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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.


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.


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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May 2013 CO2 Concentrations: 399.89 ppm

During May 2013, the Scripps Institution of Oceanography measured an average of 399.89 ppm CO2 concentration at their Mauna Loa, Hawai’i Observatory.

This value is important.  Why?  Because not only is 399.89 ppm the largest CO2 concentration value for any May in recorded history, it is the largest CO2 concentration value in any calendar month in recorded history.  More on that below.  This year’s May  value is 3.02 ppm higher than May 2012′s!  Month-to-month differences typically range between 1 and 2 ppm.  This jump is clearly well outside of that range.  This is more in line with February’s year-over-year change of 3.37 ppm.  The unending trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.

Let’s get back to that all-time high concentration value.  The yearly maximum monthly value normally occurs during May. Last year was no different: the 396.78ppm concentration in May 2012 was the highest value reported last year and, prior to the last four months, in recorded history (neglecting proxy data).  I expected May of this year to produce another all-time record value and it clearly did that.  May 2013’s value will hold onto first place until February 2014.  I wrote the following three months ago:

If we extrapolate last year’s maximum value out in time, it will only be 2 years until Scripps reports 400 ppm average concentration for a singular month (likely May 2014; I expect May 2013′s value will be ~398ppm).  Note that I previously wrote that this wouldn’t occur until 2015 – this means CO2 concentrations are another climate variable that is increasing faster than experts predicted just a short couple of years ago.

For the past few months, I stood by that prediction.  But actual concentration increases proved me slightly wrong.  Here is why: the difference in CO2 concentration values between May 2012 and March 2012 was 2.33 ppm (396.78 – 394.45).  If we do the simplest thing and add that same difference to March 2013’s value, we get 399.67 ppm.  That is awfully close to 400 ppm, but less than the 399.93 ppm extrapolation I first performed in February, which ended up being a perfect projection.  It’s also close to the 399.3 ppm extrapolation I calculated in March.  I discussed May 2013′s projection with Sourabh after February’s post.  They predicted 399.5-400 ppm concentration for May 2013.  I predicted NOAA would measure May 2013′s mean concentration near 399.3 ppm, but it turns out Sourabh was closer than I was to the actual value.

 photo co2_widget_brundtland_600_graph_201305_zpsfad83dd1.gif

Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in May from 1958 through 2013. added the `350s` and `400s` to the past two month’s graphics.  I suppose they’re meant to imply concentrations shattered 350 ppm back in the 1980s and are pushing up against 400 ppm now in the 2010s.

How do concentration measurements change in calendar years?  The following two graphs demonstrate this.

 photo CO2_concentration_5y_trend_NOAA_201306_zps66f17f18.png

Figure 2 – Monthly CO2 concentration values (red) from 2009 through 2013 (NOAA).  Monthly CO2 concentration values with seasonal cycle removed (black).  Note the yearly minimum observation occurred seven months ago the yearly maximum value occurred last month.  CO2 concentrations will decrease throughout the rest of 2013, as they do every year after May.

 photo CO2_concentration_50y_trend_NOAA_201306_zps5ba37b14.png

Figure 3 – 50 year time series of CO2 concentrations at Mauna Loa Observatory.  The red curve represents the seasonal cycle based on monthly average values.  The black curve represents the data with the seasonal cycle removed to show the long-term trend.  This graph shows the recent and ongoing increase in CO2 concentrations.  Remember that as a greenhouse gas, CO2 increases the radiative forcing of the Earth, which increases the amount of energy in our climate system.

CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming.  Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere.  Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries.  Human systems do not yet exist that remove CO2 from any medium (air or water).  They are not likely to exist for some time.  So NOAA will extend the right side of the above graphs for years and decades to come.

