Friday, 3 April 2009

Global Warming and SF

Global warming is an issue which is not going to go away, and that has implications for anyone writing fiction set in the foreseeable future. Any SF novel set within the next century or few which ignores this issue and its probable consequences will be likely to have a very short shelf-life before being seen as increasingly irrelevant. That doesn't mean that every such story should be about global warming, but that it should be set against a background which includes it – or the measures which were used to overcome it.

I don't, in this brief blog, want to rehearse the well-known basic arguments around global warming. Anyone who isn't yet convinced that this is happening as a result of human activities can read a wide variety of authoritative material on the web, such as the report of the US National Academies: Understanding and Responding to Climate Change; the Royal Society's Facts & Fictions about Climate Change; or, if you want the official 2007 report of the International Panel on Climate Change (the largest and most authoritative body studying this subject) go to the IPCC website. A more user-friendly summary can be found on Wikipedia, while I particularly recommend the New Scientist magazine's Climate Change: a guide for the Perplexed, since that also discusses the usual objections raised.

Instead, I want to focus on what might happen, and (in a later post) what might be done about it – subjects which provide very wide scope for science-fictional speculation. A recent conference of climate scientists in Copenhagen attracted some 2,500 delegates and heard 600 presentations over the three days. In the words of the New Scientist, "the majority [of these] showed the impacts of climate change would happen faster and be worse than previously thought". In other words, the predictions of the 2007 IPCC report are already being overtaken by events. This has been dramatically illustrated by the rapid shrinkage in summer Arctic ice cover.

This should be no great surprise. The rapid industrialisation of China (with a new coal-fired power station reportedly being built every week over the past few years) combined with the fact that very few countries have slowed down the increase in their CO2 output, was until recently boosting the rate of increase in atmospheric CO2 levels over that predicted by the IPCC. For all of its other unhappy consequences, the current economic recession should at least slow down the rate of change and provide a bit of a breathing space to get our environmental act together.

Despite this general view that conditions are changing quickly and that this will result in serious consequences for the global environment and for humanity, there is still much uncertainty over what precisely is going to happen. This is partly because no-one is certain of the exact link between the rate of increase in CO2 production and the rate and ultimate level of the global temperature increase; and similarly no-one knows the exact implications, for climate patterns across the world, of any specific increase in average temperature. This leaves scope for some imagination on the part of SF writers.

Perhaps the greatest uncertainty – and cause for worry – is over the issues of feedback and tipping points. Feedback concerns the threat that some consequences of increased temperature will themselves increase the rate of increase. One obvious example concerns the accelerating shrinkage in polar sea ice. The ice reflects 90 percent of the sun's rays and thus keeps temperatures down. As this disappears, more of the sea is exposed and this absorbs over 90 percent of the solar heat, which helps to explain why the Arctic is warming up faster than the rest of the world. Another example is the existence of large quantities of frozen methane in the ground within arctic regions. As the ground warms up large quantities are already being released into the atmosphere – and methane is itself a greenhouse gas. This could all result in a tipping point, when the self-reinforcing changes gather such momentum that they rapidly accelerate beyond recovery. Nothing like as rapidly as shown in the ludicrous film The Day After Tomorrow, in which temperatures plummet drastically in a matter of minutes, but significant change could happen over a period of decades rather than centuries.

The expected consequences of climate change can be grouped under several broad headings: weather fluctuations; temperature and rainfall patterns; sea level changes; and ocean acidification.

The weather fluctuations we can already see happening are the result of increased atmospheric instability as the temperature rises. That means we are likely to see more, and more violent, storms. It also means that we are likely to see annual temperature and rainfall records continuing to be broken (in both directions). This is, however, by far the least serious of the likely consequences.

