I doubt that 1600 tonnes is accurate.

According to my quick search, Bill G has a G650, which has a cruising speed of 590 mph.

So 213,000 / 590 = 361 hours of flight.

According to this site he's looking at 1932 tonnes.

To give you an idea, the average American outputs around 4.5 tonnes of CO2 per year while driving. Which would basically mean that it would take about 430 years of an average person driving to make up what Bill G put out in a year of flying.

Now also remember that not only does he have who knows how many houses, but his houses are fricking HUGE. His Seattle mansion alone is 66,000 square feet. And last I checked the weather in Seattle sucked year round, so imagine how much it takes to heat that place year round.