Global warming is the result from an overall, continuiys increase in the retention of the sun’s heat around Earth due to trapped greenhouse gases, especially carbon dioxide, nitrous oxide and methane. Emissions of harmful greenhouse gases mainly due to accelerating fossil fuel burning that began in the Industrial Revolution.
Global warming involves an unprecedented increase of the rate of change in natural processes, which now converges with the rate of change in human societies, leading to a crisis of environmental adaptation. Most authoritative scientific bodies predict that on present trends that the world needs to cut emissions by 50 percent by mid twenty-first century.
 Rising Temperature
Earth's average surface temperature, rose by 0.74 ± 0.18 °C over the period 1906–2005. The rate of warming over the last half of that period was almost double that for the period as a whole (0.13 ± 0.03 °C per decade, versus 0.07 °C ± 0.02 °C per decade). Urban heat island effect accounted about 0.002 °C of warming per decade since 1900. Temperatures in the lower troposphere have increased between 0.13 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements.
 Greenhouse Effect
- Main Article: 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. Without these gases, heat would escape back into space and Earth’s average temperature would be about 30ºC colder. Because of how they warm our world, these gases are referred to as greenhouse gases.
Strengthening of the greenhouse effect through human activities is known as the enhanced greenhouse effect and leads to global warming. Since the Industrial Revolution the amount of greenhouse gases in the atmosphere has increased dramatically, leading to increased radiative forcing from carbon dioxide, methane, tropospheric ozone, chlorofluorocarbon and nitrous oxide. Carbon dioxide and methane concentrations have increased by 36% and 148% respectively since 1750. Fossil fuel burning and deforestation has further increased production of carbon dioxide for over the past 20 years.
There are several greenhouse gases responsible for warming, and human activities emit them in a variety of ways, mostly from the combustion of fossil fuels in cars, factories and electricity production. The gas responsible for the most warming is carbon dioxide, other contributors include methane released from landfills and agriculture, nitrous oxide from fertilizers, gases used for refrigeration and industrial processes, and the loss of forests that would otherwise store carbon dioxide.
Different greenhouse gases have very different heat-trapping abilities. Methane produces more than 20 times the warming effect than carbon dioxide while nitrous oxide is 300 times more powerful than carbon dioxide. Other gases, such as chlorofluorocarbons (blamed for the depletion of the ozone layer), have heat-trapping potential thousands of times greater than carbon dioxide.
Changes have been observed in the trends of some extreme weather and climate events:
- increase in the areas affected by drought and desertification
- increased tropical cyclone activity and increase in number of intense storms
- incidence of extreme high sea level
 Retreat and disappearance of glaciers
At least one-sixth of the world's population are supplied by meltwater from major mountain ranges. Changes in glaciers and snow cover are expected to dramatically reduce water availability for these populations.
Some recorded glacial retreat:
- In the Wakhan Corridor of Afghanistan 28 of 30 glaciers examined retreated significantly during the 1976-2003 period and retreated at an average of 11 meters per year.
- 53% studied of 612 glaciers in China were retreating. After 1990, the retreat has becoming widespread as 95% of these glaciers were measured to be retreating.
- The Columbia Glacier near Valdez in Prince William Sound, Alaska has retreated 15 km in the last 25 years.
- Since 1912 the glacier cover on the summit of Kilimanjaro has apparently retreated 75%, and the volume of glacial ice is now 80% less than it was a century ago due to both retreat and thinning.
Ongoing effects of global warming to oceans include rising sea levels due to thermal expansion and melting of glaciers and polar ice sheets, and warming of the ocean surface.
- Rising sea levels - It has been determined that sea level rose at an average rate of around 1.8 mm per year over 1961 to 2003 and at an average rate of about 3.1 mm per year from 1993 to 2003, though it is still not confirmed if the rise in sea level is due to global warming.
- Acidification and oxygen depletion - As carbon dioxide dissolves in sea water, carbonic acid is formed, thus acidifying the ocean. Since 1750 human activities has led to an average decrease in pH of 0.1 units. In addition, the amount of oxygen dissolved in the oceans may decline, with adverse consequences for ocean life.
- Rising ocean temperature - The warming of the ocean and thermal expansion rates are more than 50 percent larger than previous estimates for the upper 300 meters level. From 1961, global ocean temperature has risen by 0.10°C from the surface to a depth of 700 meters.
 Agriculture and Food supply
Some arguments suggest that global warming will increase the amount of rainfall which will help grow plants and crops. Global warming makes weather more unpredictable, period of drought followed by storms will be very common. Plants and crops may not be able to cope on these conditions and will result to smaller yields, affecting the food supply.
Climate change due to global warming is estimated to be responsible for 3% of diarrhoea and malaria, 3.8% of dengue fever deaths worldwide in 2004 and it is projected that malnutrition would increase.
 Impact on Ecosystem
Ecosystems are home to many different species of plants and animals. Climate change threatens the long-term survival of all creatures on Earth, from polar bears to sea turtles to migratory birds and to humans. With sea levels predicted to rise up to 1 meter this century, climate change is predicted to destroy many beach nesting sites for sea turtles. Nearly a third of the beaches used by turtles would be lost with the sea level rise anticipated during this century, and many wading birds also face destruction of their coastal habitats in this region.
Climate change will not only affect marine habitats and species but also fisheries. Increasing ocean temperatures are causing coral bleaching - meaning that corals can no longer support the array of plants and animals that rely on them. Sea level rise is causing coral drowning as the water gets deeper and coral growth is inhibited and is also is also damaging to mangroves - a key costal habitat that protects the coastline and coastal communities from storms, reduces the impacts of floods and provides important habitats for juvenile fishes.
Mitigation of Global Warming refers to the actions and procedures taken by an individuals, corporations, government or an organization to reduce greenhouse gas emissions in order to minimize their effects on global climate change. Climate mitigation is any action taken to permanently eliminate or reduce the long-term risk and hazards of climate change to human life, property and the environment. This usually works in conjunction with national and international policies that minimize greenhouse gas production and release into the atmosphere. Instead of trying to adapt to global warming, mitigation of global warming refers more to the prevention and control of the products and actions that cause climate change.
Majority of the action taken to reduce the impact of global warming is due to the reduction of common energy sources in favor of using renewable and sustainable energy. Instead of using fossil fuels that produces harmful greenhouse gases, companies and nations can start creating policies that promote the use of wind or solar energy, thus reducing their impact on global warming. Improving vehicle fuel efficiency is one way to mitigate global warming as is the use of and promotion of energy resources such as nuclear power, hydrogen fuel cells, tidal power, and geothermal energy. Recycling and reusing resources also plays an important role in reducing the production of greenhouse gases.