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.
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.
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:
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).
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.
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.
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:
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.
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.
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.
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:
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):
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.
Figure 5. Total global heat content anomaly from 1950-2004. An overwhelming majority of energy went to the global oceans.
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.
Abram et al.‘s Figure 5| Melt response over the past millennium. a, Schematic of Prince Gustav ice shelf history showing its presence (blue), intervals of rapid retreat (1957 and 1989; yellow) and collapse (1995; red). b,c, JRI mean temperature anomaly (green;b) and melt percentage (red;c) shown as 11-year moving averages. Thick lines are 21-year Gaussian kernel filters; dashed lines denote 1981–2000 mean. Lowest temperatures and melt occurred at AD 1410–1460, followed by progressive warming and a nonlinear melt increase. d, The occurrence of melt layers (grey lines) and a 100-year stepped average of melt frequency (purple) at Siple Dome in West Antarctica.
New research published in Nature Geoscience from Nerilie J. Abram et al. (subs. req’d) presents evidence that West Antarctic ice melt accelerated over the course of the last 1,000 years. About 400 years ago, average temperature anomalies (based off the 1981-2000 mean) increased from -1°C to -0.75°C (green curve in above graphic). You can see the interannual and interdecadal variability in this time period, which was natural. Then, starting 100 years ago, temperature anomalies rose from -0.75°C to today’s slightly positive anomaly. As a result, the melt percentage jumped to 5% at James Ross Island. That melt jump was nonlinear due to the ~0C melt threshold. As the authors state, “where summer temperatures do exceed the melting threshold, the amount of melt produced is proportional to the sum of the daily positive temperatures rather than their mean. This means that as average summer temperature increases and positive temperature days become warmer and more frequent, the amount of melt produced will exhibit an exponential increase”.
That cause-and-effect relationship is one reason why a 3°C average temperature rise carries so much more impact than a 2°C average temperature rise in polar regions. It also explains why small changes in historical temperatures allowed the ice shelves to form in the first place. The large “permanent” ice shelf collapses in recent history are the effect of rising temperatures. It should be obvious too that predicting the timing of future ice shelf collapses is difficult if not impossible.
The Wilkins Ice Shelf collapsed suddenly in 2009. This shelf is located southwest of the James Ross Island site cited above. As I wrote in the Wilkins post, six other shelves completely collapsed in contemporary times: Prince Gustav Channel, Larsen Inlet, Larsen A, Larsen B, Wordie, Muller and the Jones Ice Shelf. These ice shelves responded to the West Antarctic Ice Sheet (WAIS) warming observed in the last century or so. WAIS warming is occurring faster than almost any other location on the globe. There are areas in the Arctic and now the Antarctic that have observed +2.4°C warming from 1958 through 2009. In addition to anthropogenic near-surface temperature rise, the ocean surrounding Antarctica has warmed recently. Ice shelves are therefore being melted from above as well as below. Does the following sound familiar? “Over the past 18 years, Martinson and his colleagues have measured the physical properties of the ocean around Antarctica and came to the startling conclusion that the majority of the heat anomalies they have measured have occurred since 1960. Unfortunately, those anomalies have been growing exponentially ever since.”
Additional coverage of this paper can be found here and here. [h/t Martin Lack for the HuffPo link]
Based on the above, we know that West Antarctica is warming very rapidly. We know that warming anomalies are growing exponentially. Problematically, even small temperature changes cause exponential changes in melt. Exponential change growing off of exponential change creates a highly nonlinear, and therefore very unpredictable system. What might that mean for the WAIS? It could mean that rapid effects take place in the future. In other words, ice sheet properties could change quickly. Large melt areas could start one day without very little prior signal. Additional ice sheet collapses could take place without much notice. Increasing greenhouse gas emissions will cause increasing radiative forcing, which in turn will cause increased heat storage by some climate component (primarily the ocean to date, but also the atmosphere). Current global energy imbalance guarantees decades’ worth of additional heating. That heat will eventually impact Antarctica and its massive ice sheet. Melting of global land-based ice to date increased global sea level by an average of 8 inches in the last 100 years. If the entire West Antarctic Ice Sheet melted (which would happen sooner than East Antarctica because it rests on bedrock below sea level), sea levels would rise 4.8 meters. The entire WAIS won’t melt for centuries, but sea levels would easily rise more quickly than the current 3mm/yr as annual WAIS melt increases due to increasing temperatures.