Changes in regional temperature and rainfall patterns, and their consequences for agriculture, will be far more significant. These are extremely complex and cannot be predicted with any great confidence, but some general trends are becoming evident. One is that some currently fertile areas, mainly in continental interiors, will become a lot drier. We are already seeing a pattern of increased droughts, in Africa, Australia, China and the USA, where water sources are being used up faster than they are being replenished. This is likely to have a significant effect on agricultural production, since this is one of the major users of fresh water. In part compensation, certain other regions of the world which are now too cold for agriculture will become available. However, it takes a very long time to develop fertile soils suitable for agriculture, and the total area of agricultural land is likely to diminish significantly. Meanwhile, it is virtually certain (for demographic structural reasons – lots of young people in many parts of the world) that barring devastating epidemics, warfare or famine, the world's population will continue to rise until the middle of this century, up from the current 6.4 billion to around 9 billion, with obvious implications for the demand for food and living space – and CO2 production.

It has been suggested that some areas may paradoxically become cooler, at least for a while before the general increase in temperatures pulls them back up again. The best-known possible cause is the stopping of the Gulf Stream (also known as the North Atlantic Drift or the North Atlantic Current, which is part of the Atlantic meridional overturning circulation - AMOC) as a result of a surge of fresh water from melting polar ice. This currently keeps North-West Europe (including the UK) several degrees warmer than it would otherwise be, so the short-term impact of stopping it could be considerable. This was the trigger used for the sudden cooling so exaggerated in The Day after Tomorrow. Some studies have shown that the volume of flow of the Gulf Stream has already reduced by about 30% between 1957 and 2004, but the current view appears to be that a complete stoppage of the Gulf Stream is a less serious risk than previously thought.

The melting of ice brings me on to the third major concern, which is the changes in sea level. These are already happening, partly because the oceanic water expands as it warms up, but that effect is relatively small. It is also worth pointing out that the melting of ice already floating on the ocean (such as the Arctic Ocean ice cap centred on the North Pole, or floating ice sheets around Antarctica) has no direct effect on sea levels because the ice is already displacing water. The threat comes from the melting of ice which is currently on land. Some 90% of such ice covers Antarctica, another 9% is on Greenland, and the remaining 1% is in the form of glaciers and smaller ice caps scattered around the world.

To give an idea of the potential scale of the problem: if the West Antarctic Ice Shelf – WAIS – were to melt or slide into the ocean, global sea levels would rise by an average of about 5 metres. The disappearance of the Greenland ice would add 7 metres. If all ice went, the total rise in sea level would be around 70 metres (220-240 feet) but we don't need to worry about that – according to our current understanding, it would take many millennia, and in such extreme circumstances it is unlikely that humanity would be around to see it. For a more realistic threat, it is worth bearing in mind that sea levels were 3-6 metres higher during the last interglacial period although the global mean temperature was then only 1-2 degrees warmer than now. Current expectations are for an increase in temperature of at least 2 degrees by the end of this century, and it could be a couple of degrees more.

The conventional models of ice melting show that even the WAIS and Greenland ice would take millennia to melt. However, that assumes the ice would melt while still on land; a very slow process. It is now recognised that this isn't necessary, all it has to do is transfer to the ocean to provide the rise in sea level. There are signs that this is already happening, with the rate of movement of many glaciers showing a marked increase as they are lubricated by meltwater flowing underneath them. This could result in a much faster rate of increase of sea level, with an average rise of more than one metre by 2100 now being projected (about double that forecast in the IPCC report). Such a rise would have all sorts of unwelcome consequences for port cities and low-lying areas in which large numbers of people live and farm. There is, of course, a considerable lag between an increase in atmospheric temperatures and the melting of massively thick ice caps. What that means is that even if the average rise in temperature is held to just 2 degrees, the ice will continue to melt, and the sea level to rise, for centuries.

The most recent concern is ocean acidification, which is already happening. As temperatures increase, and the percentage of CO2 in the atmosphere continues to rise, more CO2 is absorbed by the ocean. This causes an increase in the acidity of the water, which potentially will have a serious effect on oceanic ecology as some creatures at the bottom of the food chain may find it impossible to cope. Coupled with world-wide over-fishing, this could result in fish disappearing from the human diet.

In conclusion: as the science firms up, the news concerning climate change keeps on getting worse in almost every respect. However, all is not (necessarily) lost. I will consider what might be done about this, which includes lots of SFnal ideas, in a future post.

1 comment:

WCG said...

Great post, Tony. I will anxiously await your followup, where you explain how we can fix all this! :)