You see headlines like this:

China ratifies Paris climate change agreement ahead of G20

Not so. The National People’s Congress of China has voted to ratify as it was jolly well told to, but that’s not ratification yet. International law is clear on this. The Vienna Convention on the Law of Treaties of 23 May 1969, which codified long-standing practice, says this:

Article 16.
Exchange or deposit of instruments of ratification, acceptance, approval or accession

Unless the treaty otherwise provides, instruments of ratification, acceptance, approval or accession establish the consent of a State to be bound by a treaty upon:

(a) their exchange between the contracting States; (b) their deposit with the depositary; or (c) their notification to the contracting States or to the depositary, if so agreed.

So China or the USA or Vanuatu ratify the treaty when the paperwork is handed over to the Treaty Section of the UN Office of Legal Affairs, and not before. To be helpful to John Kerry, here is the address:

Mr. Santiago Villalpando, Chief of Treaty Section
United Nations Headquarters
Room No. DC2-0520
United Nations Headquarters
New York, NY 10017

I don’t know if he has a bottle of sherry for visitors.

Update, same day: It looks as if both Chinese and American diplomats found Mr. Villalpando without my help. Press release from the UNFCC secretariat:

Both countries have announced they have deposited their instruments of ratification with the UN Secretary-General.

So the Agreement has in one day jumped from 24 parties representing 1% of emissions to 26 parties representing 39% of global emissions. It needs 55 and 55%. Both targets should be hit before the end of the year. November would be nice, as entry into force by the end of the year would lock a hypothetical President Trump into the agreement for his entire first term of office (Article 28). The USA would still stop contributing, but the chair would sit empty.