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NASA & NOAA: April 2014 Warmest Globally On Record

According to data released by NASA and NOAA this month, April was the warmest April globally on record.  Here are the data for NASA’s analysis; here are NOAA data and report.  The two agencies have different analysis techniques, which in this case resulted in slightly different temperature anomaly values but the same overall rankings within their respective data sets.  The analyses result in different rankings in most months.  The two techniques do provide a check on one another and confidence for us that their results are robust.  At the beginning, I will remind readers that the month-to-month and year-to-year values and rankings matter less than the long-term climatic warming.  Weather is the dominant factor for monthly and yearly conditions, not climate.

The details:

April’s global average temperature was 0.73°C (1.314°F) above normal (14°C; 1951-1980), according to NASA, as the following graphic shows.  The past three months have a +0.63°C temperature anomaly.  And the latest 12-month period (May 2013 – Apr 2014) had a +0.62°C temperature anomaly.  The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index.  The 2010-2012 downturn was largely due to the last La Niña event (see below for more).  Since then, ENSO conditions returned to a neutral state (neither La Niña nor El Niño).  As previous anomalously cool months fell off the back of the running mean, the 12-month temperature trace tracked upward again throughout 2013 and 2014.

 photo NASA-Temp_Analysis_20140430_zps82150da6.gif

Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through April 2014 from NASA.

According to NOAA, April’s global average temperatures were +0.77°C (1.386°F) above the 20th century average of 13.7°C (56.7°F).  NOAA’s global temperature anomaly map for April (duplicated below) shows where conditions were warmer and cooler than average during the month.

 photo NOAA-Temp_Analysis_201404_zps92d3f6cb.gif

Figure 2. Global temperature anomaly map for August 2013 from NOAA.

The two different analyses’ importance is also shown by the preceding two figures.  Despite differences in specific global temperature anomalies, both analyses picked up on the same spatial temperature patterns and their relative strength.

Influence of ENSO

 photo NinoSSTAnom20140501_zpsc925f282.gif

Figure 3. Time series of weekly SST data from NCEP (NOAA).  The highest interest region for El Niño/La Niña is `NINO 3.4` (2nd time series from top).

There has been neither El Niño nor La Niña in the past couple of years.  This ENSO-neutral phase is common.  As you can see in the NINO 3.4 time series (2nd from top in Figure 3), Pacific sea surface temperatures were relatively cool in January through March, then quickly warmed.  This switch occurred because normal easterly winds (blowing toward the west) across the equatorial Pacific relaxed and two significant westerly wind bursts occurred in the western Pacific.  These anomalous winds generated an eastward moving Kelvin wave, which causes downwelling and surface mass convergence.  Warm SSTs collect along the equator as a result.  These Kelvin waves eventually crossed the entire Pacific Ocean, as Figure 4 shows.

 photo PacifcOcEqTAnomaly20140523_zpsff7554f1.gif

Figure 4.  Sub-surface Pacific Ocean temperature anomalies from Jan-Apr 2014.  Anomalously cool eastern Pacific Ocean temperatures in January gave way to anomalously warm temperatures by April.  Temperatures between 80W and 100W warmed further since April 14.

The Climate Prediction Center announced an El Niño Watch earlier this year.  The most recent update says the chances of an El Niño during the rest of 2014 exceeds 65%.  There is no reliable prediction of the potential El Niño’s strength at this time.  Without another westerly wind burst, an El Niño will likely not be very strong.  Even moderate strength El Niños impact global weather patterns.

