Discovery Science: Earth – Atmosphere – Global Warming

Earth Science: Atmosphere – Global Warming

Regardless of the degree to which human activity affects the world’s climate, the fact remains: it is getting warmer. This rise in temperature can no longer be explained on the basis of natural climatic cycles alone.

Over the course of geological history, the Earth’s climate has undergone numerous changes. The past million years, in particular, have been marked by continuous cycles of rising and falling temperatures.

Average global temperatures have fallen below 50°F (10°C) during cold phases, followed by increases of up to 62°F (17°C) during warm periods. Even since the most recent ice age, climatic cycles have continued, with temperatures some 1.8-3.6°F (1-2°C) above and below today’s average value of 58°F (14.5°C).

Nevertheless, the unusually rapid warming of the climate in recent years is cause for concern. During the past 120 years, worldwide average temperatures have risen by some 1.26°F (0.7°C), with the most significant increases registered since the early 1970s. The direct consequences of this warming include the melting of mountain glaciers, the retreat of polar ice, increases in extreme weather phenomena, and rising sea levels—with an average increase of some 6.7 inches (17 cm) observed in the 20th century alone.

According to reports from the Intergovernmental Panel on Climate Change, the main cause of the excess warming is the burgeoning concentration of greenhouse gases in the atmosphere as a result of human activity. During the 10,000 years before 1750, atmospheric carbon dioxide (CO2) levels never exceeded 280 parts per million (1 ppm = 0.001 percent). Since 1750 this concentration has shown an accelerating rise, reaching over 380 ppm today.

The upward curve is chiefly explained by the burning of fossil fuels and clearing of old-growth forests. Over the same time period, the concentration of methane, another greenhouse gas, also rose by 148 percent, mainly due to the expansion of mass livestock operations. If the proportion of these gases in the atmosphere continues to grow, a climatic catastrophe can be expected.


In 1988, the Intergovernmental Panel on Climate Change (IPCC) was founded by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP).

The panel, staffed by experts from more than 130 nations, collects, analyzes, and evaluates the latest scientific research and international studies related to the causes and possible effects of global warming.

Since 1990, its findings have been published regularly in the form of status reports, which serve as a basis for negotiations at international climate conferences.


GREENHOUSE GASES Carbon dioxide (CO,) is one of the six types of greenhouse gas regulated within the framework of the Kyoto Protocol, along with methane (CH,), nitrous oxide (N,0), hydrofluorocarbons (HFCs). perfluorocarbons (PFCs). and sulfur hexafluoride (SF6)

CO2 is emitted through the respiration processes of plants and animals, as well as the burning of wood and fossil fuels (coal, oil. and natural gas), while oceans and forests remove CO, from the atmosphere.