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Geoengineering Could Reduce Critical Global Rainfall

A plan to reduce the severity of manmade global warming by blocking incoming sunlight would have the problematic side effect of reducing precipitation worldwide, with a particularly steep reduction in the monsoon seasons in East Asia and Africa, a new study found. The study refutes the notion put forward by some proponents of so-called “geoengineering” schemes that the Earth’s climate would simply return to its pre-industrial state if the warming that has taken place since that time were reversed.

Some of the geoengineering proposals to date, including Solar Radiation Management. 
Click image to enlarge.

Instead, the study, published in the Journal of Geophysical Research-Atmospheres, found that trying to solve the global warming problem through geoengineering would have the opposite effect of what global warming is already doing, as data shows that average global precipitation is increasing, and in many parts of the world, there has already been a spike in the number of extreme precipitation events.

The research found that geoengineering would cause a drop in both the amount and frequency of precipitation worldwide, particularly over some land areas. In the dozen computer models used for the study, monsoonal rains dropped by an average of 7 percent in North America, 6 percent in East Asia and South America and 5 percent in South Africa. Those seasonal rains are vital for sustaining crops in highly populated regions and substantial changes to monsoon seasons could have wide ramifications for food availability and political stability. In addition, the study found that average global precipitation could drop by about 4.5 percent.

Climate researcher John Fasullo, one of the authors of the study, said geoengineering options present a “Pick your poison” dilemma. “Climate change is one ill, but geoengineering contains its own downsides as well.”

The study focused on one geoengineering proposal that has gained traction among geoengineering proponents and some policymakers looking for a technical fix to the climate challenge. The plan, known as solar radiation management, involves injecting small particles that reflect sunlight, or possibly even giant mirrors, into the upper atmosphere, to reduce the amount of incoming solar radiation, thereby cooling the Earth’s surface.

The new study simulated the effects of using solar radiation management in an environment in which the amount of greenhouse gases in the air is four times the level observed at the start of the industrial revolution. That is far higher than today, since the concentration of carbon dioxide (CO2), the main long-lived greenhouse gas, in the atmosphere has not yet doubled from the preindustrial level.  

The study found that blocking some incoming solar radiation would alter the temperature profile of the atmosphere by cooling the lower atmosphere. At the same time, increased amounts of greenhouse gases would continue to warm the air at higher altitudes. That would make the atmosphere more stable and reduce the amount of storminess that would occur, said Simone Tilmes, a scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colo.

According to Tilmes, “it’s not possible” for geoengineering to bring the climate back to where it was in preindustrial times, because the climate system will still be responding to the increased amounts of greenhouse gases in the atmosphere.

Change in average precipitation (without geoengineering) projected for the end of the 21st century, showing a wetter planet overall.
Click image to enlarge. Credit: IPCC Fifth Assessment Report.
 

For example, increased levels of CO2 cause plants to release less water vapor through evapotranspiration, which can reduce precipitation over land, Tilmes said. That response would continue to occur even if geoengineering were to succeed in bringing global average surface temperatures back to where they were before the industrial era began in the mid-to-late 19th century.

The study is part of an international effort among climate scientists to gain insight into the possible side effects of the geoengineering proposals that have been put forward as last-ditch plans to diminish the severity of global warming. Interest in geoengineering has increased in recent years as efforts to reduce global emissions of greenhouse gases have stalled.

Based on the study, a benefit of geoengineering — in addition to reducing global average surface temperatures — could come into play with extreme precipitation events. Such events present the risk of flooding, as was seen recently in Colorado when a 1-in-1,000 year rainfall event led to extensive flooding.

In a world with more CO2, precipitation extremes are becoming more severe and more common. According to the National Climate Assessment, released in draft form in January, the most extreme precipitation events have increased in every region of the contiguous U.S. since 1950, a trend that the study attributed partly to increased evaporation from manmade global warming. At the same time, a more intense water cycle is likely to lead to more frequent and severe drought in other areas, such as in the Southwestern U.S.

However, if the amount of solar radiation reaching the Earth’s surface were reduced, the study suggests that the frequency of heavy precipitation events would also decrease. In fact, relative to preindustrial conditions, geoengineering would produce about a 20 percent reduction in heavy precipitation events globally, with significant regional variations, Fasullo said.

It might be possible to pursue a middle-of-the-road geoengineering option that would offset some of the manmade warming while avoiding a harmful impact on precipitation — a “Goldilocks” scenario — but studies on such options have not yet been completed, and Fasullo and Tilmes both expressed skepticism that such a geoengineering sweet spot exists.

“We have to be aware of the problems” with geoengineering, Tilmes said. “It helps the conversations and the arguments about the impacts of geoengineering.”

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Geoengineering Faces Dilemma: Experiment or Not?
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Rogue Geoengineering Could ‘Hijack’ World’s Climate

Comments

By Gerald Hartley (Ridgecrest, CA 93555)
on November 5th, 2013

The problem with geoengineering is that once it is instituted and we find that it has harmful effects we didn’t anticipate or are worse than those we do anticipate it can’t be reversed.  The skies will not be as clear as they are now with a milky appearance during the day and the stars will not be as bright and clear as they are now.  Since I am an amateur astronomer I would not be pleased.

