A concern that's been in the back of mind for a while is, what if plastic isn't as long lasting as we think? To put another way, what is the carbon footprint of microorganisms evolving to eat it? Are we looking at another carbon bomb?
That's without looking at estimates of plastic production, but it's likely enough to be higher now than the majority of the 70 years.
It's an exponential curve. Most plastic made was made relatively recently. This is less obvious in the first world, where we've had consumer plastics for many decades. Most growth in plastic use happens outside the US.
Conversely, I don't know if that number includes production from natural gas and not just crude oil, and a lot of plastic feedstock is made from it.
Edit: > Direct methane emissions released to the atmosphere (without burning) are about 25 times more powerful than CO2 in terms of their warming effect on the atmosphere.
https://www.epa.gov/energy/greenhouse-gases-equivalencies-ca...
Then just plant some trees to convert co2 into wood, then cut down the trees, make furniture, then dump furniture into oceans to make new oil.
The circle of oil!
Therefore what plastic makes it into the oceans represents a small fraction of the total carbon emissions.
Besides, it appears to take a very long time to decay, significantly reducing the GHG potential of plastic