Weatherdem's Weblog

Bridging climate science, citizens, and policy


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El Niño and La Niña Redefined

This is the week to publish lots of interesting events and articles apparently.  I have a number of things I would love to post about, but only so much time.  Here is one that relates directly to something I posted on earlier: warmest La Niña years.  Just a few short weeks after NOAA operations wrote that 2012’s La Niña was the warmest on records, NOAA researchers announced they recalculated historical La Niñas because of warming global temperatures.  NOAA confirmed something that occurred to me while I was writing that post: eventually, historical El Niños will be cooler than future La Niñas.  How then will we compare events across time as the climate evolves?  The answer is simple: redefine El Niño and La Niña.  Instead of one climate period of record, compare historical ENSO events to their contemporary climate.  In other words, “each five-year period in the historical record now has its own 30-year average centered on the first year in the period”: compare 1950-1955 to the 1936-1965 average climate; compare 1956-1960 to the 1941-1970 average.  This is different from the previous practice in which NOAA compared 1950-1955 to 1981-2010 and compared 2013 to 1981-2010.  The 1950-1955 period existed in a different enough climate that it cannot be equitably compared to the most recent climatological period.

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Figure 1. “The average monthly temperatures in the central tropical Pacific have been increasing. This graph shows the new 30-year averages that NOAA is using to calculate the relative strength of historic El Niño and La Niña events.”

I want to point out something on this graph.  Is long-term warming evident in this graph?  Yes, there is.  But note they plot the breakdown by month.  The difference between 1936-1965 and 1981-2010 in October is >1°F.  Meanwhile, the same difference in May is ~0.5°F.

Here is the effect of NOAA’s change:

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Figure 2.  3-month temperature anomalies in the Nino-3.4 region.   (Top) Characterization of ENSO using 1971-2000 data.  (Bottom) Same as top, but using 1981-2010 data.

NOAA’s updated methodology resulted in the identification of two new La Niñas: 2005-06 and 2008-09.  The reason is warmer temperatures in the most recent decade than the 1970s (it sounds obvious when you say it like that).  That warming masked La Niñas with the old methodology.  It also means that the 2012 La Niña is no longer the warmest La Niña, as I related from the National Climatic Data Center last month:

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Figure 3. Anomalies of annual global temperature as measured by NOAA.  Blue bars represent La Niña years, red bars represent El Niño years, and gray bars represent ENSO-neutral years.

That record will now go down as a tie between 2006 and 2009, with 2012 coming in a close third.  This situation is analogous to the different methodologies that NOAA and NASA use to compute global temperatures and where they rank individual years.  Records might differ because of methodological differences, but the larger picture remains intact: the globe warmed in the 20th and so far in the 21st centuries.  That signal is apparent in many datasets.  Within the week, I’m sure we’ll hear from GW skeptics that La Niña years have been getting cooler since 2006.  Here is what is most important: 2000s La Niñas were warmer than 1990 Niñas, which were warmer than 1980 Niñas, etc.


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NASA & NOAA: 2012 Was In Top-10 Warmest Years For Globe On Record

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.

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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.

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Figure 2. Global temperature anomaly map for 2012 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.

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):

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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).

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:

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Figure 4. Anomalies of annual global temperature as measured by NOAA.  Blue bars represent La Niña years, red bars represent El Niño years, and gray bars represent ENSO-neutral years.

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.


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2012: Hottest Year On Record For United States

It’s official: 2012 was indeed the hottest year in 100+ years of record keeping for the contiguous U.S. (lower 48 states).  The record-breaking heat in March certainly set the table for the record and the heat just kept coming through the summer.  The previous record holder is very noteworthy.  2012 broke 1998’s record by more than 1°F!  Does that sound small?  Let’s put in perspective: that’s the average temperature for thousands of weather stations across a country over 3,000,000 sq. mi. in area for an entire year.  Previously to 2012, temperature records were broken by tenths of a degree or so.  Additionally, 1998 was the year that a high magnitude El Niño occurred.  This El Niño event caused global temperatures to spike to then-record values.  The latest La Niña event, by contrast, wrapped up during 2012.  La Niñas typically keep global temperatures cooler than they otherwise would be.  So this new record is truly astounding!

