Just for example, without petroleum, will we revert back to wood and metal for everything?...bye-bye plastics??
I don't care about preserving glaciers.
The "likely" effects are unknown. Mankind will have to adapt, like we always have. Without a global authoritarian government, there is no way to get other nations to stop their bad environmental behavior. Indeed, many Leftists will argue that they can continue because of anti-colonial equity or some such theory. There is no global solution.
And as far as urgency...I don't see it from the people who say it is urgent. They are still putting our country into an existential threat level of debt on things that are totally unrelated. They are borrowing from future generations to pay people today for "equity." When your side stops borrowing from the future, I will stand up and take notice, and give you credit for actually being concerned about the future.