Er, nothing? Joe Romm:
Last week economist William Nordhaus slammed global warming deniers and explained that the cost of delaying action is $4 Trillion. As I wrote, Nordhaus’s blunt piece — “Why the Global Warming Skeptics Are Wrong” – is worth reading because, like most mainstream climate economists, he is no climate hawk.
A key reason for that, I believe, is a chronic low-balling of future temperature rise and hence future climate impacts and hence future climate damages by the mainstream economic profession. Nordhaus’s piece proves that point. In his argument on why CO2 is a pollutant and negative externality—”a byproduct of economic activity that causes damages to innocent bystanders”– he writes:
The question here is whether emissions of CO2 and other greenhouse gases will cause net damages, now and in the future. This question has been studied extensively. The most recent thorough survey by the leading scholar in this field, Richard Tol, finds a wide range of damages, particularly if warming is greater than 2 degrees Centigrade.7 Major areas of concern are sea-level rise, more intense hurricanes, losses of species and ecosystems, acidification of the oceans, as well as threats to the natural and cultural heritage of the planet.
That highlighted sentence may strike some of you as a bit strange. After all, the chances that warming would be less than 2°C have been pretty small for quite some time even with aggressive action and essentially nonexistent without it. ...
[delete rant about a Richard Tol review paper*]
The mainstream economics community has a long way to go to catch up to the reality of emissions trends and climate science.
According to the USEPA, the 2007 IPCC says:
The average surface temperature of the Earth is likely to increase by 2 to 11.5°F (1.1-6.4°C) by the end of the 21st century, relative to 1980-1990, with a best estimate of 3.2 to 7.2°F (1.8-4.0°C) (see Figure 1). The average rate of warming over each inhabited continent is very likely to be at least twice as large as that experienced during the 20th century.
So, in the excerpt, Nordhaus seems to be saying that, even in a best-case scenario (2 degrees C), climate change will be bad. That seems like a reasonable thing to say to me. But in fact, Nordhaus later says this:
Restrictions on CO2 emissions large enough to bend downward the temperature curve from its current trajectory to a maximum of 2 or 3 degrees Centigrade would have large economic effects on many businesses.
Nordhaus says that only with climate policy will the temperature trend fall to what Joe Romm accuses climate economists of claiming is the business-as-usual trend. And Romm quotes Nordhaus' book where he discusses the economic effects of temperatures higher than 2C.
Me thinks Joe Romm hates economists too much.
*Update: Here is Tol's reasonable response and Romm's reply. The rest of the comments deserve a read. I'm sympathetic to the ones that are critical of benefit-cost analysis applied to climate change. High upfront costs with discounted benefits 50-100+ years away is not quite the right comparison.
Hat tip: Stand-up Economist