We present a tractable and transparent approach (the TMSC model) to estimating the total stock of carbon (roots, stems and leaves) in living vegetation (C _living), from gross primary productivity (GPP) estimates. The TMSC model utilises the TMS scheme of canopy functional types and a generic allometric scheme to derive these estimates. Model estimates are presented for the Australian continent under the following three vegetation–[CO₂] scenarios: the present (1988) vegetation and a hypothetical natural (1988) vegetation cover with atmospheric CO₂ concentration ([CO₂]) of 350 µmol mol^–1 (pveg350 and nveg350), and the natural vegetation (1788) having [CO₂] of 280 µmol mol^–1 (nveg280). The change between the nveg280 and pveg350 scenarios represents the combined effects of changes in land use and CO₂. The change resulting from CO₂ alone is the difference between the nveg280 and nveg350 scenarios. The estimated C _living for the continent is 21 Gt for pveg350, 23 Gt for nveg350 and 10 Gt for nveg280. This translates to an averaged rate of increase in C _living (CSI) of about 50 Tg C year^–1 over the last 200 years for the continent. Where wooded areas have been extensively cleared for agriculture, the CSI is negative (down to –4 g C m^–2 year^–1). Elsewhere, the CSI over the last 200 years ranges from ~55 g C m^–2 year^–1 in the tropical and subtropical forests to ~0 g C m^–2 year^–1 in the most arid regions.