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On 16th June this year, the Guardian ran an article with what seemed to me to be a remarkable headline, namely “How millions of lives can be saved if the US acts now on climate” with a secondary headline that is possibly even more remarkable: “Researchers have now calculated how many people could be saved from heat-related death if the US takes meaningful action”. And they do mean how many people – exactly how many people, and by US, state and even city.

I followed the helpful link to the Climate Impact Lab’s lives saved calculator with considerable curiosity, and was amazed to find that the people behind it claim to have calculated precisely how much adaptation cost and how many lives can be saved if the country, state or city goes “clean electric” or net zero by 2050.

The calculator is fun (believe it or not, given the gloomy nature of the subject). Do you live in Oakville, California and want to know what can be saved if your city achieves 100% “clean” electricity by 2050? Then you’re in luck, as the “lives saved calculator” will tell you: $62,300 in adaptation costs globally by 2100, apparently, but regrettably, no lives would be saved. Hang on a minute. Nil desperandum, residents of Oakville. Think big. Don’t just achieve 100% “clean” electricity by 2050, but instead achieve net-zero emissions. What then? $449,000 adaptation costs saved by 2100 and, what’s truly amazing, one life saved too!

Not enough? Never mind, let’s think bigger. What about California as a whole? That’s more like it – a saving globally by 2100 of $33.8 billion in adaptation costs and 73,800 lives saved. Or net zero; then 508,100 lives and $243.4 billion by 2100. How about the USA? Well, apparently, if the United States achieves 100% clean electricity by 2050, then 1.6 million lives and $742.2 billion in adaption costs will be saved by 2100. Better still, if the USA achieves net zero by 2050, then those figures become 7.3 million lives and $3.7 trillion in saved adaptation costs. Obviously the costs of going net zero will then be worth it. It’s obvious. Isn’t it?

Methodology

How is this all established with such confidence? Well, the website lets us into the secret of their approach. And we should be impressed and have confidence in it:

The Climate Impact Lab’s team of economists, climate scientists, data engineers, and risk analysts are building the world’s most comprehensive body of research quantifying the impacts of climate change, sector-by-sector and community-by-community around the world.

OK, what does that involve?

The Climate Impact Lab is…leveraging a first-of-its-kind, evidence-based, data-driven approach to quantify the impacts and costs of climate change, sector-by-sector and community-by-community around the world. This research will allow decision-makers in the public and private sectors to understand the risks climate change presents and mitigate those risks through smarter investments and public policy. The research will also produce the world’s first empirically-derived estimate of the social cost of carbon — the cost to society from each ton of carbon dioxide emitted. This figure can serve as the basis for energy and climate policies.

Well, it sounds good, I’ll grant you that, but so far it’s all just words. And if you read on, the website will offer you lots more such words, but nowhere does it set out the precise methodology that offers up such specific numbers, both human and financial. So, to try to work out what’s going on, I had to keep digging, and if I’ve understood things correctly, the important piece of the jigsaw puzzle is an article published on 21st April 2022 and titled “Valuing the Global Mortality Consequences of Climate Change Accounting for Adaptation Costs and Benefits”. In many ways, it’s a hugely impressive piece of work, and I urge you to read it. The problem I have with it, however, is that while the Guardian article and (to a considerable extent) the Climate Impact Lab’s website both deal in certainty, the study on which such apparent certainty is based very properly is in reality full of uncertainty. The abstract alone makes it clear that, for all the talk of empiricism and use of impressive levels of global data, the conclusions remain founded on estimates:

This paper develops the first globally comprehensive and empirically grounded estimates of mortality risk due to future temperature increases caused by climate change…we estimate age-specific mortality-temperature relationships that enable both extrapolation to countries without data and projection into future years while accounting for adaptation….Under a high emissions scenario, we estimate the mean increase in mortality risk is valued at roughly 3.2% of global GDP in 2100 …Finally, we estimate that the release of an additional ton of CO2 today will cause mean [interquartile range] damages of $36.6 [-$7.8, $73.0] under a high emissions scenario and $17.1 [-$24.7, $53.6] under a moderate scenario, using a 2% discount rate that is justified by US Treasury rates over the last two decades. Globally, these empirically grounded estimates substantially exceed the previous literature’s estimates that lacked similar empirical grounding, suggesting that revision of the estimated economic damage from climate change is warranted. [My emphasis].

I take no issue with the authors‘ work. Rather my issue is with the relative certainty to which their properly caveated work is put. The “calculator” makes no mentions of estimates. Instead it invites us to “See how reducing emissions in your community improves public health globally.” And when concerned citizens of the United States look to see what impact actions taken in their local community, state or country as a whole might make, they are not offered any caveats; rather, they are told bluntly and simply that achieving “clean electricity” or “net zero” would save x lives and avoid $x million (or billion or trillion) in adaptation costs globally.

The other obvious shortcoming of this approach (or so it seems to me) is that I can’t see that it considers the inevitably huge uncertainties as to what the rest of the world, outside the United States, might do vis-a-vis climate change and emissions policies by 2050. If China, India and Russia “go rogue” (which I venture to suggest isn’t beyond the realms of possibility, given emissions policies to date), then surely all bets are off? Alternatively, in the unlikely event that COP27 (or some subsequent COP) actually achieves its objectives rather than continues as all the talking shops to date, then again I would assume a reassessment of some of the key assumptions might be required.

And, colour me cynical if you will, but I simply fail to accept that it can be stated with such categorical certainty that if (say) Tacoma in Washington State achieves net-zero emissions by 2050 then that alone, without qualification or caveat, will save 3,400 lives and avoid $1.6 billion in adaptation costs by 2100.

Conclusion

The Guardian tells us that this research and the calculator mean that:

A total of 7.4 million lives around the world will be saved over this century if the US manages to cut its emissions to net zero by 2050, according to the analysis.

The financial savings would be enormous, too, with a net zero America able to save the world $3.7tn in costs to adapt to the rising heat. As the world’s second largest polluter of greenhouse gases, the US and its political vagaries will in large part decide how many people in faraway countries will be subjected to deadly heat, as well as endure punishing storms, floods, drought and other consequences of the climate emergency.

Well, maybe, maybe not. Of course, if one accepts that greenhouse gas emissions inevitably mean a warming planet, and if one accepts that this inevitably means that things will get worse rather than better, then no doubt a real reduction in emissions by (rather than merely exporting them from) the USA might save lives and might save money. But it’s a big and complex world, both as regards those assumptions and the geopolitical realities that the USA (and the rest of us) will face over the next 28 years up to that magic 2050 date. Realistically, it can all only be guesswork, and offering this veneer of near-certainty strikes me as massively over-egging the pudding.

Perhaps I’m not alone in my thoughts. So far as I’m aware, in the UK at least only the Guardian seems to have made anything of this story. Even the BBC, which so often reports on studies such as these in tandem with the Guardian, seems to have decided not to run with this one. For once they may be right.

via Climate Scepticism

June 23, 2022

Applied Maths – Climate Scepticism (cliscep.com)

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