Jetting Their Way to a Better Understanding of Global Warming

By Douglas Fischer

CO2 JET: Scientists have outfitted a Gulfstream jet to make precise measurements of greenhouse gases in the atmosphere.

BOULDER—Scientists have taken the first crack at solving a fundamental climate mystery, criss-crossing the globe in a souped-up corporate jet to determine where and when greenhouse gases enter and leave the atmosphere.

An understanding of how these climate-warming gases move about the globe is a critical prerequisite for any policy aimed at curbing global warming, scientists said Thursday, and information gained over the next three years will play a crucial role in sharpening future predictions and improving their accuracy.

Using a high performance jet, scientists will take a series of "slices" of the atmosphere over the next few years from pole to pole and from the surface to the atmosphere's upper reaches.

They are expected to return from their first mission this week—a series of 11 flights from Colorado to the Arctic Circle to Tahiti, Antarctica, Easter Island and Costa Rica. Scientists running the instruments say they have seen several "wonderful jewels" in the raw data that challenge current thinking and assumptions.

When all the measurements are assembled, scientists added, they will for the first time have a picture of the atmosphere—and a global snapshot showing where and when some of the estimated 30 billion tons of carbon emitted annually by cars, factories, deforestation and other human activities enters the atmosphere.

"We were essentially retracing Captain Cook's voyages—obviously much later and with much more sophisticated instruments, but with some very similar parallels," said Britton Stephens, a scientist with the National Center for Atmospheric Research and one of the project's principal investigators.

"When he set sail, he knew the ocean was out there, but didn't really know the details. Similarly, we've been standing on the edge of the atmosphere—the surface—but we don't really know the details."

Researchers expect the $4.5 million mission to provide several critical answers to atmospheric riddles, but the two most important are fundamental to any effort to curb climate change, team members said during a conference call with reporters near the end of the first of five missions:

First, the project will fill key gaps in our understanding of how carbon cycles through the atmosphere and among the earth, air and oceans. Roughly half the carbon emitted by humans stays in the atmosphere, with the remainder being absorbed by ocean and earth ecosystems. But scientists don't understand how the system works or how quickly various gases mix.

The result, Stephens said, is that models of this so-called carbon cycle grown wildly divergent as they are projected into the future, with nearly 100 percent uncertainty by 2050.

Second, and perhaps most important, the map will provide a baseline against which efforts worldwide to curb carbon emissions can be judged. Need for such a benchmark has gained urgency, scientists and policymakers say, as the world moves toward regional, national and international agreements to limit greenhouse gases.

"If we expect to make treaties," said Steven Wofsy, a Harvard University professor of atmospheric and environmental science and another principal investigator, "those treaties have to be based on sound science. This slice of the atmosphere is going to help us understand that."

The effort is distinctly different from other efforts—such as the launch last week of a Japanese research satellite—to map carbon dioxide. Most measurements to date look solely at points on the surface. Satellite pictures can see broad swathes of the Earth but with very fuzzy resolution. This work, scientists said, examines nearly 100 different greenhouse gases in very fine detail at almost every altitude.

They have seen some "stunning" things: ground-level ozone, or smog, through the entire depth of the Northern Hemisphere at nearly triple the concentration observed in the Southern Hemisphere; a cloud of industrial pollutants sitting above the Arctic; a large mass of oxygen above the Southern Ocean.

"It supports the view of people who say there's a very big effect of pollution, even in the wintertime," Wofsy said.

To map the atmosphere, scientists are flying a specially equipped Gulfstream V jet, owned by the National Science Foundation and operated by Colorado-based NCAR.

The plane has a range of 7,000 miles, allowing researchers to traverse vast swathes of the Pacific without refueling. Extraordinarily powerful engines allow the jet to cruise at altitudes from 1,000 feet to 47,000 feet, into the lower stratosphere nearly nine miles up.

In contrast, a typical Boeing 767 has a range of about 4,000 miles and cruises at about 35,000 feet.

And while the jet started as a luxury corporate item, it is now anything but: the cabin is stuffed with pipes, pumps, filters, analyzers, sensors computers and other laboratory equipment. They have drilled holes through the fuselage so lasers could point up and down, added pods and intake valves, ditched the leather.

"We have the equivalent of a very expensive laboratory where we can sit behind our instruments as we're going along," Stephens said.

Scientists from NCAR, Harvard, the National Oceanic and Atmospheric Administration, the Scripps Intitution of Oceanography, the University of Miami and Princeton University will complete this week the first of five missions. They left Jan. 8, flying from Colorado to Alaska and the Arctic Circle, then south to New Zealand and Antarctica. Late this week they will return from Costa Rica to Colorado.

Four subsequent missions through mid-2011 will follow similar flight paths but at different times of the year, providing a range of seasonal snapshots of greenhouse gas emissions.

The research will help answer such questions as why atmospheric levels of methane, a potent greenhouse gas, have tripled since the Industrial Age and are on the rise again after leveling off in the 1990s. They will also answer how gases and particles in the atmosphere affect temperatures by influencing clouds or the amount of solar heat reaching the Earth's surface.

And by ramming their data, along with long-standing surface measurements, through computer models, they hope to expose the weaknesses of current projections.

"Some modeling approaches will simply fail," Wofsy said. "They won't be able to do this. That's what we're after here: We're confronting these global models with data."

And the experiment is also confronting scientists with a bit of perspective.

"It's quite an experience to fly in an airplane above the Arctic ice sheet, with moonlight illuminating it, and then a short time thereafter be above American Samoa and the lush tropical forest, and then a short time later be over New Zealand," Wofsy said. "It really gave a strong sense of the interconnection of the globe."

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Is there a Planet X?

by Govert Schilling

Artist's conception of a Kuiper Belt Object. These icy bits of debris pepper space from Neptune's orbit at 30 astronomical units out to around 50 AU (Image: T Pyle (SSC) / JPL-Caltech / NASA)

If we know enough to say the solar system is a filigree construction, we might reasonably assume we know where all its bits are. But lurking in the solar system's dark recesses, rumour has it, is an unsighted world - Planet X, a frozen body perhaps as large as Mars, or even Earth.

Planet X would be the most significant addition to the solar system since the discovery of Pluto, the now notorious non-planet, in 1930. When the International Astronomical Union voted to downgrade Pluto to dwarf planet status in 2006, they established three criteria for a fully blown planet in our solar system: it must orbit the sun; its gravity must suffice to mould it into a near-spherical shape; and it must be massive enough to have ploughed its orbit clear of other bits and bobs. Pluto falls down on this third point. It is just one of many Kuiper belt objects (KBOs), icy bits of debris that pepper space from Neptune's orbit at 30 astronomical units out to around 50 AU, where 1 AU is the distance between Earth and the sun.

Any new object would have to be well clear of the Kuiper belt to qualify as a planet. Yet intriguingly, it is studies of the belt that have suggested the planet's existence. Some KBOs travel in extremely elongated orbits around the sun. Others have steep orbits almost at right angles to the orbits of all the major planets. "Those could be signs of perturbation from a massive distant object," says Robert Jedicke, a solar system scientist at the University of Hawaii.

That is by no means a general consensus. An early, slow outward migration of the giant planets (see "How was the solar system built?") could also explain some of these strange KBO orbits - although it has difficulty explaining all of the belt's observed properties.

Over the past 20 years, huge swaths of the sky have been searched for slowly moving bodies, and well over 1000 KBOs found. But these wide-area surveys can spot only large, bright objects; longer-exposure surveys that can find smaller, dimmer objects cover only small areas of the sky. A Mars-sized object at a distance of, say, 100 AU would be so faint that it could easily have escaped detection.

That could soon change. In December 2008, the first prototype of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) was brought into service at the Haleakala observatory on Maui, Hawaii. Soon, four telescopes - equipped with the world's largest digital cameras, at 1.4 billion pixels apiece - will search the skies for anything that blinks or moves. Its main purpose is to look out for potentially hazardous asteroids bound for Earth, but inhabitants of the outer solar system will not escape its all-seeing eyes.

Jedicke and his team are busy developing software to spot objects automatically using Pan-STARRS. The discovery of a further planet would be thrilling, he says. The only explanation for its presence there would be that large bodies coalesced very early in the solar system's history, only to be ejected by the gravity of the giant planets later on. That would firm up our ideas about how the solar system must have developed, and perhaps be a stepping stone towards its even more distant recesses (see "Where do comets come from?").

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Why are the sun and moon the same size in the sky?

by Marcus Chown

The "diamond ring" effect is seen toward the end of a total solar eclipse, as the Moon just begins to reveal the Sun's bright surface (photosphere) at the end of totality. This eclipse was photographed from Bolivia on 3 November 1994 (Image: Reverend Ronald Royer / SPL)

It is one of the most glorious pieces of natural theatre. Assuming you spend your life on the same part of the Earth's surface, you might witness it once - if you are particularly lucky or very long-lived, perhaps twice. But a total solar eclipse is worth the wait. At the height of totality, the fit of sun and moon is so perfect that beads of sunlight can only penetrate to us through the rugged valleys on the lunar surface, creating the stunning "diamond ring" effect.

It is all thanks to a striking coincidence. The sun is about 400 times as wide as the moon, but it is also 400 times further away. The two therefore look the same size in the sky - a unique situation among our solar system's eight planets and 166 known moons. Earth is also the only planet to harbour life. Pure coincidence?

Almost undoubtedly, say most astronomers. But perhaps it is not so much of one as the bare numbers suggest. Our moon is different. The many moons of the large outer planets - Jupiter, Saturn, Uranus and Neptune - are thought to have originated through one of two processes: from the accretion of a disc of material in the planet's gravity field, in a miniature version of the formation of the solar system's planets, or through the later gravitational capture of passing small bodies. The second possibility is also thought to account for Mars's two small satellites, Deimos and Phobos, the only other moons in the inner solar system.

But our moon is simply too big relative to Earth's own size to have formed easily by either of these processes. Planetary scientists believe there can be only one explanation: in the first 100 million years of the solar system, when unattached debris was still zinging around the inner solar system, a Mars-sized object smashed into Earth. That impact radically remodelled our planet, expelling a huge amount of debris that eventually congealed into our oversized moon.

And here's the best bit. Such a big moon is a big boon for life on Earth. As Earth spins on its own axis, it has a natural tendency to wobble, owing to the varying pull on it from other bodies such as the sun. The unseen hand of the moon's gravity gently damps that wobble, preventing rotational instabilities which would otherwise have caused dramatic changes in Earth's climatic zones over time. Such instabilities would have made it much more tricky for life to get started on our planet.

Earth's position in the "habitable zone" around the sun where liquid water is abundant is undoubtedly the single most important factor in its fecundity. But the presence of a large moon - one large enough to cause total eclipses - might also have been crucial. If so, that has important consequences for the search for life on other planets.

Since the impact that created it, the moon has been moving steadily away from us, currently about 3.8 centimetres per year. The dinosaurs did not see eclipses like we do: the moon was too close 200 million years ago, more than big enough in the sky to block out the entire sun. Equally, any occupants of Earth in a couple of hundred million years' time will not see total eclipses at all, as the moon will appear too small.

Our luck seems the result of two coincident timescales: that of the recession of an impact-formed moon, and that for the evolution of intelligent life. If you should be fortunate enough to experience a total eclipse in your lifetime, consider this intriguing possibility: that large moon might be the reason you are there.

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