Global warming is a slow rise in Earth's surface temperature caused by increased levels of carbon dioxide and other greenhouse gases from human activities like burning fossil fuels. Temperatures have increased about 0.74°C in the last 150 years and are projected to rise up to 6°C in the next century. Higher temperatures cause sea level rise from water expansion and melting ice sheets and glaciers, threatening many coastal cities. While some effects of global warming are uncertain, consequences may include stronger storms, shifting climate patterns, and damage to agriculture and natural environments. Responses have included international agreements like the Kyoto Protocol to reduce greenhouse gas emissions and efforts to adapt to or mitigate climate change impacts.

1. Global warming
From Wikipedia, the free encyclopedia
Global mean surface temperatures 1856-2004
Global warming is a slow steady rise in Earth's surface temperature.[1] Temperatures today are
0.74 °C (1.33 °F) higher than 150 years ago.[2] Many scientists say that in the next 100–200
years, temperatures might be up to 6 degrees Celsius higher than they were before the effects of
global warming were discovered.
The basic cause seems to be a rise in atmospheric carbon dioxide, as predicted by Svante
Arrhenius a hundred years ago. When people use fossil fuels like coal and oil, this adds carbon
dioxide to the air. When people cut down the Earth's forests (deforestation), this means less
carbon dioxide is taken out of the atmosphere by plants.
If the Earth's temperature becomes hotter the sea level will also become higher. This is partly
because water expands when it gets warmer. It is also partly because warm temperatures make
glaciers melt. The sea level rise may cause coastal areas to flood. Weather patterns, including
where and how much rain or snow there is, will change. Deserts will probably increase in size.
Colder areas will warm up faster than warm areas. Strong storms may become more likely and
farming may not make as much food. These effects will not be the same everywhere. The
changes from one area to another are not well known.
People in government and Intergovernmental Panel on Climate Change (IPCC) have talked about
global warming. They do not agree on what to do about it. Some things that could reduce
warming are to burn less fossil fuels, adapt to any temperature changes, or try to change the
Earth to reduce warming. The Kyoto Protocol tries to reduce pollution from the burning of fossil
fuels. Most governments have agreed to it. Some people in government think nothing should
change.
Temperature changes
See also:Temperaturerecord of the past1000 years

2. A graph of temperaturesoverthe pasttwothousandyearsfromdifferent proxy reconstructions.
Climate change has happened many times over the history of the Earth, including the coming and
going of ice ages. For more recent centuries, we have more details.
Since the 1800s, people have recorded the daily temperature. By about 1850, there were enough
places measuring temperature so that scientists could know the global average temperature. From
1920 to 1940, the temperature got warmer. From 1940 to 1970, the temperature got slightly
cooler. From 1970 to today, the average temperature for the world has increased by about 0.6 ±
0.2 °C.[3] Starting in 1979, satellites started measuring the temperature of the Earth.
Before 1850, there were not enough temperature measurements for us to know how warm or cold
it was. Climatologists use proxy measurements to try to figure out past temperatures before there
were thermometers. This means measuring things that change when it gets colder or warmer.
One way is to cut into a tree and measure how far apart the growth rings are. Trees that live a
long time can give us an idea of how temperature and rain changed while it was alive.
For most of the past 2000 years the temperature didn't change much. There were some times
where the temperatures were a little warmer or cooler. One of the most famous warm times was
the Medieval Warm Period and one of the most famous cool times was the Little Ice Age. Other
proxy measurements like the temperature measured in deep holes mostly agree with the tree
rings. Tree rings and bore holes can only help scientists work out the temperature until about
1000 years ago. Ice cores are also used to find out the temperature back to about half a million
years ago.
The greenhouse effect
Main page:Greenhouse effect

