Cold War nuke tests may have changed rainfall thousands of kilometres away

14 May 2020

Image: © Keith Tarrier/

The nuclear weapons tests at the height of the Cold War may have significantly altered rainfall in other parts of the world.

New research has found evidence that the enormous amounts of radiation released by nuclear tests during the Cold War did more than just damage environments near the blast sites.

In a study published to Physical Review Letters, researchers from the University of Reading compared historical climate data in Scotland between 1962 and 1964 with data on nuclear tests carried out during the same period.

By comparing days with high and low radioactively generated charge, they found that clouds were visibly thicker and there was 24pc more rain on average on days with more radioactivity. Radioactivity ionises the air, releasing an electric charge.

“By studying the radioactivity released from Cold War weapons tests, scientists at the time learnt about atmospheric circulation patterns. We have now reused this data to examine the effect on rainfall,” said Prof Giles Harrison, lead author of the study.

“The politically charged atmosphere of the Cold War led to a nuclear arms race and worldwide anxiety. Decades later, that global cloud has yielded a silver lining, in giving us a unique way to study how electric charge affects rain.”

Aid geoengineering research

Scientists have proposed for some time that electric charge modifies how water droplets in clouds collide and combine, potentially affecting the size of the water droplets and how they return to the ground as rainfall. This is difficult to observe in the atmosphere, but the bomb test data has helped researchers retrospectively investigate the theory.

While most of these detonations occurred in remote parts of the US and Soviet Union, radioactive pollution still spread widely through the atmosphere.

The climate records were obtained from the Kew weather station near London and the Lerwick station in the Shetland Islands. Located hundreds of kilometres off the Scottish mainland, the Shetland site was relatively unaffected by other sources of anthropogenic pollution.

This made it well suited as a test site to observe rainfall effects which, although likely to have occurred elsewhere too, would be much more difficult to detect in other areas. At the Shetland station, the findings showed noticeable differences in rainfall that vanished after the major radioactivity episode was over.

The researchers now hope their findings could aid cloud-related geoengineering research to explore how electric charge could influence rain to relive droughts or prevent floods.

Colm Gorey was a senior journalist with Silicon Republic