How Nuclear Winter Got Into the IPCC Report for the First Time

The Intergovernmental Panel on Climate Change (IPCC) is now completing its Fifth Assessment Report. None of the previous reports considered the most “dangerous anthropogenic interference with the climate system” possible, the climatic effects of nuclear war. The quote in the previous sentence is from Article 2 of the 1988 Framework Convention on Climate Change (FCCC), which thought of these impacts coming from increased greenhouse gases, but we now know that humans pose an even greater threat to the planet. Article 3 of the FCCC says, “The Parties should take precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate its adverse effects. Where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing such measures....”

As a Lead Author of Chapter 8 (Radiative Forcing) of the new Working Group I report, I thought it was important to include the threat that nuclear weapons still pose in this high visibility statement to the world. I inserted a paragraph pointing out that volcanic eruptions serve as an analog that supports new work on nuclear winter. The US and Russia still have enough nuclear weapons to produce a full nuclear winter, with temperatures staying below freezing in the summer in agricultural areas around the world, sentencing most of the people on the planet to death by starvation. Even a nuclear war between two new nuclear states, India and Pakistan, using much less than 1% of the global nuclear arsenal, could produce climate change unprecedented in recorded human history, with temperatures colder than the Little Ice Age and grain production in the US and China lowered by 20% to 50% for a decade. This would not be nuclear winter, but could produce large-scale famine.

Although some reviewers of our chapter said that this topic was inappropriate, others said it was very important and needed emphasis. I will review the new science and then tell the story of the discussions within our chapter, with review editors, and with the IPCC leadership that resulted in a box in Chapter 8 that discusses nuclear winter. In my opinion, the threat that nuclear weapons pose to the planet is much easier to solve than global warming. We need to eliminate nuclear weapons so we have the luxury of working on the global warming problem without the possibility of the existential global threat still posed by the global nuclear arsenal.