Understanding Climate Risk

Science, policy and decision-making

Feedback from Evans – there is no feedback

with 2 comments

After me getting an op-ed in The Age representing real climate science and policy, it’s time for some asshattery, c/- both the Melbourne Age and the Sydney Morning Herald. The Fairfax press has decided to redress the balance of knowledge with some agnotogeny* from Dr David Evans. From his tagline:

Dr David M. W. Evans is a mathematician and engineer who consulted full-time for the Australian Greenhouse Office (now the Department of Climate Change) from 1999 to 2005. He says he changed from being a warmist to a sceptic after ”evidence supporting the idea that CO2 emissions were the main cause of global warming reversed itself from 1998 to 2006”.

Cartoon by Fiona Katauskas

Oh purleeze.

Evans has gone to great effort to write this article, and he gets a lot wrong, so you have to admire that kind of effort.

Evans’ contention is that the positive atmospheric feedback that accompanies the direct warming effect of greenhouse gases doesn’t exist. That is, instead of warming 3°C if CO2 doubled for a 3°C sensitivity, Earth would only warm by 1°C. That restricts warming to the albedo effect where the extra energy is reflected by the planet contributes to warming with no feedbacks.

He maintains that CO2 would have contributed one-third of the historical warming if that was the case. This is not so. The  historical forcing from CO2 is 1.8 Wm2, equivalent to a temperature rise of 0.5°C. The earth has warmed by about 0.8°C since pre-industrial times. Total forcing of 1.8 Wm2, greenhouse gases minus aerosols is about the same.

But not all the heat produced stays in the atmosphere, most of it going into the ocean. The oceans cover 70% of the earth and they absorb around 90% of downward energy, releasing it over time. So genuine climate science would estimate an eventual range of 1–2.2°C at equilibrium after the oceans came into balance with the atmosphere, suggesting we have somewhere between 0.2–1.4°C to go if we kept the atmosphere as it is now, most of that coming out of the ocean.

But David Evans has another source of warming. He fingers the sun, but not solar energy entering the atmosphere because that is known currently to have a slight cooling effect, but its magnetic properties:

While the sun’s radiation is roughly constant, its magnetic field varies considerably. This field shields the earth from cosmic rays that, according to recent experiments at the world’s premier atom smasher CERN, might seed clouds. Clouds cool the planet, so if the sun’s magnetic field wanes, then it might get cooler here on earth.

Might seed clouds, might get cooler on earth. Let’s get this straight. The CERN experiment looked at the cloud nucleating agents of sulphuric acid and ammonia and concluded that they were at too low levels in the lower atmosphere to explain the level of nucleation known to be there. This isn’t actually new and it is known that there are other nucleating agents – this does need to be fixed, but we also know that influencing cloud nucleation is a plausible method of geoengineering. What they did find was that cosmic rays did influence nucleation but if this occurred in reality, it would be in the mid troposphere and above.

And here’s where Evans’ house of cards comes tumbling down. For cosmic rays to be influencing warming beyond that of the direct albedo effect of greenhouse gases, clouds need to be reducing or becoming less transparent over the recent historical period. Clouds also both cool and warm depending on their composition and height, so while it appears that cosmic rays do affect clouds on short-term scales, a mechanism has to be sought and found that produces secular changes over decadal timescales. And we haven’t observed this? Puhleeeze, Louise.

We also know that energy  in the form of heat is being stored in the ocean, causing a delay and release effect. Why? because the atmosphere can only store as much energy as the to 3m of ocean. The land only heats by small amounts, so most of the products of positive atmospheric feedbacks not apparent in the atmosphere will be in the ocean (some, a lesser amount, is taken up in the melting of ice).

The other thing Evans does is maintains that the positive feedbacks are assumptions in climate models supported by no observational evidence. In doing so, he ignores the palaeoclimatic evidence. Studies cannot reproduce Earth’s temperature without positive feedback. Measurements also do exist, and are consistent with theory and observations.

Risible attempts at discrediting science include:

  • Comparing recent rates of warming to IPCC projections made in 1990. Puhleeeze!
  • Maintaining the climate scientists rely on land temperatures when the three main global data sets are land and ocean. Puhleeeze!
  • Comparing initial ocean ARGO measurements to buckets as a pre-post 1983 phenomenon without acknowledging the ongoing improvements in ocean heat content and temperature measurements. Puhleeeze!
  • The tropical hot spot furphy. Puhleeeze! Why not mention the stratospheric cooling and tropospheric warming that is the footprint of anthropogenic warming – that you admit to.
  • He also brings up the point that short-term radiation at the top of the atmosphere decreases in models and increases in measurements. I don’t know about this one but I do know he has omitted to mention top of the atmosphere measurements that show a large existing deficit in balance due to anthropogenic forcing.

Are these points about disproving positive feedbacks? No they are not – they are the old set of saws trotted out to discredit all forms of climate science.

If Evans thinks that a lack of a warming trend in lock-step with CO2 since 1998 disproves the presence of feedbacks but admits to the direct influence of CO2 then what happened in 1998 with cosmic rays? We’ve had satellites all that time, David, so where are the measurements?

The ocean-atmosphere system is highly non-linear. The expectation that CO2 and global warming increase together without being influenced by the inherent non-linearity of ocean-atmosphere processes is totally counter to scientific understanding. The ocean runs the show. Atmospheric warming is strongly non-linear. Get used to it.

That the SMH and The Age have seen to print this rubbish is really disappointing. Print media can no longer afford science editors and it shows.

*Agnotogeny: the generation of ignorance.

Cartoon credit: Fiona Katauskas

More on the calculations in this post at Skeptical Science


Written by Roger Jones

August 2, 2012 at 10:29 pm

2 Responses

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  1. Did I miss something when I was on holiday – did Gina take over Fairfax after all?


    August 3, 2012 at 9:00 am

  2. Hi Roger
    I had a shot at this one also http://duggyvans.blogspot.com.au/2012/08/now-heres-fine-piece-of-serendipity.html as did Watching the Watchers Blog http://watchingthedeniers.wordpress.com/2012/08/02/fairfax-starts-trumpeting-rineharts-agenda-todays-op-ed-by-climate-crank-david-evans/ We both thought the Evans piece was to provide a bit of Rinehart inspired ‘balance’ to the the report of Richard Muller’s ‘Road to Damascus’ experience. I’d forgotten your op ed. You are probably right. It’s all in the name of feeding a spurious debate around the science. Shame on them!

    Douglas Evans

    August 3, 2012 at 11:37 am

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