3. Fossil fuel relatedCO2 emissionscomparedtofive IPCCscenarios.The dipsare relatedtoglobal
recessions.
Coal-burning power plants, car exhausts, factory smokestacks, and other man-made waste gas
vents give off about 23 billion tons of carbon dioxide and other greenhouse gases into the Earth's
atmosphere each year. The amount of CO2 in the air is about 31% more than it was around 1750.
About three-quarters of the CO2 that people have put in the air during the past 20 years are due to
burning fossil fuel like coal or oil. The rest mostly comes from changes in how land is used, like
cutting down trees.
The Sun
Main page:Sun
The sun gets a little bit hotter and colder every 11 years. This is called the 11-year sunspot cycle.
The change is so small that scientists can barely measure how it affects the temperature of the
Earth. If the sun was causing the Earth to warm up, it would warm both the surface and high up
in the air. But the air in the upper stratosphere is actually getting colder, so scientists don't think
changes in the sun have much effect.
Dust and dirt
Dust and dirt in the air come from natural sources such as volcanos, erosion and meteoric dust.
People also add to it. Some of this dirt falls out within a few hours. Some is aerosol, so small that
it could stay in the air for years.
Some responses
Some people try to stop global warming, usually by burning less fossil fuel. Many people have
tried to get countries to emit less greenhouse gases. The Kyoto Protocol was signed in 1997. It
was meant to reduce the amount of greenhouse gases in the atmosphere to below their levels in
1990. However, this has not happened. Carbon dioxide levels today are the highest they have
been since the start of the Industrial Revolution.
Energy conservation is used to burn less fossil fuel. People can also use energy sources that don't
burn fuel, or can prevent the carbon dioxide from getting out.
People can also change how they live because of any changes that global warming will bring.
For example, they can go to places where the weather is better, or build walls around cities to
keep flood water out. Like the preventive measures, these things cost money, and rich people and
rich countries will be able to change more easily than the poor. Geoengineering is also seen by
some as one climate change mitigation response.

4. Etymology
The term global warming was first used in its modern sense on 8 August 1975 in a science paper
by Wally Broecker in the journal Science called "Are we on the brink of a pronounced global
warming?". Broecker's choice of words was new and represented a significant recognition that
the climate was warming; previously the phrasing used by scientists was "inadvertent climate
modification," because while it was recognized humans could change the climate, no one was
sure which direction it was going. The National Academy of Sciences first used global warming
in a 1979 paper called the Charney Report, it said: "if carbon dioxide continues to increase, we
find no reason to doubt that climate changes will result and no reason to believe that these
changes will be negligible." The report made a distinction between referring to surface
temperature changes as global warming, while referring to other changes caused by increased
CO2 as climate change.
Global warming became more widely popular after 1988 when NASA climate scientist James
Hansen used the term in a testimony to Congress. He said: "global warming has reached a level
such that we can ascribe with a high degree of confidence a cause and effect relationship
between the greenhouse effect and the observed warming." His testimony was widely reported
and afterward global warming was commonly used by the press and in public discourse.
Effects of global warming on sea levels
Global warming means that Antarctica and Greenland ice sheets are melting and the oceans are
expanding. Sea level rises might be more than a metre by 2100. Low-lying areas such as
Bangladesh, Florida and the Netherlands face massive flooding.[7]
Citiesaffectedby currentsea level rise
Placesthe wouldbe floodedbya6 metersealevel rise
Many cities under threat of flooding if the present sea level rises.
These and other cities have either started trying to deal with rising sea level and related storm
surge, or are discussing this, according to reliable sources.
 London [8]
 NewYork City [9][10][11][12][13][14]
 Norfolk,Virginia,inHamptonRoads areaof UnitedStates [15][16]
 Southampton [17]
 Crisfield,Maryland, UnitedStates[18]

5.  Charleston,SouthCarolina[19]
 Miami,Florida,hasbeenlistedas"the number-one mostvulnerable cityworldwide"intermsof
potential damage topropertyfromstorm-relatedfloodingandsea-level rise.[20][21]
 SaintPetersburg[22]
 Sydney,Australia[23]
 Jakarta [24]
 Thatta and Badin,inSindh,Pakistan [25]
 Malé, Maldives
 Beijing,Mumbai,BuenosAires,LosAngeles,MexicoCity,Moscow,New Delhi,Riode Janeiro [26]