User:Co2denier

The scientific basis for limiting CO2 emissions is summarized by two sentences in the “Summary for Policymakers” of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Both are in a paragraph from Section 2, “Causes of change” of AR4.

"During the past 50 years, the sum of solar and volcanic forcings would likely have produced cooling. Observed patterns of warming and their changes are simulated only by models that include anthropogenic forcings."

The term “forcings” is the climatologist’s way to quantify the impact of potential contributors to global temperatures in their computer models. Positive and negative forcings denote global warmers and global coolers respectfully.

The first sentence reflects the IPCC climatologist’s assessment that the combination of the sun and volcanic activity would have reduced global temperatures. When they used their estimated “cooling” forcings in the computer model the results, not surprisingly, predicted slight declines in global temperatures over the last 50 years.

As the second sentence explains, rather than “adjust” the sun and volcanic activity forcings, the climatologists assumed the computer model failure was due to a lack of “anthropogenic” green house gases (GHG) primarily CO2 forcings. Raising the computer model “predicted” temperatures to the measured levels required GHG forcings 10 times climatologists estimates for the Sun. It is this level of forcings that makes global temperatures so sensitive to increased GHG emissions and has led to billions spent attempting to reduce their emissions.

It’s not clear why climatologists concluded any potential warming from the Sun was “likely” more than offset by the cooling effects of volcanic ash during the last 50 years. The combination of the two has been largely responsible for many warming and cooling periods for hundreds of thousands of years. Global temperatures during the Medieval Warming Period in 1000-1100 AD were at least as high as current levels. The MWP was followed by cooling, presumably due to some combination of reduced energy from the sun and/or more volcanic ash that lasted until the end of the Little Ice Age of the mid 1800’s.

Much of the temperature increase after 1850 occurred prior to significant GHG emissions. What led climatologists to conclude the combination of the Sun and volcanic activity would reduce rather than increase global temperatures during the last 50 years? Why assume the increase was due to relatively small changes to atmospheric CO2 levels from ~ .031% to .036% during that time period? Particularly since subsequent increases to ~.040% recently haven’t resulted in any significant additional global warming?

The only link between atmospheric CO2 levels and global temperatures was an early assessment (Al Gore (?)) showing global temperatures tended to increase, purportedly in response to higher CO2 levels. However, an article recently published in “Climate of the Past” about East Antarctic ice core studies showed CO2 levels lagged temperature changes by 500 to 5000 years. Obviously increasing CO2 can’t cause global warming if it occurs after the increase.

In conclusion, the hundreds of billions already spent limiting GHG will be dwarfed by the costs associated with future efforts. Climatologists need to do more to justify the need to do so beyond “During the past 50 years, the sum of solar and volcanic forcings would likely have produced cooling.”