Ideally, there is probably a happy middle ground to be found. Legally binding annual cuts in greenhouse gases are undesirable for the same reason balanced budget legislation is a poor fiscal policy. They unduly restrict the responsiveness of governments to unforeseen needs and emergencies. Unexpected events do and will occur and can often push a nation into debt for a given year, whether that debt is measured in dollars or carbon dioxide makes little difference. The point is to remain financially, and environmentally sustainable over time.
In today's Queen's Speech, the government announced its new climate change bill promising five-year targets to cut carbon dioxide emissions, and suggesting that an independent commission - rather than ministers - would set the targets. Those targets would in-turn be set within the context of a legal commitment to cut CO2 emissions by 60% from 1990 levels by 2050.
It is now for the government to make good on its promises by passing the bill intact and undiluted. In doing so, they would set an example for most the world to follow.