Changes in Earth's Reflectance over the past Two Decades Pallé, E.; Goode, P. R.; Montañés-Rodríguez, P. ...
Science (American Association for the Advancement of Science),
05/2004, Letnik:
304, Številka:
5675
Journal Article
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We correlate an overlapping period of earthshine measurements of Earth's reflectance (from 1999 through mid-2001) with satellite observations of global cloud properties to construct from the latter a ...proxy measure of Earth's global shortwave reflectance. This proxy shows a steady decrease in Earth's reflectance from 1984 to 2000, with a strong climatologically significant drop after 1995. From 2001 to 2003, only earthshine data are available, and they indicate a complete reversal of the decline. Understanding how the causes of these decadal changes are apportioned between natural variability, direct forcing, and feedbacks is fundamental to confidently assessing and predicting climate change.
The Earth's albedo is a fundamental climate parameter for understanding the radiation budget of the atmosphere. It has been traditionally measured not only from space platforms but also from the ...ground for 16 years from Big Bear Solar Observatory by observing the Moon. The photometric ratio of the dark (earthshine) to the bright (moonshine) sides of the Moon is used to determine nightly anomalies in the terrestrial albedo, with the aim of quantifying sustained monthly, annual, and/or decadal changes. We find two modest decadal scale cycles in the albedo, but with no significant net change over the 16 years of accumulated data. Within the evolution of the two cycles, we find periods of sustained annual increases, followed by comparable sustained decreases in albedo. The evolution of the earthshine albedo is in remarkable agreement with that from the Clouds and the Earth's Radiant Energy System instruments, although each method measures different slices of the Earth's Bond albedo.
Key Points
We presente a new 16 year long global albedo record (a fundamental climate parameter) taken using the earthshine methodolgy
The Earth's reflectance presents decadal variability, but overall no long‐term trend is identified
The new data seem to agree well with the only other available albedo data set, the one from CERES instrumentation
Getting serious about biofuels Koonin, Steven E
Science (American Association for the Advancement of Science),
2006-Jan-27, 2006-01-27, 20060127, Letnik:
311, Številka:
5760
Journal Article
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The world is now seriously revisiting Rudolf Diesel's vision of using vegetable oils as fuel, driven by surging global oil demand, the geographical concentration of known petroleum reserves, the ...increasing costs of finding and producing new reserves, and growing concerns about atmospheric greenhouse gas (GHG) concentrations. To realize the goal of supplying 30% of global fuel demand, so-called advanced biofuels must be developed from dedicated energy crops, separately and distinctly from food involving a multidisciplinary task for scientists from all disciplines working to integrate and optimize several currently disjoint activities.
COP9 signalosome (CSN) cleaves the ubiquitin-like protein Nedd8 from the Cul1 subunit of SCF ubiquitin ligases. The Jab1/MPN domain metalloenzyme (JAMM) motif in the Jab1/Csn5 subunit was found to ...underlie CSN's Nedd8 isopeptidase activity. JAMM is found in proteins from archaea, bacteria, and eukaryotes, including the Rpn11 subunit of the 26S proteasome. Metal chelators and point mutations within JAMM abolished CSN-dependent cleavage of Nedd8 from Cul1, yet had little effect on CSN complex assembly. Optimal SCF activity in yeast and both viability and proper photoreceptor cell (R cell) development in Drosophila melanogaster required an intact Csn5 JAMM domain. We propose that JAMM isopeptidases play important roles in a variety of physiological pathways.
