Select Committee on Economic Affairs Minutes of Evidence


Memorandum by Professor Sir David King, Chief Scientific Adviser to the UK Government

CURRENT UNDERSTANDING OF CLIMATE CHANGE SCIENCE

INTRODUCTION

  1.  I welcome the Committee's interest in the critical issue of climate change. In my capacity as the Government's Chief Scientific Adviser my own involvement in the subject is well known and has been wide-ranging. This has included:

    —  Presenting climate change science and raising the awareness of climate change amongst the public, industry, Parliament and Governments worldwide.

    —  Focusing on the action required, including: (i)  the energy innovation needed to achieve a radical shift to a low carbon economy, (ii)  the establishment of the UK Energy Research Centre, (iii)  UK participation in the International Thermonuclear Experimental Reactor (fusion) project, and (iv)  steps to improve the energy performance of the built environment.

    —  Focusing on actions required to meet the impacts of global warming: particularly through the Foresight Flood and Coastal Defences Project, set up with the Environment Minister Elliot Morley, as stakeholder Minister.

    —  Providing support to Defra, FCO and No 10 on international action, as well as through the network of international Science and Technology Attaches and the Global Science and Innovation Forum.

  2.  The science of climate change is a mature subject. The French mathematician Fourier in 1827 put forward the greenhouse gas concept: our atmosphere absorbs heat that would otherwise radiate out into space. This manifests itself in two important ways. Firstly the Earth's average surface temperature is kept at about 15ºC by this blanket effect of the atmosphere that surrounds it. Without the greenhouse effect, life on this planet would not exist as we know it, as the average temperature would be -18ºC. Secondly, night-time temperatures would otherwise be much lower than they are without the blanketing effect provided by the greenhouse gases. Fourier's work was followed in 1860 by the discovery by the British scientist Tyndall that the major constituents in our atmosphere, nitrogen and oxygen, do not absorb heat (infrared radiation from the earth), and that the greenhouse effect is due to the minority gases in our atmosphere, especially water vapour, carbon dioxide and methane: the greenhouse gases.

  3.  On this basis the Swedish Nobel prizewinner Arrhenuis did the first global warming calculation in 1896. He said: If the human population should burn so much fossil fuel that the carbon dioxide level in the atmosphere should double, what would the temperature rise be? His calculation yielded an average global increase of 5ºC. This is a very large increase: for example, the difference in temperature between an ice age and a warm period is about 5ºC to 8ºC.

  4.  More recent calculations of the global temperature increase that results from a doubling of carbon dioxide levels yielded a temperature range of 1.5-4.5ºC and research from the Hadley Centre proposed a temperature range for doubled CO2 of 2.4-5.4ºC, but these results, and other recent research, do not rule out the possibility of even greater temperature change, suggesting that the scale of climate change could be quite different from previous assumptions.

  5.  Carbon dioxide levels in the atmosphere, and water isotopes serving as a proxy for global temperatures, are encapsulated in ice layers in the Antarctic and on Greenland. The latest data from ice cores show that over the past 750,000 years the Earth has been through eight cycles of ice ages and warm periods. In each of the ice ages the carbon dioxide levels were at around 210 parts per million in the atmosphere. In each of the warm periods the carbon dioxide levels rose to 260-280 ppm. Temperature changes were 5 to 8ºC. The correlation bears out the greenhouse model described above.

  6.  Carbon dioxide levels in the atmosphere have been accurately recorded at the Mauna Loa Observatory, Hawaii, since 1959. They are now rising at a rate of approximately 2ppm per annum, and are approaching 379ppm, 40 per cent above the pre-industrial levels of our current warm period and also all previous warm periods.

  7.  Global temperatures have increased by 0.6ºC over the past century. This is in broad agreement with the theory of the greenhouse effect, and is what Arrhenius predicted in 1896.

