WEATHER OR NOT?

MIT researcher finds evidence of global warming on Neptune's largest moon
June 24, 1998


CAMBRIDGE, Mass. -- We're not the only ones experiencing global warming. A Massachusetts Institute of Technology researcher has reported that observations obtained by NASA's Hubble Space Telescope and ground-based instruments reveal that Neptune's largest moon, Triton, seems to have heated up significantly since the Voyager space probe visited it in 1989. The warming trend is causing part of Triton's surface of frozen nitrogen to turn into gas, thus making its thin atmosphere denser.

While no one is likely to plan a summer vacation on Triton, this report in the June 25 issue of the journal Nature by MIT astronomer James L. Elliot and his colleagues from MIT, Lowell Observatory and Williams College says that the moon is approaching an unusually warm summer season that only happens once every few hundred years. Elliot and his colleagues believe that Triton's warming trend could be driven by seasonal changes in the absorption of solar energy by its polar ice caps.

"At least since 1989, Triton has been undergoing a period of global warming. Percentage-wise, it's a very large increase," said Elliot, professor of Earth, Atmospheric and Planetary Sciences and director of the Wallace Astrophysical Observatory. The 5 percent increase on the absolute temperature scale from about minus-392 degrees Fahrenheit to about minus-389 degrees Fahrenheit would be like the Earth experiencing a jump of about 22 degrees Fahrenheit.

Triton is a simpler subject than Earth for studying the causes and effects of global warming. "It's generally true around the solar system that when we try to understand a problem as complex as global warming -- one in which we can't control the variables -- the more extreme cases we have to study, the more we can become sure of certain factors," Elliot said. "With Triton, we can clearly see the changes because of its simple, thin atmosphere."

The moon is approaching an extreme southern summer, a season that occurs every few hundred years. During this special time, the moon's southern hemisphere receives more direct sunlight. The equivalent on Earth would be having the sun directly overhead at noon north of Lake Superior during a northern summer.

Elliot and his colleagues believe that Triton's temperature has increased because of indications that the pressure of the atmosphere has increased. Because of the unusually strong correlation between Triton's surface ice temperature and its atmospheric pressure, Elliot said scientists can infer a temperature increase of 3 degrees Fahrenheit over nine years based on its recent increase in surface vapor pressure. Any ice on Triton that warms up a little results in a big increase in atmospheric pressure as the vaporized gas joins the atmosphere.

Scientists used one of the Hubble telescope's three Fine Guidance Sensors in November 1997 to measure Triton's atmospheric pressure when the moon passed in front of a star. Two of Hubble's guidance sensors are normally used to keep the telescope pointed at a celestial target by monitoring the brightness of guide stars. The third can serve as a scientific instrument.

In this case, the guidance sensor measured a star's gradual decrease in brightness as Triton passed in front of it. The starlight got dimmer as it traveled through Triton's thicker atmosphere and then got cut off completely by the moon's total occultation of the star. This filtering of starlight through an atmosphere is similar to what happens during a sunset. As the sun dips toward the horizon, its light dims because it is traveling through denser air and because the sun's disk gets "squashed."

By detecting that Triton's atmosphere had thickened, astronomers were able to deduce that the temperature of the ice on Triton's surface has increased. "This pressure increase implies a temperature increase," Elliot wrote. "At this rate, the atmosphere has at least doubled in bulk since the time of the Voyager encounter." Like the Earth, Triton's atmosphere is composed mostly of molecular nitrogen, but its surface pressure is much less than that of the Earth--about the same as that 45 miles high in the Earth's atmosphere.

In their Nature paper, Elliot and his colleagues list two other possible explanations for Triton's warmer weather. Because the frost pattern on Triton's surface may have changed over the years, it may be absorbing a little more of the sun's warmth. Or changes in reflectivity of Triton's ice may have caused it to absorb more heat. "When you're so cold, global warming is a welcome trend," said Elliot.

