In response to Mike Bishop's letter
Mike Bishop is right that the candidates at the recent Hustings on the Environment could have done more to champion climate science. A questioner asked candidates to comment on what was described as the microscopic influence of humans on CO2 increase. From the questioner's perspective, climate change, if it existed, could not be caused by humans.
In the first instance, it is not the scale of the emissions but the impact which is important. Each decade since the 1980s has been hotter than the previous decade. 2010 was the warmest year on record, tied with 2005. Research shows that the earth is now 0.85℃ hotter than before the Industrial Revolution.
In the overall scheme of things humans do emit a relatively small amount of CO2. But for a very long time the earth's natural carbon cycle has remained roughly in balance. Around 750 gigatonnes of CO2 are emitted by natural processes each year, which are then reabsorbed by other natural processes.
Humans, as a result of burning fossil fuels at an unprecedented rate, are adding carbon dioxide faster than the earth can now absorb. We emit around 26 gigatonnes of CO2 each year. Some of this is absorbed by carbon sinks, such as forests, but a net 15 gigatonnes is added to the atmosphere each year.
The link between atmospheric CO2 and temperature increases is accepted by 97% of climate scientists, and by 80 National Academies of Science, such as the Royal Society.
It was also suggested that climate change has 'paused' since 1998. In fact there are many critical indicators of a warming world, including shrinking ice sheets, rising sea levels, increased humidity, increasing air temperature, ocean warming and acidification, declining Arctic sea ice and glacial retreat.
Each of these indicators shows that warming is occurring at an alarming rate - see the NASA evidence
There is also an increasing body of evidence linking the increase in extreme weather events to climate change, for example a recent paper on heat extremes, published in Nature Climate Change, and analysed here.
For those who want more, click here for this is a great little video: 13 Misconceptions About Global Warming
Chair of the Hustings on the Environment