  8.  Some argue that warming is happening, but that it is simply part of a natural cycle. They point to the relative warmth in Europe in the middle ages and the cooler conditions that occurred in the 17th and 18th centuries—the so-called little ice age. There are undoubtedly natural fluctuations but we are now facing a sustained warming trend that can only be explained by the rise of greenhouse gases in the atmosphere. The effect of such warming is seen globally in glaciers, which are in retreat around the globe. Some have been dated back to the last ice age, 12,000 years ago, and are in retreat for the first time in our warm period. The latest supporting data was published from the Chinese Academy of Sciences late last year. A 25 year analysis of the Chinese glaciers, which correspond to 15 per cent of land-based ice on earth, based on more than 30,000 aerial photographs and satellite images, demonstrated the loss of 8,000 km2 of ice cover in this period. They estimated that the Chinese glaciers will have disappeared by the end of the century.

  9.  Impacts of climate change predicted by the modellers are already occurring: the middle Europe summer of 2003; high intensity rainfall, hotter summers, etc. Climatologists are currently focusing their attention on a number of key factors.

 (i)   What are the extreme events that we are vulnerable to as global warming continues?

  These include: a slowing, or even termination, of the thermohaline circulation which maintains northern temperatures about 8ºC higher than they would otherwise be; loss of the Greenland ice sheet, which would produce global sea level rises of about 7 metres over a timescale of a thousand years or more; enhanced retreat of glaciers in some regions; major alterations to the Indian monsoon and desertification of increased areas of the African continent.

 (ii)   Water vapour

  As carbon dioxide levels increases all models show an increase in the temperature of the earth and sea. In turn, this increases the amount of water vapour in the atmosphere, which is a greenhouse gas itself and will further raise the temperature. This is a big positive feedback. However, this water vapour can form clouds, and the clouds can have opposite effects: they can act as a blanket, adding to the greenhouse effect, or they can reflect sunlight back into space—especially high white clouds—and cause cooling. This is very difficult to model.

 (iii)   Loss of forest

  Forests remove carbon dioxide from the atmosphere. Deforestation due to human activity is a well-known problem. But sophisticated models now show that decreased rainfall is likely to accompany global warming in some critical forested areas. These include the Amazonian tropical rainforests. Reduced rainfall could lead to dryer conditions and increased numbers of forest fires. This would increase global warming quite substantially.

 (iv)   Acidification and warming of the oceans

  As the CO2 level in the atmosphere increases, so does it also increase in the oceans, which raises the ocean acidity (ie lowers the pH). Effects on coral reefs and plankton populations have already been noted. The wider impact on marine life and on the food chain, including the human food chain, is an area requiring urgent further study.

 (v)   Global dimming due to aerosols and pollutants

  Careful measurements of solar intensity indicate a reduction in sunlight over the past four decades. This is attributable to pollution generated by advanced societies, sulphurous coal in power stations and cars being the major sources. This cooling effect could have masked the true extent of global warming. The clean up process in power stations, car exhausts and other sectors of industry is reducing the aerosol content of the atmosphere and this could lead to greater levels of global warming than we have anticipated.

THE CLIMATE CHANGE SCEPTICS

  11.  These fall into three quite different groups.

    (i)  Serious scientists who stress the problems of modelling aerosols and cloud cover. They do not reject the greenhouse model, the observed increases in carbon dioxide or the observed increase in global temperature. There are very few in this category. The best known is the American climatologist Richard Lindzen.

    (ii)  A second small group of scientists who appear at every meeting but are not seriously regarded. These include scientists who argue, without any proper evidence, that sea levels are not rising at all or that global warming is due to increased solar activity.

    (iii)  Finally, there is a very vocal group of professional lobbyists. Some have had scientific training, but most have not. They manage to make their voice heard as they are articulate and clearly well-funded. They fall into the same category of lobbyists for the tobacco companies who claim that links between smoking and ill health are still not proven.

  12.  In summary, it is quite clear that the balance of international scientific opinion is overwhelmingly in support of the conclusion that climate change is a real and present danger, requiring urgent and committed action. It nonetheless remains a significant issue, in terms of gaining wider political and public consensus on the need for action, that the arguments put forward by the sceptics gain publicity and influence far beyond that which can be justified by the standing of the individuals concerned, by the validity of their arguments, and by the scientific credibility of the evidence that they are able to put forward.

24 February 2005


 
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