Climate Change
Climate Change is predicted to lead to pronounced global warming by the middle of the century or earlier. Some of the best minds in these scientific areas have worked long and hard to come to a consensus about what is likely to happen to the planet if we do not change the way we deal with the generation of greenhouse gasses.
While there is some skepticism about the science behind these predictions, the predictions are probabilistic and no-one is predicting a specific number for any of the quantified predictions, nor about the specific timing of the predicted effects. On the other side of the argument, most of the deniers are suspected of having vested interest and they have not produced any evidence that the predictions will be wrong.
While there is some uncertainty about the timing and the severity of climate change, there is no doubt that human generated carbon dioxide is a significant cause of the looming problem.
We would be grossly negligent in our duty of care for the planet which we leave to our children and their children if we were to do nothing until the catastrophe is upon us.