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State of Polar Sea Ice – September 2014: Arctic Sea Ice Minimum and Antarctic Sea Maximum

Global polar sea ice area in September 2014 remained at or near climatological normal conditions (1979-2008).  This situation has held true since early 2013 – a clear departure from conditions during the past 10+ years.  Global sea ice area values consist of two components: Arctic and Antarctic sea ice.  Conditions are quite different between these two regions: there is abundant Antarctic sea ice while Arctic sea ice remained well below normal again during 2014.  I’ll discuss both regions below.

Arctic Sea Ice

According to the NSIDC, September 2014′s average extent was 5.28 million sq. km., a 1.24 million sq. km. below normal conditions.  This value is the minimum for 2014 as less sunlight and colder fall temperatures now allow for melting ice.  September 2014 sea ice extent continued a two-plus year-long trend of monthly mean below normal values.  The deficit from normal was different each month during that time due to weather conditions overlaying longer term climate signals.

Sea ice anomalies at the edge of the pack are of interest.  Laptev and East Siberian Sea ice, for instance, was lower than their respective normals this year while Beaufort Sea and Canadian Archipelago ice maintained higher ice extent this year than they did a few years ago.  Arctic Basin ice extent was lower than its normal, but higher than it was during the late-2000s.

September 2014 average sea ice extent was the sixth lowest in the satellite record (post-1979).  Figure 1 shows that the September linear rate of decline is 13.3% per decade (blue line) relative to the 1981 to 2012 mean, compared to 2.6% per decade decline for March through 2014.  Summer ice is more affected from climate change than winter ice.  Of note, the trend through September 2013 was 13.7%, so this year’s minimum, while historically significant, was not as bad as it was during recent years.

 photo Arctic_monthly_sea_ice_extent_201409_zpsc2d01bbf.png

Figure 1 – Mean Sea Ice Extent for September: 1979-2014 [NSIDC].

Arctic Pictures and Graphs

The following graphic is a satellite representation of Arctic ice as of April 1st, 2014:

 photo Arctic_sea_ice_20140401_zpsdd9dbc04.png

Figure 2 UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20140401.

Compare that with the following graphic – a satellite representation of Arctic ice as of October 7th, 2014:

 photo Arctic_sea_ice_20141007_zps42639b5f.png

Figure 3UIUC Polar Research Group‘s Northern Hemispheric ice concentration (color contours) from 20141007.  Recent snowfall is indicated by gray-scheme contours over land.

As described above, the 2014 melt season ended with the sixth lowest Arctic sea ice extent during the satellite era.  Approximately 10 million sq. km. of sea ice  melted again this year.  That isn’t a record (11.5 million sq. km. melted in 2012), but that is a lot of melted ice.

Of greater importance is the overall health of the ice pack, which we can begin to ascertain by looking at the volume of ice, as in Figure 4:

 photo SeaIceVolumeAnomaly_20140930_zps48c8bf58.png

Figure 4PIOMAS Arctic sea ice volume time series through September 2014.

This graph shows something unique: a recent resurgence of ice volume anomalies during the past 2-3 years.  You can see that in 2011 and 2012, Arctic sea ice volume reached values below the 2nd standard deviation from normal – near -7000 and -8000 km^3.  2013 looked a bit better and 2014 looks better still: volume anomalies are back above the long-term trend line.  While that isn’t enough to declare no problems exist in the Arctic, the situation certainly is different from it was just a couple of years ago.  Put another way, these graphics show something quite different from the strident proclamations of doom from climate activists in early 2013 when holes and cracks were seen earlier than normal on Arctic sea ice.  At the time, they wondered (too loudly at times) whether an ice-free summer was in our immediate future.  I cautioned against such radical conclusions at the time and continue to do so now.  While not healthy, Arctic sea ice isn’t in as bad a shape as some wanted to believe.

Arctic Sea Ice Extent

Take a look at September’s areal extent time series data:

 photo N_stddev_timeseries_20141001_1_zpsa497f1ad.png

Figure 5NSIDC Arctic sea ice extent time series through early Ocrtober 2014 (light blue line) compared with four recent years’ data, climatological norm (dark gray line) and +/-2 standard deviation envelope (light gray).

This figure puts 2014 into context against other recent winters.  As you can see, Arctic sea ice extent was at or below the bottom of the negative 2nd standard deviation from the 1981-2012 mean during each of the past five years.  The 2nd standard deviation envelope covers 95% of all observations.  That means the past five years’ ice extents were extremely low compared to climatology.  Thankfully, 2014 sea ice extent did not set another all-time record.  This year’s values were within the 2nd standard deviation envelope and look similar to 2013’s.

Antarctic Pictures and Graphs

Here is a satellite representation of Antarctic sea ice conditions from April 2nd, 2014:

 photo Antarctic_sea_ice_20140401_zpsd15f0ddf.png

Figure 6UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20140402.

And here is the corresponding figure from October 7th, 2014:

 photo Antarctic_sea_ice_20141007_zps57847a53.png

Figure 7UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20141007.

Here we see evidence that the Antarctic is quite different from the Arctic.  Instead of record minimums, Antarctic sea ice is recording record maximums.  The April graphic begins the story: the Antarctic sea ice minimum value this year was quite high, so ice started from a different (higher) point than in recent decades.  This new pattern evolved during the past few years and absent additional changes is likely to continue for the foreseeable future.  With a head-start on ice extent, mid-winter ice grew to the largest extent on record: 20.03 million sq. km., 1.24 million sq. km. above the 1981 to 2010 average for September ice extent.

Figure 8 shows this situation in time series form:

 photo S_stddev_timeseries_20141001_zps52351c47.png

Figure 8NSIDC Antarctic sea ice extent time series through early October 2014.

The big surge in extent in late September is all the more impressive because it set another all-time record for extent, as also happened in 2012 and 2013, as Figure 9 shows:

 photo Antarctic_monthly_sea_ice_extent_201409_zps735c9cd0.png

Figure 9 – Mean Antarctic Sea Ice Extent for September: 1979-2014 [NSIDC].

