Climate Change - 8 Arguments

Global Warming 

There are a number of key issues relating to Climate Change and the consequences of Global Warming, the top 8 arguments appear to be the following:

1. The Earth's climate is always changing and this is nothing to do with humans. Even before the industrial revolution, when humans began pumping carbon dioxide into the atmosphere on a large scale, the earth experienced warm periods.

There have indeed been warmer and colder periods in the past for which Man cannot be held responsible, the great Ice Ages are probably the best example but there have been times when grapes were extensively grown throughout England (the Medieval Warm Period) and phases when the Thames froze annually (the Little Ice Age). But the temperature rises over the past 100 years on land and in the oceans cannot be explained simply by Sun activity or changes in the Earths orbit. Eleven of the last twelve years have been the hottest since records started in 1850.

The greenhouse gas effect keeps the Earth 30 degrees C warmer than it would otherwise be as these gases blanket the Earth stopping heat escaping back into space. An increase in the level of gases results in more heat being trapped in the atmosphere - global warming. Levels of carbon dioxide are currently 35% greater than they have been for 650,000 years, evidenced from core samples taken from polar ice caps. Burning of fossil fuels, production of cement and widespread burning of the world's forests are the main causes of the rise in greenhouse gas levels.

2. Carbon dioxide only makes up a small part of the atmosphere and so cannot be responsible for global warming.

The properties of greenhouse gases such as carbon dioxide mean that they strongly absorb heat. Other gases in the atmosphere may have larger concentrations, such as nitrogen, but these gases do not possess heat trapping qualities so do not affect the climate's temperature.

Man has been adding to the effect of naturally occurring greenhouse gases by pumping carbon dioxide into the atmosphere through the burning of fossil fuels and deforestation. Before industrialization carbon dioxide made up about 0.03% of the atmosphere or 280ppm (parts per million). Today, due to human influence it is about 380ppm. Even these tiny quantities have resulted in a small, but significant increase in global temperatures.

3. Rises in the levels of carbon dioxide in the atmosphere are the result of increased temperatures, not the other way round.

Fluctuations in temperatures that caused the ice ages were initiated by changes in the Earth's orbit around the Sun, which in turn, drove changes in levels of carbon dioxide in the atmosphere. This is backed up by data from ice cores which show that rises in temperature came first, and were then followed by rises in levels of carbon dioxide up to several hundred years later.

In contrast the recent steep increase in the level of carbon dioxide - some 30 per cent in the last 100 years - is not the result of natural factors because chemical analysis indicates that the majority of this carbon dioxide has come from the burning of fossil fuels.

4. Observations of temperatures taken by weather balloons and satellites do not support the theory of global warming.

Discrepancies have been found to be related to problems with how data was gathered and analysed and have now largely been resolved. Understanding of global warming leads us to expect that both the lower atmosphere (the troposphere) where most greenhouse gases are found and the surface of the earth should warm as a result of increased levels of greenhouse gases in the atmosphere. At the same time, the lower stratosphere, the part of the atmosphere above the greenhouse gas blanket should cool. It is now agreed that the warming in the troposphere is shown to be broadly consistent with the temperature trends seen at the earth's surface.

Some of the cooling at the lower stratosphere is not related to increased levels of greenhouse gases but due to a different impact that humans have had on the atmosphere - the depletion of the ozone layer. Ozone warms the stratosphere by trapping incoming energy from the sun. This reduction of ozone also has knock on effects on other parts of the atmosphere, underlining the importance of taking all factors into account when looking at what is happening to our climate.

5. Computer models which predict the future climate are unreliable and based on a series of assumptions

By creating computer simulations of how different components of the climate system - clouds, the Sun, oceans, the living world, pollutants in the atmosphere, etc., behave and interact, scientists have been able to reproduce the overall course of the climate in the last century. Using this understanding of the climate system, scientists are then able to project what is likely to happen in the future, based on various assumptions about human activities. But computer models cannot exactly predict the future because there are too many 'unknowns'.

Climate models are not sufficiently well developed to project accurately all the detail of the impacts we might see at various levels but they do give us a reliable guide to the direction of future climate change.

6. It's all to do with the Sun - for example, there is a strong link between increased temperatures on Earth with the number of sunspots on the Sun.

Change in solar activity is one of the many factors that influence the climate but cannot, on its own, account for all the changes in global average temperature during the 20th Century. Measurements from satellites show that there has been very little change in underlying solar activity in the last 30 years.

The magnitude and pattern of changes to temperatures can only be understood by taking all of the relevant factors both natural and human into account. For example, major volcanic eruptions produce a cooling effect because they blast ash and other particles into the atmosphere where they persist for a few years and reduce the amount of the Sun's energy that reaches the Earth's surface. Also, burning fossil fuels produces particles called sulphate aerosols which tend to cool the climate in the same way.

Over the first part of the 20th Century higher levels of solar activity combined with increases in human generated carbon dioxide to raise temperatures. Between 1940 and 1970 the carbon dioxide effect was probably offset by increasing amounts of sulphate aerosols in the atmosphere, and a slight downturn in solar activity, as well as enhanced volcanic activity. However, in the latter part of the 20th Century temperatures rose well above the levels of the 1940s.

7. The climate is actually affected by cosmic rays.

Any effect that cosmic rays could have on the climate is not yet very well understood but it is generally accepted that if there is one, it is likely to be small. Cosmic rays are fast moving particles which come from space and release electric charge in the atmosphere. Experiments done in a laboratory hint that cosmic rays could play a role in the development of tiny particles that could in turn play a part in the formation of clouds which generally have a cooling effect by reflecting the Sun's rays back into space.

Even if cosmic rays were shown to have a more substantial impact, the level of solar activity has changed so little over the last few decades the process could not explain the recent rises in temperatures.

8. The scale of the negative effects of climate change is often overstated and there is no need for urgent action.

The Intergovernmental Panel on Climate Change (IPCC) - the world's leading authority on climate change - has projected an expected global average temperature increase this century of 2 to 3 ?C. This would mean that the Earth will experience a larger climate change than it has experienced for at least 10,000 years. The impact and pace of this change would be difficult for many people and ecosystems to adapt to. In the short term, some parts of the world could initially benefit from climate change. More northerly regions of the world may experience longer growing seasons for crops and crop yields may increase because increased levels of carbon dioxide in the atmosphere would have a fertilizing effect on plants.

However the IPCC has pointed out that as climate change progresses it is likely that negative effects would begin to dominate almost everywhere. Increasing temperatures are likely, for example, to increase the frequency and severity of weather events such as heat waves, storms and flooding. Increasing temperatures could lead to the melting of large ice sheets with major consequences for low lying areas throughout the world. Impacts of climate change will fall disproportionately upon developing countries and the poor, those who can least afford to adapt. Thus a changing climate will exacerbate inequalities in health and access to adequate food and clean water.

The Ringmaster

(Sources New Scientist & The Royal Society)