There is no catastrophe knocking on the door today, but WAIS melt will affect coastal regions this century. Total sea level rise off the east coast of the US exceeded the global average, which has already caused communities to re-examine infrastructure. Higher levees and other protective structures either have been built or are being considered by cities such as Washington, D.C., Norfolk, and New York City. Efforts to date haven’t been sufficient (see Hurricane Sandy damage along the New Jersey shore), which points to a need for more aggressive analysis of needs and implementation of new climate-based policies. Costs to these and other communities will grow as international mitigation efforts stall.
According to the NSIDC, weather conditions once again caused less freezing to occur on the Atlantic side of the Arctic Ocean and more freezing on the Pacific side than normal this winter. Similar conditions occurred during the past six boreal winters. Sea ice creation during February measured 766,000 sq. km. Despite this rather rapid growth (38% higher than normal), February′s extent remained well below average for the month. Instead of measuring near 15.64 million sq. km., February 2013′s average extent was only 14.66 million sq. km., a 980,000 sq. km. difference! The Arctic likely reached its maximum annual extent about 10 days ago. In terms of annual maximum values, 2013′s 15.13 million sq. km. was 733,000 lower than normal.February’s relatively high rate of ice formation for February related to the lack of existing sea ice at the beginning of the month. Without ice already in the Ocean, new ice formed as winter continued.
Barents Sea (Atlantic side) ice finally edged toward its climatological normal value during the month after remaining low this winter, as it did in the past 10 winters. Kara Sea (Atlantic side) ice recovered from low extent the past couple of months, which is different from February 2012′s conditions. 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, a 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.
In terms of climatological trends, Arctic sea ice extent in February has decreased by 2.9% 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.
Arctic Pictures and Graphs
The following graphic is a satellite representation of Arctic ice as of February 11, 2013:
As is normal for this time of year, there is not a large difference between these two graphics. Any differences are primarily due to storm systems’ presence that push ice around, or the lack thereof. The lack of sea ice in the Barents Sea (north of Europe) is problematic because wind and ocean currents typically pile sea ice up on the Atlantic side of the Arctic. Sea ice presence in the Bering Sea (between Alaska and Russia) does not alleviate this problem because currents take ice from that area and transport it into the Arctic and then out into the Atlantic. The sea ice on the Atlantic side would be among the first that currents transport and then melt during the spring. With sea ice missing on the Atlantic side, currents will more easily transport Arctic sea ice to southern latitudes where it melts.
Many people questioned the overall health of the Arctic ice pack earlier this month when images (like the one below) and video documented extensive cracks in the ice in the Chukchi and Beaufort Seas. A fellow blogger (and new author!) emailed me about this phenomenon and I wrote that I would blog my thoughts on the topic. As Andrew Freedman wrote, “According to the National Snow and Ice Data Center (NSIDC) in Boulder, Colo., this fracturing event appears to be related to a storm that passed over the North Pole on Feb. 8, 2013, creating strong off-shore ice motion. The event is unusual but not unheard of, as similar patterns were seen in early 2011 and 2008. However, the NSIDC said the fracturing this time is more extensive.” The worry is the extent and size of the cracks and leads as well as the early calendar date at which they are all appearing – up to weeks before normal.
I found this article on the topic and agree with Greg Laden, the author. The cracks and leads might be a big deal or they might not. We will have to wait until the minimum sea ice extent occurs in September before we issue judgment. The scientifically sound course of action would be to wait until early cracks appeared in multiple seasons and then see what the range of response later in the year is. For all we know, the cracks could allow for even more ice to form in March than normal and delay the onset of melting. It strikes me as scientifically unsound and even irresponsible to conjecture about the existence and effect of processes, which we do not understand well. If scientists crow about upcoming devastating Arctic sea ice loss this year and reality doesn’t conform to their wishes, how much credibility with the public do they engender? I think observers should stay patient and discuss the phenomena and effects we do understand – there is plenty of material with which to work!
