Background on Global Warming


Here's the scoop on why it's happening, what's causing it and how it's changing our planet.

Is it happening?


The earth is already showing signs of worldwide climate change.
  • Average temperatures around the world have climbed 1.4°F in the last 100 years. The 1980's and 1990's were the hottest decades on record, and the eight warmest years have all occurred since 1998.
  • Arctic sea ice is rapidly disappearing. Glaciers have been melting at a faster rate than any time over the last 5,000 years. In the Arctic and the Antarctic, ice shelves several thousand years old have started to collapse due to warming.
  • Coral reefs are highly sensitive to small changes in water temperature, and in 1998 they suffered the worst die-off ever recorded. Experts predict die-offs will increase in frequency and intensity as sea temperatures rise.
  • Warmer temperatures have allowed mosquitoes to thrive, spreading mosquito-borne diseases like malaria to higher altitudes.
  • Global warming doesn't cause hurricanes, but it does make them stronger and more dangerous. Scientists have found that the destructive potential of hurricanes has greatly increased over the past 35 years.

Are humans causing it?

"Very likely," said the UN Intergovernmental Panel on Climate Change (IPCC) in a February 2007 report based on the work of 2,500 scientists in more than 130 countries.

  • Industrialization, deforestation, and pollution have greatly increased the concentrations of carbon dioxide, methane and nitrous oxide in the atmosphere. These are all greenhouse gases that trap heat near the Earth's surface.
  • The increase in carbon dioxide is caused primarily by the burning of fossil fuels and changes in land use, while the increases of methane and nitrous oxide are caused primarily by agriculture.

What can we expect?

A follow-up report by the IPCC released in April 2007 warned that global warming could lead to large-scale food and water shortages and have catastrophic effects on wildlife.

  • Scientists project that the average global temperature will increase 3.2-7.2°F by 2100.
  • Warming temperatures mean the Arctic could be free of summer ice by 2050, causing sea levels to rise and creating water shortages in regions that depend on ocean runoff for fresh water.
  • Rising sea levels could wash out highly populated coastal areas. In the United States, Louisiana and Florida are especially at risk, while New York is in danger of severe flooding. Scientists predict sea levels could rise between 7 and 23 inches by 2100.
  • Warmer ocean temperatures also mean tropical storms will grow more intense with stronger winds and heavier participation.
  • 1.6 million species face extinction from disappearing habitats, changing ecosystems and acidifying oceans.
  • Deaths from global warming are expected to double in just 25 years, to 300,000 people a year.


Intergovernmental Planel on Climate Change National Geographic
Environmental Defense Fund
Stop Global Warming World Health Organization