First published 13 December 2015
Your correspondent tries to keep an open mind which seems lacking in some of the pro and anti people who don’t seem able to ‘change their mind when the facts change’. Recently he has however been veering to the pro-anthropogenic side. So many denialist articles sound like the man with a very lethargic and sick looking dog. His neighbour pointedly comments on his condition. The man says he is unsure what has caused this. The neighbour suggests it was the beating the dog got the night before. The man says he does not think it can be that as the dog has been like this before but he has never before beaten the dog.
A recent edition of the Economist carried a lengthy special report on climate change but the cause was merely implied throughout with no discussion of the pros and cons. Some of the various points (made by various people, not necessarily the consensus view):
- To restrict the temperature rise to 2° the emissions must not exceed 3,200 gigatonnes of CO2 of which 2,000 are already out there.
- 2015 emissions are unlikely to exceed those of the previous two years
- Water vapour is the most important greenhouse gas followed by CO2 and CH4
- Without the greenhouse effect of gases the average temperature at the equator would be about -10°C
- The problem with CO2 is that it takes about 10 years to achieve maximum warming effect and 1000 years before significantly losing its effect.
- Warming in turn provides a feedback effect via higher water vapour and less reflective ice.
- If pollution per person is allocated according to the consumer of the goods rather than the producer then China is only equivalent to Europe and below the US.
- Anthropogenic climate change denialism is rare in Chinese politicians and attributed to the high proportion of engineers in that class.
- Doubling the concentration of CO2 in the atmosphere would increase effective heating by 4 watts/m2 but could therefore be offset by a 1.7% reduction in the 240w/m2 arriving from the sun. Various techniques for this are being investigated, including increasing the linear clouds that grow on aerosols emitted by ships (more effective than a carbon tax according to the Copenhagen Consensus Centre).