Tech firms, including Apple, Amazon, Google, and Microsoft, are banding together following President Trump's controversial decision on June 1 to withdraw the U.S. from the historic climate change treaty.
Social media giants Facebook, Twitter, and Snapchat also joined the effort. Noticeably absent were Oracle, IBM, and all the major telecommunications providers.
The new campaign, called "We Are Still In," formally debuted on Monday after it was quietly announced last week.
"We Are Still In" represents the most serious attempt yet by local officials, business executives, and private-sector leaders to buck the Trump administration's decision, which sent political shockwaves around the world.
Participants vowed to meet the Paris agreement's target of limiting global warming to "well below" 2 degrees Celsius, or 3.6 degrees Fahrenheit, above preindustrial levels by 2100. They also pledged to accelerate the transition to renewable energy.
"In the U.S., it is local and state governments, along with businesses, that are primarily responsible for the dramatic decrease in greenhouse gas emissions in recent years," the group wrote in an open letter to the international community.
"Actions by each group will multiply and accelerate in the years ahead, no matter what policies Washington may adopt," they wrote.
The new coalition includes dozens of university and college leaders, including the chancellors of six University of California campuses, the president of New York University, plus schools from many states in between the coasts. Nineteen attorneys general joined the group, including New York AG Eric Schneiderman and Massachusetts AG Maura Healy, both of whom are investigating Exxon Mobil for allegedly deceiving investors on the company's climate risks.
Michael Bloomberg, the former New York City mayor and a U.N. Special Envoy for Cities and Climate Change, is coordinating the effort. He's expected to deliver the statement to the U.N. Framework Convention on Climate Change (UNFCCC), the body that oversees global climate negotiations, on Monday afternoon.
Bloomberg has said that efforts by cities, states, and companies to reduce greenhouse gas emissions might ultimately be enough to meet America's current commitment under the Paris treaty. Former President Obama pledged to reduce the country's emissions by 26 to 28 percent by 2025, from their levels in 2005.
"American society remains committed to achieving the emission reductions we pledged to make in Paris in 2015," Bloomberg said in a statement.
The coalition intends to submit a "Societal Nationally Determined Contribution" to the U.N., which will be called "America's Pledge" and account for the climate-fighting efforts of U.S. cities, states, businesses, and other subnational actors.
It would be rare, if not unprecedented, for a coalition like this to formally join a U.N. treaty meant for nations to sign.
Christiana Figueres, a former top U.N. climate official who helped broker the Paris treaty, told the New York Times there is currently no formal mechanism for entities that aren't countries to fully participate in the Paris accord.
Patricia Espinosa, who succeeded Figueres in the top U.N. climate job, said the organization applauded the U.S. coalition's move.
"The UNFCCC welcomes the determination and commitment from such a wealth and array of cities, states, businesses and other groups in the United States to fast forward climate action and emissions reductions in support of the Paris Climate Change Agreement," she said in a statement.
"We Are Still In" is the latest in a string of related efforts that have cropped up in the days since Trump's Paris announcement.
Thirteen governors representing both political parties have joined the newly created United States Climate Alliance, which commits states to upholding the global warming targets under the Paris Agreement.
In addition, more than 200 mayors (and counting) have pledged to intensify their local climate efforts to meet the Paris Agreement's aspirational goal to keep global warming to 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, above preindustrial levels through 2100.
That more stringent temperature target is a high priority for low-lying developing nations that are worried about sea level rise.