The official national annual mean temperature: 55.3°F, which was 3.3°F above the 20th century mean value of 52°F.

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Figure 1 – NOAA Graph showing year-to-date average US temperatures from 1895-2012.

This first graph shows that January and February started out warmer than usual (top-5), but it was March that separated 2012 from any other year on record.  The heat of July also caused the year-to-date average temperature to further separate 2012 from other years.  Note the separation between 2012 and the previous five-warmest years on record from March through December.  Note further that four of the six warmest years on record occurred since 1999.  Only 1921 and 1934 made the top-five before 2012 and now 1921 will drop off that list.

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Figure 2 – Contiguous US map showing state-based ranks of 2012 average temperature.

Nineteen states set all-time annual average temperature records.  This makes sense since dozens of individual stations set all-time monthly and annual temperature records.  Another nine states witnessed their 2nd warmest year on record.  Nine more states had top-five warmest years.  Only one state (Washington) wasn’t classified as “Much Above Normal” for the entire year.  The 2012 heat wave was extensive in space and severe in magnitude.

Usually, dryness tends to accompany La Niña events for the western and central US.  This condition was present again in 2012, as the next figure shows.

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Figure 3 – Contiguous US map showing state-based ranks of 2012 average precipitation.

As usual, precipitation patterns were more complex than were temperature patterns.  Record dryness occurred in Nebraska and Wyoming.  Colorado and New Mexico saw bottom-five precipitation years.  Severely dry conditions spread across the Midwest all the way to the mid-Atlantic and Georgia continued to experience dryness.  Washington and Oregon were wetter than normal as a result of the northerly position of the mean jet stream in 2012.  Louisiana and Mississippi saw wetter than normal conditions, largely as a result of Hurricane Isaac.

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Figure 4 – Contiguous US map showing state-based average actual precipitation.

I always find it useful to know the magnitude of measurements as well as how they stack up comparatively.  Figure 4 provides the former while Figure 3 provides the latter.  “Normal” precipitation varies widely across the country and even between neighboring states.  How much precipitation fell to allow NE and WY to record driest years on record?  13.04 and 8.03″, respectively.  Another useful map would be state-based difference from “normal”.

So the brutal heat that most Americans experienced was one for the record books.  As the jet stream remained in a more northerly than usual position, heat across the country dominated.  More heat and fewer storm systems in 2012 meant widespread and severe drought expanded across the country.  That drought tended to reinforce both the temperatures recorded (drying soils meant incoming solar radiation was more easily converted directly to sensible heat) and the lack of precipitation (dry soils required extra moisture to return to normal conditions).

Thankfully, record-setting temperatures didn’t occur all over the globe in 2012 (although Australia is having their own problems now in 2013).  I therefore don’t expect 2012 will be the warmest year on record globally, but a top-10 finish certainly is not out of the question.  Again, this is significant because of the extended La Niña event that ended in mid-2012.  Without the influence of anthropogenic (man-made) climate change, 2012 probably would have been cooler than will be recorded.  The background climate is warming and so La Niñas today are warmer than El Niños of yesterday.

These warming and drying conditions have massive implications for our society.  The drought that afflicted the Midwest in 2012 helped push up commodity prices as crops failed.  If that trend continues into 2013, prices will rise further, which will pinch all of our finances.  Drought in the Southwest and Midwest impacted flows in rivers (Colorado & Mississippi, among others).  The former could mean imposed restrictions in 2013 while the latter could mean reduced river transportation, which puts further pressure on goods sold in the US.  Conditions aren’t the worst recorded yet, but it is imperative that we examine resource management policies.  Are policies robust enough to handle the variability of today’s climate?  If not, they probably aren’t equipped to address future variability or change either.  What systems are critical to today’s society?  If the Southwest remains dry, does agriculture (largest user of CO river water) reduce its use or do urban users?  What sets of values guide these and other decision-making processes?


