Atmospheric News
NCAR Scientists Find Global Warming Fueled 2005 Atlantic Hurricanes
Global warming accounted for around half of the extra hurricane-fueling warmth in the waters of the tropical North Atlantic in 2005, while natural cycles were only a minor factor, according to a new analysis by Kevin Trenberth and Dennis Shea of the National Center for Atmospheric Research (NCAR). The study appeared in the 27 June issue of Geophysical Research Letters, published by the American Geophysical Union.
Trenberth and Shea's research focuses on an increase in ocean temperatures. During much of last year's hurricane season, sea-surface temperatures across the tropical Atlantic between 10 and 20 degrees north, which is where many Atlantic hurricanes originate, were a record 1.7 degrees F above the 1901-1970 average. While researchers agree that the warming waters fueled hurricane intensity, they have been uncertain whether Atlantic waters have heated up because of a natural, decades-long cycle, or because of global warming.
By analyzing worldwide data on sea-surface temperatures (SSTs) since the early 20th century, Trenberth and Shea were able to calculate the causes of the increased temperatures in the tropical North Atlantic. Their calculations show that global warming explained about 0.8 degrees F of this rise. Aftereffects from the 2004-05 El Nino accounted for about 0.4 degrees F. The Atlantic multidecadal oscillation (AMO), a 60-to-80-year natural cycle in SSTs, explained less than 0.2 degrees F of the rise, according to Trenberth. The remainder is due to year-to-year variability in temperatures.
Global warming does not guarantee that each year will set records for hurricanes, Trenberth says. He notes that last year's activity was related to very favorable upper-level winds as well as the extremely warm SSTs. Each year will bring ups and downs in tropical Atlantic SSTs due to natural variations, such as the presence or absence of El Nino, says Trenberth. However, he adds, the long-term ocean warming should raise the baseline of hurricane activity.
For more information see http://www.ucar.edu/news/releases
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Study of Climate Models Shows Even Warmer Estimates Likely
As the global warming debate heats up, researchers at George Mason University and the Center for Ocean-Land Atmosphere Studies recently conducted a comprehensive, and somewhat controversial, study that the more reliable climate models tend to project higher estimates of global warming for the next century.
The paper “Climate Model Fidelity and Projections of Climate Change,” which appeared the May Geophysical Research Letters, presents a detailed mathematical analysis of the model simulations prepared for the Intergovernmental Panel on Climate Change. It predicts higher estimates of global warming-- 4 to 5 º C as opposed to the model consensus range of 2 to 4 º C--may be more likely.
This is the first study to relate the ranking of climate model accuracy to their simulations of future climate. In previous studies, the scientific community has been reluctant to evaluate models in relation to one another, but George Mason and COLA scientists have used this comparison to stress an important trend in the current predictions of global warming.
The researchers—Jagadish Shukla, Timothy DelSole, Michael Fennessy, Jim Kinter and Daniel Paolino--looked at the results of 14 current climate models from 10 different premiere laboratories in five countries. The identities of the models in the study were omitted from the paper and are being withheld to avoid promoting or criticizing individual models or modeling groups
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NRC Report on Global Temperature Changes Now Online
There is sufficient evidence from tree rings, boreholes, retreating glaciers, and other "proxies" of past surface temperatures to say with a high level of confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years, according to a new report from the National Research Council. Less confidence can be placed in proxy-based reconstructions of surface temperatures for A.D. 900 to 1600, said the committee that wrote the report, although the available proxy evidence does indicate that many locations were warmer during the past 25 years than during any other 25-year period since 900. Very little confidence can be placed in statements about average global surface temperatures prior to A.D. 900 because the proxy data for that time frame are sparse, the committee added.
The report was requested by Congress after a controversy arose last year over surface temperature reconstructions published by climatologist Michael Mann and his colleagues in the late 1990s. The researchers concluded that the warming of the Northern Hemisphere in the last decades of the 20th century was unprecedented in the past thousand years. In particular, they concluded that the 1990s were the warmest decade, and 1998 the warmest year. Their graph depicting a rise in temperatures at the end of a long era became known as the "hockey stick."
The Research Council committee found the Mann team's conclusion that warming in the last few decades of the 20th century was unprecedented over the last thousand years to be plausible, but it had less confidence that the warming was unprecedented prior to 1600; fewer proxies -- in fewer locations -- provide temperatures for periods before then. Because of larger uncertainties in temperature reconstructions for decades and individual years, and because not all proxies record temperatures for such short timescales, even less confidence can be placed in the Mann team's conclusions about the 1990s, and 1998 in particular.
The committee noted that scientists' reconstructions of Northern Hemisphere surface temperatures for the past thousand years are generally consistent. The reconstructions show relatively warm conditions centered around the year 1000, and a relatively cold period, or "Little Ice Age," from roughly 1500 to 1850. The exact timing of warm episodes in the medieval period may have varied by region, and the magnitude and geographical extent of the warmth is uncertain, the committee said. None of the reconstructions indicates that temperatures were warmer during medieval times than during the past few decades, the committee added.
The scarcity of precisely dated proxy evidence for temperatures before 1600, especially in the Southern Hemisphere, is the main reason there is less confidence in global reconstructions dating back further than that. Other factors that limit confidence include the short length of the instrumental record, which is used to calibrate and validate reconstructions, and the possibility that the relationship between proxy data and local surface temperatures may have varied over time. It also is difficult to estimate a mean global temperature using data from a limited number of sites. On the other hand, confidence in large-scale reconstructions is boosted by the fact that the proxies on which they are based generally exhibit strong correlations with local environmental conditions. Confidence increases further when multiple independent lines of evidence point to the same general phenomenon, such as the Little Ice Age.
