This is the third and last part of my tour around the global warming issues and what might be done about them, with a view to how these might feature in SF. Last time I identified four possible courses of action: to cut back CO2 production; to remove CO2 already in the atmosphere; to reduce insolation (heat received from the sun); and finally to adapt to the changes which are now inevitable. I have already dealt with the first one, now for the other three.
Remove CO2 already in the atmosphere
One of the major problems with churning out CO2 is that, once in the atmosphere, it persists for a very long time. This contrasts with other greenhouse gases such as methane, which disappear relatively quickly. Even if it were possible to stop all burning of fossil fuels immediately, the quantity of CO2 already in the atmosphere would remain higher than pre-industrial levels for centuries to come; which means that the Earth will continue warming up for centuries. As a result, there is increasing interest in "geoengineering" – physically removing CO2 from the atmosphere, or finding other ways to increase CO2 absorption or to prevent the greenhouse effect.
Geoengineering is highly controversial because of worries that it may have unwanted consequences; for instance, increasing oceanic absorption of CO2 will increase seawater's acidity (something which is already beginning to happen) with potentially dire consequences for the marine ecosystem. It is therefore only being considered as a last resort, because climate scientists now believe that there is no chance of cutting CO2 production by enough to make much difference; in fact, before the current recession hit, carbon emissions were still increasing by 3% a year.
Geoengineering techniques can be as simple as planting trees, but this only postpones the problem – at some point, the trees will die and their carbon will be released. More drastic measures are therefore being considered. These include seeding the oceans with iron filings to encourage the growth of organisms which would trap CO2. However, apart from the acidification problem, a recent experiment failed to achieve the desired effect.
A more high-tech approach is to manufacture huge quantities of "scrubbers" which will physically remove CO2 from the atmosphere. Three different techniques have been proposed.
One is a "spray hangar" in which air is sucked in one end and blown out of the other after being sprayed with sodium hydroxide solution; this reacts with CO2 to form droplets of sodium carbonate. This is known to work, but in its present form requires a huge amount of energy.
An alternative is the "solar scrubber", using sun-focusing mirrors to heat a transparent tube filled with pellets of calcium oxide. As the temperature rises to 400 degrees C, air is blown through the tube and its CO2 combines with the chemical to form calcium carbonate; virtually all of the CO2 is extracted. The process can be reversed by doubling the temperature in order to drive off pure CO2 which can easily be captured; but of course, a safe way of disposing of it then has to be found. One possibility is to pump it into adjacent greenhouses in order to promote crop growth (a technique which is already being used).
The third option is the "air collector", which pumps air over an ion exchange resin, a polymer impregnated with sodium hydroxide, to which the CO2 adheres. It can later be washed out for disposal using humid air at only 40 degree C.
The benefit of these technologies is that there appears to be minimal risk of unintended consequences since all they do is extract CO2, a process which can instantly be switched off when no longer needed. The main drawback of the CO2 scrubbers is that millions of the things would be needed, at huge cost.
A different approach is to reduce the degree by which the sun heats up the Earth, by reflecting more of its rays back into space. As we have seen, ice fields reflect around 90% of the insolation (compared with 94% absorption in open water) and their melting is contributing to Arctic warming. One study calculated that reflecting an extra 1.8% of insolation would cancel out the effects of doubling the CO2 levels.
Various fanciful ideas have been proposed, such as dumping vast quantities of white polystyrene to float in the oceans (which could of course reduce their capacity to absorb CO2) or pumping sulphate particles high into the atmosphere to reflect the sun's rays (but this could cause catastrophic droughts in some regions, and would need constant renewal). A variation on the last one is to pump atomised seawater into stratocumulus clouds in order to increase their density and make them more reflective. This should work, but the processes of atomisation and of getting the water up to the clouds in such enormous quantities are obviously not trivial issues.
A more high-tech approach is to launch "sunshades" into space, in the form of discs of silicon about 60 cm across., just a few micrometers thick and weighting 1 gram. Each would be covered with holes calculated to act like a lens, causing dispersion and dimming of the sunlight. They would be "steerable" using solar energy to keep them in the correct position and orientation. The proposal involves launching containers, each carrying a million discs, from huge electromagnetic rail guns, towards the L1 Lagrange point where the Earth's and the sun's gravities cancel out. It has been estimated that twenty rail guns, each 3 km high and working around the clock to launch one container every five minutes for ten years, could achieve the 1.8% reduction, and it is hoped that the discs could last for up to 50 years.
The danger with all of these techniques would be if they were relied on to cancel out the effect of rising CO2 levels, thereby allowing CO2 to build up to high levels. Should the regular renewal of the sunshades then fail for any reason, the consequences to the climate of being suddenly exposed to high levels of atmospheric CO2 could be sudden and catastrophic.
