Meeting the UK's world-leading climate change target will be a "colossal challenge", a government spending watchdog has warned, reports BBC.
The National Audit Office says it will affect the way we work, travel, heat our homes - even how much meat we eat.
In a report it says the cost of cutting CO2 is highly uncertain, but the cost of allowing temperatures to rise would probably be greater.
The PM has vowed to cut emissions by 68% by 2030 based on 1990 levels.
Making the new pledge, Boris Johnson urged other world leaders to follow with ambitious targets at the virtual climate summit he is hosting on 12 December.
The announcement has been broadly welcomed, although scientists say it does not guarantee dangerous climate change will be avoided.
They urged Mr Johnson to impose policies to back up his ambitions - currently the UK is slipping behind its existing targets.
The PM said: “We have proven we can reduce our emissions and create hundreds of thousands of jobs in the process – uniting businesses, academics, NGOs and local communities in a common goal to go further and faster to tackle climate change.
“Today, we are taking the lead with an ambitious new target to reduce our emissions by 2030 faster than any major economy.
“But this is a global effort, which is why the UK is urging world leaders to bring forward their own ambitious plans to cut emissions and set net zero targets.”
One of the UK’s leading climate scientists, Prof Sir Brian Hoskins, told BBC News: “Mr Johnson’s target is ambitious – but we need action to back it up, right now.
He noted that Chancellor Rishi Sunak recently committed £127bn to the HS2 rail link and new roads - which will both increase emissions - while offering just £1bn to home insulation, which would reduce emissions.
Prof Hoskins remarked: “The actions of the chancellor don't measure up. Every single department has to wear climate change glasses when they think of new policies, and the Treasury clearly hasn’t got that message.”
He and other scientists said even if the UK and other nations keep their promises on cutting emissions there was no guarantee the world would avoid serious heating.
“The world will be increasingly difficult and dangerous with every percentage point of temperature rise,” he said. “There are important things we don’t know for sure. How much more does it take to destabilise Antarctica, for instance? We don't know… and the impact could be devastating.”
Prof Corinne Le Quéré from the University of East Anglia said if nations matched the UK’s lead “it won’t be a safe climate – but it will be a safer climate than we’d get based on current levels of ambition.”
A coalition of green groups is urging the government to reach a 75% cut by 2030.
And more radical groups such as Extinction Rebellion say the UK should stop emissions almost completely within a few years to be confident of avoiding climate disaster.
Research by the London School of Economics (LSE) found that it is economically feasible for UK emissions to be cut by 72%. The government has not costed the range of measures that would be needed, but experts say more homes will need to switch to low-carbon heating. Gas-guzzling SUVs might also be forced off the roads – and frequent fliers taxed more.
The Committee on Climate Change (CCC), which advises government, welcomed the 68% cut, but warned: “This is more than just a number.
“It should be accompanied by wider climate commitments, including the development of a policy package and net zero strategy to deliver against the UK goal; clear commitments to reduce international aviation and shipping emissions; and greater support for climate finance, particularly for developing countries.”
Net zero refers to cutting greenhouse gas emissions as far as possible and balancing any further releases by removing an equivalent amount from the atmosphere.
More policies will be revealed if the long-delayed Energy White Paper is published, as expected, before Christmas.
The prime minister’s 68% target represents the UK’s NDC – its nationally determined contribution towards meeting the Paris Agreement.
