COP21 Paris
US Secretary of State John Kerry leaves the COP 21 United Nations conference on climate change on December 12, 2015 at Le Bourget, on the outskirts of Paris MANDEL NGAN/AFP/Getty Images

The real fallout from the Paris climate agreement has just begun. The fuzzy and essentially aspirational deal suits most governments and allows them to declare a victory. Its woolly and non-committal form, however, poses a serious challenge to the EU and Britain's climate policy framework.

The problem arises because the EU failed to achieve its core objective, namely that the Paris agreement should adopt "CO2 mitigation commitments that are legally binding on all parties". This failure has major consequences for Britain's unilateral climate policy.

As part of its Paris negotiations, the EU had offered to cut CO2 emissions by 40% below the 1990 level by 2030. However, this pledge was conditional on all major emitters adopting legally binding targets.

In contrast to the Kyoto Protocol (which runs out in 2020), the new accord no longer includes legally binding CO2 reduction targets. Instead, it is based on voluntary pledges of intentions determined and monitored by individual governments in line with their national interests.

Without legally binding de-carbonisation caps, there will be strong opposition within the EU to making its own conditional pledges legally binding. Poland and other poor member states in Eastern and Central Europe are widely expected to rebel against new unilateral policies that have seriously undermined Europe's competitiveness.

But if EU member states reject new binding targets for the post-Kyoto period, Britain's aggressive climate policies would stick out like a sore thumb, making them politically and economically toxic.

After all, Britain's unilateral de-carbonisation policy makes no sense in the absence of the world's major economies adopting equally binding caps. As a result of the voluntary Paris agreement, both the EU and the UK will be pushed to abandon CO2 unilateralism.

That is why Amber Rudd, the Secretary of State, has promised that the government's new climate policy will no longer pursue a solitary path, but "travel in step with what is happening in the rest of the world", so that energy bills remain affordable for households, businesses remain competitive, and the economy remains secure.

Rudd is following in the footsteps of George Osborne, who has led the fight against the fourth carbon budget. In 2011 the coalition government, under pressure from the Liberal Democrats, set the UK's carbon budget to cover 2023 to 2027. It set out a C02 reduction of 50% compared to 1990 levels by 2025 – the most aggressive target in the world and far more ambitious than the conditional EU target of 40% by 2030.

Osborne has warned repeatedly that adhering to its current targets would damage Britain's economy significantly. He has pledged that the UK will no longer adopt unilateral policies that "cut our carbon emissions faster than our fellow countries in Europe".

The emissions target of the Climate Change Act may be amended if there have been significant developments in international law or policy that make it appropriate to do so. The government has been clear that the UK may revise the fourth carbon budget in light of developments in the EU. If member states refuse to turn the 2030 pledge into nationally binding targets, we can expect Osborne to finally achieve what he has been trying for years: to revise the UK's 2025 target to more modest commitments.

The Secretary of State is to be commended for stressing pragmatism over the unrealistic carbon budget. Even the Climate Change Act must logically be up for amendment given that the Paris summit rejected Europe's and Britain's key demand. The battle for rational climate and energy policies has just begun.

Benny Peiser is the director of the Global Warming Policy Forum