We have entered the age of the local leader. At COP21, more than 400 mayors came together for the Climate Summit for Local Leaders, organized by Mayor of Paris Anne Hidalgo and former New York City Mayor Michael Bloomberg, the United Nations Secretary-General’s Special Envoy for Cities and Climate Change. This was the largest climate-oriented gathering of mayors to date, providing a forum for a dynamic discussion of solutions and ambition on climate targets.

Perhaps even more importantly, it signaled a new era in climate action. Historically, discussions on climate policy have largely portrayed cities as the source of problems, painting them as major polluters and areas of intensive resource consumption.

The conventional wisdom was that national governments were the only institutions able to solve global environmental problems; cities were simply left out of these conversations. The inclusion of cities at COP21 demonstrated the fact that the narrative has changed — there is now widespread recognition of cities as global problem-solvers, capable of tackling broad issues like climate change.

Empowering Cities to Continue to Lead

More than 3.5 billion people live in cities today, and 2.5 billion more will live in urban areas by 2050. So it’s simply impossible to solve climate change without action at the city level.

Three big things happened during COP21 proceedings that will prime cities for ambitious climate action:

1. Enhanced mitigation: More than 400 mayors signed on to the Compact of Mayors, a global initiative to reduce emissions in cities around the world. WRI research shows that action from 360 of these cities will avoid 740 million tons of carbon dioxide annually in 2030, more than Mexico’s annual emissions. Now it is up to all of us to make sure that this ambitious commitment remains transparent, to ensure that these lofty goals come to fruition.

2. Finance: We must address the $4.1-4.3 trillion dollar gap in urban climate finance, recognized by the Cities Climate Finance Leadership Alliance. International financing bodies and banks must collaborate on the supply side to fill this gap. COP21 saw an increase to commitments for public funds by national governments, like Japan, committing to $10 billion annually by 2020, also witnessing banks increasing financing for climate projects, including over $70 billion committed collectively by Bank BNP Paribas, and Crédit Agricole CIB. However, the demand side must also respond to this need, by converting this gap to a concrete call for funds, backed up by proposals for specific, on-the-ground green investment opportunities.

3. Formally putting cities on the agenda: Paris City Hall provided a beautiful backdrop to the high-energy cities events at COP21, a manifestation of the bold, collaborative local actions being undertaken in the climate fight. By the end of the Sustainable City Forum, U.N. chief Ban Ki-Moon announced that in future negotiations, cities would be recognized formally.  This is an important recognition that national governments are just one actor in the fight against climate change. One of the first big follow-ups to this announcement will be a “Climate Action 2016” summit to be held in Washington, D.C. in May of 2016. Look for cities to play a leading role.

Better Cities for a Better Climate

COP21 proved itself to be a forum for cities to share actions, to create a more formal dialogue regarding local solutions, and to commit to new actions. Importantly, these new actions will build upon transformative steps that have already been taken.

City leaders have already shown that they are up to the climate challenge, demonstrating across the globe their resolve to develop and implement innovative solutions that not only address climate change, but also make their cities better places to invest, work, live and play. Portland, for example, has met success with its Climate Action Plan, making strides towards its ambitious goal of reducing its carbon emissions 80 percent by 2050. The city has employed municipal efficiency and renewable energy standards, cultivated connected communities, and invested in light rail and streetcar lines.

Sao Paulo is another example of a city that has taken initiative on climate change. The city leveraged private partnerships to expand its network of sustainable mobility options, including an integrative metro line aimed at connecting multiple modes of mass transit.

Now more than ever, cities have established themselves as factories of climate change solutions, working towards multisector strategies that improve livelihoods and city form, while also addressing emissions. COP21 acknowledged this transformative power, and established a path forward to empower these local actors in the global challenges posed by climate change.

Building on Progress Made at COP21

The important step, now, is for increased support for cities in creating or scaling up their climate goals, from the private sector, national governments, and NGOs, alike. Creation of a space for cities to share their solutions — as well as a strong financial foundation for practical actions — can lead to all cities having the political courage to take the first steps necessary for transformational change. To lay the financial groundwork, governments can improve routes to creditworthiness for municipalities, and establish funds specifically for urban sustainability and climate programs within national plans.

COP21 has primed the global policy arena for these steps, increased ambition, and created an environment amenable to further city-level action on climate. By embracing and supporting cities as centers of advancement on the massive problem of climate change, it is possible to continue successful urban policy experimentation. Cities are the ones taking major risks with new and bold policies — we have much to learn from their experiences.

This blog originally appeared on Devex.