Figure 3 – NOAA AVHRR infrared picture of Arctic sea ice on 20130312.
The following graph of Arctic ice volume from the end of February demonstrates:
Figure 4 – PIOMAS Arctic sea ice volume time series through February 2013.
As the graph shows, volume (length*width*height) hit another record minimum in June 2012. Moreover, the volume remains far from normal since it just returned to the -2 standard deviation envelope (light gray). I understand that most readers don’t have an excellent handle on statistics, but conditions between -1 and -2 standard deviations are 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 are shifting from what they were in the past few centuries; a new normal is developing. 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 means that natural conditions are not the likely cause; rather, another cause is much more likely to be responsible for this behavior: human influence.
Arctic Sea Ice Extent
Take a look at February’s areal extent time series data:
Figure 5 – NSIDC Arctic sea ice extent time series through late March 2013 compared with last five years’ data and climatological norm (dark gray line) and standard deviation envelope (light gray).
As you can see, this year’s extent (light blue cuve) grew more rapidly in December than February. This graph also shows that this year’s extent remained at historically low levels through the winter, well below average values (thick gray curve), just as it did in the previous five winters, which are also shown on this graph. In this month’s version, NSIDC also plotted the previous four years’ data (2008 through 2012). You can also see what happened to conditions during late March and early April last spring (dark green curve). A late season freeze surge occurred, which delayed the date of maximum extent by a number of weeks. Last year’s surge has no bearing on what might happen over the next couple of weeks this year. Weather conditions and some low-frequency climate oscillations (AO) are different this year and have more bearing on ice conditions than last year’s date of maximum extent.
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from February 11, 2013:
Ice growth is easily visible around the continent. There is more Antarctic sea ice today than there normally is on this date in the year. The reason for this is the extra ice in the Weddell Sea (east of the Antarctic Peninsula that juts up toward South America). This ice exists this austral summer due to an anomalous atmospheric circulation pattern: persistent high pressure west of the Weddell sea pushed sea ice north. The same winds that pushed the sea ice north also moved cold Antarctic air over the Sea, which has kept ice melt rate well below normal. A similar mechanism helped sea ice form in the Bering Sea so far this 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, reinforcing 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 mid-March:
Given the lack of climate policy development to date, Arctic conditions will likely continue to deteriorate for the foreseeable future. The Arctic Ocean will soak up additional energy (heat) from the Sun due to lack of reflective sea ice. 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.
More worrisome for long-term concerns 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 February and January 2013. For further comparison, here is my State of Polar Sea Ice post from March 2012.
Update
I meant to include the following two graphs in this post because of the historical nature they represent.
The difference between these two graphics is obvious since they were taken near the time of minimum area (2012) and maximum area (2013). In terms of magnitude, the freeze season of 2012-2013 produced the highest amount of frozen ice area in the modern record (11.168 million sq. km.). The value of ice area last September was the lowest on record and the value of ice area earlier this month was the highest in four years. March’s area value occurred because of the factors I discussed above that boil down to this: the relative lack of thick ice in recent winters permitted rapid ice growth, albeit thin ice that melts quickly the following year. In addition to new record low area values in the future, significant oscillations from minimum to maximum and back again are likely to occur in the future as well. This does not contradict climate change; it is a manifestation of climate change. I hope write more about this topic soon, but countries are reconstructing international policy (military and economic) as a result of the changes seen in the Arctic. Those policy shifts will have societal repercussions, which I venture say few people realize today.
Climate change skeptics used the recent slowdown in observed surface warming to claim that 20th century warming was temporary and that the Earth would return to lower average annual temperatures. They offered up many potential explanations for the slowdown, none of which make physical sense. The Sun’s 11-year cycle (often used to explain away warming), a primary argument brought forth, is not the reason: this cycle’s solar maximum is near at hand, yet warming has slowed down recently.
