These points were originally included in my essays, but removed to keep those arguments as focused as possible. But I do still think these are important points to be aware of…
CO2 Lags Temperature
One of the specific points I find more important is the historical correlation of carbon and temperature. I’m not sure how often this perspective finds the mainstream discussion, but Al Gore’s Inconvenient Truth strongly implies that there is causality on the side of carbon driving increases in global temperatures. However there is wide agreement that based on Antarctic ice core data, changes in CO2 have followed changes in temperatures by about 600 to 1000 years.
This is consistent with carbon being one of the smaller temperature feedbacks, which seem to be dominated by water vapor and clouds. This “carbon lag” is accepted by both sides, and creates a opportunity for AGW proponents to confirm that CO2 has not been a dominant driver of climate and the real debate is focused on the feedback loops.
Some critics of this “lag” argument cite our current century as the one counter-example when temperature changes have lagged behind carbon changes (Al Gore’s side of causality). But in order to consider this modern counter-example as evidence of carbon being a significant driver of temperature, you must first presume the certainty of the above AGW models. So again, this counter-argument begs the question.
Changes in CO2 have lagged behind changes in temperature, so if there is causality within their correlation, the historical record demonstrates the opposite of popular opinion.
While this correlation is not inconsistent with basic carbon-temperature feedback concepts, many assumptions are necessary to count it as solid evidence for the large multiplying feedbacks in the models. Increases in carbon, one of the weaker greenhouse gasses, have never caused temperature increases before this century, so the burden of proof remains on the AGW models and the correlation cannot support the theory of catastrophic man-made global warming.
For more than five years I have been asking carbon-related questions, and I am more concerned about man-made elements added to the periodic table. Novel elements we have invented for the first time earth’s known history, which may affect the environment (and us) but not necessarily the climate.
The graph above with temperature and carbon over the past 400,000 years shows us in our current higher temperature ballpark every 100,000 years or so. Had we modernized 20,000 years earlier, there would be zero concern on rising temperatures because we would be debating at a low-point in the 10 degree Celsius fluctuations within this time-scale.
The following chart is the most common perspective in the mainstream discussion of this debate. It goes back until only 1880, and is very short-sighted but helpful for encouraging alarm:
It should be noted that in this graph above does not have the scope of the current century, where atmospheric carbon levels approach 400 ppm. This rise of carbon before temperature is certainly an anomaly without historical precedent. But also keep in mind that each doubling of CO2 concentration, temperature increases by a constant value.
Anatomically modern humans had thousands of years on an earth more than 2.5 degrees Celsius warmer than this century (almost 5 degrees Fahrenheit warmer):
And our great ape ancestors lived on an earth more than 7 degrees Celsius warmer than this century (around 13 degrees Fahrenheit warmer). It was definitely very different, and might not be preferable, and a rapid rate of temperate change may be another issue, but those temperatures alone were clearly not catastrophic enough to prevent our evolution or complete destruction of ecosystems.
And of course, the concern is really about maintaining our human status quo, life on earth itself will go on with or without us, and is not threatened.