The one good thing that the IPCC - Al Gore AGW campaign has done is to draw attention to the importance of Climate Science in attempting to evaluate future threats to the basic problem of feeding the estimated 9 billion expected on earth by mid- century. Unfortunately the science was distorted and "results " hyped to promote the political agenda ,career interests and financial interests of various parties with varying motivations. What can we agree on? I think the following statements represent what we know and how certain we may be about the "facts"
1. The quality of the basic temperature data base is not very good.
2 . In the 20th century temperatures rose from 1900 - 1940. dropped from 1940 - 70 and rose from 1970 to a peak about 2003. There was about 0.8 degrees warming in total.
3. Temperatures have entered a downtrend since then.
4. These general trends are perturbed by El Nino - La Nina and volcanic events
5. CO2 rose steadily during this period but the CO2 trend is not correlative with the temperature trend.
6. Ice core data shows that CO2 follows temperature not vice versa.
7. CO2 is a greenhouse gas.
8. Anthropogenic CO2 has contributed some ,probably small, amount to 20th century warming.
9.Until we know the forcings and feedbacks of the natural system we can't calculate with any accuracy the contribution of anthropogenic CO2 to the temperature.
10.In any event the temperature - CO2 equation is logarithmic so that any future increase in emitted CO2 has progressivley smaller effect.
11. Warm periods with higher CO2 are good for mankind and food production in general.
12. Abundant geologic data and gelogic history show very clearly that the sun is the main climate driver.
13 Our investigation of the Sun - climate system is really only just starting but Milankovich orbital cycles are well documented as are solar activity cycles of various lengths which interact with each other in complex ways.
14. Total Solar Irradiance is only one measure if solar activity . The Svensmark solar magnetism - GCR - cloud cover hypothesis is supported by a lot of evidence and is probably true.
15.Based on current solar activity and the current negative phase of the Pacific Decadal Oscilation we are more likely than not to have 20 - 30 years of cooling with maybe a Dalton or even a Maunder minimum. Solar magnetic field strength has dropped precipitously over the last 5 years .
16. One or two degrees of cooling might well produce occasional serious crop failures in the worlds chief growing areas. This would be much more dangerous to the population than a warmer world with more CO2.
17. Government efforts would be better directed towards preparing for cooling rather than warming. eg building grain and cattlefeed stockpiles.
18. The IPCC Summary for Policy makers should be abandoned as a guide to future climate trends because our knowledge is insufficient to predict temperatures 100 years out with any accuracy at all.. This is the scientific conclusion of the IPCC itself . The WG1 ( science) section on climate forcings and climate sensitvity concludes (8.6.4)
"Moreover it is not yet clear which tests are critical for constraining the future projections,consequently a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed"
What could be clearer. The IPCC says that we dont even know what metrics to put into the models to test their reliability.- ie we don't know what future temperatures will be and we can't calculate the climate sensitivity to CO2 with any certainty.This also begs a further question of what mere assumptions went into the "plausible" models to be tested anyway.Nobody ever seems to read or quote the AR4 - WG1 report- certainly not the compiler of the Summary or the AGW faithful.
19. The chief threat to the environment and humanity is the expected population increase.
20. The best way to control that is to increase as quickly as possible living standards throughout the world and at the same time raise the status and education of women.This latter will also require changing cultural behaviour in large groups of populations.
21. The world needs to get energy to the developing world as cheaply and as quickly as possible.Fossil fuels are the cheapest energy source for the forseeable future and should be extracted and used in as environmentally friendly way as possible while remembering that CO2 is an effecint fertiliser and not a pollutant and does not need to be controlled.