Momentum is building toward December's summit on climate change in Paris. Unlike the 2009 Copenhagen summit, where high hopes were dashed by low politics, this time the world's two biggest polluting countries (the U.S. and China) are onboard.
Political leaders will find it harder than ever to avoid their responsibilities.
The shameful truth is that the slow response to this urgent issue means some climate change is now inevitable.
But we must not waver from the common goal of limiting a global temperature rise to 2 degrees.
The United States has committed to reducing their greenhouse-gas emissions by 26-28 percent below its 2005 levels in 2025. The European Union has put forward a target of 40 percent. And Japan is expected to announce a target of at least 20 percent.
Developing nations like Mexico and China have agreed to reduce their emissions after 2026 and 2030, respectively.
These announcements are an important benchmark for other countries, including Australia. We have the highest greenhouse emissions per capita in the developed world, and our commitment is crucial to a successful global approach to tackling climate change.
Commitments from national governments are the crucial foundation for keeping us below a 2-degree-temperature rise.
Cities are where these national commitments will turn from words to action. Cities are economic hubs, driving development, growth and investment. But cities are also causing more than 70 percent of global greenhouse-gas emissions.
We must improve on the 20th century model of urban sprawl, fossil-fuel consumption and private motor-vehicle transport, or preventing runaway climate change may not be possible.
Fortunately, a number of mayors are leading the way, and those who are taking action are seeing the economic and health benefits of investing in sustainable climate solutions.
In Sydney, our Sustainable Sydney 2030 long-term plan lays out a vision for becoming a green, global and connected city. We are on track to meet our ambitious greenhouse-gas-reduction target of 70 percent below 2006 levels by 2030.
As well as planning for a city driven by clean energy, we are forming profitable partnerships with the private sector to reduce emissions today.
Our Better Buildings Partnership with property owners covers more than half of the Sydney CBD's commercial-floor space. The program has reduced emissions in these buildings by 35 percent, putting it ahead of schedule to reach the 70 percent target by 2030. Businesses have also slashed their energy bills by $30 million a year.
Our efforts are based on our belief that addressing climate change promotes both growth and livability -- and we are not alone. While national governments have struggled to work together to solve the global-climate crisis, mayors are cooperating through organizations like the C40 Cities Climate Leadership Group (C40) to deliver concrete results.
Sydney will co-chair the C40 Private Sector Buildings Energy Efficiency Network with the Tokyo Metropolitan Government. We're hoping to share some of the secrets of our success with them, and other cities.
Seoul is reducing their entire city's energy demand by the equivalent output of one nuclear power plant, through energy conservation and the use of renewable-energy sources.
By 2020, San Francisco will be diverting 100 percent of its garbage away from landfill, avoiding enormous amounts of greenhouse gases. In 2010, they were already diverting 80 percent away from landfill.
These are examples we can all learn from. If Chicago has a great idea, Johannesburg can benefit. If Singapore is taking effective action, Mumbai can gain, too.
In 2012, we began to replace our street lights with new LED bulbs. This was an idea we borrowed from Los Angeles, and it has already cut emissions from street light by more than 46 percent.
City leaders across the globe are pulling together and pulling their weight.
In the coming weeks, Australian Prime Minister Tony Abbott will decide whether our country is a climate lifter or a climate leaner. The success of global-climate negotiations rests on this kind of decision.
The economic consequences of failing to act are serious. Over the past 12 months, investment in the renewable-energy sector in Australia has collapsed because of the Abbott Government's unwillingness to take serious action. This investment is now headed to other cities and regions that support clean energy, while we miss out on a global boom in the industries of the future.
If Prime Minister Abbott makes the wrong decision, he will make Australia an international pariah that cowers from its duty to act.
The world is now moving, and it is time for Australia to step up. The City of Sydney is ready to support an ambitious target that Australia puts into place, and to lend our full weight to achieve those goals.
Clover Moore is Lord Mayor of the City of Sydney. Sydney is one of 75 city members of the C40 Cities Climate Leadership Group, which -- along with UN Special Envoy Michael Bloomberg and other city networks -- has launched the Compact of Mayors, the world's largest cooperative effort among cities to fight climate change.
This post is part of a Huffington Post What's Working series on the environment. The series is putting a spotlight on initiatives and solutions that are actually making a difference -- whether in the battle against climate change, or tackling pollution or other environmental challenges. To see all the posts in the series, read here.