Blocking sunlight to cool the Earth will not save humanity’s farmland from climate change, according to a new study that dismisses a leading global warming prevention theory.
Researchers had speculated that injecting particles into the atmosphere would lower rising global temperatures enough to stop crops from dying out.
But scientists analysing the past effects of Earth-cooling volcanic eruptions showed that shielding the atmosphere damages crops as much as it helps them.
They concluded that any improvements to yield triggered by cooler temperatures would be negated by lower productivity due to reduced sunlight – making the process ineffective as a way of stopping global warming.
Some previous episodes of global cooling were caused by gases emitted during massive volcanic eruptions.
Some experts believe that humans could inject sulphate aerosols into the upper atmosphere in a similar way.
This could artificially cool Earth and alleviate the greenhouse warming caused by increased levels of carbon dioxide.
Rather like using an umbrella to create shade from the sun, experts think that a global sunshade could in theory slow warning.
For example the eruption of Mount Pinatubo injected about 20 million tons of sulphur dioxide into the atmosphere.
This reduced sunlight by about 2.5 per cent and lowered the average global temperature by about half a degree Celsius (nearly 1 degree Fahrenheit).
This type of solar geoengineering is one proposed method for helping humanity manage the impacts of global warming.
However, findings by researchers from the University of California, Berkeley, suggest that this technology might not be as effective as hoped.
‘Shading the planet keeps things cooler, which helps crops grow better’, said lead author Jonathan Proctor, a UC Berkeley doctoral candidate in the Department of Agricultural and Resource Economics.
However, plants also need sunlight to grow, so blocking sunlight can affect growth.
‘For agriculture, the unintended impacts of solar geoengineering are equal in magnitude to the benefits,’ he said.
‘It’s a bit like performing an experimental surgery; the side-effects of treatment appear to be as bad as the illness.’
Researchers say the problem in figuring out the consequences of solar geoengineering is that we can’t do a planetary-scale experiment without actually deploying the technology.
‘The breakthrough here was realising that we could learn something by studying the effects of giant volcanic eruptions that geoengineering tries to copy’, said Solomon Hsiang, co-lead author of the study and Chancellor’s Associate Professor of Public Policy at UC Berkeley.
The team linked maize, soy, rice and wheat production from 105 countries from 1979-2009 to global satellite observations of these aerosols to study their effect on agriculture.
Pairing these results with global climate models, the team calculated that the loss of sunlight from a sulphate-based geoengineering program would cancel its intended benefits of protecting crops from damaging extreme heat.
‘It’s similar to using one credit card to pay off another credit card: at the end of the day, you end up where you started without having solved the problem,’ Dr Hsiang said.
“Researchers had speculated that injecting particles into the atmosphere would” kill people.
Chemtrails is the term.