http://www.americanthinker.com/2012/08/winning_the_agw_science_debate_heres_how.html
The upcoming election battles may be unique in offering for the first time a debate about global warming. Neither Bush-Gore nor McCain-Obama chose to discuss the issue — maybe because they were not really that far apart. By contrast, Barack Obama has already announced that, if re-elected, he will make climate change an important priority — while Paul Ryan is an assertive skeptic on AGW (anthropogenic global warming).
The science of climate change is not just of academic interest, but has been leading to policies for large-scale changes in energy use and supply — with important economic consequences. The burden of proof for AGW therefore falls on those who call for such policies. They must demonstrate with reasonable certainty that human activities are causing global warming, that a future warming will produce significant economic and ecological damage, and that it would be more cost-effective to mitigate now rather than to adapt later. They must also be ready to respond to any critique of the underlying science.
A recent example of irresponsible AGW claims is a just-released statement by the American Meteorological Society — the same crew that cannot predict the weather three days in advance. The concluding section begins:
There is unequivocal evidence that Earth’s lower atmosphere, ocean, and land surface are warming; sea level is rising; and snow cover, mountain glaciers, and Arctic sea ice are shrinking. The dominant cause of the warming since the 1950s is human activities. This scientific finding is based on a large and persuasive body of research. The observed warming will be irreversible for many years into the future, and even larger temperature increases will occur as greenhouse gases continue to accumulate in the atmosphere. Avoiding this future warming will require a large and rapid reduction in global greenhouse gas emissions. The ongoing warming will increase risks and stresses to human societies, economies, ecosystems, and wildlife through the 21st century and beyond, making it imperative that society respond to a changing climate.
I would start by asking AGW supporters the following question: “What is your single most important piece of evidence for AGW?” I have received many answers to this question; most of them can be disposed of in a trivial way. Some examples are:
* “Man-made CO2 is increasing in the atmosphere.” True, but is warming increasing as a result?
* “Climate models predict rising climate temperatures in the future.” True, but models are not evidence.
* “Glaciers are melting, sea ice is shrinking, storms are increasing, droughts and floods are increasing.” Even if any of these were true, they don’t reveal the cause and certainly cannot furnish temperature data like thermometers.
* “Sea levels are rising.” But they have been rising for 18,000 years, and there is no evidence that the current rate of rise is affected by temperature; 20th-century data show no acceleration.
* A common misleading reply by AGW supporters: “The past decade is the warmest in X years.” This may be true, provided X is chosen appropriately, but the current trend over the past decade has been approximately zero. (One must not confuse Trend [measured in degrees C/decade] with temperature [measured in degrees C]. According to climate models, it is an increased temperature trend that should relate to any increasing trend in greenhouse gases.)
But note also that climate seems to follow long-term cycles of about 1,500 years (Singer and Avery, Unstoppable Global Warming: Every 1500 years, 2007). If the “Bond-cycle” is active now, we may expect further, irregular warming in the present century and beyond — entirely due to natural causes, likely related to the Sun.
Finally, a common response simply appeals to the report of the U.N.-IPCC (Intergovernmental Panel on Climate Change). To which one should say: “OK, then let’s see if it holds up to scrutiny.” (Note that the “evidence” presented as crucial has been different in every one of the past four IPCC assessment reports.) The latest IPCC claim for AGW is laid out simply in the Summary for Policymakers on page 10 of the 2007 report: “Most of the observed increase in global average temperatures since the mid 20th century is very likely [i.e., 90-99% sure] due to observed anthropogenic increase of greenhouse gases.”
* This claim is advanced in the SPM and eventually backed up by fig. 9.5 on page 684 of the 2007 report. The models are “fitted” to the observed temperature record from 1900 up to about 1970 by choosing suitable sensitivities and model parameters, using “expert judgment.” But the figure shows a large gap after 1970 between reported temperatures and unforced models (i.e., models that do not incorporate an increase in GH (greenhouse) gases).