"Climate is too complex for accurate predictions":

Climate change models, no matter how powerful, can never give a precise prediction of how greenhouse gases will warm the Earth, according to a new study.

The result will provide ammunition to those who argue not enough is known about global warming to warrant taking action.

...What is more, they found that better computer models or observational data will not do much to reduce that uncertainty. A better estimate of sensitivity is the holy grail of climate research, but it is time to "call off the quest", according to a commentary published alongside the paper.

Which raises the question as to why major policy decisions are being advocated based on inherently unreliable models.