Scientists have been fairly unequivocal in their warnings that we must ditch fossil fuels entirely if we are to have any hope of reversing climate change. Yet despite significant progress in the last year, historic announcements like the China-U.S. climate pact are still pushing a less ambitious, more incremental approach to cutting our emissions.

That may be why many activists are focusing on the local, community level to push a more radical approach. As I recently reported over at TreeHugger, a new grassroots movement has launched petitions in hundreds of cities across the world calling for a transition to 100 percent renewable energy/zero emissions by 2050 at the latest. While this may have sounded like wishful thinking a few short years ago, these activists are actually building on a growing number of communities that have already taken such pledges — and some who appear to have achieved them.

So who are these leaders in the clean energy world?

Aspen, Colorado: 100 percent renewable electricity by 2015

The beautiful tourist town of Aspen, Colorado, hasn't just pledged to go 100 percent renewable for its electricity supply, it has pledged to do so by 2015. According to Go 100% Renewable Energy, a website dedicated to promoting and supporting the 100 percent clean energy goals of cities, businesses and even countries, Aspen has already achieved 86 percent renewable energy by 2014, mostly in the form of existing hydro power but with some wind included. This goal is part of an effort to cut community-wide emissions 80 percent by 2050.

Copenhagen, Denmark: Carbon neutral by 2025

Copenhagen, the capital of Denmark, has a distinct advantage because the entire country is already committed to ambitious renewable energy goals. Indeed, the city's pledge to become the first carbon neutral capital by 2025 is greatly helped by the fact that offshore wind already supplies most of the city's energy needs, but the city is now working on carbon-free transportation, including already world-class bicycle infrastructure, as well as greener heating options like combined heat and power plants and geothermal energy. The city is collaborating closely with nearby Malmö, Sweden, which has set similarly cutting-edge goals.

Bonaire, The Caribbean: 100 percent renewable energy by 2015

The Caribbean island of Bonaire (population 14,500, plus 70,000 tourists each year) is not exactly a major metropolis, but its efforts to go 100 percent renewable are worthy of note because a) they have nearly been achieved already and b) because, as an island, Bonaire was previously dependent on expensive and disproportionately polluting diesel generators. After a fire destroyed the previous diesel-fired power plant in 2004, the island set a goal of 100 percent renewable energy by 2015. Using a combination of wind power and battery storage, combined with backup diesel generators which will eventually be fueled by algae-based biofuels, the island is looking to completely sever its ties with fossil fuels for electricity.

wind turbines in Bonaire, the Caribbean

Wind turbines in Bonaire, the Caribbean. (Photo: Donal Boyle/creative commons)

Munich, Germany: 100 percent renewable electricity by 2025

Munich, with a population of 1.35 million people, is Germany's third largest city. So its commitment, set in 2008, to produce enough renewable power to meet the entire city's electricity needs by 2025 is a significant step toward a clean energy future. According to the city's website, significant progress has been made already:

On completion of the already initiated or executed projects, SWM will have a generation capacity of around 2.8 billion kWh of green electricity from its own plants. That equates to 37 percent of Munich’s power consumption and is significantly more than the requirements of all of Munich’s approximately 800,000 households as well as the underground and tram systems.

Sydney, Australia: 70 percent emissions cuts by 2030

Sydney is also getting in on the clean energy game. As part of its efforts to cut total greenhouse gas emissions 70 percent by 2030, the city is aiming for 30 percent of electricity to be produced from renewable sources and 70 percent from ultra-efficient trigeneration (combined cooling heat and power). The city's renewable energy master plan has the details.

