Britain's surprising vote to leave the European Union in a national referendum on Thursday sent a shock through global financial markets, and there is similar concern that the move will have profound implications for climate policy as well.
Clean energy investments, carbon markets and the Paris climate agreement weren't a major part of the calculus when Britons went to the polls, but now environmentalists fear Britain's contribution to global climate action may be compromised, with negative ramifications for global warming.
"It leaves me shocked, disappointed and extremely concerned about the future of environmental protections in the UK," James Thornton, the chief executive of ClientEarth, a non-profit environmental law organization with offices in London, Brussels and Warsaw, said in a statement. "Many of the laws which my organization uses to ensure that nature and health are protected in Britain were drawn up with the UK's agreement in Brussels. Now as the UK prepares to go it alone, we have no idea which laws will be retained."
The UK's former energy and climate change secretary Edward Davey went further, quoting the Bible in a tweet.
"Father, forgive them for they do not know what they are doing"
— Edward Davey (@EdwardJDavey) June 24, 2016
Many fear the decision to leave the EU could plunge the world into an economic slowdown or recession, with former Treasury Secretary Lawrence Summers saying the economy is more fragile than any time since World War II.
If world economies are affected, it could depress greenhouse gas emissions growth in the short term, Chris Huhne, Britain's the former secretary of state for energy and climate change, told Climate Home.
In the long term, however, an economic downturn would threaten the kind of massive investments required for a transition to a clean energy economy, wrote the Guardian's Damian Carrington.
The UK has traditionally been a leader on climate policy, including in 2008 when it became the first country to set a long-term binding law mandating emissions be cut by 80 percent by 2050 and creating a voluntary emissions market before the EU launched its own carbon trading system.
Politicians who led the Leave movement and who may take on new leadership roles after Prime Minister David Cameron departs could seek to roll back existing climate policy. Cameron announced on Friday that he would step down by mid-October.
One of those potentially ascendant politicians, Nigel Farage, who led the push for this week's referendum has said "I haven't got a clue whether climate change is being driven by carbon-dioxide emissions" and expressed interest in ending pollution regulations on power plants.
Boris Johnson, a leading contender to be the UK's next prime minister after Cameron leaves, has said that warm weather caused by humanity is "without foundation."
Those sentiments prompt some to question whether the UK will continue with its plans to phase out coal power plants by 2025.
"In the long term, were the British public to buy into the Leave camp's vision of bonfires of so-called 'red tape,' I worry that the anti-environment, anti-climate action wing of the conservative party would come into the ascendency, taking Brexit as mandate for their preferred course of action," Friends of the Earth UK spokesman James Goode said.
We May Not Always Have Paris
UK's shifting political landscape could have a significant impact on the Paris climate agreement. "It could potentially submit a highly ambitious [nationally determined contribution] to the U.N., it could ramp down its ambition, or it could ignore it, which would be a blow to the whole process," Will Nichols, a senior environment and climate change analyst at the risk advisory firm Verisk Maplecroft told Politico. Earlier in the week, Christiana Figueres, the U.N.'s outgoing climate chief, said a Leave vote on Brexit would force a revisit of the plan EU countries submitted in Paris.
Tim Rayner, a climate policy analyst at the University of East Anglia, said the UK's exit will shift the balance of power on energy policy in the EU.
"Especially with Poland exerting its weight, 2016 will see some rather tough negotiations over 'effort sharing' towards the EU's 40 percent emissions target," Rayner said. "The UK's 80 percent reduction target is a big part of that collective goal. "
European Union carbon prices were down more than 10 percent Friday morning following the vote, their lowest level since March.
While it's still too early to tell exactly what Britain's departure from the European Union means for climate policy in the UK and beyond, many experts predicted dire implications.
The Institute of Environmental Management & Assessment an association for environmental professionals, polled more than 4,000 environment and sustainability professionals on the risks and opportunities associated with Brexit in the lead-up to the referendum.
Approximately 80 percent said that the UK's influential role in the development of EU environment and climate policy means the UK would have exercised greater international influence inside the EU than outside.
"It is absurd to suggest that Brexit could be good for the environment when the major challenges we face, not least the risk of catastrophic climate change, are international by their nature," Clive Lewis, the Labour party's energy and climate change minister told the Guardian.
Rise of Nationalism
Some experts said the vote is an expression of a global wave of populist nationalism that threatens to undermine action on climate and other issues, including migration and collective security, in Europe and beyond.
"The radical populism that we see exhibited ... is antithetical to the approach we need to deal with climate change," said Paul Bledsoe, a former climate adviser during the Clinton administration who is now an independent energy and climate consultant.
"You see it in the U.S. in the states' rights movement and you see it in Trump. That's a bigger concern than the Brexit vote itself. Our politics are moving in a direction of radical entrenchment. Structurally, as countries break ties with international institutions, their ability to act together is reduced on a wide range of issues, from trade, to climate and defense. It does legitimize a worldview that questions participation in any global institution," he said.
Dr. Susanne Dröge, a senior research fellow at the German Institute for International and Security Affairs, a nonprofit think tank in Berlin, said in an interview before the referendum that "a leave vote would be a downer."
"The UK has been pretty ambitious when it came to setting EU climate policy, testing new approaches for carbon pricing, showing a way forward," she said. "I'm really worried that we see so many countries twisting toward a nationalist approach, when implementing the Paris agreement really needs international action to solve a global problem."
Bob Berwyn contributed reporting for this story.