GLOBAL WARMING :- MEANING | DEFFINATION | IMAGES | ISSUES AND MORE

Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) between the start and the end of the 20th century. The Intergovernmental Panel on Climate Change (IPCC) concludes that most of the observed temperature increase since the middle of the 20th century was very likely caused by increasing concentrations of greenhouse gases resulting from human activity such as fossil fuel burning and deforestation. The IPCC also concludes that variations in natural phenomena such as solar radiation and volcanic eruptions had a small cooling effect after 1950. These basic conclusions have been endorsed by more than 40 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries.[

Climate model projections summarized in the latest IPCC report indicate that the global surface temperature is likely to rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century.The uncertainty in this estimate arises from the use of models with differing sensitivity to greenhouse gas concentrations and the use of differing estimates of future greenhouse gas emissions. Most studies focus on the period leading up to the year 2100. However, warming is expected to continue beyond 2100 even if emissions stop, because of the large heat capacity of the oceans and the long lifetime of carbon dioxide in the atmosphere.

An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects include changes in the frequency and intensity of extreme weather events, species extinctions, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional variations is uncertain.
Political and public debate continues regarding global warming, its causes and what actions to take in response. The available options are mitigation to reduce further emissions; adaptation to reduce the damage caused by warming; and, more speculatively, geoengineering to reverse global warming. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions.

Temperature changes

The most common measure of global warming is the trend in globally averaged temperature near the Earth's surface. Expressed as a linear trend, this 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). The urban heat island effect is estimated to account for about 0.002 °C of warming per decade since 1900.[10]  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. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with regionally varying fluctuations such as the Medieval Warm Period and the Little Ice Age.[11]

Estimates by NASA's Goddard Institute for Space Studies and the National Climatic Data Center show that 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree.[12][13] Estimates prepared by the World Meteorological Organization and the Climatic Research Unit show 2005 as the second warmest year, behind 1998.[14][15] Temperatures in 1998 were unusually warm because the strongest El Niño in the past century occurred during that year.[16] Global temperature is subject to short-term fluctuations that overlay long term trends and can temporarily mask them. The relative stability in temperature from 2002 to 2009 is consistent with such an episode

 

Definitions of global warming 

What is global warming? 

Global warming is when the earth heats up (the temperature rises).  It happens when greenhouse gases (carbon dioxide, water vapor, nitrous oxide, and methane) trap heat and light from the sun in the earth’s atmosphere, which increases the temperature.  This hurts many people, animals, and plants.  Many cannot take the change, so they die.

What is the greenhouse effect?

The greenhouse effect is when the temperature rises because the sun’s heat and light is trapped in the earth’s atmosphere.  This is like when heat is trapped in a car. On a very hot day, the car gets hotter when it is out in the parking lot.  This is because the heat and light from the sun can get into the car, by going through the windows, but it can’t get back out.  This is what the greenhouse effect does to the earth.  The heat and light can get through the atmosphere, but it can’t get out.  As a result, the temperature rises.

The sun’s heat can get into the car through the windows but is then trapped.  This makes what ever the place might be, a greenhouse, a car, a building, or the earth’s atmosphere, hotter.  This diagram shows the heat coming into a car as visible light (light you can see) and infrared light (heat).  Once the light is inside the car, it is trapped and the heat builds up, just like it does in the earth’s atmosphere.

Sometimes the temperature can change in a way that helps us.  The greenhouse effect makes the earth appropriate for people to live on.  Without it, the earth would be freezing, or on the other hand it would be burning hot.  It would be freezing at night because the sun would be down.  We would not get the sun’s heat and light to make the night somewhat warm.  During the day, especially during the summer, it would be burning because the sun would be up with no atmosphere to filter it, so people, plants, and animals would be exposed to all the light and heat.

Although the greenhouse effect makes the earth able to have people living on it, if there gets to be too many gases, the earth can get unusually warmer, and many plants, animals, and people will die.  They would die because there would be less food (plants like corn, wheat, and other vegetables and fruits).  This would happen because the plants would not be able to take the heat.  This would cause us to have less food to eat, but it would also limit the food that animals have.  With less food, like grass, for the animals that we need to survive (like cows) we would even have less food.  Gradually, people, plants, and animals would all die of hunger.