Global Warming

GLOBAL WARMING

Global warming is posing a drastic hazard to our environment

Global warming or Climate change is a hot topic for
environmentalists today

Fingerprints:
Direct manifestations of a widespread and long-term trend toward warmer global temperatures
Heat waves and periods of unusually warm weather
Ocean warming, sea-level rise and coastal flooding
Glaciers melting
Arctic and Antarctic warming
Harbingers:
Events that foreshadow the types of impacts likely to become more frequent and widespread with continued warming.
Spreading disease
Earlier spring arrival
Plant and animal range shifts and population changes
Coral reef bleaching
Downpours, heavy snowfalls, and flooding
Droughts and fires

Climate Change or Global Warming?
The term climate change is often used interchangeably with the term global warming, but according to the National Academy of Sciences, "the phrase 'climate change' is growing in preferred use to 'global warming' because it helps convey that there are [other] changes in addition to rising temperatures."

Climate change refers to any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer). Climate change may result from:
natural factors, such as changes in the sun's intensity or slow changes in the Earth's orbit around the sun;
natural processes within the climate system (e.g. changes in ocean circulation);
human activities that change the atmosphere's composition (e.g. through burning fossil fuels) and the land surface (e.g. deforestation, reforestation, urbanization, desertification, etc.)
Global warming is an average increase in the temperature of the atmosphere near the Earth's surface and in the troposphere, which can contribute to changes in global climate patterns. Global warming can occur from a variety of causes, both natural and human induced. In common usage, "global warming" often refers to the warming that can occur as a result of increased emissions of greenhouse gases from human activities.
Top of Page

Basic Information
The Earth's climate has changed many times during the planet's history, with events ranging from ice ages to long periods of warmth. Historically, natural factors such as volcanic eruptions, changes in the Earth's orbit, and the amount of energy released from the Sun have affected the Earth's climate. Beginning late in the 18th century, human activities associated with the Industrial Revolution have also changed the composition of the atmosphere and therefore very likely are influencing the Earth's climate.

Science
For over the past 200 years, the burning of fossil fuels, such as coal and oil, and deforestation have caused the concentrations of heat-trapping "greenhouse gases" to increase significantly in our atmosphere. These gases prevent heat from escaping to space, somewhat like the glass panels of a greenhouse.
Greenhouse gases are necessary to life as we know it, because they keep the planet's surface warmer than it otherwise would be. But, as the concentrations of these gases continue to increase in the atmosphere, the Earth's temperature is climbing above past levels. According to NOAA and NASA data, the Earth's average surface temperature has increased by about 1.2 to 1.4ºF in the last 100 years. The eight warmest years on record (since 1850) have all occurred since 1998, with the warmest year being 2005. Most of the warming in recent decades is very likely the result of human activities. Other aspects of the climate are also changing such as rainfall patterns, snow and ice cover, and sea level.
If greenhouse gases continue to increase, climate models predict that the average temperature at the Earth's surface could increase from 3.2 to 7.2ºF above 1990 levels by the end of this century. Scientists are certain that human activities are changing the composition of the atmosphere, and that increasing the concentration of greenhouse gases will change the planet's climate. But they are not sure by how much it will change, at what rate it will change, or what the exact effects will be. See the Science and Health and Environmental Effects sections of this site for more detail, or review the answers to some frequent science questions.

Greenhouse Gas Emissions
More than half the energy-related emissions come from large stationary sources such as power plants, while about a third comes from transportation. Industrial processes (such as the production of cement, steel, and aluminum), agriculture, forestry, other land use, and waste management are also important sources of greenhouse gas emissions.

Health and Environmental Effects
Climate change affects people, plants, and animals. Scientists are working to better understand future climate change and how the effects will vary by region and over time.
Scientists have observed that some changes are already occurring. Observed effects include sea level rise, shrinking glaciers, changes in the range and distribution of plants and animals, trees blooming earlier, lengthening of growing seasons, ice on rivers and lakes freezing later and breaking up earlier, and thawing of permafrost. Another key issue being studied is how societies and the Earth's environment will adapt to or cope with climate change.
Human health can be affected directly and indirectly by climate change in part through extreme periods of heat and cold, storms, and climate-sensitive diseases such as malaria, and smog episodes. For more information on these and other environmental effects, please visit the Health and Environmental Effects section of this site, or review the answers to some frequent effects questions.

What You Can Do
Greenhouse gases are emitted as a result of the energy we use by driving and using electricity and through other activities that support our quality of life like growing food and raising livestock. Greenhouse gas emissions can be minimized through simple measures like changing light bulbs in your home and properly inflating your tires to improve your car's fuel economy. The What You Can Do section of the climate change site identifies over 25 action steps that individuals can take to decrease greenhouse gas emissions, increase the nation's energy independence and also save money.
State and local governments and businesses play an important role in meeting the national goal of reducing greenhouse gas intensity by 18 percent by 2012. For example, major corporations, states and local organizations are taking action through participation in a wide range of EPA and other federal voluntary programs.
You can start by assessing your own contribution to the problem, by using EPA's personal greenhouse gas emissions calculator to estimate your household's annual emissions. Once you know about how much you emit, you use the tool to see how simple steps you take at home, at the office, on the road, and at school can reduce your emissions.
Top of Page

Global Warming
The term "global warming" refers to the warming in recent decades and its projected continuation, and implies a human influence. The United Nations Framework Convention on Climate Change (UNFCCC) uses the term "climate change" for human-caused change, and "climate variability" for other changes. The term "climate change" recognizes that rising temperatures are not the only effect. The term "anthropogenic global warming" is sometimes used when focusing on human-induced changes.

Global mean surface temperature anomaly relative to 1961–1990
Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980Global warming is the increase in the average measured temperature of the Earth's near-surface air and oceans since the mid-20th century, and its projected continuation.

The average global air temperature near the Earth's surface increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 years ending in 2005. The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic (man-made) greenhouse gas concentrations" via an enhanced greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.

These basic conclusions have been endorsed by at least 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries. While individual scientists have voiced disagreement with some findings of the IPCC, the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.

Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century. This range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.

Increasing global temperature is expected to cause sea levels to rise, an increase in the intensity of extreme weather events, and significant changes to the amount and pattern of precipitation, likely leading to an expanse of tropical areas and increased pace of desertification. Other expected effects of global warming include changes in agricultural yields, modifications of trade routes, glacier retreat, mass species extinctions and increases in the ranges of disease vectors.

Remaining scientific uncertainties include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions, but there is ongoing political and public debate worldwide regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences.
Top of Page

Causes
The Earth's climate changes in response to external forcing, including variations in its orbit around the Sun (orbital forcing), changes in solar luminosity, volcanic eruptions,[18] and atmospheric greenhouse gas concentrations. The detailed causes of the recent warming remain an active field of research, but the scientific consensus is that the increase in atmospheric greenhouse gases due to human activity caused most of the warming observed since the start of the industrial era. This attribution is clearest for the most recent 50 years, for which the most detailed data are available. Some other hypotheses departing from the consensus view have been suggested to explain most of the temperature increase. One such hypothesis proposes that warming may be the result of variations in solar activity.

None of the effects of forcing are instantaneous. The thermal inertia of the Earth's oceans and slow responses of other indirect effects mean that the Earth's current climate is not in equilibrium with the forcing imposed. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0.5 °C (0.9 °F) would still occur.
Top of Page

Contents and text on this page is available under the terms of the GNU Free Documentation License.