Consider the end of the world.
The UN has just announced its findings that, even if the Paris Agreement were met, it would see global temperatures raised by 3-5 degrees on pre-industrial levels. Far worse, and this is buried in the story, it has declared that even if all carbon emissions stopped right now, the Arctic would still be an average of 5 degrees warmer by the century's end, after eighty years of relief, than it was in the period 1986-2005.
All carbon emissions will not stop right now. Short of a colossal, chiliastic political rupture, carbon emissions will continue to massively expand for the foreseeable future. Paris, even if it was universally implemented, locks that in. As to the effects, up to this point official estimates from the IPCC have tended to significantly underestimate the rate of Arctic warming and melt. Last year's Arctic winter was much warmer than average.
Given this, it is difficult to see the ice caps lasting for much longer. And it is difficult to see how that doesn't mean the end. A melted Arctic will certainly open, briefly, new commercial and military channels, which each Arctic power is desperate to be the first to exploit. But the feedback effects of Arctic warming are, by now well-known. Reducing albedo, wherein solar radiation is reflected back into space, will accelerate warming. Melting permafrost and releasing methane will accelerate warming. Increasing the surface area of dark water available to absorb rather than deflect heat will increase oceanic warming. Taken together with the ongoing carbonic acidification of the oceans, this will kill a lot of marine life, bleach the last corals, destroy the most biologically productive areas of the planet. This life is responsible, not only for the fish we capture and eat, but for about half the oxygen that we breathe. Such an ordinary thing as breathing will become a lot more effortful in the near-certain future.
Take this in conjunction with other relatively recent findings. Researchers at the MIT have announced that, by 2070, billions would regularly suffer deadly heatwaves, and half a billion would be struck by temperatures that would kill in the shade within six hours. Last year, the UN estimated that it will take just sixty harvests for the erosion of fertile top soil to make the feeding of humanity impossible. Such ordinary things as eating and being outside will become far more hazardous and difficult, far more of a struggle, in this future. All of this, combined with dropping insect biomass, desertification and more regular flooding and weather disasters, will likely congeal with the crisis tendencies of the capitalist mode of production to produce chronic, worsening breakdowns in the means of life. Consider the kinds of politics that will give rise to.
The planet toward which we are accelerating is one in which the chances of human survival are very slim. It is remarkable, and wrenchingly awful, to contemplate this. But it is also, just, true. It is the most realistic appraisal, short of a political breakthrough scattering all existing coordinates of political realism. And it is the most idle utopianism to suggest otherwise.