'Pause', Long term Cooling, Or selectivity within Still warming trend?

  1. mbig
    Until more time has passed we won't know for sure.
    Before it does we have selective use/abuse of statistics to 'demonstrate' that 1998-2012 was a viable start of a reversal to 20th Century Warming.

    Who Created the Global Warming "Pause"? | Mother Jones
    Hat Tip: ThreeGoofs'

    "..This has occurred despite the fact that claiming that global warming has "paused" is deeply misleading. The IPCC explained as much in its just-released report, where it noted that although the rate of warming is somewhat smaller over the last 15 years, selectively seizing on this period, from 1998-2012, basically represents a case of bad statistics.

    After all, the year 1998 was a Record temperature year, due to a strong El Niño. So by making it the first year of an analysis you're stacking the deck. "If you shift just 2 years earlier, so use 1996-2010 instead of 1998-2012, the trend is 0.14 C per decade, so slightly Greater than the long-term trend," explains Drew Shindell, a climate scientist at NASA who was heavily involved in producing the IPCC report. This is why climate scientists generally don't seize on 15 year periods and make a big thing about them."""

    Graph I previously posted.
    They're Still 'Going Down the Up Escalator'
  2. longview
    I would like to start with as raw as data as possible.
    This one from Nasa seems good, although I wonder about how they eliminated outliers.
    GLOBAL Land-Ocean Temperature Index in 0.01 degrees Celsius base period: 1951-1980

    sources: GHCN-v3 1880-08/2013 + SST: ERSST 1880-08/2013
    using elimination of outliers and homogeneity adjustment
    Notes: 1950 DJF = Dec 1949 - Feb 1950 ; ***** = missing
    It is a standard practice to amplify data to more effectively see changes,
    I think the gain of 100 works good, but some may misinterpret the changes as being greater than they are.

    Divide by 100 to get changes in degrees Celsius (deg-C).
    Multiply that result by 1.8(=9/5) to get changes in degrees Fahrenheit (deg-F).

    Best estimate for absolute global mean for 1951-1980 is 14.0 deg-C or 57.2 deg-F,
    so add that to the temperature change if you want to use an absolute scale
    (this note applies to global annual means only, J-D and D-N !)

    Example -- Table Value : 40
    change : 0.40 deg-C or 0.72 deg-F
    abs. scale if global annual mean : 14.40 deg-C or 57.92 deg-F
    I remember in the late 80's Apple had a Star field demo, which clearly had more stars in the northern
    hemisphere. The reason was that there were more astronomers in the northern hemisphere.
    I compared The January to July Temps, Nothing stood out.
    (This format does not seem to let me place a jpeg direct.)

    From the giss graph both hemispheres show a leveling off.
    Keep in mind because of the gain of 100, all of the data is within the noise,
    So any guesses, are just that guesses.
  3. LowDown
    Of course, the emphasis is on the most recent 15 or so years because that's the period that includes the present.

    I agree that calling it a pause is a little misleading because we don't know for sure whether or not the warming will ever resume at the previous rate.

    Starting off with the El Nino does stack the deck somewhat, but consider also that just prior to that there had been a period of cooling from Mt. Pinatubo. Remove that and the pause might extend back 2 or 3 more years.

    But to get around to what I think the pause represents some background is necessary:

    The last 20 years is also important because that's the period of time in which the climate model predictions from earlier iterations of the IPCC report are being prospectively tested. And they are not doing well at all. Real world temperatures have fallen well below the predictions of most of the computer climate models. Whether or not you agree that the last 15 years have shown no warming this failure of the models is significant. The IPCC expected the temperatures to go one way and they went the other. This calls the theory behind the model into question.

    There was one model that got the last 20 years right, though. That was the model published in 1938 by G.S. Callendar. It was a dimensionless climate model based on CO2 forcing and with no water vapor feedback. His model predicts a climate sensitivity of 1.9. Since 1900 atmospheric CO2 levels have gone up by about 100 ppm which is 37% of the way toward doubling. During that time temperatures have gone up by about 0.75 degrees C. Callender's prediction was it would go up by 0.70 degrees (extrapolating from his tables). Callender's prediction for the past 20 years would have been an increase in temperature of 0.28. The actual increase was 0.25. The average prediction of the computer models was an increase of 0.5.

    The period from about 1940 to 1975 was what gave rise to speculation about catestrophic global cooling because for 35 years temperatures went down. Prior to that the period of 1910 to 1940 there was a run up in temperature that looks almost identical, adjusting for baseline, to the period between 1975 and 1996. Step back from this graph of temperatures from 1900 to the present, and it looks a lot like natural variation superimposed on a modest warming trend of 0.09 degrees C per decade for the past 100 years.

    So it may be that the "pause" and the increase in temperature that came before it between 1975 and 1996 is natural variation superimposed on a more modest warming trend. That would mean no catestrophic global warming for the foreseeable future.
  4. Threegoofs
    Odd. I've seen that graph a hundred times in the denier threads. Non peer reviewed, from a creationist. They never seem to show this one that comes from Real Climate.

    I also find this, which shows the numbers arent too shabby. Of course, the Ridley scenario is the implausible (there isnt any warming above the trend) skeptical one.

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