Trillions of light dispersing discs in space to shield the sun

Tarp wrapping is already used for some glaciers.

Melting German Glacier Gets Sunscreen, Again : TreeHugger

Tom

 

Blocking sunlight before it reaches the Earth is a very simple-minded approach. I'm sure many photosynthesizing plants and animals, including those who rely on photosynethic capacity, will LOVE this idea. lol

 

Sure it will cost a fortune, but we can keep driving SUVs. :madgrin:

 

How about inserting SUVs into space to block the sunlight?

Tom

 

Its going to cost even more to get them into orbit. Probably only one or two per rocket launch. :madgrin:

 

Wouldn't it be more effective/efficient just to shoot SUV drivers into
space. I'm sure they'd pack tighter than the vehicles.

If weight is an issue, use a solar dryer/dessicator to take the water
out, which it would be a good idea to keep regardless.

 

Weight is the primary issue, so launching dessicated SUV drivers is the most cost effective of these choices.

 

saw a report on Sci-Fri podcast from NPR news. great idea, but what if its a mistake???

hundreds of Billions to find out, and it might not be fixable. what if we get them up there, they block too much light and we cant get rid of them??.

 

The term of art for proposals like this is "geo-engineering". Proposals come in basically two varieties: ways to suck carbon out of the air, and ways to shade the earth.

As always, in this area, the best place to start is to ping realclimate.org.

RealClimate: Geo-engineering in vogue…

The consensus of well-informed people is, I think, that the approaches based on shading the earth have a lot of drawbacks. Not just cost.

First, they have to keep working a long time. Excess C02 has a long residence time in the atmosphere. Whatever you do to shade the earth, if you do that and continue to emit C02 at the current pace, then you're committed to maintaining that shade for a long, long time -- on the order of centuries.

For geoengineering based on putting aerosols into the upper atmosphere, you clearly have to renew that continuously, as those particles fall out of the atmosphere.

For space-based mirrors, people forget that orbits decay, and the lighter (less dense) the item in the orbit, the more rapid the decay. And, of course, if we continue to emit C02, you have to continue to build up the space-based mirrors.

Bottom line: If you could do it in the first place, you'd better hope that mankind has the wherewithal and will to continue launching replacement mirrors into space for the next few centuries. Because if you allow C02 to continue to build, then take away the sunscreen, you get rapid warming.

Second, a shaded planet with high C02 is not the same as the planet we currently inhabit. Acidification of the ocean will continue, and the climate will be different. For example, in the past, say when Pinatubo erupted, when there was a large aerosol injection into the atmosphere that cooled the planet, it greatly reduced the monsoon. So if you go this route, you (at the minimum) redistribute rainfall away from certain heavily populated areas. It's also not clear that you would avoid thawing the arctic, even if you held global mean temperature the same as now, under a high-C02-but-shadier world.

So you could get the average temperature "right", but the total picture of high-C02-less-sunlight would not look like the earth today. In particular, if you depended on the monsoon, you probably would not favor this approach. If you like to eat shellfish, you probably would not favor this approach.

That said, we may yet get desperate enough to try some geoengineering along those lines.

The alternative form of geoengineering is to try various methods to suck carbon out of the air. For example, most rocks release carbon as they weather, but some absorb it (convert it to carbonate). So you could try mining those rocks, grinding them up, distributing the rock dust, as a way to trap atmospheric carbon. Biochar is another one. I'm sure there are others.

The problem as I see it is the scale of the enterprise. Barring some new approach, it's probably cheaper just to not burn the fossil fuel in the first place.

To put it in perspective, the US emits something like 2 gigatons of carbon per year. Per the EPA, an acre of southern pine will absorb about a ton of carbon per year over its lifetime. So, could we plant, harvest, and store enough trees to absorb our carbon emissions? We'd need to plant 2 billion acres (2 giga acres) of new pine forest, if we wanted to suck up all our emitted carbon. Problem is that the land area of the US is only 2.3B acres. Even if we could (e.g.) water the deserts, we literally don't have enough unused land to do it. Although you will see proposals to (e.g.) water Saudi Arabia and the Australian outback and plant forests there. So that we can keep emitting carbon.

So I'm not against geoengineering per se, but you need to put it in perspective. Shading the earth to reduce temperature is not equivalent to stopping the emission of greenhouse gases. It's riskier, it assumes a continued high level of civilization for centuries to come, and it results in a planet that is significantly different from the current earth. Methods to remove carbon from the air face a major barrier in the scale of what is needed. Probably, at this stage, in most cases, it would be cheaper just to conserve fuel than to try most of the carbon-absorption methods.

But I wouldn't rule out either one of them if technology changes or we get desperate enough.