You’re eyes aren’t deceiving you: the Antarctic September sea ice extent trend is opposite that of the Arctic sea ice extent trend.  The Antarctic trend is +1.3%/decade.  The reason for this seeming discrepancy is rooted in atmospheric chemistry and dynamics (how and why the atmosphere moves the way it does) and ice dynamics.  A reasonable person without polar expertise likely looks at Figures 1 and 9 and says, “I don’t see evidence of catastrophe here.   I see something bad in one place and something good in another place.”  For people without the time or inclination to invest in the layered nuances of climate, most activists come off sounding out of touch when they always preach gloom and doom.  If climate change really were as clearly devastating as activists screamed it was, wouldn’t it be obvious in all these pictures and plots?  Or, as I’ve commented at other places recently, do you really think people who are insecure about their jobs and savings even have the time for this kind of information?

Policy

Given the lack of climate policy development at a national or international level to date, Arctic conditions will likely continue to deteriorate for the foreseeable future.  This is especially true when you consider that climate effects today are largely due to greenhouse gas concentrations from 30 years ago.  It takes a long time for the additional radiative forcing to make its way through the entire climate system.  The Arctic Ocean will soak up additional energy (heat) from the Sun due to lack of reflective sea ice each summer.  Additional energy in the climate system creates cascading and nonlinear effects throughout the system.  For instance, excess energy can push the Arctic Oscillation to a more negative phase, which allows anomalously cold air to pour south over Northern Hemisphere land masses while warm air moves over the Arctic during the winter.  This in turn impacts weather patterns throughout the year (witness winter 2013-14 weather stories) across the mid-latitudes and prevents rapid ice growth where we want it.

More worrisome for the long-term is the heat that impacts land-based ice.  As glaciers and ice sheets melt, sea-level rise occurs.  Beyond the increasing rate of sea-level rise due to thermal expansion (excess energy, see above), storms have more water to push onshore as they move along coastlines.  We can continue to react to these developments as we’ve mostly done so far and allocate billions of dollars in relief funds because of all the human infrastructure lining our coasts.  Or we can be proactive, minimize future global effects, and reduce societal costs.  The choice remains ours.

Errata

Here are my State of Polar Sea Ice posts from April 2014 and October 2013.


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Deep Decarbonization Pathways Interim Report Released

An international group of folks put together an interim report analyzing “Deep Decarbonization Pathways”.  Decarbonization refers to the process of using less carbon within an economy.  The intent of the report was to show ways forward to keep global mean temperatures below 2C.  Readers of this blog know that I no longer think such a goal is achievable given the scope and scale of decarbonization.  We have not moved from a “business-as-usual” approach and have run out of time to reduce GHG emissions prior to relevant limits to meet this goal.  I argue the exact opposite of what the authors describe in their summary:

We do not subscribe to the view held by some that the 2°C limit is impossible to achieve and that it should be weakened or dropped altogether.

Thus the main problem with this report.  They’re using a threshold that was determined without robustly analyzing necessary actions to achieve it.  In other words, they a priori constrain themselves by adopting the 2C threshold.  Specifically, a more useful result would be to ascertain what real-world requirements exist to support different warming values in terms real people can intuitively understand.  The report is not newsworthy in that it reaches the same results that other reports reached by making similar assumptions.  Those assumptions are necessary and sufficient in order to meet the 2C threshold.  But examination unveils something few people want to recognize: they are unrealistic.  I will say that this report goes into more detail than any report I’ve read to date about the assumptions.  The detail is only slightly deeper than the assumptions themselves, but are illuminating nonetheless.

An important point here: the authors make widespread use of “catastrophe” in the report.  Good job there – it continues the bad habit of forcing the public to tune out anything the report has to say.  Why do people insist on using physical science, but not social science to advance policy?

On a related note, the report’s graphics are terrible.  They’re cool-color only, which makes copy/paste results look junky and interpretation harder than it should be.  So they put up multiple barriers to the report’s results.  I’m not sure why if the intent is to persuade policy makers toward action, but …

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2014 US National Climate Assessment Released

The US Global Change Research Program issued its latest National Climate Assessment today. There are lots of goodies in it.  I want to focus on a couple of things that caught my eye in an initial skim.

Impacts will increase in frequency and severity (no big surprise there). This assessment includes up-t0-date research results on those impacts.  Like most reports, they leave `Responses` as a final category.  I understand the logic of laying out the evidence of climate change and its impacts prior to discussing solutions, but as I’ve written before today, people primarily respond to solutions and not problems.  Only the most dedicated readers will make it all the way through the report to get to the Response section.  My worry is that the Response section will not be the focus of activists’ attention; a continuation of decades of wasted energy.

Extreme Weather

The report summarizes the state-of-the-science well: “Over the last 50 years, much of the U.S. has seen increases in prolonged periods of excessively high temperatures, heavy downpours, and in some regions, severe floods and droughts.”  That is accurate.  I do not think one example is valid, however.  The report discusses anomalous warmth and dryness in Texas and Oklahoma in 2011.  I do not argue that the event occurred; I blogged about it and the subsequent 2012 Great Plains drought.  Where I deviate from the Assessment is this: there is scant evidence that the 2011 Southern Plains drought had a strong climate signal.  The same goes for the 2012 Great Plains drought.  Instead, these droughts were strongly linked to drier summertime conditions during the recent decade as part of a regime shift, most probably due to natural decadal variability (Hoerling et al. 2014).  The 2011 Texas heat wave was more likely to occur than it was 40 years ago.  This is not the same thing as identifying a clear attribution – something that remains at the cutting edge of climate science.

Likewise, the largest determinant of Atlantic hurricanes remains natural variability.  The Assessment’s statement that Atlantic hurricane activity increased since the early 1980s is true, but there are important details to consider.  The Atlantic signal is opposite the global signal (a small reduction in overall hurricane activity in that same time period), so regional effects are important to consider.  The Atlantic Multidecadal Oscillation is currently in a positive phase (since the early 1980s – isn’t that interesting?), which includes a warmer than usual Atlantic Ocean.  All else equal, this facilitates tropical storm development, which we’ve seen.

The Assessment’s conclusion stands in direct contrast to a couple of peer-reviewed papers, including Chylek and Lesins 2008 (we find no increase in the number of major hurricanes (category 3–5); If there is an increase in hurricane activity connected to a greenhouse gas induced global warming, it is currently obscured by the 60 year quasi-periodic cycle.) and Enfield and Cid-Serrano 2009 (Projections to the year 2025 show that the cumulative change in summer warm pool size since 1975 will depend critically on whether a subsequent cooling in the multidecadal cycle occurs, comparable to the warming between 1975 and 2000 AD.)  In other words, determining how man-made warming affects Atlantic hurricanes will not be detectable from the natural signal for many years to come.

