A lesser-known success of the Paris climate agreement in 2015 is the 'global adaptation goal', an ambitious plan for adapting to climate change that reaches beyond national boundaries. This is important because climate-change mitigation needs to take the world's adaptation potential into account.

To sustain the long-term goal of keeping the global average temperature rise well below 2 °C, we also need evidence that the world can adapt to the impacts of warming. The Paris agreement aims to build a collective understanding of adaptation through metrics and tools that capture each country's efforts. Aggregating national contributions as a global trend will indicate whether humankind is on track to adapt.

The first step will be the agreement's ratification in April by at least 55 parties to the United Nations Framework Convention on Climate Change (UNFCCC) — which together account for at least 55% of total greenhouse-gas emissions.

It will next be necessary to define metrics that both reflect national circumstances and allow aggregation. To this end, scientists tracking adaptation will need to work with experts at the UNFCCC and organizations such as the UN Environment Programme.