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NASA & NOAA: October 2012 Was 2nd, 4th Warmest On Record

According to data released by NASA and NOAA this week, October 2012 was the 2nd and 4th warmest October’s (respectively) globally on record.  NASA’s analysis produced the 2nd warmest October in its dataset; NOAA recorded the 4th warmest October 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:

October’s global average temperatures were 0.69°C (1.24°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 to occur for years: high latitudes (especially within the Arctic Circle in July 2012).  The past three months have a +0.63°C temperature anomaly.  And the latest 12-month period (Nov 2011 – Oct 2012) had a +0.51°C temperature anomaly.  The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index.  The recent downturn (post-2010) is largely due to the latest La Niña event (see below for more) that recently ended.  ENSO conditions returned to a neutral state.  Therefore, the temperature trace (12-mo running mean) should track upward again, especially as cooler months fall off the running mean.

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Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through October 2012 from NASA.

According to NOAA, October’s global average temperatures were 0.63°C (1.13°F) above the 20th century mean of 14.0°C (57.2°F).  NOAA’s global temperature anomaly map for October (duplicated below) reinforces the message: high latitudes continue to warm at a faster rate than the mid- or low-latitudes.

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Figure 2. Global temperature anomaly map for October 2012 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.

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.

Of additional concern are the very warm conditions found over Greenland.  Indeed, record warmth was observed at a 3200m altitude station in early July.  3.6°C may not sound that warm in July, but the station’s location at 10,500ft altitude is of interest.  In contrast, continued warmth over portions of Greenland that have not witnessed such warmth did result in rapid melting during 2012.  There was recent news that described how much faster melt has occurred over Greenland (see associated picture) than expected in the IPCC AR4.  While the record-setting sea ice melt across the Arctic Ocean this year is important in some respects, at least melting sea ice doesn’t contribute to sea level rise.  The opposite is true for Greenland melt: every drop that makes it to the ocean raises the level.  When the melt is happening 3X faster than just 20 years ago, it’s time to pay attention (note: not panic!).

These observations are also worrisome for the following reason: the globe is experiencing ENSO-neutral conditions:

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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).

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 2009 to 2011.  Note that the darker lines (running means) started to increase at the end of 2011, following the higher frequency monthly data.  ENSO-nuetral conditions are expected to continue through the next 3-6 months, after which a new El Niño event might begin.

As the globe returns to ENSO-neutral conditions this winter, how will global temperatures respond?  Remember that global temperatures typically trail ENSO conditions by 3-6 months: the recent tropical Pacific warming trend should therefore help boost global temperatures back to their most natural state (i.e., without an ENSO (La Niña) signal on top of it, although other important signals might also occur at any particular point in time).

So what do we do?  I hope most readers are aware that the 18th Conference of Parties (COP-18) meeting is currently underway in Doha, Qatar.  I’ve stated my opinion before that I don’t think putting every country in the world around the table to negotiate a climate treaty is the most appropriate approach.  Canada, Russia, and Japan removed themselves from the Kyoto Protocol recently, which means that the only large emitters left are from the European Union.  I actually think that’s more appropriate: I prefer regional and bilateral agreements – countries should have pursued them more aggressively in the past 30 years.

More to the point, we should focus on  bottom-up approaches.  There are smaller groups of people who, if provided the right type of expertise and resources when needed, could probably enact changes that will result in decreasing emissions as well as successful adaptation policies.  The developed world is decarbonizing, but not fast enough yet.  I also recommend you watch China.  They invested very large sums of money in renewable energy and other green efforts.  That money will bear fruit in the future.  The rub, of course, is we cannot accurately predict when and how today.  It will also be interesting to see how the northeast U.S. reacts to Hurricane Sandy.  They have to rebuild infrastructure.  Will they include adaptive measures while they’re at it or will they kick the can down the road?