Recently accepted research points to a viable physical explanation. In addition to oceanic transport of heat to the deep ocean and recent La Nina events, sulfuric emissions from small and mid-sized volcanoes entered the lower stratosphere and reflected more incoming solar radiation than normal. This research separated the effect of natural sulfur emissions from anthropogenic emissions, using a model, to determine the former had a much larger influence than thought. Aerosol optical depth (AOD) is a calculated metric used to represent how opaque or transparent the atmosphere is to different radiation wavelengths. The layer between 20 and 30 km increased 4-10% per year since 2000, which is a significant change from normal conditions – significant enough to have effects on Earth’s climate.
Here is one of the paper’s graphical results:
Figure 1. Observed and modeled time series of stratospheric AOD from three latitude bands. Satellite observations are represented by the black line. Base-line model runs are in green. Model runs with the increase in anthropogenic emissions from China and India are in blue. The dashed blue line depicts a model run with 10x the actual increase in anthropogenic emissions. The model run with volcanic emissions is in red. The black diamonds and initials along the bottom of the plot represent the volcanic eruptions that were included in the model run. (Source: Neely paper; subs. req’d.)
As the caption says, satellite measurements are denoted by the thick black curve. Note the large increase in AOD (higher opacity) over the tropics in the mid-2000s (b) and the large AOD increase over the northern mid-latitudes in the late-2000s (a). While not a perfect fit to the observations, the model run with volcanic eruptions (red curve) does the best job of explaining the origin of the SO2. Individual eruptions are indicated by black diamonds on the bottom of each sub-plot. The effects of volcanic eruptions on climate are, in a general sense, well-known. Injections of SO2 into the stratosphere reflects sunlight, which reduces the amount of energy entering the Earth’s climate system. The difference between one large-scale eruption (e.g. Pinatubo in 1991) or many mid-sized eruptions in a short time-period (see above) is not large as far as the climate is concerned.
This could be good news as far as the climate is concerned, at least in the shorth-term. If incoming energy were reflected back into space instead of being stored in the system, we can physically explain the observed temperature trend slowdown (see Figure 2) and treat the slowdown as real instead of waiting for that energy to transfer from the oceans to the atmosphere, for example.
There is also bad news however. From the study (emphasis mine):
The significant portion of the radiative forcing due to increases in stratospheric aerosol from 2000 to 2010, interpreted as a mechanism of global cooling [Solomon et al., 2011], may now be completely attributed to volcanic sources and should not be considered a trend. Rather, the stratospheric aerosol layer should be treated as a natural source of radiative forcing that is continuously perturbed by volcanic injections of a range of sizes, and potentially other sources such as large fires.
Figure 2. Global mean surface temperature anomaly maps and 12-month running mean time series through January 2013 from NASA.
We can see from the 12-month running mean time series (lower-right in Figure 2) that NASA’s temperature index increased more slowly during the latter part of the 2000s than the 1990s. Neely et al. suggest that there is no physical reason to conclude that slowdown is a trend of opposite sign than that seen throughout the 20th century. In other words, once the SO2 precipitates from the stratosphere, as it eventually will, the background warming trend will re-establish itself. Indeed, future warming will likely be stronger than past warming because CO2 concentrations have not decreased in the past ten years. To the contrary, they have increased at a faster rate than before. Greenhouse gases have simply had less incoming radiation to absorb than they did 10 years ago due to the recent presence of SO2 in the stratosphere.
Neely’s coauthor Brian Toon had this to say:
Toon of CU-Boulder’s Department of Atmospheric and Oceanic Sciences. “But overall these eruptions are not going to counter the greenhouse effect. Emissions of volcanic gases go up and down, helping to cool or heat the planet, while greenhouse gas emissions from human activity just continue to go up.”
This situation provides a good example of another aspect of climate policy. I wrote about geoengineering earlier this year as part of a Polar Sea Ice post (much more discussion took place here). One proposed mechanism to reduce the impacts of climate change is human injection of SO2 into the stratosphere, which would mimic natural volcanic effects. If we implemented such a strategy without simultaneously reducing atmospheric greenhouse gas concentrations, then abruptly stopped the injection (due to lack of funds or international controversy), the resulting warming signal would be higher post-injection than pre-injection. The result would be unprecedented due to the large warming signal such a halt would introduce to the climate system.
