Global warming: caused by aerosols?

What is the main effect on global warming?
Michael Asher (DailyTech.com) on a new research - influence of aerosols on European climate. (link)

A new study suggests much of that warming isn't due to global warming at all, but rather a decrease in atmospheric pollution as a result of clean air legislation. The cleaner air has fewer small particles known as aerosols, which tend to block sunlight from reaching the Earth's surface. A reduction in aerosols leads to an effect known as "solar brightening," which increases surface warming.

Citation: Ruckstuhl, C., et al. (2008), Aerosol and cloud effects on solar brightening and the recent rapid warming, Geophys. Res. Lett., 35, L12708, doi:10.1029/2008GL034228. (link)

Abstract

The rapid temperature increase of 1°C over mainland Europe since 1980 is considerably larger than the temperature rise expected from anthropogenic greenhouse gas increases. Here we present aerosol optical depth measurements from six specific locations and surface irradiance measurements from a large number of radiation sites in Northern Germany and Switzerland. The measurements show a decline in aerosol concentration of up to 60%, which have led to a statistically significant increase of solar irradiance under cloud-free skies since the 1980s. The measurements confirm solar brightening and show that the direct aerosol effect had an approximately five times larger impact on climate forcing than the indirect aerosol and other cloud effects. The overall aerosol and cloud induced surface climate forcing is ∼+1 W m⁻² dec⁻¹ and has most probably strongly contributed to the recent rapid warming in Europe.