That doesn’t mean we do nothing.  To the contrary, I argue that we need to adapt our current infrastructure to our current climate.  Multi-billion dollar events occur today.  Most of that is related to increases in population and wealth, as the Assessment reports.  We can lessen impacts by hardening our infrastructure (taking the likeliest climate effects into account) today while simultaneously mitigating future climate effects.  One should not happen without the other, but at a minimum, we need to adapt to today’s climate while recognizing tomorrow’s climate will be different.

Southwest

I want to cite the impacts the Assessment identifies for the Southwest, which includes California, Nevada, Utah, Colorado, New Mexico, and Arizona.  This region is the hottest and driest of the US.  They include: “increased heat, drought, insect outbreaks, and wildfires.  Declining water supplies, reduced agricultural yields, health impacts in cities due to heat, and flooding and erosion in coastal areas are additional concerns.”

Key messages:

  • Reduced snowpack and streamflow
  • Agricultural threats
  • Increased wildfire
  • Sea level rise
  • Heat threats to health

Southwest Responses

I really want to highlight one of the responses.  Without having read through all the responses carefully, I want to point out that I hope other responses are better than this one.  The selected response shows one scenario that could theoretically achieve 80% GHG reductions from 1990 levels by 2050:

 photo SW_energy-generation-by-2045_12447_v10-hi_0_zps2c73bc2c.jpg

I’ll discuss Colorado here; the Assessment included references to exhaustive reports for California, which I’ll cover in the future.

The latest data for Colorado’s net generation shares (2012) demonstrate the immense challenge confronting the scenario shown above.  Broken down by percentage: coal (64.3%), natural gas (20.1%), wind (11.2%), hydroelectric (3.7%), solar (0.3%), biomass and other (0.1% each).  The scenario above (still trying to pin down units) shows that wind can become the dominant source of electricity generation.  In principle, I agree.  But wind would have to switch places with coal as the dominant generation type by 2050 to achieve 80% GHG reductions.  Wind has penetrated the electricity generation market, which I fought for and applaud.  But it still trails natural gas (1/2 the generation) and significantly trails coal (1/5 the generation).  Changing those ratios requires a policy upheaval which I don’t think is likely.  Renewables will eventually supplant fossil fuels as primary generation technologies.  At this time, I don’t think it will happen in Colorado or anywhere else (California has an outside shot) by 2050.

Conclusion

This Assessment is useful for academics and activists, but is probably not useful for the general public.  A brief review of the Response section didn’t convince me that the writers and editors had the public as their primary audience.  I’ve seen Twitter explode today with comments regarding how people were at the forefront of this report, how actionable the information is, etc.  I’m not convinced yet.  Hopefully that will change.


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State of Polar Sea Ice – March 2014: Arctic Sea Ice Maximum and Antarctic Sea Minimum

Global polar sea ice area in March 2014 remained at or near climatological normal conditions (1979-2008).  This represents early 2013 conditions continuing to present when sea ice area was at or above the average daily value.  Global sea ice area values consist of two components: Arctic and Antarctic sea ice.  Conditions are quite different between these two regions: Antarctic sea ice continues to exist abundantly while Arctic sea ice remained well below normal again during the past five months.

The NSIDC made a very important change to its dataset in June.  With more than 30 years’ worth of satellite-era data, they recalculated climatological normals to agree with World Meteorological Organization standards.  The new climatological era runs from 1981-2010 (see Figure 6 below).  What impacts did this have on their data?  The means and standard deviations now encompass the time period of fastest Arctic melt.  As a consequence, the 1981-2010 values are much lower than the 1979-2000 values.  This is often one of the most challenging conditions to explain to the public.  “Normal”, scientifically defined, is often different from “normal” as most people refer to it.  U.S. temperature anomalies reported in the past couple of years refer to a similar 1981-2010 “normal period”.  Those anomalies are smaller in value than if we compared them to the previous 1971-2000 “normal period”.  Thus, temperature anomalies don’t seem to increase as much as they would if scientists referred to the same reference period.

Arctic Sea Ice

According to the NSIDC, March 2014′s average extent was 14.80 million sq. km., a 730,000 sq. km. difference from normal conditions.  This value is the maximum for 2014 as more sunlight and warmer spring temperatures now allow for melting ice.  March 2014 sea ice extent continued a nearly two-year long trend of below normal values.  The deficit from normal was different each month during that time due to weather conditions overlaying longer term climate signals.  Arctic sea ice extent could increase during the next month or so depending on specific wind conditions, but as I wrote above, we likely witnessed 2014’s maximum Arctic sea ice extent 10 or so days ago.

Sea ice anomalies at the edge of the pack are of interest.  There is slightly more ice than normal in the St. Lawrence and Newfounland Seas on the Atlantic side of the pack.  Barents sea ice area, meanwhile, is slightly below normal.  Bering Sea ice recently returned to normal from below normal, while Sea of Okhotsk sea ice remains below normal.  The ice in these seas will melt first since they are on the edge of the ice pack and are the thinnest since they just formed in the last month.

March average sea ice extent for 2014 was the fifth lowest in the satellite record.  The March linear rate of decline is 2.6% per decade relative to the 1981 to 2012 average, as Figure 1 shows (compared to 13.7% per decade decline for September: summer ice is more affected from climate change than winter ice).  Figure 1 also shows that March 2014′s mean extent ranked fifth lowest on record.

 photo Arctic_monthly_sea_ice_extent_201403_zpsf13de46a.png

Figure 1 – Mean Sea Ice Extent for March: 1979-2014 [NSIDC].

Arctic Pictures and Graphs

The following graphic is a satellite representation of Arctic ice as of October 1st, 2013:

 photo Arctic_sea_ice_20131001_zps56b337ee.png

Figure 2UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20131001.

The following graphic is a satellite representation of Arctic ice as of January 15th, 2014:

 photo Arctic_sea_ice_20140115_zps96036b51.png

Figure 3UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20140115.

The following graphic is a satellite representation of Arctic ice as of April 1st, 2014:

 photo Arctic_sea_ice_20140401_zpsdd9dbc04.png

Figure 4 UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20140401.

