Governments don't need a vast global hoax incorporating thousands of scientists and masses of fraudulent data to grab power, or to raise taxes, they just do it.
When Labor's in, they just say "we need to raise this tax, or introduce this policy, to fix the Liberals' mess"
When the Liberals are in, they just say "we need to raise this tax, or introduce this policy, to fix the Labor mess"
Moreover, politicians are simply too dumb and incompetent to manage such a vast global hoax.
The simpler explanation is that greenhouse gases do, in fact, trap heat; and as a result, temperatures are, in fact, rising and ice extent is receding.