By Wee Kean Fong and Elyse Myrans

This article was originally posted on the WRI blog, Insights. 

As home to 3.5 billion of the world’s population, cities and urban areas play a crucial role in combating global climate change. And today, many of their leaders are announcing steps to do just that.

Michael Bloomberg, the UN Secretary-General’s Special Envoy for Cities and Climate Change, announced at the Climate Summit for Local Leaders that more than 400 cities joined the Compact of Mayors, a coalition of city leaders dedicated to significantly reducing emissions. Based on an analysis of 360 cities, WRI found that Compact of Mayors signatories can collectively reduce their emissions by nearly 17 percent below 2010 levels by 2030. To put that in perspective, they can avoid emitting 740 million tons of greenhouse gas emissions annually in 2030, more than what Mexico emits every year.

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How It Works

Under the Compact of Mayors, cities will complete four steps: joining the Compact; measuring and reporting on their greenhouse gas emissions; setting targets to reduce future emissions; and creating a plan explaining how they will achieve their targets. Once a city meets these four requirements, it becomes compliant with the Compact of Mayors.

The popularity of the Compact shows that city leaders are increasingly recognizing that shifting to a low-emissions pathway is not only in the best interest of the planet, but that it will improve the health of their citizens, increase efficiency and lead to economic benefits. Around the world, cities are taking steps such as transforming their transportation sectors, changing building sustainability requirements, and prioritizing investment in renewable energy infrastructure.

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Cities Already Taking Action Under the Compact of Mayors

Rio de Janeiro is the first city to become fully compliant with the Compact of Mayors, committing to reduce its emissions by 20 percent from 2005 levels by 2020. Back in 2013, Rio used the Global Protocol for Community-Scale Greenhouse Gas Emission Inventories (GPC) to measure its emissions. Officials found that transportation and waste were the biggest contributors to the city’s overall emissions, at 39 percent and 19 percent, respectively. So the city is now targeting projects in these sectors—like a new bus rapid transit (BRT) system and bicycles lanes—and is on track to achieve its 2020 goal.

Wellington, New Zealand is another Compact of Mayors city. In 2013, Wellington set its long-term target to lower GHG emissions by 30 percent by 2030 and 80 percent by 2050, based on 2001 levels. Wellington’s action plan identified key steps to achieve its 2030 target, including: increasing renewable generation, reducing energy demand through more efficient homes and commercial buildings, managing energy supply/demand with smart grid technology, increasing the use of public transport, and more.

Tokyo, one of the world’s pioneers of city climate action, joined the Compact of Mayors in October. The city developed its first greenhouse gas inventory back in 1999 and has been updating the data on an annual basis. In 2007, Tokyo committed to reduce its greenhouse gas emissions by 25 percent from 2000 levels by 2020. After realizing that about 40 percent of the city’s total emissions came from commercial and industrial sectors, in 2010, it developed the Tokyo Cap-and-Trade Program, the world’s first urban cap-and-trade program for large-scale commercial and industrial buildings.

Going from Commitments to Action

While the announcement today is very encouraging, it’s a huge challenge to ensure all 400+ cities fulfill the Compact of Mayors’ four-step compliance requirement. To date, only 35 have completed all four steps. Tools, training and technical assistance are essential to help these cities turn commitments into tangible actions.

The Compact of Mayors and its partners have developed a series of tools and training resources. The GPC helps cities measure and report greenhouse gas emissions in a credible and consistent way that is essential for first-year compliance. The GHG Protocol Mitigation Goal Standard guides cities to design emissions-reduction targets, which are required for the second year. And the Guiding Principles for City Climate Action Planning that was just launched today by UN-Habitat and WRI provides internationally accepted principles for creating a climate action plan, which is required for third-year compliance. The Compact of Mayors will also launch a specialized e-learning tool in early 2016 that will serve to educate and guide cities towards joining the Compact of Mayors and becoming compliant.

The Compact of Mayors announcement represents a huge leap forward for city climate action. Today’s commitments demonstrate that cities have the potential to accelerate the global transformation towards a zero-carbon, climate-resilient world.