Climate change is any substantial change in Earth’s climate that lasts for an extended period of time. Global warming refers to
climate change that causes an increase in the average temperature of the lower atmosphere. Global warming can have many different
causes, but it is most commonly associated with human interference, specifically the release of excessive amounts of greenhouse gases.
Greenhouse gases, such as carbon dioxide (CO
), methane (CH
), water vapor, and fluorinated gases, act like a greenhouse around the
earth. This means that they let the heat from the Sun into the atmosphere, but do not allow the heat to escape back into space. The more
greenhouse gases there are, the larger the percentage of heat that is trapped inside the earth’s atmosphere. The earth could not exist in its
present state (that is, with life) without the presence of some naturally occurring greenhouse gases, such as CO
, and water vapor.
Without any greenhouse gases no heat would be trapped in atmosphere, so the earth would be extremely cold. (NASA, 2002)
Naturally occurring greenhouse gases (not fluorinated gases) are good in naturally occurring amounts;
it’s when people start contributing excessive amounts of them that greenhouse gases become a
problem. With excessive greenhouse gas buildup, the earth’s atmosphere warms to unnatural
temperatures which causes, among other things, sea level to rise. Global warming also causes sea
surface temperatures to rise, precipitation patterns to change, etc.
The rate of warming is increasing. The 20th century's last two decades were the hottest in 400
years and possibly the warmest for several millennia, according to a number of climate studies.
And the United Nations' Intergovernmental Panel on Climate Change (IPCC) reports that 11 of
the past 12 years are among the dozen warmest since 1850.
• The Arctic is feeling the effects the most. Average temperatures in Alaska, western Canada, and
eastern Russia have risen at twice the global average, according to the multinational Arctic
Climate Impact Assessment report compiled between 2000 and 2004.
• Arctic ice is rapidly disappearing, and the region may have its first completely
ice-free summer by
Polar bears and indigenous cultures
are already suffering from the sea-ice loss.
• Glaciers and mountain snows are rapidly melting—for example,