Wednesday, April 16, 2014

Will Global Temperature Records Fall?

Much has been made of the so-called global warming "pause" or "hiatus", a term that has been used to describe the slowdown in the rate of increase of surface temperatures over the past 10–15 years.  As we have discussed in previous posts (e.g., Global Warming Hasn't Stopped), this period has been marked by continued warming of the ocean, melting of ice, and warming of the land surface, so there is every reason to expect a return to more rapidly rising surface temperatures in the future.

In addition, there is some potential that we will see a new global surface temperature record in 2014 or 2015.  It is looking increasingly likely that El Nino will develop this summer or fall, with some indicators suggesting that it could be a moderate or strong event.  

El Nino is characterized by relatively warm sea surface temperatures in the tropical Pacific Ocean which, along with other accompanying changes in atmospheric and oceanic circulations, typically leads to an increase in global temperatures.  Conversely, La Nina is associated with relatively cool sea surface temperatures in the tropical Pacific Ocean and a decrease in global temperatures.  This can be seen in the graphic below, which categorizes years based on El Nino (red), La Nina (blue), or neutral/other conditions (a.k.a., "No Nino").  
Source: NCDC
That categorization doesn't distinguish, however, between weak and strong El Nino events.  1998 was characterized by a very strong El Nino and it remains one of the warmest years on record.  Note what an outlier it was compared to the period in which it is embedded.  There has subsequently been only one El Nino Year (2010) and it was a weak one.  However, the most recent 10-year period is clearly the warmest decade in the instrumented record so it is quite likely that a moderate to strong El Nino will likely yield record global surface temperatures.  

In the above analysis, NCDC classifies a year as El Nino or La Nina based on the first three months of the calendar year.  This reflects that fact that El Nino and La Nina typically reach their peak strength during the Northern Hemisphere winter.  However, this also makes the categorization a bit more difficult since the peak El Nino/La Nina conditions often straddle the start/end of the calendar year.  For example, some classify 2010 as a La Nina year since there was a rapid transition from El Nino to La Nina conditions during the Northern Hemisphere spring and summer.  

On the other hand, there is often a lag of a few months between peak El Nino/La Nina conditions and the accompanying increase/decrease in global temperature anomalies.  This is why we might need to wait for 2015 for a record.  Alternatively, we could bag this calendar year crap and instead look at a 12-month period encompassing the peak El Nino/La Nina period.  Here's what the global temperature trend looks like for July-June average temperatures.

Source: NCDC
In this instance, the hottest year is 2010 (i.e., July 2009-June 2010), which includes the moderate 2009–2010 El Nino, followed by 2007, which was characterized by a transition from weak El Nino to neutral or very weak La Nina conditions, and then 1998, which featured the strongest El Nino on record.

All of this suggests that if we can get a moderate to strong El Nino to develop, we will probably see record setting global temperatures for some 12-month period if not the calendar year.  Perhaps even a weak El Nino will do the job.  We'll have to see how things come together in the coming months and see if there are any surprises, like a huge volcanic eruption to cool things off. 


  1. Put the y-axis on a scale of 1 degrees...the warming is but a small blip on a geological timescale. Nothing to see here.

  2. I am often asked about the impact of El Nino/La Nina on our ski seasons, and thus put up these 3 pages:
    Thus I've analyzed El Nino/La Nino not on a 12 month basis but on a November-April basis.

    With regard to both snowfall and climate the positive or negative status of the Pacific Decadal Oscillation has similar effects to El Nino and La Nina respectively. El Ninos tend to more frequent and/or stronger during positive PDO periods like the 1980's and 1990's while the La Ninas are more prevalent in the negative PDO periods like the 1970's and the past decade.

    The other point, as demonstrated in my first page above, is that El Nino/La Nina tends to stabilize during the July to January timeframe and to be at its least stable during the northern hemisphere spring. Therefore the August/September status tends to persist well into the winter and can be used as an overall predictor for the upcomoing ski season at the most sensitive areas.

    Due to historic instability El Nino/La Nina predictions made in April are next to useless. I've read there are some deep underwater temperature readings that fit with the same timeframe in 1997, but I'm skeptical as prior predictions made at this time of year have a random at best success rate.

    During our ski season the 2009-10 El Nino was moderate in strength, 7th strongest by MEI Index since 1950 but only about 40% of the strength of the extreme events of 1982-83 and 1997-98. It's not obvious to me that we can get much stronger than that during the PDO negative phase. 1972-73 was just slightly stronger than 2009-10, and the 4 El Ninos that are much stronger were all in the 1980's and 1990's.

    One of the tests of the climate models is how long it will take to have a year that "breaks out" significantly above the levels of 1998, 2005 and 2010. The current flat period is already approaching the 95% confidence lower boundary of projections done in the late 1990's.

    I believe in the warming effect of greenhouse gases, but I am highly skeptical of the large positive multiplier effects in the climate models. Temporary cooling effects like PDO and perhaps solar influences are likely offsetting the greenhouse effect in the intermediate term of the past 10-15 years and there was a similar flat period from 1940-1970. When other effects than GHG are neutral or positive, then temperatures are likely to resume rising at a moderate rate similar to the 1980's and 1990's.