What+is+Climate+Change

=**What is Climate Change?**=

==== **Climate** refers to the average weather experienced over a long period, typically 30 years. The Earth’s climate has changed many times in response to natural causes. The term **//climate change//** usually refers to changes that have occurred since the early 1900s. ====

====Natural and human factors both affect global climate. Natural causes include interactions between the ocean and the atmosphere, changes in the Earth's orbit and volcanic eruptions. Humans influence global climate by releasing greenhouse gases – like carbon dioxide and methane – into the atmosphere. These gases absorb energy that is radiated from the Earth’s surface, warming the atmosphere and increasing temperatures globally.====

====In 2007, the Intergovernmental Panel on Climate Change (IPCC), the world’s most authoritative body on climate change, concluded that //most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (man-made) greenhouse gas concentrations//.====