SOON AND BRIGGS: Global-warming fanatics take note – Sunspots do impact climate

Leif Svalgaard says: September 11, 2012 at 10:57 pm
The whole issue is too complex to deal with in a comment, but from past discussions with Signe my understanding is that both natural dynamics and anthropogenic influence play a role.
That seems like a reasonable possibility to me.
The situation is like with climate change: each camp claims that their mechanism is the only [or at least dominant] cause, and the discussion quickly degrades into polarized name-calling.
Strange how “science” works these days…
The timing of the beginning of the long, slow recovery suggests to me that the ban on some man-made halocarbon refrigerants has been working.
I am skeptical of the evidence of “recovery” as I have limited confidence in the atmospheric ozone content measurements/calculations, e.g.;

“Nimbus-7 TOMS Instrument and Satellite Information
The TOMS program began with the launch of TOMS Flight Model #1 on the Nimbus-7 spacecraft on October 24, 1978. Valid measurements started in November of that same year and the instrument continued to return data long after all other on-board experiments had failed. The TOMS instrument fell silent in May 1993. The software to derive useful information from the data returned by Nimbus 7 TOMS is the basis for the algorithm used to analyze all TOMS data and has gone through a lengthy evolutionary process bring it to the current version. The Version 7 processed data include a revised instrument calibration based on analysis of the entire 14.5 year data record (including a correction for a 0.2 nm wavelength error which caused a 3% absolute offset relative to Dobson) as well as an improved algorithm.
Algorithmic Improvements include:
use of wavelength “triplets” that correct for errors linear in wavelength
improved ISCCP cloud height climatology, higher resolution terrain height maps
use of improved profile shape selection to improve total ozone at very large solar zenith angles
use of a more accurate model for partially-clouded scenes improved radiative transfer calculations for table generation”
http://toms.gsfc.nasa.gov/n7toms/n7sat.html

In order to fulfil the demand in data quality required for reliable long-term trend analysis a network was designed during the 1970s which runs under the auspices of the World Meteorological Organization (WMO) (e.g. Staehelin, 2008, Dlugokencky et al., 2010). It includes regular intercomparisons between station and standard instruments (see Section 3). The network was first named Global Ozone Monitoring System (GO3S) which was subsequently integrated in Global Atmosphere Watch (GAW). Since 1979 the global ozone shield is measured from space which allows (quasi) global and (quasi) continuous monitoring of the ozone layer. However, it become clear in the 1980s that it is very important to complement the global monitoring by satellite instruments with ground based measurements, because the long-term stability of ground based instruments can be more easily controlled than instruments operated onboard of satellites (e.g. Heath et al., 1988; WMO, 1989).http://www.wmo.int/pages/prog/www/IMOP/publications/IOM-104_TECO-2010/1_3_Stahelin_Switzerland.pdf

NASA Ozone Data Source:
The data for 1979–1993 are from the TOMS instrument on the NASA/NOAA Nimbus-7 satellite.
The data for this 1993–1994 are from the TOMS instrument on the Soviet-built Meteor-3 satellite. The data for 1996–October 2004 are from the NASA Earth Probe TOMS satellite.
The data for November 2004–2011 are from the OMI instrument (KNMI / NASA) onboard the Aura satellite. They are the OMTO3 that have been processed in a manner similar to the TOMS data from earlier years.
The ozone minimum is determined only from data actually contained in the processed satellite data. To calculate the ozone hole area and mass deficit, we fill in missing areas (bad orbits and polar night) from an atmospheric model. MERRA is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5). The Project focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales and places the NASA EOS suite of observations in a climate context. Since these data are from a reanalysis, they are not up-to-date. So, we supplement with the GEOS-5 FP data that are also produced by the GEOS-5 model in near real time.”
http://ozonewatch.gsfc.nasa.gov/meteorology/ozone_1990_MERRA_SH.html

“08-15-2007
Corrected Earth Probe Data
correction basis: NOAA-16 SBUV/2 ozone
time period: August 1996 – December 13, 2005
data products corrected: ozone, reflectivity
By mid-2000, the Earth Probe (EP) TOMS instrument degradation became so large that standard correction procedures could no longer produce accurate ozone. The problem is believed to be inhomogeneous degradation of the scanner mirror on TOMS that results in a calibration error that is different at different latitudes. We have warned users that the production EP ozone data should NOT be used for trend analysis.
We have now applied a correction to the Earth Probe data that stabilizes the EP ozone record. This empirical correction is based on the NOAA-16 SBUV/2 ozone record, with a solar zenith angle dependence that accounts for much of the spurious latitude dependence observed in the current data. Only the ozone and reflectivity records have been corrected. The aerosol index data and SO2 records are more complex and have not been corrected by this empirical correction.
Comparison with the ground network shows that the resulting ozone is stable within ± 1% over the 1996-2005 period. In the period 2002-2005 in the northern hemisphere, there is a residual seasonally-dependent error of ± 1.5% magnitude. These data should still NOT be used as a source for trend analysis since they are no longer independent.”
http://ozoneaq.gsfc.nasa.gov/news.md

So “long after all other on-board experiments had failed” it produced suspect data, which was then put through “a lengthly evolutionary process” that includes “revised instrument calibration”, “including a correction for a 0.2 nm wavelength error”, “as well as an improved algorithm” that included “a more accurate model for partially-clouded scenes” and “to calculate ozone hole area and mass deficit” they “fill in missing areas (bad orbits and polar night) from an atmospheric model.” It seems that the TOMS instrument has a long history of issues and required “corrections”, thus the resultant Ozone content measurements/calculations should be viewed with a skeptical eye.
Prior to the TOMS measurements, the accuracy of ground based measurements was likely significantly worse, e.g.;

