"Not only is the ozone layer getting better, we feel it is due to the Montreal Protocol," she added in an interview.

The depletion of the ozone layer, which absorbs most of the harmful effects of the sun's ultraviolet radiation, increases the risk of skin cancer and cataracts in humans and may harm crop yields and sea life.

Despite the signs of recovery, Weatherhead, who reported the findings in the journal Nature, said people should still protect themselves from harmful ultraviolet rays.

Weatherhead and Signe Bech Anderson of the Danish Meteorological Institute in Copenhagen analyzed data from satellites and ground stations and information from 14 modeling studies.

They found that ozone levels have stabilized or increased slightly in the past 10 years. But full recovery is still decades away.

The researchers said depletion has been most severe at the poles and to a lesser extent at mid-latitudes covering bands of North America, South America and Europe.

Shifting temperatures, greenhouse gases, nitrous oxide (N20) and atmospheric dynamics, which can influence ozone levels, are going to change in the future, they added.

"Therefore we really don't think ozone is going to stabilize back to its pre-ozone-depleting-substance levels," Weatherhead said.

Volcanic activity on Earth also has an impact. The 1993 Mount Pinatubo eruption in the Philippines caused ozone levels to backslide for several years, according to the researchers.

El Ninos boost rainfall in the southern United States and western South America and bring dry weather or even drought to Indonesia, Malaysia and elsewhere in the western Pacific.

As for the Pacific food chain near the equator, the slowdown might reduce populations of tiny plants and animals up through the fish that eat them, because of reduced nutrition welling up from the deep, said the author, Gabriel Vecchi.

Vecchi, a visiting scientist at a National Oceanic and Atmospheric Administration lab in Princeton, N.J., and colleagues present their results in Thursday's issue of the journal Nature.

The slowdown was detected in shipboard and land-based data going back to the mid-1800s. It matches an effect predicted by computer climate simulations that trace global warming to a build-up of heat-trapping greenhouse gases, the researchers report. But simulations that consider only natural influences fail to produce the observed slowdown, Vecchi said.

So, it appears the slowdown is largely due to the man-made buildup of greenhouse gases, the researchers concluded. And the result lends more credibility to computer models that trace global warming to greenhouse gases, at least for their ability to forecast what will happen in the tropics, Vecchi said.

The study focused on what scientists call the Walker circulation, a huge wind pattern that covers almost half the circumference of Earth.

The pattern traces a huge loop. Trade winds blow across the Pacific from east to west. The air rises in the western Pacific and then returns eastward at an altitude of a few miles. Then it sinks back to the surface and starts the loop again.

The new study is based on barometric pressure readings, since differences in air pressure drive winds near the equator. Results suggest the average wind speed in the Walker circulation has weakened by about 3.5 percent since the mid-1800s. It has weakened faster since World War II than in the long-term trend since the mid-1800s, Vecchi said.

Computer simulations say the circulation might weaken another 10 percent by 2100, Vecchi said.

Dennis Hartmann, a professor of atmospheric sciences at the University of Washington, said the study makes a strong case that the Walker circulation has slowed. While such an effect had been predicted as a result of global warming, he said, "it's not been demonstrated before as clearly as they've done here."

A small long-distance migrating bird called the pied flycatcher (Ficedula hypoleuca) spends the northern hemisphere winter in West Africa, returning to northern Europe in the spring to breed.

Dutch researchers have been following the species for decades, using nestboxes in forests, observations of their arrival and departure and monitoring availability of their staple food, which is caterpillars.

They have found that the earlier arrival of warm weather causes the caterpillars to emerge sooner -- and as a result, the flycatchers may arrive too late to properly feed their young. The birds breed, but without having an adequate food supply for the nestlings.

The team, lead by Christian Both of Groningen University, looked at population numbers and caterpillar availability from 1987 to 2003.

An early food peak caused flycatcher numbers to decline by a stunning 90 percent. But when the caterpillars peaked later, the decline was only 10 percent.

"Mistiming as a result of climate change is probably a widespread phenomenon," says Both. "(The) evidence (is) that it can lead to population declines."

Statistics from the Tibet weather bureau show that average temperatures in Tibet have risen by 0.9 degree Celsius (2 Fahrenheit) since the 1980s, Xinhua reported, quoting Han Yongxiang of the National Meteorological Bureau.

The glaciers in the Qinghai-Tibet plateau account for 47 percent of China's total glacier coverage, according to Xinhua.

The melting glaciers will eventually lead to drought, more desertification and an increase in the number of sandstorms, Xinhua quoted researcher Dong Guangrong at the Chinese Academy of Sciences as saying.

The spread of deserts and sandstorms are already pressing problems in China.

The severity of China's sandstorms was highlighted by the onslaught of 300,000 metric tons (330,000 short tons) of dust in capital Beijing two weeks ago. Dust was blown as far away as South Korea and Tokyo.

Beijing has approved programs to reclaim land by planting hardy grasses and shrubs on 30 percent of the country's 700,000 square miles of desert by 2050.

Workers have already planted thousands of acres of vegetation to stop the spread of deserts in China's north and west.