Climate change could lead to 83 million "excess deaths" by 2100.
A young researcher calculates the Mortality Cost of Carbon. The number is staggering.
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Although many climate studies demonstrate that global warming can cause a significant number of excess deaths—an unusual mortality increase during a specific period—existing integrated assessment models (IAMs) that calculate the social cost of carbon (SCC) and suggest the best climate policies to limit damage, generally provide limited information on the impact of carbon on heat-related human mortality.
R. Daniel Bressler, a PhD. candidate at Columbia University’s Earth Institute and the university’s School of Public and International Affairs designed a study to correct that major gap in current estimates of the Social Cost of Carbon.
He did so by creating an extension to William Nordhaus’ pioneering IAM DICE-2016. Called DICE-EMR (Dynamic Integrated Climate-Economy Model with an Endogenous Mortality Response) he constructed an additional reduced-form mortality damage function that explicitly accounts for the temperature-related climate impacts on the mortality rate using central estimates from studies chosen from an interdisciplinary systematic research synthesis of the scholarly literature. By doing so, he introduces a new metric, the mortality cost of carbon (MCC),
On his website, Bressler writes:
The DICE-EMR model updates the DICE-2016 model, and determines the social cost of carbon (SCC), which represents the monetized net present value of social damage from emitting one ton of carbon dioxide at certain point in time. It can also be used to prescribe an optimal climate policy by comparing the benefits of avoiding climate damages with the costs of reducing emissions. In addition, the DICE-EMR model calculates a new metric-- the mortality cost of carbon (MCC) -- that measures the marginal mortality impact of climate change in units of excess deaths without discounting or valuing lives. This follows from the National Academies of Sciences 2017 recommendations to disaggregate climate damages and to give them in their natural/physical units in addition to monetized units, which in the case of mortality is the number of excess deaths.
The results are truly frightening. From the report:
We use DICE-EMR to produce a new metric that avoids some of the limitations of the SCC: the mortality cost of carbon (MCC). The 2020 MCC is the number of expected temperature-related excess deaths globally from 2020 to 2100 caused by the emission of one additional metric ton of carbon-dioxide-equivalent emissions in 2020. We find that in the DICE baseline scenario that results in 4.1 °C warming above preindustrial temperatures by 2100, the 2020 MCC is 2.26 × 10−4 lives per metric ton in the central estimate, which implies that adding 4,434 metric tons of carbon dioxide in 2020—equivalent to the lifetime emissions of 3.5 average Americans—causes one excess death globally in expectation between 2020 and 2100.
Using the baseline scenario, Bressler’s study assumes that on the current path, by 2050, average temperatures will surpass the Paris goal of 2.1 degrees C (3.8 F) above those of the preindustrial age and will get even worse very rapidly, with temperatures reaching 4.1 degrees C (7.4 F) higher by 2100.
Using the new Dice-EMR model under this scenario, heat-related climate change would cause 83 million excess deaths by 2100, the study projects. Optimal emission climate policy after 2050 could save 9 million of those lives, Bressler projects. As Columbia’s Climate School State of the Planet blog puts it:
In bigger, less personal terms: adding 1 million metric tons to the 2020 baseline emissions would kill 226 people. Those 1 million tons equal the yearly emissions of 216,000 passenger vehicles; or, 115,000 homes; or 35 commercial airliners; or 0.24 coal-fired power plants.)
The report also finds that the current social cost of carbon ($37) under Dice 2016 is way too low and increases seven-fold under the updated DICE model to $258 per metric ton.
In the baseline emissions scenario, the 2020 MCC is 2.26 × 10‒4 [low to high estimate −1.71× 10‒4 to 6.78 × 10‒4] excess deaths per metric ton of 2020 emissions. This implies that adding 4,434 metric tons of carbon dioxide in 2020—equivalent to the lifetime emissions of 3.5 average Americans—causes one excess death globally in expectation between 2020-2100. Incorporating mortality costs increases the 2020 SCC from $37 to $258 [−$69 to $545] per metric ton in the baseline emissions scenario. Optimal climate policy changes from gradual emissions reductions starting in 2050 to full decarbonization by 2050 when mortality is considered.
There are limits to the Dice-EMR model, of course. It accounts only for direct temperature-related deaths, like heat strokes and omits many other possible deaths from floods, storms, agriculture failures, wars or changes in disease patterns. Bressler used the central estimates of the public health data he analyzed rather than best or worst case numbers. All of which means the projection of 83 million deaths may well be a vast underestimate.
My takeaway from this devastating new mortality metric is that we’re soon getting to that place where only the privileged will survive in temperature-controlled underground bunkers a lot faster than many of us who remember Dr. Strangelove had thought. The optimal time (and maybe last chance) to mobilize the best climate policies, behaviors, and technologies is obviously right now. It has never been clearer that the social cost of carbon (with mortality costs factored in) is a cost none of us want to pass on to our fellow and potential future earthlings. Sorry, Slim. It’s time to close that bomb door now.
Dig Deeper
The mortality cost of carbon (R. Daniel Bressler, Nature)
The Dice-EMR model (R. Daniel Bressler website)
More Carbon Emissions Will Kill More People. Here's How Many. (State of the Planet)
Study: Cost of carbon emissions measured in lives lost is high (Andrew Freeman, Axios)
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