Caldeira Lab

Natural Climate Variability and Future Climate Policy, Katharine L. Ricke

[Nature Climate Change]

Click here to read about the paper



It’s obvious to most people that extreme heat waves, big storms and other dramatic weather events provoke discussion of climate change in the media and political circles.  Scientifically, we know these extreme events are caused by a combination of climate change and natural variability. Yet no one knows how the natural climate variability component might impact global efforts to reduce emissions.
To look at the potential effect that unpredictable extreme weather events might have on how convinced citizens are to take action on climate change and, in turn, what policy makers’ timelines will be to implement strong climate policies, we did an analysis in which deterministic citizens respond to a stochastic world that’s represented by global climate model projections.
We analyzed output from a large climate model ensemble and looked at how different local experiences with extreme temperature events might affect the timing of strong climate policy action. The social system in our analytic model is completely deterministic – so the only differences between different simulation ensemble members are small perturbations in initial conditions of the simulation – something that produces different natural variability pathways as the simulations progress.
As a look at what we found, this figure shows the range of times-to-policy-action for the top six carbon dioxide emitters in the world.  The spread of the results for each emitter here is due entirely to natural climate variability. From this large spread in the results, we can see that natural climate variability, superimposed on a global warming trend, has the potential to affect the timescale for reaching national – and thus international – political consensus on climate change mitigation.
This suggests there are some significant risks associated with allowing local extreme events to drive national and global climate policies.

Ricke, K. and K Caldeira, Natural Climate Variability and Future Climate Policy, 2014: Nature Clim. Change, 4, 1-6, doi: 10.1038/NCLIMATE2186.

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