Actions should improve scientific understanding in only one of the following areas:

a) Greenhouse gas fluxes and Earth system feedbacks
Actions should target a better understanding of key processes related to the life cycles of GHGs, other climate forcers and associated feedbacks affecting the Earth’s climate over different time horizons, including the effect of climate variability from inter-annual to multi-decadal and longer time scales. Actions should focus on elements of the climate system which have an important influence on climate change and its impacts but are not sufficiently understood by the latest science, such as terrestrial ecosystems, hydrological cycles, ocean circulation changes, atmosphere-ocean gas exchanges, coastal zones or the biogeochemical cycles.

b) Global warming contribution of different, non-CO2 radiative forcers
Actions should improve knowledge concerning the individual and cumulative contribution of short- and long-lived radiative forcers, including GHGs other than CO2 and their precursors, aerosols, refrigerants and other climate forcers, to climate change, including their impact on atmospheric and ocean circulation, as well as other environmental issues. Actions may focus on a subset of forcers, and should concentrate on those where the relationship between emissions, atmospheric lifecycle, climate system feedbacks, and global warming is least well understood. Actions should also assess the climate and non-climate impacts, over multiple time scales, of policies and measures targeting forcers other than CO2. Moreover, the action should examine the application of this knowledge in relevant sectors (such as transport, industry, agriculture and health) with a view to better understand co-benefits and trade-offs of mitigation policies with other societal benefits, including human health.

c) Climate and Earth system responses to climate neutrality and net negative emissions
Actions should improve understanding of the environmental consequences of reducing net greenhouse gas emissions to levels consistent with the aim of stopping global warming. Actions should focus on the response of global temperatures and other key properties of the Earth system to sustained reductions in greenhouse gas emissions to net zero and below. The action should pay particular attention to climate-related challenges at different temporal scales, including potential benefits, risks and feedbacks of using carbon dioxide removal strategies, whether nature-based or technological, to stabilise global temperature.