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By Dave (Basking Ridge, NJ 07920)
on November 5th, 2013

The specific finding reported here relating to a prediction of generally reduced precipitation amounts with a geo-engineered reduced solar approach to climate change control, sounds reasonable. I can imagine and accept that outcome as one of the likely long term climate consequences.

However, the style of this report might lend the false impression to some that the overall consequences of massive geo engineering are therefore more or less identifiable. Whenever such schemes are discussed it is a good idea to keep in mind why that would be a false assumption. The global climate is a complex system in the full technical sense. As such it is full of interdependencies with, or influences, many other systems representing a cascading network of diverse linear and non linear effects. As a result, the net response to and dynamic impacts of massive geo-engineered changes directed at climate control should not be assumed to be fully identifiable, easily characterized, systematic or otherwise generally linear.

For this reason many scientists have profound concerns over the possibility and indeterminate nature of significant unintended consequences of massive geo engineering, whether it is by aggressive solar radiation management or large scale addition of iron to the oceans, etc.

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By kermit
on November 5th, 2013

The only geoengineering I am reasonably comfortable with would be anything that attacks the problem directly, by removing greenhouse gases from the atmosphere. Biochar sequestration doesn’t hurt. I don’t know if it can be scaled up enough to do the job, however. Painting all roofs white helps a little, without changing the atmospheric chemistry or reducing the light the biosphere gets. But we’re not doing what we have to do to minimize further damage - halting further coal plant building, stopping fracking, oil drilling, and the like. I am not optimistic.

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By brad (brisbane)
on November 5th, 2013

they are already doing this they are also called CHEMTRAILS and they put other things in there that make people sick,,drought is already happening   ,,  AGENDA 21

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By Ian Miller (Lower Hutt / New Zealand / 5010)
on November 6th, 2013

The “greenhouse effect” depends on the integral of gas produced, the oceans acting as a buffer, and if we stopped production of industrial CO2 completely, we would probably still get sea-level rises of 7 - 10 meters minimum. We cannot simply stop such production, therefore the only way to avoid losing our coastal cities and coastal farm production (and half of Bangla Desh) is to ensure that the rate of snow falling onto the major ice sheets equals the rate of ice melting from them. That, in my view, is what geoengineering should focus on. We may not know how to achieve this, because it will require altering heat inputs to specific regions to get vaporization and wind patterns right, but we should at least study it and try. Yes, with any geoengineering there will be prices to pay, but there will also be very horrible prices to pay if we do nothing. The environmental debts are already in place - our only choices are how we pay and who pays because the planet will extract its price.

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By Dane Wigington (bella Vista Ca 96008)
on November 7th, 2013

Not only CAN geoengineering reduce global rain fall, geoengineering IS RADICALLY REDUCING RAIN.
When will the “elephant in the room” be admitted to? The planet has been subjected to ongoing climate engineering programs for decades. The decimation being caused by these programs is already approaching cataclysmic.
Any that care about a future for planet earth should investigate “geoengineering”, and then do their best to help the rest of us expose these criminal climate modification programs.

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By Dave (Basking Ridge, NJ 07920)
on November 8th, 2013

@Ian

Seriously? Hypothetically, IF it were even possible to focus solely on thermally isolating the poles, then the amount of additional heat then held back across the planet that did not go towards melting ice at the poles would accelerate warming in sub polar latitudes. The resulting enhanced heat gradient between the equator and the poles would then amplify the requirement for this hypothetical geo-e thermal isolation at the poles leading to more lower latitude heating and so on in a nasty feedback loop until the scheme collapsed under it’s own ‘weight’. The oceans and poles buffer global warming. We need them to be involved to slow GW down. If by some magic we even could take them out of the global heat equation we would still have a bigger climate problem, not to mention the repercussions from such massive reshaping of global weather systems.

Are you really quite so willing to accept the risks of your particular hypothetical non existent geo-e scheme on behalf of the rest of us? That’s the type of problem you run into with massive geo-e. Just who would it be that should make such choices and what does accountability even mean in this context anyway?

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By Shepard Ambellas (Haiku)
on November 10th, 2013

This is all addressed in the new documentary SHADE the Motion Picture.

http://www.youtube.com/watch?v=V4VFYRaltcc

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By Duff Smith (Key Largo, FL)
on November 11th, 2013

Two geoengineering methods not mentioned in this article is the dispersion of alkalizing minerals in the ocean to offset acidification and the placement of cometary debris in Lagrangian point orbit to reduce sunlight.

Has anyone tried to harvest the valuable minerals from the discharge of desalinization plants? This could be the least exorbitant way to offset the heavy metals loading from the dispersion of alkalizing minerals.

If sunlight is to be reduced then it should be done in a way that produces power.

That idea of placing and dispersing cometary material in Lagrangian point orbit sounds like an interesting proposal for Venus; at least I would make that planet the guinea pig before trying anything that radical on Earth.

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