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Third of world’s remaining carbon budget could be determined by urban policy decisions



US Secretary of State John Kerry & Michael Bloomberg are today welcoming city mayors to the State Department at the culmination of the Our Cities, Our Climate program. The C40 Cities Climate Leadership Group (C40) and Stockholm Environment Institute (SEI) announced a new report today, which demonstrates that urban policy decisions before 2020 could determine up to a third of the remaining global carbon budget that is not already ‘locked-in’ by past decisions.

Existing research has shown that investing in low carbon infrastructure in the next five years will be four times less expensive than building high carbon infrastructure now, and then having to replace it in the future. Mayors and local leaders in power today thus have a major role to play in determining whether or not we have a cost-effective and, therefore, realistic path to a climate safe world.

“This report provides hope for the future because it shows that we don’t just have to rely on the outcome of the critical COP21 negotiations, but that mayors and city leaders in office right now have the opportunity to protect a large share of the world’s carbon budget,” said C40 Chair and Rio de Janeiro Mayor Eduardo Paes. “The report calculates that moving from a business as usual scenario to low carbon urban development across all the world’s cities would save 45 Gt CO2 by 2030 – equivalent to eight times the current emissions of the United States.”

Scientists have previously calculated that we can emit a ‘carbon budget’ of just 1,000 Gt CO2 without creating an unacceptable risk of run-away climate change, and that much of this budget may be locked-in by investments such as fossil fuel power stations, highways and energy-hungry buildings that have already been made.

Previous research has suggested that decisions about the remaining infrastructure will be taken in the next five years, by 2020. Fortunately, C40 and SEI’s new analysis shows that a third of the decisions will be made in cities, meaning local leaders in office right now, many of whom have already demonstrated leadership on climate change, can grasp the opportunity to move on to a low-carbon path.

“This report shows how important urban policy decisions are to tackling climate change – and how mayors have great financial incentives to act,” said UN Secretary General’s Special Envoy for Cities and Climate Change, Michael R. Bloomberg. “Investing in modern and efficient infrastructure now, rather than continuing to expand traditional high-carbon infrastructure, will be four times less expensive over the long run. It’s the latest example of how fighting climate change is good for taxpayers.”

Negotiations for a critical new climate treaty, taking place in Paris this December at COP21, concern action to be taken after 2020. But mayors can, and are, taking action right now. More than half of all C40 cities have committed to the Compact of Mayors, a global platform where cities publish their current emissions inventories and commit targets and action plans to cut future emissions. Hundreds more cities around the world are following suit and making ambitious commitments. None needs to wait for the outcome of treaties and talks to take action.

This new report is thus both a major boost in ongoing efforts to deliver a climate safe world, and provides further evidence that there needs to be a major focus on supporting mayors and action in cities.

The report was launched at an event honoring international and US mayors, including many C40 cities, and held today at the US State Department; the event served as the culmination of Our Cities, Our Climate, an historic initiative by the US Secretary of State John F. Kerry and Michael R. Bloomberg, UN Secretary-General’s Special Envoy for Cities and Climate Change, to leverage the leading role cities play internationally in advancing innovative climate change action.

About the C40 Cities Climate Leadership Group

The C40 Cities Climate Leadership Group, now in its 10th year, connects 82 of the world’s greatest cities, representing 640+ million people and one quarter of the global economy. Created and led by cities, C40 is focused on tackling climate change and driving urban action that reduces greenhouse gas emissions and climate risks, while increasing the health, wellbeing and economic opportunities of urban citizens. The current chair of the C40 is Rio de Janeiro Mayor Eduardo Paes; three-term Mayor of New York City Michael R. Bloomberg serves as President of the Board. To learn more about the work of C40 and our cities, please visit, follow them on Twitter @c40cities and like us on Facebook at