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Warmest Year on Record Likely For US in 2012

As readers of this blog are likely aware, 2012 was brutally hot across most of the U.S. in the spring and summer.  All-time records at hundreds of stations fell, monthly records were shattered, and seasonal records were similarly set.  These conditions led to speculation that 2012 would be the U.S.’s warmest.

That speculation is likely to be borne out as true.  Even though October was the first month in seventeen in which average contiguous U.S. temperatures were below average instead of above average, the January-October average temperature continued to track well above the previous record-setting year – 1998 – as the following graph demonstrates.

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Figure 1. 2012 observed and projected contiguous U.S. temperature anomalies compared to previous top-5 anomalous years.

The current record holder is, of course, 1998 – the year which saw the strongest El Nino event of the 20th century end.  2012’s anomaly are therefore very important in context: a moderate La Nina event ended in 2012.  La Nina is typically characterized as a cooling event while El Nino is typically characterized as a warming event.  Now, those characterizations are global in nature, so interpreting their effects for the U.S. only gets more complex.  The point of this is the following: as the globe as a whole continues to warm and future El Ninos occur, the U.S. is likely to see warmer years than 2012.

The graph also contains the following information.  November and December would have to be among the ten coldest months on record in order for the 2012 average to dip below 1998’s record.  Well, November has been warmer than average so far through the first couple of weeks.  That trend is forecasted to continue for the next couple of weeks (not record-setting hot, just warmer than the 20th century average).  Therefore, the trend would have to absolutely reverse itself in December in order for 2012 to not set the new record.  Simply put, the chances of that happening are incredibly remote.

I haven’t blogged about it yet, but Hurricane Sandy’s landfall and subsequent widespread destruction might start small-scale conversations regarding the state of our infrastructure in today’s world.  Without even considering the potential future effects of anthropogenic global warming, it is clear to more and more people as weather disasters strike that we are not equipped as a society to adequately handle today’s climate.  Conditions have largely been beneficial to benign throughout the 20th century.  That wasn’t always the case prior to that and it’s likely that it won’t be the case in the future.  We have to have honest conversations about this and make hard decisions about what to build where and what industries our society should be built on.  What aid do we provide to farmers in areas that are drought-prone?  What aid do we provide to homeowners that live in high-risk areas?  What do our building codes and zoning laws allow today and should those same things be allowed in the future?  These are just a small sample of the kind of policy questions we have to ask when we see the above graph and many others like it.

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On another topic, I’m almost done with classes this semester.  I’ll get back to much more frequent posting in another month.


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NASA & NOAA: July 2012 Was 12th, 4th Warmest On Record

According to data released by NASA and NOAA this week, July 2012 was the 12th and 4th warmest July (respectively) globally on record.  NASA’s analysis produced the 12th warmest July in its dataset; NOAA recorded the 4th warmest July in its dataset.  The two agencies have slightly different analysis techniques, which in this case resulted in not only different temperature anomaly values but rather different rankings as well.

The details:

July’s global average temperatures were 0.47°C (0.85°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 to occur for years: high latitudes (especially within the Arctic Circle in July 2012).  The past three months have a +0.56°C temperature anomaly.  And the latest 12-month period (Aug 2011 – Jul 2012) had a +0.50°C temperature anomaly.  The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index.  The recent downturn (post-2010) is largely due to the latest La Niña event (see below for more) that recently ended.  As ENSO conditions return to neutral or even El Niño-like, the temperature trace should track upward again.

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Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through July 2012 from NASA.

According to NOAA, July’s global average temperatures were 0.63°C (1.13°F) above the 20th century mean of 15.2°C (1.12°F).  NOAA’s global temperature anomaly map for July (duplicated below) reinforces the message: high latitudes continue to warm at a faster rate than the mid- or low-latitudes.  Unfortunately in July 2012, almost the entire Northern Hemisphere was warmer than normal.

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Figure 2. Global temperature anomaly map for July 2012 from NOAA.