An important detail is whether the potential 2014 El Niño will be an Eastern or Central Pacific El Niño (see figure below).  Professor Jin-Yi Yu, along with colleagues, first proposed the difference in a 2009 Journal of Climate paper.  More recently, Yu’s work suggested a recent trend toward Central Pacific El Niños influenced the frequency and intensity of recent U.S. droughts.  This type of El Niño doesn’t cause global record temperatures, but still impacts atmospheric circulations and the jet stream, which impacts which areas receive more or less rain.  If the potential 2014 El Niño is an Eastern Pacific type, we can expect monthly global mean temperatures to spike and the usual precipitation anomalies commonly attributed to El Niño.

 photo EastvsCentralPacificENSOschematic_zps08856e81.jpg

Figure 5. Schematic of Central-Pacific ENSO versus Eastern-Pacific ENSO as envisioned by Dr. Jin-Yi Yu at the University of California – Irvine.

If an El Niño does occur later in 2014, it will mask some of the deep ocean heat absorption by releasing energy back to the atmosphere.  If that happens, the second half of 2014 and the first half of 2015 will likely set global surface temperature records.  2014, 2015, or both could set the all-time global mean temperature record (currently held by 2010).  Some scientists recently postulated that an El Niño could also trigger a shift from the current negative phase of the Interdecadal Pacific Oscillation (IPO; or PDO for just the northern hemisphere) to a new positive phase.  This would be similar in nature, though different in detail, as the shift from La Niña or neutral conditions to El Niño.  If this happens, the likelihood of record hot years would increase.  I personally do not believe this El Niño will shift the IPO phase.  I don’t think this El Niño will be strong enough and I don’t think the IPO is in a conducive state for a switch to occur.

The “Hiatus”

Skeptics have pointed out that warming has “stopped” or “slowed considerably” in recent years, which they hope will introduce confusion to the public on this topic.  What is likely going on is quite different: since an energy imbalance exists (less energy is leaving the Earth than the Earth is receiving; this is due to atmospheric greenhouse gases) and the surface temperature rise has seemingly stalled, the excess energy is going somewhere.  The heat has to go somewhere – energy doesn’t just disappear.  That somewhere is likely the oceans, and specifically the deep ocean (see figure below).  Before we all cheer about this (since few people want surface temperatures to continue to rise quickly), consider the implications.  If you add heat to a material, it expands.  The ocean is no different; sea-levels are rising in part because of heat added to it in the past.  The heat that has entered in recent years won’t manifest as sea-level rise for some time, but it will happen.  Moreover, when the heated ocean comes back up to the surface, that heat will then be released to the atmosphere, which will raise surface temperatures as well as introduce additional water vapor due to the warmer atmosphere.  Thus, the immediate warming rate might have slowed down, but we have locked in future warming (higher future warming rate).

 photo Ocean_heat_content_balmaseda_et_al_zps23184297.jpg

Figure 6. Recent research shows anomalous ocean heat energy locations since the late 1950s.  The purple lines in the graph show how the heat content of the whole ocean has changed over the past five decades. The blue lines represent only the top 700 m and the grey lines are just the top 300 m.  Source: Balmaseda et al., (2013)

You can see in Figure 6 that the upper 300m of the world’s oceans accumulated less heat during the 2000s (5*10^22 J) than during the 1990s.  In contrast, accumulated heat greatly increased in ocean waters between 300m and 700m during the 2000s (>10*10^22 J).  We cannot and do not observe the deep ocean with great frequency.  We do know from frequent and reliable observations that the sea surface and relatively shallow ocean did not absorb most of the heat in the past decade.  We also know how much energy came to and left the Earth from satellite observations.  If we know how much energy came in, how much left, and how much the land surface and shallow ocean absorbed, it is a relatively straightforward computation to determine how much energy likely remains in the deep ocean.

