Skip to content

Overestimated global warming over the past 20 years

August 28, 2016
tags:

By Paul Homewood 

 

image

http://www.nature.com/nclimate/journal/v3/n9/full/nclimate1972.html

 

It’s three years old, but I don’t recall it at the time, and it’s still highly relevant:

 

 

Recent observed global warming is significantly less than that simulated by climate models. This difference might be explained by some combination of errors in external forcing, model response and internal climate variability.

Global mean surface temperature over the past 20 years (1993–2012) rose at a rate of 0.14 ± 0.06 °C per decade (95% confidence interval). This rate of warming is significantly slower than that simulated by the climate models participating in Phase 5 of the Coupled Model Intercomparison Project (CMIP5). To illustrate this, we considered trends in global mean surface temperature computed from 117 simulations of the climate by 37 CMIP5 models (see Supplementary Information).

These models generally simulate natural variability — including that associated with the El Niño–Southern Oscillation and explosive volcanic eruptions — as well as estimate the combined response of climate to changes in greenhouse gas concentrations, aerosol abundance (of sulphate, black carbon and organic carbon, for example), ozone concentrations (tropospheric and stratospheric), land use (for example, deforestation) and solar variability. By averaging simulated temperatures only at locations where corresponding observations exist, we find an average simulated rise in global mean surface temperature of 0.30 ± 0.02 °C per decade (using 95% confidence intervals on the model average).

The observed rate of warming given above is less than half of this simulated rate, and only a few simulations provide warming trends within the range of observational uncertainty (Fig. 1a).

The inconsistency between observed and simulated global warming is even more striking for temperature trends computed over the past fifteen years (1998–2012). For this period, the observed trend of 0.05 ± 0.08 °C per decade is more than four times smaller than the average simulated trend of 0.21 ± 0.03 °C per decade (Fig. 1b). It is worth noting that the observed trend over this period — not significantly different from zero — suggests a temporary ‘hiatus’ in global warming. The divergence between observed and CMIP5- simulated global warming begins in the early 1990s, as can be seen when comparing observed and simulated running trends from 1970–2012 (Fig. 2a and 2b for 20-year and 15-year running trends, respectively the current generation of climate models (when run as a group, with the CMIP5 prescribed forcings) do not reproduce the observed global warming over the last 20 years, or the slowdown in global warming over the past fifteen years. This interpretation is supported by statistical tests of the null hypothesis that the observed and model mean trends are equal, exchangeable with each other (that is, the ‘truth plus error’ view); or (2) the models are exchangeable with each other and with the observations (see Supplementary Information).

Differences between observed and simulated 20-year trends have p values (Supplementary Information) that drop to close to zero by 1993–2012 under assumption (1) and to 0.04 under
assumption (2) (Fig. 2c). Here we note that the smaller the p value is, the stronger the evidence against the null hypothesis. On this basis, the rarity of the 1993–2012 trend difference under assumption (1) is obvious. Under assumption (2), this implies that such an inconsistency is only expected to occur by chance once in 500 years, if 20-year periods are considered statistically independent. Similar results apply to trends for 1998–2012 (Fig. 2d). In conclusion, we reject the null hypothesis that the observed and model mean trends are equal at the 10% level.

image

  http://www.stat.washington.edu/peter/statclim/fyfeetal.pdf

 

The paper goes on to explore possible reasons for the divergence between observations and computer models, without coming to any conclusion.

But the message is loud and clear, that climate models have grossly overestimated the small amount of warming seen since 1993, and failed to account for the temperature standstill since 1998.

15 Comments leave one →
  1. August 28, 2016 11:23 am

    Reblogged this on Wolsten.

  2. August 28, 2016 11:34 am

    Reblogged this on Climatism and commented:
    97% of climate models say that 97% of climate scientists are wrong.

  3. Don B permalink
    August 28, 2016 11:34 am

    A John Fyfe paper from 2016:

    Nature: Making sense of the early 2000’s warming slowdown

    It has been claimed that the early-2000s global warming slowdown or hiatus, characterized by a reduced rate of global surface warming, has been overstated, lacks sound scientific basis, or is unsupported by observations. The evidence presented here contradicts these claims. – Fyfe et al.

    https://judithcurry.com/2016/02/24/nature-making-sense-of-the-early-2000s-warming-slowdown/

  4. August 28, 2016 1:05 pm

    ‘Overestimated global warming over the past 20 years’

    It was never going to be underestimated, was it?

  5. songhees permalink
    August 28, 2016 1:39 pm

    http://theclimatescepticsparty.blogspot.com/2016/08/climate-exit-clexit.html
    Latest book and documentary.
    ‘The Deliberate Corruption of Climate Science’.



    http://www.drtimball.com

  6. Oliver K. Manuel permalink
    August 28, 2016 1:41 pm

    Please see: Neutron repulsion – Powers beyond the dreams of scientific fiction: http://ierj.in/journal/index.php/ierj/article/view/409/386

    • 1saveenergy permalink
      August 28, 2016 2:10 pm

      Oliver,
      wish you’d give it a rest, you’re all over the place like a blóódy rash.

      I expect that’s what your kids thought as well…. need I say more.

  7. DaveO permalink
    August 28, 2016 4:09 pm

    This paper is the basis for Box 9.2 in AR5. If you read this paper then Box 9.2 you will see the similarities.

    http://www.climatechange2013.org/images/report/WG1AR5_Chapter09_FINAL.pdf

    Fyfe, Gillett and Zwiers are all long time IPCC insiders and Lead Authors. This was clearly a “made to order” paper for the IPCC to deal with the embarrassing hiatus. The main difference between this paper and Fyfe 2016 (linked above) is that the data has changed (big surprise). See Karl 2015.

  8. August 28, 2016 6:57 pm

    Figure 1 is actally worse than it seems. Recall the model parameters are tuned to best hindcast from YE 2005. So only 2006-2012 is forecast. The rest just shows how poorly they hindcast even when the fix is in.

  9. RAH permalink
    August 29, 2016 7:24 am

    “Recent observed global warming is significantly less than that simulated by climate models. This difference might be explained by some combination of errors in external forcing, model response and internal climate variability.”

    I would say the difference could easily be explained as resulting from liars lying.

  10. August 29, 2016 12:10 pm

    Climate “scientists” are clearly ignorant of the “GIGO” principle.
    “Garbage in, garbage out”.

  11. Markon permalink
    August 30, 2016 3:08 am

    “This difference might be explained by some combination of errors in external forcing, model response and internal climate variability.”

    Maybe, but it looks like outright fraud to me.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: