Climate Change

“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.”
(Source: Synthesis Report of the IPCC Fourth Assessment Report, 2007)
The basic breakdown of climate change is simple and it begins with the greenhouse effect. The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapor, carbon dioxide, nitrous oxide, and methane, for example) trap energy from the sun. These greenhouse gases in the atmosphere behave much like the glass panes in a greenhouse. Sunlight enters the Earth’s atmosphere passing through the blanket of greenhouse gases. As it reaches the Earth’s surface, land, water, and biosphere absorb the sunlight’s energy. Once absorbed, this energy is sent back into the atmosphere. Some of the energy passes back into space, but much of it remains trapped in the atmosphere by the layer of greenhouse gases, causing our world to heat up.

The greenhouse effect is important. Without it the Earth would be about 60 degrees Fahrenheit cooler which is too cold for humans to live. When the layer of greenhouse gases becomes too thick making the greenhouse effect too strong, too much of the suns energy is trapped by the atmosphere causing the Earth’s temperature to warm more than usual.

According to the European Environment Agency, the main sources of man-made greenhouse gases are:
• burning of fossil fuels in electricity generation, transport, industry and households;
• agriculture and land use changes like deforestation;
• land filling of waste; and
• use of industrial fluorinated gases

The Intergovernmental Panel on Climate Change (IPCC) is an organization set up by the UNEP (United Nations Environmental Programme) and the World Meteorological Organization (WMO). It brings together thousands of scientists from all over the world.
In November 2007 the IPCC released its Fourth Assessment Report, comprising four sections: The Physical Science Basis, by Working Group I; Impacts, Adaptation and Vulnerability, by Working Group II; Mitigation of Climate Change, by Working Group III; and an overall Synthesis Report. It took six years to complete the report, which runs to several thousand pages. For this and its other work over the last 20 years, the IPCC was the joint winner of the 2007 Nobel Peace Prize.

The main idea of the report is that over the past 150 years, mean temperature has increased by almost 0.8 ºC globally and by about 1 ºC in Europe. Eleven of the last twelve years (1995–2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850). Without global action to limit emissions, the IPCC expects that global temperatures may increase further by 1.8 to 4.0 ºC by 2100. This means that temperature increase since pre-industrial times would exceed 2 °C. Beyond this threshold irreversible and possibly catastrophic changes become far more likely.

IPCC Fourth Assessment Report highlights:
• Around 20-30 per cent of the plant and animal species assessed are likely to be at increased risk of extinction if global average temperatures exceed 1.5 degrees C to 2.5 degrees C over late 20th century levels.
• There is a likelihood of "irreversible" impacts. For example if temperature increases exceed about 3.5 degrees C, between 40 per cent and 70 per cent of the species assessed might be at increased risk of extinction.
• Increases in sea surface temperatures of about one to three degrees C are projected to result in more "frequent coral bleaching events and widespread mortality".
• There is growing concern over the oceans and seas becoming more acidic as they absorb rising levels of CO2 and the impacts on "marine shell-forming organisms" like coral reefs.
• There is a higher confidence in the risks of extreme weather events and the projected increases in droughts, heatwaves and floods as well as their adverse impacts.
• Concern is growing that the poor and elderly in low-latitude and less-developed areas (including those in dry areas and living on mega-deltas) are likely to suffer most.
• There is high confidence that by mid-century "many semi-arid areas, for example the Mediterranean basin, western United States, southern Africa and northeast Brazil, will suffer a decrease in water resources due to climate change".
• New observations linked with the Greenland and possibly Antarctic ice sheets may mean that the rate of ice loss will increase above previous forecasts.
• There is growing concern that any benefits linked with climate change will be gone after more modest temperature rises.
Citations:
United Nation Environment Programme, http://www.unep.org/; The IPCC Assessment Reports, http://www.ipcc.ch/; European Environmental Agency, http://www.eea.europa.eu/themes; United Status Environmental Protection Agency, http://www.epa.gov/climatechange