Posts

Few pathways to an acceptable climate future without immediate action, e.g., carbon neutral energy production by 2030 and low atmospheric sensitivity to increased CO2

  • A new comprehensive study of climate change has painted over 5 million pictures of humanity’s potential future, and few foretell an Earth that has not severely warmed.
  • But with immediate action and some luck, there are pathways to a tolerable climate future, according to a research team.
  • One pathway is to immediately and aggressively pursue carbon-neutral energy production by 2030 and hope that the atmosphere’s sensitivity to carbon emissions is relatively low, according to the study.
  • The researchers emphasize that rapid carbon reduction strategies provide a hedge against the possibility of high climate sensitivity scenarios.

Read full ScienceDaily summary here (from March 2019)

….The model used in the study accounts for uncertainties in human activity and climate by exploring millions of scenarios, some of which reveal pathways to a world where warming is limited to 2-degrees Celsius by the year 2100 — a goal most climate experts say is required for a “tolerable” future.

The massive analysis shows that meeting that target is exceptionally difficult in all but the most optimistic climate scenarios. One pathway is to immediately and aggressively pursue carbon-neutral energy production by 2030 and hope that the atmosphere’s sensitivity to carbon emissions is relatively low, according to the study. If climate sensitivity is not low, the window to a tolerable future narrows and in some scenarios, may already be closed.

The researchers emphasize that rapid carbon reduction strategies provide a hedge against the possibility of high climate sensitivity scenarios.

“Despite massive uncertainties in a multitude of sectors, human actions are still the driving factor in determining the long-term climate. Uncertainty is sometimes interpreted as an excuse for delaying action. Our research shows that uncertainty can be a solid reason to take immediate action,” said Lamontagne.

J. R. Lamontagne, P. M. Reed, G. Marangoni, K. Keller, G. G. Garner. Robust abatement pathways to tolerable climate futures require immediate global actionNature Climate Change, 2019; DOI: 10.1038/s41558-019-0426-8

Abstract

Disentangling the relative importance of climate change abatement policies from the human–Earth system (HES) uncertainties that determine their performance is challenging because the two are inexorably linked, and the nature of this linkage is dynamic, interactive and metric specific1. Here, we demonstrate an approach to quantify the individual and joint roles that diverse HES uncertainties and our choices in abatement policy play in determining future climate and economic conditions, as simulated by an improved version of the Dynamic Integrated model of Climate and the Economy2,3. Despite wide-ranging HES uncertainties, the growth rate of global abatement (a societal choice) is the primary driver of long-term warming. It is not a question of whether we can limit warming but whether we choose to do so. Our results elucidate important long-term HES dynamics that are often masked by common time-aggregated metrics. Aggressive near-term abatement will be very costly and do little to impact near-term warming. Conversely, the warming that will be experienced by future generations will mostly be driven by earlier abatement actions. We quantify probabilistic abatement pathways to tolerable climate/economic outcomes4,5, conditional on the climate sensitivity to the atmospheric CO2 concentration. Even under optimistic assumptions about the climate sensitivity, pathways to a tolerable climate/economic future are rapidly narrowing.