I captured Figure 2 right after 2013’s date of minimum ice extent occurrence.  I wasn’t able to put together a post in January on polar sea ice, but captured Figure 3 for future reference.  You can see the rapid growth of ice area and extent in three month’s time.  Since January, additional sea ice formed, but not nearly as much as during the previous three months.  Figure 4 shows conditions just after the annual maximum sea ice area occurred.  From this point through late September, the overall trend will be melting ice – from the edge inward.

The following graph of Arctic ice volume from the end of January (PIOMAS updates are not available from the end of February or March) demonstrates the relative decline in ice health with time:

 photo SeaIceVolumeAnomaly_20140131_zpse02b6133.png

Figure 5PIOMAS Arctic sea ice volume time series through January 2014.

The blue line is the linear trend, identified as -3,000 km^3 (+/- 1,000 km^3) per decade.  In 1980, there was a +5,000 km^3 anomaly compared to 2013’s -6,000 km^3 anomaly – a difference of 11,000 km^3.  How much ice is that?  That volume of ice is equivalent to the volume in Lake Superior!

Arctic Sea Ice Extent

Take a look at March’s areal extent time series data:

 photo N_stddev_timeseries_20140401_1_zps069b9c1d.png

Figure 6NSIDC Arctic sea ice extent time series through early April 2014 (light blue line) compared with four recent years’ data, climatological norm (dark gray line) and +/-2 standard deviation envelope (light gray).

This figure puts winter 2013-14 into context against other recent winters.  As you can see, Arctic sea ice extent was at or below the bottom of the negative 2nd standard deviation from the 1981-2012 mean.  The 2nd standard deviation envelope covers 95% of all observations.  That means the past five winters were extremely low compared to climatology.  With the maximum ice extent in mid-March, 2014’s extent now hovers near record lows for the date.  Previous winters saw a late-season ice formation surge caused by specific weather patterns.  Those patterns are not likely to increase sea ice extent this boreal spring.  This doesn’t mean much at all for projections of minimum sea ice extent values, as the NSIDC discusses in this month’s report.

Antarctic Pictures and Graphs

Here is a satellite representation of Antarctic sea ice conditions from October 1, 2013:

 photo Antarctic_sea_ice_20131001_zps2fb64db9.png

Figure 7UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20131001.

And here is the corresponding graphic from January 15th, 2014:

 photo Antarctic_sea_ice_20140115_zpsd2a383a2.png

Figure 8UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20140115.

The following graphic is a satellite representation of Antarctic ice as of April 2nd, 2014:

 photo Antarctic_sea_ice_20140401_zpsd15f0ddf.png

Figure 9UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20140402.

Antarctic sea ice clearly hit its minimum between mid-January and early April.  In fact, that date was likely six weeks ago.  Antarctic sea ice is forming again as austral fall is underway.  As in recent austral summers, the lack of sea ice around some locations in Figure 8 is related to melting land-based ice.  Likewise,  sea ice presence around other locations is a good indication that there is less land-based ice melt.  Figure 8 looks different from other January’s prior to 2012 and 2013.  Additionally, Antarctic weather in recent summers differed from previous years in that winds blew land-based ice onto the sea, especially east of the Antarctic Peninsula (jutting up towards South America), which replenished the sea ice that did melt.  The net effect of the these and other processes kept Antarctic sea ice at or above the 1979-2008 climatology’s positive 2nd standard deviation, as Figure 10 below shows.

Finally, here is the Antarctic sea ice extent time series through early April:

 photo S_stddev_timeseries_20140401_zpscadac617.png

Figure 10NSIDC Antarctic sea ice extent time series through early April 2014.

The fact that Arctic ice extent continues well below average while Antarctic ice extent continues well above average for the past couple of years works against climate activists who claim climate change is nothing but disaster and catastrophe.  A reasonable person without polar expertise likely looks at Figures 6 and 10 and says, “I don’t see evidence of catastrophe here.   I see something bad in one place and something good in another place.”  For people without the time or inclination to invest in the layered nuances of climate, most activists come off sounding out of touch.  If climate change really were as clearly devastating as activists screamed it was, wouldn’t it be obvious in all these pictures and plots?  Or, as I’ve commented at other places recently, do you really think people who are insecure about their jobs and savings even have the time for this kind of information?  I don’t have one family member or friend that regularly questions me about the state of the climate, despite knowing that’s what I research and keep tabs on.  Well actually, I do have one family member, but he is also a researcher and works in supercomputing.  Neither he nor I are what most people would consider “average Joes” on this topic.

Policy

Given the lack of climate policy development at a national or international level to date, Arctic conditions will likely continue to deteriorate for the foreseeable future.  This is especially true when you consider that climate effects today are largely due to greenhouse gas concentrations from 30 years ago.  It takes a long time for the additional radiative forcing to make its way through the entire climate system.  The Arctic Ocean will soak up additional energy (heat) from the Sun due to lack of reflective sea ice each summer.  Additional energy in the climate system creates cascading and nonlinear effects throughout the system.  For instance, excess energy pushes the Arctic Oscillation to a more negative phase, which allows anomalously cold air to pour south over Northern Hemisphere land masses while warm air moves over the Arctic during the winter.  This in turn impacts weather patterns throughout the year (witness winter 2013-14 weather stories) across the mid-latitudes and prevents rapid ice growth where we want it.

More worrisome for the long-term is the heat that impacts land-based ice.  As glaciers and ice sheets melt, sea-level rise occurs.  Beyond the increasing rate of sea-level rise due to thermal expansion (excess energy, see above), storms have more water to push onshore as they move along coastlines.  We can continue to react to these developments as we’ve mostly done so far and allocate billions of dollars in relief funds because of all the human infrastructure lining our coasts.  Or we can be proactive, minimize future global effects, and reduce societal costs.  The choice remains ours.

Errata

Here are my State of Polar Sea Ice posts from October and July 2013. For further comparison, here is my State of Polar Sea Ice post from late March 2013.


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State of Polar Sea Ice – September 2013: Arctic Sea Ice Minimum and Antarctic Sea Maximum

Global polar sea ice area in September 2013 was slightly below climatological normal conditions (1979-2008).  This represents a change from early 2013 conditions when sea ice area was at or above the average daily value.  Antarctic sea ice continues to exist abundantly while Arctic sea ice fell below normal again during the month.

