One of Supreme Court Justice Antonin Scalia's last acts was to halt the EPA's Clean Power Plan, at least temporarily threatening the United States' ability to carry out promises made in Paris on curbing climate change. But that doesn't mean things aren't moving forward.

Eighteen states issued statements supporting the Clean Power Plan the day after the Supreme Court's stay. More importantly, cities aren't waiting around, and they are the ones that can really make a difference in the battle to curb greenhouse gas emissions.

A group of cities from different parts of the world came together in 2005 to discuss climate action at the municipal level, later becoming a powerful network known as C40. Today the group counts 83 members. C40's board president is Michael Bloomberg, and members include Beijing, Moscow, Cairo and Sao Paulo as well as US cities Boston, Chicago, Houston, Los Angeles, New York City, Philadelphia, Washington, DC, Austin, New Orleans, Portland, San Francisco, and Seattle.

C40 cities have launched more than 9,800 individual climate actions since 2011, and 30% of these actions are coming from city-to-city collaboration. C40 cites a recent report by the New Climate Economy, a research organization, which estimates there is a $17 trillion opportunity worldwide by 2050 from investments in smarter, low-emission cities.

Cities consume 78% of energy globally, according to CDP, the major organization collecting data on climate risk,  and without intervention the power generation market would be on track to double its carbon emissions by 2040. The good news is that of 162 cities reporting to CDP on their energy mix, 35% say already more than 75% is from non-fossil fuel sources. "2015 CDP data reveals that in many countries, cities are leading the way in making the global switch to renewable energy," reads a CDP infographic. "Can cities quit fossil fuels? Yes." CDP works with cities to help them manage greenhouse gas emissions, and is now playing matchmaker, identifying municipal projects the private sector can invest in around the world, in areas such as energy efficiency, resilience and forestry, and sustainable transport. Apparently, there is money to be made. 

Copenhagen is leading the charge for economic growth through carbon neutrality. The city has a goal to become carbon neutral by 2025, and Mayor Morten Kabell says achievements are already ahead of schedule.

"The aim was that in 2015 we should have reduced by 20 per cent from 2005 levels," he says, "but the number is actually something like 36 or 37 per cent."

Copenhagen's plan focuses on four areas: energy, mobility, city administration and energy consumption. One advantage is that the city's grid provides district heating. "So that is a question of removing coal and oil as fuel for the power plant and replacing them with biomass, with wind and the solar industry," says Mayor Kabell. "Those are existing technologies."

The city also wants to encourage its inhabitants to travel by bicycle, by public transportation or on foot, and its urban planning revolves around this. "We try to create transport networks using three Cs: compact, connected and coordinated," says the mayor. "We are trying to create a high-density city where residential areas and commercial areas are connected. It's also a question of which kind of commercial development you want to promote, as a city. Do you want to promote big malls? Go ahead. Make lots of room for cars. If you want to promote local shopping, local businesses, promote walking and cycling. That is a choice you're making as an urban planner, and that's important." Copenhagen has plans to build 26 "bike superhighways."

Some of Copenhagen's goals:

-          to lower public buildings' energy consumption by 40 per cent, commercial buildings' by 20 per cent, and household consumption by 10 per cent;

-          to lower energy consumption of street lighting by 50 per cent;

-          to assure that all of the city's energy consumption will be from renewable sources; and

-          to make the city's renewable energy production exceed its energy consumption.

In May, 2014, the London School of Economics published a report on Copenhagen as a "green economy leader," listing eight drivers of its green economy. The report paints a picture of a leader in innovation with a cleantech cluster and a highly skilled workforce. It describes a city investing in energy and resource effectiveness, with falling water consumption and only two per cent of municipal waste going to landfill in 2010. The report also notes that Copenhagen is a "city of entrepreneurship," where the city's low carbon and environmental quality programs and investments provide it with all the ingredients to turn carbon neutrality into a growth opportunity.

But can this be done elsewhere? Morten Kabell says it can. "Everyone can do this," he says. "In Copenhagen it has actually been a big reason for not having had a recession throughout the financial crisis." His message to other mayors? "Just get going. It's good for the economy; it means a healthier population; it means more generally that you're able to stand up and say we're doing our part."