Blocking sunlight to cool Earth will NOT save humanity: Particles injected into the atmosphere may fix global warming but they could also kill off our crops by starving them of UV light

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  • Particles injected into the atmosphere cannot stop damage to crops worldwide
  • The technique may save crops from heat damage but would cut off their sunlight
  • Scientists came to the conclusion after analysing effects of volcanic eruptions 

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. 

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One proposal for solar geoengineering is to inject sulphate aerosols into the atmosphere, similar to what happens after large volcanic eruptions. The blanket of smog acts as an umbrella, reducing sunlight and temperatures a few percent to counter global warming. However, according to the latest study this will kill off crops

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.'

Particles injected into the atmosphere cannot stop damage to crops caused by rising global temperatures, according to the latest analysis (stock image)

Particles injected into the atmosphere cannot stop damage to crops caused by rising global temperatures, according to the latest analysis (stock image)

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.

WHAT ARE THE SIDE EFFECTS OF GEOENGINEERING STRATEGIES?

Scientists have proposed all sorts of solutions to fight climate change, including a number of controversial geoengineering strategies.

Among the many include: 

Afforestation: This technique would irrigate deserts, such as those in Australia and North Africa, to plant millions of trees that could absorb carbon dioxide.

Drawback: This vegetation would also draw in sunlight that the deserts currently reflect back into space, and so contribute to global warming.

Scientists have proposed all sorts of solutions to fight climate change. File photo

Scientists have proposed all sorts of solutions to fight climate change. File photo

Artificial ocean upwelling: Engineers would use long pipes to pump cold, nutrient-rich water upward to cool ocean-surface waters.

Drawback: If this process ever stopped it could cause oceans to rebalance their heat levels and rapidly change the climate.

Ocean alkalinisation: This involves heaping lime into the ocean to chemically increase the absorption of carbon dioxide.

Drawback: Study suggests it will have of little use in reducing global temperatures.

Ocean iron fertilisation: The method involves dumping iron into the oceans to improve the growth of photosynthetic organisms that can absorb carbon dioxide.

Drawback: Study suggests it will have of little use in reducing global temperatures.

Solar radiation management: This would reduce the amount of sunlight Earth receives, by shooting reflective sulphate-based aerosols into the atmosphere.

Drawback: Carbon dioxide would still build up in the atmosphere. 

Some earlier studies suggested that aerosols might improve crop yields also by scattering sunlight and allowing more of the sun's energy to reach interior leaves typically shaded by upper canopy leaves.

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Nothing farks me off more than being robbed of sunlight. Even my 3yr old  moko when I plonk him in my lounger on the deck and tell him to stay put and lap up the sun rays cuz 'the sun Really is our friend', told me today 'it feels so nice and warm like a hug'.

"Stating the bloody obvious" (To us here at least). Best solution to prevent human induced climate change is to stop screwing with the climate and let nature do it's job.

But I believe that isn't the real issue. The whole geoengineering thing is to weaponise the atmosphere for military purposes. The "saving the planet" story as put forward by David Keith and co. is just a cover to sell it to the public.

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