Climate conditions

This crack in Greenland's Petermann Glacier is expected to some day completely sever, creating a large iceberg that will float away. Parts of Greenland's vast ice cover are speeding up their flow into the sea, adding a bit each year to rising sea levels.

The Arctic's sea ice recedes each summer but experts fear that human emissions of greenhouse gases are impacting what is an otherwise natural process. The 2009 season saw the third largest retreat since satellite records began in 1979. Satellite data was used to map the extent on July 1, at top, and Sept. 7, which was the lowest point of the summer. The two previous years were the lowest on record, and data for the three years points to a worrisome trend, say experts at the National Snow and Ice Data Center.

Climate change also impacts ocean ecosystems, from coral reefs to fish populations. These tuna fishermen in Bali, Indonesia, live in an area known as the "Coral Triangle" because of its wealth of coral species. But rising water temperatures, sea levels and water made more acidic by carbon dioxide are threatening to destroy that coral kingdom.

Reefs like this one off Batangas Bay, south of Manila, Philippines, provide life not only to tiny coral but to the fish that live in and feed off the reefs.

A rare and endangered blue whale swims off Long Beach, Calif. In decades past, blue whales were rarely seen along California's coastline but their migration and feeding patterns are changing. In recent years sightings in Southern California have increased dramatically. Scientists suspect that climate change is among the factors having an effect on the food of the blues, the largest animal on Earth.

The Indian Ocean nation of Maldives built this raised island in the 1990s to try to keep ahead of rising seas. The nation's main island, Male, is even flatter and fears are that the nation could disappear by the end of the century.

Attempts to reduce emissions of greenhouse gases caused by burning fossil fuels includes a boom in wind power. This wind farm, the world's largest offshore, was built in 2009 off the west coast of Denmark near Esbjerg. The platforms are anchored to the sea floor.

Students plant mangroves at a conservation area in Jakarta, Indonesia. Native to many coastlines, mangroves are a natural buffer against storm surges and even rising seas.

Deforestation is a major source of greenhouse gases in the developing world. This area was being cleared in Indonesia where the forest is being replaced with palm oil farms.

Experts warn that global warming will mean more, and more severe, droughts in parts of the world such as southern Brazil, where a dry spell in 2009 left fields like this one unusable.

An endangered red eyed tree frog rests on a leaf at a nature reserve in Heredia, Costa Rica. Tropical frogs have been in decline and experts believe warming temperatures are making it hard for them to adapt quickly.

The Kibera slum in Nairobi, Kenya, is a perfect candidate for the kind of climate "megadisasters" that U.N. staff warn of should warming increase the severity of weather extremes from heat waves to floods.

These farmers in western Uganda rely on water from glaciers atop the the Rwenzori Mountains, yet like most glaciers around the world Uganda's are receding rapidly.

A squatters' site is destroyed during a raid aimed at protecting Brazii's vast central savannah region. Illegal farming and settlements have destroyed tens of thousands of square miles of forest in recent years, removing trees and other plants that would have eased the climate impact by absorbing carbon dioxide from the atmosphere.

Beijing is known for the almost constant air pollution that hangs over China's capital. Efforts to curb smog by making cars cleaner has had a secondary effect of reducing greenhouse gas emissions.

China has embarked on a clean energy push that includes building nuclear power reactors like this one in Zhejiang Province. While storing nuclear waste is an environmental issue in itself, nuclear power produces no greenhouse gases.

A worker unloads coal from a freight train in Xiangfan, China. The nation is still dependent on coal-fired power plants, a major source of carbon dioxide emissions.

Within the United States, the Colorado River has been cited as an example of direct impacts from warming temperatures. The river system, which supplies much of California's water, is being stressed by drought and an increasing population in the West.

President Barack Obama, left, has showcased clean energy with trips like this one to a massive solar power installation at Nellis Air Force Base in Las Vegas, Nev.

The United States still relies on coal for power given a large supply and relatively low costs. Critics counter that carbon dioxide emissions from burning coal are enormous and that the mining process includes practices like removing mountaintops to get to the coal -- which is what happened here at Kayford Mountain, W. Va.

Beetles and wildfires are consuming Western forests like this area in Canada in what scientists say is a preview of a warmer future in which dying, burning forests would then only add to the warming.

Coal-fired power plants like this one in Poland -- the largest in Europe -- emit soot pollutants as well as carbon dioxide but also help power industry and homes around the world. This infrastructure won't vanish any time soon, so experts are looking for ways to capture and then safely store the carbon dioxide so that their climate impact is reduced.