Doyle Rice

USA TODAY

World leaders from 175 countries signed the historic Paris climate accord Friday, using Earth Day as a backdrop for the ceremonial inking of a long-fought deal that aims to slow the rise of harmful greenhouse gases.

"We are in a race against time." U.N. secretary-General Ban Ki-moon told the gathering at the United Nations headquarters in New York. "The era of consumption without consequences is over."

"The poor and most vulnerable must not suffer further from a problem they did not create," Ban added.

U.S. Secretary of State John Kerry signed the document while holding his young granddaughter. She was one of 197 children at the event to represent the parties that adopted the agreement, Ban said.

"These young people are our future. Our covenant is with them," Ban said. "Today is a day for our children and grandchildren and all generations to come."

The non-binding treaty, approved in Paris in December after years of U.N. climate negotiations, aims to slow the rise of greenhouse gases, such as carbon dioxide, blamed for putting Earth on a dangerous warming path.

The deal sets a target of limiting global warming by 2100 to “well below” 2 degrees Celsius (3.6 degrees F), as compared to pre-industrial levels. To accomplish that, each nation sets its own target for reducing emissions and updates that mark each year.

Friday's signing sets a record for the number of countries signing an agreement on the first available day, the Associated Press reported. The old record goes back to the Law of the Sea in Montego Bay, which was signed by 119 countries in 1982, according to AccuWeather.

The heat is on: Our view

Signing the accord is only one step in the process. The leaders must now go back to their home countries' governments to ratify and approve the agreement, which could take months or years. The deal goes into effect once 55 countries representing at least 55% of global emissions formally join.

Nations not at the ceremony will have one year to sign the accord, then will need extra time to get it ratified and approved by their governments.

The U.S. and China, which together account for nearly 40% of global emissions, said they intend to formally join the agreement this year, AP reported. Both nations signed the document Friday.

“The signing could not come soon enough," said Andrew Steer, president of the World Resources Institute. "Each month since the Paris agreement was reached has brought fresh evidence that Mother Nature has a fever and all life on Earth is suffering the consequences."

Ice melt forces polar bears into paths of Alaska schoolchildren

Last year was the planet's hottest on record, and 2016 is already on path to surpass it, according to data from the National Oceanic and Atmospheric Administration and NASA.

Over the past winter, the peak in Arctic sea ice was the lowest since records began 37 years ago, according to the National Snow and Ice Data Center.

"The signing and early ratification of the Paris agreement will be essential if we are to save the world from runaway climate change," said Hugh Sealy, a U.N. climate change expert from St. George's University in Grenada.

Environmental groups praised the event.

“We won’t beat climate change with a piece of paper," said Rhea Suh, president of the Natural Resources Defense Council. "Today marks a beginning, a historic start."

"We’re leaving the age of Jurassic fuels behind — for good — and moving to cleaner, smarter ways to power our future," she said.

Others weren't as impressed.

Mike Duncan, president of the American Coalition for Clean Coal Electricity, called the signing "nothing more than a parlor game lacking consequence or purpose; it’s purely symbolic."

"The simple truth of the matter is that the agreement is an exercise in futility as the reduction targets are wholly unachievable," he added.