Gregory Korte

USA TODAY

WASHINGTON — History may judge the Paris climate agreement as a turning point for the planet, President Obama said Wednesday as the United Nations reached a key threshold triggering the implementation of the climate accord.

With nations representing more than 55% of world carbon emissions now having signed on to the agreement, the deal now goes into effect in 30 days. The agreement requires countries to come up with nation-specific carbon reduction plans in an effort to keep global temperatures from rising more than 2 degrees Celsius, or 3.6 degrees Fahrenheit, over pre-industrial levels.

"Today is a historic day in the fight to protect our planet for future generations," Obama said. "Make no mistake: This agreement will help delay and avoid some of the worst consequences of climate change."

With the early October temperature at 70 degrees under a partly cloudy sky, Obama spoke about the agreement for five minutes from the Rose Garden, a venue usually reserved by President Obama for the most significant events. And with less than four months left in his term, Obama cast the agreement as an integral part of his presidential legacy.

"One of the reasons I ran for this office was to make America a leader in this mission. And over the past eight years, we've done just that," he said.

Under his administration, he said, American "led by example" by investing in wind and solar power, instituting new power plant emission limits and raising fuel efficiency standards. "From the cars and trucks we drive to the homes and businesses in which we live and work, we've changed fundamentally the way we consume energy," he said.

But the United States signed on to the accord by executive agreement, without seeking the Senate ratification that would make it binding, and future administrations may not adhere to its provisions. Democratic presidential candidate Hillary Clinton supports the deal; Republican presidential candidate Donald Trump has said he would "cancel" it.

And Obama said even the Paris Agreement alone will not solve all the world's climate-related problems, and called on countries to "ratchet down" their emissions targets over time.

Obama's five-minute remarks came in an unscheduled statement after the European Union, Canada and Nepal notified the United Nations Wednesday that they were signing on to the agreement. The United States and China, the world's two largest emitters of carbon pollution, submitted their approvals last month. Obama said that the agreement two years ago between China and the United States gave the overall plan the momentum it needed to succeed.

Under the agreement, the deal automatically takes effect once 55 countries — accounting for 55% of world carbon emissions — sign on. There are now 71 nations responsible for 58.7% of emissions.

EU lawmakers endorse Paris climate pact