Globally, this was the hottest winter on record, with the smallest measured Arctic sea ice maximum

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Sunday March 22, 2015 · 1:30 PM PDT

2015/03/22 · 13:30

Global map: February 2015 Blended Land & Sea Surface Temperature Anomalies in °C

The National Climatic Data Center is terse and to the point:

The globally averaged temperature over land and ocean surfaces for February 2015 was the second highest since record keeping began in 1880. Both the year-to-date (January–February) and seasonal (December–February) globally averaged temperatures were record high.

Which continues the trend that made 2014 the hottest year on record. And given these continuing records, Thursday's report from the National Snow & Ice Data Center was no surprise:

On February 25, 2015 Arctic sea ice likely reached its maximum extent for the year, at 14.54 million square kilometers (5.61 million square miles). This year’s maximum ice extent was the lowest in the satellite record, with below-average ice conditions everywhere except in the Labrador Sea and Davis Strait. The maximum extent is 1.10 million square kilometers (425,000 square miles) below the 1981 to 2010 average of 15.64 million square kilometers (6.04 million square miles) and 130,000 square kilometers (50,200 square miles) below the previous lowest maximum that occurred in 2011.
Because of the variability of ice extent at this time of year, there can be some delay in pinpointing the date of the maximum extent, as was true this year. NSIDC calculates daily ice extent as an average of the previous five days (see the Sea Ice Index documentation for more information), and we also look for a clear downward trend for a number of days.

While the downturn in extent was quite pronounced on February 25, the trend subsequently flattened. This is in part due to recent ice growth in the Bering Sea, partly balancing continued ice retreat in the Barents and Kara seas. Over the next two to three weeks, periods of increase are still possible. However, it now appears unlikely that there could be sufficient growth to surpass the extent reached on February 25.

More beneath the fold.

Map: Arctic sea ice extent for February 25, 2015 was 14.54 million square kilometers (5.61 million square miles).

As Chris Mooney notes:

The loss of sea ice around the Arctic has a vast number of consequences. They range from climatic — exposing more dark ocean water, which absorbs more solar radiation than ice does, leading to further warming — to social and cultural: Undermining the subsistence hunting techniques that Alaskan native villages have pursued atop the ice for generations.

And while the September Arctic ice minima get more attention, partially because they are more dramatic, Mooney also emphasizes that decreasing minima make it harder for ice to regrow.

But declining maxima are also important — indeed, a trend of declining maxima and minima, combined, underscore the dramatic overall change in the Arctic system.
“This new data on sea ice loss sends a clear message to the global community that the Arctic is unraveling, warming twice as fast as the rest of the planet,” said Rafe Pomerance, a former deputy assistant secretary of state who chairs a group called Arctic 21, a collection of Arctic-focused groups.

The melting ice is but an effect, and the NCDC bullet points get to the cause:

Global highlights: February 2015

During February, the average temperature across global land and ocean surfaces was 1.48°F (0.82°C) above the 20^th century average. This was the second highest for February in the 1880–2015 record. The highest temperature occurred in 1998, at 1.55°F (0.86°C) above average.

During February, the globally-averaged land surface temperature was 3.02°F (1.68°C) above the 20^th century average. This was also the second highest for February in the 1880–2015 record. The highest temperature occurred in 2002, at 3.06°F (1.70°C) above average.

During February, the globally-averaged sea surface temperature was 0.92°F (0.51°C) above the 20^th century average. This was the third highest for February in the 1880–2015 record.

The average Arctic sea ice extent for February was 370,000 square miles (6.2 percent) below the 1981–2010 average. This was the third smallest February extent since records began in 1979, according to analysis by the National Snow and Ice Data Center based on data from NOAA and NASA.

Antarctic sea ice during February was 250,000 square miles (21.4 percent) above the 1981–2010 average. This was the sixth largest February Antarctic sea ice extent on record but smallest since 2012.

According to data from NOAA analyzed by the Rutgers Global Snow Lab, the Northern Hemisphere snow cover extent during February was 230,000 square miles abovethe 1981–2010 average. This was the 14^th largest February Northern Hemisphere snow cover extent in the 49-year period of record. Eurasia had its ninth smallest February snow cover extent, while North America had its 20^th largest.

Global highlights: December–February 2015

During December–February, the average temperature across global land and ocean surfaces was 1.42°F (0.79°C) above the 20^th century average. This was the highest for December–February in the 1880–2015 record, surpassing the previous record of 2007 by 0.05°F (0.03°C).

During December–February, the globally-averaged land surface temperature was 2.63°F (1.46°C) above the 20^th century average. This tied with 2007 as the highest for December–February in the 1880–2015 record.

During December–February, the globally-averaged sea surface temperature was 0.97°F (0.54°C) above the 20^th century average. This was the third highest for December–February in the 1880–2015 record.

Global highlights: Year-to-date (January–February 2015)

During January–February, the average temperature across global land and ocean surfaces was 1.42°F (0.79°C) above the 20th century average. This was the highest for January–February in the 1880–2015 record, surpassing the previous records of 2002 and 2007 by 0.07°F (0.04°C).

During January–February, the globally-averaged land surface temperature was 2.75°F (1.53°C) above the 20^th century average. This was the second highest for January–February in the 1880–2015 record. The highest temperature occurred in 2002, at 2.79°F (1.55°C) above average.

During January–February, the globally-averaged sea surface temperature was 0.94°F (0.52°C) above the 20^th century average. This was the third highest for January–February in the 1880–2015 record.

Climate change deniers cling to a misunderstanding of what's happening to Antarctic sea ice as their last best hope of somehow disproving the scientific reality of anthropogenic climate change. But they are wrong:

As counter-intuitive as it sounds, Dr Jan Lieser, lead author of the ACE CRC report, told me the increase in sea ice is consistent with the changes in a warming world.
The sea ice is sitting at the interface of the ocean and the atmosphere, and so it gets a double-whammy effect. We actually understand the physics of this quite well. It is because of the warming that we can see the sea ice increasing at the moment.

And while the science of Antarctic sea ice increase bears further study, Antarctic sea ice isn't growing as rapidly as Arctic sea ice is melting, and its growth in no way refutes the overall trend of global warming and the climate changes it drives. It also has almost nothing to do with the overall trend of rising sea levels:

The answer seems to be that, while scientists aren’t entirely sure what’s causing increasing Antarctic sea ice, they have some plausible explanations for it. But no matter what the cause turns out to be, understanding it is unlikely to give us any reason to worry less about what’s happening to the land-based ice of Antarctica — which, unlike sea ice, presents the true concern due to its potential for driving very dramatic sea level rise.

Whether growing or shrinking, just as melting ice cubes don't cause glasses of water to overflow, melting sea ice won't contribute much to sea levels. That's not the main concern. The concern is the melting of land-based ice, which would signficantly add to sea levels. It's happening in Greenland, and it may be accelerating. And the melting of land-based ice in Antarctica is going from bad to worse. And beneath even the growing Antarctic sea ice, warm water is flowing, undermining it from beneath and accelerating the retreat of coastal glaciers.

Sea levels are rising, and as CBS News reported last month:

Rising seas could force largest-ever human exodus

The warnings continue. And continue. And Congressional Republicans remain unhinged in their efforts to deny or even censor the science. And their leading presidential candidates are no better.

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Globally, this was the hottest winter on record, with the smallest measured Arctic sea ice maximum

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