A body emits thermal radiation at a rate proportional to its surface area and absolute temperature.

If we do anything on the earth to generate heat at a rate greater than the earth emits the heat the earth gets hotter, and so reaches equilibrium emitting more heat at the higher temperature.

The only way to reach this equilibrium without the earth getting hotter is to either increase the surface area of the planet or reduce the amount of heat in the planet.

Since any form of energy that involves stuff up will generate heat we must reduce the heat coming from the other source.

See black body radiation.

Mines the very very black one with a parasol.

I ginet space mirror is just what we need

porfeser wernstrum

get all the earths robots on to an island for a party ?Then get them to exhuast there emissions ?

I have noticed a change in the radical climate change rhetoric of late (or should that be the mainstream rhetoric)?

The basic theme is that ways to do things 'better' are discouraged. This includes such things as biofuels and nuclear energy. In a weird way the ultra climateers and old oil have joined in unholy alliance to squish any system that maintains the same energy consumption but is perceived as 'greener'

Today you can see old oil and climateers singing from the same hymnbook about the evils of biofuel and 'risky' nuclear. Old Oil wants to sell more oil. climateers want to stop any viable alternative that uses a CO2 cycle of any sort.

In the end climateers want to massively reduce energy consumption. This will inevitably require drastic reduction in humans. (Old oil will tend to disagree with this point of view, just not now)

Reading your article, the solar shield's main theme of slowing global warming falls into the category of allowing existing energy use but without reducing energy use. Hence taboo to the climateers.

I recognize the anomaly about the particular climateers being pro biofuel, but put that down to their (typically) confused thinking. It isn't mainstream.

"If we do anything on the earth to generate heat at a rate greater than the earth emits the heat the earth gets hotter, and so reaches equilibrium emitting more heat at the higher temperature."

The heat generated by human activities is irrelevant. 99% (ish) of the the thermal balance consists of solar input and atmospheric re-emission of that input. Global warming is caused either by our changing the atmospheric composition so as to retain more heat or by an increase in solar input or it doesn't happen at all.

Still, the figure of several trillion dollars is a useful upper limit on the amount of money we should be willing spend on other "solutions".

Since even mentioning those three options probably means the rest of this thread will be a long and boring rehash of the usual argument, I'll just mention Hitler (Godwin's Law) and get my coat. Mine's the big shiny one.

So compared to an unworkable, unachievable, and ridiculously impractical idea their ideas are better? Yup, won me over.

Miss H for her intellectual superiority.

Yes perhaps we should wait for climate models that actually work first (Chaos theory anyone)

Do people actually get paid to work on this pointless crap ?

Since there have yet to be any major civilisation destroying problems associated with global warming I'd rather just wait and see. Who knows what problems might be caused by a space sunshade. Just leave well enough alone and do what we've always done ADAPT.

Generate shed loads of heat, seen all that steam?

Humans, constantly operating at 37 degrees, there's 6 billion of those!

Anything dug up and burnt makes the planet hotter.

@Ken Hagan

I disagree with your figures, but 1% Is still a difference and so the temperature will change.

As I recall, part of the war on the machine was to darken the sky.... Step 1 to the rise of the machine and us stuck in the 80's!

KC

A space sun shield is a stupid way of cooling the Earth. It would be far far cheaper to just paint a large section of the planet white.

Could "they" - (who are they? the wizards?) place solar panels on this oversized parasol, and solve lots of energy problems at the same time?

Paris knows it makes sense.

Seriously, who gets paid to recommend a giant sun-shade? Here is their brilliant idea: humans have broken the weather, so lets fix it by braking the weather. I think Paris has more sense these people, and you can throw a brick at her and she wouldn't notice. I guess I am in the wrong profession. "Humans have damaged the weather, never you mind I have no credentials at all in weather. Now pay me lots of money." That is what I'm going to do so I can be rich, just like these idiot climate change doomsday preachers from the Church of Al Gore.

So rather than just a parasol, why not cover it in solar panels and have a big wire down to earth or some kind of clever Tesla broadcast-electricity doodad to get the energy down here. Lots of renewable electricity, less warming of the climate; a plan with no drawbacks.

... welcome our new space-faring umbrella overlord.

The solar power so derived would be beamed back to earth where it would do hot things and so make the planet hot again.

What's 'ironing'?

Finally, a carbon-emission related excuse for the state of my shirts.

"A space sun shield is a stupid way of cooling the Earth. It would be far far cheaper to just paint a large section of the planet white."

No, you'd want the Earth to be white during the day (to reflect incoming radiation) and black at night (to radiate heat into space). And/or you want cloud cover during the day, but not at night.

Additionally, we want the energy from the Sun but not the heat. If the sunshade was constructed as a giant solar collector and beamed the energy back to earth using frikkin laser beams, we'd solve both global warming and energy supply at once. The "sunshade deathstar" could double as a great "defensive" tool against the rebel alliance (sorry, Axis of Evil).

John

"A space sun shield is a stupid way of cooling the Earth. It would be far far cheaper to just paint a large section of the planet white."

