The costs of climate change are enormous — and so are the opportunities.

As vast and complex as the climate change crisis is, there is no ambiguity regarding the costs. They will be dizzyingly high, and they are beginning to come due.

Mounting annual damages from natural disasters already count in the hundreds of billions of dollars in the United States alone. In the years to come, the global costs of inaction will be tallied in the trillions. The Economist Intelligence Unit estimated that the financial sector worldwide could lose $4.2 trillion in the value of currently managed assets by 2100 – an amount equal to Japan’s total GDP – if global warming isn’t limited to around two degrees celsius. A study in the journal Nature, meanwhile, found that the full social cost of climate change impacts at current greenhouse gas emissions levels over the long term could be as much as $16 trillion. From every angle, the economic cost is staggering.

The human and ecological costs of inaction are even more daunting. Estimates of the total number of refugees who will be forced from their homes by extreme weather and other climate disasters range from 200 million to one billion by 2050. Under a business-as-usual scenario, the figures on species and habitat loss worldwide and the potential collapse of entire ecosystems – virtually all the world’s coral reefs, for example – yield damages that are beyond reasonable calculation.

But there is another, more practical cost that makes a strong case for taking dramatic action on climate change: building a low-carbon economy worldwide represents the greatest economic opportunity of the 21st century. Again, the figures count in trillions – one rigorous recent study estimated that $26 trillion in “direct economic gain” could be added to global ledgers by 2030 through dramatic action to slash greenhouse gas emissions. In the meantime, the global cleantech economy already generates more than $2 trillion annually, and the world’s top economies – led by the United States and especially China – now invest hundreds of billions of dollars annually in emissions-free renewable energy.

Climate change remains a rapidly deepening crisis, but there is real hope to be found – and much money to be made – building out a low-carbon economy in the next 10 years at a speed and scope that will dwarf the last 10. And this project will focus on the engines of the global economy: the world’s cities, where the majority of humanity now resides for the first time ever.

While rural locations are ideally suited to host large-scale wind power generation, biomass, and agricultural investments; diverse, densely populated, economically vibrant urban environments can be the core of this new economy. Cities will require massive infrastructure upgrades – transit lines, smart grids, electric vehicle charging infrastructure, and much more. They will need to host a revolution in building efficiency. They will foster the lively interactions of academics, entrepreneurs and the public sector needed to continue to generate innovation, to maintain and improve our standards of living. And they will create an enviable quality of life that makes low-carbon living not a necessary chore but a welcome improvement on business as usual. (The average resident of Copenhagen, often at the top of global most livable city lists, has a carbon footprint less than a quarter the size of the average North American.)

The challenge of climate change is unprecedented in scale and scope, and it will loom over us for decades to come. But it can be surmounted – not because we are terrified of what we might lose, but because we are ecstatic to discover what we have to gain.

– Chris Turner