Danish scientist Bjorn Lomborg has reacted sharply on the claim of over 200 medical journals, earlier this month, that there are significant health risks to any temperature rise. He concludes that there are very basic mistakes underlying the alarmist claims and send the following letter to the editor of The Lancet, one of the journals involved. Lomborg posted his letter on twitter.

Below the full letter.

Malmö, September 8, 2021

Dear Dr. Horton,

I read with interest your co-authored editorial “Call for emergency action to limit global temperature increases, restore biodiversity, and protect health” published in BMJ (2021;374:n1734) and many other international journals. As a core argument you write that there are significant health risks to any temperature rise and document it with “In the past 20 years, heat related mortality among people aged over 65 has increased by more than 50%.” However, this mortality increase [i] is a simple count, not a rate. The overwhelming part of the increase is due to the fact that the global population of people aged over 65 increased more than 40% in the same time period. Indeed, the increase in heat mortality rate is a much lower 9.4%. I am sure you agree that making a causal claim without adjusting for a dramatically changed population is fundamentally unsound. In fact, I am positive that you and your journal would demand a rewrite of any paper making such an argument. It is analogously flawed to claiming that Brexit led to better health for the European Union because total deaths overnight dropped 600,000 per year when the UK left. Given the enormous attention that your paper received, I therefore reach out to you to hear what action you will take to ensure that this unsound argument is rectified.

Yours truly,

Bjorn Lomborg President, Copenhagen Consensus, and Visiting fellow, Hoover Institution at Stanford University

I hope it might be useful to visualize the issue.

Below, the left box illustrates your editorial’s claim that temperature rises have increased the number of heat deaths of people aged 65+ by 53.7% while disregarding a 40% increase in the relevant population. The middle box shows the rate of heat deaths for the same population group, which takes into account the rapid increase in the population. I hope you will also find the right box interesting: it compares the heat deaths (which are slowly rising) with the much greater risk from cold deaths (declining much faster) from the Global Burden of Disease study. It highlights the problem with only looking at more heat death but neglecting the much greater fall in cold deaths.

This result is comparable with a new Lancet study that shows global warming increased heat deaths of all deaths by 0.21% (from 0.83% in 2000-03 to 1.04% in 2016-19) and decreased cold deaths by 0.51% (from 8.70% to 8.19%).[ii]

[i] Your reference is indicator 1.1.3, which shows a 53.7% increase in heat mortality from 165,000 annual deaths in 2000-04 to 253,000 annual deaths in 2014-18, from “The 2020 report of The Lancet Countdown on health and climate change: responding to converging crises” in the Lancet (https://doi.org/10.1016/S0140-6736(20)32290-X).

[ii] Table S5&6, “Global, regional, and national burden of mortality associated with non-optimal ambient temperatures from 2000 to 2019: a three-stage modelling study” Lancet Planet Health 2021; 5:e415–25.