Discover the scientific facts on global warming

Many observations indicate that global warming has taken place during the 20th century. Global warming has resulted in a increase of the average surface temperature, a decrease in snow cover and ice extent and a rise of the sea level. Moreover, global warming affects precipitation, cloud cover and extreme temperatures. More...

• What causes this global warming?
  
  
• What global warming are expected for the future?
  
  
• read the GreenFacts Digest on the global warming

Variation of the Earth's surface temperature
for the past 140 years

What causes this global warming?

global warming has and will always vary for natural reasons. However, human activities are increasing significantly the concentrations of some gases in the atmosphere, such as greenhouse gases (mainly CO2), which tend to warm the earth surface, and anthropogenic aerosols, which mostly tend to cool it.

Although more research is needed, understanding of global warming processes and computer models have improved, leading the IPCC to draw the following conclusion:

Most of the global warming over the last 50 years is likely to have been due to man-made activities. More...

What global warmings are expected for the future?

To predict the future global warming, several greenhouse gas emission scenarios were developed and fed into computer models.

They project for the next century that, without specific policy changes:

• global mean temperature should increase by between 1.4 and 5.8°C (2.5 to 10°F).
• the Northern Hemisphere cover should decrease further, but the Antarctic ice sheet should increase.
• the sea level should rise by between 9 and 88 cm (3.5" to 35").
• other changes should occur, including an increase in some extreme weather events.
  

After 2100, human induced global warming is projected to persist for many centuries.
The sea level should continue rising for thousands of years after the climate has been stabilized. More...