Scientific Evidence

The Climate Change Challenge

The fundamentals of climate change have long been understood because they involve the same basic physics that keeps the earth habitable. Heat-trapping 'greenhouse gases' in the atmosphere (of which the two most important are water vapour - clouds- and carbon dioxide, CO₂) let through short wave radiation from the sun but absorb the long wave heat radiation coming back from the Earth's surface and re-radiate it. These gases act like a blanket - and keep the surface and the lower atmosphere about 33°C warmer than it would be without them. The Earth's greenhouse blanket is a good balance between the extremes of our neighbours: Mars, which has no greenhouse gases is a frozen wasteland without life; whilst Venus remains trapped in a dense blanket of CO₂ and is consequently a very hot and hostile place, again without any possibility of life.
Source: The Carbon Trust, UK

It is possible that the global warming trend projected over the course of the next 100 years could, without warning, dramatically accelerate in just a handful of years - forcing a qualitative new climatic regime which could undermine ecosystems and human settlements throughout the world, leaving little or no time for plants, animals and humans to adjust. The new climate could result in a wholesale change in the earth's environment, with effects that would be felt for thousands of years.
USA National Academy of Sciences, February 2002

By drilling ice cores miles into the frozen ice in Greenland and in the Antarctic we can get a detailed temperature and CO₂ history of Earth's past. By obtaining an ice core sample 10,000 feet down in our ice sheets we are looking at ice made over 700,000 years ago and by analysing the minute bubbles of air trapped in this ice scientists can tell what the earth's temperature was at the time. In Figure 2 alongside, the graph gives the temperature and carbon level history of the planet over the past 400,000 years. Warm peeks interrupt long periods of cold ice age conditions and it is easy to see the direct correlation between temperature and CO₂ levels: as the greenhouse gases in the atmosphere rise, so does the temperature. During the last 14,000 years the earth has had one of its most stable periods in terms of temperature with small fluctuations of only 1 degree centigrade - this coincides directly to the stable period of 'civilisation' as we know it - conditions on Earth are ideal for crop development, animal life and human existence.

Figure 3 shows how CO₂ levels rose after the last ice age to a stable plateau of about 265 ppmv and the Earth's temperature averaged out to 0 degrees centigrade + or - 1 degree centigrade. The Lascaux Caves are dated at 14,000 years ago, Poliochni 6000 years ago and Troy was 3000 years ago, all evolving during the Earths 'stable' warm period. During the last 150 years, CO₂ levels have increased dramatically to a present day level of 380ppmv which is and will promote a direct rise in the Earths temperature. This is the threat of climate change - by the consequences of our life style we are forcing Earth out of her stable temperature period, which is so conducive to human existence, into the possibility of temperature rises and global instability. It is easy to see that a predicated Earth temperature rise of 3 degrees C would put the planet into a position it has not experienced for a hundred thousand years.

During the last 200 years we have very accurate temperature measurements which, since 1900 have been increasing steadily. This temperature rise in now understood to be a direct consequence of global industrial growth. The graph figures in Figure 4 show the average global surface temperature as measured (red line), compared to estimates from a computer simulation, respectively without (left) and with (right) the effects of human emissions included.
Source: Reproduced from Intergovernmental Panel on Climate Change, 2001

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