The figure shows the mean methanol concentrations in surface air and at 500 hPa in January and July simulated with the GEOS-CHEM global model of tropospheric chemistry. Methanol is the second most abundant organic gas in the troposphere and has a number of implications for tropospheric chemistry. We simulated its global distribution to test the consistency between our current understanding of sources and sinks and the growing body of atmospheric methanol observations available from surface sites and aircraft. Global sources of methanol in the model, based on best knowledge of processes, are 128 Tg/yr from plant growth, 38 Tg/yr from atmospheric production by CH₃O₂ radical reactions, 23 Tg/yr from plant decay, 13 Tg/yr from biomass burning and biofuels, and 4 Tg/yr from fossil fuel combustion and industrial activities. Plant growth emissions are a factor of 3 higher for young than for mature leaves. The atmospheric lifetime of methanol against oxidation and deposition in the model is 7 days. Gas-phase oxidation by OH provides 63% of the total sink, dry deposition to land 26%, wet deposition 6%, uptake by the ocean 5%, and aqueous-phase oxidation in clouds less than 1%. The resulting simulation of atmospheric concentrations is generally unbiased in the northern hemisphere, and reproduces the observed correlations of methanol with acetone, HCN, and CO in Asian outflow. Accounting for decreased biogenic emission as leaves mature is critical to successful simulation of the observed seasonal variation of methanol concentrations. The main model discrepancy is over the South Pacific where simulated methanol concentrations are a factor of two too low. Atmospheric production of methanol is the dominant model source in this region. A factor of 2 increase in this source (to 50-100 Tg/yr) would largely correct the model underestimate. Atmospheric constraints imply a likely range of 100-160 Tg/yr for the plant growth source, and a likely range of 5-10 days for the methanol lifetime. Our best estimate of the global source of methanol is 240 Tg/yr. This work was led by Daniel Jacob and Brendan Field; a full account is given in Jacob et al. [2004].