Because of actions already taken, processes set into motion long ago, and ongoing human activities, the planet is deeply committed to a global climate disaster. The disturbing combination of accelerating deforestation, large scale farming, industrial pollution, paving, energy consumption, and most importantly, green house gasses, has resulted in the deadly mix of heat production, heat absorption, and heat trapping. We are just now beginning to feel the effects of this rapidly accelerating catalytic chain reaction of global proportions and unimaginable scale and momentum. It isn't our actions that fuel the impending catastrophe, our ability to create and wield energy is still childlike and insignificant. But we have succeeded in setting into motion trigger processes that profoundly effect how much of the Sun's almost unimaginable power are released upon our little planet, and its finely balanced systems.
Taken together, these three factors have already put the planet into a climate tailspin that is responsible for ice shelf melting, dramatic sea level rise, depletion of fresh water sources, catastrophic weather pattern disruption, ecosystem migrations faster than biology can adjust, catastrophic species and bio-diversity die-offs, ocean PH and serenity shock, large scale shifts in oceanic and atmospheric circulation patterns, rapidly receding glaciers, permafrost thaws re-releasing millions of years accumulated and sequestered carbon and the much harsher green house gas methane, crop depletion, epidemic increases in forest fires, bio-stress induced pestilence and disease, and and potentially, massive and sudden release of biosphere killing methane frozen at the bottoms of our oceans. Absent from this list are all of the sundry ways these changes in the biosphere are and will effect humans.
Because humans often live and sustain themselves where rivers meet oceans, or on the flat inland alluvial valleys along rivers and delta, rising sea levels are already effecting us. If the seas rise as fast as projected (accelerated ice sheet melting is pushing projections to up to 20 meters within the next 20 to 100 years) 10 to 30% of all current human habitation will be below sea level. Almost half as much (some 40%) of our agricultural land will underwater as well (saltwater!).
And these changes are not increasing at friendly rates. Geometric (the current rate times some number x) and exponential (the current rate multiplied by itself some x number of times) math rules the growth rates of this uniquely human caused catastrophy.
The Earth is a huge system. The energy systems effected, the weather and ocean currents, the mix of ice, ocean and land, are colossal. Colossal systems are hard to set moving... and once you do, hard to stop. Momentum on Earth-scales is hard to underestimate. Any changes we can measure today were set into motion long before. Any heroics we absolutely need to engage have to be done now if we expect to see their effect on this accelerating runaway train that is even now careening faster and faster down the mountain that is the Earth's future.
When changes are set into motion at rates that outpace the capacity of biology to react, biology simply can not survive. This is the situation we have entered. While the world warms, micro climates all around the world are moving steadily towards the poles. Deserts are spreading out and away from the equators. Temperate climates are being pushed towards the poles. On mountain slopes, banded climates are being pushed ever upward towards higher and higher elevations. If this drift is more than a few miles a decade, plants which move in their glacially slow seed/sprout/mature/seed, centuries long crawl are not fast enough to keep up with the environment that determines their survival. If the plants can't move with the climate, the insects and animals that can move die without them. Evolution, the process that works so well in the long haul, is simply not equipped to work at the rates dictated by the changes human culture have wrought.
Clearly we have to do something and do something fast. Clearly we have to choose solutions that effect the system at scales fit to the scale of the problem and at rates that are matched as well. If the runaway train is going 100 miles per hour and weighs 1000 tones, and we try to slow it down by towing it in the opposite direction by a truck that can only tow 1 tone at 50 mph, than we are not going to do anything much at all to solve the problem. Anyone who knows physics will tell you that a 1 ton force will eventually stop any coasting train no matter how big or fast... unless that train is being accelerated by an opposing force. The global warming train is being pushed... it is of course subject to huge force, the sun. Which is to say that it isn't just coasting... it is accelerating. Which simply and absolutely means that we will only slow it down if the force we apply to stop it is smaller than the force that is already propelling it towards oblivion. Any realistic solution will have to effect changes at a larger scale and at a faster rate than those that are causing the problem in the first place. This is important. This is, in point of fact, the only important criteria of a true solution. Anything less will not and can not work.
