Archive for October 29, 2015

Social Cost of Carbon should be 6 Times Higher

The economic damage caused by a ton of CO2 emissions-often referred to as the “social cost of carbon-could actually be six times higher than the value that the United States uses to guide current energy regulations, and possibly future mitigation policies, Stanford scientists say.

A recent U.S. government study concluded, based on the results of three widely used economic impact models, that an additional ton of CO2 emitted in 2015 would cause US$37 worth of economic damages. These damages are expected to take various forms, including decreased agricultural yields and harm to human health related to .

But according to a new study, published online this week in the journal Nature Climate Change, the actual cost could be much higher. “We estimate that the social cost of carbon is not $37, as previously estimated, but $220,” said study coauthor Frances Moore, a PhD candidate in the Emmett Interdisciplinary Program in Environment and Resources in Stanford’s School of Earth Sciences.

Based on the findings, countries may want to increase their efforts to curb greenhouse gas emissions, said study coauthor Delavane Diaz, a PhD candidate in the Department of Management Science and Engineering. “If the social cost of carbon is higher, many more mitigation measures will pass a cost-benefit analysis,” Diaz said. “Because carbon emissions are so harmful to society, even costly means of reducing emissions would be worthwhile.”

Read more at:

Paper:  Moore et al., 2015.  Temperature impacts on economic growth warrant stringent mitigation policy,Nature Climate Change, DOI: 10.1038/nclimate2481

Tim Lenton: Our Common Future Under Climate Change 2015, Paris


Early Warning for Thresholds and Tipping Points in the Earth System

Tim Lenton, University of Exeter (1st speaker, Session L-2.4)

Conference website at

(Scientific prelude to COP21 meeting this December in Paris)


Implication:  70% emission reductions are needed now, e.g., shutting down fossil fuels by 2040 is needed to stabilize at 1.5 C increase above pre industrial level


Expert elicitation on chance of at least 1 in 5 of earth systems reaching a tipping point by 2100

Questioned 5 experts (Kriegler et al.); used models and observational data

moderate warming scenario, 2-4 C increase:  16% chance of tipping, lower bound

business as usual > 4C increase:  50-60% chance of tipping, lower bound

much higher than economists have been assuming

Slides at

Slide 3:  estimates above are shown

Slide 9:  tipping occurs about 200 years after early warning system is triggered, but 500 years of data  maybe needed; better methods needed

Slides 10-11: N. Pacific surface temp slowing down, Pacific Decadal Oscillaiton index is slowing: is the mixing layer deepening?

Slide 12: marine ecoysystem more variable, more likely to hit tipping point; marine animals are already moving

Slide 14:  social cost models with tipping points included — impact would be ~ 10% of world GDP estimates

Slide 17: Social cost of carbon:  Nordhouse $37 / ton, they estimate it is up to 592 $/ton; 

Risk preferences for uncertainty of future impacts account for about 1/2 of social cost.

Implication:  70% emission reductions are needed now, e.g., shutting down fossil fuels by 2040 is needed to stabilize at 1.5 C increase above pre industrial level

Slide 18:  the interactions of tipping points are also important

Thank you to Thomas Phillips for sharing.