ITV News Science Editor Tom Clarke explains the pledge
The decision to commit the UK to a "net zero" carbon economy by 2050 is a momentous one.
If the change to legislation gets through Parliament, it would commit the UK to nothing less than a new industrial revolution.
Thirty years seems like a long time, but the shift away from fossil fuels and improvements in energy efficiency that would be required in that period could make this one of the most radical economic and social commitments a civilian government has undertaken in modern times.
That is of course, if it does happen.
Theresa May is a prime minister with, frankly, nothing to lose, in search of a legacy that is anything but the disaster of her Brexit negotiations.
Her government is already set to miss near-term climate change targets, and a target 30 years off is a VERY long time in politics.
The legislation also has to get through Parliament, and survive what looks like a five year break-out clause which allows a future government to ditch the commitment if other major economies don’t follow suit and the UK ends up disadvantaged by its ambition.
But I think it’s reasonable to think it will happen, and essential that it does.
First, it is likely to get through Parliament, and be adopted by a future government. All the main Tory leadership candidates have said they support a "net zero" economy. Labour, the Lib-Dems and you guessed it, the Greens support it too.
Second, Sweden and Denmark have passed similar legislation already. And if President Macron has his way, the French are likely to be just behind the UK in getting their economies off fossil fuels.
Talk in Westminster is the Treasury was very nervous about a prime minister with, frankly, nothing to lose, signing Britain up to a policy change that could cost us nearly a £1 trillion.
How can we afford to do this? When in fact the question should be, how we can afford not to? The threat from climate change is real. The costs of doing something about it will be much less if we do something now, rather than wait for things to get more dangerous.
Also that £1 trillion figure was arrived at by the Treasury. The costs calculated by the Committee on Climate Change, which has done a bit more work on it than they did suggests when you factor in the economic benefits of a zero-carbon economy it’s a win-win.
Cleaner air, warmer homes, more trees, cheaper transport and electricity (eventually) means huge cost savings to the NHS, local authorities and tax payers.
And that’s not even considering the amount you save on avoiding the dangers and costs posed by climate change.
By being the first G7 economy to commit to a zero-carbon future also helps your chances of having developing the tools and industries that other countries will need when they too pursue more environmentally friendly economies.
One danger this or any future government must avoid is failing to bring society with them. The misery and deprivation following the collapse of industries like coal mining still lingers in many parts of the UK. A badly managed zero-carbon transition could do the same. And would become quickly politically unacceptable.
The degree of economic and social upheaval required to end kick the carbon habit might sound crazy. But a quick reading of the science of climate change tells us it would be crazy not to.