In their recent paper on how to avoid dangerous climate change, authors Y. Xu and V. Ramanathan calculate the climate would warm about 3.5°C by 2100 (relative to 1900), given a “baseline-default” emissions trajectory. This particular trajectory assumes declines in energy intensity* will continue at about the current pace for the balance of the century. Unfortunately, a rise of 3.5°C could very well be catastrophic for our planet long before we even hit the 3.5 degree mark or get to 2100. Better to keep warming within 1.5°C, as many climate scientists have called for. The question is how. Xu and Ramanathan suggest the following three-lever strategy:
1. Quicker pace of energy efficiency improvements may reduce CO2 warming by 0.9 °C from 3.5 to 2.6 °C of pre-industrial levels..
2. Maximum deployment of current technologies to reduce emissions of short-lived climate pollutants may reduce warming by another 1.2 °C.
3. Carbon extraction and sequestration of CO2 to thin the atmospheric CO2 blanket already enveloping our planet.
Ideally, these levers should be pulled by 2020.
* In these climate change posts, energy intensity is being defined as the amount of energy used to produce a unit of global GDP. A decline in global energy intensity means the world is able to produce more GDP for each unit of energy consumed.
Next: More on the three levers, starting with energy efficiency.
References:
Millar, R.J. Why the 1.5C warming limit is not yet a geophysical impossibility. 19 Sep 2017 http://www.oxfordmartin.ox.ac.uk/opinion/view/378
Millar, R.J., Fuglestvedt, J.S., Friedlingstein, P., Rogeli, J., Grubb, M.J., Matthews, H.D., Skeie, R.B., Forster, P.M., Frame, D.J. and Allen, M.R. (2017) Emission budgets and pathways consistent with limiting warming to 1.5 C. Nature geoscience.
Xu, Y. and V. Ramanathan (2017). "Well below 2 ° C: Mitigation strategies for avoiding dangerous to catastrophic climate changes." Proceedings of the National Academy of Sciences 114(39): 10315-10323. http://www.pnas.org/content/114/39/10315.full