Given the recent series of posts promoting global warming hysteria, I want to give the board an overview of my beliefs regarding the anthropogenic global warming (AGW) theory. I also want to point out what the settled facts are, and identify those parts which are simply hypothesis. I am an AGW skeptic, but not a global warming skeptic. The Earth warms and cools in constant cycles of varying lengths. In the very short term, local temperatures warm during the day and cool at night. Any given area will warm every summer, and cool every winter. There are also longer-term trends, where the Earths climate fluctuates between ice ages and interglacial warm periods. I do believe that the Earth is in a 100-year warming trend, so in that sense, I do believe in global warming. I also acknowledge that the Earth is in an 8-year cooling trend, a fact not popular among true climate change deniers. Of course, 8 years isnt that significant. But is 100? 500 years ago, the Vikings were farming Greenland, which is basically a glacier nowadays. If anecdotal evidence passes for hard science, isnt Greenland an excellent example of long-term global cooling? If 500 years isnt enough - 35 million years ago, the Colorado River was flowing through the present-day Grand Canyon. Id say the local climate there has changed quite a bit. None of the above facts prove or disprove AGW theory but to suggest the climate was virtually static before man intervened is complete and utter nonsense. So weve established that the Earth has been in a 100-year warming trend about .6 degrees Celsius over the past 100 years. Of course, mankind has only been systematically measuring temperatures for 100 years, so all this suggests is that it is warmer today than it was at the arbitrary point at which man began recording temperatures. Coincidentally, two things happened at that point: 1) The Earth was emerging from an era known as the Little Ice Age a period so cold that the Thames froze over yearly in England, and a multitude of people were able to migrate to America over the Bering Land Bridge. 2) The industrial revolution that led to man producing significant amounts of CO2 emissions. So right from the get-go, the AGW claim is that temperatures 100 years ago were normal, and modern-day temperatures are abnormally high. Really? It cant possibly be the case that todays temperatures are normal, and 100 years ago the Earth was abnormally cold? What exactly is normal in a constantly fluctuating climate? Oh, I know, the arbitrary point at which man began recording temperatures. How scientific! Getting into the theory of AGW, its a bit of a mish-mash of facts and theory that some folks have trouble discerning. It is indeed true that the global average temperature has risen over the past 100 years, and it is also true that weve increased atmospheric CO2 concentrations by 1/3 through the burning of fossil fuels (from 280 PPM to 384 PPM). That might seem like a lot, but when I pose the data a different way, the impact seems trivial. Pre-Industrial Levels: CO2: .028% Other Atmospheric Components: 99.972% Present-Day Levels: CO2: .0384% Other Atmospheric Components: 99.9616% It is also true that carbon dioxide can act as a greenhouse gas, and can trap heat that would otherwise escape into space. But the very study that validates CO2 as a greenhouse gas also proves that there is a diminishing return relationship between CO2 concentrations and temperature forcing. As concentrations approach infinity, the total possible temperature increase levels off logarithmically around 1.2 degrees C. This is because CO2 can only absorb select frequencies of infrared radiation and as such, each additional increment of CO2 traps less heat than the previous. Thats where the facts end and the theory begins. AGW theory makes some assumptions about how this initial temperature forcing will resonate in the Earths climate system. According to alarmists, the initial CO2 forcing will trigger incredibly strong positive feedback mechanisms that will amplify and accelerate the warming (by 200-1000% or more)! These feedbacks include reduced ice albedo, and increased evaporation which leads to more atmospheric water vapor (a much more powerful greenhouse gas). These feedbacks are plausible, but they are theoretical (read: no empirical evidence) and certainly not the only feedback effects at work. In any naturally occurring long-term stable system you can think of, negative feedbacks outweigh the positive feedbacks, and I believe this is the case in the climate system. Negative feedbacks promote long-term stability by keeping a system within a natural range of variation. Variance is perfectly normal in a long-term stable system, as forcings in multiple directions keep the system within a range centered around an equilibrium point. Increased plant growth and low cloud formation are among these negative feedbacks that have a cooling effect, dampening the CO2 warming. Unlike the positive feedbacks, there is empirical proof that these effects are triggered by temperature increase. Yet climate models typically build in assumptions that these proven negative feedbacks are masked by the theoretical positive feedbacks. That doesnt make a whole lot of sense to me, and I take exception to a theory built on what I consider some very questionable assumptions. If the Earths climate is governed by natural positive feedbacks, then why do alarmists claim the Earths climate was extremely stable before man intervened? Shouldnt other slight disturbances have led to runaway warming in the past? In data primarily gathered from ice cores, we see carbon dioxide levels were 500 times higher during the Cretaceous period, some 160 million years ago. But no runaway warming occurred then, so why is it certain that CO2 will trigger runaway warming now? This claim and the assumptions about positive feedbacks are extremely paradoxical. But thats where the doomsday scenarios come from the belief that climate reacts profoundly to the temperature forcing of CO2 (called climate sensitivity in the IPCC reports). When you plug a large climate sensitivity multiplier into forecast models, obviously the models output will reflect this multiplier. But if the magnitude (and quite possibly, the sign!) of this multiplier is questionable, then so is the models output. Is there incentive to produce models with these doomsday forecasts? Absolutely. By presenting the possible threats of the situation, climate scientists can make a case to justify increased funding to study the problem and seek solutions. The more dire the situation they present, the greater case they have for continued study. Should we employ a carbon abatement strategy, just in case? In my belief, no. If you want to talk about strong correlation, prosperity in the modern world and carbon emissions go hand-in-hand. There is tremendous opportunity cost to carbon abatement in terms of future wealth. Curbing worldwide economic growth by 2% (say, from 4% to 2%) results in an economy one-seventh the size of its potential (compounding over 50 years). That is a huge loss in wealth. Would you purchase home insurance if the cost exceeded the cost to rebuild your home from scratch? Increased wealth wont prevent future natural disasters, but it will sure do wonders for mans ability to cope with them. The Earths climate is unpredictable and driven by countless interactions. The greenhouse effect is one of the factors that determines climate, but it is not the driver. The greenhouse effect and atmospheric CO2 are naturally occurring and absolutely essential to sustain life. To suggest that such a slight increase in this effect (which again, is ABSOLUTELY ESSENTIAL TO OUR EXISTANCE) will trigger catastrophic warming? Mother Nature sure has a cruel sense of irony! And if you want a concrete example of leaping from hypothesis to claimed fact, look no further than local Chicken Little, Kirk. Within days of posting a link to an article, The North Pole Might Be Briefly Ice-Free this Summer, he added such posts as Weve melted the pole, Dude! and Weve melted the pole in 50 short years! Suddenly, possibility became reality, and fossil fuels became the definite culprit. Classic make-believe. If anyone can find legitimate flaws or holes in my chain of thought, Ill be glad to reconsider. But no amount of scare-mongering will convince me, as I prefer rationale when discussing scientific matters.