What do the numbers mean? These are the increases in the median temperatures Celsius from the 1955-1975 era to the 1999-2010 era in these six slices of the Arctic Circle.
Why those years? All four of those years are strong La Niña years.
What's the methodology? Splitting each slice into a 10 × 10 grid and looking for grid points that reported temperatures in at least 90% of the seasons between 1955 and 2010.
Are these numbers big or small? These numbers are hella big, as we say in Oakland. One degree in 56 years is a Big Damn Deal and the smallest number here is 1.38° C.
What's the cause? In most of the slices, the big change is albedo, areas where ice on the sea surface melts and exposes more water. Losing oceanic ice does NOT increase sea level, but it does mean more heat is absorbed. This is a feedback loop.
What's the main problem? Melting ice caps in the land mass close to the pole, most notably Greenland but also the northernmost islands of Canada.
What do humans have to do with this? Greenhouse gases are our main contribution to the mix as far as the Arctic is concerned. Carbon dioxide (CO2), which is measured in parts per billion in the atmosphere, is at an unprecedented level. The thing is, the earth's climate is a very big thing that doesn't evenly distribute anything.
If CO2 levels are higher than ever, why aren't temperatures higher than ever? That is a fair question. Not every system increases linearly. For example, gravity increases linearly when mass is increased, but decreases by the reciprocal of the square when distance increases. Other systems only increase by the square root or fourth root of some important variable. The greenhouse gas model hasn't been pushed to this level before, so maybe we will find out a linear increase isn't in the cards. In this case, slower would be better.
Is global warming to blame for Katrina or Sandy or the droughts in the Midwest? Here, the predictive model doesn't state that exactly. The most that climate scientists can say is the odds of certain things happening seem to be on the rise and that rise is definitely noticeable. For example, there are events called "100 year storms", based on the idea they can be expected to happen every 100 years. In some parts of the globe, the odds of the "100 year storm" have increased so much that they might now be fairly called "10 year storms" or even "5 year storms".
Later today, a similar recap for Antarctica.
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