Climate Change
What is climate change?
Climate change in IPCC usage refers to any change in climate over time, whether due
to natural variability or as a result of human activity.
Natural variability
Climate change is a normal part of the earth’s natural variability, which is related
to interactions among the atmosphere, ocean, and land, as well as changes in the
amount of solar radiation reaching the earth. The geologic record includes
significant evidence for large-scale climate changes in earth’s past.
Human-induced change
Certain naturally occurring gases, such as carbon dioxide (CO2) and water vapor
(H2O), trap heat in the atmosphere causing a greenhouse effect. Burning of fossil
fuels, like oil, coal, and natural gas is adding CO2 to the atmosphere. The current
level is the highest in the past 650,000 years. The Fourth Assessment Report of the
Intergovernmental Panel on Climate Change concludes, “that most of the observed
increase in the globally averaged temperature since the mid-20th century is very
likely due to the observed increase in anthropogenic greenhouse gas concentrations.”
Our climate is changing, largely due to the observed increases in human-produced
carbon pollution. The changes include increases in global average air and ocean
temperature, widespread melting of snow and ice, and rising global sea levels. The
extra heat in the climate system has other impacts, such as affecting atmospheric
and ocean circulation, which influences rainfall and wind patterns.
Another serious impact of increasing carbon pollution is ocean acidification. Around
a quarter of human-produced carbon dioxide is absorbed by the oceans. As the carbon
dioxide dissolves in seawater, it forms a weak carbonic acid, making the ocean more
acidic. There are early indications that some marine organisms are already being
affected by ocean acidification. Scientists agree that the worst effects of climate
change can largely be avoided if we can reduce pollution to an acceptable level.
Why carbon dioxide can bring about changes in the climate of the earth?
The heat content of the earth's surface is mainly from the sun. When sunlight shines
on the surface of the earth, the earth will heat up. After receiving the heat, the
earth will radiate the heat back to space. As a matter of fact, the amount of heat
received from the sun and the amount of heat the earth radiates out to space is more
or less the same in the long run. Nature is in equilibrium. The carbon dioxide in
the air can hinder the heat from radiating back to space. As such, carbon dioxide
acts like a blanket, hindering the earth from losing heat.
How do we know that our climate is changing?
Many signs around us caution us of a warming earth. Temperatures, precipitation,
birds, butterflies, fish, vegetation, glaciers, and sea levels can indicate changes
in the climate system. A few example clues to climate change occurring around the
world are discussed below:
Glacial retreat (melt)
Glaciers are large, slow-moving masses of ice, formed from compacted layers of snow.
They are considered among the most sensitive indicators of climate change. Himalayan
glaciers are receding faster today than the world average. Sixty-seven percent of
Himalayan glaciers are retreating at a startling rate, and a major factor has been
identified as climate change.
Sea level rise
Sea level has risen 6.7 inches (17.01 cm) in the last 100 years. In 2001, over 45
percent of tourist resorts in the Maldives reported beach erosion.
Timing of Bird Migration
Birds have long been used as an indicator of environmental change and are also good
indicators of the effect of climate change. In northern Europe, migratory birds such
as the swallow arrived earlier and departed later as a direct response to global
warming.
