Jonathan Swift once observed ‘How is it possible to expect that Mankind will take Advice, when they will not so much as take Warning.’ It is easy to take the view that it does not matter greatly if people take neither warning nor advice, and continue to work their way through the Earth’s fossil carbon reserves until they can get no more. As the greenhouse gases build up, more energy will be trapped in the atmosphere, making the planet warmer, altering rainfall distribution and increasing sea level. That icon of climate change, the polar bear, will disappear from its natural home, along with other less spectacular creatures. After very many thousands of years, most of the fossil-derived carbon dioxide will end up in the ocean or in marine sediments and the flux of carbon dioxide between air, sea and land will return to balance. In the meanwhile, many of our descendants could find themselves without the necessities for life. It is also possible to imagine a world where we humans stabilize the climate, deliberately reducing the concentration of greenhouse gases in times of global warming, increasing them when the inexorable swing of the Milankovitch Cycles brings us to the start of another ice age.
Global warming is insidious: it is hard to discern slow long-term trends in climate against the daily, seasonal and annual variations that we all know as the weather. It thus differs from the more obvious and immediate threats facing humanity in the twenty-first century - militarism, fanaticism, political and economic instability, corruption and lethal pandemics.
It is impossible to put a precise figure on how much time we have left to put effective controls on greenhouse gases in place. According to the Stern Review ‘there is still time to avoid the worst impacts of climate change if strong collective action starts now’. Further, ‘the next ten to twenty years will be a period of transition, from a world where carbon pricing schemes are in their infancy, to one where carbon pricing is universal and automatically factored into decision making’. But the longer the delay, the more damage will be done and the more it will cost to remedy. Because so much fossil carbon dioxide has already been emitted, some warming is inevitable, whatever is done in the future, and people will have to adapt to this warming (and to the associated rise in sea level) as best they can.
There are no simple ways to deal with the changes in climate that people are bringing upon themselves. Although no one can say how people will deal with the effect of their own activities in the distant future, certain options are already available. People can adapt to climate change, become less wasteful with energy, work out ways to prevent greenhouse gases entering the atmosphere and develop clean sources of energy. There are good precedents: governments have already acted concertedly and successfully to control chemicals that destroy the ozone layer and to reduce the emission of sulfurous gases from industry. As developing countries such as China, India or Brazil industrialize, more fossil fuel will be used – unless they can leapfrog the carbon phase of development and move comprehensively to non-fossil sources of energy. But no developing country is going to agree to remain poor, just to prevent climate change in other parts of the world.
The most urgent technological problems now facing people (see Table 5.1) are to reduce carbon dioxide emissions from electricity generation and heavy industry, to make buildings more energy-efficient and to obtain more kilometres per litre of fuel from transport, particularly cars. The great advantage of fossil fuels is their cheapness and convenience, compared to most alternatives, but fuel costs will rise as demand increases and the more accessible fossil reserves are worked out. This rise in the real cost of fossil fuel, coupled with the dire long-term influence of fossil fuels on climate, will increasingly drive people to investigate and exploit non-fossil sources of energy – assuming that the drive to greener energy is not derailed by accident, obduracy, or vested interests.
Although no legally binding agreements to limit emissions emerged from the 2009 United Nations Climate Change Conference in Copenhagen, the meeting did show that all the major countries now accept that the ever-increasing use of fossil fuels will alter global climate, in most cases for the worse. It would be surprising if universal agreement could be reached at one meeting, seeing the huge differences in development of the different countries involved – and the compexity of their political alliances. But a global problem requires global agreement – at least between the major industrial countries. There is an old Irish saying ‘the windy day is not the day to be mending the thatch’, and there is much to be said for making such agreements before, rather than after the thatch starts to leak.
The choices between the various ways of dealing with climate change will be made through the evolving interplay of political, regional and economic forces, not by the engineers and scientists to whom this article is addressed. But these scientists and engineers have a duty to point out what is happening and what can be done to mitigate the situation. Their advice must be based on a balanced assessment of the evidence and, crucially, indicate the range of uncertainties in their conclusions. They also have a duty to strive towards objectivity, at the same time openly acknowledging funding and other support. The engineers will, as always, have the task of putting ideas into action and dealing with the problems that arise as they go about their work.
Just in case you need to know:-
The symbol M (for mega) means 106; G (for giga) is 109, T (for tera) is 1012, P (for peta) is 1015 and E (for exa) is 1018.
A joule (J) is the SI unit of work, energy and heat. One joule is the work done when a force of one newton moves its point of application 1 m in the direction of the force.
A watt (W) is the SI unit of power. One watt is one joule per second.
Energy is power multiplied by time. Thus one kWh is the amount of energy equivalent to a steady power of 1 kilowatt running for one hour, or 3.6 x 106 J.
An electricity generating plant rated at one GW, running full-time at its rated output, would produce 31.56 PJ in one year, or 8766 million kWh.
To convert Wm-2 to kWhm-2day-1 multiply by 0.024
To convert Wm-2 to MJm-2day-1 multiply by 0.0864
One tonne of carbon dioxide carbon (t CO2-C) is equivalent to 44/12 or 3.67 tonnes of carbon dioxide. Wherever possible, I have avoided giving the mass of CO2, but used the equivalent mass of CO2carbon instead.
One tonne oil equivalent (toe) corresponds to 4.185 x 1010 J or 1.163 x 104 kilowatt-hours. It is a much-used measure of energy, being the amount of energy released when one tonne of crude oil is burned. One barrel of oil contains 42 US gallons or 159.0 litres. There are approximately 7.2 barrels in a tonne of oil. A barrel of crude oil contains approximately 0.118 tonnes of carbon
One ppm by volume of atmospheric carbon dioxide is equivalent to 2.13 Gt C.
Total concentration of greenhouse gases is given as carbon dioxide equivalent, (or CO2e). This is the sum of all the long-lived greenhouse gases, each calculated as its carbon dioxide equivalent from its Global Warming Potential over a 100 year time-frame (see Table 1.1).
D.S. Jenkinson FRS is Lawes Trust Senior Fellow in the Department of Soil Science, Rothamsted Research, Harpenden, AL5 2JQ, England.
[email protected] © D.S. Jenkinson 2010