Not since and other climate change questions

We greatly enjoyed the huge response to our article about climate change. It is clear that there is both a great deal of interest and a great deal of confusion about the science of climate change, write Doug Mackie, Hugh Doyle and Paul Young.

We have compiled some of the most common scientific claims taken from the 940 submissions made about the Emissions Trading Scheme and we invite comments and questions.

If this is successful we will add more claims later but for now we will only respond to comments that are on topic. We have excluded non-scientific claims (eg"It is all a hoax"), but can come back if there is interest.

• Click here to read reader questions and the researchers' answers

Not since.
This was the topic of our last article and is the idea that "the slight warming that occurred between 1979 and 1998 has been followed by stasis and, since 2002, cooling."

To the right are the graphs we used to show this claim is invalid because such short time periods are weather, not climate.

2. Natural cycle.
This is the idea that climate varies naturally and that current variation is due to changes in a stated factor (such as solar output or El Nino). We agree climate varies naturally.

However, natural changes and human-induced changes are not exclusive.

The current change in atmospheric CO2 is superimposed over and above natural changes. Furthermore, the rate of current change is unprecedented for at least the last 8 "ice ages", further suggesting it is not natural. At the end of an ice age CO2 typically goes up by about 100 parts per million (ppm) over about 10,000-15,000 years (i.e. less than 0.01 ppm per year). Currently CO2 is increasing at more than 2 ppm per year. This is over 200 times faster than changes associated with the natural CO2 cycle.

3. Carbon cycle
We included this because it has increased hugely in popularity; 18th in 2008 to 12th in February 2009 to 4th place in October 2009. This claim states agricultural emissions are a closed cycle and do not require regulation because grass takes up CO2, cows eat grass and belch methane and then the methane is oxidised to CO2 and taken up by the grass.

However, this neglects the fact that methane is better at trapping heat than CO2 and until the methane is oxidised (about 8 years) it causes extra warming.

It is like saying because you borrowed $100,000 at 9% for 8 years and then earned 4% interest on $100,000 saved for 8 years that your finances are balanced.

Editor: ODT Online invites all those who have contributed to the debate thus far, and indeed any reader interested in climate change, to question the authors using the comment window below  These comments will be forwarded to the authors who will provide a response. The comments and their reponses will then be published. The cut-off date for comments is Monday, November 16.