Cleaning Up the Atmosphere

Is North America really cleaning up after itself? Last year, the tentative answer seemed to be a surprising yes, at least for many experts.

Every year, human civilization adds 6 billion or 7 billion tons of carbon to the atmosphere (in the form of carbon dioxide and related gases), but only about half stays there. The rest is somehow sopped up by oceans and land, which serve as carbon "sinks" in ways that are still uncertain.

In 1998, a celebrated analysis of carbon dioxide emissions published in the journal Science concluded that the plants and soils of the United States and southern Canada were actually sucking up as much CO2 as both societies put out. In fact, according to that study, North America tucked away a whopping 1.7 billion metric tons of carbon per year--nearly all of the amount sequestered by land everywhere in the Northern Hemisphere.

Now a new study in the July 23 issue of Science questions that estimate. Researchers from the Woods Hole Research Center in Massachusetts examined the pattern of land-use change in the United States and calculated that from 1700 to 1945, deforestation, fossil-fuel burning and the like put about 27 billion tons of carbon into the air. But since 1945, the abandonment of cropland, fire suppression efforts and forest growth have pulled about 2 billion tons out. However, the authors note, all the recent land-use changes would offset only "10 to 30 percent of U.S. fossil fuel emissions."

Watch that space.

How Hard Can a Comet Hit?

Scientists have developed a new method for assessing the risk of comets and asteroids that might hit Earth. Similar to the Richter scale used for earthquakes, the Torino Impact Hazard Scale is named for the Italian city in which the scale was initially adopted by the International Astronomical Union in June. It was officially endorsed at the United Nations' UNISPACE III conference in Vienna last week.

The scale uses colors from white to red, and numbers from zero to 10, to assess the size and speed of celestial objects, as well as their chances of striking Earth. An object rated at zero or one, in the white zone, presents no threat of damage. A red 10 means certain global catastrophe, such as the impact that many think wiped out the dinosaurs and other species 65 million years ago.

With increasingly sophisticated observing instruments, more asteroids than ever are being detected in the cosmic shooting gallery near Earth. Richard Binzel of the Massachusetts Institute of Technology in Cambridge, who created the scale, said he hopes it will assuage public concerns about a doomsday collision. He notes comfortingly that all currently known asteroids have scale values of zero.

Medicine's Common Language

The language of medicine is complicated to begin with, and it's made all the more so by doctors' personal idiosyncrasies, which tend to make medical charts less useful than they could be.

But if doctors used a standardized or "canonical" vocabulary for everything, and typed it into a computerized patient chart system, hospital computer programs could more easily ensure that the right drugs are prescribed to the right patients, proper educational materials are forwarded to patients who need them, and billing information is handled properly.

Many researchers have tried to develop such a language--a limited vocabulary that doctors could stick to in which every word has a precise, agreed-upon meaning.

Now scientists report the most efficient system yet. They took all 891,770 medical chart comments written by 1,961 doctors for 74,696 patients who passed through an Atlanta hospital over six years, and boiled those comments down to a mere 15,534 proposed "canonical" comments. The idea was to use as few words as possible to say everything that needed to be said, without losing anything in the translation.

To see how well the proposed language captured what the doctors had intended to convey, the researchers gave the newly distilled charts for 234 patients back to their 36 doctors. The doctors reported that the condensed comments "completely captured their clinical intent" 84 percent of the time. Three percent of the chart comments were judged to be misleading or clinically dangerous, the researchers report in the July 20 Annals of Internal Medicine.

The Magnetic Eye of Newts

Weird but true: Recently, scientists have found that several kinds of animals carry a sort of on-board compass system that allows them to orient themselves in Earth's magnetic field.

For certain birds, insects and amphibians, that mechanism seems to be located in the eye and involves some peculiar interaction between magnetic field and light-detecting tissues: When a researcher changes the wavelength of light that the animals receive, it also alters their sense of magnetic direction.

But in at least one critter, compass orientation takes place outside the eye, biologists report in the July 22 issue of Nature. Newts have "extraocular" spots on their heads that respond to light via the brain's pineal gland or possibly the hypothalamus.

A team from Indiana University placed two kinds of transparent "caps"--in effect, tiny sunglass lenses one-quarter of an inch wide--over these photoreceptors. Half were clear; half allowed only long-wavelength light to pass through. In tests, newts with long-wavelength caps oriented themselves at a 90-degree angle to those with clear caps. "Thus," the researchers conclude, "extraocular photoreceptors are involved in the newt's light-dependent magnetic compass."