Secretary of State John Kerry, ever the diplomat, sure knows how to melt our cold hearts on Earth Day. Representatives from 175 countries marked the occasion with a formal signing ceremony of the Paris climate agreement at the United Nations. In an event featuring a sea of green ties, Kerry made a different kind of symbolic statement, holding his 2-year-old granddaughter Isabelle as he signed the agreement.

The ceremony is only a first step to seeing the Paris agreement enter into force. Fifty-five countries representing at least 55 percent of global emissions still need to ratify the agreement, which the U.S. and China (the two biggest emitters) plan on doing this year. Even once it’s ratified, there’s a lot of work left to be done. Top U.S. climate negotiator Todd Stern told Grist in an interview, “the most important thing is what countries do nationally” to make their needed emissions cuts.