Copies of Surface Temperature Reconstructions for the Last 2,000 Years are available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at http://www.nap.edu. The report is also available at http://national-academies.org
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Aviation Weather Stations Delivered to Sweden and Poland
Coastal Environmental Systems, Inc. has just completed delivery of its Tactical Aviation Weather Stations to the countries of Sweden and Poland. The stations can be rapidly transported and set-up in the battlefield and report back to the command post via a license free radio (5-7 miles). These stations are designed specifically to meet the demands of tactical military use. According to the manufacturer, the systems are rugged, accurate, reliable, and able to withstand the rigors associated with military missions and deployments for many years. The U.S. Navy, U.S. Air Force, NWS, FAA, and Swedish, French, Polish, Mexican and Peruvian Militaries all rely on Coastal Environmental Systems’ Aviation Weather Stations for their weather data and reporting needs.
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New Spacecraft Will Study Sun’s Interaction with Radiation Belts
The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., will develop and operate twin NASA spacecraft to study how the sun interacts with Earth’s radiation belts.
Part of NASA’s Living With a Star Program, the Radiation Belt Storm Probes (RBSP) mission will determine how varying inputs of solar energy form or change populations of relativistic electrons and ions in the Earth’s radiation belts -- the doughnut-shaped bands of charged particles trapped by Earth’s magnetic field that extend some 20,000 miles around our planet. After launch, scheduled for 2012, the RBSP spacecraft will measure the distributions of charged particles as well as the electric and magnetic fields that energize, transport or remove the particles within these belts.
Detailed design of the probes will begin this summer, after NASA selects the spacecraft’s science instruments. The mission’s science results will provide the understanding needed to predict potentially hazardous space weather effects, much in the same way we forecast weather on Earth. Furthermore, observations from the spacecraft will be used to improve the characterization of planetary space environments. Increased knowledge of the space environment and effects of space weather will permit better design and operations of new technology on Earth and in space.
For more information on the program, visit http://lws.gsfc.nasa.gov
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NASA and NSF Computers Simulate Sun’s Corona
NASA researchers have developed a computer simulation that can accurately create a model of the sun's outer atmosphere, or corona. By accurately simulating the behavior of the corona, the scientists hope to eventually predict when it will produce flares and coronal mass ejections, huge clouds of hot plasma ejected from the sun. Such predictions will help protect astronauts against radiation from flares and coronal mass ejections, in addition to mitigating disruptions on orbiting satellites and land-based communications and power systems.
The computer model was based on spacecraft observations of magnetic activity on the sun's surface, which affects and shapes the corona. The observations were made with the Michelson Doppler Imager instrument on the Solar and Heliospheric Observatory (SOHO) spacecraft. The Science Applications International Corporation team released simulated "photographs" of the 29 March total solar eclipse 13 days before and again 5 days before the actual event.
During a total solar eclipse, the moon blocks direct light from the sun, so the much fainter corona is visible. This is the only time the corona is visible from Earth without special instruments, and it resembles a white, lacy veil surrounding the black disk of the moon. Because the corona is always changing, each eclipse looks different.
Since the physics of the corona is still not completely understood, the accuracy of the simulation will improve when our understanding of how energy flows through the corona improves. More detailed measurements of magnetic activity on the solar surface, like those expected from NASA's Solar Dynamics Observatory scheduled to launch in 2008, will also improve the accuracy of the simulation.
For additional information and graphics, visit:
http://www.nasa.gov/vision/universe/solarsystem/corona_telecon.html
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EPA Issues Excessive Heat Events Guidebook
The Environmental Protection Agency has developed an Excessive Heat Events Guidebook that summarizes heat-related health impacts and highlights best practices that can save lives. The guidebook also provides public-assistance options for emergency managers, state and local officials, and meteorologists.
The book is online at http://epa.gov/heatisland/about/heatguidebook.html
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AMS Fellow, NCAR Director Timothy Killeen to Lead American Geophysical Union
Timothy Killeen, AMS Fellow and director of the National Center for Atmospheric Research (NCAR), will begin a two-year term as president of the American Geophysical Union (AGU) on July 1.
Killeen is an expert on atmospheric and space science. As director of NCAR, he has overall responsibility for the organization's scientific, technical, and educational activities. Previously, he was a professor at the University of Michigan, serving as director of the university's Space Physics Research Laboratory. He holds a Ph.D. in atomic and molecular physics from University College London.
The American Geophysical Union is a worldwide scientific research community that works to advance our understanding of the four fundamental areas of geophysics: atmospheric and ocean sciences, solid-Earth sciences, hydrologic sciences, and space sciences. The organization serves its membership of more than 45,000 with a range of publications, meetings, and educational activities that support research in Earth and space sciences.
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AMS Fellow Lennart Bengtsson Wins Prestigious IMO Prize
AMS Fellow and Professor Lennart Bengtsson has won the 51st IMO Prize for his pioneering research in numerical weather prediction. Prof. Bengtsson has contributed to the development of meteorological science and international cooperation for more than 40 years.
He was Head of Research at the European Centre for Medium-Range Weather Forecasts (ECMWF) and was later appointed Director. He also led the Max Planck Institute for Meteorology in Hamburg
The WMO Prize is awarded to scientists for outstanding contributions to the advancement of meteorology and hydrology, as well as encouraging scientists active in those fields. The IMO Prize originates from WMO’s predecessor, the International Meteorological Organization (IMO), which was founded in 1873.
The WMO awarded several other prizes. For a complete list see http://www.wmo.ch/index-en.html
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