There Is Always A Worse Worst Case

In The Future We Choose, Christina Figueres and Tom Rivett Carnac, two key figures in the development of the Paris Climate Agreement, describe a pair of potential futures for our planet and human civilization.  
In the Guardian, they summarize the best cast and worst case for our future.

The Worst Case (of course things could always be worse)

...Our world is getting hotter. Over the next two decades, projections tell us that temperatures in some areas of the globe will rise even higher, an irreversible development now utterly beyond our control...Now there are few forests left, most of them either logged or consumed by wildfire, and the permafrost is belching greenhouse gases into an already overburdened atmosphere...in five to 10 years, vast swaths of the planet will be increasingly inhospitable to humans...No one knows what the future holds for their children and grandchildren: tipping point after tipping point is being reached, casting doubt on the form of future civilisation. Some say that humans will be cast to the winds again, gathering in small tribes, hunkered down and living on whatever patch of land might sustain them.

And, the Best Case (already cast in doubt):

While we may have successfully reduced carbon emissions, we’re still dealing with the aftereffects of record levels of carbon dioxide in the atmosphere. The long-living greenhouse gases have nowhere to go other than the already-loaded atmosphere, so they are still causing increasingly extreme weather, though it’s less extreme than it would have been had we continued to burn fossil fuels.

Glaciers and Arctic ice are still melting and the sea is still rising. Severe droughts and desertification are occurring in the western United States, the Mediterranean and parts of China. Ongoing extreme weather and resource degradation continue to multiply existing disparities in income, public health, food security and water availability. But now governments have recognised climate crisis factors for the threat multipliers that they are. That awareness allows us to predict downstream problems and head them off before they become humanitarian crises.

Sadly, the Best Case here requires immediate and sustained planet wide activities that aren't even being considered by the largest greenhouse gas producing countries.  The Worst Case on the other hand could easily be the title of the Trump Republican environmental policy.  A policy being adopted by other countries with like minded autocratic governments.