So what exactly is pushing our runaway climate? The sun! No, the sun isn't getting hotter or closer, its just that too much of its energy is staying here to warm things up. Why? Mainly because some of the gasses that our machines emit float up to the highest layers of our atmosphere and act as one-way mirrors; letting the sun's photons in, and then trapping many of the ones that used to hit the land and oceans and bounce back into space. Because the sun hasn't changed, we humans must therefor shoulder the entire blame. Likewise, and ironically, we are the only things around that are fast and smart enough to effect a solution.
Again, our in-system solar budget is growing... and if things stay the way they are, there is nothing for the earth to do but get hotter and hotter until we can remove some of the greenhouse gasses that have already floated up there. Confounding the problem is the fact that the greenhouse gasses are long lived and stable. Once they find their way up there... well, they stay there for centruries. Our two other options are not so straight forward but may end up providing paths towards workable solutions. The first option is to restrict the amount of the sun's energy that reach the earth. The second option is to devise an active heat pump that sends excess heat up, out and away from the earth (and its atmosphere).
Green house gasses act as a switch that controls how much of the sun's overwhelming energy enters and remains within the earth's heat system. Yes it is true, we humans are producing more heat than was here without us. Every time we drive to the store or cook on our stoves or burn coal or gas to generate electricity, every time we push a river through a turbine or run a factory we are converting potential energy to free energy or degrading free energy down towards heat, adding to the heat on earth. But when compared to the heat trapped by greenhouse gasses, human produced heat still only accounts for about one ten thousandths of the energy contributing to global warming. Because human thirst for energy doubles every two decades, it won't be long before this ratio is flipped. For the next half century or so, we can ignore this factor and concentrate only on solar energy trapped by green house gases. Its not what we are doing down down here as much as it is how what we are doing down here effects the Earth's natural solar energy regulators. Even the smallest changes the reflective index of our upper atmosphere have large effects on the amount of energy (heat) trapped within Earth's system.
Scientists and activists have long used the "driving a car" metaphor to illustrate our shared predicament... warning that we are going to have to take some pressure off of the gas peddle... that we need to do what it takes to slow our production of carbon dioxide. But this is misleading. A car slows down when one releases the accelerator. Global warming does not slow when we decrease the amount of carbon dioxide and methane we are exhausting into our atmosphere. The stuff that is already up there just stays up there and continues to act as a greenhouse roof, trapping the sun's energy for hundreds of years. The sun keeps burning... so the Earth will keep getting hotter. Even if we completely stopped using hydrocarbons today, the amount of greenhouse gasses already up there will continue to trap more of the sun's heat than the earth can re-radiat into space... so the earth just continues to get hotter indefinitely.
You can use the car metaphor if you would like, but it is distance that matters, not speed. Imagine the road as a thermostat. Where you start is the Earth's natural self-regulating sweet spot, where there is just enough carbon dioxide and methane in the stratosphere to maintain a constant average global temperature. Every time you drive the car you are moving further from this neutral point... you are adding more greenhouse gasses to the naturally balanced level. You can stop the car at any point, but the damage is already done. Just sitting there with the engine off won't do anything to slow down the warming you have already started in motion. That sun keeps shining, isn't effected at all by your driving, but your driving has opened the earth's spigot a little bit more, so more of the sun's energy is flooding in. Driving with a lighter foot simply slows the "rate" at which we are opening up the already overly open spigot to the sun's relentless energy.
Which isn't to say that we shouldn't attempt always to find ways to reduce the tonnage of CO2 we are releasing. That is essential. Slowing this car down won't be easy. But if we are serious about recognizing global warming, we are going to have to do something to reduce the amount of solar energy that gets here or something that offloads the heat already here. We are going to have to put this car in reverse and back it up to, and then past, that neutral starting point we disturbed when we first started burning all of these hydrocarbons for a living.
