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Grant McDermott

Data. Economics. Environment.

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Secondary subject line: The relative prices argument for strong action against climate change.

Paul Krugman must have been feeling more provocative than usual yesterday:
What’s behind the surge in food prices? The usual suspects have made the usual claims — it’s all about the Fed, or it’s all about speculators. But I’ve been looking at the USDA World supply and demand estimates, and what stands out from the data is mainly that we’ve had a huge global harvest failure.


Why is production down? Most of the decline in world wheat production, and about half of the total decline in grain production, has taken place in the former Soviet Union — mainly Russia, Ukraine, and Kazakhstan. And we know what that’s about: an incredible unprecedented heat wave.
Despite his later disclaimer about attributing any single weather event to larger trends in our climate, you have to credit Krugman for knowing how to rile the opposition. The implication that rising food prices (i.e. inflation) are the result of climate change \(-\) rather than the actions of Dark Lord Ben Bernanke and his evil minions \(-\) is enough to have caused brain explosions in conservative households across America. The only way that Krugman could have come up with a more unholy combination aimed at upsetting this particular constituency would be to suggest that Mao Zedong was directly descended from Jesus.

I don't really wish to get dragged into the merits of Krugman's argument here.[*] What I am interested in, however, is the idea that he touches on; how climate change could affect food prices. It got me thinking about one of the strongest arguments I have heard in favour of swift and decisive action against climate change: the role of relative prices.

The basic gist of the relative prices argument goes like this: Environmental goods and man-made goods are imperfect substitutes. With environmental goods expected to become "scarcer" as a result of climate change (increased drought, loss of biodiversity, etc), it follows that they will become more expensive in comparison with man-made goods. This will clearly impact our ability to generate future wealth and needs to be accounted for when we evaluate our best response to climate change. Indeed, incorporating this into our analysis strongly supports the notion that we should be looking at decisive action against climate change sooner rather than later.

The above ideas are neatly encapsulated in the following paper by Sterner and Persson: An Even Sterner Review - Introducing Relative Prices into the Discounting Debate. As I have said elsewhere, this might be the one paper that I would recommend everyone read to understand the basic arguments surrounding the economics of climate change. The authors do a great job in discussing the most salient aspects of the discount rate (which is central to much of what climate change economics is about) and the controversy surrounding different estimates by the likes of the Stern Review and his opponents, before adding their own contribution via the aforementioned relative prices twist. Seriously, have a look. It's not too long and very readable.[**] 

Anyway, I was thinking of all this when I read that Krugman post. I left a comment \(-\) lost among the many :'( \(-\) that included a quote from the above Sterner and Persson paper, which is very germane to the issue at hand:
"[G]lobal agriculture is said to represent 24 percent of global GDP (Stern Review, p. 67). A 1-percent loss of agricultural output might be estimated to reduce global GDP by.24 percent. Basic logic, however, tells us that a 50-percent loss of agricultural production would reduce global GDP by much more than 12 percent, and a 100-percent loss would reduce GDP by more than 24 percent of GDP. The mechanism behind this would be escalating food prices: As food became more and more scarce, its relative price would rise so fast that the dwindling food supplies would crowd out everything else and approach 100 percent of total GDP." (Pg. 68, emphasis added)
THOUGHT FOR THE DAY: Apart from being tremendously self-indulgent, one of the reasons I started this blog was because I wanted to try and act as an intermediary for ideas that I have come across in my field of specialisation (environmental and natural resource economics) and put them in a format that friends and non-specialists could easily access and debate. When it comes to the economics of climate change, reasonable people have argued that it makes sense to focus adaptation measures rather than attempting to reduce carbon output. Typically, this would involve the continued heavy use of fossil fuels in a bid to grow our economies as fast as possible so as put us in a better position to deal with any effects that climate change has. However, there are several reasons why I respectfully, yet firmly, disagree with this position. The impact that relative prices will have on our ability to create wealth is chief amongst these.

UPDATE: I have some follow-up comments about this relative prices issue, as well as the role of the discount rate in climate change economics here.
[*] For what it's worth, I think that we are going to see higher food prices generally in comparison to previous decades. In particular, the evidence points to a stronger link between the prices of energy and non-energy goods. This was a key driving factor during the 2006-2008 boom and, while the recession may have burst that particular bubble, I don't see any obvious reason why the fundamentals have changed.

[**] For those of you feeling up to it, the ever-impressive Christian Gollier has put forward a number of analogous, though far more technical papers on this subject... For example here and here. [Wonkish: By focusing on the "ecological discount rate", Gollier actually goes some way to merging the relative price argument with Weitzman’s uncertainty principal, before arriving at separate discount rates for biodiversity (1.5%) and consumption (3.2%). As some of you may recognise, the former is pretty much on par with Stern’s rate of 1.4%…]