Friday, 2 April 2021

Firm conclusions based on total guesswork

From The Guardian:

The climate crisis is already eating into the output of the world’s agricultural systems, with productivity much lower than it would have been if humans hadn’t rapidly heated the planet, new research has found.

Advances in technology, fertilizer use and global trade have allowed food production to keep pace with a booming global population since the 1960s, albeit with gross inequities that still leave millions of people suffering from malnutrition.

But rising temperatures in this time have acted as a handbrake to farming productivity of crops and livestock, according to the new research, published in Nature Climate Change. Productivity has actually slumped by 21% since 1961, compared to if the world hadn’t been subjected to human-induced heating.

And from itself:


Agricultural research has fostered productivity growth, but the historical influence of anthropogenic climate change (ACC) on that growth has not been quantified.

We develop a robust econometric model of weather effects on global agricultural total factor productivity (TFP) and combine this model with counterfactual climate scenarios to evaluate impacts of past climate trends on TFP. Our baseline model indicates that ACC has reduced global agricultural TFP by about 21% since 1961, a slowdown that is equivalent to losing the last 7 years of productivity growth.

The effect is substantially more severe (a reduction of ~26–34%) in warmer regions such as Africa and Latin America and the Caribbean. We also find that global agriculture has grown more vulnerable to ongoing climate change.

Is there any part of this whatsoever that doesn't scream 'total guesswork'? You can't just add up inputs and assume a linear rise in outputs. Your factors are land, water and sunshine, seeds, labour, machinery, other capital and fertiliser, it's all trade-offs. How on earth do you ascribe one set of relative values? Machinery will be used if it is cheaper than using labour, so you use more tractors in high-wage countries and more labour in low wage countries.

Using 'enough' fertiliser will get you an optimum result; there is no point using more than that because the extra yield does not justify the extra cost. And the extra yield depends on how much you can sell your produce for. All plants require a minimum amount of land to grow, although you can enhance that by building greenhouses and polytunnels etc.

Billions of farmers worldwide have been making these calculations since farming was invented and they seem to have got it right most of the time. Somehow or other, food production has always kept pace with population growth (by definition) and there's no reason to assume that this won't continue for the foreseeable future.

There used to be famines all the time, but there haven't been many in the past couple of decades apart from those imposed by governments (North Korea) or warfare. Sure, there are droughts, floods and outbreaks of pests now and then, here and there, always have been and always will, but you don't read about hundreds of thousands or millions of people starving to death like you did for most of the 20th century.

So sorry, really not bothered.


Bayard said...

"with productivity much lower than it would have been if humans hadn’t rapidly heated the planet,"

Interesting to see that we have gone beyond the "Project Fear" use of the conditional into the bald lie.

Dr Evil said...

Quite a few crops have been genetically engineered to withstand droughts/dry conditions and higher temperatures.

A K Haart said...

I agree with Bayard - it's a bald lie.

Bayard said...

DR E, that's not really the point. The climate has always changed over time and food growers have adapted. The vast majority of historic desertification is through abuse of the soil rather than climate change, whether global or regional.

Mark Wadsworth said...

B, to them, it is not a lie.

DrE, that's another good example. Selective breeding and GM-stuff.

AKH, ta.

B, I think it is the point, you seem to be saying the same thing. Even if climate is not changing, those new drought-resistant crops can be grown in new places where they couldn't be grown before. It's all good.

Bayard said...

"Even if climate is not changing, those new drought-resistant crops can be grown in new places where they couldn't be grown before"

Exactly, we need them anyway, so their development has nothing to do with AGW.

Mark Wadsworth said...

B, that's what I thought you meant.

But Dr E did not imply that this was WHY they are doing it, he merely pointed out that they ARE doing it.