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El Niño and La Niña Redefined

11:21 am in Uncategorized by WeatherDem

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.

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

10:12 am in Uncategorized by WeatherDem

According to data released by NASA and NOAA this week, 2012 was the 9th or 10th warmest year (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.

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

9:49 am in Uncategorized by WeatherDem

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.

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NASA & NOAA: June 2012 Was 4th Warmest On Record

7:38 am in Uncategorized by WeatherDem

According to data released by NASA and NOAA this week, June 2012 was the 4th warmest June globally on record.  NASA’s analysis produced the 4th warmest June in its dataset; NOAA recorded the 4th warmest May in its dataset.  The two agencies have slightly different analysis techniques, which actually helps to reinforce the results from each other.

The details:

June’s global average temperatures were 0.56°C (1.01°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 June 2012).  The past three months have a +0.59°C temperature anomaly.  And the latest 12-month period (Jul 2011 – Jun 2012) had a +0.52°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 normal, 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 June 2012 from NASA.

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NASA & NOAA: April 2012 Among Top 5 Warmest On Record

8:33 am in Uncategorized by WeatherDem

According to data released by NASA and NOAA this month, April 2012 ranked among the top 5 warmest Aprils on record: NASA recorded the 4th (tied) warmest April in its dataset; NOAA recorded the 5th warmest April in its dataset.  The two agencies have slightly different analysis techniques, which actually helps to reinforce the results from each other.

The details:

April’s global average temperatures were 0.56°C above normal (1951-1980), according to NASA.  The warmest regions on Earth are exactly where climate models have been projecting the most warmth to occur for years: high latitudes (especially within the Arctic Circle in April 2012).  The past three months have a +0.47°C temperature anomaly.  And the latest 12-month period (May 2011 – Apr 2012) had a +0.49°C temperature anomaly.

According to NOAA, April’s global average temperatures were 0.65°C (1.17°F) above the 20th century mean of 13.7°C (56.7°F).  NOAA’s global temperature anomaly map for April reinforces the message: high latitudes continue to warm at a faster rate than the mid- or low-latitudes.  The extreme 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,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 the methane signal for many more years.

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

7:37 am in Uncategorized by WeatherDem

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. Read the rest of this entry →

Climate Change Basics – Energy & Projections

9:47 am in Uncategorized by WeatherDem

It’s been since August that I last wrote a post here because I was in graduate school full time.  While exhausting, I was exposed to and learned a great deal of information.  I wanted to continue a series I started last summer before delving into some highlights of what I think is important to this community.  The type of things I will talk about will seem very pessimistic at first, but I hope to relay the optimism that I do find in this complex topic.  As always, questions and feedback are appreciated.

In July, I wrote a post that laid the groundwork for the discussion of climate change basics: Gases, Forcing & Surface Temperature. This post follows onto that initial post by discussing energy within Earth’s climate system. As in that post, I will focus on the results in the IPCC’s AR4. There is a wealth of additional results in the scientific literature since the 2007 Report and I will share some of those in future posts. In other words, the IPCC information will be used as a baseline.

Energy Content

First, here are two views of the energy content in the climate system. The first is from the IPCC’s WGI Technical Summary:

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Source: IPCC AR4 Technical Summary Figure TS.15. Energy content changes in different components of the Earth for two periods (1961-2003 (blue) and 1993-2003 (burgundy)).

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East Coast Heat Wave Preview Of New Normal

6:35 am in Uncategorized by WeatherDem

heatwave sunset; Astoria Park

heatwave sunset; Astoria Park by Global Je


Readers of my posts should know by now I have been moving away from using certain language when discussing climate change effects.  That language includes talking about effects in the far-off future and the uncertainty involved with climate projections (even though they do exist).  This transition has happened rapidly as I have read hundred of journal articles detailing the latest science assessments as well as seminal reports like the IPCC’s in 2007.  Generally speaking, the American public has no idea what is about to hit them.  A solid percentage think climate change is occurring and our species is now the dominant forcing mechanism.  That’s the good news.  The bad news is far too few Americans realize how quickly conditions are changing and what those changing conditions mean for their future.

An article came out today putting some pieces together that I want to comment on.  The article covers the topic of a new paper being published in Climatic Change Letters by a Standford group.  It deals with projections of summer conditions around the globe, using the current heat wave affecting a good portion of the country as context.  That’s not to say this heat wave can be directly and completely attributed to climate change, but that conditions are primed for heat waves like this to occur with climate change affecting baseline conditions.  Unsurprisingly, the group found (among other things) the following:

The Stanford study’s lead author, Noah Diffenbaugh, sought to determine when the current hottest temperatures would become “the new normal.” He says, “According to our projections, large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years.”

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2010 Warmest Year On Record, Says NASA & NOAA

4:27 pm in Uncategorized by WeatherDem

The news is in and it isn’t good. Despite a strong La Nina during the second half of the year and cold air able to escape the Arctic and affect Europe and the eastern U.S., 2010 was the warmest year since 1880.

The top-10 warmest years in the NASA record are now:

2010, 2005 (actually 0.018°F less than 2010), 1998, 2002, 2003, 2006, 2007, 2009, 2004 and 2001.

9 out of the 10 warmest years on record have now all occurred since 2002. The 12 warmest years on record have occurred since 1997. Global warming has not stopped. Global warming will not stop unless and until we stop polluting the climate system with greenhouse gas emissions at a tiny fraction of our current pace.

NOAA has put together their annual global report, which acts as confirmation of the NASA result: 2010 is statistically tied with 2005 as the warmest year in their dataset.

To the climate zombies that infest the discussion over what to do about global warming, consider the following: 2010 was “only” 1.12°F (0.62°C) above the 20th century average of 59.0°F. Our current emissions trajectory is closest to the A1FI emissions scenario in the IPCC’s SRES family. Results of running that scenario through climate models produced the following results: best estimate temperature rise of 7.2°F with a likely range of 4.3 to 11.5°F (4.0 °C with a likely range of 2.4 to 6.4 °C).

Multiple extreme weather events also characterized 2010 and continue to do so in early 2011. From a heat wave worse than any seen in the past few thousand years across eastern Europe and Russia that claimed many lives and spawned massive wildfires to related Pakistani floods that affected tens of millions of people to floods in Australia that cover more area than several countries in Europe, loaded die are starting to land. The costs of these disasters already reach into the tens to hundreds of billions of dollars. If these kinds of horrific events are already occurring with only 1.12°F warming, what will happen when the globe warms by an average of 4.3°F, 7.2°F, or even 11.5°F? It can be summed up simply: stress will move beyond impacting disparate societies; our civilizations will be stressed to breaking points, to say nothing of ecosystems across the planet.

Cross-posted at WeatherDem – the blog.