Many Greens sincerely believe these predictions are accurate so they are acting according to their beliefs. At least they are genuine even if it is debatable whether they are right.
Clearly the speed with which they want to move on this issue would have serious repercussions for the country but over a longer time period I think they are on the right track. We should be developing and switching to renewable forms of energy and reducing our consumption of non-renewable and polluting fossil fuels. But there is no way we could do that in the time frame the Greens want and not destroy our economy.