The NSIDC made a very important change to its dataset in June.  With more than 30 years’ worth of satellite-era data, they recalculated climatological normals to agree with World Meteorological Organization standards.  The new climatological era runs from 1981-2010 (see Figure 6 below).  What impacts did this have on their data?  The means and standard deviations now encompass the time period of fastest Arctic melt.  As a consequence, the 1981-2010 values are much lower than the 1979-2000 values.  This is often one of the most challenging conditions to explain to the public.  “Normal”, scientifically defined, is often different than “normal” as most people refer to it.  U.S. temperature anomalies reported in the past couple of years refer to a similar 1981-2010 “normal period”.  Those anomalies are smaller in value than if we compared them to the previous 1971-2000 “normal period”.  Thus, temperature anomalies don’t seem to increase as much as they would if scientists referred to the same reference period.

Arctic Sea Ice

According to the NSIDC, September 2013′s average extent was only 5.35 million sq. km., a 1.17 million sq. km. difference from normal conditions.  This value is the minimum for 2013 as less sunlight and cooler autumn temperatures now allow for ice to refreeze.  September 2013 sea ice extent was 1.72 million square kilometers higher than the previous record low for the month that occurred in 2012.  The shift from a record low value one  year to a non-record low the next is completely normal.  Indeed, had Arctic sea ice extent fallen to a new record low, conditions this year would have been much more inhospitable to sea ice than they were.  To be clear, I do not cheer new record lows.  They are worthy of discussion not simply because of the record they set, but because they are part of a larger ongoing trend.  This year’s minimum extent value did not break that trend, it continued it.

Overall, conditions across the Arctic Ocean this summer prevented record-setting ice loss.  There were more clouds in 2013 than 2012.  Clouds reflect most incoming solar radiation, which means less sea ice melts.  At the end of the melt season, many small seas had normal sea ice extent, which is to say none.  Anomalous areas include the East Siberian Sea and the Arctic Basin, which recorded less sea ice extent than normal.

September average sea ice extent for 2013 was the sixth lowest in the satellite record. The 2012 September extent was 32% lower than this year’s extent.  The September linear rate of decline is 13.7% per decade relative to the 1981 to 2010 average, as Figure 1 shows.  Figure 1 also shows that September 2013’s mean extent ranked sixth lowest on record.  You can see from the graph that although a new record minimum was not set in 2013, the negative multi-year trend continued.

 photo Arctic_monthly_sea_ice_extent_201309_zpsf6898e0a.png

Figure 1 – Mean Sea Ice Extent for Septembers: 1979-2013 [NSIDC].

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State of Polar Sea Ice – June 2013: Arctic Sea Ice Decline and Antarctic Sea Ice Gain

Global polar sea ice area in June 2013 remained at or slightly above climatological normal conditions (1979-2008).  This follows early 2013 conditions’ improvement from September 2012′s significant negative deviation from normal conditions (from -2.5 million sq. km. to +500,000 sq. km.).  Early austral fall conditions helped create an abundance of Antarctic sea ice while colder than normal boreal spring conditions helped slow the rate of ice melt in the Arctic.

The NSIDC made a very important change to its dataset in June.  With more than 30 years’ worth of satellite-era data, they recalculated climatological normals to agree with World Meteorological Organization standards.  The new climatological era runs from 1981-2010 (see Figure 5 below).  What impacts did this have on their data?  The means and standard deviations now encompass the time period of fastest Arctic melt.  As a consequence, the 1981-2010 values are much lower than the 1979-2000 values.  This is often one of the most challenging conditions to explain to the public.  “Normal”, scientifically defined, is often different than “normal” as most people refer to it.  U.S. temperature anomalies reported in the past couple of years refer to a similar 1981-2010 “normal period”.  Those anomalies are smaller in value than if they were compared to the previous 1971-2000 “normal period”.  Thus, temperature anomalies don’t seem to increase as much as they would if scientists referred to the same reference period.

Arctic Sea Ice

According to the NSIDC, sea ice melt during June measured 2.10 million sq. km.  This melt rate was slower than normal for the month, but June′s extent remained below average – a condition the ice hasn’t hurdled since this time last year.  Instead of measuring near 11.89 million sq. km., June 2013′s average extent was only 11.5 million sq. km., a 300,000 sq. km. difference.

Barents Sea (Atlantic side) ice remained below its climatological normal value during the month, which continues the trend that began this last winter.  Kara Sea (Atlantic side) ice temporarily recovered from its wintertime low extent and reached normal conditions earlier this year, but fell back below normal during May through June.  Arctic Basin sea ice (surrounding the North Pole) fell below normal during June due to earlier weather conditions that sheared ice apart.  The Bering Sea (Pacific side), which saw ice extent growth due to anomalous northerly winds in 2011-2012, saw similar conditions in December 2012 through March 2013.  Since then, Bering Sea ice extent returned to normal for this time of year: zero.  The previous negative Arctic Oscillation phase gave way to normal conditions throughout June.  However, a stronger than normal Arctic Low set up which kept Arctic weather conditions cooler and stormier than normal.  These conditions prevented Arctic sea ice from melting as quickly in June as it did in 2012.  In the past few days, these conditions eased and rapid Arctic melt is once again underway.  I’ll have more to say about this in next month’s post.

For the first time in a number of years, Arctic sea ice extent in June didn’t reach a bottom-ten status.  June Arctic sea ice extent was “only” the 11th lowest on record.  In terms of climatological trends, Arctic sea ice extent in June decreased by 3.6% per decade.  This rate is closest to zero in the late winter/early spring months and furthest from zero in late summer/early fall months.  Note that this rate also uses 1981-2010 as the climatological normal.  There is no reason to expect this rate to change significantly (much more or less negative) any time soon, but negative rates are likely to slowly become more negative for the foreseeable future.  Additional low ice seasons will continue.  Some years will see less decline than other years (e.g., 2011) – but the multi-decadal trend is clear: negative.  The specific value for any given month during any given year is, of course, influenced by local and temporary weather conditions.  But it has become clearer every year that humans have established a new climatological normal in the Arctic with respect to sea ice.  This new normal will continue to have far-reaching implications on the weather in the mid-latitudes, where most people live.

Arctic Pictures and Graphs

The following graphic is a satellite representation of Arctic ice as of June 13, 2013:

 photo Arctic_sea_ice_20130613_zpsde15c255.png

Figure 1UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20130613.