In one more respect then, policymakers have wasted the past decade. Instead of developing and implementing climate mitigation policies, international inaction continued. Once the atmosphere removes the SO2, the climate signal will be stronger than before. We cannot and should not rely on future volcanic SO2 emissions to mitigate our GHG emissions. The lack of robust policies is a choice, but it is not a wise long-term choice.
According to data released by NASA and NOAA last week, January was the 6th and 9th warmest January’s (respectively) 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 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:
January’s global average temperatures were 0.61°C (1.098°F) above normal (1951-1980), according to NASA, as the following graphic shows. The warmest regions on Earth coincide with the locations where climate models have been projecting the most warmth will occur: high latitudes (especially within the Arctic Circle). The past three months have a +0.58°C temperature anomaly. And the latest 12-month period (Feb 2012 – Jan 2013) had a +0.58°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) is 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 in 2013.
Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through January 2013 from NASA.
According to NOAA, January’s global average temperatures were 0.54°C (0.97°F) above the 20th century mean of 14.0°C (57.2°F). NOAA’s global temperature anomaly map for January (duplicated below) shows where conditions were warmer than average during the month.
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.
The very warm conditions found over Greenland and Alaska are a concern. These areas were warmer than average during more months in recent history than not. Additionally, Australia was much warmer than usual. Indeed, Australia’s January average temperature was the highest on record: +2.28°C (4.10°F!) above the 1961–1990 average, besting the previous record set in 1932 by 0.11°C (0.20°F). In contrast to 2012, Siberian temperatures were cooler than normal. This is likely a temporary, seasonal effect. Long-term temperatures over northern Siberia continue to rise at among the fastest rate for any region on Earth.
These observations are also worrisome for the following reason: the globe came out of a moderate La Niña event in the first half of the year. During the second half of the year, we remained in a ENSO-neutral state (neither El Niño nor La Niña):
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 January 2013, in recorded history.
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) 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. 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 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 additional water vapor. Thus, the immediate warming rate might have slowed down, but we have locked in future warming (higher future warming rate).
In a previous post on global temperatures, I pointed a few things out and asked some questions. The Conference of Parties summit produced no meaningful climate action (November 2012). Countries agreed to have something on paper by 2015 and enacted by 2020. If everything goes as planned (a huge assumption given the lack of historical progress), significant carbon reductions wouldn’t occur until later in the 2020s – too late to ensure <2°C warming by 2100. If, as is much more likely, everything doesn’t go as planned, reductions wouldn’t occur until later than the 2020s. Additional meetings are scheduled for this year, but I maintain my expectation that nothing meaningful will come from them. The international process is ill-equipped to handle all the legitimate interest groups in one fell swoop.
Instead, actions that start locally and grow with time are more likely to address emissions and eventual warming and other climate change effects. People started small-scale activities in cities around the world in recent years. There are also regional and international carbon markets. While most markets were poorly designed, lessons learned from the first generation can be used to make future generation markets more effective. As these small-scale efforts grow and their effects combine, larger bodies will need to address differences between them so that they work for larger populations and markets.
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 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.
According to the NSIDC, weather conditions once again caused less freezing to occur on the Atlantic side of the Arctic Ocean and more freezing on the Pacific side than normal. Similar conditions occurred during the past six boreal winters. Sea ice creation during January measured 1.36 million sq. km. Despite this rather rapid growth, January′s extent remained well below average for the month. Instead of measuring near 14.84 million sq. km., January 2013′s extent was only 13.78 million sq. km., a 1.06 million sq. km. difference! The Barents Sea recorded lower than average sea ice, which is an unusual condition for January. Kara Sea ice recovered from low extent the past couple of months. The Bering Sea, which saw ice extent growth due to anomalous northerly winds in 2011-2012, saw similar conditions in December 2012 and January 2013. This has caused anomalously high ice extent in the Bering Sea. Previously this winter, a 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 has returned to a more neutral phase in the past month, which has kept Arctic air closer to where it normally is this time of year.
