Question

when was environmental pollution became a global problem?

Answer 1

It depends on what you mean by 'pollution' and 'problem.'

The climate has long been influenced by terrestrial forces - for example, the Atlantic Multidecadal Oscillation (a major driver of long term climate change in North Africa, Europe and North America) has lately been linked to aerosol released from volcano eruptions before man made aerosols started influencing it too.

People started observing *ecological* changes a couple decades after the start of the Industrial Revolution - for example, they started noticing that dark moths were less visible on pollution covered trees than white moths, so dark moths are more successful at passing on their genes and after a few generations almost all moths were dark.

Climate changes took a while longer to be noticed. One reason is that climatology was not a rigorous or widely accepted scientific field until the 1970s, when there was a lot of public interest in it - so the computational tools and the data sets to actually quantify climate change were not available.

A lot of climatologists currently believe that man started having measurable effect on global climate in the mid or late 19th century, so a couple decades after the Industrial Revolution got under way. But it was small - these days they are more concerned by the rate of increase in that effect.

I have attached the famous hockey stick graph because it is possibly the most important figure in any scientific paper in the last decade.