San Diego, California: 100 percent renewable electricity by 2035

California has already seen explosive growth in the solar energy and electric car markets. In San Diego, that growth is feeding into an effort to have community-wide 100 percent renewable electricity by 2035. Here's the scoop from Go 100% Renewable Energy:

The plan, which is being framed as an economic development and jobs initiative, has support in the City Council, including that of the City Council President, who as Interim Mayor, included the 100% renewable power goal in his Climate Action Plan released in January 2014. The previous Mayor also had committed to a 100% renewable energy goal for the city in April 2013. Other bold elements in the September 2014 plan include a legally binding goal to reduce the city's greenhouse gas emissions 50% by 2035, advancing electric vehicles and their infrastructure, increasing walking and biking as modes of transportation, energy efficiency building retrofits, and planting trees.

Isle of Wight, England: 100 percent self-sufficient and renewable by 2020

Not exactly a metropolis either, but the Isle of Wight's 142,500 inhabitants will soon be benefiting from a 100 percent renewable energy supply if the EcoIsland initiative succeeds. Technologies being pushed include 1,300 solar roofs, waste to energy, tidal, wind power and geothermal, as well as a smart grid rollout aimed at conserving energy and matching supply with demand. Efforts to install onshore wind turbines have, however, met with some community resistance.

Frankfurt, Germany: Zero carbon emissions by 2050

Much like Munich, Frankfurt am Main is pushing an ambitious carbon reduction goal within a nation that is more committed than most to a truly low carbon economy. As the whole of Germany pursues its "energiewende" (energy transition) policies, Frankfurt is aiming for a staggering 100 percent reduction in carbon emissions by 2050 at the latest. And there has already been significant progress with reductions in energy consumption achieved, despite significant growth in the city's economy:

Frankfurt on Main founded one of the first municipal energy and climate protection agencies, which has been promoting a comprehensive energy management scheme since 1985. The city is a member of Energie Cities und Eurocities, has conducted a wide range of projects at the European level, and is a member of the Covenant of Mayors. Frankfurt updates its energy and carbon footprint annually, with the goal being a 100 percent reduction of carbon emissions by 2050. Already, emissions have been reduced by 15 percent since 1990 even though the economy has grown by more than 50 percent – and office floor area by more than 80 percent.

San Jose, California

With its position in the heart of Silicon Valley, it's no surprise that San Jose is positioning itself to lead on matters of technological innovation. Part of that positioning is a goal of achieving 100 percent renewable electricity by 2022. Part of the city's push has been to reduce red tape associated with installing solar power. Here's more from Go 100% Renewable Energy:

Helping to show they mean it, the city is one of the few in the U.S. to have eliminated a building permit requirement for residential rooftop solar, breaking down a big barrier to solar PV uptake. San Jose also plans to install solar on its municipal facilities, support technology innovation, and help create bulk power purchasing arrangements. Additionally, the city aims to support power purchase agreements that allow businesses and residents to sell solar power they generate to utilities.

San Francisco, California: 100 percent renewable electricity by 2020

And finally, San Francisco is also pushing the envelope too. The Mayor’s Renewable Energy Task Force was established in January 2011 to develop recommendations to help meet this goal within 10 years. And again, significant progress is being made. According to a 2012 recommendations report, the goal was both entirely achievable and already well underway:

San Francisco’s electricity supply is already 41% renewable, due to a completely renewable municipal power supply from the San Francisco Public Utilities Commission’s (SFPUC) hydroelectric, solar, and biogas facilities, and a state renewable portfolio standard (RPS) that required most utilities and electricity service providers to meet 20% of their electricity demand with eligible renewable resources by 2010, increasing to 33% by 2020. Pacific Gas and Electric (PG&E), which provides most of the power for San Francisco residents and businesses, is on track to meet the 20% requirement by 2013, with a 2010 supply mix that included 15.9% RPS-eligible resources and another 15.6% from large hydroelectric sources.
And many, many more...

These cities and communities already make up an impressive list and, collectively, represent millions and millions of global citizens whose environmental footprint will be greatly reduced as their goals are achieved. But they are just a few among many. And as grassroots efforts to push more cities into action gear up, we may see cities overtaking nation states as the primary driver for a clean energy economy. Add that to the cities and communities divesting from fossil fuels and the picture really starts to get interesting. 

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