We report spectroscopic observations of the earthshine reflected from the Moon. By applying our well-developed photometry methodology to spectroscopy, we are able to precisely determine the Earth's ...reflectance and its variation as a function of wavelength through a single night as the Earth rotates. These data imply that planned regular monitoring of earthshine spectra will yield valuable new inputs for climate models, which would be complementary to those from the more standard broadband measurements of satellite platforms. For our single night of reported observations, we find that Earth's albedo decreases sharply with wavelength from 500 to 600 nm, while being almost flat from 600 to 900 nm. The mean spectroscopic albedo over the visible is consistent with simultaneous broadband photometric measurements. Unlike previous reports, we find no evidence for either an appreciable "red" or "vegetation" edge in the Earth's spectral albedo, or for changes in this spectral region (700-740 nm) over the 40 of Earth's rotation covered by our observations. Whether or not the absence of a vegetation signature in disk-integrated observations of the Earth is a common feature awaits the analysis of more earthshine data and simultaneous satellite cloud maps at several seasons. If our result is confirmed, it would limit efforts to use the red edge as a probe for Earth-like extrasolar planets. Water vapor and molecular oxygen signals in the visible earthshine, and carbon dioxide and methane in the near-infrared, are more likely to be powerful probes.
We have been making sustained observations of the earthshine from Big Bear Solar Observatory in California since late 1998. We also have intermittent observations from 1994–1995. We have ...reinvigorated and modernized a nearly forgotten way of measuring the Earth's albedo, and hence its energy balance, previously studied by A. Danjon and his followers for about 25 years early in the last century using their observations of the earthshine from France. This is the first in a series of papers covering observations and simulations of the Earth's reflectance from photometric and spectral observations of the Moon. Here, we develop a modern method of measuring, instantaneously, the large‐scale reflectance of the Earth. From California we see the Moon reflecting sunlight from the third of the Earth to the west of us in our evening (before midnight, which is during the Moon's rising phase) and from the third of the Earth to our east in our morning (after midnight, which is during the Moon's declining phase). We have precisely measured the scattering from the Moon as a function of lunar phase, which enables us to measure, in a typical night's observations, the Earth's reflectance to an accuracy of 2.0% (equivalent to measuring the Earth's emission temperature to ∼0.8 K). We have also identified the lunar phase function as the major source of discrepancy between Danjon's estimates of the albedo and more recent measurements. The albedo is due to the interplay of cloud cover and different landscapes.
The reflectance of the Earth is a fundamental climate parameter that we measured from Big Bear Solar Observatory between 1998 and 2017 by observing the earthshine using modern photometric techniques ...to precisely determine daily, monthly, seasonal, yearly and decadal changes in terrestrial albedo from earthshine. We find the inter‐annual fluctuations in albedo to be global, while the large variations in albedo within individual nights and seasonal wanderings tend to average out over each year. We measure a gradual, but climatologically significant ∼0.5 W/m2 decline in the global albedo over the two decades of data. We found no correlation between the changes in the terrestrial albedo and measures of solar activity. The inter‐annual pattern of earthshine fluctuations are in good agreement with those measured by CERES (data began in 2001) even though the satellite observations are sensitive to retroflected light while earthshine is sensitive to wide‐angle reflectivity. The CERES decline is about twice that of earthshine.
Plain Language Summary
The net sunlight reaching the Earth's climate system depends on the solar irradiance and the Earth's reflectance (albedo). We have observed earthshine from Big Bear Solar Observatory to measure the terrestrial albedo. For earthshine we measure the sunlight reflected from Earth to the dark part of the lunar face and back to the nighttime observer, yielding an instantaneous large‐scale reflectance of the Earth. In these relative measurements, we also observe the sunlit, bright part of the lunar face. We report here reflectance data (monthly, seasonal and annual) covering two decades, 1998–2017. The albedo shows a decline corresponding to a net climate forcing of about 0.5 W/m2. We find no correlation between measures of solar cycle variations and the albedo variations. The first precise satellite measures of terrestrial albedo came with CERES. CERES global albedo data (2001‐) show a decrease in forcing that is about twice that of earthshine measurements. The evolutionary changes in albedo motivate continuing earthshine observations as a complement to absolute satellite measurements, especially since earthshine and CERES measurements are sensitive to distinctly different parts of the angular reflectivity. The recent drop in albedo is attributed to a warming of the eastern pacific, which is measured to reduce low‐lying cloud cover and, thereby, the albedo.
