The lowest one is "if we soon stop using the fossil fuels completely" which is not going to happen.

And to those who don't believe:

It is caused by humans: see the energy used in the last 200 years:

https://gailtheactuary.files.wordpress.com/2012/03/world-ene...

And see what it means that the "climate changed before":

https://xkcd.com/1732/

The principle the warming works is the same why you wear a coat in the winter: the coat keeps the surface temperature of your body warmer, even if the coat itself doesn't produce a new heat. A thick coat keeps you warmer than a thin one. More CO2 does the same to the Earth surface. Without the greenhouse gases the average Earth temperature would be 0°F (or -18°C) and it is 59°F (15°C). And "a few degrees more" is really a lot and awfully fast, see the xkcd drawing again.

That's called the "wishful thinking" fallacy, to which you cling to confirm your previous "investment." If we'd look at your sources of the apparent "conflicting" data, we'd be able to see that they are intentionally biased, fabricated, cherry picked or whatever. But I would be surprised that you accept that fact, on average it doesn't function that way psychologically. Which is how humans work, but not a scientific argument.

Anyway, the natural processes, unless cataclysmic, don't make such rapid changes that we experience now. The speed of the change is orders of magnitude faster now than the non-cataclysmic natural ones. It is really going to be worse than most can even imagine. Our children or grandchildren are going to hate us for not doing enough. The politicians and lobbyists who only see their own benefit will be dead and won't care.

To compare with the "good old times": the study of human DNA shows that 70000 years ago, only 2000 humans survived one extinction event:

http://news.bbc.co.uk/2/hi/science/nature/2975862.stm

And then there was no civilization infrastructure to fail, just the hunter-gatherers, ready to move.

So I don't understand why so much of the left chooses to frame the issue in such a way that makes it contingent on that cause.

I think here's where you're going wrong. There's a difference between "is caused by" and "contributes to".

It would be internally consistent to form an argument that supposes an alternate root cause, e.g., solar activity cycles and cycles of the Earth's magnetic field. One can state that these natural problems are (hypothetically) the root cause, while still acknowledging that CO2 is a greenhouse gas and thus decreasing our CO2 emissions - even if we weren't doing anything naughty on our own - might serve to mitigate the damage expected to be caused by those long-term natural cycles.

The common jargon in Liberalese is "anthropogenic climate change", i.e., climate change created by humans. My argument is that they'd have an easier time getting people on board if they went about this without assigning blame.

Saying "there's a problem we need to solve" is going to get a more productive reception than saying "you created this problem and now we need to solve it".

How would someone go about it, and would you trust them?

That's if we keep burning all the carbon. Yes, causes are important.

So you're saying that we need consensus to do things now? My sides are splitting.

Can you name a thing that you think we have "consensus" about?

edit: and wait... "easier to find consensus"! I admit you lost me there. We just don't live in the same world. Do we have consensus for the policies we have now? So what is the justification for favoring them?

"Total radiative forcing is positive, and has led to an uptake of energy by the climate system. The largest contribution to total radiative forcing is caused by the increase in the atmospheric concentration of CO2 since 1750 (see Figure SPM.5). {3.2, Box 3.1, 8.3, 8.5"

"Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system. {2–14}"

http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SPM_...

The politicians, lobbyists and the media aren't the same as the scientists.