Random Variable

Thanks to IT and Owen for an apocalyptic Kino Fist screening. Barry Hines Threads was truly terrifying. Looking at the credits at the end, it was clear that Hines and Mick Jackson went to some effort making sure the docu-drama-calypse was as accurate as possible, representing a scientific best-estimate of the impact of all out nuclear war, consulting such luminaries as Carl Sagan. Now, there’s a natural scientist with an ethical conscience. Sagan popularised the nuclear winter hypothesis, that large-scale nuclear war would blot out the sun for months, causing harvest failures, with severe impacts on countries whose infrastructure is already decimated by the war itself. At the end of the film, we see a 2nd-generation mutated stillborn baby born in a Britain where most of the English language has already been lost within 15 years, in a society that appears to have economically regressed back to the Neolithic revolution.

But, I was wondering just how accurate the predictions are today. Funnily enough, this requires entering the world of Global Climate Models. Apparently, the models that generated the mass-extinction nuclear winter scenarios were simple 1-dimensional models. These later gave way to more complex models which suggested that the impact of dust would not be so bad at all compared to the initial blast effects [1].

However, the scenarios have been rerun using our latest-and-greatest GCMs (developed for global warming modelling), and to account for the world’s shrunken nuclear arsenal. The results don’t look good [2]:

We use a modern climate model to reexamine the climate response to a range of nuclear wars, producing 50 and 150 Tg of smoke, using moderate and large portions of the current global arsenal, and find that there would be significant climatic responses to all the scenarios. This is the first time that an atmosphere-ocean general circulation model has been used for such a simulation and the first time that 10-year simulations have been conducted. The response to the 150 Tg scenario can still be characterized as ‘‘nuclear winter,’’ but both produce global catastrophic consequences. The changes are more long-lasting than previously thought, however, because the new model, National Aeronautics and Space Administration Goddard Institute for Space Studies ModelE, is able to represent the atmosphere up to 80 km, and simulates plume rise to the middle and upper stratosphere, producing a long aerosol lifetime. The indirect effects of nuclear weapons would have devastating consequences for the planet, and continued nuclear arsenal reductions will be needed before the threat of nuclear winter is removed from the Earth.

Even if all out nuclear war doesn’t occur, and you have a nuclear exchange between two small countries, then even that would still be bad as cities burn for weeks into ashes—creating a Nuclear Autumn, to borrow from Thompson & Schneider’s optimism [3]:

The climate changes are large and long-lasting because the fuel loadings in modern cities are quite high and the subtropical solar insolation heats the resulting smoke cloud and lofts it into the high stratosphere, where removal mechanisms are slow. While the climate changes are less dramatic than found in previous “nuclear winter” simulations of a massive nuclear exchange between the superpowers, because less smoke is emitted, the changes are more long-lasting because the older models did not adequately represent the stratospheric plume rise.

All this means, reducing the world’s nuclear arsenals through decommissioning and non-proliferation, as well as clamping down on the market for weapons should still be key priorities for global cooperation. More when I’ve read last month’s NLR.

1. S. L. Thompson and S. H. Schneider, “Nuclear Winter Reappraised,” Foreign Affairs 64 (1985): 981.
2. A. Robock, L. Oman, and G. L. Stenchikov, “Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences,” J. Geophys. Res 112 (2007).
3. A. Robock et al., “Climatic consequences of regional nuclear conflicts,” Atmos. Chem. Phys 7 (2007): 2003-2012.