Cold War Nuclear Tests Linked to Rainfall Changes

The findings could help scientists of the future geoengineer clouds to influence rain, alleviate drought or prevent floods without the use of chemicals.

(CN) — Nuclear weapon tests during the Cold War destroyed landscapes. But they also altered the rainfall patterns of environments thousands of miles away from detonation sites, according to a study released Wednesday.

In the study published in the journal Physical Review Letters, scientists at the University of Reading discuss their research on how these test detonations, carried out mainly by the United States and the Soviet Union in the 1950s and 1960s, released electronic charges through radiation which in turn affected the nearby rainclouds.

Among other things, the Cold War involved a treacherous race to develop nuclear weapons as the world’s superpowers tried to assert military dominance over each other and demonstrate their capabilities during the heightened tensions that came after World War II. Test detonations of these weapons were carried out in remote areas of the world — including the Nevada desert and on Pacific and Arctic islands — but radioactive pollution spread throughout Earth’s atmosphere. 

The results of pollution from test detonations could be seen in almost all aspects in life, with radiation levels poisoning the environment and people, even as nuclear accidents like Chernobyl made large swaths of the landscape uninhabitable.

Radioactive pollution made its way into the ground, into bodies of water and especially into the atmosphere. Additionally, the radioactivity ionized the air, which then released an electric charge to the clouds above.

The study involved the use of historic records written between 1962 and 1964 at a research station in Scotland to compare data from days with high and low radioactively-generated charge. They found that the clouds became visibly thicker and on average 24% more rain fell on the days with more radioactivity than less.

“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 Giles Harrison, lead author and professor of atmospheric physics at the University of Reading. “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.”

The topic of electricity modifying water droplets has been difficult to study in the past for several reasons, with the most significant being that the subject is in the atmosphere. It has long been suspected that electric charge modifies how water droplets form in the clouds, therefore potentially affecting the size of droplets and influencing rainfall. 

This study stands apart for being able to definitively investigate this phenomenon by combining the bomb test data with weather reports from the period. The authors believe that by learning more about how electric charge affects non-thunderstorm clouds, today’s scientists can achieve a better understanding of important weather processes.

Researchers from the University of Reading, the University of Bath and the University of Bristol, also studied pertinent records from well-equipped Met Office research weather stations at Kew near London and Lerwick in the Shetland Isles. The Shetland site, located 300 miles northwest of Scotland, was relatively unaffected by other sources of human-caused pollution, making it an ideal test site to observe rainfall patterns. The authors note that although this probably occurred elsewhere as well, without as much of a controlled environment it would have been much harder to detect rain effects.

They found it was easiest to measure atmospheric electricity on clear days, so they used the Kew measurements to identify nearly 150 days where there was high or low charge generation over the United Kingdom while it was overcast in Lerwick. The results found that the Shetland rainfall on these days exhibited differences which disappeared after the major radioactivity episode was over. 

A similar study proved that the filtration systems within coal-fired power stations produce ultrafine dust particles that can modify and redistribute rainfall patterns and can have considerable impacts on the environment.

These findings could prove to be valuable for cloud-related geoengineering research, a field that explores how electric charge could influence rain, relieve droughts or prevent floods without the use of chemicals.

Currently, Harrison is leading a project on clouds in the United Arab Emirates to investigate electrical effects on dust and clouds, as part of their national program in Rain Enhancement Science. The results from this study will ultimately help to show the typical charges possible in natural non-thunderstorm clouds.

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