Discussion

The fact that April 2014 was the warmest on record despite a negative IPO and a neutral ENSO is eye-opening.  I think it highlights the fact that there is an even lower frequency signal underlying the IPO, ENSO, and April weather: anthropogenic warming.  That signal is not oscillatory, it is increasing at an increasing rate and will continue to do so for decades to centuries.  The length of time that occurs and its eventual magnitude is dependent on our policies and activities.  We continue to emit GHGs at or above the high-end of the range simulated by climate models.  Growth in fossil fuel use at the global scale continues.  This growth dwarfs any effect of a switch to energy sources with lower GHG emissions.  I don’t think that will change during the next 15 years, which would lock us into the warmer climate projections through most of the rest of the 21st century.  The primary reason for this is the scale of humankind’s energy infrastructure.  Switching from fossil fuels to renewable energy will take decades.  Acknowledging this isn’t defeatist or pessimistic; it is I think critical in order to identify appropriate opportunities and implement the type and scale of policy responses to encourage that switch.


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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].

Continue reading


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NASA & NOAA: August 2013 4th Warmest Globally On Record

According to data released by NASA and NOAA this month, August was the 4th warmest August globally on record.  Here are the data for NASA’s analysis; here are NOAA data and report.  The two agencies have different analysis techniques, which in this case resulted in different temperature anomaly values but the same overall rankings within their respective data sets.  The analyses result in different rankings in most months.  The two techniques do provide a check on one another and confidence for us that their results are robust.  At the beginning, I will remind readers that the month-to-month and year-to-year values and rankings matter less than the long-term climatic warming.  Monthly and yearly conditions changes primarily by the weather, which is not climate.

The details:

August’s global average temperature was 0.62°C (1.12°F) above normal (1951-1980), according to NASA, as the following graphic shows.  The past three months have a +0.58°C temperature anomaly.  And the latest 12-month period (Aug 2012 – Jul 2013) had a +0.59°C temperature anomaly.  The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index.  The 2010-2012 downturn was largely due to the latest La Niña event (see below for more) that ended early last summer.  Since then, ENSO conditions returned to a neutral state (neither La Niña nor El Niño).  Therefore, as previous anomalously cool months fall off the back of the running mean, and barring another La Niña, the 12-month temperature trace should track upward again throughout 2013.

 photo NASA-Temp_Analysis_20130831_zps3ff2a250.gif

Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through August 2013 from NASA.

According to NOAA, April’s global average temperatures were 0.62°C (1.12°F) above the 20th century average of 15.6°C (60.1°F).  NOAA’s global temperature anomaly map for August (duplicated below) shows where conditions were warmer and cooler than average during the month.

 photo NOAA-Temp_Analysis_201308_zpsf2f24a41.gif

Figure 2. Global temperature anomaly map for August 2013 from NOAA.

The two different analyses’ importance is also shown by the preceding two figures.  Despite differences in specific global temperature anomalies, both analyses picked up on the same temperature patterns and their relative strength.

 photo NinoSSTAnom20130924_zps74ba969c.gif

Figure 3. Time series of weekly SST data from NCEP (NOAA).  The highest interest region for El Niño/La Niña is NINO 3.4 (2nd time series from top).

The last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012.  Since then, tropical Pacific sea-surface temperatures peaked at +0.8 (y-axis) in September 2012.  You can see the effect on global temperatures that the last La Niña had via this NASA time series.  Both the sea surface temperature and land surface temperature time series decreased from 2010 (when the globe reached record warmth) to 2012.  Recent ENSO events occurred at the same time that the Interdecadal Pacific Oscillation entered its most recent negative phase.  This phase acts like a La Niña, but its influence is smaller than La Niña.  So natural, low-frequency climate oscillations affect the globe’s temperatures.  Underlying these oscillations is the background warming caused by humans, which we detect by looking at long-term anomalies.  Despite these recent cooling influences, temperatures were still top-10 warmest for a calendar year (2012) and during individual months, including August 2013.

