Tag Archive for Common Future

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

early-warning-of-climate-tipping-points-19-638

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 http://www.commonfuture-paris2015.org/

(Scientific prelude to COP21 meeting this December in Paris)

Video:  https://www.youtube.com/watch?v=uOepcNc278I

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

Notes:

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 http://www.slideshare.net/CFCC15/early-warning-of-climate-tipping-points?qid=4f427685-a10d-4ce5-a100-1c082b8976b6&v=default&b=&from_search=1

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.