About the same size and density as Pluto, Triton--one of Neptune's eight moons--is 30 times as far from the sun as the Earth. It is very cold and windy, with winds close to the speed of sound, and has a mixed terrain of icy regions and bare spots. Triton is a bit smaller than our moon, but its gravity is able to keep an atmosphere from completely escaping because it is so cold. Its composition is believed to be similar to a comet's, although it is much larger than a comet. Triton was captured into a reverse orbit by Neptune's strong gravitational pull.

Other astronomers who participated in this investigation are MIT research assistant Heidi B. Hammel and technical assistants Michael J. Person and Stephen W. McDonald of MIT; Otto G. Franz, Lawrence H. Wasserman, John A. Stansberry, John R. Spencer, Edward W. Dunham, Catherine B. Olkin and Mark W. Buie of Lowell Observatory; Jay M. Pasachoff, Bryce A. Babcock and Timothy H. McConnochie of Williams College.

This work is supported in part by NASA, the National Science Foundation and the National Geographic Society.

The Worst Weather in the Solar System
By Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
06 March 2001




Venus: Holy Heat Wave!

A comedian on Venus could make a career out of "it was so hot" jokes. But for planetary scientists, intense heat on the second planet from the Sun is no laughing matter. And there is no argument over global warming.

We're talking hot and thick. Venus' atmosphere is nearly 100 times as dense as the one you breathe.

They call it a case of runaway greenhouse effect, and some scientists say it might hold lessons for where Earth's climate could be headed. The effect occurs because heavy doses of carbon dioxide and other gases in Venus' atmosphere let the Sun shine in, but then trap the heat like a black wool suit on a summer day in Atlanta. Earth's atmosphere has less carbon dioxide; so while there is also a natural greenhouse effect on our planet, it is more subdued. Much of the heat generated by the Sun is re-radiated into space.

At least this is the basic theory. But there's a puzzling aspect.

"Venus is much warmer than one would predict based on the amount of sunlight it absorbs," said Andrew Ingersoll, the Caltech planetary scientist. "Venus is closer to the Sun and receives more sunlight than Earth, but it reflects a higher fraction, so it actually absorbs slightly less than Earth," he said. Yet, "Venus is much warmer than one would predict based on the amount of sunlight it absorbs."

Okay, we bite. How hot is it?

"The surface of Venus is over 700 Kelvin while the surface of Earth is less than 300 Kelvin, on average."

Translated -- That's 860 degrees Fahrenheit (427 degrees Celsius). Hot enough to melt lead.

Makes you wonder what SPF to bring along.

Saturn's Bull's-Eye Marks Its Hot Spot

02.03.05


NASA astronomers using the Keck I telescope in Hawaii are learning much more about a strange, thermal "hot spot" on the tip of Saturn's south pole.

In the most precise reading of Saturn's temperatures ever taken from Earth, a new set of infrared images suggests a warm "polar vortex" at Saturn's south pole - the first warm polar cap ever to be discovered in the solar system. The vortex is punctuated by a compact spot that is the warmest place on the planet. The researchers report their findings in the Feb. 4 issue of the journal Science.

The images can be viewed at: http://www.nasa.gov/multimedia/imagegallery/.

A polar vortex is a persistent, large-scale weather pattern, likened to a jet stream on Earth in the upper atmosphere. On Earth, the Arctic Polar Vortex is typically located over eastern Canada and plunges arctic air to the northern plains in the United States. Earth's cold Antarctic Polar Vortex, centered over Antarctica, traps air and creates unusual chemistry, such as the effects that create the "ozone hole".

Polar vortices on Earth, Jupiter, Mars and Venus are colder than their surroundings. But new images from the W. M. Keck Observatory show the first evidence of such a polar vortex at much warmer temperatures than their surroundings. And the even warmer, compact region at the pole itself is quite unusual.

"There is nothing like this compact warm 'cap' in the Earth's atmosphere," said Dr. Glenn S. Orton, senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and lead author of the paper. "Meteorologists have detected sudden warming of the pole, but on Earth this effect is very short-term. This phenomenon on Saturn is longer-lived because we've been seeing hints of it in our data for at least two years."

Data for these observations were taken in the imaging mode of the Keck facility instrument, the Long Wavelength Spectrometer, on Feb. 4, 2004, by Orton and Dr. Padma Yanamandra-Fisher, the paper's co-author, also a research scientist at JPL.

The puzzle isn't that Saturn's south pole is warm; after all, it has been exposed to 15 years of continuous sunlight, having just reached its summer Solstice late in 2002. But both the distinct boundary of a warm polar vortex some 30 degrees latitude from the southern pole and a very hot "tip" right at the pole were completely unexpected. If the increased southern temperatures are the result of the seasonal variations of sunlight, then temperatures should increase gradually with increasing latitude. But they don't - the tropospheric temperature increases toward the pole abruptly near 70 degrees latitude from 88 to 89 Kelvin (- 301 to -299 degrees Fahrenheit) and then to 91 Kelvin (-296 degrees Fahrenheit) right at the pole. Near 70 degrees latitude, the stratospheric temperature increases even more abruptly from 146 to 150 Kelvin (-197 to -189 degrees Fahrenheit) and then again to 151 Kelvin (-188 degrees Fahrenheit) right at the pole.

The abrupt temperature changes may be caused by a concentration of sunlight-absorbing particulates trapping heat in Saturn's upper atmosphere. This theory would explain why the hot spot appears dark in visible light and contains the highest measured temperatures on Saturn. However, this alone would not explain why the particles themselves are constrained to a compact area at Saturn's south pole. One possible explanation would be downwelling of dry air, which is also consistent with deeper clouds observed at the southern pole. Researchers plan more observations to check that possibility.

More detail about the temperatures and possible chemical changes in these regions may be available from an infrared spectrometer on the Cassini spacecraft, in orbit around Saturn. The discovery of the hot spot at Saturn's south pole has prompted Cassini's composite infrared spectrometer science team, including Orton, to redirect some future observations to this area.

"One of the obvious questions is whether Saturn's north pole is abnormally cold and whether a cold polar vortex has been established there. That's something we can't see from Earth, and Cassini's instruments will be in a unique position to observe it," said Orton.

Funding for this research was provided by NASA's Office of Space Sciences and Applications, Planetary Astronomy Discipline, and the NASA Cassini project. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C.

The W.M. Keck Observatory is operated by the California Association for Research in Astronomy, a non-profit scientific partnership of the California Institute of Technology, the University of California, and NASA. On the Web at www.keckobservatory.org .

Jupiter's Spots Disappear Amid Major Climate Change
By Robert Roy Britt
Senior Science Writer
posted: 01:00 pm ET
21 April 2004




Jupiter is undergoing major climate change and could lose many of its large spots over the next seven years, only to make way for the creation of fresh spots in a decades-long cycle, according to a new explanation of old mysteries.

While the analysis remains to be proven, it is seen by other researchers as interesting and, importantly, testable even with large backyard telescopes.

Philip Marcus, a professor at the University of California, Berkeley who came up with the idea is an expert in fluid and atmospheric dynamics. He has never seen Jupiter through a telescope. But his computer modeling, reported in the April 22 issue of the journal Nature, accounts for previously noted disappearances of large white spots, and it makes predictions that can easily be verified or refuted.

Experienced backyard astronomers should be able to witness the forecasted changes, which include color shifts that might even alter the look of the centuries-old Great Red Spot, the mother of all storms in our solar system.

Marcus bases his prediction in part on the observed appearance of three large white ovals, all thousands of miles across, on Jupiter in 1939, and the unexpected disappearance of two of them between 1997 and 2000, during which time they all merged into one.

Other smaller spots have gone away since.

Marcus says the demise of still more spots over the next seven years will mark the end of a newly proposed, 70-year climate cycle.

During this time, Jupiter's equatorial region will warm up a whopping 18 degrees Fahrenheit (10 Celsius) and the planet will grow cooler near the poles. Then the stage will be set, as in 1939, for another batch of white ovals to dramatically appear by 2014.

What's going on

In a telephone interview, Marcus told SPACE.com how he thinks the changes are related to alternating periods of atmospheric calm and chaos.

Jupiter's spots are swirls of air called vortices, which stir up different chemical mixes to make themselves lighter or darker and of varying colors. They all march around the planet embedded in rotating cloud bands, akin to Earth's jet streams. Jupiter has about a dozen of these bands going east and a dozen heading west, moving in excess of 300 mph (482 kilometers per hour).

"Between those there's a lot of shear," Marcus explained. "And vortices thrive in that kind of environment."

Among the most pronounced of these vortices were the three largest white ovals, rotating counterclockwise in the southern hemisphere and called anticyclones.

In 1979, the Voyager spacecraft identified, for the first time, hundreds of smaller vortices, by Marcus' measure. "They always had brothers and sisters," he said. "When you saw one anticyclone, you'd see others at the same latitude." Marcus tried to create mathematical models for generating so many anticyclones in close proximity. On Earth, vortices of the same flavor -- such as two low-pressure systems or, alternately, a pair of high-pressure systems -- tend to rotate around one another without necessarily destroying one another.

"I failed miserably, because all of the vortices in a row would quickly merge into one giant vortex," Marcus said of his early models.

Invisible cyclones

Finally he figured a way to simulate the setup.

In between every two anticyclones, he inserted a cyclone, a region that rotates in the opposite direction. The opposing pairs move along what's known as a von Karman vortex street, a well understood phenomenon in fluids and the atmosphere of Earth. The virtual Jovian whirls began to hum like well-oiled gears.

"It's an extremely stable configuration," Marcus said.

Problem was, no one believed there were long-lived cyclones on Jupiter, and other scientists didn't believe they existed. Voyager had found cyclones, but because their associated clouds were tangled and disorganized, they were either not identified as vortices or were considered transients that could have no long-term influence.

Then in 1994 the Hubble Space Telescope witnessed two anticyclones that should have repelled one another instead traveling together.

"This really bugged me," Marcus recalls. "I couldn't figure out what the heck was going on."

With some more modeling, he realized that jet streams -- the cloud bands -- can develop waves. On Earth, these waves, or troughs, can capture system after system and usher them into, say California, in a weeks-long series of storms. On Jupiter, a wave can trap two anticyclones with a cyclone sandwiched between.

"Then any little perturbation can trip the balance and cause the two anticyclones to merge," Marcus realized. That's what he thinks happened to the three large white ovals that joined up a few years back.

'Serious' climate change

The mergers are part of a significant climate change Marcus thinks is imminent. Unlike Earth, Jupiter's equator is not much warmer than its poles, even though the equator receives more sunlight. That implies something is globally mixing the heat pretty effectively, Marcus explains. (Another factor is that Jupiter generates much of its heat from within.)

The vortices play a role, he thinks, with chaos as a supporting actor. Imagine putting dye in a cup of water. It doesn't mix well. But shake the cup -- introduce some chaos -- and the dye mixes easily. The vortices create chaos that extends from the visible surface down into Jupiter's hidden belly.

As more vortices on Jupiter merge, a period of calm will set in, reducing the mixing of atmospheric heat.

"If you knock out a whole row of vortices, you stop all the mixing of heat at that latitude," Marcus reasons. "This creates a big wall and prevents the transport of heat from the equator to the poles." He notes that the predicted equatorial warming of 18 degrees Fahrenheit dwarfs any climate changes measured on Earth.

"This is a serious change," he said. "It's nice to have another laboratory to look at global climate change. Perhaps we can learn something."

Peter Gierasch, a Cornell University astronomer who has modeled Jupiter's weather but was not involved in the new work, notes that heat is behind all of the cloud dynamics on Jupiter.

