9:47 PM
Gabriella Brianna
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An unparalleled heat wave in eastern Europe, coupled with intense droughts and fires around Moscow, put Earth’s temperatures in the headlines this summer. Likewise, a string of exceptionally warm days in July in the eastern United States strained power grids, forced nursing home evacuations, and slowed transit systems. Both high-profile events reinvigorated questions about humanity’s role in climate change.
But, from a global perspective, how warm was the summer exactly? How did the summer's temperatures compare with previous years? And was global warming the "cause" of the unusual heat waves? Scientists at NASA's Goddard Institute for Space Studies (GISS) in New York City, led by GISS's director, James Hansen, have analyzed summer temperatures and released an update on the GISS website that addresses all of these questions.
Globally, June through August, according to the GISS analysis, was the fourth-warmest summer period in GISS’s 131-year-temperature record. The same months during 2009, in contrast, were the second warmest on record. The slightly cooler 2010 summer temperatures were primarily the result of a moderate La Niña (cooler than normal temperatures in the equatorial Pacific Ocean) replacing a moderate El Niño (warmer than normal temperatures in the equatorial Pacific Ocean).
As part of their analysis, Hansen and colleagues released a series of graphs that help explain why perceptions of global temperatures vary -- often erroneously -- from season to season and year to year. For example, unusually warm summer temperatures in the United States and eastern Europe created the impression of global warming run amuck in those regions this summer, while last winter's unusually cool temperatures created the opposite impression. A more global view, as shown below for 2009 and 2010, makes clear that extrapolating global trends based on the experience of one or two regions can be misleading.
"Unfortunately, it is common for the public to take the most recent local seasonal temperature anomaly as indicative of long-term climate trends," Hansen notes. "[We hope] these global temperature anomaly maps may help people understand that the temperature anomaly in one place in one season has limited relevance to global trends."
Last winter, for example, unusually cool temperatures in much of the United States caused many Americans to wonder why temperatures seemed to be plummeting, and whether the Earth could actually be experiencing global warming in the face of such frigid temperatures. A more global view, seen in the lower left of the four graphs above, shows that global warming trends had hardly abated. In fact, despite the cool temperatures in the United States, last winter was the second-warmest on record.
Meanwhile, the global seasonal temperatures for the spring of 2010 -- March, April, and May -- was the warmest on GISS's record. Does that mean that 2010 will shape up to be the warmest on record? Since the warmest year on GISS’s record -- 2005 -- experienced especially high temperatures during the last four calendar months of the year, it’s not yet clear how 2010 will stack up.
"It is likely that the 2005 or 2010 calendar year means will turn out to be sufficiently close that it will be difficult to say which year was warmer, and results of our analysis may differ from those of other groups," Hansen notes. "What is clear, though, is that the warmest 12-month period in the GISS analysis was reached in mid-2010."
The Russian heat wave was highly unusual. Its intensity exceeded anything scientists have seen in the temperature record since widespread global temperature measurements became available in the 1880s. Indeed, a leading Russian meteorologist asserted that the country had not experienced such an intense heat wave in the last 1,000 years. And a prominent meteorologist with Weather Underground estimated such an event may occur as infrequently as once every 15,000 years.
In the face of such a rare event, there’s much debate and discussion about whether global warming can "cause" such extreme weather events. The answer -- both no and yes -- is not a simple one.
Weather in a given region occurs in such a complex and unstable environment, driven by such a multitude of factors, that no single weather event can be pinned solely on climate change. In that sense, it's correct to say that the Moscow heat wave was not caused by climate change.
However, if one frames the question slightly differently: "Would an event like the Moscow heat wave have occurred if carbon dioxide levels had remained at pre-industrial levels," the answer, Hansen asserts, is clear: "Almost certainly not."
The frequency of extreme warm anomalies increases disproportionately as global temperature rises. "Were global temperature not increasing, the chance of an extreme heat wave such as the one Moscow experienced, though not impossible, would be small," Hansen says.
For more information visit http://www.nasa.gov/topics/earth/features/summer-temps.html
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10:11 PM
Gabriella Brianna
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A team of planet hunters from the University of California (UC) Santa Cruz, and the Carnegie Institution of Washington has announced the discovery of a planet with three times the mass of Earth orbiting a nearby star at a distance that places it squarely in the middle of the star's "habitable zone."