Skeptics have pointed out that warming has “stopped” or “slowed considerably” in recent years, which they hope will introduce confusion to the public on this topic.  What is likely going on is quite different: since an energy imbalance exists (less energy is leaving the Earth than the Earth is receiving; this is due to atmospheric greenhouse gases) and the surface temperature rise has seemingly stalled, the excess energy is going somewhere.  The heat has to be going somewhere – energy doesn’t just disappear.  That somewhere is likely the oceans, and specifically the deep ocean (see figure below).  Before we all cheer about this (since few people want surface temperatures to continue to rise quickly), consider the implications.  If you add heat to a material, it expands.  The ocean is no different; sea-levels are rising in part because of heat added to it in the past.  The heat that has entered in recent years won’t manifest as sea-level rise for some time, but it will happen.  Moreover, when the heated ocean comes back up to the surface, that heat will then be released to the atmosphere, which will raise surface temperatures as well as introduce additional water vapor due to the warmer atmosphere.  Thus, the immediate warming rate might have slowed down, but we have locked in future warming (higher future warming rate).

 photo Ocean_heat_content_balmaseda_et_al_zps23184297.jpg

Figure 4. New research that shows anomalous ocean heat energy locations since the late 1950s.  The purple lines in the graph show how the heat content of the whole ocean has changed over the past five decades. The blue lines represent only the top 700 m and the grey lines are just the top 300 m.  Source: Balmaseda et al., (2013)

Paying for recovery from seemingly localized severe weather and climate events is and always will be more expensive than paying to increase resilience from those events.  As drought continues to impact the US, as Arctic ice continues its long-term melt, as storms come ashore and impacts communities that are not prepared for today’s high-risk events (due mostly to poor zoning and destruction of natural protections), economic costs will accumulate in this and in future decades.  It is up to us how many costs we subject ourselves to.  As President Obama begins his second term with climate change “a priority”, he tosses aside the most effective tool available and most recommended by economists: a carbon tax.  Every other policy tool will be less effective than a Pigouvian tax at minimizing the actions that cause future economic harm.  It is up to the citizens of this country, and others, to take the lead on this topic.  We have to demand common sense actions that will actually make a difference.

But be forewarned: even if we take action today, we will still see more warmest-ever La Niña years, more warmest-ever El Niño years, more drought, higher sea levels, increased ocean acidification, more plant stress, and more ecosystem stress.  The biggest difference between efforts in the 1980s and 1990s to scrub sulfur and CFC emissions and future efforts to reduce CO2 emissions is this: the first two yielded an almost immediate result.  It will take decades to centuries before CO2 emission reductions produce tangible results humans can see.  That is part of what makes climate change such a wicked problem.


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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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NASA & NOAA: April 2013 13th Warmest Globally On Record

According to data released by NASA and NOAA last week, April was the 13th warmest April globally on record.  Here are the data for  NASA’s analysis; here are NOAA data and report.  The two agencies have slightly different analysis techniques, which in this case resulted in different temperature anomaly values but the same overall rankings.  Most months, the analyses result in different rankings.  The two techniques do provide a check on one another and confidence for us that their results are robust.

The details:

April’s global average temperatures were 0.50°C (0.9°F) above normal (1951-1980), according to NASA, as the following graphic shows.  The past three months have a +0.53°C temperature anomaly.  And the latest 12-month period (Apr 2012 – Mar 2013) had a +0.59°C temperature anomaly.  The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index.  The 2010-2012 downturn was largely due to the latest La Niña event (see below for more) that ended early last summer.  Since then, ENSO conditions returned to a neutral state (neither La Niña nor El Niñ0).  Therefore, as previous anomalously cool months fall off the back of the running mean, and barring another La Niña, the 12-month temperature trace should track upward again throughout 2013.

 photo NASA-Temp_Analysis_20130430_zpsd93c9d48.gif

Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through April 2013 from NASA.

According to NOAA, April’s global average temperatures were 0.52°C (0.94°F) above the 20th century mean of 13.7°C (56.7°F).  NOAA’s global temperature anomaly map for April (duplicated below) shows where conditions were warmer and cooler than average during the month.

 photo NOAA-Temp_Analysis_201304_zps204a8f35.gif

Figure 2. Global temperature anomaly map for January 2013 from NOAA.

