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." The you may draw your own conclusions using a more recent study 2012...
http://www.atmos-chem-phys.net/12/8777/2012/acp-12-8777-2012.html which concludes: "...
Therefore, the aerosol impacts on precipitation are amplified by the positive feedback of precipitation on aerosol, which ultimately alters the cloud micro- and macro-physical properties, leading to strong aerosol-cloud-precipitation interactions. The high sensitivity is also related to an increase in cloud-top entrainment rate (by 16% at night) due to the increased anthropogenic aerosols. The simulated aerosol-cloud-precipitation interactions due to the increased anthropogenic aerosols have a stronger diurnal cycle over the clean region compared to the near-coast region with stronger interactions at night. During the day, solar heating results in more frequent decoupling of the cloud and sub-cloud layers, thinner clouds, reduced precipitation, and reduced sensitivity to the increase in anthropogenic emissions. This study shows the importance of natural aerosols in accurately quantifying anthropogenic forcing within a regional modeling framework. The results of this study also imply that the energy balance perturbations from increased anthropogenic emissions are larger in the more susceptible clean environment than in already polluted environment and are larger than possible from the first indirect effect alone." It is important to check the evidence provided pro and against the GeoEngineering Phenomena.