Britain currently aims to cut its emissions by 80 percent by 2050, but campaigners say that does not go far enough to meet pledges made under the 2015 Paris climate agreement
* Target achievable by 2050 with existing technology -advisers Government advisers say policy and societal changes needed
* Want new fossil-fuel car ban brought forward to at least 2035
* Lower consumption of beef, lamb likely needed -report
* Calls for increasing renewable, low-carbon electricity (Updates with government statement, other comment, context)
By Susanna Twidale
LONDON, May 2 (Reuters) - Britain should commit to a net zero greenhouse gas emissions target by 2050, government climate advisers said, a goal that could require phasing out new petrol and diesel cars by at least 2035 and a 20 percent cut in beef and lamb consumption.
Their recommendations came in a report released on Thursday after weeks of civil disobedience protests by climate group Extinction Rebellion meant to raise pressure for action to tackle what it calls a global climate crisis.
On Wednesday, Britain's parliament declared a symbolic climate change "emergency" in a nod to the increasingly vocal activist movement.
Britain currently aims to cut greenhouse gas emissions (GHGs) by 80 percent compared with 1990 levels by 2050. But campaigners say this does not go far enough to meet pledges made under the 2015 Paris climate agreement to try to limit a rise in global warming to 1.5 degrees Celsius.
"The UK can end its contribution to global warming within 30 years by setting an ambitious new target to reduce its greenhouse gas emissions to zero by 2050 (on 1990 levels)," the Committee on Climate Change (CCC) report said.
The government-commissioned report said the new target is achievable with existing technology but can only be met if the government ramps up climate policies.
A current goal to phase out new petrol and diesel cars by 2040 would come too late and would need to be brought forward to at least 2035 or 2030 if possible, the report said.
Several European Union countries or cities have proposed banning diesel cars in a clampdown on polluting emissions, such as Spain, also from 2040.
More renewable and low-carbon electricity would be needed to meet the UK's target, and technology to capture and store or use carbon dioxide emissions from industrial sectors must be adopted, the report added.
Households would also need to be weaned off natural gas heating and switch to low-carbon alternatives such as hydrogen or heat pumps, the report said.
Britons should be encouraged to consume around 20 percent less beef, lamb and dairy products, while growth in air travel would likely need to be curbed unless the aviation sector adopts low-carbon fuels such as biofuel or electrified air travel.
A statement from Conservative Prime Minister Theresa May's government said: "We are not immediately accepting the recommendations set out in the (committee's) detailed report but will be responding in due course to ensure the UK continues to be a world leader in tackling climate change."
Climate scientists have warned that failure to limit global temperatures at 1.5 degrees would lead to rising sea levels, catastrophic weather events such as droughts and floods and the loss of species.
INACTION MORE COSTLY
The CCC report said the cost of meeting the new target would be around 1-2 percent of Britain's GDP - tens of billions of pounds a year. It said the Treasury should undertake a review of how the transition should be funded.
The cost of delay, or inaction, would be much higher, the report said.
Sam Fankhauser, director of the Grantham Research Institute on Climate Change at the London School of Economics and Political Science, said Britain was not now even on track to meet its carbon budget goals for the late 2020s and early 2030s.
"If this is not addressed sooner rather than later, taking the necessary steps will be more expensive for UK taxpayers."
Legislation would have to go to parliament before a new climate target could become law.
CCC Chief Executive Chris Stark told journalists the law could be in place before international climate talks in Chile at the end of the year since there was cross-party consensus in Britain on the need to act.
Stark said that if Britain, the world's fifth largest economy, set a net zero target, this could encourage other countries to do the same and increase the likelihood of the Paris climate target being met.
(Reporting by Susanna Twidale and Nina Chestney Editing by Mark Heinrich)
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