The two different analyses’ importance is also shown by the preceding two figures.  Despite differences in specific global temperature anomalies, both analyses picked up on the same temperature patterns and their relative strength.

Both analyses show much cooler than normal conditions over most of North America, Europe, and northeast Asia.  As I’ve discussed elsewhere, this is in response to the abnormal jet stream.  Large, unmoving high pressure centers blocked the jet stream at different locations in the Northern Hemisphere multiple times this winter and spring.  The jet stream therefore assumed a high amplitude pattern where the trough and ridge axes were tens of degrees of latitude apart from one another.  When this happens, very cold air is pulled southward and warm air is pulled northward (look at central Eurasia).  In April 2013, the specific position of the high pressure centers caused cold air to spill southward over land as opposed to over the oceans.  These cold air outbreaks were an advantage for the US in that severe storms were unable to form.  This situation obviously broke down in the past couple of weeks and we have correspondingly seen devastating severe weather outbreaks across the south-central US.

During the second half of last year, a ENSO-neutral state (neither El Niño nor La Niña) began, which continues to this day:

 photo NinoSSTAnom20130501_zpsf742a7c0.gif

Figure 3. Time series of weekly SST data from NCEP (NOAA).  The highest interest region for El Niño/La Niña is NINO 3.4 (2nd time series from top).

The last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012.  Since then, tropical Pacific sea-surface temperatures peaked at +0.8 (y-axis) in September 2012.  You can see the effect on global temperatures that the last La Niña had via this NASA time series.  Both the sea surface temperature and land surface temperature time series decreased from 2010 (when the globe reached record warmth) to 2012.  So a natural, low-frequency climate oscillation affected the globe’s temperatures during the past couple of years.  Underlying that oscillation is the background warming caused by humans.  And yet temperatures were still in the top-10 warmest for a calendar year (2012) and individual months, including through March 2013, in recorded history.  We ascribe a certain status to top-10 events.  April 2013 obviously missed the top-10 threshold, but it remains close to that level of anomalous warmth.  However, the difference in temperature magnitude between the 10th and 13th warmest Aprils is measured in tenths of a degree.

Skeptics have pointed out that warming has “stopped” or “slowed considerably” in recent years, which they hope will introduce confusion to the public on this topic.  What is likely going on is quite different: since an energy imbalance exists (less outgoing energy than incoming energy due to atmospheric greenhouse gases) and the surface temperature rise has seemingly stalled, the excess energy is going somewhere.  That somewhere is likely the oceans, and specifically the deep ocean (see figure below).  Before we all cheer about this (since few people want surface temperatures to continue to rise quickly), consider the implications.  If you add heat to a material, it expands.  The ocean is no different; sea-levels are rising in part because of heat added to it in the past.  The heat that has entered in recent years won’t manifest as sea-level rise for some time, but it will happen.  Moreover, when the heated ocean comes back up to the surface, that heat will then be released to the atmosphere, which will raise surface temperatures as well as introduce additional water vapor due to the warmer atmosphere.  Thus, the immediate warming rate might have slowed down, but we have locked in future warming (higher future warming rate).

 photo Ocean_heat_content_balmaseda_et_al_zps23184297.jpg

Figure 4. New research that shows anomalous ocean heat energy locations since the late 1950s.  The purple lines in the graph show how the heat content of the whole ocean has changed over the past five decades. The blue lines represent only the top 700 m and the grey lines are just the top 300 m.  Source: Balmaseda et al., (2013)

