The top two biggest carbon emitters in the world are taking the lead to successfully realize the Paris climate change accord earlier than its most optimistic projections.

Over 150 governments including 40 leaders are expected to attend and sign up to the Paris Agreement that addresses climate change at the United Nations on Friday (April 22), marking the biggest one-day signing of any international agreement in history.

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But beyond the mere signing, state leaders will be looking at which countries will honor the promises they made in Paris last December to keep global warming below the agreed 2C target.

So far, a handful of nations including China, Canada and the United States have committed to join the force this year, boosting hopes that the Paris deal will be implemented three to four years earlier than its actual 2020 target date, experts said.

"It's likely it could come into effect in 2017. It could even happen this year," said Eliza Northrop, a World Resource Institute analyst.

If the timeline will be accelerated, environment ministers said the faster pace shows how seriously committed the state leaders are. Furthermore, it could also possibly help attain a more ambitious aim of limiting warming to 1.5C, which would likely give smaller islands and other nations a higher chance of survival.

"We can't just now rest on our laurels and have a nice signing on Earth Day, and then we all go home," Catherine McKenna, environment and climate change minister from Canada, told a panel from World Bank last week. "Early entry into force - we are very committed to making that happen."

Tagschina, United States, Paris Agreement, Climate Change, Carbon emission, United Nations