The following graphic is a satellite representation of Arctic ice as of July 4, 2013:

 photo Arctic_sea_ice_20130704_zps808dd919.png

Figure 2UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20130704.

Continued melt around the Arctic ice periphery is evident in the newest figure.  Hudson Bay ice is nearly gone.  Rapid melt is also evident in the Kara, Barents, and Bering Seas.  Compared to last year at the same time, more ice is present in the Baffin/Newfoundland, Beaufort, and Kara Seas.  This is due to interannual weather and sea variability.  The climate trend remains clear: widespread and rapid sea ice melt is the new normal for the Arctic.

So far, the early season thinning of sea ice near the North Pole hasn’t caused a mid-season mid-ocean collapse of sea ice, as many people feared.  This is not to say that rapid ice melt in the central Arctic Ocean will not happen this year.  We simply have to wait and see what happens before we issue obituaries.

The following graph of Arctic ice volume from the end of June demonstrates the relative decline in ice health with time:

 photo SeaIceVolumeAnomaly_20130630_zps85e7de79.png

Figure 3PIOMAS Arctic sea ice volume time series through June 2013.

As the graph shows, volume (length*width*height) hit another record minimum in June 2013.  Moreover, that volume remained far from normal for the past three years in a clear break from pre-2010 conditions.  Conditions between -1 and -2 standard deviations are somewhat rare and conditions outside the -2 standard deviation threshold (see the line below the shaded area on the graph above) are incredibly rare: the chances of 3 of them occurring in 3 subsequent years under normal conditions are extraordinarily low (you have a better chance of winning the Powerball than this).  Hence my assessment that “normal” conditions in the Arctic shifted from what they were in the past few centuries; humans are creating a new normal for the Arctic.  Note further that the ice volume anomaly returned to near the -1 standard deviation envelope in early 2011, early 2012, and now early 2013.  In each of the previous two years, volume fell rapidly outside of the -2 standard deviation area with the return of summer.  That provides further evidence that natural conditions are not the likely cause; rather, the more likely cause is human influence.

Arctic Sea Ice Extent

Take a look at May’s areal extent time series data:

 photo N_stddev_timeseries_20130704_1_zpsd03c4765.png

Figure 4NSIDC Arctic sea ice extent time series through early July 2013 compared with five recent years’ data, climatological norm (dark gray line) and standard deviation envelope (light gray).

As you can see, this year’s extent (light blue curve)  remained at historically low levels throughout the spring, well below average values (thick gray curve), just as it did in the previous five springs.  Sea ice extent did something different this spring and early summer: the late season surge of ice formation seen in the  2009, 2010, and 2012 curves was not as strong this year; the early summer surge of ice melt seen in the 2010, 2011, and 2012 curves was also not as strong this year, at least not until the last week or so.  This graph also demonstrates that late-season ice formation surges have little effect on ice extent minima recorded in September each year.  The primary reason for this is the lack of ice depth due to previous year ice melt.  I will pay close attention to this time series throughout June to see if this year’s curve follows 2012′s.  Note the sharp decrease in sea ice extent in mid-June 2012.  That helped pave the way for last year’s record low September extent, even though weather conditions were not as a factor as they were during the 2007 record low season.

 photo N_stddev_timeseries_20130704_2_zpsb4d45830.png

Figure 5 – Graph comparing two climatological normal periods: 1979-2000 (light blue solid line with dark gray shaded envelope) and 1981-2010 (purple solid line with light gray shaded envelope).  Also displayed is the Arctic sea ice extent for 2012 (green dashed line) and 2013 (light purple solid line).

This figure demonstrates the effect of adding ten years’ of low sea ice extent data in a data set’s mean and standard deviation values.  The 1981-2010 mean is lower than the 1979-2000 mean for all dates but the difference is greatest near the annual minimum extent in mid-September.  Likewise, the new standard deviation is much larger than the previous standard deviation.  This means that recent variance exceeds variance from the previous period.  This shows graphically what I’ve written about in these posts: the Arctic entered a new normal within the past 10 years.  What awaits us in the future?  For starters, scientists expect that the annual minimum extent will nearly reach zero.  The timing of that condition remains up for debate.  I think it will happen within the next ten years, rather than thirty years as others predict.

Antarctic Pictures and Graphs

Here is a satellite representation of Antarctic sea ice conditions from June 13, 2013:

 photo Antarctic_sea_ice_20130613_zpsbe2cd3c3.png

Figure 6UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20130613.

And here is the corresponding graphic from July 4, 2013:

 photo Antarctic_sea_ice_20130704_zps2529650e.png

Figure 7UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20130704.

Sea ice growth in the past two months is within climatological norms.  However, there is more Antarctic sea ice today than there normally is on this calendar date.  The reason for this is the presence of early-season extra ice in the Weddell Sea (east of the Antarctic Peninsula that juts up toward South America).  This ice existed this past austral (Southern Hemisphere) summer due to an anomalous atmospheric circulation pattern: persistent high pressure west of the Weddell Sea.  This pressure system caused winds that pushed the sea ice north and also moved cold Antarctic air over the Sea, which kept ice melt rate well below normal.  A similar mechanism helped sea ice form in the Bering Sea last winter.  Where did the anomalous winds come from?  We can again point to a climatic relationship.

The difference between the noticeable and significant long-term Arctic ice loss and relative lack of Antarctic ice loss is largely and somewhat confusingly due to the ozone depletion that took place over the southern continent in the 20th century.  This depletion has caused a colder southern polar stratosphere than it otherwise would be.  Why?  Because ozone heats the air around it after it absorbs UV radiation and re-radiates it to its environment.  Will less ozone, there is less stratospheric heating.  This process reinforced the polar vortex over the Antarctic Circle.  This is almost exactly the opposite dynamical condition than exists over the Arctic with the negative phase of the Arctic Oscillation.  The southern polar vortex has helped keep cold, stormy weather in place over Antarctica that might not otherwise would have occurred to the same extent and intensity. The vortex and associated anomalous high pressure centers kept ice and cold air over places such as the Weddell Sea this year.

