Sunday, August 17, 2014

New paper: "explanations of the so-called ‘warming hiatus’ remain fragmented & implications...unclear"

A new paper published in Nature Geoscience finds excuse #32 for the 18 year "pause" in global warming that sophisticated IPCC climate models failed to predict. According to the paper, the IPCC models didn't predict the pause because they are too complex, but if a model with "reduced complexity" and the already known changes of natural variability is used, all is well.

The simpler model uses observations of ENSO, solar activity, and stratospheric aerosols to retrospectively predict the known climate change, not nearly as challenging as making a true prospective prediction of climate change before the natural variability is known.

The authors state, "the explanations of the so-called ‘warming hiatus’ remain fragmented and the implications for long-term temperature projections are unclear," but that their less complex model including a greater role for natural variability explains the "pause."



Natural variability, radiative forcing and climate response in the recent hiatus reconciled


Nature Geoscience
 
 
doi:10.1038/ngeo2228
Received
 
Accepted
 
Published online
 
Global mean surface warming over the past 15 years or so has been less than in earlier decades and than simulated by most climate models1. Natural variability234, a reduced radiative forcing5,67, a smaller warming response to atmospheric carbon dioxide concentrations89 and coverage bias in the observations10 have been identified as potential causes. However, the explanations of the so-called ‘warming hiatus remain fragmented and the implications for long-term temperature projections are unclear. Here we estimate the contribution of internal variability associated with the El Niño/Southern Oscillation (ENSO) using segments of unforced climate model control simulations that match the observed climate variability. We find that ENSO variability analogous to that between 1997 or 1998 and 2012 leads to a cooling trend of about −0.06 °C. In addition, updated solar and stratospheric aerosol forcings from observations explain a cooling trend of similar magnitude (−0.07 °C). Accounting for these adjusted trends we show that a climate model of reduced complexity with a transient climate response of about 1.8 °C is consistent with the temperature record of the past 15 years, as is the ensemble mean of the models in the Coupled Model Intercomparison Project Phase 5 (CMIP5). We conclude that there is little evidence for a systematic overestimation of the temperature response to increasing atmospheric CO2 concentrations in the CMIP5 ensemble.

3 comments:

  1. Looks like the modelers are finally being forced by nature to take into account some of the natural variability. It might at some time occur to them to take into account all of the natural variability as seen in the quasi - periodicities in the temperature record itself - in particular the quasi millennial periodicity. Perhaps it would help their mind set if they thought of reality as a virtual computer which accurately parameterizes all their differential equations .
    For forecasts of the coming cooling based on the millennial and 60 year cycles in the temperature see the latest post at
    http://climatesense-norpag.blogspot.com
    Here is a summary of the latest conclusions and update,

    "In earlier posts on this site http://climatesense-norpag.blogspot.com at 4/02/13 and 1/22/13
    I have combined the PDO, ,Millennial cycle and neutron trends to estimate the timing and extent of the coming cooling in both the Northern Hemisphere and Globally.
    Here are the conclusions of those posts.
    1/22/13 NH Forecast
    1) The millennial peak is sharp - perhaps 18 years +/-. We have now had 16 years since 1997 with no net warming - and so might expect a sharp drop in a year or two - 2014/16 - with a net cooling by 2035 of about 0.35.Within that time frame however there could well be some exceptional years with NH temperatures +/- 0.25 degrees colder than that.
    2) The cooling gradient might be fairly steep down to the Oort minimum equivalent which would occur about 2100. (about 1100 on Fig 5) ( Fig 3 here) with a total cooling in 2100 from the present estimated at about 1.2 +/-.
    3) From 2100 on through the Wolf and Sporer minima equivalents with intervening highs to the Maunder Minimum equivalent which could occur from about 2600 - 2700 a further net cooling of about 0.7 degrees could occur for a total drop of 1.9 +/- degrees.
    4) The time frame for the significant cooling in 2014 - 2016 is strengthened by recent developments already seen in solar activity. With a time lag of about 12 years between the solar driver proxy and climate we should see the effects of the sharp drop in the Ap Index which took place in 2004/5 in 2016-17.
    4/02/13Global Forecast
    1 Significant temperature drop at about 2016-17
    2 Possible unusual cold snap 2021-22
    3 Built in cooling trend until at least 2024
    4 Temperature Hadsst3 moving average anomaly 2035 - 0.15
    5 Temperature Hadsst3 moving average anomaly 2100 - 0.5
    6 General Conclusion - by 2100 all the 20th century temperature rise will have been reversed,
    7 By 2650 earth could possibly be back to the depths of another little ice age.
    8 The effect of increasing CO2 emissions will be minor but beneficial - they may slightly ameliorate the forecast cooling and help maintain crop yields .
    9 Warning !! There are some signs in the Livingston and Penn Solar data that a sudden drop to the Maunder Minimum Little Ice Age temperatures could be imminent - with a much more rapid and economically disruptive cooling than that forecast above which may turn out to be a best case scenario."

    3.2 2014 Updates and Observations..

    3.2.1 Updates
    a) NH Forecast- item 4. With regard to timing, closer examination of the Ap Index (Fig13) and Neutron Count (Fig.14) would suggest that the sharpest drop in activity is better placed at 2005/6 with the associated sharp temperature drop now forecast at 2017-18.
    b) Global Forecast - item1. Significant temperature drop now forecast for 2017-18.
    c) Global Forecast - item 9. Another year of flat Livingston and Penn umbral data suggests that a swift decline into a Maunder Minimum is now very unlikely.

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  2. Ah, so they have found that if you do a simple model which includes full solar forcing and the effect of the 60 year ocean cycle you can correctly match the temperature record?

    Well blow me down with a feather.

    Its what we've been saying for years and years. My model is still working very well.

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    Replies
    1. Nice,

      and here's a really really simple model Sunspots+AMO+PDO that correlates 96% with global temperatures:

      http://hockeyschtick.blogspot.com/2010/01/climate-modeling-ocean-oscillations.html

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