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According to the graph below, Arctic sea ice volume has been decreasing from 1979-2012:
Though this graph from the ESA’s CryoSat satellite show that the volume of Arctic sea ice increased 50% from 2012 to 2013:
What is the explanation for the difference accounts of Arctic sea ice volume trends?
This question has already been answered on Skeptics.SE:
Did the Arctic Ice Sheet grow by 60% from 2012 to 2013?
The short answer is that those two graphs are consistent with each other. The first shows a 33 year trend of declining Arctic sea ice (summer minimum, I think), whereas the second highlights inter-annual variation in Arctic sea ice over the last four years. We don't expect long-term trends to be strictly monotonic increases or decreases, so both positive or negative year-on-year differences, such as those between 2012 and 2013, can be consistent with the trend.
Few things to notice are that while the Arctic Sea volume increased 50%, the volume increase was marginal compared with the volume of sea ice in 1979. Next, if you review the graph below, one year spikes are not that unusual, though if there was another 50% the volume increase from 2013 to 2014, it would be of note, given the rarity of significant year over year increases in Arctic Sea volume.
