Multi-Agency Cooperation Needed to Accurately Model Effects of Nuclear Weapons

Existing models for the effects of nuclear war are incomplete and out of date, a new National Academies report finds.

The report, commissioned by Congress through the National Defense Authorization Act for FY 2021, recommends that U.S. agencies “coordinate the development of and support for a suite of model intercomparison projects (MIPs) to organize and assess models to reduce uncertainties in projections of the climatic and environment effects of nuclear war.”

MIPs are traditionally used by Earth and climate scientists to answer questions related to climate change . The National Academies report proposes a series of MIPs that would require interdisciplinary support to understand the uncertainties outlined in the report.

The 200+ page report attempts to assess four nuclear conflict scenarios, ranging from a single detonation to a full-scale nuclear war, but concludes that there are too many uncertainties to properly model any of the scenarios’ long-term impacts on the environment, human health, and society. It also finds that the “nuclear winter” scenario that has dominated post-nuclear war modeling since the 1980s is outdated both in terms of its precision and in its assumptions about nuclear conflict.

“There have been significant military, political, and technological changes on the nuclear landscape, as well as significant advances in our understanding of and ability to model Earth as a system,” said Antonio Busalacchi, president of the University Corporation for Atmospheric Research, during a webinar hosted by the National Academies on last month.

Busalacchi emphasized that the recent conflict between Israel and Iran falls beyond the scope of the report but nonetheless demonstrates the need to consider what might happen in a regional conflict involving nuclear weapons and how the associated explosions might affect the environment.

“A lot of previous studies have focused on extreme case studies, and so there’s a need … for a better understanding of the realm of possible outcomes that then feeds into a cascading series of interactions, feedback, and uncertainties,” Busalacchi said.

At the direction of Congress, the report authors attempted to look beyond the effects of an initial blast and its immediate environmental impact and model socioeconomic effects that might last far beyond the conflict.

However, the report concludes that much more data is necessary to predict the effects of a nuclear war on food supplies, agriculture, and climate.

Radiation-climate physics is well understood, but long-term ecological impacts are unknown due to “due to varying responses across different geographical regions and complex human land-use changes that would follow,” the report says.

There are gaps in up-to-date research on direct and indirect impacts on human mental and physical health, which is one aspect that the recommended MIPs would address.

The report argues that some fields with substantial potential value for nuclear war modelling have neglected the subjects that would make them most useful to that endeavor. For example, the report notes that fire modelling is heavily focused on rural and wildland areas and that urban, suburban, and industrial zones are “poorly characterized” by comparison. “We need to have a much more coordinated attack on this problem, which really requires a whole-of-government approach,” said Busalacchi. “These MIPS could identify what are those crucial characteristics … so that we can reduce that uncertainty going forward.”