Wednesday, January 17, 2007

Stern Reveiw Crushed. Hmmmm......maybe not.

Denialists the world over are trumpeting the arrival of THE Stern critique, in which the Stern Review on the Economics of Climate Change gets its comeuppance.

Only that isn’t the case because, predictably, the critique is the same tired, debunked rubbish from the same shills: Bob Carter, Dick Lindzen, Ian Castles, Nigel Lawson, Ross McKitrick etc. Surely there must be some new crazies out there who can be found to put their name to this stuff.

Anyway, a little about the science.

The science section isn’t aimed at scientists, as anyone with a bit of knowledge of the field can easily pick the distortions, omissions and bizarre logic. It’s aimed squarely at the media, which hopefully by now will have learnt not to fall for it (though, unsurprisingly, the Climate Auditors have).

And which study gets a special mention in the critique, even earning a long quote in the text? Have a guess:
…the global warming observed during the latest 150 years is just a short episode in the geologic history. The current global warming is most likely a combined effect of increased solar and tectonic activities and cannot be attributed to the increased anthropogenic impact on the atmosphere. Humans may be responsible for less than 0.01°C (of approximately 0.56°C total average atmospheric heating during the last century).
Why, it’s none other than Khilyuk, L. F., and G. V. Chilingar (2006), perhaps the most mistake-ridden screed ever to pass peer-review. It has been fully debunked, and is an embarrassment to the authors, reviewers and the journal in which it was published, yet here it is forming a major part of the critique.

Ya gotta laugh at the gall of it.

Something else caught my eye (mainly because I saw Stephen Long’s presentation on this particular subject in Adelaide last year). It’s only a small section, but it encapsulates the approach taken in the entire critique.
Another source of the Review’s overestimates of future levels of hunger is its treatment of the prospective fertilisation of crops by additional carbon dioxide. The basis for this assumption, which flies in the face of numerous papers on the reality of carbon fertilisation, is a recent paper (Long et al., 2006), which suggests only that under field conditions, carbon fertilisation may be a third to less than half of what is suggested by experiments using growth chambers. The Review’s effective assumption of no carbon fertilisation, which is wholly unrealistic, allows it to make a headline projection that “250–550 million additional people may be at risk” of hunger, whereas, on its own figures, an assumption of strong fertilisation would have suggested declining numbers of hungry people, even for a temperature increase of up to 3.5 degrees C.
So, is there only one study that shows little CO2 benefit under field conditions? No.

FACE (free-air carbon enrichment) studies have been conducted on multiple crops at multiple sites by multiple research groups. This link shows the 50-odd papers published so far.

Do the FACE experiments show CO2 fertilization will be 1/3 to 1/2 of that suggested by growth chamber experiments? No.

This is roughly correct for C3 crops (though when combined with increased ozone, also due to fossil fuel burning, C3 crops decrease in yield). C4 crops actually show significantly less benefit again. Maize, which produces more grain than any other single crop on a world-wide basis, is a C4 plant.
Results from the open-field experiments, using Free-Air Concentration Enrichment (FACE) technology, “indicate a much smaller CO2 fertilization effect on yield than currently assumed for C3 crops, such as rice, wheat and soybeans, and possibly little or no stimulation for C4 crops that include maize and sorghum,”
The bit that makes me laugh the most is the statement that FACE experiments ONLY demonstrate increased CO2 loses its fertilisation effect under field conditions. Only, hey?

Imagine trying to sell this super-dooper CO2 fertilizer:

Nexus 6: “I’ve got this great new fertilizer that increases yields heaps.”

Farmer: “How much will it increase yields in my paddock.”

Nexus 6: “Not much, it may even decrease them. But it does wonders in the growth chamber.”

Farmer: “But I don’t grow my crops in the growth chamber.”

Nexus 6: “Oh.”

So why the difference between growth chamber and field? Because in growth chamber experiments, conditions are near-perfect and there are no additional limiting factors, allowing plants to fully utilise excess CO2. The results themselves are quite real; they just don’t represent the real world.

Liebig’s Law points to the reason why. Liebig's Law of the Minimum states that growth is controlled not by the total of resources available, but by the scarcest resource.

In the field, conditions are never perfect, with limitations in factors such as light, temperature, water, nitrogen, phosphorous etc., preventing the plant from taking full advantage of excess CO2. C4 plants use CO2 ‘more efficiently’ than C3 plants and, accordingly, show less response in the FACE experiments.

Everyone who has ever worked with growth chambers knows that experiments conducted in them are often unreliable indicators of how plants will perform in the field. Growth chamber experiments still have their value, but their limitations need to be understood.

So, for the critique to suggest that Stern should have ignored the field results and used the growth chamber results showing a strong fertilizer effect is preposterous. Stern is perfectly correct in this case, and the critique’s authors clearly full of it.

Who would have thought?