Paying for recovery from seemingly localized severe weather and climate events is and always will be more expensive than paying to increase resilience from those events.  As drought continues to impact US agriculture, as Arctic ice continues to melt to new record lows, as storms come ashore and impacts communities that are not prepared for today’s high-risk events (due mostly to poor zoning and destruction of natural protections), economic costs will accumulate in this and in future decades.  It is up to us how many costs we subject ourselves to.  As President Obama begins his second term with climate change “a priority”, he tosses aside the most effective tool available and most recommended by economists: a carbon tax.  Every other policy tool will be less effective than a Pigouvian tax at minimizing the actions that cause future economic harm.  It is up to the citizens of this country, and others, to take the lead on this topic.  We have to demand common sense actions that will actually make a difference.  But be forewarned: even if we take action today, we will still see more warmest-ever La Niña years, more warmest-ever El Niño years, more drought, higher sea levels, increased ocean acidification, more plant stress, and more ecosystem stress.  The biggest difference between efforts in the 1980s and 1990s to scrub sulfur and CFC emissions and future efforts to reduce CO2 emissions is this: the first two yielded an almost immediate result while it will take decades to centuries before CO2 emission reductions produce tangible results humans can see.  That is part of what makes climate change such a wicked problem.


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

Global polar sea ice area in April 2013 tracked back to climatological normal conditions (1979-2009) from the temporary surplus the previous two months.  This follows January and February’s improvement from September 2012′s significant negative deviation from normal conditions (from -2.5 million sq. km. to +750,000 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 creation during April measured 1.5 million sq. km.  This melt rate was approximately normal for the month, so April′s extent remained below average again.  Instead of measuring near 15 million sq. km., April 2013′s average extent was only 14.37 million sq. km., a 630,000 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, which is also different from spring 2012′s conditions, before 2013 melt caused the extent to fall below normal conditions again.  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 February 2013.  This caused anomalously high ice extent in the Bering Sea again this winter.  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 is related 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 April has decreased by 2.3% per decade, the lowest of any calendar month.  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 increasingly negative rates are likely in 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.

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4th Daily April Record Low in Denver & Record Snow in Boulder

I spent a lot of time on record temperatures in Colorado in 2012 – they were all record highs.  Due to annual weather variability, there are a couple of different records in April 2013: record lows.  There have been four record lows set or tied in Denver, CO this April:

9F on April 9th

6F on April 10th

22F on April 16th (tie)

21F on April 22nd

Needless to say, with record low temperatures due to vigorous synoptic cyclones that brought Arctic air masses down into the middle of the country, April’s average temperature is among the lowest on record.  I will have more to say about that next week after the month ends.  Denver may not record a bottom-10 moth because much more seasonable weather is on tap for the next week.  In contrast, two record highs were set in April 2012: 84F on the 1st and 88F on the 24th.

In other news, Boulder, CO set a monthly record for snowfall: 47.4″ through the 23rd!  The old record of 44″ was set in 1957.  The official snowfall measurement site for Denver (Denver Int’l Airport) recorded “only” 20.4″ of snow for the month-to-date.  With 60F+ temperatures forecasted from today through next Tuesday, DIA won’t challenge the top-10 snowiest Aprils (#10 recorded 21.0″ of snow).

Remember that one month’s, season’s or year’s temperatures, precipitation, or even drought are not indicative by themselves of climate change.  They are too heavily influenced by individual weather systems.  When I discuss climate change, I write about long-term trends (decadal to multi-decadal).  Natural variability influences individual weather events that overlie the long-term climate signal.  I’ve written before that climate change means we are more likely to see record high temperatures than record low temperatures.  The weather will continue to set both, but will set the former at a higher rate moving forward than the latter.  Of course, I for one am very glad there was more precipitation than normal for April.  Last year’s drought and record hot summer was not enjoyable to live through.  Denver-Boulder and the surrounding region will unfortunately need months in a row of above average precipitation to break the long-term drought.  This spring’s precipitation pattern slightly reduced the intensity and areal coverage of drought.  I will update my last drought post in the next couple of days.


