US environmentalists Friday hailed the signing of the landmark Paris climate pact by more than 170 countries on the first day it is open for signatures.

"On Earth Day this year we can say that the Paris climate pact signals the start of a potential new era of positive global change," said Roy Morrison, a U.S. scholar who in 1995 put clear concept and description for the "ecological civilization" in his book.

China joined with more than 170 countries in signing the Paris pact on Friday, giving a strong push to the international efforts against global warming.

China also announced it will finalize domestic procedures to ratify the Paris Agreement before the G20 summit in China in September. UN Secretary-General Ban Ki-moon immediately welcomed the pledge.

Morrison said, "Chinese leadership and progress in reducing carbon dioxide is crucial for the ecosphere and for building an ecological civilization."

In his book "Eco Civilization 2140" published in 2005, Morrison, an observer of China's progress on environmental protection and ecological civilization construction in the past years, predicted that China will lead the way toward sustainability in 2070-2090.

"It's up to the leading emitters, China and the United States, to be leaders in an ecological turn," said Roy in an interview with Xinhua.

More than 170 countries took the first step of signing the deal on Friday in the biggest day one

endorsement of a global agreement.

Many environmentalist groups in the United States celebrated the historic moment at the UN headquarters Friday, saying that it showed determination of the world to join hands in taking action against climate change.

Michael Brune, the executive director of the Sierra Club, an American environmental organization founded by preservationist John Muir in 1892, said in his blog that "This Earth Day, we mark a major milestone in stopping one of the most dangerous mistakes our species has ever made: Digging up and burning enough fossil fuels to change our planet's climate."

He noticed that "China may already have reached peak coal as it accelerates its clean-energy development," adding that it needs not only governments that sign the Paris agreement, but also efforts of millions of ordinary people to make our future better.

Nancy Skinner, a nationally syndicated radio and television commentator who is currently the host and executive producer of the "Climate Talk Radio," told Xinhua that "The most astonishing thing to me is that for decades now, the U.S. has used 'China's reluctance' as an excuse to not pass any meaningful policy on Climate Change."

"Meanwhile, China has shown that it has not only embraced renewable energy, it is owning that sector. For the Paris Agreement to succeed the United States must grow up and deliver on our commitments."