Friday, February 12, 2021

Why "Solar Geo-Engineering" To Combat Climate Change Is Nonsense

 That climate change is reaching  alarming levels is now obvious to all but the most purblind.  Leave out even the new invasion of the polar vortex which we already know is connected to ramped up warming-climate change, e.g.

 Add to that the ever earlier allergy season across the United States and Canada, with pollen season now starting 20 days earlier and pollen loads 21% higher since 1990.  A huge chunk of that is because of global warming, according to a new study in The Proceedings of the National Academies of Sciences. While other studies have shown North America’s allergy season getting longer and worse, this is the most comprehensive data with 60 reporting stations and the first to make the required and detailed calculations that could attribute what’s happening to human- caused climate change.  How has this come about?

We now know the CO2 concentration currently  in the atmosphere (415 ppm)  hasn't been seen in 12 million years. This condition  is rapidly pushing the climate back to its state in the Eocene Epoch, over 33 million years ago, when no ice existed on either pole. This mode of positive feedback is what we're faced with in the melting of the Arctic, see e.g.

This  concept of positive feedback  was well explicated by Carl Sagan in one of his essays, 'Ambush : The Warming of the World'in his book:  'Billions and Billions: Thoughts on Life and Death at the Beginning of the Millennium':
"Melting of ice caps (already occurring) results in diminished albedo (reflection of solar radiation back into space), and a darker Earth surface - with more infrared radiation absorbed - reinforcing the tendency while enhancing the melting effect, leading to further darkening of the surface, reduced albedo and more melting."
This positive feedback melting elicited a pointed question from Harvard climate science  Prof. James Anderson in a FORBES interview (in 2019): 
 "Can we lose 75-80 percent of permanent ice and recover? The answer is no.
In other words, with that vast, reflecting ice surface gone, humans will have to figure out an alternative means of raising the albedo..  Basically, to avert such positive feedback would require perhaps the most monumental  engineering  effort  in the history of mankind -  dwarfing anything seen  hitherto. It would have to be mounted to reflect as much sunlight away from the Earth's poles as the melting ice sheets are now..   But here's the rub: short of launching into space twenty or so vast reflectors of 20 square kilometers surface each - likely at a cost of $2 trillion per reflector (conservative estimate) - that isn't going to happen.  
Now Ezra Klein, writing in a recent NY Times piece:
 Offers an alternative approach based on a book by Elizabeth Kolter, e.g.:
"The central theme of the Pulitzer Prize-winning author and journalist Elizabeth Kolbert’s new book, “Under a White Sky: The Nature of the Future.” is there is no going back. We will not return to a prelapsarian period where humans let nature alone. Indeed, as Kolbert shows, there is no natural nature left — we live in the world (and in particular, a climate) we altered, and are altering. The awful knowledge that our interventions have gone awry again and again must be paired with the awful reality that we have no choice save to try to manage the mess we have made.
 I wanted to focus on one that obsesses me: solar geoengineering. To even contemplate it feels like the height of hubris. Are we really going to dim the sun?

 We discuss the prospect of intentionally sending sulfurous particles into the atmosphere to dim the sun, whether “carbon capture” technology could scale up to the levels needed to make a dent in emissions levels."

Let's first  be clear there is no actual "dimming" of the Sun.  That would require altering our star's radiative opacity which is clearly beyond humanity's technological achievement level and may well be beyond any advanced civilization's as well.   We can express the basic equation of radiative transfer in the form:
= -kn In + jn.

Where the transfer is attenuated by the first term on the right side with the opacity ( kn )  defined in terms of the number density  n of absorbing particles and the absorption cross section  sn:
kn = n sn

The reduction in solar radiation intensity  In  in situ is not what Klein is proposing.  Rather he is proposing an increase in the opacity of Earth's atmosphere by injecting billions of tons of sulphur dioxide into the upper atmosphere to increase cloud cover. In this case the radiative transfer equation that applies is:
 -dI/dt (1/k r ) = I – J
Where k is a mass scattering coefficient, r  is the molecular density (e.g. in cloud cover) and J is the vector source function for a specific intensity I.  Hence, if ample SO2 can be injected into the upper atmosphere then r  can be increased enough to diminish radiation intensity associated with heat  - in other words,  infrared radiation.  
While the idea looks neat on paper it would actually invite catastrophe and make conditions much worse.
Even if the mechanical- engineering  problems could be solved (including increased to the scale needed), it would still be a god-awful idea. For one thing, SO2 in the presence of the catalyst NO2 forms sulphuric acid, H2 SO4, and this can then generate acid rain. Do we really want ten septillion tons of acid rain descending on what remaining agriculture growth areas, farms remain in a greenhouse world? Not to mention raining on humans, with concentrations of pH in the range of 2-3? Ever had H2SO4 spill onto your skin in a chemistry lab?

Beyond that, SO2 at the given altitude needed for effect can further erode the ozone layer. In excess of a certain threshold, this erosion of protective ozone leads to much higher influx of ultraviolet radiation - more skin cancers, more blindness, etc.  In effect, Klein and Kolbert's "godlike" dimming solution merely creates more problems while attempting to solve the excess heat one from global warming.   
What appears to have escaped them is there is no real technological fix for our current predicament.  Short of hoping advanced aliens can turn the Sun into a cooler K-class star, the best and most realistic solution is conservation. Oh, and not letting the global population hit 10 billion!  (Or even 9 billion.)

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