This discovery was the result of more than a decade of observations using the W. M. Keck Observatory in Hawaii, one of the world's largest optical telescopes. The research, sponsored by NASA and the National Science Foundation, placed the planet in an area where liquid water could exist on the planet's surface. If confirmed, this would be the most Earth-like exoplanet yet discovered and the first strong case for a potentially habitable one.
To astronomers, a "potentially habitable" planet is one that could sustain life, not necessarily one where humans would thrive. Habitability depends on many factors, but having liquid water and an atmosphere are among the most important.
The new findings are based on 11 years of observations of the nearby red dwarf star Gliese 581using the HIRES spectrometer on the Keck I Telescope. The spectrometer allows precise measurements of a star's radial velocity (its motion along the line of sight from Earth), which can reveal the presence of planets. The gravitational tug of an orbiting planet causes periodic changes in the radial velocity of the host star. Multiple planets induce complex wobbles in the star's motion, and astronomers use sophisticated analyses to detect planets and determine their orbits and masses.
"Keck's long-term observations of the wobble of nearby stars enabled the detection of this multi-planetary system," said Mario R. Perez, Keck program scientist at NASA Headquarters in Washington. "Keck is once again proving itself an amazing tool for scientific research."
Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz, and Paul Butler of the Carnegie Institution lead the Lick-Carnegie Exoplanet Survey.
"Our findings offer a very compelling case for a potentially habitable planet," said Vogt. "The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common."
The paper reports the discovery of two new planets around Gliese 581. This brings the total number of known planets around this star to six, the most yet discovered in a planetary system outside of our own. Like our solar system, the planets around Gliese 581 have nearly-circular orbits.
The new planet designated Gliese 581g has a mass three to four times that of Earth and orbits its star in just under 37 days. Its mass indicates that it is probably a rocky planet with a definite surface and enough gravity to hold on to an atmosphere.
Gliese 581, located 20 light years away from Earth in the constellation Libra, has two previously detected planets that lie at the edges of the habitable zone, one on the hot side (planet c) and one on the cold side (planet d). While some astronomers still think planet d may be habitable if it has a thick atmosphere with a strong greenhouse effect to warm it up, others are skeptical. The newly-discovered planet g, however, lies right in the middle of the habitable zone.
The planet is tidally locked to the star, meaning that one side is always facing the star and basking in perpetual daylight, while the side facing away from the star is in perpetual darkness. One effect of this is to stabilize the planet's surface climates, according to Vogt. The most habitable zone on the planet's surface would be the line between shadow and light (known as the "terminator").
For more information visit http://www.nasa.gov/topics/universe/features/gliese_581_feature.html
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9:38 PM
Gabriella Brianna
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Imagine building a car chassis without a blueprint or even a list of recommended construction materials.
In a sense, that's precisely what a team of engineers at the NASA Goddard Space Flight Center in Greenbelt, Md., did when they designed a one-of-a-kind structure that is one of 9 key new technology systems of the Integrated Science Instrument Module (ISIM). Just as a chassis supports the engine and other components in a car, the ISIM will hold four highly sensitive instruments, electronics, and other shared instrument systems flying on the James Webb Space Telescope, NASA's next flagship observatory.
From scratch — without past experience to help guide them — the engineers designed the ISIM made of a never-before-manufactured composite material and proved through testing that it could withstand the super-cold temperatures it would encounter when the observatory reached its orbit 1.5-million kilometers (930,000 miles) from Earth. In fact, the ISIM structure survived temperatures that plunged as low as 27 Kelvin (-411 degrees Fahrenheit), colder than the surface of Pluto.
"It is the first large, bonded composite spacecraft structure to be exposed to such a severe environment," said Jim Pontius, ISIM lead mechanical engineer.
The 26-day test was specifically carried out to test whether the car-sized structure contracted and distorted as predicted when it cooled from room temperature to the frigid — very important since the science instruments must maintain a specific location on the structure to receive light gathered by the telescope's 6.5-meter (21.3-feet) primary mirror. If the structure shrunk or distorted in an unpredictable way due to the cold, the instruments no longer would be in position to gather data about everything from the first luminous glows following the big bang to the formation of star systems capable of supporting life.
"The tolerances are much looser on the Hubble Space Telescope," said Ray Ohl, a Goddard optical engineer who leads ISIM's optical integration and test. "The optical requirements for Webb are even more difficult to meet than those on Hubble."