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NASA & NOAA: March 2013 9th, 10th Warmest Globally On Record

According to data released by NOAA, March was the 10th warmest globally on record.  Here are the NOAA data and report.  NASA also released their suite of graphics, but their surface temperature data page is down today, so I cannot relay how NASA’s March temperature compares to historical Marches.  Once their site is back up, I will update this post.  [Update: NASA's analysis resulted in their 9th warmest March on record.  Here are the data for  NASA’s analysis.] The two agencies have slightly different analysis techniques, which in this case resulted in not only different temperature anomaly values but somewhat different rankings as well.  The two techniques provide a check on one another and confidence for us.

The details:

March’s global average temperatures were 0.59°C (1.062°F) above normal (1951-1980), according to NASA, as the following graphic shows.  The past three months have a +0.57°C temperature anomaly.  And the latest 12-month period (Apr 2012 – Mar 2013) had a +0.60°C temperature anomaly.  The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index.  The recent downturn (2010-2012) was largely due to the latest La Niña event (see below for more) that ended early last summer.  Since then, ENSO conditions returned to a neutral state (neither La Niña nor El Niñ0).  Therefore, as previous anomalously cool months fall off the back of the running mean, and barring another La Niña, the 12-month temperature trace should track upward again throughout 2013.

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Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through March 2013 from NASA.

According to NOAA, March’s global average temperatures were 0.58°C (1.044°F) above the 20th century mean of 12.7°C (54.9°F).  NOAA’s global temperature anomaly map for March (duplicated below) shows where conditions were warmer than average during the month.

 photo GlobalTemperatureAnomalyMap201303_zpsf432fd9b.gif

Figure 2. Global temperature anomaly map for March 2013 from NOAA.

The two different analyses’ importance is also shown by the preceding two figures.  Despite small differences in specific global temperature anomalies, both analyses picked up on the same temperature patterns and their relative strength.

The very warm conditions found over Greenland are a concern.  Greenland was warmer than average during more months in recent history than not.  In contrast to 2012, northern Eurasian temperatures were much cooler than normal.  This is likely a temporary, seasonal effect.  Long-term temperatures over much of this region continue to rise at among the fastest rate for any region on Earth.

The NASA and NOAA surface temperature maps correlate well with the 500-mb height pressure anomalies, as seen in this graph:

 photo NOAA500hPaanomalymap201303_zps6d024aed.gif

Figure 3. 500-mb heights (white contours) and anomalies (m; color contours) during March 2013.

Note the correspondence between the height map and the NASA & NOAA surface temperature maps: lower heights (negative height anomalies) present over the North Atlantic and northern Eurasia overlay the cold surface temperature anomalies at the surface.  Similarly, warm surface temperature anomalies are located under the positive 500-mb height anomalies.

These temperature observations are of interest for the following reason: the globe came out of a moderate La Niña event in the first half of last year.  During the second half of the 2012 and the first part of 2013, we remained in a ENSO-neutral state (neither El Niño nor La Niña):

 photo NinoSSTAnom20130401_zpsf59ac6f7.gif

Figure 4. Time series of weekly SST data from NCEP (NOAA).  The highest interest region for El Niño/La Niña is NINO 3.4 (2nd time series from top).

The last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012.  Since then, tropical Pacific sea-surface temperatures peaked at +0.8 (y-axis) in September 2012.  You can see the effect on global temperatures that the last La Niña had via this NASA time series.  Both the sea surface temperature and land surface temperature time series decreased from 2010 (when the globe reached record warmth) to 2012.  So a natural, low-frequency climate oscillation affected the globe’s temperatures during the past couple of years.  Underlying that oscillation is the background warming caused by humans.  And yet temperatures were still in the top-10 warmest for a calendar year (2012) and individual months, including March 2013, in recorded history.

