Full coverage: G20 Hangzhou Summit

BRUSSELS, Sept. 5 (Xinhua) -- The determination and joint leadership that China and the United States have demonstrated on the sidelines of the Group of 20 (G20) summit in fighting climate change have won widespread applause.

Chinese President Xi Jinping (C), U.S. President Barack Obama (R) and Secretary-General of the United Nations Ban Ki-moon attend the deposit of instruments of joining the Paris Agreement in Hangzhou, capital city of east China's Zhejiang Province, Sept. 3, 2016. (Xinhua/Li Tao)

At a meeting between Chinese President Xi Jinping, U.S. President Barack Obama and UN Secretary-General Ban Ki-Moon on the eve of the G20 Hangzhou summit, both China and the United States formally ratified the climate change agreement.

In the eyes of some environmental experts, it is time for European countries as well as the European Union (EU) to follow suit.

As a result, the early entry into force of the Paris Agreement, which was seen as an inconceivable task a short few months ago, is now close to reality, said Li Shuo, senior global policy advisor of Greenpeace East Asia.

"The rhythm and durability of the new climate regime will be enhanced as a result of it," the expert said, adding: "The G20 outcome strengthens China's climate leadership."

On Dec. 12, 2015, after hard and lengthy bargaining, climate negotiators of 196 parties to the UN conference on climate change in Paris sealed the climate change pact, aiming to reverse the trend of temperature rises mainly caused by carbon emissions.

Jennifer Morgan, executive director of Greenpeace International, urged other countries to endorse the Paris Agreement this year.

"Countries now need to react to the strong call from the G20 to formally join and ratify the Paris Agreement as soon as possible, so that this Agreement can enter into force this year," the expert said.

Meanwhile, on behalf of the Greenpeace, Morgan urged Germany, the G20's next president, to lead by example in the year before its G20 presidency to show the world that it is ready to transform its full economy to be zero carbon and shift the investments needed to do so.

As the world's two largest economies, China and the United States together account for 39 percent of global emissions, while the Paris pact still lacks the support of 55 nations that account for 55 percent of global greenhouse gas emissions.

Christoph Bals, policy director at Germanwatch said the ratification increased the pressure for all EU governments to follow suit if they don't want to be left out.

Bals commended China for putting the implementation of the Paris Agreement and the greening of the financial system on the G20 agenda, adding that it is now up to the German presidency next year to deliver concrete implementation strategies on these issues.

Celia Gautier, international and EU policy advisor at Climate Action Network, said France can play an active role in the coming months to convince other G20 countries to make climate-risk disclosure mandatory for all investments, and to introduce climate stress tests for companies.

"France can rely on its own experience, since it made climate-risk disclosure and reporting mandatory in 2015. Secondly, France should join the U.S., China, Germany and others in the reform and peer review process of their public support to fossil fuels, and phase out its harmful subsidies by 2020," Gautier said.

Ruth Davis, senior associate of the London-based organization Third Generation Environmentalism (E3G), said it is the perfect moment for Theresa May to show that Britain will not be left behind, economically or diplomatically, by this new reality.

"As well prompt UK ratification of the Paris Agreement, top of her agenda should be confirming a date for phasing out the UK's remaining coal-fired power stations and setting out an ambitious industrial strategy that will enable UK firms to take advantage of rapidly expanding clean technology markets," Davis said.

As a business leader, Jill Duggan, director of Prince of Wales's Corporate Leaders Group, said strong signals from the G20 governments are important for businesses to act.

"With such a signal the private sector will respond and unlock the creative innovation needed to solve the climate crisis," the expert said.

Duggan stressed that businesses and policymakers alike need to stop thinking incrementally, but focus on delivering the innovative solutions needed to lift the society into the next era.

"The shift to a more sustainable global economy will be the most capital intensive transition in human history," said Ben Caldecott, director of the Sustainable Finance Programme at the University of Oxford Smith School of Enterprise and the Environment.

"The G20 is right to focus on how to mobilize the finance required, and we warmly welcome the work produced jointly by the Bank of England and the People's Bank of China on green finance. It is important that this work accelerates under the G20 in Germany," he added.