The Sulphur Shield (again)

Before we move into this topic I of course wish with all my heart that we would just stop using fossil fuels. If I could, I would wave a magic wand and give every nation the right mix of nuclear and renewables to shut down every coal mine and gas pump and oil refinery on the planet. Prevention is better than a cure. A stitch in time saves nine. You get the picture.

But we are not doing it, and are close to locking in 3 degrees which many now believe is enough to start the Amazon tipping point.  In that case, we could suddenly jump into a 6 or 7 degree global warming fry-up of our worst nightmares! In other words, I did not enjoy posting yesterday’s guest blog by Byron Smith. It’s a truly awful collection of facts and data from reputable sources, and leaves me barely able to make eye contact with my children. What have we done to them!?

All of this has me thinking of desperate measures.

Have you heard of the ‘sulphur shield’? This involves spraying sulphur particulates into the atmosphere to reflect a tiny percent of the incoming sunlight, thereby cancelling out global warming. Long hoses held 30km high by blimps could pump microscopic sulphur particles into the air, acting a little like sunglasses for the planet.  I’ve wondered about it previously, and the wiki also refers to plenty of interesting studies.

Australian climate scientist David Karoly said:

As a group these solar radiation management technologies were considered to be the most risky.

The symposium found reducing sunlight has a significantly different effect than reducing greenhouse gas emissions in terms of resultant spatial effects, changes to temperature patterns over time, and effects on rainfall. Reducing sunlight leads to more cooling in the day time and in summer, whereas reducing greenhouse gases leads to more cooling at night and in winter. Hence, reducing sunlight cannot exactly offset the warming patterns due to increasing greenhouse gases.

The immediate climate responses may be local but would almost certainly have unpredictable knock-on effects for the climates of distant areas. Reflecting more sunlight in one region would cool the climate locally but, since the variations in climate are globally connected, such changes would likely affect weather and rainfall patterns all around the globe.

There may also be uncertain impacts on the ozone layer and other important areas in the stratosphere.

However, he also said:

Solar radiation management systems, in particular, would be very difficult to govern. While one of these technologies could be deployed unilaterally (by a nation or private entity, at a potential cost of more than $1 billion a year), the impacts will be global and could have unanticipated consequences.

That is, the cost of using the sulphur shield is negligible. It’s really cheap. The world economy is $70 trillion dollars a year. That means the cost to deploy the solar shield is only 1/70,000th of our global economy. OK, that’s fairly meaningless because who is going to pay what? Let’s pretend America wakes up with horrible climate consequences on their agriculture. (Oh, wait, that’s already happening). They decide to have their military “Just fix this climate thang!” They push the button marked “Sulfur gun”.
(They don’t just think they own the planet, they also spell sulphur differently. And have ‘mad scientists’ that invent Reagan’s star wars and then go on to speculate about big guns shooting sulfur into the air!)

The ‘sulfur gun’ would only be 1/680th of the American military budget. Uncle Sam could ‘fix’ global warming for us all on his lonesome. They have huge reserves of sulfur in all the nasty sour crude and tar sands and oil shale they’re mining and refining. They could do this, unilaterally. It’s not like they’ve never taken any military action unilaterally before! 😉

(However, please note that wikipedia also reports that according to Nobel Prize winner Paul Crutzen the annual cost of enough stratospheric sulfur injections to counteract effects of doubling CO2 concentrations would be $25–50 billion a year.[2] This is over 100 times cheaper than producing the same temperature change by reducing CO2 emissions.[16])

So then the real question becomes whether the cure is worse than the disease? The wiki says:

  • Drought, particularly monsoon failure in Asia and Africa is a major risk.[24]
  • Ozone depletion is a potential side effect of sulfur aerosols;[25][26] and these concerns have been supported by modelling.[27]
  • Tarnishing of the sky: Aerosols will noticeably affect the appearance of the sky, resulting in a potential “whitening” effect, and altered sunsets.[28]
  • Tropopause warming and the humidification of the stratosphere.[26]
  • Effect on clouds: Cloud formation may be affected, notably cirrus clouds and polar stratospheric clouds.
  • Effect on ecosystems: The diffusion of sunlight may affect plant growth.[29][30][31]but more importantly increase the rate of ocean acidification by the deposition of hydrogen ions from the acidic rain[32]
  • Effect on solar energy: Incident sunlight will be lower,[33] which may affect solar power systems both directly and disproportionately, especially in the case that such systems rely on direct radiation.[34]
  • Deposition effects: Although predicted to be insignificant,[35] there is nevertheless a risk of direct environmental damage from falling particles.
  • Uneven effects: Aerosols are reflective, making them more effective during the day. Greenhouse gases block outbound radiation at all times of day.[36]