Marcus' modeling represents "the first time that the heating has been coupled to the vortex dynamics," Gierasch told SPACE.com. "That's a step forward."

Soon the temperature increase is expected to fuel a fresh round of chaos within the jet streams.

"You take these nice happy jet streams and make them unstable," Marcus said. "Waves form. Like waves on a beach, they break." But there's a difference between an ocean and an atmosphere with no shores. The Jovian waves will roll up and produce new, large vortices, repopulating Jupiter with new spots for skywatchers to discover.

Marcus offers a specific location for seasoned amateur astronomers to watch for change starting right now. At about 41 degrees south latitude, Voyager saw 12 distinct white ovals. Now there are fewer, he said, and more should disappear over the next seven years.

Partial immunity

Jupiter's Great Red Spot is a different beast. It's the largest, at 12,500 miles (20,120 kilometers) wide and was discovered around 1665, having now outlived all other spots. It rumbles around the planet near the equator, in what Marcus calls a "kill zone" of inactivity.

"The Red Spot is very odd, because it's not in a row of vortices," he said. "It's all by itself. So the Red Spot just goes around eating its neighbors no matter what happens."

But if the equatorial region warms as Marcus predicts, the biggest of all spots could take on a different appearance. Over the past 300 years it has changed color several times and recently altered from its traditional red to something more like salmon. Scientists aren't sure why, but it likely involves redistribution of chemicals, with underlying layers becoming exposed.

"If you heat it up, you may well change the color," Marcus said. On his web site are animations showing how cyclones and anticyclones on Jupiter interact

Glaciers 'shrinking for 100 years'
From correspondents in Copenhagen, Denmark
August 22, 2006
GREENLAND'S glaciers have been shrinking for the past century, according to a Danish study published today, suggesting that the ice melt is not a recent phenomenon caused by global warming.

Danish researchers from Aarhus University studied glaciers on Disko island, in western Greenland in the Atlantic, from the end of the 19th century until the present day.

"This study, which covers 247 of 350 glaciers on Disko, is the most comprehensive ever conducted on the movements of Greenland's glaciers," glaciologist Jacob Clement Yde, who carried out the study with Niels Tvis Knudsen, said.

Using maps from the 19th century and current satellite observations, the scientists were able to conclude that "70 per cent of the glaciers have been shrinking regularly since the end of the 1880s at a rate of around eight metres per year," Mr Yde said.

"We studied 95 per cent of the area covered by glaciers in Disko and everything indicates that our results are also valid for the glaciers along the coasts of the rest of Greenland," he said.

The biggest reduction was observed between 1964 and 1985.

"A three-to-four degree increase of the temperature on Greenland from 1920 to 1930............

SATELLITES SHOW OVERALL INCREASES IN ANTARCTIC SEA ICE COVER

While recent studies have shown that on the whole Arctic sea ice has decreased since the late 1970s, satellite records of sea ice around Antarctica reveal an overall increase in the southern hemisphere ice over the same period. Continued decreases or increases could have substantial impacts on polar climates, because sea ice spreads over a vast area, reflects solar radiation away from the Earth's surface, and insulates the oceans from the atmosphere.

In a study just published in the Annals of Glaciology, Claire Parkinson of NASA's Goddard Space Flight Center analyzed the length of the sea ice season throughout the Southern Ocean to obtain trends in sea ice coverage. Parkinson examined 21 years (1979-1999) of Antarctic sea ice satellite records and discovered that, on average, the area where southern sea ice seasons have lengthened by at least one day per year is roughly twice as large as the area where sea ice seasons have shortened by at least one day per year. One day per year equals three weeks over the 21-year period.

You can see with this dataset that what is happening in the Antarctic is not what would be expected from a straightforward global warming scenario, but a much more complicated set of events," Parkinson said.

