Reconstructing past climate from noisy data

Empirical reconstructions of the Northern Hemisphere (NH) temperature in the past millennium based on multiproxy records depict small-amplitude variations followed by a clear warming trend in the past two centuries. We use a coupled atmosphere-ocean model simulation of the past 1000 years as a surrogate climate to test the skill of these methods, particularly at multidecadal and centennial time scales. Idealized proxy records are represented by simulated grid-point temperature, degraded with statistical noise. The centennial variability of the NH temperature is underestimated by the regression-based methods applied here, suggesting that past variations may have been at least a factor of 2 larger than indicated by empirical reconstructions.     

Comment on "Reconstructing past climate from noisy data"

von Storch et al. (Reports, 22 October 2004, p. 679) criticized the ability of the "hockey stick" climate field reconstruction method to yield realistic estimates of past variation in Northern Hemisphere temperature. However, their conclusion was based on incorrect implementation of the reconstruction procedure. Calibration was performed using detrended data, thus artificially removing a large fraction of the physical response to radiative forcing.     

Light scattering in central arctic ocean: some winter profiles

Measurements for light scattering in an Arctic water column reveal strong gradients and variability of the order of 15 percent in depths of less than 500 meters. The region of variability appears to persist from day to day and is roughly associated with the typical hydrographic features of the region. No definite nephelocline was observed.     

Skylab radar altimeter: short-wavelength perturbations detected in ocean surface profiles

Short-wavelength anomalies in sea surface topography, caused by the gravitational effects of major ocean bottom topographic features, have been detected by the radar altimeter aboard Skylab. Some features, such as deep ocean trenches, seamounts, and escarpments, displace the ocean surface by as much as 15 meters over 100-kilometer wavelengths. This experiment demonstrates the potential of satellite altimetry for determining the ocean geoid and for mapping major features of the ocean bottom.     

Tropical pacific forcing of decadal SST variability in the western indian ocean over the past two centuries

A 194-year annual record of skeletal delta(18)O from a coral growing at Malindi, Kenya, preserves a history of sea surface temperature (SST) change that is coherent with instrumental and proxy records of tropical Pacific climate variability over interannual to decadal periods. This variability is superimposed on a warming of as much as 1.3 degrees C since the early 1800s. These results suggest that the tropical Pacific imparts substantial decadal climate variability to the western Indian Ocean and, by implication, may force decadal variability in other regions with strong El Nino-Southern Oscillation teleconnections.     

建立可持续发展的有机农业

现代农业是在传统农业中孕育、发生的。现代农业的生产经历了由量变到质变的过程 ,至 2 0世纪6 0年代 ,现代农业基本确立。在传统农业向现代农业过渡阶段中 ,最大的变化之一是 ,化肥的研制成功和广泛应用促进了作物单产的提高 ,据统计世界粮食增产额中大约有 5 0 %是化肥的贡献     

Modeling ocean circulation

Ocean numerical models have become quite realistic over the past several years as a result of improved methods, faster computers, and global data sets. Models now treat basin-scale to global domains while retaining the fine spatial scales that are important for modeling the transport of heat, salt, and other properties over vast distances. Simulations are reproducing observed satellite results on the energetics of strong currents and are properly showing diverse aspects of thermodynamic and dynamic ocean responses ranging from deep-water production to EI Ni?o. Now models can represent not only currents but also the consequences for climate, biology, and geochemistry over time spans of months to decades. However, much remains to be understood from models about ocean circulation on longer time scales, including the evolution of the dominant water masses, the predictability of climate, and the ocean's influence on global change.     

Reconstructing the origin of Andaman Islanders

The origin of the Andaman "Negrito" and Nicobar "Mongoloid" populations has been ambiguous. Our analyses of complete mitochondrial DNA sequences from Onges and Great Andaman populations revealed two deeply branching clades that share their most recent common ancestor in founder haplogroup M, with lineages spread among India, Africa, East Asia, New Guinea, and Australia. This distribution suggests that these two clades have likely survived in genetic isolation since the initial settlement of the islands during an out-of-Africa migration by anatomically modern humans. In contrast, Nicobarese sequences illustrate a close genetic relationship with populations from Southeast Asia.     

Ethane ocean on titan

It is proposed that Saturn's satellite Titan is covered by an ocean one to several kilometers deep consisting mainly of ethane. If the ocean is in thermodynamic equilibrium with an atmosphere of 3 percent (mole fraction) methane, then its composition is roughly 70 percent ethane, 25 percent methane, and 5 percent nitrogen. Photochemical models predict that ethane is the dominant end product of methane photolysis so that the evolving ocean is both the source and sink for continuing photolysis. The coexisting atmosphere is compatible with Voyager data.     

重塑国有森林资源产权制度

根据产权理论及森林资源的特殊性,界定了国有林区森林资源产权及其制度的基本内涵,指出要从纵横两个方面认识森林资源产权;分析了国有林区森林资源产权的有限多元化、不具有明显的排他性以及国有森林产权制度的成本过高的制度性缺陷;提出了森林资源配置效率是产权制度效率的判断标准;最后设计出在林地及部分公益林资源国有的框架下,实行森林、林木及其他多种资源的所有权、使用权、处置权、收益权的多元化主体的分散产权制度。