Backing up...that is what this paper is about. Backing up means bringing the Earth's budget of the sun's energy back to its pre-industrial balance... and at least until things get back on track, even over-compensating for warming already in process.
What of smoke and smog, don't these help shade the earth from the sun's energy? While it is true that dust and soot act to shade areas beneath them, they also absorb the sun's energy and end up trapping more heat. Soot causes local cooling to the air and ground beneath it, but on the scale of the entire atmosphere, soot actually increases the earth's total heat budget. Understanding this fact will help us move towards a real solution. The difference between a solution that works and one that doesn't is the difference between a solution that stops energy from getting here in the first place or ships existing energy up and out into space, and a solution that just redistributes the energy that is already here.
Talk to any rocket scientist and they will tell you that the single greatest problem to be overcome in the design of a space craft or satellite is getting rid of heat. It is easy to make heat, every action, every little process on a spacecraft generates some heat. The laws of thermodynamics guarantee it. Where there is action or change, heat is the eventual a byproduct.
Heat is the bottom of the energetic scale. Anytime a system changes, anytime an action occurs, some of the energy in that system degrades to a lower form. Eventually, that means there will be more heat. And classical heat, molecules jumping around, isn't the kind of heat that can be radiated into space. Simple heat doesn't precipitate photons which can exit into the vacuum of space. Once energy has degraded to chemical heat, extra effort and energy has to be added to the system in order to upgrade it to radiate-able heat.
Space is a vacuum: heat doesn't travel through a vacuum. That is why a thermos bottle works. Surrounding the bottle is a sealed double walled space pumped free of air. Because heat is the jiggling of molecules, without molecules, no heat can be transfered. And guess what... the Earth is ultimately nothing but a space craft in the thermos that is space. Energy gets here easily (the sun), and has a heck of a time leaving. The astute among you will ask, "If heat doesn't travel through a vacuum, than how does the sun's heat get here?" Good question. The answer is that we don't get the sun's heat, but we do get energy that will travel through a vacuum; light! Once it is here, the photons of the sun's light are absorbed by air, land and water, some of these photons bounce right back out into space but most of the energy of most of the photons is transfered to the motion of molecules.. heat. Once it is heat, the sun's energy can't get back out unless some process (a fire, a laser, a charged plasma, radio, nuclear fusion, etc.) converts it back to photons that can travel through space.
Those are the details, the big picture is that human activity has increased the amount of photon trapping gasses in the upper atmosphere and this has tipped the balance towards warming. The gasses are additive and stable... once they are there, they stay there. There are already too many greenhouse gasses. Which means the earth will continue to warm even if we stop putting more up there. That's bad enough. But we aren't stopping. The rate at which we shove more gases up there is increasing geometrically!
Each and every one of the solutions proffered so far by ecologists, politicians, energy experts, etc. have fallen into the 1 ton truck category. They are simply too little and too late. It doesn't matter if these solutions are well intended, if they don't effect reality at the required scale, they simply will not succeed.
If we are to survive, we must immediately do one of two things. We must either reduce the amount of sunlight reaching the earth, or we must actively pump energy off system (up and out into space). Of course it is essential that we get better about how much greenhouse gasses we release into the atmosphere, but because we are already past the tipping point, we need a solution that will counter the damage we have already caused to the natural heat balance.
With computer models we are getting better and better at understanding exactly how much solar energy is now being trapped; how much we would have to dump into space or block before it gets here. We have to take this measurement and build active solutions that bring our energy budget back into balance. Remember, the essential ingredient here is scale. The solution must equal or exceed the scale of the problem and it must effect change in the time frame dictated by the brittleness of the biosphere's own ability to adjust... evolution.
