Krugman Paints False Picture of Consensus Alarmism

Nobel laureate Paul Krugman wrote a lengthy article, “Building a Green Economy,” in last Sunday’s New York Times Magazine. Krugman is an able writer.  He laid out the textbook arguments on climate change from the problem-and-act perspective, and his fact-of-the-matter tone and apparent expertise no doubt misled many readers.

Although he technically said nothing demonstrably false, Krugman gives the impression that there is widespread consensus that drastic action is needed to avert catastrophic climate change. This is simply not true, and all we have to do is actually read the consensus reports to see that Krugman is misleading his readers.

Krugman’s Summary of the Climate Science

After giving a good summary of the standard issues in the economics of climate change, Krugman pauses to comment on what the natural scientists (as opposed to the economists) have to say on the subject:

This is an article on climate economics, not climate science. But before we get to the economics, it’s worth establishing three things about the state of the scientific debate.

The first is that the planet is indeed warming. [I]f you look at the evidence the right way ­— taking averages over periods long enough to smooth out the fluctuations — the upward trend is unmistakable: each successive decade since the 1970s has been warmer than the one before.

Second, climate models predicted this well in advance, even getting the magnitude of the temperature rise roughly right. While it’s relatively easy to cook up an analysis that matches known data, it is much harder to create a model that accurately forecasts the future. So the fact that climate modelers more than 20 years ago successfully predicted the subsequent global warming gives them enormous credibility. [Krugman page 3, emphasis added.]

Now Krugman’s summary above is either accurate or not, depending on how much error we will tolerate in the predictions. But fair enough, we’ll agree with Krugman that climate models 20 years ago predicted higher average global temperatures, and that’s indeed what we’ve experienced.

Yet look at the move Krugman makes two paragraphs later:

And this brings me to my third point: models based on this research indicate that if we continue adding greenhouse gases to the atmosphere as we have, we will eventually face drastic changes in the climate. Let’s be clear. We’re not talking about a few more hot days in the summer and a bit less snow in the winter; we’re talking about massively disruptive events, like the transformation of the Southwestern United States into a permanent dust bowl over the next few decades. [emphasis added.]

This is completely misleading. After establishing the rock-solid reliability of climate models that have made predictions 20 years out, Krugman changes his focus to “models based on this research” and then discusses their apocalyptic projections. But these aren’t the same models! It is simply not the case that there is a broad-based, modeling consensus on the imminent danger to the United States.

Yes, there are some alarming projections in new models; in one of his NYT op eds Krugman referred to recent work by a group at MIT. But to repeat, these alarmist projections do not have a 20-year track record; they are new projections that Krugman and other alarmists are pointing to, in order to say, “Things are worse than we thought!”

For one thing, to the extent that the 20-year projections have been verified (more or less), this is only true if we look at macro predictions such as globally averaged temperatures. It is not true that climate models have been developed which reliably predict local events (such as the temperature in the Southwestern United States) over a 20-year period. My point isn’t to suggest that these predictions are wrong, but merely to show that Krugman’s earlier point about forecasting reliability is largely irrelevant.

The Consensus Is Not Alarmist, Especially for the United States

I’m not asking the reader to take my word for it. Here is what the most recent Economic Report of the President [.pdf] had to say about the dangers of unmitigated climate change–meaning this is what they predict will happen if the government does nothing:

The…projected losses for the most likely range of temperature changes are relatively modest. For example, at the Intergovernmental Panel on Climate Change’s most likely temperature increase of 3°C for a doubling of CO2 concentration…the projected decline is 1.5 percent of GDP. [Box 9-2, p. 242, emphasis added.]

And even on the matter of American farmers, things are not as grim as Krugman led us to believe:

Although warmer temperatures may extend the growing season in the United States for many crops, large increases in temperature also may harm growth and yields…

That said, another study finds that expected changes in temperature in the United States will have a relatively small impact on overall agricultural profits (Deschênes and Greenstone 2007). Neither study accounts for the possible increase in yields from elevated carbon dioxide levels or the possible decrease in yields from increased pests, weeds, and disease.

Climate change is also likely to bring increased weather uncertainty. Extreme weather events—droughts and downpours—may have catastrophic effects on crops in some years. Growing crops in warmer climates requires more water, which will be particularly challenging in regions such as the Southeast that will likely face decreased water availability.

American farmers have substantial capacity for innovation and are already taking steps to adapt to climate change. For instance, they are changing planting dates and adopting crop varieties with greater resistance to heat or drought. They can also undertake more elaborate change. In areas projected to become hotter and drier, some farmers have returned to dryland farming (instead of irrigation) to help the soil absorb more moisture from the rain. How well the private sector can adapt to the effects of climate change and at what cost is still an open question. [Box 9-1, p. 241, emphasis added.]

Conclusion

Paul Krugman is a very smart guy, and has a gift for explaining technical issues in terms that the layperson can understand. Unfortunately, Krugman’s recent “summary” of the state of the climate science is very misleading. He makes it seem that only anti-empirical “deniers” can doubt that crisis is upon us, when in fact the case for climate alarmism is weak indeed.