Reproduced below is a paper, published in the March 16 edition of the
prestigious magazine Science, which argues that based on at least one
set of satellite data (AVHRR), the sun, not man-made CO2, is
responsible for the global warming 'jump' seen in the last 15 years.

The paper is a bit hard to follow for non-specialists, but essentially
it is arguing that once you strip away the aerosol sun-blocking
effects of two volcanic eruptions in ~1982 (El Chichon) and ~1992
(Pinatubo), you get a trend line that indicates the sun is shining
brighter than before on the surface of the earth.  The aerosols were
blocking the sun, and once the aerosols were removed, the sun shined
through stronger than before.

The implication is that it's not man-made greenhouse gases that caused
the jump in temperatures since 1990, but less aerosols in the air
(dust, pollution like SOx, etc).

BTW this does not mean there's no global warming caused by man--there
seems to be a steady increase over the long term that suggests man is
responsible--but rather, it does suggest that the 'jump' in
temperatures in recent decades, which is what the Greens get hot under
the collar about, has been caused by fewer aerosols, not more CO2.
This is obviously good news for fossil fuel burning countries,
especially the USA which burns a lot more CO2 producing fuels like
coal than other countries, such as France (which uses more nuclear
energy instead).

Since the article was scanned into text the figure could not be
introduced.

RL

Science Vol. 315 16 March 2007
Long-Term Satellite Record Reveals Likely Recent Aerosol Trend
Michael I. Mishchenko,* Igor V. Geogdzhayev, William B. Rossow, Brian
Cairns, Barbara E. Carlson, Andrew A. Lads, Li Liu, Larry D. Travis

Recent observations of downward solar radiation fluxes at Earth's
surface have shown a recovery from the previous decline known as
global "dimming" (1), with the 'brightening" beginning around 1990
(2). The increasing amount of sunlight at the surface profoundly
affects climate and may represent certain diminished counterbalances
to greenhouse gas warming, thereby
making the warming trend more evident during the past decade.
It has been suggested that tropospheric aerosols have contributed
notably to the switch from solar dimming to brightening via both
direct and indirect aerosol effects (1, 2). It has further been
argued
(3) that the solar radiation trend mirrors the estimated recent trend
in primary anthropogenic emissions of SO2 and black carbon, which
contribute substantially to the global aerosol optical thickness
(AOT). A similar increase of net solar flux at the top of the
atmosphere (TOA) over the same period appears to be explained by
corresponding changes in lower latitude cloudiness (4), which
confounds the interpretation of the surface radiation record.
Therefore, it is important to provide a direct and independent
assessment of the actual global long-term behavior of the AOT. We
accomplish this by using the longest uninterrupted record of global
satellite estimates of the column AOT over the oceans, the Global
Aerosol Climatology Project (GACP) record (5). The record is derived
from the
International Satellite Cloud Climatology Project (ISCCP) DX radiance
data set composed of calibrated and sampled Advanced Very High
Resolution Radiometer (AVHRR) radiances. A detailed discussion of the
sampling resolution, calibration history, and changes in the
corresponding satellite sensors can be found in
(6).
The global monthly average of the column AOT is depicted for the
period August 1981 to June 2005 (Fig. 1, solid black curve). The two
major maxima are caused by the stratospheric aerosols generated by
the
El Chichon (March 1982) and the Mount Pinatubo (June 1991) eruptions,
also captured in the Stratospheric Aerosol and Gas Experiment (SAGE)
stratospheric AOT record (7). The quasi-periodic oscillations in the
black curve are the result of short-term aerosol variability.
The overall behavior of the column AOT during the eruption-tree
period
from January 1986 to June 1991 (Fig. 1, red line) shows only a hint
of
a statistically significant tendency and indicates that the average
column AOT value just before the Mount Pinatubo eruption was close to
0.142. After the eruption, the GACP curve is a superposition of the
complex volcanic and tropospheric AOT temporal variations. However,
the green line reveals a long-term decreasing tendency in the
tropospheric AOT. Indeed, even if we assume that the stratospheric
AOT
just before the eruption was as large as 0.007 and that by June 2005
the stratospheric AOT became essentially zero (compare with the blue
curve), still the resulting decrease in the tropospheric AOT during
the 14-year period comes out to be 0:03. This trend is
significant at the 99% confidence level.
Admittedly, AVHRR is not an instrument designed for accurate aerosol
retrievals from space. Among the remaining uncertainties is radiance
calibration, which, if inaccurate, can result in spurious aerosol
tendencies. Similarly, substantial systematic changes in the aerosol
single scattering albedo or the ocean reflectance can be
misinterpreted in terms of AOT variations. However, the successful
validation of GACP retrievals
using precise sun photometer data taken from 1983 through 2004 (8, 9)
indicates that the ISCCP radiance calibration is likely to be
reliable. This conclusion is reinforced by the close correspondence
of
calculated and observed TOA solar fluxes (4). Furthermore, the GACP
AOT record appears to be self-consistent, with no drastic
intrasatellite variations, and is consistent with the SAGE record.
The advantage of the AVHRR data set over the data sets collected with
more advanced recent satellite instruments is its duration, which
makes possible reliable detection of statistically significant
tendencies like the substantial de¬
crease of the tropospheric AOT between 1991
and 2005. With all the uncertainties, the troposphere AOT decrease
over the 14-year period is estimated to be at least 0.02. This change
is consistent with long-term atmospheric transmission records
collected in the former Soviet Union (5).
Our results suggest that "the recent downward trend in the
tropospheric AOT may have contributed to the concurrent upward trend
in surface solar fluxes. Neither AVHRR nor other existing satellite
instruments can be used to determine unequivocally whether the recent
AOT trend is due to long-term global changes in natural or
anthropogenic aerosols. This discrimination would be facilitated by
an
instrument like the Aerosol Polarimetry Sensor (APS), scheduled for
launch in December 2008 as part of the NASA Glory
mission (10). It is thus imperative to provide uninterrupted
multidecadal monitoring of aerosols from space with dedicated
instruments like APS in order to detect long-term anthropogenic
trends
potentially having a strong impact on climate.
References and Notes
1. 2. R. T. Pinker, B. Zhang, E. G. Dutton, Science 308, 850
        (2005).
        3. D. G. Streets, Y. Wu, M. Chin, Geophys. Res. Let!. 33,
        L1S806 (2006).
        4. Y. Zhang, W. B. Rossow, A. A. Lacis, V. Oinas,
        M. I. Mishchenko,]. Geophys. Res. 109, Dl910S (2004).
        5. I. V. Geogdzhayev, M. I. Mishchenko, E. I. Terez,
        G. A. Terez, G. K. Gushchin,]. Geaphys. Res. 110,
        D2320S (2005); and references. therein.
6. W. B. Rossow, R. A. Schiffer, Bull. Am. Meteorol. Soe. 80,
        2261 (1999); and references therein.
        7. ]. Hansen et al.,]. Geophys. Res. 107, 4347 (2002).
8. L. Liu et al.,]. Quant. Spectrase. Radiat. Tronsfer 88, 97
        (2004).
9. A. Smirnov et aI., Geophys. Res. Lett. 33, L14817
        (2006).
10. M. I. Mishchenko et al.,]. Quant. Spectrose. Radiat.
        Transfer 88,149 (2004).
11. This research is part of NASA/Global Energy and Water Cycle
Experiment GACP and was funded by the NASA Radiation Sciences
Program,
managed by H. Maring and D. Anderson.
24 October 2006; accepted 20 December 2006 10.1126/science.1136709