Global Warming II

The Weatherman entered the Iron Labyrinth in order to comment on the post "Global Warming". His comment is as follows:

Sorry... I don't buy it! "Predictions of global warming are based on computer climate modeling, a branch of science still in its infancy. The empirical evidence actual measurements of Earth's temperature shows no man-made warming trend. Indeed, over the past two decades, when CO2 levels have been at their highest, global average temperatures have actually cooled slightly." http://sitewave.net/pproject/s33p36.htm
Sure CO2 levels are increasing at this time. But for the last 300 years or so, they have been lower than usual and are increasing with the general warming trend since "The Little Ice Age". Human activity may certainly be adding to the CO2 increase, but there is also no actual evidence that this increase is causing any "warming effect". In fact, recent carbon dioxide rises have shown a tendency to follow rather than lead global temperature increases.

I do not agree with the two fundamental points of the criticism leveled by the Weatherman…

The comment that "Predictions of global warming are based on computer climate modeling, a branch of science still in its infancy" is dubious but not directly relevant since the reasoning in my original blog are not based on any climate modeling but rather on the known data on CO2. That is, I reason that since CO2 is a greenhouse gas, and since levels are rising, that the hypothesis that the global climate is warming follows. On the other hand, it is true that the RESULTS to be anticipated from global warming are sometimes predicted using computer modeling. These results include a global retreat of ice, decreasing salinity in high latitude oceans and seas, and slowing of the Gulf stream. All of these effects have been predicted by computer models and current trends are showing these models to be reliable. Examples of the first prediction, global retreat of ice can be seen in the Arctic where the Northwest Passage is now open for part of the year (http://www.carc.org/whatsnew/writings/amitchell.html), in Africa where the Furtwangler ice wall on Kilimanjaro has undergone a massive retreat in recent years (http://news.bbc.co.uk/2/hi/science/nature/2337023.stm), and in the Antarctic where glaciers are moving at an unprecidentedly high rate and the Larsen B ice shelf collapsed in 2002 (http://nsidc.org/iceshelves/larsenb2002/). There other easy to find sites which show observations of other predicted effects of warming.

The comment that "empirical evidence actual measurements of Earth's temperature shows no man-made warming trend. Indeed, over the past two decades, when CO2 levels have been at their highest, global average temperatures have actually cooled slightly" is not credible because it is based on some really sloppy data. The data, taken from The Petition Project at http://sitewave.net/pproject/s33p36.htm, shows a graph, their Fig. 5, which is taken from data by J. K. Angell at, http://cdiac.esd.ornl.gov/trends/temp/angell/angell.html. While Angell's original data is credible, the graphs by the Petition Project are so poorly designed that conclusions based them alone are suspect at best and bogus at worst. The Petition Project's Figure 5 looks like one of those puzzles entitled, "What's wrong with this picture?" First and foremost, the given trendline has no R-squared value associated with it and no prediction interval shown. Without those fit criteria, the conclusion made by the Weatherman, that "global average temperatures have actually cooled slightly" is unsupported. Further, the line in Figure 5 uses a sub-set of Angell's data without giving a reason for discounting the other data in the set. That is, for some reason, Figure 5 only fits a line using data from 1978 to present, not the full set of data from 1958 to present. Since a line fitted to all of the data available (1958 to present ) would yield a positively sloped trendline rather than a negative one, and since the conclusion drawn is based entirely on the trendline slope, it is difficult to see why one should credit the data from Figure 5 at all. Further, The Petition Project's data in other associated graphs are subject to similar criticisms. By way of comparison, I took the full range of Angell's data from 1958 to 2004 based on Annual surface conditions and found that a fitted trendline has a POSITIVE slope (m=0.0162), that R-squared is 0.58 and that the 95% prediction interval does NOT contain ANY lines of negative slope… That is, a graph based on the relevant data as published by Angell contradict the Weatherman's conclusion that "global average temperatures have actually cooled slightly". The data supports the conclusion that we can be at least 95% certain that global average temperatures are rising: exactly what one would expect as CO2 levels rise.

Since the margin of the Weatherman's comment relies on the above arguments, and since I do not find his above arguments credible, I will not address the margin of the comment.

I invite further commentary.