• New York, USA
  • Rio de Janeiro, Brazil
  • Cancun, Mexico
  • Melbourne, Australia

Michael R. Bloomberg
U.N. Secretary-General’s Special Envoy for Cities and Climate Change

Cities around the world are taking the lead in fighting climate change—and determining the course of our planet's future.

We’re for Climate Action We’re for Climate Action

Why Cities

Now more than ever, what happens in cities is shaping our world. Cities are home to the majority of the global population and power the world’s economy. As centers of innovation and progress, they are the key to solving many of the world’s biggest challenges, including climate change. With 70% of the world’s greenhouse gas emissions coming from cities, they also present the greatest opportunities for action.

Mayors around the world are rising to the challenge. They are leveraging their executive powers to protect their cities from more severe storms and weather, and to target some of the biggest sources of greenhouse gas emissions.

From ambitious flood prevention efforts in Dar es Salaam, Tanzania, to new low-carbon bus rapid transit systems in Rio de Janeiro, Brazil, to energy-saving building practices in Melbourne, Australia—cities are leading in the fight against climate change, while improving public health and growing their economies.

Since its launch at the Climate Summit in New York City in September 2014, mayors around the world can sign on to a Compact of Mayors. The compact is an important step forward and gives cities the tools to measure and manage their greenhouse gas emissions in a way similar to nations under the UN’s 1997 Kyoto Protocol.

Cities’ central role was made even clearer by a recent report, which showed that if the world’s cities took bold actions to reduce emissions, their collective impact would be equal to halving global coal use over the next 40 years.

When the world community convenes in Paris in 2015 to create a new climate agreement, cities must be partners in creating a global solution—one that will help avoid the worst impacts of climate change and promote a healthier future.

Climate Report

Our new research, the Special Envoy’s Report to the UN Secretary-General, completed in partnership with C40 Cities Climate Leadership Group and the Stockholm Environment Institute, shows that if all cities took on aggressive new efforts to reduce building, transportation and waste energy use, they could potentially reduce the world’s annual greenhouse gas (GHG) emissions by an additional 3.7 Gigatons (Gt) CO2e by 2030 over what national policies and actions are currently on track to achieve. By 2050, cities could cut annual GHG emissions by 8.0 Gt CO2e over what national policies are currently on track to achieve, the equivalent of cutting annual global coal use by more than half. Cumulatively, cities have the potential to reduce emissions by more than 140 Gt CO2e by 2050.

The first time that cities’ collective GHG impacts have ever been quantified, the Report underscores the importance of including cities’ climate efforts as nations set GHG reduction targets—something nations have rarely done–to prevent the world’s temperature from rising more than 2 degrees Celsius above pre-industrial levels, a ceiling agreed upon in the United Nations’ 2010 Cancun Agreement.

Importantly, the Report identifies actions in each of the sectors where mayors have the greatest control and the most significant opportunities for greenhouse gas reductions. They are the following:

  • Building energy efficiency standards for new urban buildings;
  • Building energy retrofits for existing urban buildings;
  • Aggressive energy performance standards for urban building lighting and appliances; and
  • Transportation mode shifts and transit efficiency for city residents

In the end, this Report demonstrates that cities can actually help their nations achieve the more aggressive GHG targets needed to prevent a global temperature rise, as nations set higher commitments in arriving at a new global climate treaty in 2015.

Mike Bloomberg

Mike Bloomberg Mike Bloomberg

Michael R. Bloomberg is an entrepreneur and philanthropist who served as Mayor of New York City for three terms, from 2002 through 2013. He began his career in 1966 with an entry-level job at Salomon Brothers, an investment firm. After being let go in 1981, he launched a technology startup providing real-time financial data, Bloomberg LP, which grew into a global company that now has 15,500 employees and offices in 73 countries.

As Mayor of New York, Bloomberg’s innovative sustainability plan, PlaNYC, helped reduce the city’s carbon footprint by 19 percent in just six years. After 2012’s Hurricane Sandy, Bloomberg also created the Special Initiative for Rebuilding and Resiliency to repair communities damaged by the storm and to protect the city’s infrastructure from future impacts of climate change.

As a philanthropist, Bloomberg has given away more than $3.3 billion in support of education, public health, government innovation, the arts, and the environment. He serves as board president of the C40 Cities Climate Leadership Group. In 2014, U.N. Secretary-General Ban Ki-moon appointed Bloomberg as his Secretary-General’s Special Envoy for Cities & Climate Change to engage cities and nations in creating more ambitious goals around climate change mitigation and adaptation.


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Climate Change Milestones

Key milestones on the road to the United Nations 2015 climate treaty in Paris, France:


  • December 1997: Kyoto, Japan
    Parties to the U.N. Framework Convention on Climate Change (UNFCCC) adopt the Kyoto Protocol to set international greenhouse gas emissions reduction targets.
  • April 2007: New York City, USA
    Mayor Bloomberg releases PlaNYC, an effort to prepare the City for one million more residents, fight climate change and enhance the quality of life for all New Yorkers.
  • December 2009: Copenhagen, Denmark
    In the Copenhagen Accord, UNFCCC parties recognize that human-caused global warming must stay below 2⁰ Celsius to prevent the worst effects of global climate change.
  • November 2010: Hong Kong
    Mayor Bloomberg is appointed Chair of C40 Cities Climate Leadership Group, the network of world's megacities working together to take measurable actions to reduce carbon emissions.
  • November 2010: Cancun, Mexico
    Nations commit to reduce their emissions, establish Green Climate Fund to finance sustainable and resilient projects in developing nations, and, for the first time, recognize cities as central governmental stakeholders for the next climate agreement.
  • March 2012: Princeton, USA
    To demonstrate Mike Bloomberg’s overarching commitment to sustainability, Bloomberg LP completes an 8-acre solar energy system to help power the company’s New Jersey office.
  • January 2014: New York City, USA
    Bloomberg Philanthropies helps scale the Greener, Greater Buildings Plan nationally by committing $3.2 million to City Energy Project, a 10-city effort to cut carbon pollution.
  • February 2014: Johannesburg, South Africa
    Mike Bloomberg welcomes UNFCCC Executive Secretary Christiana Figueres at C40 Mayors Summit, the first time C40 actively engaged with the UN process.
  • June 2014: New York City, USA
    Mike Bloomberg, Tom Steyer and Hank Paulson release the “Risky Business Report,” a first-of-its-kind report to quantify financial risks of delaying climate action in the U.S.
  • September 2014, Paris, France
    Paris Mayor Anne Hidalgo and Mike Bloomberg meet at Town Hall, demonstrating their eagerness to work together on cities and climate change leading to the Paris COP in 2015.
  • October 2014: Brussels, Belgium
    At the EU’s Mayors Adapt Signature Ceremony, Mike Bloomberg celebrates local leadership in fighting and adapting to the impacts of climate change, and encourages more European cities to join the Mayors Compact.
  • January 2002: New York City, USA
    Michael R. Bloomberg is sworn in as 108th mayor of New York City.
  • December 2007: Bali, Indonesia
    Mayor Bloomberg urges larger focus on cities in fight against global warming to international delegates, as parties create new roadmap to tackle climate change under Bali Action Plan.
  • December 2009: New York City, USA
    Mayor Bloomberg targets buildings – the highest emissions-emitting sector by introducing The Greener, Greater Buildings Plan, which will help reduce NYC’s emissions by 5%. Mayor Bloomberg also presents the plan at the Mayor of Copenhagen’s Climate Change Summit, held alongside the UN’s Climate Conference.
  • July 2011: Washington, DC, USA
    As part of its broad environmental portfolio, Bloomberg Philanthropies commits $50 million to Beyond Coal campaign, to retire one-third of the U.S.’s 500 coal plants by 2020 and replace them with clean energy.
  • June 2013: New York City, USA
    Following Hurricane Sandy, Mayor Bloomberg releases a Special Initiative for Rebuilding and Resiliency, a $20 billion plan to protect New York City against the impacts of climate change.
  • November 2013: Warsaw, Poland
    Nations stay on track to create a new universal climate agreement in 2015 and provide a showcase for climate action by businesses, cities, regions and civil society as important stakeholders in this agreement.
  • January 2014: New York City, USA
    UN Secretary-General Ban Ki-moon appoints Mike Bloomberg as his first Special Envoy for Cities and Climate Change, signaling cities’ significant role in keeping the planet from warming another 2⁰ Celsius.
  • March 2014: Medellín, Colombia
    Mike Bloomberg addresses U.N.-Habitat’s World Urban Forum, focusing on cities’ crucial role in fighting climate change.
  • September 2014: New York City, USA
    At the U.N. Climate Summit, Mike Bloomberg joins Secretary-General Ban Ki-moon and government, business and civil society leaders to announce concrete actions to fight climate change over the next year.
  • September 2014: New York, USA
    At UN Climate Summit, Mike Bloomberg announces new research that demonstrates cities’ importance in fighting climate change, and new initiatives that will accelerate their progress, e.g., the Compact of Mayors.
  • December 2014: Lima, Peru
    Nations present drafts of their new national commitments to reduce emissions, to prepare for climate change and to capitalize the Green Climate Fund.
  • March 2015
    UNFCCC parties present final drafts of their national commitments.
  • December 2015: Paris, France
    The world community agrees to a broad and ambitious global climate treaty.