As the “ozone hole” continues to recover during this century, the effects of global warming will become more clear in this region, especially if ocean warming continues to melt sea-based Antarctic ice from below (subs. req’d).  The strong Antarctic polar vortex will likely weaken back to a more normal state and anomalous high pressure centers that keep ice flowing into the ocean will not form as often.  For now, we should perhaps consider the lack of global warming signal due to lack of ozone as relatively fortunate.  In the next few decades, we will have more than enough to contend with from Greenland ice sheet melt.  Were we to face a melting West Antarctic Ice Sheet at the same time, we would have to allocate many more resources.  Of course, in a few decades, we’re likely to face just such a situation.

Finally, here is the Antarctic sea ice extent time series through early July:

 photo S_stddev_timeseries_20130704_zpsc6c44a01.png

Figure 8NSIDC Antarctic sea ice extent time series through early July 2013.

The 2013 time series continues to track near the top of the +2 standard deviation envelope and above the 2012 time series.  Unlike the Arctic, there is no clear trend toward higher or lower sea ice extent conditions in the Antarctic Ocean.

Policy

Given the lack of climate policy development at a national or international level to date, Arctic conditions will likely continue to deteriorate for the foreseeable future.  This is especially true when you consider that climate effects today are largely due to greenhouse gas concentrations from 30 years ago.  It takes a long time for the additional radiative forcing to make its way through the climate system.  The Arctic Ocean will soak up additional energy (heat) from the Sun due to lack of reflective sea ice each summer.  Additional energy in the climate system creates cascading and nonlinear effects throughout the system.  For instance, excess energy pushes the Arctic Oscillation to a more negative phase, which allows anomalously cold air to pour south over Northern Hemisphere land masses while warm air moves over the Arctic during the winter.  This in turn impacts weather patterns throughout the year across the mid-latitudes and prevents rapid ice growth where we want it.

More worrisome for the long-term is the heat that impacts land-based ice.  As glaciers and ice sheets melt, sea-level rise occurs.  Beyond the increasing rate of sea-level rise due to thermal expansion (excess energy, see above), storms have more water to push onshore as they move along coastlines.  We can continue to react to these developments as we’ve mostly done so far and allocate billions of dollars in relief funds because of all the human infrastructure lining our coasts.  Or we can be proactive, minimize future global effects, and reduce societal costs.  The choice remains ours.

Errata

Here are my State of Polar Sea Ice posts from June and May 2013. For further comparison, here is my State of Polar Sea Ice post from July 2012.


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State of Polar Sea Ice – May 2013: Arctic Sea Ice Decline and Antarctic Sea Ice Gain

Global polar sea ice area in May 2013 remained at or slightly above climatological normal conditions (1979-2009).  This follows early 2013 conditions’ improvement from September 2012′s significant negative deviation from normal conditions (from -2.5 million sq. km. to +500,000 sq. km.).  While Antarctic sea ice gain was slightly more than the climatological normal rate following the austral summer, Arctic sea ice loss was slightly more than normal during the same period.

Arctic Sea Ice

According to the NSIDC, sea ice melt during May measured 1.12 million sq. km.  This melt rate was slower than normal for the month, but May′s extent remained below average – a condition the ice hasn’t hurdled since this time last year.  Instead of measuring near 13.6 million sq. km., May 2013′s average extent was only 13.1 million sq. km., a 500,000 sq. km. difference.  In terms of annual maximum values, 2013′s 15.13 million sq. km. was 733,000 lower than normal.

Barents Sea (Atlantic side) ice once again fell from its climatological normal value during the month after remaining low during most of the winter.  Kara Sea (Atlantic side) ice temporarily recovered from its wintertime low extent and reached normal conditions earlier this year, but fell back below normal during May.  The Bering Sea (Pacific side), which saw ice extent growth due to anomalous northerly winds in 2011-2012, saw similar conditions in December 2012 through March 2013.  As it did previously this winter, an extended negative phase of the Arctic Oscillation allowed cold Arctic air to move far southward and brought warmer than normal air to move north over parts of the Arctic.  The AO’s tendency toward its negative phase in recent winters relates to the lack of sea ice over the Arctic Ocean in September each fall.  Warmer air slows the growth of ice, especially ice thickness.  This slow growth allows more melt than normal during the subsequent summer, which helps establish and maintain negative AO phases.  This is a destructive annual cycle for Arctic sea ice.

In terms of climatological trends, Arctic sea ice extent in May has decreased by 2.24% per decade.  This rate is closest to zero in the late winter/early spring months and furthest from zero in late summer/early fall months.  Note that this rate also uses 1979-2000 as the climatological normal.  There is no reason to expect this rate to change significantly (much more or less negative) any time soon, but negative rates are likely to slowly become more negative for the foreseeable future.  Additional low ice seasons will continue.  Some years will see less decline than other years (e.g., 2011) – but the multi-decadal trend is clear: negative.  The specific value for any given month during any given year is, of course, influenced by local and temporary weather conditions.  But it has become clearer every year that humans have established a new climatological normal in the Arctic with respect to sea ice.  This new normal will continue to have far-reaching implications on the weather in the mid-latitudes, where most people live.

Arctic Pictures and Graphs

The following graphic is a satellite representation of Arctic ice as of May 10, 2013: photo Arctic_sea_ice_20130510_zps95770d27.png

Figure 1UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20130324.

Here is the similar image from June 13, 2013:

 photo Arctic_sea_ice_20130613_zpsde15c255.png

Figure 2UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20130510.

The early season melt is evident in the Sea of Okhotsk, the Bering Sea,  the Baffin/Newfoundland Bay area, the Barents Sea, and the Kara Sea.  Ice finished forming in these regions at the latest point in the winter.  As such, sea ice is the thinnest there and most susceptible to weather and solar heating.  Weather and ocean currents are also able to transport this ice around and out of the Arctic, as this animation demonstrates.  Currents will continue to transport sea ice out of the Arctic, after which the ice melts at lower latitudes.

The recent lack of sea ice thickness near the North Pole is also troubling.  This is a result of weather conditions from late May through early June that were able to easily push thin sea ice around; this has not been seen before this year.  As I mentioned in my two previous series posts, we do not yet know what effect early season anomalies such as vast ice cracks or thinning sea ice might have on end-of-season sea ice extent.  We are literally charting new history with these events, which means we have more theories than answers.

The following graph of Arctic ice volume from the end of May demonstrates the relative decline in ice health with time:

 photo SeaIceVolumeAnomaly_20130531_zps051f50ce.png

Figure 3PIOMAS Arctic sea ice volume time series through May 2013.

