Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth's surface that was observed for several decades after the start of systematic measurements in 1950s. It is thought to have been caused by an increase in particulates such as black carbon in the atmosphere due to human action. The effect varied by location, but worldwide it was of the order of a 4% reduction over the three decades from 1960–1990. The trend reversed during the past decade. Global dimming has interfered with the hydrological cycle by reducing evaporation and may have caused droughts in some areas. Global dimming also creates a cooling effect that may have partially masked the effect of greenhouse gases on global warming.

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Global Dimming

Long story short: Pollution has 2 effects, a warming effect via
CO2 and a cooling effect (global dimming) caused by particles in the air which block the sunlight out. (smoke, ashes, soot etc.)
The easiest environmental measures have a bigger effect on the particles so the temparature has rissen lately.
Interesting detail: on the days after 11 sept., the temparature in the usa rose sharply with one degree celsius, cause of flight-suspension. When flights resumed it dropped to its normal levels.
Still, on average apperently, the warming effect is larger than the cooling effect. If we do nothing, then we'll end up with a slightly warmer world, where it will be extremely hard to breathe.
In such a world, two expressions will dissappear from human speech: "As free as air" and "Only the sun shines for naught".

Perhaps we could paint the Earth white, see here.

Interesting: Global Dimming reduces global warming in the short term but increases global warming in the long term. Aerosols reduce photosynthesis in plankton and plants leaving long-term CO2 in the atmosphere.