Statistical analyses of ground-based total-column ozone measurements show that between 1970 and 1980 there was no statistically significant decrease in the annual global average content of ozone (i.e. the decrease was less than 1 per cent). Model calculations, taking into account increases in carbon dioxide, methane, nitrous oxide and halocarbons, predicted that total-column ozone should have decreased by less than 0.5 per cent at all latitudes in the summer and between 0.5 and 1 per cent in the winter, with the largest depletions predicted at high latitudes. Thus the model results are not inconsistent with the observations.
Estimates of trends in the vertical distribution of ozone, using ground-based data, suggest that ozone decreased in the middle and upper stratosphere by 23 per cent in the period 1970 to 1980. While this data base is limited, both in number of stations and data quality,the trends are consistent with model predictions. http://www.ciesin.org/docs/011-466/011-466.html

At the beginning of the 1970s ozone destruction by anthropogenic emissions started to be discussed in science and public. Molina and Rowland (1974) showed that chlorofluorocarbons (CFCs) anthropogenically emitted at the Earth’s surface can reach the upper stratosphere, where they can destroy stratospheric ozone after photolysis. This caused a change in paradigm of stratospheric ozone research: In the previous period stratospheric ozone measurements were performed for scientific purposes (e.g. to determine the climatology and to study the relation between meteorology and stratospheric ozone) and therefore the requirement in precision and accuracy were comparatively low because total ozone can change from one to another day up to 30% at mid-latitudes. Long-term changes in the ozone layer become a new topic in the debate of the anthropogenic destruction of the ozone layer particularly since the theory of Molina and Rowland (1974) was challenged by industry manufacturing ODS. However, it turned out that the network of earlier total ozone measurements did not fulfil the data quality requirements to be used for long-term trend analysis (note that the downward trend in total ozone caused by ODS at mid-latitudes never exceeded more than a few percent decrease per decade (see e.g. WMO, 1989); this implies that only a few data series going back in time prior to the 1970s can be used for long-term analysis after careful homogenization, see e.g. Figure 1).http://www.wmo.int/pages/prog/www/IMOP/publications/IOM-104_TECO-2010/1_3_Stahelin_Switzerland.pdf

The historical ground-based total ozone observations in October show that the depletion started in the late 1970s, reached a maximum in the early 1990s and stabilised afterwards due to saturation. There is no indication of ozone recovery yet. At southern mid-latitudes, a reduction of 20– 50% is observed for a few days in October–November at the newly installed Rio Gallegos station. Similar depletion of ozone is also observed episodically during the vortex overpasses at Kerguelen in October–November and at Macquarie Island in July–August of the recent winters. This illustrates the significance of measurements at the edges of Antarctica. http://www.atmos-chem-phys.net/10/6569/2010/acp-10-6569-2010.pdf

Measurement of ozone content within a swirling Polar Vortex;
http://www.jhu.edu/~dwaugh1/gallery_stratosphere.html
from a few ground stations, that were not far from the coast of Antarctica, does not provide confidence in the measurement accuracy.
It thus perplexing that this questionable evidence was sufficient to support attribution to and action against anthropogenic CFC emissions, i.e.:

In 1985 the Antarctic ozone hole was first reported (Farman et al., 1985). Observations of total-column ozone, using a ground-based spectrophotometer at Halley Bay, showed that the October level of ozone decreased from a value of typically 300 Dobson Units (DU) during the 1960s and early 1970s to about 200 DU in the early 1980s (Figure 6). This decrease of about 30-40 per cent in a decade was totally unexpected. Satellite data (Plates I and II. between pages 52 and 53) showed the spatial extent of the depletion. and balloonsonde data (Figure 7) showed that it occurred in the lower stratosphere. By 1986 three mechanisms (two involving changes in natural processes (1 and 2) and one involving human activities (3)) had been proposed to explain the observations of ozone loss:
solar cycle mechanism: periodic increases in the abundance of nitrogen oxides in the lower Antarctic stratosphere due to variations in solar output:
dynamical mechanism: a change in the circulation pattern from downwelling of ozone-rich air from the upper stratosphere to upwelling of ozone-poor air from the troposphere; and
halogen mechanisms: several different theories invoking the catalytic destruction of ozone due to CFCs and halons.
A ground-based study based at McMurdo, Antarctica, in 1986 showed that:
the abundances of nitrogen oxides were exceptionally low, which largely disproved the solar cycle mechanism:
the levels of long-lived tracers were such that a dynamical mechanism was unlikely: and
the elevated levels of active chlorine species suggested that chlorine catalysis was the most probable mechanism.
At the time that the Montreal Protocol was signed in September 1987, the cause of the Antarctic ozone hole was not well established. However, the scientific synthesis upon which the Protocol was based provided convincing evidence that the stratosphere had become perturbed:
the levels of atmospheric chlorine were increasing at about 4-5 per cent per year because of the emissions of chlorofluorocarbons;
theoretical models predicted a chlorine-induced ozone loss, primarily in the upper stratosphere between 30km and 45km;
there was limited observational evidence of ozone loss near 40km; and
a significant loss of ozone was occurring every October above Antarctica, even though its cause had not been conclusively established. http://www.ciesin.org/docs/011-466/011-466.html

No significant conclusions, just a bunch of data and various reasons for healthy skepticism.