They described a "global dimming" in particular over south and east Asia, South America, Australia and Africa, while visibility remained relatively stable over North America and improved over Europe, the researchers said.
Aerosols, tiny particles or liquid droplets belched into the air by the burning of fossil fuels and other sources, are responsible for the dimming, the researchers said.
Human pollution is turning the seas into acid so quickly that the coming decades will recreate conditions not seen on Earth since the time of the dinosaurs, scientists warned.
The rapid acidification is caused by the massive amounts of carbon dioxide belched from chimneys and exhausts that dissolve in the ocean. The chemical change is placing "unprecedented" pressure on marine life such as shellfish and lobsters and could cause widespread extinctions, the experts say.
Global warming pushes extremes. It prolongs drought while sometimes bringing deluges the parched earth cannot absorb. California Department of Water Resources Director Lester Snow says two things keep him up at night: drought and flood.
"It isn't that drought is the new norm," said Snow. "Climate change is bringing us higher highs and lower lows in terms of water supplies."
Climate change is already having an impact on European bird species, according to British scientists.
Details of the study by an international team of researchers have been published in the journal Plos One.
Some birds are expected to do well as temperatures rise, but these are in the minority, the researchers write.
"Overall, the trend is towards net loss," said a spokesman for the Royal Society for the Protection of Birds (RSPB), which contributed to the study.
The researchers found birds that are expected to do well as temperatures rise had indeed increased in number since the 1980s.
But some 75% of species studied by the researchers had declined in the same period.
