Negotiators from around the world have gathered in Bonn, Germany, to resume work on implementing the Paris Agreement, making this an opportune moment to recap progress to date and highlight some of the challenges ahead.

Negotiators last gathered in December at COP 24 in Katowice, Poland, where they adopted the ‘rulebook’ for implementing the Paris Agreement – the most significant step in the global climate effort since the 2015 Paris summit. (C2ES has just published a short guide to the agreement and rulebook, summarizing parties’ obligations and provisions addressing accountability and ambition.)

If you saw photos of Michał Kurtyka, the president of COP 24, literally leaping off the podium with a huge grin on his face, you’d be forgiven for the impression that the entire rulebook was wrapped up in Katowice. In fact, one major piece was left undone.

Parties couldn’t come to agreement and on the detailed rules for implementing Article 6 of Paris, which addresses carbon markets (see our recent brief on Article 6 issues). The central challenge is devising accounting rules for transfers of emission credits among parties that will facilitate trading while ensuring strong environmental integrity. Finishing up these rules is high on the agenda at COP 25, taking place December 2-13 in Santiago, Chile.

Apart from finishing up the Paris rulebook, the major focus of the global effort over the coming months is strengthening momentum for more ambitious national commitments.

The Paris parties all put forward their initial nationally determined contributions (NDCs) upon formally adopting the agreement. The next round of new or updated NDCs is due in 2020. Parties already are or soon will be in the process of revisiting their targets and their domestic policies to see where they stand and how they can do more. A global movement of youth climate demonstrations as well as increased climate litigation are pressuring parties to raise their climate ambition.

UN Secretary General António Guterres will host a Climate Summit in New York City on September 23, and is urging world leaders to bring “concrete, realistic plans” to enhance their NDCs—not speeches. As many as 80 countries have already indicated that they want to increase their climate pledges ahead of schedule.

The release this fall of the Intergovernmental Panel on Climate Change’s next special report on the ocean and cryosphere will likely provide additional urgency. Chile has declared COP 25 a “Blue COP,” hoping to highlight the role of oceans in absorbing vast amounts of carbon dioxide and the negative impacts on ocean ecosystems that this is causing.

Meantime, expectations are high that President Trump will soon follow through on his promise to withdraw the United States from the Paris Agreement. Under the terms of the agreement, the earliest a withdrawal notice could be formally submitted is November 4. It would become effective one year later on November 4, 2020 – one day after the presidential election. The House of Representatives recently passed the Climate Action Now Act to keep the administration from leaving the agreement, but the Senate is unlikely to follow suit.

Yet even as some climate leadership falters, others– countries, states, cities, businesses, and ordinary citizens–are stepping in to fill that gap. At a Vatican conference last week, for instance, top representatives of oil and gas companies and major investment firms endorsed carbon pricing and stronger corporate disclosure of climate-related risks.

Hopefully, these and similar efforts will help ensure success at COP 24 and give governments the confidence they need to significantly ramp up ambition in the months ahead.