These figures show just how extreme (intensity & spatial extent) the heat wave over most of the US was during July 2012.  As many people saw during the preceding two-and-a-half weeks, England was cooler than usual.  The same was true for northwestern Europe, most of Australia, and a good portion of South America (Argentina, Bolivia, etc.)  Additional anomalous warmth occurred over Greenland, Russia, eastern Europe, and into central Asia and the Middle East.  The two different analyses’ importance is also shown by these 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 a recent post, 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.  Of additional concern are the very warm conditions found over Greenland.  Indeed, record warmth was observed at a 3200m altitude station in early July.  3.6°C may not sound that warm in July, but the station’s location at 10,500ft altitude is of interest.  I want to post more on this later, but the early July melt occurred over a very short time period, which did not result in a great deal of runoff.  In contrast, continued warmth over portions of Greenland that have not witnessed such warmth did result in rapid melting during 2012 (note: the melt season isn’t over yet either).

These observations are also worrisome for the following reason: the globe is still returning to ENSO-neutral conditions:

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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).

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 have slowly warmed back above a +0.5°C-1.0°C anomaly (y-axis).  La Niña is a cooling event of the tropical Pacific Ocean that has time-delayed effects across the globe.  It is therefore significant that the past handful of months’ global temperatures continued to rank in or near the top-5 warmest in the modern era.  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 2009 to 2011.  Note that the darker lines (running means) started to increase at the end of 2011, following the higher frequency monthly data.

As the globe returns to ENSO-neutral conditions this summer and early fall, how will global temperatures respond?  Remember that global temperatures typically trail ENSO conditions by 3-6 months: the recent tropical Pacific warming trend should therefore help boost global temperatures back to their most natural state (i.e., without an ENSO signal on top of it, although other important signals might also occur at any particular point in time).  Looking further into the future, what will next year’s temperatures be as the next El Niño develops, as predicted by a number of methods (see figure below)?

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Figure 5. Set of mid-July predictions of ENSO conditions by various models (dynamical and statistical).  To be considered an El Niño event, 3-month average temperature anomalies must be measured above +0.5°C for 5 consecutive months (so the earliest an El Niño event is likely to be announced is sometime this fall).  Approximately 1/2 of the models are predicting a new El Niño event by the end of this year.  The other models predict ENSO-neutral conditions through next spring.

From the above, I hope it is clear that the US’s recent record heat wave and historic drought are associated with the most recent La Niña event.  This is typical for the US, given dominant wind patterns that La Niña establishes.  While El Niño would add additional anomalous warmth on top of the slowly evolving climate change signal, it usually also heralds above-average precipitation over most of the US.  That would be a welcome event, given the reach and severity of the drought currently underway.


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2011: 9th Warmest Calendar Year On Record, Even With A La Niña

NASA’s James Hansen and a few of his colleagues released their assessment of 2011 global temperatures recently.  In short, 2011 was the 9th warmest year in the GISS dataset.

Just as importantly, this situation occurred in the midst of a continuing La Niña event that is of moderate strength.  La Niña is characterized by a general cooling of the tropical Pacific waters near the surface; it is frequently referred to as being the opposite of El Niño.  As La Niñas progress, global temperatures tend to cool from their normal state.  This of course has implications as scientists work to differentiate the effects of natural climate processes and those brought about by humans.  If one year’s temperatures are cooler than the preceding year’s (or are warmer), does that mean that global warming has stopped (as skeptics like to say) or does that mean that there are competing forcings that affect the temperatures recorded?

It is the assessment of an overwhelming majority of climate scientists that global warming has not stopped.  Instead, the 2nd half of 2010 and all of 2011 were dominated by La Niña events.  What does this mean?  It means that if the La Niña events had not occurred (and if there were no El Niños either), in other words purely “normal” conditions, 2011 likely would have been warmer than was recorded.  This should become obvious in the next 6 months to 3 years as this La Niña dissipates and conditions across the globe respond accordingly.  It takes ~6 months for downstream effects to show up in observations after ENSO phases start and after they go away.

