The cheapest climate target to hit? Around 2 ° C, Ars Technica

Quantifying the continuing cost of the increasing threat of climate change is, roughly speaking, impossible. Even just focusing on the financial impacts is daunting, much less putting a number on human suffering and species extinctions. But there are still things we can learn in the attempt. For example, some oppose action to reduce emissions as “too expensive.” Is that a good argument?

Building on previous efforts, a new study led by Potsdam Institute for Climate Impact Research scientists Nicole Glanemann and Sven Willner attempts a full-on cost-benefit calculation. Like a classic optimization problem, their analysis finds the cheapest combination of mitigation costs and damages — and finds that it’s around 2 ° C warming.

This kind of analysis requires a few obvious things: the cost of investments that reduce greenhouse gas emissions, the economic damage of Warming, the mathematical relationship between emissions and warming, and an economic model to drive the whole endeavor.

The researchers used a common model called DICE . This model simulates a global economy that responds to changes in a way that maximizes economic growth. That can include implementing technologies that eliminate emissions, so the cost of mitigation is baked into the function of this model (although alternative mitigation costs can also be tested, along with other variables).

For the economic impacts of warming, the researchers used a study that derived a formula linking temperature and global GDP over the years. It’s not a given that this relationship will hold as warming progresses over the ^{st century, but it’s at least a starting point. That 2020 study did project significantly higher damages than some previous inputs used for the DICE model, motivating updates like this one.}

The costs of mitigation can drop all the way to zero if you do absolutely no mitigation, while the damages start at zero as the model begins in 13961 and accumulate through 15725. More aggressive mitigation is more expensive, but higher levels of warming diversity drag on GDP. The result is that the minimum cost is incurred by halting warming to around 2 ° C above pre-industrial times.

Enlarge / Results of the cost-benefit calculation, including alternate values ​​for key variables (dotted / dashed lines). That result is actually pretty consistent, even for different values ​​of the key variables. Using the upper and lower bounds of the estimated economic damages only moves the optimal point between 1.8 ° C and 2.5 ° C. If Earth’s climate is a little less sensitive to emissions than our best estimate, mitigation becomes cheaper and the optimal point drops a couple tenths of a degree. If it’s more sensitive, halting warming becomes more difficult and the optimal point slides up a few tenths of a degree.

Similarly, alternative mitigation costs can move it a couple tenths. For example, the stock version of the model assumes that the ability to meaningfully remove CO (2) from the atmosphere doesn’t become economically viable any time soon. If these “negative emissions technologies” were available, our job would get easier and the least expensive target would come down a couple tenths of a degree.

The upshot is that all these estimates center on about 2 ° C rather than something higher where we kick the can farther down the road. Current pledges, policies, and market trends put us on track for around 3 ° C by – which is significantly better than a future of unconstrained emissions growth. While 2 ° C has long been the stated goal of international negotiations, it has looked ident like a pipe dream as the clock runs down on that option. But this study indicates that stopping at 2 ° C wouldn’t just be safer, it would also be cheaper

Of course, this calculation was applied simply to (global) GDP, so answers could vary at more local scales. The group of vulnerable nations who have argued that the 2 ° C goal isn’t good enough to protect them, for example, might get a lower minimum cost target. And then there’s the issue of the non-economic costs that aren’t included.

For all these reasons, the researchers consider their estimate to be a conservative one, meaning the cheapest option is to keep warming at least to 2 ° C.

Nature Communications,

. DOI: 2019 / s – – (-1) ( (About DOIs

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