Changing winds in the jet stream caused by bizarre and scarcely understood ‘waves’ could cause catastrophic crop failures and severe droughts around the world, a study claims.
Food supplies would be at risk across North America, Western Europe and Asia, causing starvation and threatening the lives of millions of people.
A study from Oxford University looked into what happens when the jet stream is subjected to mysterious fluctuations called Rossby waves.
These swirls of hot air could have an extreme knock-on effects for the world’s major food producing regions.
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A study from Oxford University looked into what happens when the jet stream is subjected to mysterious fluctuations called Rossby waves. These swirls of hot air could have an extreme knock-on effects for the world’s major food producing regions, killing crops (stock)
The jet stream is a strong wind, circling the northern hemisphere about five miles above the earth’s surface.
It has a huge impact on climate in various parts of the world, creating the conditions which agriculture and societies depend on.
Random fluctuation to the jet stream is natural, with atmospheric Rossby waves causing the wind to move north or south.
But major climactic changes can lead to synchronised heatwaves.
Study lead author Dr Kai Kornhube said: ‘Co-occurring heatwaves will become more severe in the coming decades if greenhouse gases are not mitigated.
‘In an interconnected world, this can lead to food price spikes and have impacts on food availability even in remote regions not directly affected by heatwaves.’
The team combed through 40 years of data and found the specific wave patterns responsible for spiking temperatures over all three continents.
When they found these wind patterns there was a 20-fold increase in the likelihood of simultaneous heatwaves, the researchers found.
Dr Kornhuber said: ‘Until now this was an under explored vulnerability in the food system.
‘We have found that during these events there actually is a global structure in the otherwise quite chaotic circulation.
‘The bell can ring in multiple regions at once and the impacts of those specific interconnections were not quantified previously.’
Rising temperatures reduce rainfall, dry out soils and kill crops, causing food prices to rise and social unrest.
Western North America, Western Europe and the Caspian Sea region are particularly high-risk, becoming focal points for the poor conditions.
Study co-author Dr Elisabeth Vogel, of Melbourne University in Australia, said: ‘During years in which two or more summer weeks featured the amplified wave pattern, cereal crop production was reduced by more than ten per cent in individual regions, and by four per cent when averaged across all crop regions affected by the pattern.’
The worst waves hit in 1983, 2003, 2006, 2012 and 2018, and the impact of these mysterious waves was profound.
In years where the Rossby waves featured in two or more summer weeks, the researchers, using their climate modelling programme, found a reduction in yield of more than ten per cent in some regions.
Droughts and simultaneous heatwaves will hit Northern America, Western Europe and Asia, leaving crop yield and human survival in tatters (stock)
Co-author Dr Dim Coumou said: ‘Normally, low harvests in one region are expected to be balanced out by good harvests elsewhere.
‘These waves can cause reduced harvests in several important breadbaskets simultaneously, creating risks for global food production.’
Rossby waves are, so far, only a theory. But there is a growing body of proof suggesting their existence and impact is real.
Scientists believe Rossby waves will grow in stature and importance as the planet warms.
It is still unknown if the waves are linked to climate change and greenhouse gases, but further research will seek to find a link.
Dr Kornhuber said: ‘Even if the frequency or the size of the [Rossby] waves doesn’t change, the heat extremes linked to the patterns will become more severe, because the atmosphere as a whole is heating.’
The team hopes their findings will help people understand and prepare for future risks.
Coauthor Dr Radley Horton said: ‘If climate models are unable to reproduce these wave patterns, risk managers such as re-insurers and food security experts may face a blind spot when assessing how simultaneous heat waves and their impacts could change in a warming climate.
Professor Theodore Shepherd, a climate science at the University of Reading who was not involved in the study, said of the findings: ‘We have strong observational evidence of this wave pattern.
‘What is open for discussion is how it might respond to climate change.’
The findings were published in the journal Nature Climate Change.
