mid-August The orange line
is the average extent for that time of year.
Map from National Snow and Ice
We've been closely watching the ice in the Arctic because it started the spring this year with the lowest extent on record for that time of year.
Would the ice be the least extensive on record in the Arctic by the time it reached its minimum for the season in September?
The answer is no, we found out this week. The extent of the ice was tied with 2007 as the second lowest on record, says the National Snow and Ice Data Center.
The summer in much of the Arctic was cooler and cloudier than in recent years, so ice melted more slowly than it otherwise would have. The NSIDC said it was remarkable the ice diminished this summer as much as it did, given the weather conditions up there.
Keeping tabs on Arctic ice is important because that ice - and that in Antarctica, helps act as the world's air conditioner. The white ice deflects much of the sun's heat back up into space. The more open water there is in the Arctic, the less heat bounces back to space, and is instead absorbed by the darker water.
Such a situation is referred to as a positive feedback, because global warming causes ice to melt, which exposes ocean water, which absorbs heat and makes climate change even worse.
What wasn't all that surprising to the NSIDC is that the record low ice extent for spring did not correlate to a record low in September. The agency said it is often the case where a trend in the beginning of the summer doesn't last all year.
The low ice extent comes in a year in which every month so far set a record for warmth for the Earth. Early data shows August will become a record warm month as well.
El Nino, a periodic warming in eastern Pacific Ocean waters near South America, combined with global warming to help us set those high temperature records. El Nino is gone, but there's usually a several months long lag between when El Nino fades and its effects on global temperatures goes away.
2017 might end up being a tad cooler than 2016 because of El Nino's disappearance, but the overall trend of a warming planet will continue as greenhouse gases continue to accumulate in the atmosphere.