An Expedition to Close Global Carbon Budget: From a Few Surface Flasks to Millions of Satellite Observations and Beyond

On average, about half of the fossil fuel emissions have been absorbed by natural carbon cycle, of which one half has been absorbed by terrestrial biosphere. Where and how these carbon have been absorbed directly link to whether terrestrial biosphere can continue absorbing carbon from the atmosphere at current rate in the future. Pioneered by Tans, Fung, and Takahashi (Science, 1990), atmospheric CO2 observations from a few flask observations in 1990s to millions of satellite observations today have been used to quantify the spatiotemporal distribution of net terrestrial biosphere fluxes. Recently, other types of satellite observations, such as Solar Induced chlorophyll Fluorescence observations and carbon monoxide observations, have been used in combination of CO2 in an attempt to have a more mechanical understanding of underlying processes that control terrestrial biosphere carbon cycle. In the future, plant traits and biomass observations will also be available. In this talk, I will review how atmospheric flux inversion involved from 1990s, what we have learned, and the challenges ahead.