[cropsieboss]

Most CO2 is indeed natural.

We did increase the circulating amount by a very small margin. Large enough so that it accumulated over the years.

This of course led to a feedback loop.

Arctic ice has 1400Gt of carbon locked up as methane. [1] This is equivalent to 1400/10 = 140 years of human 2016 activity. [2] If ice starts to melt, we are doomed.

[1]: https://en.wikipedia.org/wiki/Arctic_methane_emissions

[2]: https://www.co2.earth/global-co2-emissions

[specialist]

I believe (but cannot prove, obviously) that we're way past the tipping point. Meaning simply reducing anthropocentric emissions, even down to zero, will not meaningfully impact atomspheric CO2, methane.

For civilization to survive, we must adapt, mitigate, or both.

[stale2002]

The scientific consensus is that sea levels will rise by 1-2 meters over the course of 200 years.

Thats the science. And it doesn't sound like extinction to me.

[mark-r]

Sea levels aren't the only source of trouble. Changing rainfall amounts for example would impact our ability to grow crops.

Yes, extinction seems unlikely. But the planet's ability to support the current population could easily be a casualty.

[brazzledazzle]

I think the concern is that the models in use don't take these additional feedback loops into consideration because they're difficult to predict.

[pier25]

> If ice starts to melt, we are doomed.

It's already happening. Natalia Shakhova has been studying this for years.

https://www.youtube.com/watch?v=iSsPHytEnJM

[graeme]

Yup. That's what's terrifying. Most current talk about CO2 assumes that humans will have control over how much is released.

But since we pushed the system to a new state, its net emissions may dwarf our own emissions. Then things get even harder.