Despite repeated cycles of testing, the truss-like assembly designed by Goddard engineers did not crack. The structure shrunk as predicted by only 170 microns — the width of a needle —when it reached 27 Kelvin (-411 degrees Fahrenheit), far exceeding the design requirement of about 500 microns. "We certainly wouldn’t have been able to realign the instruments on orbit if the structure moved too much," said ISIM Structure Project Manager Eric Johnson. "That's why we needed to make sure we had designed the right structure."
Obtaining the Unobtainium
Achieving the milestone was just one of many firsts for the Goddard team. Almost on every level, "we pushed the technology envelope, from the type of material we would use to build ISIM to how we would test it once it was assembled," Pontius added. "The technology challenges are what attracted the people to the program."
One of the first challenges the team tackled after NASA had named Goddard as the lead center to design and develop ISIM was identifying a structural material that would assure the instruments' precise cryogenic alignment and stability, yet survive the extreme gravitational forces experienced during launch.
An exhaustive search in the technical literature for a possible candidate material yielded nothing, leaving the team with only one alternative — developing its own as-yet-to-be manufactured material, which team members jokingly referred to as "unobtainium." Through mathematical modeling, the team discovered that by combining two composite materials, it could create a carbon fiber/cyanate-ester resin system that would be ideal for fabricating the structure's square tubes that measure 75-mm (3-inch) in diameter.
How then would engineers attach these tubes? Again through mathematical modeling, the team found it could bond the pieces together using a combination of nickel-alloy fittings, clips, and specially shaped composite plates joined with a novel adhesive process, smoothly distributing launch loads while holding the instruments in precise locations — a difficult engineering challenge because different materials react differently to changes in temperature.
"We engineered from the small pieces to the big pieces testing along the way to see if the failure theories were correct. We were looking to see where the design could go wrong," Pontius explained. "By incorporating the lessons learned into the final flight structure, we met the requirements and test validated our building-block approach."
Making Cold, Colder
The test inside Goddard's Space Environment Simulator — a three-story thermal-vacuum chamber that simulates the temperature and vacuum conditions found in space — presented its own set of technological hurdles. "We weren't sure we could get the simulator cold enough," said Paul Cleveland, a technical consultant at Goddard involved in the project. For most spacecraft, the simulator's ability to cool down to 100 Kelvin (-279.7 degrees Fahrenheit) is cold enough. Not so for the Webb telescope, which will endure a constant temperature of 39 Kelvin (-389.5 degrees Fahrenheit) when it reaches its deep-space orbit.
The group engineered a giant tuna fish can-like shroud, cooled by helium gas, and inserted it inside the 27-foot diameter chamber. "When you get down to these temperatures, the physics change," Cleveland said. Anything, including wires or small gaps in the chamber, can create an intractable heat source. "It's a totally different arena," he added. "One watt can raise the temperature by 20 degrees Kelvin. We had to meticulously close the gaps."
With the gaps closed and the ISIM safely lowered into the helium shroud, technicians began sucking air from the chamber to create a vacuum. They activated the simulator's nitrogen panels to cool the chamber to 100 Kelvin (-279.7 degrees Fahrenheit) and began injecting helium gas inside the shroud to chill the ISIM to the correct temperature.
To measure ISIM's reaction as it cooled to the sub-freezing temperatures, the team used a technique called photogrammetry, the science of making precise measurements by means of photography. However, using the technique wasn't so cut-and-dried when carried out in a frosty, airless environment, Ohl said. To protect two commercial-grade cameras from extreme frostbite, team members placed the equipment inside specially designed protective canisters and attached the camera assemblies to the ends of a motorized boom.
As the boom made nearly 360-degree sweeps inside the helium shroud, the cameras snapped photos through a gold-coated glass window of reflective, hockey puck-shaped targets bolted onto ISIM's composite tubes. From the photos, the team could precisely determine whether the targets moved, and if so, by how much.
"It passed with flying colors," Pontius said, referring to the negligible shrinkage. "This test was a huge success for us."
With the critical milestone test behind them, team members say their work likely will serve NASA in the future. Many future science missions will also operate in deep space, and therefore would have to be tested under extreme cryogenic conditions. In the meantime, though, the facility will be used to test other Webb telescope systems, including the backplane, the structure to which the Webb telescope’s 18 primary mirror segments are bolted when the observatory is assembled. "We need to characterize its bending at cryogenic temperatures," Ohl said.
