Over the weekend, the UK’s three main political leaders pledged to tackle climate change after the next election, whatever the outcome.

The Conservative’s David Cameron, Labour’s Ed Miliband and the Liberal Democrat’s Nick Clegg agreed to work towards a legally-binding global climate deal, to agree new UK emissions-cutting goals and to phase out unabated coal-fired power.

Carbon Brief assesses the significance of the unusual joint pre-election pledge.

Cross-party pledge

There are three parts to the  party leaders’ pledge, published on Saturday after months of behind-the-scenes negotiations brokered by NGOs, including Green Alliance, Christian Aid and the Women’s Institute.

The leaders agree:

• To seek a fair, strong, legally binding, global climate deal which limits temperature rises to below two degrees.

• To work together, across party lines, to agree carbon budgets, in accordance with the Climate Change Act.

• To accelerate the transition to a competitive, energy efficient low-carbon economy and to end the use of unabated coal for power generation.

The first part of the pledge, on a legally-binding climate deal consistent with limiting warming to two degrees, is in line with official EU policy. So the UK government already supported this aim.

The wording does not specifically refer to the UN climate talks where leaders are supposed to agree a deal in Paris this December. This omission may be to allow for the chance that the Paris talks agree a deal which is  not legally binding, or which falls short on the goal of limiting warming to no more than two degrees.

The second part, on UK carbon budgets, is also a restatement of current policy. The Climate Change Act is legally binding and says that carbon budgets must be agreed according to a fixed timetable and the advice of the Committee on Climate Change.

The coal phase out pledge is a new policy for Labour and the Conservatives. However, it reflects  current government expectations that unabated coal use for energy would have in any case ceased by around 2030. Unabated coal would be off the electricity grid by 2027 under central projections from the Department for Energy and Climate Change.

New unabated coal plants are already banned in the UK. The Liberal Democrats had pledged to ban all unabated coal by 2025. They had also backed an electricity decarbonisation target for 2030, as had Labour and the Committee on Climate Change. This would heavily restricted the operation of coal-fired power stations.

Domestic political significance

Given the lack of truly new policy in the party leaders’ statement, you could be forgiven for asking what all the fuss is about. Indeed, the pledge was not considered significant enough to feature in BBC Radio Four’s ‘Week in Westminster‘, the weekly round-up of the week’s top political stories. The news was also absent from Radio Four’s Sunday summary of the week’s newspapers and from Monday morning news bulletins.

Yet the UK probably hasn’t witnessed a similar show of cross-party political unity on climate change since parliament voted to pass the UK Climate Change Act in 2008, with the support of all the main party leaders and only five votes against.

The joint pledge is, therefore, domestically significant for what it rules out, rather than what it rules in, because it reduces the chance that the next government could weaken the UK’s stance on climate change.

It should quell environmentalists’ fears of a future Conservative government aiming to match the UK Independence Party’s climate skeptic position. It also marginalises Conservative former environment minister Owen Paterson’s call to scrap the Climate Change Act.

The promise to jointly agree future carbon budgets under the Act could prevent a repeat of last year’s review of the fourth carbon budget, initiated by chancellor George Osborne. The Committee on Climate Change will recommend a fifth carbon budget later this year.

The UK does not need coal to keep the lights on. The committee said last year that current power generating capacity was sufficient to meet all but the highest peaks of demand, without coal. Last week, research showed the UK could do without coal power as early as 2023.

Emissions impact

A coal phase out would have a large impact on UK emissions, because it emits more than twice as much carbon dioxide as gas, per unit of electricity generated.

Coal-fired power stations emitted around 114 million tonnes of carbon dioxide in 2013, around a quarter of the UK total. So UK emissions would fall by a quarter if nuclear or renewables were used to supply this electricity. They would fall by 15 per cent if gas were used instead.

It’s hard to say if the joint pledge will accelerate coal emissions reductions, because the coal phase-out has no deadline attached. Arguably, the UK would have had to phase out unabated coal in order to meet its legally binding carbon budgets. The leaders’ pledge simply confirms what would have had to happen anyway and prevents any backsliding by future governments.

The international emissions impact of the coal phase-out is complicated, too. Power sector emissions are part of the EU emissions trading scheme (EU ETS). The EU ETS is capped, so if UK emissions fell on a coal phase-out, other EU countries would be allowed to emit more.

Planned reforms of the EU ETS could modify this situation by removing surplus emissions permits at certain times, but they have yet to be agreed.

The international emissions impact would also be complicated by any price effects due to reduced UK coal consumption. If coal prices fell in response to reduced demand, it could cause coal consumption to increase elsewhere.

International political significance

The pledge is internationally significant, too. The UK was the home of the coal-driven industrial revolution. It remains the third largest user of coal in the EU and 14th largest in the world. Coal still accounts for nearly a third of UK electricity production.

A major report last year said developed countries should aim to stop using coal as quickly as possible, as part of cost-effective efforts to tackle climate change.  The UK joins Denmark and Finland in pledging to follow this advice.

Campaigners asking other governments to do the same are bound to use the UK as an example. Germany, in the spotlight for its high coal use, has said it cannot phase out coal and nuclear at the same time.

UK climate and energy secretary Ed Davey says:

“The agreement between British political leaders to end unabated coal power in the UK is a positive step. But we now need to take an open, honest and pragmatic look at how, in Europe and beyond, we can address unabated coal globally if we are to meet our climate goals.”

In broader political terms, the cross-party UK climate pledge is already being used as an example to others. In Australia, a Nobel laureate says his country’s political leaders should follow the UK lead. In the US, the Washington Post compares UK leaders’ unity to Republican and Democrat disagreement over climate.

Former Mexican president Felipe Calderón says:

“The UK’s cross-party agreement serves as a positive example to other countries struggling to act on climate change. A focus on the simultaneous economic and climate benefits of low-carbon growth makes sense from any angle, and can help bridge typical partisan divides.”

So, while the UK leaders’ pledge may not make that big a difference to outcomes in the UK, its wider impacts could prove influential around the world.