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Methanol is a biogeochemically active compound and a significant component of the volatile organic carbon in the atmosphere. It influences background tropospheric photochemistry and may serve as a tracer for biogenic emissions. The mass of methanol in the atmospheric reservoir, the annual mass flux of methanol from sources to sinks, and the estimated atmospheric lifetime of methanol in the free troposphere, marine boundary layer, continental boundary layer, and in-cloud, are evaluated. The atmosphere contains approximately 4 Tg (terragrams, 1012 g) of methanol. Estimates of global methanol sources and sinks total 340 and 270 Tg methanol yr-1, respectively, and are in balance given their estimated precision. Sink terms were evaluated using observed methanol distributions; the total loss is approximately a factor of 5 larger than prior estimates. The adopted source is a factor of 3 larger than its prior estimate. Recent net flux observations and the magnitude of the estimated sink suggest biogenic methanol emissions to be near their current estimated upper limit, >280 Tg methanol yr-1, and this value was adopted. The methanol source will be larger with the inclusion of an argued for oceanic gross emission of 30 Tg methanol yr-1, but a major uncertainty concerns whether the oceans are a major net sink or source of methanol, an issue which will not be resolved without new measurements. Other large uncertainties are the estimates of primary biogenic emissions and gas surface deposition. The first loss estimates of methanol by in-cloud chemistry and precipitation are presented. They are approximately equal at 10 Tg methanol yr-1, each. These are small in comparison to the surface loss and gas phase photochemical loss estimated here but would be significant additional losses in earlier budgets. Surface exchange processes dominate the atmospheric budget of methanol and its distribution. The atmospheric deposition of methanol and the argued for methanol produced in the upper ocean are ubiquitous sources of C1 substrate capable of sustaining methylotrophic organisms throughout the surface ocean.

If published estimates of S[O.sub.2] volatilization and N[O.sub.x] generation by the Cretaceous-Tertiary (K-T) impact were atmospherically converted to sulfuric and nitric acid, globally dispersed, and rapidly rained out, the resulting acid concentrations would bracket a critical threshold in surface-ocean chemistry. Rapid and globally uniform deposition of masses corresponding to the lowest estimates would have had no major effect on sea-surface chemistry. However, similar deposition of masses corresponding to the highest estimates would have provided enough acid to destroy the carbonate-buffering capacity of the upper 100 m of the world ocean and catastrophically reduce surface-ocean pH. Despite the possible effect of the highest estimated acid yields, scenarios that rely on acid rain as the primary explanation of global K-T extinctions are not readily compatible with K-T records of terrestrial and marine survival or culturing studies of modern marine plankton. The possibility that acid rain was a primary cause of K-T extinctions can be tested further by analysis of geographic variation in extinction intensity, because such variation was a likely consequence if the impact resulted in global dispersal and rapid globally uniform deposition of more than [approximately] 6 X [10.sup.16] mol of [H.sub.2]S[O.sub.4] or 1.2 X [10.sup.17] mol of HN[O.sub.3].

The nine-word sentence 'we are evaporating our coal mines into the air', often used to introduce or illustrate discussions of the anthropogenic production of carbon dioxide from fossil fuels in the context of its effect on the Earth's climate is credited to Svante Arrhenius. It is argued that he was not the original author of the sentence and it was the work of four separate individuals.