For more information visit http://www.nasa.gov/topics/technology/features/jwst-unobtainium.html
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9:49 PM
Gabriella Brianna
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Turning a midsummer night's dream into reality, NASA's Cassini spacecraft begins its new mission extension -- the Cassini Solstice Mission -- today. The mission extension will take Cassini a few months past Saturn's northern summer solstice (or midsummer) through September 2017. It will enable scientists to study seasonal changes and other long-term weather changes on Saturn and its moons.
Cassini had arrived just after Saturn's northern winter solstice in 2004, and the extension continues a few months past the northern summer solstice in May 2017. A complete seasonal period on Saturn has never been studied at this level of detail.
Cassini has revealed a bounty of scientific discoveries since its launch in 1997, including previously unknown characteristics of the Earth-like world of Saturn's moon Titan, and the plume of water vapor and organic particles spewing from another moon, Enceladus.
The Cassini Solstice Mission will enable continued study of these intriguing worlds. It will also allow scientists to continue observations of Saturn's rings and the magnetic bubble around the planet, known as the magnetosphere. Near the end of the mission, the spacecraft will make repeated dives between Saturn and its rings to obtain in-depth knowledge of the gas giant. During these dives, the spacecraft will study the internal structure of Saturn, its magnetic fluctuations and ring mass.
Cassini entered orbit around Saturn in 2004. Mission managers had originally planned for a four-year tour of the Saturnian system. In 2008, Cassini received a mission extension through September 2010 to probe the planet and its moons through equinox, when the sun was directly over the equator. Equinox, which occurred in August 2009, marked the turn from southern fall to northern spring. The second mission extension, called the Cassini Solstice Mission, was announced earlier this year.
"After nearly seven years in transit and six years in Saturn orbit, this spacecraft still just hums along," said Bob Mitchell, Cassini program manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "With seven more years to go, the science should be just as exciting as what we've seen so far."
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the project for NASA's Science Mission Directorate in Washington. The Cassini orbiter was designed, developed and assembled at JPL.
For more information visit http://www.jpl.nasa.gov/news/news.cfm?release=2010-314
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9:19 PM
Gabriella Brianna
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This summer, wildfires swept across some 22 regions of Russia, blanketing the country with dense smoke and in some cases destroying entire villages. In the foothills of Boulder, Colo., this month, wildfires exacted a similar toll on a smaller scale.
That's just the tip of the iceberg. Thousands of wildfires large and small are underway at any given time across the globe. Beyond the obvious immediate health effects, this "biomass" burning is part of the equation for global warming. In northern latitudes, wildfires actually are a symptom of the Earth's warming.
'We already see the initial signs of climate change, and fires are part of it," said Dr. Amber Soja, a biomass burning expert at the National Institute of Aerospace (NIA) in Hampton, Va.
And research suggests that a hotter Earth resulting from global warming will lead to more frequent and larger fires.
The fires release "particulates" -- tiny particles that become airborne -- and greenhouse gases that warm the planet.
Human ignition
A common perception is that most wildfires are caused by acts of nature, such as lightning. The inverse is true, said Dr. Joel Levine, a biomass burning expert at NASA Langley Research Center in Hampton, Va.
"What we found is that 90 percent of biomass burning is human instigated," said Levine, who was the principal investigator for a NASA biomass burning program that ran from 1985 to 1999.
Levine and others in the Langley-led Biomass Burning Program travelled to wildfires in Canada, California, Russia, South African, Mexico and the wetlands of NASA's Kennedy Space Center in Florida.
Biomass burning accounts for the annual production of some 30 percent of atmospheric carbon dioxide, a leading cause of global warming, Levine said.
Dr. Paul F. Crutzen, a pioneer of biomass burning, was the first to document the gases produced by wildfires in addition to carbon dioxide.
"Modern global estimates agree rather well with the initial values," said Crutzen, who shared the Nobel Prize in Chemistry 1995 with Mario J. Molina and F. Sherwood Rowland for their "work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone."
Northern exposure
Whether biomass burning is on the rise globally is not clear. But it definitely is increasing in far northern latitudes, in "boreal" forests comprised largely of coniferous trees and peatlands.
