The scientists said, why not cool the Earth

Ученые рассказали, почему нельзя охлаждать Землю

This will lead to even worse consequences.

Trying to stop global warming by spraying aerosol particles in the stratosphere was not a very good idea: all of the benefits of slowing warming can be cut by the fall in yields because of the blackout, the authors write.

One of the most popular ideas in the field of geoengineering (directional influence on the Earth’s climate to combat anthropogenic warming) is the mass spraying in the stratosphere of aerosols containing sulphur compounds. It is assumed that such a “stratospheric veil” will reduce the amount of sunlight reaching the Earth’s surface, and slow the growth of the average temperature.

Jonathan Proctor (Jonathan Proctor) at the University of California at Berkeley and his colleagues decided to find out how the creation of such a shield from solar radiation will affect agriculture. Because large-scale geoengineering experiments is considered too risky, scientists used natural analogue and the prototype of this process is the eruption of large volcanoes. For example, the volcano Pinatubo erupted in 1991, was thrown into the atmosphere approximately 20 million tons of sulfur dioxide, which reduced global average temperature by about half a degree Celsius.

“Blackout of the planet limits the growth temperature which helps crops grow better. But since plants need sunlight, his blocking could have an impact on growth. For agriculture the negative effects of this method on the scale of equal benefits. That’s about as experimental surgical treatment: the side effects seem no better than the disease,” said Proctor, quoted by the press service of the University.

The scientists compared data on the yields of corn, soybeans, rice and wheat in 105 countries over the period from 1979 to 2009, monitored data of the illumination and satellite observation of aerosols in the stratosphere. In the years there have been two major volcanic eruptions, El Chichon in Mexico in 1982 and Pinatubo in the Philippines 1991. They found that the additional diffusion of light due to aerosols reduced the yield of all crops: for example, after the Pinatubo eruption yield of maize due to changes in ambient light have been reduced by 9.3 percent, and the yield of corn, soybeans and rice — 4.8 per cent (part of the reduction could be offset by favorable plants decrease in temperature).

Then, using climate models, they showed that by mid century the entire gain in yield from a hypothetical “veil” in the form of at least high temperatures will be closed it down because of the deteriorating light. Theoretically, farmers can adapt to reduced illumination, such as choosing more resistant varieties of it, however, the possibility and limits of such adaptation is difficult to assess.

The researchers note that in some previous works spraying atmospheric aerosols was associated with an additional yield increase due to the fact that the scattered light better reaches the leaves inside the crown. Apparently, this effect is weaker than previously thought, because the authors did not see a net increase in the yield over the lifetime of aerosols.

According to scientists, their result does not imply that the method of spraying aerosols should be abandoned, perhaps in other sectors of the economy the positive impact will be substantial. They insist that before proceeding to the experiments, you need to understand the benefits, costs, and risks of geoengineering projects, which while very little is known.

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