Here is Hansen et al.‘s updated figure showing global land-ocean temperatures using an index:

Figure 1.  Global surface air temperature anomalies relative to 1951-1980 base period for annual and 5-year running means. Green vertical bars are 2σ error estimates (Hansen et al., 2010). [Source for all graphs: Hansen]

The last black square on the right hand side of the graph is 2011’s temperature index value: +0.51°C.  You can clearly see where the 9th highest ranking comes from when viewing this graph.  You can further see that 2011 was warmer than 2001, 2004 and 2008 (simply comparing the past 10 years of values), as well as every year prior to 2000 save 1998, the year when the last century’s strongest El Niño occurred.

But I wrote above that large changes can occur year-to-year and this is evidenced by the jagged look to the yearly data in the graph above.  So what happens if the data is analyzed in such a way as to remove the yearly signal?  Furthermore, can the ENSO and solar cycle signals be quieted down to get a better idea of what the global temperatures are likely doing?  Yes they can, as the following graph demonstrates:

Figure 2. Global surface air temperature anomalies relative to 1951-1980 base period for (a) the 12-month running mean, and (b) the 60-month and 132-month running means.

The right panel of Figure 2 demonstrates the results of the removal of the ENSO signal (red line, 60-month running mean) and the solar cycle signal (blue line, 132-month running mean).  The addition of more months into the running mean helps to remove more and more noise (to a limited degree, of course).  What is left behind is increasingly the global warming signal in global temperature data.  A key takeaway is this: the same general result can be seen regardless of the specific temperature dataset employed.

To expand on this topic a little more, here is a graph comparing mean temperature anomalies and the Nino 3.4 index (and index used to characterize the ENSO signal as El Niño or La Niña):

Figure 3. Global monthly and 12-month running mean surface temperature anomalies relative to 1951-1980 base period, and 12-month running mean of the Nino 3.4 index.

Paired with the Nino 3.4 index data, it is very easy to pick out the ENSO influence on the temperature data.  Peaks in global temperature anomalies tend to occur during El Niños while troughs in anomalies tend to occur during La Niñas.  As you can see, claims that global warming has “stopped” in the past couple of years are not likely to be correct since a prolonged La Niña has occurred during that time frame.  One good indicator of whether or not global warming has stopped will be what the global temperature anomaly is ~6 months after the next El Niño peak occurs (likely sometime in the next 3 years).

Another good indicator of whether global warming has stopped or not will be what global temperature anomalies register as the upcoming solar maximum descends from its next peak.  As the following graph illustrates, the peak is likely to occur 3+ years from now:

Figure 4. Solar irradiance from composite satellite-based time series. Data sources: For 1976/01/05 to 2011/02/02 Physikalisch Meteorologisches Observatorium Davos, World Radiation Center and for 2011/02/03 to 2012/01/11 University of Colorado Solar Radiation & Climate Experiment. Data are concatenated using the 2010/02/03 to 2011/02/02 period.

It is important to note that the global temperature response to the solar cycle is delayed by ~18 months.  So in 4-5 years from now, we’ll have a much clearer idea of the effects of global warming in the 1st half of the 2010s were.  That time period will occur after the next solar cycle maximum and after the next El Niño.  It strains credulity to think that global temperatures will be lower after those two milestones than they are today.

My thoughts on this are easily understood: it is more likely that global temperature anomalies will continue to exhibit decadal-scale rises than falls in our future (21st century).  As I’ve stated many times before, it is also likelier that projected temperature increases are underestimated, not overestimated.  We are more likely to read about additional top-10 warmest year on record in our future.  That said, I’d be happy to be wrong about all of this.  The changing environment we’re living in demands changes to the way our societies function.  I don’t believe those changes will be equally catastrophic to everybody around the globe.  But all of us will be affected by this phenomenon in one way or another.  How we decide to handle those changes will be the key.

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