The Visual Display of Quantitative Information II

Conor Clarke accepts that:

I think Jim Manzi and others are right to say — if you believe the IPCC and CBO — that the U.S. won’t experience a climate-induced decline in GDP until 2080 or 2100.

But Conor goes on to argue that the costs that Waxman-Markey is expected to impose on American consumers by 2050 – about $1,1,00 per household per year, or a little less than 1% of total consumption – are pretty trivial, because we should expect to be so much richer by then. (I’ll note in passing that, as per my posts on this, there are very good reasons to believe that the EPA cost estimate is low, and also that costs are also virtually certain to rise between 2050 and roughly 2100 when we would expect to start getting some offsetting benefits.)

He then shows a chart making the point, basically, that 1% is a small fraction of 100%. But of course, this cuts both ways. We hear constantly about the existential threat posed by global warming – Cities underwater! Drought! Famine! Think about his graphic. The expected benefits don’t even outweigh these costs. That ought to make you stop and think.

But, you might say, that is because we are taking a parochial view that only looks at the U.S. and only the next several decades (which is a pretty broad definition of parochial). We need to consider our actions as stewards of the entire planet over at least a century. OK, let me do a very simple chart for you, built from a list of simple, validated assumptions:

1. Secular long-term global growth in real per capita consumption before considering any effects of global warming is about 1.3% per year. (This is a standard conservative estimate; it has averaged about 2.5% per year over the past half century).

2. Unrestricted global warming produces a global temperature change of 4C within a hundred years (which is quite aggressive, a better middle-of-the-road estimate is about 3C).

3. Economic damages from this temperature increase are equal to 5% of GDP (which is the top end of IPCC’s estimated range for 4C of warming).

The following chart shows what income an average person on earth has today, plus the same number in constant dollars for (i) 2110 with unrestricted global warming, and (ii) 2110 if we somehow magically eliminated all damages from global warming for the entire world at zero mitigation cost, labeled “2110 w/ no AGW”.

The expected impacts of human-induced climate change are marginal as compared either to the sloppy, sentimental and self-righteous rhetoric that surrounds this issue, or as compared to the potential reduction in global material well-being that would likely be created by ham-fisted attempts to substitute political allocation of resources for markets.