In terms of longer, climatological trends, Arctic sea ice extent in January has decreased by 3.2% per decade. This rate is closest to zero in the 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 (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.
Arctic Pictures and Graphs
The following graphic is a satellite representation of Arctic ice as of January 9, 2013:
The lack of sea ice in the Barents Sea (north of Europe) is problematic because wind and ocean currents typically pile sea ice up on the Atlantic side of the Arctic. Sea ice presence in the Bering Sea (between Alaska and Russia) does not alleviate this problem because currents take ice from that area and transport it into the Arctic. That sea ice will be among the first to melt completely come spring. With sea ice missing on the Atlantic side, currents will more easily transport Arctic sea ice to southern latitudes where it melts.
Overall, the health of the ice pack is not healthy, as the following graph of Arctic ice volume from the end of January demonstrates:
Figure 3 – PIOMAS Arctic sea ice volume time series through January 2013.
As the graph shows, volume (length*width*height) hit another record minimum in June 2012. Moreover, the volume remains far from normal since it just returned to the -2 standard deviation envelope (light gray). I understand that most readers don’t have an excellent handle on statistics, but conditions between -1 and -2 standard deviations are 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 are shifting from what they were in the past few centuries; a new normal is developing. 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 means that natural conditions are not the likely cause; rather, another cause is much more likely to be responsible for this behavior: human influence.
Arctic Sea Ice Extent
Take a look at January’s areal extent time series data:
As you can see, the extent (light blue line) grew rapidly in November but still remained at historically low levels through the winter. The extent remained well below average values (thick gray line) throughout the fall and early winter. The time series of sea ice extent for previous low years is also shown on this graph. In this month’s version, NSIDC also plotted the previous four years’ data. You can see the effect of the wintertime conditions that I described above: the difference between a year’s extent and the average value in January or February is smaller than the difference in October. This leads us to examine the differences between the historical mean, the negative two standard deviation (light gray) below that mean, and the 2012-2013 time series.
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from January 9, 2013:
Ice loss is easily visible around the continent. There is slightly more Antarctic sea ice today than there normally is on this date in the year. The reason for this is the extra ice in the Weddell Sea (east of the Antarctic Peninsula that juts up toward South America). This ice exists this winter due to an anomalous atmospheric circulation pattern: persistent high pressure west of the Weddell sea pushed sea ice north. The same winds that pushed the sea ice north also moved cold Antarctic air over the Sea, which has kept ice melt rate well below normal. A similar mechanism helped sea ice form in the Bering Sea so far this winter.
As a reminder, the difference between 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, reinforcing 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. 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). 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 melting on Greenland. Were we to face 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 from February 11th:
Given the lack of climate policy development to date, Arctic conditions will likely continue to deteriorate for the foreseeable future. The Arctic Ocean will soak up additional energy from the Sun due to lack of reflective sea ice. Additional energy in the climate system creates cascading effects through the system. The energy pushes the Arctic Oscillation to a negative phase, which allows anomalously cold air to pour south over Northern Hemisphere land masses while warm air moves over the Arctic. This impacts weather patterns throughout the year.
More worrisome for long-term concerns 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, 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. Or we can be proactive, minimize future global effects, and reduce societal costs. The choice remains ours.
Errata
Here are my State of the Poles posts from January and September.
According to data released by NASA and NOAA this week, 2012 was the 9th and 10th warmest years (respectively) globally on record. NASA’s analysis produced the 9th warmest year in its dataset; NOAA recorded the 10th warmest year in its dataset. 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 details:
2012’s global average temperature was +0.56°C (1°F) warmer than the 1951-1980 base period average (1951-1980), according to NASA, as the following graphic shows. The warmest regions on Earth (by anomaly) were the Arctic and central North America. The fall months have a +0.68°C temperature anomaly, which was the highest three-month anomaly in 2012 due to the absence of La Niña. In contrast, Dec-Jan-Feb produced the lowest temperature anomaly of the year because of the preceding La Niña, which was moderate in strength. And the latest 12-month period (Nov 2011 – Oct 2012) had a +0.53°C temperature anomaly. This anomaly is likely to grow larger in the first part of 2013 as the early months of 2012 (influenced by La Niña) slide off. The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index. The recent downturn (2010 to 2012) shows the effect of the latest La Niña event (see below for more) that ended in early 2012. During the summer of 2012, ENSO conditions returned to a neutral state. Therefore, the temperature trace (12-mo running mean) should track upward again as we proceed through 2013.
Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through December 2012 from NASA.
According to NOAA, 2012’s global average temperatures were 0.57°C (1.03°F) above the 20th century mean of 13.9°C (57.0°F). NOAA’s global temperature anomaly map for 2012 (duplicated below) reinforces the message: high latitudes continue to warm at a faster rate than the mid- or low-latitudes.
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.
The continued anomalous warmth over Siberia is especially worrisome due to the vast methane reserves locked into the tundra and under the seabed near the region. Methane is a stronger greenhouse gas than carbon dioxide over short time-frames (<100y),which is the leading cause of the warmth we’re now witnessing. As I discussed in the comments in post this summer, the warming signal from methane likely hasn’t been captured yet since the yearly natural variability and the CO2-caused warming signals are much stronger. It is likely that we will not detect the methane signal for many more years.
These observations are also worrisome for the following reason: the globe came out of a moderate La Niña event in the first half of the year. During the second half of the year, we remained in a ENSO-neutral state (neither El Niño nor La Niña):
As the second time series graph (labeled NINO3.4) shows, the last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012. Since then, SSTs peaked at +0.8 in September (y-axis). 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 the globe’s temperatures were affected by a natural, low-frequency climate oscillation during the past couple of years. And yet temperatures were still in the top-10 warmest for a calendar year in recorded history.
Indeed, this was the warmest La Niña year on record:
This figure shows that 2012 edged out 2011 as the warmest La Niña year on record (since 1950). It also shows a clear trend seen in every temperature record of this length: La Niña years are getting warmer with time (note the difference between 2012 and 1956, for instance). El Niño years are getting warmer with time (note the difference between 2010 and 1958). ENSO-neutral years are getting warmer with time. The globe got warmer throughout the 20th and into the 21st century. Do not pay too much attention to any single year as “evidence” that global warming stopped. As I stated above, natural low-frequency climate oscillations introduce a lot of noise into the temperature signal. Climate is measured over decades and the decadal trend is obvious here: warmer with time.
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: if an energy imbalance exists (less outgoing energy than incoming) and the surface temperature rise has seemingly stalled, the excess energy has to be going somewhere. That somewhere is likely to be the oceans, and specifically the deep ocean. 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 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 additional water vapor. Thus, the immediate warming might have slowed down, but we have locked in future warming.
In my previous post on global temperatures, I pointed a few things out and asked some questions. The Conference of Parties summit produced no meaningful climate action. Countries agreed to have something on paper by 2015 and enacted by 2020. If everything goes as planned, significant carbon reductions wouldn’t occur until later in the 2020s – too late to ensure <2°C warming by 2100. If, as is much more likely, everything doesn’t go as planned, reductions wouldn’t occur until later than the 2020s. Additional meetings are scheduled for later this year, but I maintain my expectation that nothing meaningful will come from them. The international process is ill-equipped to handle all the legitimate interest groups in one fell swoop.
The northeast continues to recover from Superstorm Sandy. New York and New Jersey began to plan for infrastructure with increased resilience from the next storm, which will eventually hit the area. Congress took way too long to approve relief money (months, instead of days as it did after Katrina). $60 billion will go a long ways toward assisting the region, especially if people take seriously the threat of living next to the ocean, which has been uncharacteristically quiet for decades.
Paying for recovery is and always will be more expensive than paying to increase resilience from disasters. 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 much grief we subject ourselves to. As President Obama begins his second term and climate change “will be a priority in his second term”, he tosses aside the tool 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 ENSO-neutral years.
