Hello Andrew,
see section 7.4.6 of IPCC AR5 :
http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter07_FINAL.pdf
The summary is
"Cosmic rays enhance new particle formation in the free troposphere, but
the effect on the concentration of cloud condensation nuclei is too weak
to have any detectable climatic influence during a solar cycle or over
the last century (medium evidence, high agreement). No robust
association between changes in cosmic rays and cloudiness has been
identified. In the event that such an association existed, a mechanism
other than cosmic ray-induced nucleation of new aerosol particles would
be needed to explain it. {7.4.6}"
Best
Olivier
Cosmic rays cause cloud condensation nuclei. They are therefore
believed to affect cloudiness, and therefore climate. If we made more
cosmic rays, that would likely make it more cloudy. Whether this was a
warming or cooling effect would depend on whether it was cirrus or
cumulus clouds (NB, sometimes making cirrus ultimately removes water,
resulting in less cirrus)
Cosmic rays are almost all protons, with an typical energy peak
distribution of 0.3GEv. (4.8×10^−11 J). No idea if that's the right
energy for CCN, but we can tweak that later.
Creating artificial cosmic rays is possible, using a linear particle
accelerator. This is similar to an ion thruster, as used in space probes.
To affect climate, you'd probably have to get densities of the order
of 1/s/sqm (more on that, later).
360 million square kilometers of ocean is 360tn sqm or 3.6x10^14sqm.
You don't really want to send particles into people, and the cleaner
air over the oceans makes them more effective.
A kilo of hydrogen contains 6x10^26 protons.
That means 1kg of H2 gives you enough material for 1.6x10^12s =
roughly 50 years - so a satellite could easily carry enough material
to do the job.
Power is 3.6x10^14 x 4.8x10^-11J/s = 17kW - again, well within what a
satellite could muster (roughly 100sqm of solar panels, at around 20%
panel efficiency (conservative) and 50pc conversion (made up)
efficiency).
Cheap satellites are about $50m - well within the capabilities of a
rich philanthropist. Even if this is not cheap, it's still only
perhaps 500m
If I'm out by 5 orders (1 ray per sq cm, not per sq m each second),
then that's only 10,000 satellites. That's expensive, but not
outlandish. Superficially, that would be $500bn at the lower cost, but
there is likely a 10x or 100x experience curve cost reduction, meaning
the whole programme would be about $5-50bn max.
As an alternative, you could use aircraft or balloons, but beam
attenuation would be a serious issue. 40km balloons can be launched,
albeit with small payloads. They would fly at the bottom of the
mesosphere, over 99.9pc of the atmosphere. So maybe beam attenuation
would be tolerable, at that height. I don't know how to calculate it,
but I'm guessing it would be cms to kms - so not really far enough to
make a difference to climate. You could perhaps have mountaintop
accelerators with very high powers, and a sweeping beam (like a
lighthouse). If the power requirement was GW-range, then maybe the
beam range would be a hundred km, or so. That might be enough to work,
but it would have some pretty significant effects on local atmospheric
chemistry - so probably not a good idea.
Any thoughts from anyone?
Andrew Lockley
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BAMS State of the Climate 2017
<https://www.ametsoc.org/ams/index.cfm/publications/bulletin-of-the-american-meteorological-society-bams/state-of-the-climate/>
has an aerosol section in the Global Climate chapter
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