As the graph shows, volume (length*width*height) hit another record minimum in June 2012.  Moreover, the volume remained far from normal for the past three years in a clear break from pre-2010 conditions.  Conditions between -1 and -2 standard deviations are somewhat rare and conditions outside the -2 standard deviation threshold (see the line below the shaded area on the graph above) are incredibly rare: the chances of 3 of them occurring in 3 subsequent years under normal conditions are extraordinarily low (you have a better chance of winning the Powerball than this).  Hence my assessment that “normal” conditions in the Arctic shifted from what they were in the past few centuries; humans are creating a new normal for the Arctic.  Note further that the ice volume anomaly returned to near the -1 standard deviation envelope in early 2011, early 2012, and now early 2013.  In each of the previous two years, volume fell rapidly outside of the -2 standard deviation area with the return of summer.  That provides further evidence that natural conditions are not the likely cause; rather, the more likely cause is human influence.

Arctic Sea Ice Extent

Take a look at May’s areal extent time series data:

 photo N_stddev_timeseries_20130613_2_zpse5413c25.png

Figure 4NSIDC Arctic sea ice extent time series through early June 2013 compared with four other low years’ data, climatological norm (dark gray line) and standard deviation envelope (light gray).

As you can see, this year’s extent (light blue curve)  remained at historically low levels throughout the winter, well below average values (thick gray curve), just as it did in the previous four winters.  Sea ice extent did something different this spring: the late season surge of ice formation seen in the  2009, 2010, and 2012 curves was not as strong this year.  This graph also demonstrates that late-season ice formation surges have little effect on ice extent minima recorded in September each year.  The primary reason for this is the lack of ice depth due to previous year ice melt.  I will pay close attention to this time series throughout June to see if this year’s curve follows 2012’s.  Note the sharp decrease in sea ice extent in mid-June 2012.  That helped pave the way for last year’s record low September extent, even though weather conditions were not as a factor as they were during the 2007 record low season.

Antarctic Pictures and Graphs

Here is a satellite representation of Antarctic sea ice conditions from May 10, 2013:

 photo Antarctic_sea_ice_20130510_zps3bc7c6af.png

Figure 5UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20130510.

And here is the corresponding graphic from June 13, 2013:

 photo Antarctic_sea_ice_20130613_zpsbe2cd3c3.png

Figure 6UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20130613.

Sea ice growth in the past two months is within climatological norms.  However, there is more Antarctic sea ice today than there normally is on this calendar date.  The reason for this is the presence of early-season extra ice in the Weddell Sea (east of the Antarctic Peninsula that juts up toward South America).  This ice existed this past austral (Southern Hemisphere) summer due to an anomalous atmospheric circulation pattern: persistent high pressure west of the Weddell Sea.  This pressure system caused winds that pushed the sea ice north and also moved cold Antarctic air over the Sea, which kept ice melt rate well below normal.  A similar mechanism helped sea ice form in the Bering Sea last winter.  Where did the anomalous winds come from?  We can again point to a climatic relationship.

The difference between the noticeable and significant long-term Arctic ice loss and relative lack of Antarctic ice loss is largely and somewhat confusingly due to the ozone depletion that took place over the southern continent in the 20th century.  This depletion has caused a colder southern polar stratosphere than it otherwise would be.  Why?  Because ozone heats the air around it after it absorbs UV radiation and re-radiates it to its environment.  Will less ozone, there is less stratospheric heating.  This process reinforced the polar vortex over the Antarctic Circle.  This is almost exactly the opposite dynamical condition than exists over the Arctic with the negative phase of the Arctic Oscillation.  The southern polar vortex has helped keep cold, stormy weather in place over Antarctica that might not otherwise would have occurred to the same extent and intensity. The vortex and associated anomalous high pressure centers kept ice and cold air over places such as the Weddell Sea this year.

As the “ozone hole” continues to recover during this century, the effects of global warming will become more clear in this region, especially if ocean warming continues to melt sea-based Antarctic ice from below (subs. req’d).  The strong Antarctic polar vortex will likely weaken back to a more normal state and anomalous high pressure centers that keep ice flowing into the ocean will not form as often.  For now, we should perhaps consider the lack of global warming signal due to lack of ozone as relatively fortunate.  In the next few decades, we will have more than enough to contend with from Greenland ice sheet melt.  Were we to face a melting West Antarctic Ice Sheet at the same time, we would have to allocate many more resources.  Of course, in a few decades, we’re likely to face just such a situation.

Finally, here is the Antarctic sea ice extent time series through early June:

 photo S_stddev_timeseries_20130613_zpsaf473dbf.png

Figure 7NSIDC Antarctic sea ice extent time series through early June 2013.

The 2013 time series continues to track near the top of the +2 standard deviation envelope and above the 2012 time series.  Unlike the Arctic, there is no clear trend toward higher or lower sea ice extent conditions in the Antarctic Ocean.

Policy

Given the lack of climate policy development at a national or international level to date, Arctic conditions will likely continue to deteriorate for the foreseeable future.  This is especially true when you consider that climate effects today are largely due to greenhouse gas concentrations from 30 year ago.  It takes a long time for the additional radiative forcing to make its way through the climate system.  The Arctic Ocean will soak up additional energy (heat) from the Sun due to lack of reflective sea ice each summer.  Additional energy in the climate system creates cascading and nonlinear effects throughout the system.  For instance, excess energy pushes the Arctic Oscillation to a more negative phase, which allows anomalously cold air to pour south over Northern Hemisphere land masses while warm air moves over the Arctic during the winter.  This in turn impacts weather patterns throughout the year across the mid-latitudes and prevents rapid ice growth where we want it.

More worrisome for the long-term is the heat that impacts land-based ice.  As glaciers and ice sheets melt, sea-level rise occurs.  Beyond the increasing rate of sea-level rise due to thermal expansion (excess energy, see above), storms have more water to push onshore as they move along coastlines.  We can continue to react to these developments as we’ve mostly done so far and allocate billions of dollars in relief funds because of all the human infrastructure lining our coasts.  Or we can be proactive, minimize future global effects, and reduce societal costs.  The choice remains ours.

Errata

Here are my State of Polar Sea Ice posts from May and March 2013. For further comparison, here is my State of Polar Sea Ice post from May 2012.

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