The Paris Agreement aims to limit global warming to well below 2°C. Meeting this goal requires robust estimates of past, present and future sources and sinks of the major greenhouse gases (CO2, CH4 and N2O). Translating the temperature target into allowable emissions depends on how land and ocean sinks respond to future change. For this, accurate present-day fluxes at national to global scales are needed to track progress towards Nationally Determined Contributions (NDCs) and to detect emerging changes early, such as a weakening of natural sinks. Observations of past and present fluxes, in turn, constrain projections of their future evolution. Yet all of these remain limited by large uncertainties in observing and modelling GHG fluxes from regional to global scales. Quantifying the transient response to emissions and the magnitude of remaining GHG budgets requires a substantial improvement in our ability to estimate the budgets and trends of major greenhouse gases across all spatio-temporal scales.

This session aims to bring together studies to help understand and quantify past, present, and future global and regional GHG budgets in the atmosphere, the ocean, and on land, as well as processes controlling their trends and variability.

We welcome contributions using a variety of approaches, such as (national) emissions inventories, field and remotely sensed observations, terrestrial and ocean biogeochemical modeling, Earth system modeling, and inverse modeling. We encourage contributions integrating different datasets and approaches at multiple spatial (regional to global) and temporal scales (diurnal, seasonal, interannual variability and long-term trends) that provide new insights on processes influencing GHG budgets and trends in the past, present and future.