Apparently @GeorgeMonbiot cannot read a scientific paper

This seems a little odd, no?

Or we could perhaps file this under the rubric of “Always read the footnotes”. That is, check what people are saying before we believe anyone trying to tell us what they’re saying.

The news is that the state of a crucial oceanic circulation system has been reassessed by scientists. Some now believe that, as a result of climate breakdown changing the temperature and salinity of seawater, it is more likely than not to collapse. This system – known as the Atlantic meridional overturning circulation (Amoc) – delivers heat from the tropics to the North Atlantic. Recent research suggests that if it shuts down, it could cause both a massive drop in average winter temperatures in northern Europe and drastic changes in the Amazon’s water cycles. This could help tip the rainforest into cascading collapse and trigger further disaster.

Amoc’s shutdown is likely also to cause an acceleration of sea level rise on the east coast of the US, threatening cities.

Well, OK, I’m in inland Portugal and have wood fires and electrical heating so I’ll be fine. What do I care if the AMOC closes down?

But that’s not the point here. Rather:

So why is this not all over the news? Why is it not the top priority for the governments that claim to protect us from harm? Well, in large part because oligarchic power has championed a model of climate impact that bears little relation to reality: that is, they have a hypothesis about how the world works that is completely detached from scientific findings. This model underpins official responses to the climate crisis.

It began with the work of the economist William Nordhaus, who sought to assess the economic effects of global heating. His modelling suggests that a “socially optimal” level of heating is between 3.5C and 4C. Most climate scientists see a temperature rise of this kind as catastrophic. Even 6C of heating, Nordhaus suggests, would cause a loss of just 8.5% of GDP. Climate science suggests it would look more like curtains for civilisation.

No, that’s not what he does say.

As the eminent economists Nicholas Stern, Joseph Stiglitz and Charlotte Taylor have argued, the mild effects Nordhaus forecasts are merely artefacts of the model he has used. For example, his modelling assumes that catastrophic risks do not exist and that climate impacts rise linearly with temperature. There is no climate model that proposes such a trend.

Sigh. So here’s the actual Nordhaus paper. This is the earlier, working, paper because NBER papers are widely available in a way that the version published later in a journal is not.

The current version of the DICE model continues to rely on existing damage studies. The method for estimating the damage function was the following: The new estimates started with a survey of damage estimates by Andrew Moffat and Nordhaus (2017). The underlying damage estimates were identified and collected. The survey turned up 27 studies which contained 36 useable damage estimates. For example, a recent version of the PAGE model estimated that the impact of a 4 °C warming would be to lower global output by 2.9%. Using those 36 estimates as data points, we then fitted a number of different specifications to the estimates. The central specification was a one-parameter quadratic equation with a zero intercept and no linear term and was therefore a one-parameter function. (The weighted OLS version had the highest damage parameter; it was followed by the weighted median regression that is used; while the unweighted least squares and unweighted median regressions have the smallest estimated damage coefficients. “Largest” here means most negative.) Because the studies generally included only a subset of all potential impacts, we added an adjustment of 25 percent of quantified damages for omitted sectors and non-market and catastrophic damages, as explained in Nordhaus and Sztorc (2013). Including all factors, the damage equation in the model assumes that damages are 2.1% of global income at 3 °C warming and 8.5% of income at 6 °C warming. A full discussion of the estimates and statistical analysis are available in Nordhaus and Moffat (2017).

The parameter used in the model was an equation with a parameter of 0.227% loss in global income per °C squared with no linear term. This leads to a damage of 2.0% of income at 3 °C, and 7.9% of global income at a global temperature rise of 6 °C.

This is an assumption of the model not a result of the model. If - note, IF - the assumptions of the model hold then the result will be…..

And a few paragraphs later we get well, what if the assumptions of the model do not hold?

It should be noted that the optimal policy depends crucially on the assumed damage function. If the damage function shows higher costs, or has sharp curvature at or around 2 °C, as is implicitly assumed in international policies that have a 2 °C target, then the revised optimal policy would have much higher abatement, and the temperature-limit and Stern policies would be much more economically attractive. However, current damage studies do not at present display either of these features (see Nordhaus and Moffat 2017).

Nordhaus actually says that if the damages are non-linear, as Stern suggests, then Stern is right - or perhaps righter - about policy.

How’s that for the oligarchic billionaires lying to us about climate change then?

One does have to wonder, eh? Can George actually read an economics paper?

As to why he isn’t doing so currently my assumption - and note it is only an assumption, of mine - is that Nordhaus insists we can deal with this through prices. Stick on the appropriate carbon tax and she’ll be fine. Sure, sure, we should have started some time agao - as I’ve long been saying - but modify markets to include the externality and markets will do the rest. George doesn’t want markets to do the rest, George wants the planned society. Therefore don’t actually grasp what Nordhaus is saying for fear that climate change will not be used as an excuse to abolish markets and capitalism. As I say, an assumption and quite possibly an unkind one but there we are.

But we do still need an explanation here. Why can’t George understand what Nordhaus is saying?