The reason is that, unlike the tropics, northern latitudes are warming, and experiencing less precipitation, making them more susceptible to fire. Coniferous trees shed needles, which are stored in deep organic layers over time, providing abundant fuel for fires, said Soja, whose work at the NIA supports NASA.
"That's one of the reasons northern latitudes are so important," she said, "and the smoldering peat causes horrible air quality that can affect human health and result in death."
Fires in different ecosystems burn at different temperatures due to the nature and structure of the biomass and its moisture content. Burning biomass varies from very thin, dry grasses in savannahs to the very dense and massive, moister trees of the boreal, temperate and tropical forests.
Fire combustion products vary over a range depending on the degree of combustion, said Levine, who authored a chapter on biomass burning for a book titled "Methane and Climate Change," published in August by Earthscan.
Flaming combustion like the kind in thin, small, dry grasses in savannahs results in near-complete combustion and produces mostly carbon dioxide. Smoldering combustion in moist, larger fuels like those in forest and peatlands results in incomplete combustion and dirtier emission products such as carbon monoxide.
Boreal fires burn the hottest and contribute more pollutants per unit area burned.
'Eerie experience'
Being near large wildfires is a unique experience, said Levine. "The smoke is so thick it looks like twilight. It blocks out the sun. It looks like another planet. It's a very eerie experience."
In Russia, the wildfires are believed caused by a warming climate that made the current summer the hottest on record. The hotter weather increases the incidence of lightning, the major cause of naturally occurring biomass burning.
Soja said she hopes the wildfires in Russia prompt the country to support efforts to mitigate climate change. In fact, Russia's president, Dmitri A. Medvedev, last month acknowledged the need to do something about it.
"What's happening with the planet's climate right now needs to be a wake-up call to all of us, meaning all heads of state, all heads of social organizations, in order to take a more energetic approach to countering the global changes to the climate," said Medvedev, in contrast to Russia's long-standing position that human-induced climate change is not occurring.
For more information visit http://www.nasa.gov/topics/earth/features/wildfires.html
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9:40 PM
Gabriella Brianna
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The northern hemisphere of Saturn's moon Titan is set for mainly fine spring weather, with polar skies clearing since the equinox in August last year. The visual and infrared mapping spectrometer (VIMS) aboard NASA's Cassini spacecraft has been monitoring clouds on Titan regularly since the spacecraft entered orbit around Saturn in 2004. Now, a group led by Sébastien Rodriguez, a Cassini VIMS team collaborator based at Université Paris Diderot, France, has analyzed more than 2,000 VIMS images to create the first long-term study of Titan's weather using observational data that also includes the equinox. Equinox, when the sun shone directly over the equator, occurred in August 2009.
Rodriguez is presenting the results and new images at the European Planetary Science Congress in Rome on Sept. 22.
Though Titan's surface is far colder and lacks liquid water, this moon is a kind of "sister world" to Earth because it has a surface covered with organic material and an atmosphere whose chemical composition harkens back to an early Earth. Titan has a hydrological cycle similar to Earth's, though Titan's cycle depends on methane and ethane rather than water.
A season on Titan lasts about seven Earth years. Rodriguez and colleagues observed significant atmospheric changes between July 2004 (early summer in Titan's southern hemisphere) and April 2010 (the very start of northern spring). The images showed that cloud activity has recently decreased near both of Titan's poles. These regions had been heavily overcast during the late southern summer until 2008, a few months before the equinox.
Over the past six years, the scientists found that clouds clustered in three distinct latitude regions of Titan: large clouds at the north pole, patchy clouds at the south pole and a narrow belt around 40 degrees south. "However, we are now seeing evidence of a seasonal circulation turnover on Titan – the clouds at the south pole completely disappeared just before the equinox and the clouds in the north are thinning out," Rodriguez said. "This agrees with predictions from models and we are expecting to see cloud activity reverse from one hemisphere to another in the coming decade as southern winter approaches."
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate, Washington, D.C. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.
For more information visit http://www.jpl.nasa.gov/news/news.cfm?release=2010-308
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9:47 PM
Gabriella Brianna
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Meanwhile, the global seasonal temperatures for the spring of 2010 -- March, April, and May -- was the warmest on GISS's record. Does that mean that 2010 will shape up to be the warmest on record? Since the warmest year on GISS’s record -- 2005 -- experienced especially high temperatures during the last four calendar months of the year, it’s not yet clear how 2010 will stack up.
