Vigorous debate is good. It forces the debaters to carefully evaluate their positions and, if honest debate is sustained, to re-evaluate their positions, conceding points well made. It encourages analytical thinking and fact gathering such that both serve to bring about truth. If only the promoters of chemtrails would engage in an honest debate, the issue would be much further along towards a resolution than it is.
In the spirit of debate, my conclusions in this thread were well challenged by GeorgeB in another thread
here.
GeorgeB's contention as a "chemtrails advocate", laid out
here, is that a covert aerosol program could be ongoing if certain assumptions are made, though he has no direct evidence for it. My position is that the data, specifically solar transmission measurements, do not show the solar transmission decreases which would be expected if such a program were underway. My position is laid out above in this thread.
As a result of George's counterclaim in the other thread, I must admit that, even though it is not clear to me in the graph I posted above, some data in this paper does show that solar transmission declined between 2000 and 2009, which
the paper does attribute to sulfur releases from coal burning increases by the world's largest CO2 emitter, China, and
another paper says were also likely due to smaller volcanic eruptions.
I was confounded, yet determined to learn more about the facts of the matter. I did further research, first looking at the Mauna Loa website at the most recent transmission data here:
To me, this data doesn't show a clear decline, which is probably due to the long-term nature of the 50 year representation. The data is "time sensitive" to a negative degree. For example, consider you were on a road trip through the mountains, and at the end calculated your average speed at 40 miles/hour. In actuality, however, during parts of the trip you were headed uphill and your speed might have decreased, and at times headed downhill at much greater speed.
What was needed is a greater resolution, and I believe I have found it. One month before last, in July 2012, the Bulletin of the American Meteorological Society (BAMS) produced
The State of the Climate in 2011, containing the most recent review of climate data available. Here is the section on solar atmospheric transmission:
BAMS said:
SIDEBAR 2.3: LONG-TERM CHANGES OF ATMOSPHERIC SOLAR
TRANSMISSION—E. DUTTON
Both the solar and thermal infrared transmission of the atmosphere play important roles in Earth's energy balance. For example, the anticipated long-term worldwide decrease in infrared atmospheric transmission, due to increasing greenhouse gas abundance, gives rise to the issues and concerns of global warming. Similarly, long-term increases in the solar transmission would contribute to warming, while a decrease would have the opposite effect. While considerable attention and effort has gone into observations necessary to track and understand the long-term global background of the atmospheric infrared transmission, relatively few similar records of the solar transmission exist.
One of the longest, continuous observational records of solar transmission through the free troposphere and above is maintained by NOAA at the Mauna Loa observatory in Hawaii (Dutton and Bodhaine 2001). This consists of qualified daily and monthly averages of clear-sky morning "apparent" solar transmission obtained from pyrheliometer observations by the methodology first described by Ellis and Pueschel (1971). The "apparent" is an optical term applied to the solar transmission values used here because they are determined from ratios of direct beam solar irradiances observed at different solar zenith angles (atmospheric paths) such that the computed transmission is relative to the irradiance already transmitted along the shorter path. The irradiance is measured with a calibrated pyrheliometer. The linear calibration factor cancels out in the apparent transmission ratio, yielding a more accurate and stable result.
This measure of solar transmission is particularly sensitive to aerosols. The computational procedure diminishes the effect of water vapor, which is the other major contributor to variable clear-sky solar transmission, due to saturation effects. There is also a minor ozone contribution, although this is not significant on the scale of the variations seen. Spectral aerosol optical depth is also observed (sun photometer) at the site and confirms the primary aerosol role in current observed solar transmission variability. Although only a single site, Mauna Loa can be considered representative of a much larger portion of the Earth because of its remote central Pacific location and high elevation, above most local effects, especially in the early morning during downslope-wind conditions when daily transmission measurements are made.
The complete apparent transmission (AT) record (Fig. SB2.7a) shows the extended impact of three major explosive volcanic eruptions (Agung, 1964; El Chichón, 1982; and Pinatubo, 1991). These injected large quantities of sulfur dioxide (SO2) into the stratosphere, where it was converted to sulfate aerosol and remained for many months while spreading around the world. A certain amount of month-to-month variability and a small amplitude (~0.007 AT) annual cycle (spring minimum, winter maximum) persisting throughout much of the record are also seen. This annual cycle has been attributed to the seasonally
enhanced transport of Asian tropospheric aerosol over the site (Bodhaine et al. 1981). Not so apparent in the record are potential variations in the overall background transmission, which have the most enduring effects. Examination of the last decade (Fig. SB2.7b) and other information by Solomon et al. (2011) has shown a small net downward tendency, possibly due to multiple periods of injection of stratospheric aerosols. Figure S2.7b suggests a general decrease of about 0.003 AT occurring between 1998 and 2010. This trend is also seen in collocated spectral aerosol optical depth measurements. However, the downturn appears to have ended in the last 2–3 years. Currently, it is not possible to discern a continuing coherent long-term behavior in the record, but the 55-year AT record permits putting the current variability into historical context.
Using these and other data, Solomon et al. (2011) computed that the decline in transmission (or equivalently, an increase in AOD) from the late 1990s to 2010 was sufficient to reduce tropospheric warming by about 0.07°C compared to a scenario with a relatively "clean" stratosphere, as was previously widely used in global climate models for that decade. The source of the general decrease in solar transmission is suspected to be several small, largely unnoticed, volcanic eruptions that together have increased the stratospheric component of the total column aerosol over a large portion of the globe (Vernier et al. 2011).
The graph, which includes my previously referenced Mauna Loa Clear-sky solar transmission (a), also shows a high resolution version covering the more recent period (b).
Using this higher resolution dataset, you can now discern that solar transmission has gone through a complete cycle from greater to less, and during the past three years is basically back where it started. There is corroborating data in the colored CALIPSO aerosol chart above showing good reason to suspect the volcanoes were the source of decreased transmission through 2009, but that effect has now gone away and transmission has returned to the same state it was in at the time George claims that geoengineering was taking place.
This data shows that though some changes in optical transmission have occurred during the decade in which claims have been made that there was ongoing geoengineering, that trend has reversed and transmission has since recovered to its previous state.
It is significant that during the time of the last three years, as solar transmission has recovered after being perturbed by the volcanoes, this recovery occurred amidst an unabated continuation of the same "chemtrails" being reported worldwide. Thus, there is no correlation seen between the observation of purported geoengineering "chemtrails" and any decline in solar transmission.
