Naked Science Forum

Life Sciences => The Environment => Topic started by: katieHaylor on 14/09/2017 16:33:44

Title: Can we mitigate global warming by reflecting sunlight?
Post by: katieHaylor on 14/09/2017 16:33:44
James says:

Could we use absorption or reflection of sunlight by particulate matter to postpone global warming? This is said to occur after a massive dust particle release into the atmosphere and stratosphere with asteroid collision with us, or nuclear war or gigantic volcanic activity. Possibly silicates, aluminium?

Land based experiments might estimate a graded amount to release. I don't suggest release to a level to dramatically reduce sunlight, just a tiny amount. The particles might eventually disperse, fast or slowly, depending on the height above the earth or the nature of the particles. They should degenerate and disperse over time. Krakatoa apparently altered the climate for some time.

The sky might change colour a little. There may be other consequences, but would they be as bad as the consequences of climate change? I don't have faith in us humans taking adequate or timely reduction of carbon dioxide emission to avoid the consequences. Even if we totally stopped our own CO2 emission overnight and stopped forest clearing we can't avoid rapid global warming now. Those that believe we can may have their heads in the sand.

Are there any other radical or useful approaches that may possibly assist - biological or physical?


What do you think?
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: Colin2B on 14/09/2017 17:23:41

James says: Could we use absorption or reflection of sunlight by particulate matter to postpone global warming? This is said to occur after a massive dust particle release into the atmosphere and stratosphere with asteroid collision with us, or nuclear war or gigantic volcanic activity.


Following 9/11 all aircraft in USA were grounded, hence no contrails. I heard reports that over the next 2 days there was a slight increase in ground temp. I heard a similar report that contrails affect temperatures over part of Indian Ocean. Don't have references but might be worth following up.
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: evan_au on 14/09/2017 20:10:50
Some years ago there was a proposal in the UK to test some of the technologies needed to deliver chemicals like sulphates into the upper atmosphere by pumping them into a hose held aloft with a balloon.

For the test they were just going to use water, to see if their pumps functioned properly.

However, some people did not even want to know if the technology was feasible. I think they were afraid that it might divert attention from "greener" technologies, so a moratorium was placed on geoengineering experiments.

That just means that if/when such technology is needed, it will need to be developed and tested, instead of being available "just in case".
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: tkadm30 on 14/09/2017 20:16:39
However, some people did not even want to know if the technology was feasible. I think they were afraid that it might divert attention from "greener" technologies, so a moratorium was placed on geoengineering experiments.

Citation needed.
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: tkadm30 on 14/09/2017 20:36:13
The sky might change colour a little.

No kidding... I thought the sky was pink already.

Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: Kryptid on 14/09/2017 23:06:39
Intentionally injecting large amounts of particulate matter into the atmosphere sounds like a recipe for trouble: even inert substances like silica can cause health problems if inhaled.
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: evan_au on 15/09/2017 06:56:17
Quote from: evan_au on Yesterday at 20:10:50
Quote from: evan_au
However, some people did not even want to know if the technology was feasible. I think they were afraid that it might divert attention from "greener" technologies, so a moratorium was placed on geoengineering experiments.

Citation needed.
The particular project was called SPICE, see:
https://www.theguardian.com/environment/blog/2012/may/17/geoengineering-spice-project-research

I also ran into this report on a UK parliamentary investigation into Geoengineering (116 pages)
https://publications.parliament.uk/pa/cm200910/cmselect/cmsctech/221/221.pdf
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: tkadm30 on 15/09/2017 09:34:53
The particular project was called SPICE, see:
https://www.theguardian.com/environment/blog/2012/may/17/geoengineering-spice-project-research

I also ran into this report on a UK parliamentary investigation into Geoengineering (116 pages)
https://publications.parliament.uk/pa/cm200910/cmselect/cmsctech/221/221.pdf

Can you please quote the part where it says a "moratorium was placed on geoengineering experiments"?
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: puppypower on 16/09/2017 11:34:41
Didn't old timer coal fired steam plants give off a lot of particulate matter. And wasn't it the same crowd, who now cries global warming, responsible for reducing the particulate emissions that could helped global warming by reflecting sunlight?
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: Colin2B on 17/09/2017 09:08:02


Didn't old timer coal fired steam plants give off a lot of particulate matter. And wasn't it the same crowd, who now cries global warming, responsible for reducing the particulate emissions that could helped global warming by reflecting sunlight?
Not quite as simple as people make out, here's the opposite view:
http://web.stanford.edu/group/efmh/jacobson/Articles/VIII/fossil/fossil.pdf (http://web.stanford.edu/group/efmh/jacobson/Articles/VIII/fossil/fossil.pdf)


However, the point is valid that any changes can be a 2 edged sword. Take cloud cover for instance. Yes, clouds reflect sunlight and reduce radiation warming the ground, also warm moist air rising to form clouds cools the earth, but as the cloud cover increases to become stratus the air becomes more stable acting as in insulating layer and convection reduces. Also, water vapour is one of the most effective greenhouse gasses and present in large quantities so the cloud cover contributes to the warming process. As the temperature of the atmosphere rises, more water is evaporated from rivers, oceans, soil and because the air is warmer, the absolute humidity can be higher i.e. more water vapor in the atmosphere, the higher concentration of water vapor is then able to absorb more IR radiated from the ground further warming the atmosphere. The warmer air can then hold more water vapour etc - a 'positive feedback loop. However, no one is certain of the extent and importance of this feedback loop. While there are good measurements of other key greenhouse gases such as carbon dioxide and methane, there are poor measurements of global water vapor, so it is not certain by how much atmospheric concentrations have risen in recent decades or centuries. Overall, not a good idea to start messing about until we understand what is happening - not that that ever stopped the politicians.
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: tkadm30 on 19/09/2017 13:00:21
However, the point is valid that any changes can be a 2 edged sword. Take cloud cover for instance. Yes, clouds reflect sunlight and reduce radiation warming the ground, also warm moist air rising to form clouds cools the earth, but as the cloud cover increases to become stratus the air becomes more stable acting as in insulating layer and convection reduces. Also, water vapour is one of the most effective greenhouse gasses and present in large quantities so the cloud cover contributes to the warming process. As the temperature of the atmosphere rises, more water is evaporated from rivers, oceans, soil and because the air is warmer, the absolute humidity can be higher i.e. more water vapor in the atmosphere, the higher concentration of water vapor is then able to absorb more IR radiated from the ground further warming the atmosphere. The warmer air can then hold more water vapour etc - a 'positive feedback loop. However, no one is certain of the extent and importance of this feedback loop. While there are good measurements of other key greenhouse gases such as carbon dioxide and methane, there are poor measurements of global water vapor, so it is not certain by how much atmospheric concentrations have risen in recent decades or centuries. Overall, not a good idea to start messing about until we understand what is happening - not that that ever stopped the politicians.

Water vapor does not reflect sunlight like silica or aluminium particulates. It would not be possible to "mitigate" global warming with water vapor alone. Also, water vapor does not change the color of the sky, a phenomenon known as "global dimming".
Title: Re: Can we mitigate global warming by reflecting sunlight?
Post by: yor_on on 20/09/2017 03:26:16
I don't think that was the purpose of Colins post tkadm. He gave examples of why 'geo engineering' something ala Jules Verne wouldn't be such a good idea.

The last thing we've 'geo engineered' is called 'Global Warming' and we're still trying to understand what that will bring with it.