In reply to Michael G Wells' letter concerning global warming printed in last week's edition, I'd like to take the opportunity to respond and provide some balance to the argument.

In his letter he claims that global warming and climate change are an "entirely natural phenomenon" when in fact plenty of research has proved this not to be the case.

Claims of human activity causing a miniscule 0.0002 per cent increase in carbon dioxide levels is both inaccurate and, like many statistics, given without being put in any sort of context.

Carbon dioxide levels (as a percentage of the composition of all atmospheric gases) have in fact risen by about 0.009 per cent in the last 250 years. This is after many millions of years of relative stability and is largely attributed to the industrial revolution which sparked our thirst for energy. This was provided by the burning of carbon-based fossil fuels.

However, even though this figure is almost 50 times greater than the figure quoted by Mr Wells (although he doesn't state what his figure is a percentage of), by itself it too means little. Put it alongside the actual percentage of carbon dioxide in the atmosphere now and 250 years ago and this 0.009 per cent change in the total amount of carbon dioxide in the atmosphere equates to about a 30 per cent increase in the level of carbon dioxide itself (250 years ago = 0.0028 per cent, today = 0.0037 per cent). In context, this is clearly a significant increase.

Science (and yes, it is science taking these samples, carrying out this analysis and interpreting the results) has further proven that the level of carbon dioxide from burning fuels (as opposed to that which is naturally occurring) has increased by isotopic analysis of the carbon atoms found in atmospheric CO2, to name just one method of analysis.

I agree, carbon dioxide is part of the life blood of our planet, playing a major role in the carbon cycle, particularly via photosynthesis without which our planet would be devoid of plant life (and eventually human life). However, human activity has upset the equilibrium and is causing CO2 levels to rise thanks to our desire to burn fuels to release their energy.

Science understands that increasing CO2 levels prevent heat from escaping from our planet (the proverbial greenhouse effect) causing atmospheric temperatures to rise. Until we stop releasing CO2 from fossil fuels into the atmosphere, global warming caused by humans will continue.

RUSS CHURCH

Weston Walk

Frome

Are Michael G Wells' motives for attacking "global warmers and climate change controllers" in the Standard similar to those of the people he quotes?

Ian Plimer, as well as being a university professor, is a director of a coal-gas company and the author of a book, Heaven and Earth, which has been widely derided for its lack of scientific references. For example, his claim that volcanoes produce more CO2 than human activity is contradicted by a US Geological Survey report that humans produce 130 times as much as volcanoes, including those beneath the sea.

Prof Plimer claimed that global warming has stopped; this was based on his choice of the hottest year ever, 1998, as his starting point. Had he picked any other year, he would have noticed that temperatures have steadily risen over the past century.

Willie Soon has received more than a million dollars from petroleum and coal interests since 2001. His research budget has been supported by the American Petroleum Institute, Mobil and Texaco. He was a paid consultant of the George C Marshall Institute, of which Exxon-Mobil has been a major funder. The Institute has, in order to resist and delay regulation, lobbied to create a false picture of scientific uncertainty about the effects of passive smoking, the links between smoking and cancer, the existence of acid rain and the evidence of the impact of CFCs on the ozone layer.

There has always been debate about scientific evidence and it is always possible to find something that reinforces one's opinions – Charles Darwin was accused of blasphemy. I have learned to be suspicious of anyone whose published views are supported by finance from multinational companies; as Mr Wells so aptly puts it, "driven by scientists who see an opportunity to make money".

ORLANDO GOODDEN

Catherine Street

Frome