The global effort to confront climate change was hobbled for many years by the mistaken idea that only national governments and international rules could solve the problem. The Paris agreement, which recognizes and supports voluntary carbon-reduction efforts by cities, regions and businesses, was an important step in the right direction. Ironically, no one has done more to demonstrate the agreement’s strengths than its most prominent critic: Donald Trump.

Last week, the Trump administration formally notified the UN of its intention to withdraw from the Paris agreement. It was an empty gesture, because no party can actually withdraw until November 2020 (right after the next US presidential election). What matters is this: the US is on pace to reach the commitment we made under the agreement – and there is nothing Washington can do to stop us.

Over the past decade, the US has led the world in reducing carbon emissions. In that time, the US Congress has never passed a single law directly aimed at climate change.

The central climate-related regulation adopted by the Obama administration – a carbon emission standard for power plants – was put on hold by the courts and never even went into effect. And yet we are already about halfway to our Paris goal of reducing carbon emissions by at least 26% by 2025.

That progress has happened because cities, states, business and citizens all recognize the health and economic benefits of action. And they are not slowing down now. In fact, the biggest impact of Trump’s withdrawal from the Paris agreement has been to accelerate those efforts and improve public understanding of their central role in fighting climate change.

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Take cities, which are home to the majority of the world’s people for the first time in human history. Mayors understand that the same steps that reduce carbon emissions also make cities better places to live and work – and where people want to live, businesses want to invest. Mass transit, parks and trees, and less traffic congestion all reduce air pollution and carbon emissions, while helping cities to grow.

Globally, cities account for about 70% of carbon emissions. That makes them the bulk of the problem, but they are also the source of the most effective solutions. In New York City, we were able to reduce emissions by 19% in just six years, while also outpacing the nation in job growth. Mayors around the world, from across the political spectrum, are increasing their use of clean energy sources, such as wind and solar, which is now often cheaper than fossil fuels.

Since the Trump administration announced its intent to withdraw from the Paris agreement, more than 2,500 US cities, states, businesses and universities have signed a letter reaffirming their commitment to the agreement’s goals. Bloomberg Philanthropies is helping lead an effort – we call it “America’s Pledge” – to measure the collective potential of all these groups to reduce their carbon emissions.

Just as every nation has done, we will create a clear and transparent report to account for these efforts, and show how they help us to fulfill the pledge we made in Paris. These reports will be made available to the UN and the parties to the Paris agreement.

We’ll also work with our partners to draw up a blueprint for how each group can accelerate their progress, despite current inaction by the federal government. That includes helping cities access financing for green infrastructure and developing regional policies that encourage investment in clean energy.

Under the leadership of Governor Jerry Brown, the state of California – by itself the world’s sixth-largest economy – recently announced a commitment to getting 60% of its energy from clean sources and strengthened its cap-and-trade system for carbon emissions. Other states can follow suit.

There is also more action coming from the private sector. Until recently it has been hard for businesses to measure the potential financial impacts they face from climate change, which makes them difficult to prevent and reduces incentives to address the problem. It also makes it hard for investors to know which companies are most vulnerable to climate risk and which are taking action.

Last year, I was asked by the Bank of England governor, Mark Carney, to chair a global Task Force on Climate-related Financial Disclosures to help close this data gap, by creating financial standards for measuring and reporting climate risks. We recently released a set of recommendations and are working to help more companies adopt them.

National pledges under the Paris agreement assume involvement from national governments – but the fact is, in the US, progress on climate change has always been driven from the bottom up. More help from Washington would be helpful and welcome, but cities, states and businesses aren’t waiting for it.

The benefits of action – and the risks of inaction – are too great.