Cosmic rays from exploding stars can influence weather on Earth, a pioneering study has found.
There has long been speculation that cosmic rays – highly charged particles travelling through space – may affect our atmosphere.
But now researchers at Denmark Technical University show that the rays trigger the formation of ‘seeds’ in our atmosphere.
These seeds allow clouds to form around them – and can potentially have a cooling effect on the Earth.
Cosmic rays from exploding stars can influence weather on Earth, a pioneering study has found. Pictured is a colourised Nasa observation of the debris expanding from an exploding white dwarf star captured in 2015
Cosmic rays can be flung out by our own sun and from exploding stars – supernovae.
The researchers claimed the discovery helped fill in a mysterious gap in our knowledge of our climate and may help to explain unusual periods of warmth and cold during the past 2,000 years.
The researchers said the effect of cosmic rays ‘gives a physical foundation to the large body of empirical evidence showing that solar activity plays a role in variations in Earth’s climate.’
As clouds are essential for the amount of solar energy reaching the surface of Earth, they said the implications can be significant for our understanding of why climate has varied in the past and also for future climate changes.
They cited as examples the Medieval Warm Period around year 1000AD – around 1-2C (1.8-3.6F) warmer than in the early 20th century.
The other was the Little Ice Age 1300-1900AD when temperatures dropped across northern Europe by 0.6C (1F) and glaciers advanced across the Alps.
Both periods were consistent with changes in solar activity.
Dr Henrik Svensmark, lead researcher of the paper in Nature Communications said: ‘Finally we have the last piece of the puzzle explaining how particles from space affect climate on Earth.
There has long been speculation that cosmic rays (artist’s impression) – charged particles travelling through space – may affect our atmosphere. But now researchers show that the rays trigger the formation of ‘seeds’ in our atmosphere which allow clouds to grow around them
‘It gives an understanding of how changes caused by Solar activity or by supernova activity can change climate.’
The effect of cosmic rays on the Earth’s atmosphere was simulated using a cloud chamber – a sealed container which replicates the conditions in the upper atmosphere.
When the ions entered the chamber, they caused cloud condensation nuclei – sometimes known as ‘cloud seeds’ – to form.
These are particles 0.2 nanometres in size – about twice the size of a helium atom.
The cloud seeds allow the water vapour to condense around them.
The authors said more cloud condensation nuclei mean more clouds and a colder climate.
The researchers said that ‘When the qun is lazy, magnetically speaking, there are more cosmic rays and more low clouds, and the world is cooler.
When the sun is active fewer cosmic rays reach the Earth and, with fewer low clouds, the world warms up.’
Dr Hamish Gordon, Post-doctoral researcher, Institute for Climate and Atmospheric Science, University of Leeds, said: ‘This is an interesting and plausible result, and if it stands up to more detailed scrutiny it may prove an important contribution to aerosol microphysics.’
The research was published in Nature Communications.