The simple arguments concerning the connection between rise in world temperature and rise in sea level are inadequate, and so one often has to rely on the complicated world climate models. It is not possible for anyone who is not actually making such calculations to assess the validity or the results and, one may add, not so easy even for those who are. There is the additional uncertainty due to the possibility that the changes in average world climate do not always take place smoothly. This happens when some variable reaches a critical value and a large and irreversible change takes place, as when a kettle boils over or a house of cards collapses. We cannot be absolutely sure what will happen to the climate in the future. Thus it has been suggested that there may be a sudden and catastrophic cooling of northern Europe due to a change in the flow of the Gulf Stream. At present the Gulf Stream brings warm water from the tropics toward Europe by what is called the thermohaline circulation. This is due to the freezing of the Arctic water, which causes the salt water to drain out of the ice. This salty water is heavier than fresh water and so it sinks thus drawing warmer water northwards from the tropics. As this water cools it becomes denser and also sinks, thus attracting more warm water. If the oceans are heated by global warming and more freshwater enters the polar seas it could slow and even stop the Gulf Stream. This could cause the temperature to fall by six to eight degrees centigrade and so it would then be frozen for much of the year, and London would be like Siberia.
Such uncertainties are not uncommon in human affairs. We have to make a decision on the basis of incomplete knowledge. It is easy to say that we must undertake more research and do nothing until we are absolutely sure what is the best thing to do. This is nearly always the worst decision of all. We must take our decision on the basis of the best knowledge we have, even if it is to some extent uncertain. Concerning climate change, the best knowledge we have is contained in the results of the model calculations, and of how the climate has changed in the past from measurements on stratigraphic records from ice, lake, peat bog and marine sediment cores.
It has been estimated by the World Health Organisation that climate change is already causing about 150,000 deaths each year, and this is set to rise in the future. It is therefore prudent to explore any practicable means to reduce the emission of the gases that are responsible.
During the last century carbon emissions have fallen due to the gradual shift from coal to oil, gas and nuclear power, but soon this is likely due to change due to increased coal burning in China and India and reduced use of oil and gas. Governments are increasingly concerned about the effects of climate change, and have convened a series of conferences at Rio (1992), Kyoto (1997) and Johannesburg (2004) to decide the best ways to tackle the problem. At the meeting at Rio the representatives of 165 countries agreed to 'stabilise greenhouse gas emissions at a level that would prevent dangerous anthropogenic interference with the climate system'. As a start, countries were told to reduce their greenhouse gas emission to the 1990 level. By 1995, however, the emissions were still rising. At the meeting in Kyoto, the industrialised countries accepted rather different obligations: the Europeans to 8% below 1990 levels, the USA to 7% below and Japan to 6% below. This applies to five greenhouse gases in addition to carbon dioxide. The emerging industrial countries, including India, China, Sri Lanka, and Kuwait had no obligation to reduce in the period up to 2010. The USA refused to accept these targets unless they were applied to other countries as well. Otherwise, because reductions are expensive, the US companies would be at a disadvantage compared with companies in India and China. This is true, but it seems unjust for nations who have developed their industries without pollution control to prevent developing countries from behaving in the same way. At present the average American is responsible for the same emissions as 18 Indians and 99 Bangladeshi, so why should they have different targets? Despite strong international pressure the USA declined to take action, and its emissions rose by 12% during the 1990s. The British Government agreed to reduce carbon emission by 20% from the 1990 level by 2010, but it is evident that it is nearly impossible to achieve this (Nuclear Issues 28, 2006).
As already mentioned in Section 6.3, the potentially devastating effects of climate change require much larger reductions in carbon dioxide emissions, and it is clear that any realistic proposals, such as much higher taxes on emissions, would meet with implacable opposition. To overcome this is one of the most challenging problems of the present time.
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