UN officials say the signing ceremony tomorrow will set a record for international diplomacy: Never before have so many countries inked an agreement on the first day of the signing period.
That could help pave the way for the pact to become effective long before the original 2020 deadline possibly this year though countries must first formally approve it through their domestic procedures.
The US and China, which together account for nearly 40 per cent of global emissions, have said they intend to formally join the agreement this year. It will enter into force once 55 countries representing at least 55 per cent of global emissions have done so.
"There's incredible momentum," former New Zealand Prime Minister Helen Clark, who heads the UN Development Program, told The Associated Press. "We're moving as quickly as possible to action."
The agreement, the world's response to hotter temperatures, rising seas and other impacts of climate change, was hammered out in December outside Paris.
The pact was a major breakthrough in UN climate negotiations, which for years were bogged down with disputes between rich and poor countries over who should do what to fight global warming.
The mood was so pessimistic after a failed 2009 climate summit in Copenhagen, Denmark, that UN climate chief Christiana Figueres said she thought a global deal wouldn't happen in her lifetime. Now she expects the Paris Agreement to take effect by 2018.
