417 & counting ...

417 & counting ... is exactly what the interactive Bloomberg Carbon Clock is doing, something most disquieting as the increase in carbon, along with methane, have been the prime drivers for all of the mass extinctions of earth beginning over 700+ million years ago.

Why this number

Carbon dioxide pollution from humans—mostly burning fossil fuels and clearing forests—is the main driver of global warming. Not all of the CO2 that people emit ends up lingering in the atmosphere. About a quarter is absorbed by oceans, and another quarter is taken up by plants. The rest remains, and that running tally of atmospheric carbon dioxide has been fundamental to the discovery and monitoring of climate change. The number above means CO2 now makes up 0.0417% of the planet’s overall atmospheric volume, more than 49% higher than before industrialization. Geologic evidence suggests that the earth’s CO2 was last at this level approximately 3 million years ago—an era when the world was 2°C or 3°C warmer and the oceans may have been more than 65 feet higher.

Bringing it back to 350 will take time, lots and lots of time, which we don't have ...

What progress looks like

The carbon clock will be a lagging indicator of progress. If new greenhouse-gas emissions ended tomorrow, CO2 in the atmosphere would begin washing into the ocean, rolling the parts-per-million count backwards outside of the seasonal up-down cycle. This would start a very long process. Getting it back to pre-industrial levels would take thousands of years—unless we deploy technologies that can suck up vast quantities of CO2 from the air.

Thus far, nothing has been done and, from this perspective, the chances of massive tech soaking up the excess carbon is questionable at best. Dimming the sun's light is another boondoggle as well IMHO.

Remember, we did this to ourselves.