Key Points
We report on two decades of earthshine measurements of the earth's reflectance made from Big Bear Solar Observatory yielding a large‐scale terrestrial albedo
We find a decline in albedo between 1998 and 2017, corresponding to a radiative increase of 0.5 W/m2, which is climatologically significant
The CERES data show the same behavior, which is attributed to a reversal of the Pacific Decadal Oscillation reducing the Earth's albedo
Since late 1998, we have been making sustained measurements of the Earth's reflectance by observing the earthshine from Big Bear Solar Observatory. Further, we have simulated the Earth's reflectance ...for both the parts of the Earth in the earthshine and for the whole Earth. The simulations employ scene models of the Earth from the Earth Radiation Budget Experiment, simulated snow/ice cover, and near‐real‐time satellite cloud cover data. Broadly, the simulations and observations agree; however, there are important and significant differences, with the simulations showing more muted variations. During the rising phase of the Moon we measure the sunlit world to the west of California, and during the declining lunar phase we measure the sunlit world to the east. Somewhat surprisingly, the one third of the Earth to the west and that to the east have very similar reflectances, in spite of the fact that the topographies look quite different. The part to the west shows less stability, presumably because of the greater variability in the Asian cloud cover. We find that our precision, with steady observations since December 1998, is sufficient to detect a seasonal cycle. We have also determined the annual mean albedos both from our observations and from simulations. To determine a global albedo, we integrate over all lunar phases. Various methods are developed to perform this integration, and all give similar results. Despite sizable variation in the reflectance from night to night and from season to season (which arises from changing cloud cover), we use the earthshine to determine annual albedos to better than 1%. As such, these measurements are significant for measuring climate variation and are complementary to satellite determinations.
A sensitive protein-fold recognition procedure was developed on the basis of iterative database search using the PSI-BLAST program. A collection of 1193 position-dependent weight matrices that can be ...used as fold identifiers was produced. In the completely sequenced genomes, folds could be automatically identified for 20%-30% of the proteins, with 3%-6% more detectable by additional analysis of conserved motifs. The distribution of the most common folds is very similar in bacteria and archaea but distinct in eukaryotes. Within the bacteria, this distribution differs between parasitic and free-living species. In all analyzed genomes, the P-loop NTPases are the most abundant fold. In bacteria and archaea, the next most common folds are ferredoxin-like domains, TIM-barrels, and methyltransferases, whereas in eukaryotes, the second to fourth places belong to protein kinases, beta-propellers and TIM-barrels. The observed diversity of protein folds in different proteomes is approximately twice as high as it would be expected from a simple stochastic model describing a proteome as a finite sample from an infinite pool of proteins with an exponential distribution of the fold fractions. Distribution of the number of domains with different folds in one protein fits the geometric model, which is compatible with the evolution of multidomain proteins by random combination of domains. Fold predictions for proteins from 14 proteomes are available on the World Wide Web at. The FIDs are available by anonymous ftp at the same location.
The genomic RNA of human astrovirus was sequenced and found to contain 6797 nt organized into three open reading frames (1a, 1b, and 2). A potential ribosomal frameshift site identified in the ...overlap region of open reading frames 1a and 1b consists of a "shifty" heptanucleotide and an RNA stem-loop structure that closely resemble those at the gag-pro junction of some retroviruses. This translation frameshift may result in the suppression of in-frame amber termination at the end of open reading frame 1a and the synthesis of a nonstructural, fusion polyprotein that contains the putative protease and RNA-dependent RNA polymerase. Comparative sequence analysis indicated that the protease and polymerase of astrovirus are only distantly related to the respective enzymes of other positive-strand RNA viruses. The astrovirus polyprotein lacks the RNA helicase domain typical of other positive-strand RNA viruses of similar genome size. The genomic organization and expression strategy of astrovirus, with the protease and the polymerase brought together by predicted frameshift, most closely resembled those of plant luteoviruses. Specific features of the sequence and genomic organization support the classification of astroviruses as an additional family of positive-strand RNA viruses, designated Astroviridae.
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