The AGCI Virtual Classroom

Maroon Bells - Aspen, CO
Natural changes that occur within a human lifetime are most obvious to us when the scale and time of the change match our daily lives. Seasonal change in leaf color primarily in deciduous forests of mid-latitudes fits this pattern.

Mt. Everest - Tibet
While often not perceptible on human timescales, geologic formations such as the Himalayas are in a constant state of motion and change. For example, Mt. Everest, the world's highest mountain, began to form some 55 million years ago during the collision between two massive continental plates. Mt. Everest appears to still be growing by about 4 mm (0.15 inches) each year.

Coral Reef - Red Sea, Egypt
Scientists have identified some 1.6 million species with an unknown number yet to be discovered. New species evolve while others become extinct. These changes occur through the process of evolution resulting in the tremendous biodiversity we can witness today such as in coral reefs, where some 90.000 unique species have been described.

American Falls - Niagara, New York
The sun drives the hydrologic cycle of our water planet, moving water from the oceans to the atmosphere and back to the earth's surface as snow and rain. Water in motion is a major driver of erosion altering landforms and filling streams, lakes, and the continental shelf with sediment.

Rice Harvesting - Vietnam
Growing food requires the delivery of key ingredients from the natural world, such as carbon, hydrogen, oxygen nitrogen, phosphorus, and potassium. Each of these are distributed globally by interactive geologic, hydrologic, atmospheric, biologic, and chemical processes.

Arctic Sea Ice - North Pole Region
The brightness of snow and ice alter the energy balance of earth by reflecting sunlight back to space. On land, high-altitude cold snowpack regions serve as a store of freshwater providing a reliable supply for billions of people worldwide during critical agricultural irrigation periods of mid to late summer. Sea level rise and fall over geologic time resulting from melting glaciers and ice-caps significantly alters the size of continents, coastal ecosystems, and biogeographic barriers important in evolution.

Shanghai, China
Often displaying imposing skylines, the world's great urban locales are a testament to the unique human ability to create their own environment. However, these transformations can cause major disturbances to existing natural systems.

Open Pit Mine - Chuquicamata, Chile
To satisfy the needs of the global human population, an enormous amount of resources are required. As a result, large-scale operations, such as open pit mining, are needed to meet the demand. The mine pictured here is about 830 meters (about half a mile) deep, a depth greater than the world's tallest building.
(Photo credit: Peter McBride)

Hubbard Glacier, Alaska
Combustion of fossil fuel has released over 500 billion tons of carbon into the atmosphere since the industrial revolution. This quantity of carbon in the form of carbon dioxide is significant in that it has trapped enough heat to change the global average temperature 0.8 deg C (1.5 deg F) in a little over a hundred years -- enough of a change to set most glaciers worldwide into an extended retreat.

Mt. Pinatubo, Philippines
When Mt. Pinatubo erupted in 1991, it sent 10 billon metric tons of magma into the air, as well as 20 billion tons of sulfur dioxide--making it the largest eruption of the 20th century. This debris encircled the globe, lingering for over a year and causing average global temperature to temporarily fall by nearly 0.5 degree C (0.9 degree F).

Pollution Graveyard
Seemingly small harmless human actions can wreck major havoc on Earth systems far and wide. For instance, the use of chloroflurocarbons (CFCs) in refrigerants, foam insulation, and electronic cleaning fluids) have contributed significantly to the thinning of the ozone layer of the atmosphere up until the Montreal Protocol stipulated the phasing out of their use internationally. The "ozone hole" is slowly recovering as the levels of chlorine in the stratosphere diminish.

Cows - Nebraska, USA
A surprising fact about global change is that livestock raised for human consumption plays a significant role in global methane and nitrogen cycles. It is estimated that livestock accounts for 18% of all human-induced greenhouse gas emissions. Emissions come from the land and energy required to raise the heifers, but significant amounts also originate from the digestive system of the animals themselves.

Polar Bear -Arctic Sea
In a warming world, polar bears face dramatic changes to their habitat, threatening their continued existence. Although many other species face similar threats around the world, not all forms of life are adversely affected. Some species are expected to thrive on a warmer planet.

Bleached Coral - St. Croix, US Virgin Islands
Delicate ecosystems such as coral reefs face particular danger from global change. Since coral can thrive within only a narrow range of conditions, human-caused impacts on the ocean such as global warming, pollution, and ocean acidification put the entire ecosystem in peril. If current trends continue, some projections find that most or all of suitable coral reef habitat will vanish by 2050. (Photo Credit: NOAA Coastal Monitoring and Assessment)

Mesa Verde National Park - Colorado, USA
Human life is not immune to the impacts of global change. In the past, peoples such as the Anasazi, which dwelled in places like Mesa Verde, are thought to have been driven away from their cliff dwellings by changing climatic patterns altering reliable food supplies. Present day climate change also poses a similar challenge to the human way of life. Over this century reduced mountain snowpack may force the failure of crops dependent on mid to late summer streamflows for irrigation--a serious threat to millions of people.