SAN FRANCISCO — Steve Benjamin, a mayor from South Carolina, flew into this city to talk about climate change — and was rushing back out to deal with a hurricane.

“We in the Carolinas are forced to deal with the realities of climate change every single day,” Benjamin told USA TODAY from the tarmac at San Francisco International Airport as the Democratic lawmaker waited for his plane to return him to Columbia, S.C., the state capital of 134,000 where people are bracing for Hurricane Florence, which has already forced the evacuations of more than 1 million.

Scientists say that the strength of hurricanes could increase in the future due to climate change, and they've pointed to fossil-fuel burning as a contributor to a turbulent summer of global floods, heat waves and wildfires.

Florence, feared to be as bad or worse than last year's Hurricane Harvey because of its size and the chance that it will bring days of rain and severe flooding, is the kind of extreme weather mayors like Benjamin are worried about.

On Tuesday, ahead of a climate change conference here, the U.S. Conference of Mayors issued a report that 95% of surveyed mayors said their cities had experienced climate change impacts in the past five years, with heavy rains, inland flooding, heat waves, drought and wildfires at the top of the list.

Florence comes on top of a summer of drought, extraordinary strong wildfires in the West and massive heatwaves and fires in Europe and Africa. The past four years have been Earth's hottest on record.

The Global Climate Action Summit, which opens Wednesday, is meant to showcase the ways American cities, states and businesses, along with international groups, are moving forward in dealing with the root cause of global warming — carbon emissions — even as the Trump administration has withdrawn the United States from the Paris climate agreement.

It's co-chaired by California governor Jerry Brown, one of the leaders in the "We Are Still In" movement. This self-described "bottom up" group began last year as a bipartisan coalition of more than 3,500 political and business leaders who represent an economy of $6.2 trillion.

More:Hothouse Earth: Runaway global warming threatens 'habitability of the planet for humans'

More:Environmentalists: New documents reveal why Trump shouldn't lower gas mileage standards

More:Tech firms like Google, Amazon push power companies toward solar and wind, a blow to coal

Brown on Monday signed into law a plan to shift California — the world's sixth largest economy — to 100% zero-carbon electricity by 2045, just 27 years from now.

“It’s not going to be easy, and it won’t be immediate, but it must be done. California is committed to doing whatever is necessary to meet the existential threat of climate change," Brown said at the signing.

The global reach of the conference is clear in its international lineup, which includes officials from countries across the globe, including China, India and the United Nations.

The three-day meeting aims, among other things, to find ways for groups from states to non-profits to Fortune 500 companies to make headway on lowering the greenhouse gasses that cause climate change when national elected officials will not.

Renewable energy, which is becoming cost-competitive with electricity generated by fossils fuels, is a big part of that.

Onshore wind generation now costs an average of 6 cents per kilowatt hour, while solar is typically 10 cents per kilowatt hour. The cost of electricity generated by burning fossil fuels is generally between 5 to 17 cents per kilowatt hour, according to a report released in January by the International Renewable Energy Agency.

The conference will be a mix of how-to workshops for state and local governments, big-picture idea plenaries, a few Hollywood celebrities and lots of protesters. Some will be environmentalists decrying the Trump administration's move away from climate change mitigation, others will be activists demanding the state phase out all oil production.

If the government won't help stall global warming, maybe business can, hope some scientists and civic leaders. They're dismayed by the Trump Administration's efforts to roll back climate change mandates, including diluting a requirement that energy companies look for potent greenhouse gas methane leaking from oil and gas wells, weakening fuel-efficiency standards for cars and light trucks and rolling back carbon pollution limits for power plants.

The administration argues that such rules were too expensive, hurt businesses and are unfair to America. President Trump has said in the past he believes that global warming is a hoax.

Some business fixes are readily at hand, said Nigel Purvis, CEO of Climate Advisers, a climate consulting firm.

“Renewable energy is as affordable as non-renewable in huge parts of the world. Clean cars are safer, cleaner and faster than traditional cars,” he said.