The Intergovernmental Panel on Climate Change (IPCC) has just produced their sixth report. This report builds on their previous work, and the current version (AR6) is the product of 234 scientists from around the world. This is essentially an update from their previous reports, taking into account all new evidence that has come to light. You can read the full report, or the executive summary for policymakers, or if you want more detail, the technical summary. Many news outlets, like the BBC, have also put out a highlight summary of their own.

I am not going to produce my own summary, just read the executive summary if you want the details. It’s only 39 pages. Instead, I am going to make some general observations.

First, for those who say there is no such thing as consensus in science, you are straight-up wrong. That is a strawman and denialist talking point. The strawman is the ubiquitous talking point that science is not determined by consensus. Of course it isn’t – consensus is determined by the science. The IPCC report is a great example of what consensus in science means – 234 experts pour over all the available evidence and then hash out a joint statement about what that evidence says. Next to each and every point there is a confidence notation, which they quantify – unlikely, likely, very likely, etc., with percentage confidence indicated for each notation. They are acknowledging the uncertainty, which torpedoes another strawman, equating consensus with certainty, or that the science is “settled” or that further research or debate is being shut down. This is all nonsense. The IPCC is simply a list of specific scientific statements, with a summary of the current evidence and degree of confidence.

If you disagree with the conclusions of the IPCC report, then you should have a very good reason. You need to fairly and completely represent the evidence, and indicate specifically why the IPCC report is wrong or misleading. Contradicting 234 world experts requires that you yourself have a high level of expertise and technical topic knowledge, not just regurgitated cherry-picked talking points from biased sources. Citing single outlier experts is also not enough. There are outliers in every discipline.

Keep in mind, I myself have contradicted consensus reports, so clearly I think it can be reasonable to do so. But only in areas where I have personal expertise and have done extensive study, all involving science-based medicine and the intersection of science and pseudoscience, something on which I think I can fairly claim expertise. Even then, I do so very cautiously, and always with the starting assumption that I may be wrong or missing something. First, I try to prove myself wrong, and then I check with others with proper expertise. And to put this into further perspective, this has always been in situations where the consensus involved pseudoscientists and paraprofessionals with clearly flawed and biased methodology, and/or professionals without proper expertise in pseudoscience who were essentially fooled.

None of this applies in the case of the IPCC. This is a broad consensus of proper experts. In order to deny their findings (or at least sufficiently muddy the waters for political purposes) contrarians will deny the very concept of expertise or consensus (both ludicrous propositions, supported only with logical fallacies). Or they will cherry pick evidence or mispresent them. Some will engage in conspiracy theories, having to spin tales about a global hoax against the poor fossil fuel industry, or some left-wing power grab. None of these claims are credible, and they don’t address the robust evidence on which the IPCC report rests.

Having a legitimate contrarian view also requires that you honestly engage with your critics or those who disagree with you, but that rarely happens. Climate deniers, rather, typically just snipe, dropping cherry-picked factoids in a hit-and-run style. When their claims are debunked, they don’t admit it or provide a counter argument, just move on to the next hit-and-run. Once enough time goes by, then repeat their previously debunked claims. This is profound intellectual dishonesty. If you really think you are smarter than the world’s experts on a topic, or that you have some superior perspective or objectivity, then you should be able to properly engage with pushback. Otherwise, you are just a propagandist.

Finally I want to point out that the current IPCC report shows the progression of the evidence of AGW. The overall pattern that emerges when dealing with some kind of pseudoscience is that they are stagnant or they go around in circles. The wander from claim to claim, without building a solid foundation. The evidence base and theoretical framework for homeopathy is about the same today as it was 200 years ago. Nothing that amounts to real progress has been made. That is because homeopathy is not real.

This IPCC report, however, builds on a solid foundation. Over time multiple independent lines of evidence have been converging on the same conclusions, and the confidence in those conclusion has mostly been rising. This is perhaps the biggest difference between this report and previous reports – the interval evidence has become more solid. Scientists, ever cautious, are slowly becoming more confident in their conclusions.

Where ever you may be starting from, I strongly suggest you read at least the entire executive summary with an open mind. It is always best if our policies are informed (not determined) by the best available science. There are many policy implications to the science being presented in this report. We ignore the science at our own peril.