Folly

The cost of denying global climate change was high and multiplicative. The sea levels rose, which was bad. But they rose higher and faster than expected and the impact of erosion was vastly underestimated.
The weather patterns--ALL the weather patterns--changed dramatically. We were no longer able to predict the weather on a daily basis, much less long term. Draughts and blights ruined formerly productive agricultural regions.
Multiple pandemics swept the world. Melting ice revealed "new" viruses and bacteria. Flooding and infrastructure compromised public sanitation. Rising sea levels swamped Superfund Sites and leached pollutants into the water tables faster and further than ever before. Public health systems began to collapse under the weight of waves if sick and dying and governments began to succumb as well.
It wasn't an apocalypse. It was several.
On the plus side, wars ended. Too few soldiers left to fight them, and those who remained refused to follow any orders that didn't involve seeing to their own. First individual units and then whole armies turned themselves towards rescuing and preserving what lives they could, regardless of borders.
There was no denying that it was well past time for action and the general populace had little patience for half-measures.
"The Folly" became the vernacular term for the failure of global leadership to acknowledge the clear evidence of global climate change and the following tragedies which made the Exfil Edict necessary.