CO2 levels of ~900 ppm cause significant cognitive impairment... Unless we take action we will hit that level by the end of the century.
Long before that large areas of the Earth will become uninhabitable...
Water demand will rise, water supply will drop....
Food demand will rise, drought and heat will cut supply-increased CO2 will lead to the crops that are harvested being less nutritious.
All this will lead to a refugee crisis orders of magnitude worse than what we can even conceive... Or do we expect the billions affected to politely die of heat stroke and starvation without making too much fuss about it?
Adding to the refugee crisis will be the conflicts that result from dwindling resources.
We are not talking about something in the distant future- this will all come to pass in the next 25 years.