The threat to humanity is clear: such a disappearance of living space (with some 100 million people living within less than 1 metre above present sea level) would represent a virtually impossible burden to a human population that is already struggling to feed itself, and is set to add another three billions to its numbers this century.
We note that it may not be the amount of sea level rise, as its speed, which may be catastrophic for a large section of humanity. The geological record shows that the melting of icecaps does not proceed smoothly, but occurs in fits and starts. Thus, the last retreat of the great ice-sheets included at least three episodes where sea level rose some 5-10 metres within the space of a decade. This is because a modest sea level rise can destabilize the edge of a mass of land ice, causing large parts of it to rapidly slide into the sea.
The consequences of such a sea level rise would be calamitous, comparable (and perhaps including as a consequence) a global war. Unlike a world war, though, civilization cannot get back to normal afterwards, as much of the landscape will have been drowned, effectively forever. We consider the threat to be imminent, the timescale of the global changes seeming likely to include the lifespans of our children.
The central problem We therefore add our voices to those urging more serious attention, and action, from national and international bodies. The central problem is one of the massive transfer of carbon from beneath the ground into the atmosphere, caused by humanity’s enormous demands for energy, and current dependence on fossil fuels to supply by far the greatest part of this energy.
It is hard to convey the sheer scale of this carbon transfer. In numbers, it currently runs at some 6.5 billion tons each year. How can one visualize this? If the Great Pyramid of Khufu were made of diamond, the densest and most compact form of pure carbon, it would weigh some 6.5 million tons. So, globally, our annual carbon transfer, through fossil fuel burning, to the atmosphere is equivalent to one thousand Great Pyramids, all made of diamond. We burn, each year, around a million years worth of accumulated hydrocarbons.
Action The problem can only be marginally (i.e. ineffectually) addressed by increases in alternative energy and energy efficiency; these should be promoted, but likely savings will be modest, and probably offset by population and economic growth. And, given the huge energy and material demands in the construction of, say, wind farms, the ultimate value of these is debatable. More radical solutions to humanity’s dilemma are necessary, and these might include:
- massive underground sequestration of CO2. This is not yet a proven method on anything like the scale needed, buit needs to be pursued with urgency.large-scale capture of CO2 from the air and its conversion into a mineralized form, perhaps as carbonate minerals.
- a large-scale switch to civil nuclear power. This has the benefit of being proven technology and, additionally, has the potential to lie at the heart of future hydrogen-based transport systems. We are acutely aware of the problems and current public unpopularity of this route, and the knock-on effects for, say, nuclear arms proliferation. Nevertheless, the dangers posed by global warming may be orders of magnitude greater than those resulting from the controlled use of nuclear power.
Sources A good deal has now been written on ways to stem to carbon tide, though rather less has been put into practice. General statements include the remarkable article recently published by David King (chief scientific advisor to the UK government):
- King, D.A. 2004. Climate change science: adapt, mitigate or ignore? Science, vol. 303, pp. 176-177.
There are also:
- Hasselmann, K. et al. 2003.The challenge of long-term climate change. Science, vol. 302, pp. 1921-1923.
- Watson, R.T. 2003. Climate change: The political situation. Science, vol. 302, pp. 1925-1926.
As regards specific technologies, there is:
- Lackner, K.S. 2003. A guide to CO2 sequestration. Science , vol. 300, pp. 1677-1678.
- A series of papers on the hydrogen economy, headed ‘Not So Simple’, in Science, 2004, vol. 305, pp. 957-976.
- Schiermeier, Q. 2003. The oresmen. Nature, vol. 421, pp. 109-110 (on fertilizing the open ocean with iron, to see if enhanced plankton growth can extract CO2 from the atmosphere; recent experiments on this method are detailed in a series of papers in Science, 2004, vol. 304, pp. 396-397 and pp. 408-420).