That all sounds pretty bad, but 3 degrees warming seems locked in and has lists as bad or worse. If 3 degrees actually acts as a tipping point towards 6 degrees of warming, then the consequences above would look like the ‘good old days! Also, there does not seem to be as neatly summarised a consensus about the consequences of a sulphur shield. I’m not getting the sound-byte warnings that tell me just how bad this might really be. Are we talking about a permanent failure of the monsoons in India? Is it total, or partial?

And how much of the Ozone layer would we really lose? This 2008 study suggests that it wouldn’t be the total destruction of the Ozone layer at all.

The large burden of sulfate aerosols injected into the stratosphere by the eruption of Mount Pinatubo in 1991 cooled Earth and enhanced the destruction of polar ozone in the subsequent few years. The continuous injection of sulfur into the stratosphere has been suggested as a “geoengineering” scheme to counteract global warming. We use an empirical relationship between ozone depletion and chlorine activation to estimate how this approach might influence polar ozone. An injection of sulfur large enough to compensate for surface warming caused by the doubling of atmospheric CO2 would strongly increase the extent of Arctic ozone depletion during the present century for cold winters and would cause a considerable delay, between 30 and 70 years, in the expected recovery of the Antarctic ozone hole.

Also, this study says suggests the whole field is still in its infancy:

Some areas of research remain unexplored. Although ozone may be depleted, with a consequent increase to solar ultraviolet-B (UVB) energy reaching the surface and a potential impact on health and biological populations, the aerosols will also scatter and attenuate this part of the energy spectrum, and this may compensate the UVB enhancement associated with ozone depletion. The aerosol will also change the ratio of diffuse to direct energy reaching the surface, and this may influence ecosystems. The impact of geoengineering on these components of the Earth system has not yet been studied. Representations for the formation, evolution and removal of aerosol and distribution of particle size are still very crude, and more work will be needed to gain confidence in our understanding of the deliberate production of this class of aerosols and their role in the climate system.

Indeed, the conclusions of this JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, D16101, doi:10.1029/2008JD010050, 2008, says on page 13 of their PDF

[31] Mitigation (reducing emissions of greenhouse gases) will reduce global warming, but is only now being seriously addressed by the planet. Whether we should use geoengineering as a temporary measure to avoid the most serious consequences of global warming requires a detailed evaluation of the benefits, costs, and dangers of different options. MacCracken [2006], Bengtsson [2006], Cicerone [2006], Kiehl [2006], and Lawrence [2006] all express concern about geoengineering. Robock [2008b] lists 20 reasons that argue against the implementation of this kind of geoengineering. The work here helps to document some benefits of geoengineering (global cooling and preservation of Arctic sea ice), but also the possible side effects on regional climate, item 1 on that list.

The side-effects of the decreased Ozone layer cannot be too bad, when one considers who is pushing the sulphur shield.

Professor Paul Crutzen, winner of the 1995 Nobel Prize for his work on the Antarctic ozone hole, has proposed an emergency geoengineering solution to cool off the planet: dump huge quantities of sulfur particles into the stratosphere to reflect sunlight. His paper, “Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma?” was published in the August 2006 issue of the journal Climatic Change. A recent editorial in the New York Times by Ken Caldeira called for more research into geoengineering schemes like this to cool the planet, proposing that 1% of the $3 billion federal Climate Change Technology Program should be spent thusly.

If Paul Crutzen is advising the sulphur shield as an emergency stop-gap, then it cannot be too bad for the Ozone layer.

It’s an interesting area of study. For now we should seal this scheme behind a glass door that reads “Break only in case of emergency”. Sadly, with the world’s inaction on climate change and suspicion of nuclear power, it seems like we are rapidly approaching one!

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