This month, I want to spend some time on this post’s focus: CO2 concentration values.  Given our species penchant for round numbers, it came as little surprise that the corporate media placed an uncommon amount of attention on a value that has relatively low meaning: daily CO2 concentrations at Mauna Loa surpassed 400 ppm for a day during the month of May.  In fact, both the media and many climate activists made a very big deal about this development.  I think that was largely a waste of time.  Again, the daily value itself didn’t represent any large difference once reached.  The climate system did not automatically kick into a different setting once concentrations passed 400 ppm for a day.  Nothing substantially new occurred that didn’t when concentration were “only” 399 ppm (or 390 ppm or 380 ppm for that matter).

As I state in this series every month, the trend makes much more of a difference than any daily, monthly, or even yearly average value.  And that trend is accelerating upwards at a rate that many didn’t think was possible even 10 years ago.  The effects from last year’s average CO2 concentrations won’t manifest in realizable terms until 30-50 years from now.  I didn’t see anybody pointing out that important detail.  Similarly, I didn’t see any explanation that today’s mean temperatures are largely a result of CO2 concentrations from 30+ years ago.  Perhaps most importantly, climate activists didn’t mention that CO2 concentrations are rising at a rising rate despite decades of their activism.  That fact creates a rather uncomfortable situation because most activists are proponents of doing tomorrow what they did yesterday.  If those actions haven’t had any effect up until now, why the advocacy for the status quo when those same activists try to claim that the status quo is untenable.  If they really believed in their catastrophic climate change claims, shouldn’t they honestly evaluate the effects their actions have had?  And if those actions produced far less meaningful progress than they state is absolutely required for the survival of our species and the planet (grandiose language, I know), why do their strategies and tactics remain largely unchanged?

I write these posts for people who are curious or interested in the state of a key climate variable.  I realized that doomsday language turns a significant portion of my potential audience off from the get-go.  If we are to do something meaningful about climate change, we cannot afford the disengagement and hostility of one-third or more of our fellow global citizens towards climate activism.  I don’t want to simply treat people as empty vessels into which I can pour knowledge.  I want to engage them on ground that is similar between us precisely because I want to do something.  Screaming about 400 ppm mean CO2 concentration for one day and then walking away from the variable until we pass the next perceived meaningful threshold doesn’t strike me as engagement.

The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will.  It depends primarily on the rate at which we emit CO2 into the atmosphere.  We can choose 400 ppm or 450 ppm or almost any other target (350 ppm seems out of reach within the next couple hundred years).  That choice is dependent on the type of policies we decide to implement.  It is our current policy to burn fossil fuels because we think doing so is cheap, although current practices are massively inefficient and done without proper market signals.  We will widely deploy clean sources of energy when they are cheap, the timing of which we control.  We will remove CO2 from the atmosphere if we have cheap and effective technologies and mechanisms to do so, which we also control to some degree.  These future trends depend on today’s innovation and investment in research, development, and deployment.  Today’s carbon markets are not the correct mechanism, as they are aptly demonstrating.  The bottom line is: We will limit future warming and climate effects when we choose to do so.

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Denver’s May 2013 Climate Summary


During the month of May 2013, Denver, CO’s (link updated monthly) temperatures were 0.8°F above normal (57.9°F vs. 57.1°F).  The maximum temperature of 88°F was recorded on the 17th while the minimum temperature of 19°F was recorded on the 2nd.  Here is the time series of Denver temperatures in May 2013:

 photo Denver_Temps_201305_zpsacd74199.png

Figure 1. Time series of temperature at Denver, CO during May 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

In comparison to March and April 2013, May 2013 brought much less extreme weather to the Denver area.   After a cold start to the month, there was a general regime change that allowed high pressure to dominate in the middle and at the end of the month.  This high pressure brought warmer than average temperatures, which offset the early month cold snap.


Precipitation was lighter than normal during May 2013: only 0.82″ precipitation fell at Denver during the month instead of the normal 2.12″.  Precipitation is a highly variable quantity though.  The west side of the Denver Metro area received higher than normal precipitation during the same time period.

Precipitation in the past couple of months alleviated some of the worst drought conditions in northern Colorado.  The link goes to a late April 2013 post; further relief occurred in May with regular rain events.  All of Colorado continues under at least some measure of drought in early June 2013.  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however.

Interannual Variability

I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.