Can someone who voted for the 30/12/0 years options please make their case in the comments? I hate being an "anti-science" guy, but I genuinely don't understand what the science is telling us here. You've got people like Biden saying we've got until 2050, Cortez is saying we have until 2030, and Andrew Yang is telling everyone that it's already too late and we need to head for the hills. I've studied climate change at my university but we only really delved into the causes (and how we know it's caused by us), not the timetable it's operating on. I have to say, it looks pretty stupid when multiple candidates say "I believe the science" and then they all offer up completely different interpretations for what the science is telling us.
I think the underlying idea here is "if we do X, then there's a Y% chance Z happens". I haven't paid too close attention to the debates or who's been saying what, but it sounds like Biden is saying that we need to accomplish ABC and XYZ by 2050 in order to stay within 2 C of warming, while Ocasio-Cortez is like "we have until 2030 to get to zero emissions or else we have no chance of staying within 2 C".
Yang seems to be focusing more on adapting to a changing climate, partly because the structural changes we would need to make in order to reach a +2 C world are at best mildly unrealistic, but more importantly because we've already locked in a certain amount of long-term climate change with the amount of greenhouse gases we've already put into the atmosphere. Even if we were to magically stop all CO2 emissions tomorrow, and atmospheric CO2 levels stayed constant for the next several hundred years- we would still be experiencing more heat waves, floods, droughts, and extreme weather than we did in the past. So there would still be some level of change to adapt to.