Climate Change: The Problem of Sources

Figuring out entirely by yourself the costs and benefits of climate change is impossible. All of us, including the professionals in the field, are dependent on second hand information. An economist or agronomist trying to estimate the costs of climate change depends on someone else’s estimate of how much change there will be and with what its effects. A climate scientist deciding whether human production of CO2 is the cause of climate change is dependent on, among others, paleoclimate researchers who produce proxy evidence that the current rate of global warming is unprecedented in the periods for which they have good proxies.

The ordinary layman faces a second level of dependence on other people. Combining the evidence produced by the professionals in the field is a hard problem. In practice almost everyone with an opinion on the subject is basing that opinion on evaluations of the evidence by other people.

I tried to look at the evidence for myself and concluded that we do not know enough to have confidence in the size, or even the sign, of the net effects of climate change, that it might make us worse off, might make us better off. In trying to persuade other people of that conclusion I face the problem that most of the authoritative sources they rely on confidently predict that the effects will be negative and significant. One way of dealing with that problem is to show my work, try to sketch the arguments that led me to my conclusion, as I did in my first post here.

One problem with that approach is that, for an issue that complicated, someone can reasonably reject my argument on the grounds that it is incomplete, omitted important considerations which would change the conclusion, justify the currently orthodox conclusion. I was reminded of that problem when a reader of my substack linked to my first post as a comment on the most recent thread on Astro Codex Ten, Scott Alexander’s substack, and several commenters indignantly rejected its conclusion.

An alternative approach is to attack not the conclusion but the sources of information on which other people base their beliefs. If I can show that the sort of authoritative sources they rely on for information on the effects of climate change cannot be trusted, are demonstrably biased, incompetent, or dishonest, that eliminates the basis for their present beliefs. They must then either shift to agnosticism, conclude that they do not know what the consequences of climate change will be, or do what I have done, try as best they can to put together whatever facts they believe they can trust to reach their own conclusion.

If a source of information is badly biased, incompetent or dishonest, demonstrating the fact is easier than demonstrating that its conclusion is wrong. Here are some examples:

Rennert et al. 2022 is a recent Nature  article that estimates the cost due to an additional ton of CO₂ being released, concludes that it is more than three times as high as the value calculated under the Obama administration and currently used by the EPA for regulatory decisions. It is being considered by the EPA as a possible basis for future decisions. I claim that its conclusions depend, among other things, on the implicit assumption that there will be no change in most of the relevant technologies, including medicine and biotech, for the next three centuries. My critique.

Introduction to Modern Climate Change is a climate science textbook sufficiently successful to be in its third edition. I claim that it contains demonstrably false statements obvious to a critical reader as well as a badly biased selection of true statements. My critique.

William Nordhaus is an economist who got a Nobel prize for estimating the costs of climate change. In a 2012 piece in the New York Review of Books arguing that climate change was an urgent problem he reported his estimate of the cost of doing nothing about it for the next fifty years as $4.1 trillion and added that “wars have been started over smaller sums.” He did not mention that $4.1 trillion, spread over the rest of the century, was equivalent to reducing global GNP by about .06%. Link.

My arguments in all three cases are much simpler and easier for the reader to check than my arguments on the consequences of climate change. That Nordhaus wildly exaggerated the implication of his own research you can check by reading what he wrote about the cost of waiting, looking up global GNP, and dividing. Checking the other two requires a little more work but not a lot and I provide the necessary links.

Consider the implications if my claims are true. An article published in Nature has been through peer review. Either it did not occur to any reviewer that improvements in medical technology over the next three centuries would have some effect on how many people died from warmer temperatures or the reviewers noticed but said nothing or reviewers pointed out the problem and the authors and journal editors ignored it.

A textbook that has been out for more than ten years and successful enough to be in its third edition has been looked at and used by many professors. Either none of them noticed multiple obvious mistakes, all biasing the conclusion in the same direction, or they did not think it worth reporting them to the author, or he did not think it worth correcting them. Either Nordhaus did not bother to do the arithmetic to determine the implications of his own research or he deliberately misrepresented them.

The conclusion is that the mechanisms for providing reliable information about the consequences of climate change are badly broken, that sources of information that satisfy the obvious criteria for reliable authorities are quite likely to say things that are not true.

One response, if you find this convincing, is climate agnosticism. You now know that you do not know what the net effects of climate change are likely to be. The alternative is to try to do what I have tried to do, work out for yourself what the implications of the evidence are.

You cannot, as I could not, establish the basic facts for yourself. That was a project that required the work of thousands, of researchers over many years. You need to find sources you can rely on for the facts on which to base your conclusions. In doing so, you can use the same approach I have used to find sources you cannot rely on, evaluate sources of information on internal evidence and consistency with other sources, then get your information from ones that pass that test.

I believe the IPCC reports qualify. The body of the reports appears to be honest if mildly biased, inclined to pay more attention to costs of climate change than to benefits. The Summary for Policymakers, which is all most will read, is more biased and mildly dishonest, but you don’t have to rely on it.

I have two reasons to believe the body of the report is honest. The first is that it quite frequently reports facts that undermine the conclusion that climate change is a bad thing, although those facts rarely show up in news stories. One example is the fact that some projections show climate change resulting in greening the Sahara and Sahel. Another is that the globe overall is greening, increasing the area of leaves, probably as a result of CO₂ fertilization. A third is that the total number of tropical cyclones is projected to decrease as a result of climate change.

A good many years ago I noticed that defenders of the current orthodoxy claimed that past IPCC projections of global temperature had turned out to be correct, critics that they had turned out to be wrong, so decided to check the claim for myself. I looked through each of the early reports, figured out what I would expect future temperature change to be if it were right, compared it to actual temperature change thereafter.

When I originally did it, in 2014, my conclusion was that the IPCC consistently overpredicted temperature change. When I redid the calculations seven years later, that was no longer the case. The projections were high three times out of four, low once, and only once was actual warming below the predicted range. I think that is consistent with random variation, a second reason to conclude that the reports are reasonably honest, since overpredicting is an obvious way of scaring people into doing something about climate change, which the IPCC is obviously in favor of.

Even if the projections are not biased how much do they tell us? To answer that question I compared the projections from each of the first four reports with the result of a straight line fit to the data starting in 1965, when warming resumed after the mid-century pause, and ending  the year of that report.

The straight line fit beat the IPCC projection four times out of four.

My conclusion is that the IPCC is not trying, or not trying very hard, to bias their results, but also that the complicated models they use for temperature projections don’t tell us very much. I have accordingly done my own calculations taking facts and projections from the body of the IPCC report as honest, in most cases the best information available to me, but no more than that.

For anyone who would like to see a broader sample of my work, both critiquing sources and trying to draw conclusions, much of it has been on my blog. I also have a collection of webbed chapter drafts for a future book dealing with climate and a variety of other issues; I expect some will eventually appear here. One of the reasons I am doing a substack is to get criticism and comments on things I expect to include in a future book.