Search

Observations of C[O.sub.2] and [O.sub.2] are interpreted to develop an understanding of the changes in the abundance of atmospheric C[O.sub.2] that have arisen over the period 1995-2007. Fossil fuels accounted for an addition of 89.3 Gt of carbon to the atmosphere over this time period, 29° of which was transferred to the ocean, 15° to the global biosphere, with the balance (57°) retained by the atmosphere. Analysis of historical data for C[O.sub.2] derived from studies of gases trapped in ice at Law Dome in Antarctica indicate that the biosphere represented a net source of atmospheric C[O.sub.2] prior to 1940, switching subsequently to a net sink. PACS No.: 92.60Hp Nous analysons les observations qui ont ete faites sur les molecules de C[O.sub.2] et de [O.sub.2], afin de mieux comprendre les changements d'abondance du C[O.sub.2] atmospherique qui sont survenus entre 1995 et 2007. Les carburants fossiles ont ajoute 89,3 Gt de carbone a l'atmosphfere pendant cette periode, dont 29° ont ete transfers aux oceans, et 15° a la biosphere, alors que 57° restaient dans l'atmosphfere. L'analyse des donnees historiques sur le C[O.sub.2], obtenues des gaz captifs dans la glace a Law Dome en Antarctique, revele que la biosphere a represente une source nette de C[O.sub.2] avant 1940 et qu'elle en est devenue un piege net depuis. [Traduit par la Redaction], 1. Introduction The bulk of the Earth's carbon resides in sediments. The ocean ranks number two, followed by soils, the biosphere, and the atmosphere. The concentration of C[O.sub.2] in the [...]

The potential of wind power as a global source of electricity is assessed by using winds derived through assimilation of data from a variety of meteorological sources. The analysis indicates that a network of land-based 2.5-megawatt (MW) turbines restricted to non-forested, ice-free, nonurban areas operating at as little as 20% of their rated capacity could supply >40 times current worldwide consumption of electricity, >5 times total global use of energy in all forms. Resources in the contiguous United States, specifically in the central plain states, could accommodate as much as 16 times total current demand for electricity in the United States. Estimates are given also for quantities of electricity that could be obtained by using a network of 3.6-MW turbines deployed in ocean waters with depths

Americans' annual consumption of gasoline (for both private and commercial transportation) amounts to more than 140 billion gallons--close to 500 gallons for every man, woman, and child in the country. [...]

Wind offers an important alternative to coal as a source of energy for generation of electricity in China with the potential for substantial savings in carbon dioxide emissions. Wind fields derived from assimilated meteorological data are used to assess the potential for wind-generated electricity in China subject to the existing government-approved bidding process for new wind farms. Assuming a guaranteed price of 0.516 RMB (7.6 U.S. cents) per kilowatt-hour for delivery of electricity to the grid over an agreed initial average period of 10 years, it is concluded that wind could accommodate all of the demand for electricity projected for 2030, about twice current consumption. Electricity available at a concession price as low as 0.4 RMB per kilowatt-hour would be sufficient to displace 23% of electricity generated from coal

INTRODUCTION WE LIVE AT A UNIQUE POINT in the history of planet Earth. After almost four billion years of evolution, a single species, Homo sapiens sapiens, has evolved with the [...]

Changing Composition of the Global Stratosphere OZONE IS FORMED IN THE STRATOSPHERE BY PHOTOLYSIS of O.sub.2 to atomic oxygen (O), hv + O.sub.2 → O + O (1) followed by [...]

Stable carbon isotope ratios ([[Delta].sup.13]C) in extant plants can discriminate between [C.sub.3], [C.sub.4], and CAM photosynthesis, estimate water-use efficiency, and detect carbon cycle variations. In fossil plants [[Delta].sup.13]C is typically measured in untreated leaf carbon, which is used to reconstruct the [[Delta].sup.13]C of living tissue. Living plant tissue is a mixture of different chemical components such as cellulose, lignin, and lipids, which differ from each other in their [[Delta].sup.13]C. The ratio of cellulose, lignin, and lipids is altered during fossilization through partial anaerobic decay and thermal maturation, which increase the abundance of isotopically light lignin and cutin relative to isotopically heavy cellulose, Reconstructions of [[Delta].sup.13]C in a fossil can be 5% to 6% too negative if the fossil material consists solely of lignin. Carbon isotope ratios in extant and fossil plant cuticle indicate that isolation of a pure cuticle fraction can overcome biases introduced by fossilization. The [[Delta].sup.13]C of extant angiosperm and gymnosperm cuticle is 3-3.5% more negative than the [[Delta].sup.13]C of whole tissue, an offset that is consistent for [C.sub.3], [C.sub.4], and CAM species. Estimating whole-tissue [[Delta].sup.13]C from cuticle [[Delta].sup.13]C in extant plants has an error of approximately [+ or -]1%, significantly less than the potential error caused by loss of cellulose during fossilization. Comparison of [[Delta].sup.13]C in untreated leaf carbon and cuticle macerated from the same fossil indicates significant loss of cellulose in some fossil specimens. Carbon isotopic differences between [C.sup.3] and [C.sup.4] plants are sufficiently large to be detected in either untreated fossil carbon or cuticle. However, finer-scale differences in fossil-plant [[Delta].sup.13]C, such as those resulting from differences in water-use efficiency or variations in atmospheric C[O.sub.2], probably require the analysis of cuticle for unambiguous detection.