Tag Archives: Nature Climate Change

Correctly taken to task by two readers and some breaking news

I should have amended the previous post to say I mistrust unverified models.  Here are two comments

#1 Andyextance

  • “Leaving aside the questions of the reliability of models in different subjects, and whether all of your six reasons truly relate to models, I have one core question: Without models, how can we have any idea about what the future might hold? Models may not always be right – but as long as they have some level of predictive skill they can often at least be a guide.”

    Absolutely correct — it’s all about prediction, not plausibility.

#2 Former Bell Labs denizen

“And yet you board a commercial airliner without hesitation, freely trusting your life to the models of aerodynamics, materials science, control system theory, electronics, etc. that were used in designing the aircraft. Similar comments apply to entering a modern skyscraper, or even pushing the brake pedal on your automobile.
Perhaps what you are really saying is that you don’t trust models until their correctness is demonstrated by experience; after that, you trust them. Hey, nothing to disagree with there.”
Correct again
Breaking news
This just in — too late for yesterday’s post — the climate models have overestimated the amount of warming to be expected this century — the source  is an article  in
Nature Geoscience (2017) doi:10.1038/ngeo2973 — behind a paywall — but here’s the abstract
In the early twenty-first century, satellite-derived tropospheric warming trends were generally smaller than trends estimated from a large multi-model ensemble. Because observations and coupled model simulations do not have the same phasing of natural internal variability, such decadal differences in simulated and observed warming rates invariably occur. Here we analyse global-mean tropospheric temperatures from satellites and climate model simulations to examine whether warming rate differences over the satellite era can be explained by internal climate variability alone. We find that in the last two decades of the twentieth century, differences between modelled and observed tropospheric temperature trends are broadly consistent with internal variability. Over most of the early twenty-first century, however, model tropospheric warming is substantially larger than observed; warming rate differences are generally outside the range of trends arising from internal variability. The probability that multi-decadal internal variability fully explains the asymmetry between the late twentieth and early twenty-first century results is low (between zero and about 9%). It is also unlikely that this asymmetry is due to the combined effects of internal variability and a model error in climate sensitivity. We conclude that model overestimation of tropospheric warming in the early twenty-first century is partly due to systematic deficiencies in some of the post-2000 external forcings used in the model simulations.
Unfortunately the abstract doesn’t quantify generally smaller.
Models whose predictions are falsified by data are not to be trusted.
Yet another reason Trump was correct to get the US out of the Paris accords— in addition to the reasons he used — no method of verification, no penalties for failure to reduce CO2 etc. etc.  The US would tie itself in economic knots trying to live up to it, while other countries would emit pious goals for reduction and do very little. 
In addition, \ I find it rather intriguing that the article was not published in Nature Climate Change   –,http://www.nature.com/nclimate/index.html — which would seem to be the appropriate place.  Perhaps it’s just too painful for them.