Cities sit on the front line of climate change. They house half of the world's population and are responsible for the vast majority of global economic output. It is not unusual for the largest cities to produce emissions that exceed those of medium-sized countries.

It is clear that they face major challenges in transitioning to low-carbon economies. Cities need solid data if they are to meet the scale of goals to reduce environmental impact that we need to see.

As Mayor Bloomberg of New York City says: "We will never meet the ambitious goals we set as an organization without solid data to measure our progress; as I've always said: If you can't measure it, you can't manage it."

That is why we have expanded the Carbon Disclosure Project's global reporting framework that has been used successfully for years to help corporations measure and report on carbon emissions, to cities around the world. 

There are many compelling reasons for cities to measure and report their greenhouse gas emissions and climate strategies: addressing risks, providing transparency for city residents, and creating economic opportunities and increased competitiveness.

These reasons are laid out in a CDP and Accenture report, "The Case for City Disclosure."

Innovation and opportunity are key factors for cities to consider. There is significant potential for disclosure and sustainability actions to drive R&D and innovation in areas such as clean tech and sustainable urbanization, for example.

As Jay Bhatt, senior vice president at Autodesk, said: "To create cities that support a better quality of life while minimizing environmental impact, today's designers need a clear picture of the impact of climate change … allowing planners to develop strategy for improving the urban environment."

Measuring and reporting is not solely about reducing carbon, increasing operational effectiveness and adopting strategies to safeguard the future of cities -- vital as these all are. Creating transparency and accountability through a standard disclosure platform also enables data to be shared with the global marketplace to drive investment and make them attractive places to live, work, study and locate businesses. What's more, it helps cities share best practices with their global peers.

There are challenges too. Budgetary, political and time pressures on cities can all make disclosure challenging.

Yet, despite the challenges, reporting puts cities on a journey to greater awareness, transparency, and management of carbon.

Image CC licensed by Flickr user midweekpost.