“Regional Nuclear War” Could Be Not So Regional After All

Posted on January 29, 2007

Back in the 1980s, a group of scientists (led by Carl Sagan) made news when they announced the discovery of a theretofore unknown danger posed by nuclear weapons: "nuclear winter", massive global cooling that would ensue after thousands of nuclear detonations choked the atmosphere with dust and soot. Their findings starkly illustrated the danger the Cold War arms race posed, not just to the powers participating, but to all humanity.

Then, of course, the Berlin Wall fell, the U.S. and Russia made nice and the danger of nuclear winter disappeared forever. Right?

Maybe not. On his blog over at Weather Underground, climate scientist Dr. Jeff Masters is reporting on a new study that indicates that it might take a whole lot less to trigger nuclear winter than we used to think.

The Sagan study was predicated on a full scale nuclear war between the U.S. and the Soviet Union. In such a war, tens of thousands of nuclear weapons would have been exchanged in a matter of hours. That scenario isn’t plausible anymore; what is plausible, though, is a so-called "regional nuclear war" in which two non-superpower nuclear powers hit each other with a smaller but significant number of weapons, on the order of 10-100 each. The obvious case study for such a war would be if the long-simmering conflict between India and Pakistan went nuclear: India is estimated to have 30-90 small nuclear warheads, with Pakistan’s arsenal estimated at 25-50.

Clearly, it would be a tragedy beyond imagining for the people who live in India and Pakistan if those countries fired their nukes at each other. But should the rest of the world be afraid too? That was the question that was posed in the study "Climatic consequences of regional nuclear conflicts", conducted by scientists from Rutgers, the University of Colorado, and UCLA. In that study, the scientists took a sophisticated climate model and watched what happened after 100 Hiroshima-size bombs — roughly the complete nuclear arsenals of Pakistan and India — went off, with the explosions all going off within a single region of the globe.

The results are sobering:

The effects of the smoke cloud on surface temperature are large. A global average surface cooling of –1.25 C persists for years, and after a decade the cooling is still –0.5 C. The temperature changes are largest over land… A cooling of several degrees occurs over large areas of North America and Eurasia, including most of the grain-growing regions. As in the case with nuclear winter calculations, large climatic effects would occur in regions far removed from the target areas or the countries involved in the conflict.

A drop of -0.5-1.25 degrees Celsius might not sound like much. But it’s enough to cause widespread starvation and social disruption. When the eruption of Indonesia’s Mount Tambora in 1815 threw so much ash and dirt into the atmosphere that the next year saw a drop in global temperatures of similar scale, the result was christened "the year without a summer" — a year that saw dramatically aberrant cold weather. Crops froze, food shortages in England and France led to riots, and it snowed in Boston in June.

And that was just one year. The study, if accurate, indicates that a regional nuclear war would result in two or three such years in a row, with substantial cooling lingering for a decade.

In other words: bad stuff. And all it would take would be one bad decision in Islamabad or New Delhi — or Pyongyang, or Jerusalem, or Paris, or London, or Washington — to make it a reality for all of us.