By these criteria I can only conclude that our only reasonable path out of this catastrophic bottleneck is to construct solar shades in earth orbit. We have to stop the sun's energy before it gets here... before it gets in-system. We already have some experience with some of the technologies involved... we have deployed solar sails (thin mirrored mylar film spread out into a disc in space) and could easily build actuators that allow us to control their orientation. If we had enough of them up there, we could effect the solar budget in a controlled manor (reflecting .1 to 3 percent of the rays that would otherwise hit the earth), and could tilt some or all of them like a window shutter to achieve the kind of fine control to make it safe. On earth, nobody would be the wiser... you really couldn't hardly see the things... just little dots up near the mid day sun. This is a passive system well within the our current technical and financial wherewithal. And it would buy us the time we need to figure out how to stop doing things that put CO2 and Methane where it can do damage.
There are other potential solutions of course. But none of them seem physically possible or affordable or controllable. Here are a few alternative solutions along with simple explanations of why they won't work.
1. We could remove some of the carbon dioxide and methane and ozone from it's upper atmospheric perch. In the bathtub example above, this would be equivalent to opening the drain and letting all or some the water out. But how? A hundred years ago there was about 1/3rd less CO2 up there. So it is obvious that some concentration of these greenhouse gasses is essential to the stability of our environment. Any solution that removed all of the green house gasses would plunge the Earth into a sub zero snow ball earth super ice age. Short of nuclear reactions, matter is conserved, you can not "get rid of carbon", the best you can do is grab it and ship it somewhere eles.
2. We could add a whole mess of some sort of reflective dust or crystals to the upper atmosphere... reflecting sunlight back to space. What would this be and how could we control it? How would we get rid of it if it didn't' work, worked too well, or if it did work but our goal had been reached? Any substance we add to the atmosphere will react with other existing substances and degrade into other compounds. Very unpredictable. The 1991 Mount Pinatubo eruption on the Philippine islands, provided direct measurable evidence of one substance that works as an aerosol solar reflector: sulfur dioxide. For ten years after the eruption, predicted global warming was held steady by this upper atmosphere infusion of the distinctly yellow gas. Sulfur dioxide is in no way inert, it is the nasty pollutant that causes "acid rain". But in times of great danger, one has often to make terrible decisions. By the way, we would have to dig up (and somehow burn and eject to at least 80 thousand feet) more of this rotten-egg smelling stuff than the all of coal we currently mine world wide. The Pinatubo explosion sent 1 cubic mile of material to an altitude of 22 miles. To mimic the effect of the Pinatubo event, we would have to somehow harness the energy equivalent to 800 1 megaton (Hiroshima) nuclear bombs. To put this into perspective, a measly 1 megaton nuclear bomb releases the equivalent energy of 11 billion kilowatt hours of electricity. Which means we would somehow have to gather together energy equivalent to at least eight thousand eight hundred billion kilowatt hours worth of electricity (and that is just to get the stuff up into the stratosphere). How much energy would it take to mine it and processes it for dispersion? And that is just to counter warming at 1990 greenhouse gas levels (and only for 10 years or so). Any fix that uses a substance as nasty as sulfur dioxide, and in the amounts needed, and at the expense projected, would clearly be the choice of last resort.
3. An adjunct scheme (to adding reflective particles or gas to the stratosphere) is to somehow make the ones already up there more reflective. This could involve the insertion of a smallish amount of some super reactive compound which would catalyze a transformative reaction. Clearly dangerous even if we could find this magic substance. An alternative method I have proposed would be to physically orient (existing) stratospheric crystals (water and methane ice) so that they are more reflective (point their flat sides to the sun). I went to a lecture at NASA AMES in the 80s explaining how plasma and earth's magnetic fields do this naturally. The bugaboo here is beaming energy up to the crystals (masers? microwaves?) that would hold the buggers in the desired orientation. Also, I have not done enough research to know if there are enough of the little buggers up there, the calculations to know if orienting them would reflect enough sunlight to make a difference, or how much energy it would take to spin and hold them perpendicular to the sun.
