El Nino, Climate Change link Unclear

The frequency and volatility of El Nino, a weather pattern that hammers the tropical Pacific Ocean every five years or so, does not seem linked to climate change, said US research.

The study involved scientists measuring the monthly growth of ancient coral fossils found on two tropical Pacific islands to determine what, if any, impact the warming climate had on the weather phenomenon.

By reconstructing temperatures and precipitation over the millenniums, the study compared it to the frequency and intensity of El Nino and found that the latter had indeed become more intense and frequent in the 20th century.

But although the increase was statistically significant and could be linked to climate change, the long historic record provided by the coral fossils allowed the researchers to determine that the El Nino Southern Oscillation (ENSO), has also had large natural variations in past centuries.

Thus, it is not clear that changes seen in recent decades can be linked to climate change caused by rising levels of carbon dioxide, the researchers said.

"The level of ENSO variability we see in the 20th century is not unprecedented," said climatologist Professor Kim Cobb, from the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology.

"But the 20th century does stand out, statistically, as being higher than the fossil coral baseline," she added.

The study was sponsored by the National Science Foundation and published in the journal Science.

Researchers from the Scripps Institution of Oceanography and the University of Minnesota also contributed to the study.

El Nino occurs every two to seven years, when the trade winds that circulate surface water in the tropical Pacific start to weaken.

A mass of warm water builds in the western Pacific and eventually rides over to the eastern side of the ocean, causing a major shift in rainfall, bringing floods and mudslides to usually arid countries in the region.

El Nino is ushered out by a cold phase, La Nina, which usually occurs the following year.

NASA Saturn Cassini VIMS Instrument re-assigned to Venus watching

This image shows the visual and infrared mapping spectrometer instrument (VIMS) just before it was attached to NASA's Cassini spacecraft. 

Cassini launched in 1997 and has been exploring the Saturn system since 2004.

Credit: NASA/JPL-Caltech/University of Arizona.

For seven years, a mini-fridge-sized instrument aboard NASA's Cassini spacecraft reliably investigated;

• weather patterns swirling around Saturn; 
• the hydrocarbon composition of the surface of Saturn's moon Titan;
• the aerosol layers of Titan's haze; and 
• dirt mixing with ice in Saturn's rings. 

But this year the instrument - the visual and infrared mapping spectrometer - has been testing out some new telescopic muscles.

This Friday, Dec. 21, the spectrometer will be tracking the path of Venus across the face of the sun from its perch in the Saturn system.

Earthlings saw such a transit earlier this year, from June 5 to 6, but the observation in December will be the first time a spacecraft has tracked a transit of a planet in our solar system from beyond Earth orbit.

Cassini will collect data on the molecules in Venus's atmosphere as sunlight shines through it.

But learning about Venus actually isn't the point of the observation. Scientists actually want to use the occasion to test the VIMS instrument's capacity for observing planets outside our solar system.

"Interest in infrared investigations of extra-solar planets has exploded in the years since Cassini launched, so we had no idea at the time that we'd ask VIMS to learn this new kind of trick," said Phil Nicholson, the VIMS team member based at Cornell University, Ithaca, N.Y., who is overseeing the transit observations. "But VIMS has worked so well at Saturn so far that we can start thinking about other things it can do."

VIMS will be able to complement exoplanet studies by space telescopes such as NASA and ESA's Hubble and Spitzer space telescopes. VIMS scientists are particularly interested in investigating atmospheric data - such as signatures of methane - from far-off star systems in near-infrared wavelengths.

The pointing has to be very accurate to get one of those extrasolar planets in VIMS's viewfinder, but the instrument has had lots of practice pointing at other stars.

Earlier this year, VIMS obtained its first successful observation of a transit by the exoplanet HD 189733b. Scientists want to improve these observations by reducing the amount of noise in the signal.

NORUSCA II camera: First-ever hyperspectral images of Earth's auroras

The aurora as seen as a color composite image from the NORUSCA II camera.

Three bands were combined to make the image. 

Each band was assigned a different color - red, green, and blue - to enhance the features of the aurora for analysis. 

Credit: Optics Express.

Hoping to expand our understanding of auroras and other fleeting atmospheric events, a team of space-weather researchers designed and built NORUSCA II, a new camera with unprecedented capabilities that can simultaneously image multiple spectral bands, in essence different wavelengths or colors, of light.

The camera was tested at the Kjell Henriksen Observatory (KHO) in Svalbard, Norway, where it produced the first ever hyperspectral images of auroras-commonly referred to as "the Northern (or Southern) Lights" and may already have revealed a previously unknown atmospheric phenomenon.

Details on the camera and the results from its first images were published in the Optical Society's (OSA) open-access journal Optics Express.

Auroras, nature's celestial fireworks, are created when charged particles from the Sun penetrate Earth's magnetic field. These shimmering displays in the night sky reveal important information about the Earth-Sun system and the way our planet responds to powerful solar storms.

Current-generation cameras, however, are simply light buckets-meaning they collect all the light together into one image-and lack the ability to separately capture and analyze multiple slivers of the visible spectrum.

That means if researchers want to study auroras by looking at specific bands or a small portion of the spectrum they would have to use a series of filters to block out the unwanted wavelengths.

The red arrow points to the unidentified low-intensity wave pattern, which the researchers suspect is an auroral-generated wave interaction with airglow. 

For contrast, the blue arrow points to the faint emission of the Milky Way. Credit: Optics Express.

The new NORUSCA II hyperspectral camera achieves the same result without any moving parts, using its advanced optics to switch among all of its 41 separate optical bands in a matter of microseconds, orders of magnitude faster than an ordinary camera.

This opens up new possibilities for discovery by combining specific bands of the same ethereal phenomenon into one image, revealing previously hidden details.

"A standard filter wheel camera that typically uses six interference filters will not be able to spin the wheel fast enough compared to the NORUSCA II camera," said Fred Sigernes of the University Centre in Svalbard (UNIS), Norway.

"This makes the new hyperspectral capability particularly useful for spectroscopy, because it can detect specific atmospheric constituents by their unique fingerprint, or wavelengths, in the light they emit."

These spectral signatures can then reveal subtle changes in atmospheric behaviour, such as the ionization of gases during auroras. This form of multispectral imaging also will enable scientists to better classify auroras from background sky emissions and study the way they cluster in the atmosphere.