Skeptics have pointed out that warming has “stopped” in recent years (by comparing recent temperatures to the 1998 maximum which was heavily influenced by a strong El Niño even), which they hope will introduce confusion to the public on this topic.  What is likely going on is quite different: a global annual energy imbalance exists (less outgoing energy than incoming energy).  If the surface temperature rise has seemingly stalled, the excess energy is going somewhere.  That somewhere is likely the oceans, and specifically the deep ocean (see the figures below).  Before we all cheer about this (since few people want surface temperatures to continue to rise quickly), consider the implications.  If you add heat to a material, it expands.  The ocean is no different; sea-levels are rising in part because of heat added to it in the past.  The heat that has entered in recent years won’t manifest as sea-level rise for some time, but it will happen.  Moreover, when the heated ocean comes back up to the surface, that heat will then be released to the atmosphere, which will raise surface temperatures as well as introduce additional water vapor.  Thus, the short-term warming rate might have slowed down, but we have locked in future warming (higher future warming rate) as well as future climate effects.

 photo Total-Heat-Content.gif

Figure 5. Total global heat content anomaly from 1950-2004. An overwhelming majority of energy went to the global oceans.

 photo Ocean_heat_content_balmaseda_et_al_zps23184297.jpg

Figure 6. New research that shows anomalous ocean heat energy location since the late 1950s.  The purple lines in the graph show how the heat content of the whole ocean has changed over the past five decades. The blue lines represent only the top 700 m and the grey lines are just the top 300 m.  Source: Balmaseda et al., (2013)

Balmaseda et al.’s work demonstrates the transport of anomalous energy through the depth of the global oceans.  Note that the grey lines’ lack of significant change from 2004-2008 (upper 300m).  Observations of surface temperature include the very top part of this 300m layer.  Since the layer hasn’t changed much, neither have surface temperature readings.  Note the rapid increase in heat content within the top 700m.  Given the lack of increase in the top 300m, the 300-700m layer heat content must have increased.  By the same logic, the rapid growth in heat content throughout the depth of the ocean, which did not stall post-2004, provides evidence for anomalous heat location.  You can also see the impact of major volcanic eruptions on ocean heat content: less incoming solar radiation means less absorbed heat.

A significant question for climate scientists is this: are climate models capable of picking up this heat anomaly signal and do they show a similar trend?  If they aren’t, then their projections of surface temperature change is likely to be incorrect since the heat is warming the abyssal ocean and not the land and atmosphere in the 2000s and 2010s.  If they aren’t, climate policy is also impacted.  Instead of warmer surface temperatures (and effects on drought, agriculture, and health to name just a few), anomalous ocean heat content will impact coastal communities more than previously thought.  Consider the implications of that in addition to the AR4’s lack of consideration of land-based ice melt: sea level projections could be too conservative.

That said, it is also a fair question to ask whether today’s climate policies are sufficient for today’s climate.  In many cases, I would say  they aren’t sufficient.  Paying for recovery from seemingly localized severe weather and climate events is and always will be more expensive than paying to increase resilience from those events.  As drought continues to impact US agriculture, as Arctic ice continues to melt to new record lows, as storms come ashore and impacts communities that are not prepared for today’s high-risk events (due mostly to poor zoning and destruction of natural protections), economic costs will accumulate in this and in future decades.  It is up to us how many costs we subject ourselves to.

As President Obama began his second term with climate change “a priority”, he tosses aside the most effective tool available and most recommended by economists: a carbon tax.  Every other policy tool will be less effective than a Pigouvian tax at minimizing the actions that cause future economic harm.  It is up to the citizens of this country, and others, to take the lead on this topic.  We have to demand common sense actions that will actually make a difference.  But be forewarned: even if we take action today, we will still see more warmest La Niña years, more warmest El Niño years, more drought, higher sea levels, increased ocean acidification, more plant stress, and more ecosystem stress.  The biggest difference between efforts in the 1980s and 1990s to scrub sulfur and CFC emissions and future efforts to reduce CO2 emissions is this: the first two yielded an almost immediate result while it will take decades before CO2 emission reductions produce tangible results humans can see.

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