Someone just asked the standard question 'What possible benefit could anyone get for making up global warming'. Here is my answer:
Climatology was created for global warming, till then it was meteorology, with the climate being a sideline in geology or geography. Now everyone with a BSc is a climatologist, and share the billions in grants and huge amounts of publicity and policy making amongst each other.
Without the threat of global warming the extreme left and green movement would have remained forever on the lunatic fringe where they belong. Now they are mainstream.
Energy companies now receive billions in renewable subsidies, and the price of fossil fuel has shot up since governments have put restrictions on its production and distribution. Therefore they get money for nothing for wind farms that don't work, and more for their existing reserves. Win-win for all.
Assuming there was already a one world government plan in place, they need a reason or people will reject it. The UN now have in place a global carbon tax and global carbon currency which, like the Euro, will need full political integration to implement. Agenda 21, also created on the back of global warming, is accepted by over 200 countries, the first informal step to world government.
The entire third world are racing ahead economically while the west restrict carbon emissions and they can produce free of regulations.
I'm sure I could go on for ages but that's quite enough to cover the main areas.