They called this the ice age.

I don't want a big sunshade - it's bloody cold enough here, already.

"The solar power so derived would be beamed back to earth where it would do hot things and so make the planet hot again."

The reduction in fossil fuels would mean lowering the carbon impact while neatly sidestepping nuclear waste.

However it is costly to put solar panels up there and cheaper to put them down here, perhaps cover an unused desert or two, which would then have the same carbon reduction effect.

Why reduce carbon though?

If you've got a giant space parasol do you care any more?

It's the heat we're creating that makes things hot.

Where they set up 'the shield' which turns out to cause more problems than it solves.

Yes, we do care – resources are finite.

"If the sunshade was constructed as a giant solar collector and beamed the energy back to earth using frikkin laser beams, we'd solve both global warming and energy supply at once. The "sunshade deathstar" could double as a great "defensive" tool against the rebel alliance (sorry, Axis of Evil)."

Oh no, we need the full Dyson sphere around the sun to get a sunny deathstar ray!

Mine's the one with the XKCD strip.

Somewhere, Achimedes Plutonium is in a corner crying.

I thought I read some time ago about some ultra-thin Mylar self-unfurling technology that could potentially be used to advertise from orbit. Mylar reflects light damned well, seems like we could just stick one or three of these in a decent orbit for much less than trillions of dollars. Plus how did these people calculate the effects of a sun shade? It doesn't have to cover a given spot on the planet, or be stationary relative to the sun. Seems to me like a rather straight forward way to cool the planet off.

That is assuming that there actually is any global warming, and that if there is we should do anything about it at all. Anything we orbit to block sun will have to be removable in case it gets too cold out there.

And yes, beaming down power would be a bad thing. Everyone talks about heat, thinking that lasers or electricity aren't related to heat. We need to worry about the total energy balance, not just thermal energy, since eventually that laser power will get run through someone's ice box and thus be converted to heat. The whole idea of a sun shade is to prevent energy from getting to the atmosphere at all.

And we should never get an accurate climate model, since that Chaos theory someone mentioned basically says that there is a limit to the ability to predict anything in a chaotic system, even if you know the governing equations really well. Which we probably never will.

Newtons laws of mass and inertia rule absolutely !

"I disagree with your figures, but 1% Is still a difference and so the temperature will change."

Sorry, I was being lazy and said 99% when I couldn't be bothered to go and look it up. I just meant nearly all. In fact, the real figure is more like 99.999999%. For an overview, try...

http://earthobservatory.nasa.gov/Newsroom/MediaResources/Energy_Balance.pdf

A solar shade is going to be dificult, not so much to construct as to keep in correct position and orientation.

How about we just move the earth a bit further from the sun?

(Paris is unhappy because she won't get a tan anymore)

Anyone remember Venus? That planet with runaway greenhouse effect that leaves it boiling day and night, even though the night is 2000 hours long?

Thanks to the thick clouds, the surface of Venus actually receives the ~same~ amount of sunlight as we do right here on Earth, even though it's so much closer to the sun. It's already got a sun shade. But it doesn't help.

That's the whole idea of the greenhouse effect. The planet retains any heat it receives, even if there's less coming in.

Didn't someone already try this?

It would be cheaper to trigger a big volcanic eruption every few years, maybe with some help from a nuclear bomb. It's always fun to make things go boom.

Then we'd have lots of sulphate particles high in the atmosphere reflecting sunlight and cooling the planet. As a bonus, we'd have great sunsets to watch as we relaxed with our drinks.

Yep, this is the common refrain of the green movement.

They refuse to present reasonable soloutions, only problems with a straight-line "don't" which is little more than moralistic preaching.

Olivine dispersal is much easier, and is a BTRO solution. Blocking sunlight is SACTCAR.

--- G.R.L. Cowan, H2 energy fan 'til ~1996

http://www.eagle.ca/~gcowan/boron_blast.html

Nooooooooo! Then you'd be getting clean power, significantly reducing carbon emissions, *and* a sunshade, pleasing nobody but the manufacturers of electric patio heaters and polar bears looking to move to Brighton.

Remember that you can't please all the ecologists all of the time.

Now I've no idea whether I want my coat or not.

Sunshields in space, painting all roofs white and using lighter coloured road surfacing would all help lower the global temperature but they do absolutely nothing to reduce the increasing acidification of the oceans by CO2. That is already killing off corals all over the planet and negatively affecting many species of small marine plankton, etc. that form the basis of the ocean food chain (and thus the basis of much of the human food chain too).

A world that's cool(er) but unable to produce sufficient food to sustain the human and animal population is just as doomed as one that's too hot. There is simply no alternative to reducing CO2 emissions if we are to survive as a relatively prosperous civilised species on this planet.

Don't you understand English, David?

I agree about the sunshade, but, while people bang on about greenhouse effect on Venus, they seem to have no idea that radiation follows the inverse square law and Venus is nearer enough to the sun to get it's heat without any greenhouse effect.

Dave