I've been looking at climate modelling studies with a renewed vigor since reading Dyson's statement that projections of global warming are based on flawed climate models. It's not only Dyson's comment that provokes me. The climate models fallacy is promoted by many private interest groups trying to influence the COP21 climate talks in November. For example, the Cornwall Alliance is a group of faith-based, pro-fossil fuel, evangelicals:
Many fear that carbon dioxide emissions from fossil fuel use endanger humanity and the environment because they lead to historically unprecedented, dangerous global warming....This letter also cites a lot of inaccurate and outdated information on the instrumental record, and credits the Judeo-Christian Heritage with the rise of the modern scientific method and dismisses computer modelling as not a reliable avenue of research.
Computer climate models of the warming effect of enhanced atmospheric carbon dioxide are the basis for that fear. -- An Open Letter on Climate Change to the People, their Local Representatives, the State Legislatures and Governors, the Congress, and the President of the United States of America. Cornwall Alliance, 2015.
So, I want to share what fictions climate models help us to maintain, and I didn't have to dig deep for good example, rather, just open my mailbox. My most recent issue of Nature (15 Oct. 2015) reports on modelling the loss of continental ice from Antarctica:
- The multi-millennial Antarctic commitment to future sea-level rise, Golledge et. al, Nature 15 October 2015
The article cites four paleoclimate studies that connect global warming in the past with the loss of Antarctic ice (three of which I've read). One of these articles is open access, so I'll use it to discuss underlying assumptions driving our computer modelling study:
- The multimillennial sea-level commitment of global warming, Levermann et al., Proceedings of the National Academy of Sciences
For the Eemian Interglacial (115,000 years ago): "We thus assign a possible sea-level range of 5–9 m higher than present...."These estimates converge around 7 meters, or 21 feet. This is big. It requires relocating hundreds of millions of coastal inhabitants, including the evacuation of some nations. Therefore, it's important to know the following:
For Marine Isotope Stage 11 (a time 400,000 years ago when orbital configurations most resembled those of our current Holocene): "We thus assign a possible sea-level range of 6–13 m higher than present...."
For the Pliocene (over 1 million years ago): "We thus conclude that sea level was at least 7 m above present during mid-Pliocene warm periods"
- How fast can the sea level rise occur?
- What global temperature makes the outcome unstoppable?
- What pathway is there to preventing a return of some or all of this paleo-historical sea level rise. (I say "paleo-historical" to emphasize that paleoclimates are history, though not recorded by humans.)
Golledge et al. put special emphasis on understanding how the topology of the shoreline maintains ice shelves that in turn slow the flow of ice sheets into the ocean. Golledge et al. clearly acknowledge that their resolution on topography is coarser than what would be ideal, due to limits on computer processing power. According to a reviewer of the article, their results represent a best case scenario:
...Golledge and collegue's simulations might represent a best-case scenario for future sea-level rise. (The long future of Antarctic melting, Robel, Nature 15 Oct. 2015)A best case for what? Best case means minimum rise of sea level, the best that we can hope for. This study describes what rate Antarctica will contribute to sea level rise under emissions scenarios that stabilize global temperatures from 2.6 to 8 degrees C above pre-industrial. The paleoclimate background makes a strong case that at least 7 meters of sea level rise should be expected. But by modelling the mechanics of ice loss, we can get some useful information on the following:
- We are probably committed to a rise of 0.5-3 meters by 2300 CE.
- If we do not reduce emissions according to the 2.6 degree scenario, the ice shelves currently trapped in Antarctica will collapse and allow a steady flow of ice loss to the ocean till at least 3000 CE. This is a lot of coastal adaption to push onto nearly a thousand years of future generations.
- The 2.6 scenario requires cutting our emissions by 2050 to half our emissions level in 1990. No doubt these are big cuts, but without them, we are committing future generations to nearly a thousand years of moving coastlines.
My opening may have criticized the evangelical community. Many conservative Christians side with the policies of the Cornwall Alliance. But I know enough evangelicals to know that many of them are present where natural disasters strike, e.g., rebuilding homes in poor nations and helping relocate refugees (something our nations don't have the best track record at). Christian charity is great and noble, but my instincts tell me that it's not as noble if you use ignorance and confusion to make the work necessary.