The length of the sea ice season in any particular region or area refers to the number of days per year when at least 15 percent of that area is covered by sea ice. Some areas close to the Antarctic continent have sea ice all year long, but a much larger region of the Southern Ocean has sea ice for a smaller portion of the year, and in those regions the length of the sea ice season can vary significantly from one year to another.

To calculate the lengths of the sea ice seasons, Parkinson used satellite data gridded to 25 by 25 kilometer grid cells for the Southern Ocean region. For each grid cell, the satellite data were used to determine the concentration, or percent area, of the sea ice cover. Whenever the percentage was at least 15 percent, the grid cell was considered to have ice. Using this method, Parkinson went through the entire data set and for each grid cell had a computer count how many days of each year had ice, then calculated trends over the 21-year record.

Overall, the area of the Antarctic with trends indicating a lengthening of the sea ice season by at least one day per year was 5.6 million square kilometers (2.16 million square miles), about 60 percent the size of the United States. At the same time, the area with sea ice seasons shortening by at least one day per year was 3 million square kilometers (1.16 million square miles).

Regionally, the Ross Sea, on average, had its sea ice seasons getting longer, while most of the Amundsen Sea and almost the entire Bellingshausen Sea had their sea ice seasons getting shorter.

"The Antarctic sea ice changes match up well with regional temperature changes," Parkinson said. "The one region in the Antarctic where the temperature records have shown prominent warming over this period is the Antarctic Peninsula, and indeed it's immediately to the west and east of the Antarctic Peninsula, in the Bellingshausen/Amundsen and western Weddell seas, respectively, that the sea ice seasons have been shortening rather than lengthening."

The Arctic also shows a mixed pattern of sea ice trends over the 1979-1999 period, but in contrast to the Antarctic, the area with shortening seasons in the Arctic is far greater than the area with lengthening seasons. The Arctic patterns suggest some connections with major oscillations in large-scale atmospheric pressures, called the Arctic Oscillation and the North Atlantic Oscillation, and it is possible the ice covers of both hemispheres could be influenced by oscillations that are still not fully identified, Parkinson said.

The study used data from NASA's Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) and the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imagers (SSMIs) and in the future will be extended with data from the National Space Development Agency of Japan's Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) recently launched on board NASA's Aqua satellite.

I, for one, am very skeptical of global warming theory because I believe it may rest on wholly inadequate evidence of doubtful accuracy.

real life wrote:

I, for one, am very skeptical of global warming theory because I believe it may rest on wholly inadequate evidence of doubtful accuracy.

The climate is definitely warming. The only question is how much are we contributing to it, and how much is just a natural process that we are caught up in.

For more information, see the link I provided a few posts back.

We succeeded in taking that picture [from deep space], and, if you look at it, you see a dot. That's here. That's home. That's us. On it everyone you know, everyone you love, everyone you've ever heard of, every human being who ever was, lived out their lives. The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines. Every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived there - on a mote of dust suspended in a sunbeam.
The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that in glory and triumph they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of the dot on scarcely distinguishable inhabitants of some other corner of the dot. How frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light.

Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity -- in all this vastness -- there is no hint that help will come from elsewhere to save us from ourselves. It is up to us. It's been said that astronomy is a humbling, and I might add, a character-building experience. To my mind, there is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly and compassionately with one another and to preserve and cherish this pale blue dot, the only home we've ever known.

Whether you believe man is changing the climate or not, taking care of the only home we have seems like a good idea to me. I suppose if you are not worried about the world future generations will have to face this might not be a concern, but I'd say that is pretty selfish.

Since we don't know, and this is all we've got; why take a chance?

I agree that voluntarily saving energy makes good sense all around.

I think it's all in what time period you are using when you try to define a trend.

I agree that voluntarily saving energy makes good sense all around.

Extremist stuff like eliminating the combustion engine scares me too. They might mean well, but let's face it, that is not even close to realistic at this point.

You know you live in Michigan when you've used to AC and Heat all in the same day (haha).