4. Proposals have been put forth to make more reflective some significant percentage of the Earth's surface. It is estimated that greenhouse gas warming could be countered by somehow painting white an area the size of all earth desserts. Solutions that increase reflectivity at the surface are far less efficient as much of the reflected energy is absorbed by the atmosphere on the way back out to space. There are about 10 million square miles of dessert. At 80,000 gallons of paint per square mile... it would take eight hundred billion gallons of Sears' Best Outdoor Latex! Plan B at best.
5. We could somehow collect and concentrate in-system heat and then pump it out and into space. Wow, talk about difficult and expensive. The laws of thermodynamics blatantly guarantee the incredible expense of any such mechanism. This would be the classic Maxwell's Daemon problem writ large. More heat would be generated in the process of collecting the heat and moving it off-system than you could ever ship away after you collected it. Even if we could cheat the second law, how would we ship heat off system? Well we would have to upgrade simple molecular heat (giggling molecules) into photonic (radiated) energy (light) and then beam that light (radio, infrared, visible, ultraviolet, microwave, x-ray?) into space (laser, maser?). Much of it would never actually leave as it would heat up the atmosphere on its way out. Beaming energy off system would take huge amounts of energy, and energy is part of our problem... we never seem to have enough especially during this uncomfortable transition away from dwindling fossil fuel sources. In fact, any potential global warming solution that requires a substantial amount of new energy to succeed, simply will not ever succeed... where do we get the energy is the first problem, but the other less obvious problem is that energy use creates heat.
6. We could do something down here on the surface of the earth that sequesters heat... that converts heat from active energy to potential energy. You have no doubt heard the term "carbon sequestering", well there are chemical processes that pull heat out of a system and store it chemically or structurally. These reactions are called endothermic reactions. Carbon sequestering is itself an endothermic process. Rain forests do this. Photosynthesis is the Earth's the biological mechanism for heat sequestering. This is one of the reason's the rain forests are so important to the health of the planet. Our thirst for energy and wealth has put us on a path towards increased destruction of rain forests. Just slowing this destruction has proved culturally and politically daunting. Actively "constructing" rain forests or some other system that approaches the carbon and heat sequestering capacity of these unfathomably complex natural systems is outside of the capacity of human knowledge and human resources.
7. Alternative space reflector plans have been proposed. An early plan proposed a huge glass lens placed at the L1 (Lagrangian) point. The L1 is a balance point between the Earth and the Sun where gravity of the two masses are equivalent (after the orbital momentum of the satellite is factored out). The magic of this point is that it parallels the earth's orbit around the sun. An object placed there would stay put... would always be right between the sun and the earth where it could shade the earth. The proposed lens would refract the light from the sun, spreading it out so that some of it spills out into space and misses the earth. If you have ever seen the flat lenses (on the back windows of vans with the record like concentric grooves) you will know how a much lighter lens could be made of extremely thin plastic film. If this Fresnel lens was spun like a disk, the centrifugal force would hold it into the proper shape. A single such lens about a thousand miles in diameter would divert enough of the sun's rays to right the wrongs of greenhouse gasses. Other proposals involve a cloud of particles or small lenses (instead of one big one). Installing a space lens would require commodity launch economics that we haven't yet achieved. The Earth/Sun L1 point for such an object would be about 6 times the distance between us and the moon. The launch and construction of such a space shade would have to be mostly robotic.
Taken together, our choices are few, daunting, and problematic. Inaction by any projection leads only to disaster. The best we can do is choose the best of the evils and get to work making it work in the timeframe we have. In the long term we have to save our rain forests. We have to stop burning hydro carbons for energy. We have to learn to use our natural energy source, the sun, at the rate it comes to us. We have to understand the Earth's heat regulation mechanisms and work with them to slow human-induced environmental change to a rate that biological evolution can comfortably handle. Right now we have to do something fast and big that will allow us the luxury to solve the larger longer term problems at the pace their complexity demands.
