Global warming

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.


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.

Greenhouse Gas Overview

Gases that trap heat in the atmosphere are often called greenhouse gases. This section of the EPA Climate Change Site provides information and data on emissions of greenhouse gases to Earth’s atmosphere, and also the removal of greenhouse gases from the atmosphere. For more information on the science of climate change, please visit EPA's climate change science home page.
Some greenhouse gases such as carbon dioxide occur naturally and are emitted to the atmosphere through natural processes and human activities. Other greenhouse gases (e.g., fluorinated gases) are created and emitted solely through human activities. The principal greenhouse gases that enter the atmosphere because of human activities are:

Carbon Dioxide (CO2): Carbon dioxide enters the atmosphere through the burning of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of other chemical reactions (e.g., manufacture of cement). Carbon dioxide is also removed from the atmosphere (or “sequestered”) when it is absorbed by plants as part of the biological carbon cycle.

Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.

Nitrous Oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.
Fluorinated Gases: Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes.

Fluorinated gases are sometimes used as substitutes for ozone-depleting substances (i.e., CFCs, HCFCs, and halons). These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases (“High GWP gases”).




The Consequences of Global Warming
On Weather Patterns

Ecosystem Shifts and Species Die-Off
Increasing global temperatures are expected to disrupt ecosystems, pushing to extinction those species that cannot adapt. The first comprehensive assessment of the extinction risk from global warming found that more than 1 million species could be obliterated by 2050 if the current trajectory continues.

Melting Glaciers, Early Ice Thaw
Rising global temperatures will speed the melting of glaciers and ice caps and cause early ice thaw on rivers and lakes.

More Powerful and Dangerous Hurricanes
Warmer water in the oceans pumps more energy into tropical storms, making them stronger and potentially more destructive.

Infectious Disease and Food and Waterborne Illness Outbreaks
Warming temperatures, alternating periods of drought and deluges, and ecosystem disruption have contributed to more widespread outbreaks of infections like malaria, dengue fever, tick-borne encephalitis, and diarrheal illnesses. People living in poverty will be hardest hit by the global surge in infectious diseases.

More Powerful and Dangerous Hurricanes
Warmer water in the oceans pumps more energy into tropical storms, making them stronger and potentially more destructive.

Bad Air, Allergy and Asthma
Global warming could increase smog pollution in some areas and intensify pollen allergies and asthma. Hotter conditions could also aggravate local air quality problems, already afflicting more than 100 million Americans.

Intense Rainstorms
Warmer temperatures increase the energy of the climatic system and can lead to heavier rainfall in some areas.


Drought and Wildfire
Warmer temperatures could increase the probability of drought. Greater evaporation, particularly during summer and fall, could exacerbate drought conditions and increase the risk of wildfires.


What You Can Do

You release greenhouse gases as a result of using energy to drive, using electricity to light and heat your home, and through other activities that support our quality of life like growing food, raising livestock and throwing away garbage. Greenhouse gas emissions can be reduced through simple measures like changing light bulbs and properly inflating your tires. This site provides over 25 easy steps you can take to not only reduce your greenhouse gas emissions, but also reduce air pollution, increase the nation's energy independence and save money.

What do you think about global warming and how can we protect our environment? What you can do?

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