I read this piece about the problems of man-made global warming theory on Anthony Watts "Watts Up with That?" site. The piece, which is titled "Disproving The Anthropogenic Global Warming (AGW) Problem", is written by Dr. Leonard Weinstein (bio at the bottom of this page).
The opening paragraphs of Weinstein's paper are straight forward and well explained for the most part. Weinstein then lists six of the main predictions of man-made global warming models and then tries to show you why each one of those predictions is wrong.
Weinstein makes some strong points, but he also seems to be doing some cherry-picking as well. Let's take a look..........
1. While global atmospheric CO2 has indeed seen its steepest increase since 1940, it was already sharply increasing since the 1850's (industrial revolution). The atmospheric CO2 levels between 1940 and 1970 do not even compare (much lower) to what they are predicted to be from 2010 to 2100. Perhaps the modeling expects that these much higher levels of atmospheric CO2 in the future will be high enough to completely overwhelm natural climate cooling variables such as aerosols, la Nina, changes in the sun etc.....
Weinstein also states....It is also true that the present temperature trend is down and expected to continue downward for several more years before reversing again. What is his version of the present trend? This past year, past 5 years, 10 years? Also, some sources do predict a downward or stable trend for several years, while other sources disagree.
2. Weinstein states......The drop in temperature from 1940 to 1970 was claimed to have been caused by "global dimming" caused by aerosols made by human activity. This was stated as dominating the AGW effects at that time. This was supposed to have been overcome by activity initiated by the clean air act. In fact, the â€œglobal dimmingâ€ continued into the mid 1990â€™s and then only reduced slightly before increasing more (probably due to China and other countries increased activity). If the global dimming was not significantly reduced, why did the temperature increase from 1970 to just past 2000?
Weinstein seems to have forgotten about Mt. Pinatubo. Look at the chart below, courtesy of NASA, which plots global dimming aerosols. There was plenty of global dimming in the early 90s due to that volcano, but if you take out that volcano, then you can see there has been a steady decrease in global dimming aerosols from the 1980's through 2005.
3. Weinstein states......Claim 4 implies that the higher latitudes should heat up more than lower latitudes. In fact, the higher latitudes have warmed, but at a rate close to the rest of the world.
A rate close to the rest of the world? Not according to the RSS microwave satellite measurements. Check this out.........
His statement seems true in regards to the southern high latitudes since the 1980s, but it is clear that the northern high latitudes have warmed much more than the rest of the world since the mid 1990's. The far greater sea-surface area in the southern latitudes probably has a lot to do with the much more stable temperature anomaly trend down there, compared to the north.
4. Weinstein states.....In fact, Antarctica has overall cooled in the last 50 years except for the small tail that sticks out.
Not according to this research from Nature Journal back in Dec 2006, which shows a reconstruction of Antarctic temperature anomalies since 1957 over east and west Antarctica. According to the study.....the continent-wide average near-surface temperature trend is positive.
I am not saying that Weinstein is wrong. I am not sure. There is obviously some difference in opinion in regards to this 50-year trend.
5. Weinstein states.....Greenland and the arctic region are presently no warmer than they were in the late 1930â€™s, and are presently cooling!
Where is that cooling he was talking about? I guess he meant parts of Siberia.
6. Weinstein states......it may be that the combination of the two (or more) volcanoes, along with Solar variability and variations in ocean currents (i.e., PDO) may explain the major causes of recent surface temperature rises to about 2002. In fact, the average Earth temperature stopped rising after 2002, and has been dropping for the last few years!
Mt. Pinatubo caused a period of cooling, not warming in the early 1990's. Weinstein also fails to mention the recent La Nina (late 2007/2008), which almost certainly had a role in the recent short term period of cooling. Also, depending on the source, the most recent period of global cooling was was less than two years in length and now appears to be creeping back up again in 2009, especially now that the most recent La Nina is officially dead.
7. Weinstein states....While some overall trends can be reasonably made based on looking at past historical trends, and some computational models can suggest some suggested trends due to specific forcing factors, nevertheless, the long term predicted result has not been shown to be valid.
Our overall assessment (IPCC)........
Coupled models have evolved and improved significantly since the SAR. In general, they provide credible simulations of climate, at least down to sub-continental scales and over temporal scales from seasonal to decadal. The varying sets of strengths and weaknesses that models display lead us to conclude that no single model can be considered "best" and it is important to utilize results from a range of coupled models. We consider coupled models, as a class, to be suitable tools to provide useful projections of future climates. Intergovernmental Panel on Climate Change
8. Weinstein states.....The overall effect of Antarctic and Greenland are now resulting in net gain (or at least near zero change) of ice, not loss.
ScienceDaily (Feb. 25, 2009) â€” The Greenland and Antarctica ice sheets are melting, but the amounts that will melt and the time it will take are still unknown, according to Richard Alley, Evan Pugh professor of geosciences, Penn State.
Seems like more controversy.
Bio courtesy of Energy Probe.
Leonard Weinstein received a B.S. in Physics in 1962 from Florida State University. He started work at NASA Langley Research Center in June 1962. While at Langley, Leonard obtained his Master and Doctor of Science degrees in Engineering from the George Washington University. He continued to work at NASA Langley until June 2007, ending as a Senior Research Scientist. Dr. Weinstein is presently a Senior Research Fellow at the National Institute of Aerospace.