Nuclear bomb testing during the Cold War may have led to an increase of precipitation for a period of at least two years, leading to a change of rainfall patterns thousands of miles from detonation sites, new research suggests.
More than half a century ago, the nuclear arms race ramped up as world powers competed to develop nuclear weapons following heightened tensions spurred by World War II. During the Cold War of the 1950s and 1960s, the US and the Soviet Union conducted nuclear testing at various remote sites around the world, from the South Pacific to the desert of the American Southwest. Many of these testing sites bear the scars today and some even remain radioactive, but what happens at a nuclear site does not stay there. Between 1962 and 1964, radioactive pollution spread throughout the atmosphere, ionizing the air and releasing electric charges that altered rainfall patterns.
Researchers at the University of Reading in the UK determined how electric charges released by radiation from test detonations affected rainclouds at the time by reviewing historical records between 1962 and 1964 from two weather stations in the United Kingdom. Weather records were then compared to days with high and low radioactively-generated charges and cross-referenced with bomb test data.
Writing in the journal Physical Review Letters, the researchers found that clouds were visibly thicker and there was an average of 24 percent more rain on days with more radioactivity. Electrical observations show that additional atmospheric ionization caused by radioactivity during the time led to an “increase in the global circuit’s conduction current” and, in fact, the “stratospheric radioactive material was so extensively distributed in the northern hemisphere that similar electrical changes are expected widely.”
"By studying the radioactivity released from Cold War weapons tests, scientists at the time learned about atmospheric circulation patterns. We have now reused this data to examine the effect on rainfall,” said Professor Giles Harrison, lead author and Professor of Atmospheric Physics at the University of Reading, in a statement.
"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."
It is largely thought that electric charge can change how water droplets in clouds collide and combine, which could affect their size and influence rainfall. Rain produced in clouds depends on a variety of factors, including condensation rates and how quickly water droplets are able to gain mass, making them heavy enough to fall to the surface. Radioactivity can influence the charge of these droplets, using electrical force to modify and influence the clouds and their respective precipitation
The scientists conclude that their findings may be helpful for cloud-related geoengineering research to determine how electric charge might play a role in influencing rain to potentially relieve droughts or possibly prevent floods.