global warming

Global warming is the rise in the average temperature of Earth's atmosphere and oceans since the late 19th century and its projected continuation.  Since the early 20th century, Earth's mean surface temperature has increased by about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980.  Warming of the climate system is unequivocal, and scientists are more than 90% certain that it is primarily used by increasing concentration of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation.  These findings are recognized by the national science academies of all major industrialized nations.

Climate model projections were summarized in the 2007 Fourth Amendment Report (AR4) by the Intergovernmental Panel of Climate Change (IPCC).  They indicated that during the 21st century, the goal surface temperature is likely to rise a further 1.1 to 2.9 °C (2 to 5.2 °F) for their lowest emissions scenario and 2.4 to 6.4 °C (4.3 to 11.5 °F) for their highest.  The ranges of these estimates arise from the use of models with differing sensitivity to greenhouse gas concentrations.

According to AR4, warming and related changes will vary from region to region around the globe.  The effects of an increase in global temperature include a rise in sea levels and a change in the amount and pattern of precipitation, as well a probable expansion of subtropical deserts.  Warming is expected to be strongest in the Arctic and would be associated with the continuing retreat of glaciers, permafrost, and sea ice.  Other likely effects of the warming include a more frequent occurrence of extreme-weather events including heat waves, droughts and heavy rainfall, ocean acidification and species extinctions due to shifting temperature regimes.  Effects significant to humans include the threat to food security from decreasing crop yields and loss of habitat from inundation.

Proposed policy responses to global warming include mitigation by emissions reduction, adaptation to its effects, and possible future geoengineering.  Most countries are parties to the United Nations Framework Convention on Climate Change (UNFCCC), whose ultimate objective is to prevent dangerous antropogenic (i.e., human-induced) climate change.  Parties to the UNFCCC have agreed that deep cuts in emissions are required, and that future global warming should be limited to below 2.0 °C (3.6 °F) relative to the pre-industrial level.  Reports published in 2011 by the United Nations Environment Programme and the International Energy Agency suggest that efforts as of the early 21st century to reduce emissions may be inadequate to meet UNFCCC's 2 °C target.

Greenhouse gas
A greenhouse gas (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range.  This process is the fundamental cause of the greenhouse effect.  The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.  In the solar system, the atmospheres of Venus, Mars, and Titan also contain gases that cause greenhouse effects.  Greenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would average about 33 °C (59 °F) colder than the present average of 14 °C (57 °F).

However, since the beginning of the Industrial Revolution, the burning of fossil fuels has contributed to the increase in carbon dioxide in the atmosphere from 280ppm to 397ppm, despite the uptake of a large portion of the emissions through various natural "sinks" involved in the carbon cycle.  Anthropogenic carbon dioxide (CO₂) emissions (i.e., emissions produced by human activities) come from combustion of carbon based fuels, principally wood, coal, oil, and natural gas.

Fossil fuels
Fossil fuels are oil, coal, and natural gas that originate from decayed plants and animals found in the Earth's crust.  Because they take millions of years to form and are being used at such a rapid rate, fossil fuels are essentially a non-renewable source of energy.  Even so, in 2005, more than three-quarters of the world's energy consumption was through the use of fossil fuels.  They work to generate steam, electricity and power transportation systems.  They make the manufacturing of tens of thousands of commercial goods possible.  And although fossil fuels have become synonymous with modern industrial society, their potential to solve some of the challenges of everyday existence has been understood throughout history.

Use of fossil fuels produces around 21.3 billion metric tons of carbon dioxide per year.  Carbon dioxide is, of course, one of the notorious greenhouse gases - the stuff directly responsible for global warming.

There are many potential alternatives to the use of fossil fuels (some of them can be rather fruity).  These include biofuel, ethanol, and vegetable oil.  Most scientists believe it's time for humans to address their addiction to fuels derived from decayed plants and animals and help fossil fuels go the way of the dinosaur.

Sources:

http://en.wikipedia.org/wiki/Global_warming
http://en.wikipedia.org/wiki/Greenhouse_gas
http://tlc.howstuffworks.com/family/fossil-fuel.htm
http://www.instituteforenergyresearch.org/energy-overview/fossil-fuels/