A lower-tech approach would be to install reflective surfaces on the roofs of buildings or in the form of material covering desert areas, in those locations not required for solar heating or power systems.
Adapt to the changes
It is now accepted by climate scientists that any effective moves to reduce CO2 production will now be too late to avoid some unpleasant consequences – our politicians have already failed us by avoiding the potentially unpopular measures required. Even the 2007 IPCC report predicted a rise in global average temperature of between 2 and 6.4 degrees C this century and, as we have seen, a recent conference of climate scientists concluded that the outlook has worsened since that was written. An increase of 4 degrees by the end of the century now looks quite possible on present trends. So as well as continuing to try to minimise the warming effect, we are going to have to prepare for the consequences of a warmer world.
What this might mean is discussed in an article published in New Scientist on 28 February 2009 ("Surviving in a Warmer World"), which spells out the implications of a 4 degree warmer world. The picture painted is frankly horrifying. Much of the tropics would become uninhabitable due to drought, floods or extreme weather; the Amazon basin would become a desert, as would most of the USA, southern Europe, nearly all of Africa, southern Asia and Australia. Rising sea levels would mean that low-lying areas would vanish. On the bright side, there would be some potential for reforestation due to changing wind patterns, in west Africa and western Australia. However, the main areas suitable for habitation and farming would be Canada and Alaska, northern Europe and Asia, New Zealand, western Greenland and western Antarctica. These would become exceedingly crowded places, with the surviving population having to live in dense, high-rise accommodation to leave as much usable land as possible free for agriculture.
James Lovelock, who developed the "Gaia" theory, estimates that the devastation caused by climate change could result in the world's population reducing to 1 billion or less by the end of this century. Inevitably, there would be huge conflicts as displaced populations attempted to move to more favoured areas. Many observers think that the first climate change war has been underway for years, in the civil war in the Sudan. Christians and Muslims had lived peacefully side-by side in Sudan's Darfur province for centuries, but the trigger for their vicious war (in which 200,000 have already died and around two million been displaced) has been a dramatic reduction in rainfall over the past few decades, leading to increasing desertification and a conflict over the remaining usable land. If the regional climate projections are right, similar problems are likely to occur throughout the tropics during this century.
Other climate impact specialists consider that the worst consequences can be reduced, provided that we start planning and acting now, by determinedly adopting the kind of measures discussed in this survey. It's too late to prevent a lot of problems, but it's worth doing all we can to minimise the future scale of them, since that could prevent a bad situation from becoming utterly appalling. The political issues and pressures generated by all this are a potential source of material for near-future fiction.
Even if world leaders really begin to address this problem effectively, some changes will have to be made. The rising sea level, combined with more, and more violent, storms means that it would generally be futile to continue defending low-lying coastal areas. To give one well-known example, there is no point in the long term in trying to protect cities like New Orleans. This is already beginning to happen in a small way, with the evacuation of the 1,400 inhabitants of Papua New Guinea's Carteret Islands, and there are similar plans to abandon other low-lying oceanic islands. The prospect of millions of Bangladeshis moving into India as their land floods will raise problems on a very different scale.
Water shortages resulting from a combination of climate change and population growth will also require some changes to farming to get the maximum value out of agricultural land. One consequence is that meat-eating will have to diminish because, for the same food value, animal farms use farmland and water at several times the rate of crop farms. So the only farm animals likely to survive will be those which can live on rough mountain pasture unsuitable for agriculture. To make matters worse, fish stocks will continue to shrink, not just through overfishing but through the increasing acidification and deoxygenation of the oceans. The water shortages will almost certainly end the current squeamishness about genetically-modified crops; to produce enough food, it will be necessary to develop drought-resistant strains.
Even so, a switch to a largely vegetarian diet wouldn't provide a complete solution. Crops not only use up a lot of water, our commercial farms are also heavily dependent on oil, for farm machinery, transport and fertiliser. Reductions in the use of fossil fuels to cut back on CO2 production, combined with an increasing shortage of oil as cheap sources are used up, will make traditional crop-growing far more difficult and expensive. A recent UK TV programme on "farms of the future" predicted the decline of large-scale crop growing in favour of local "vertical farms", based on hedges and trees producing fruit, nuts and edible leaves, which can provide several times the food value of the same area of arable land. These require very little work or other resources to grow, but they are much more labour-intensive to collect.
That just about wraps up my survey. In a nutshell, climate change is accelerating, and if we wish to avoid some rather horrendous consequences, we need to put a far higher priority on taking the kind of preventative and precautionary measures I have been describing. I hope that all of this provides some useful material for the SF community; certainly there is scope for a wide range of backgrounds, from best-case to worst-case. My own novel, which I mentioned last time, was intended to represent a likely future but, in the light of the latest information, is now looking to be at the optimistic end of the spectrum!