Global warming is the temperature of Earth’s surface, oceans and atmosphere going up over tens to thousands of years. Average temperatures today are about 1 °C (1.8 °F) higher than before people started burning a lot of coal around 1750. But in some parts of the world it is less than this and some more. Most scientists say that by the year 2100 temperatures will be 2 °C (3.6 °F) to 4 °C (7.2 °F) higher than they were before 1750. The changes people can see most easily because of this increase in temperature is the melting of ice caps all around the world. Sea level is rising for two reasons. One reason is because of ice on the land, like Greenland, melting into the sea. The other reason is because of water getting bigger when it gets warmer. Many cities will be partly flooded by the ocean in the 21st century.
Global average temperature, shown by measurements from various sources, has increased since the Industrial Revolution.
Places that were warmer (Red) and cooler (Blue) over the past 50 years
File:Global warming explained in 3 minutes.webmPlay media
A simple video explanation of global warming
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In the Northern Hemisphere, unusually hot summers have become more common (relative to 1951–1980 mean), according to Hansen et al. (2012) as a consequence of global warming.
Global warming is mostly because of people burning things, like gasoline to make cars go and natural gas to keep houses warm. But the heat from the burning itself only makes the world a tiny bit warmer: it is the carbon dioxide from the burning which is the biggest part of the problem. Among the greenhouse gases, the increase of carbon dioxide in the atmosphere is the main cause of global warming, as predicted by Svante Arrhenius a hundred years ago, confirming the work of Joseph Fourier more than 200 years ago. When people burn fossil fuels like coal, oil and natural gas this adds carbon dioxide into the air. This is because fossil fuels contain lots of carbon and burning means joining most of the atoms in the fuel with oxygen. When people cut down many trees (deforestation), this means less carbon dioxide is taken out of the atmosphere by those plants.
As the Earth’s surface temperature becomes hotter the sea level becomes higher. This is partly because water over 4 °C (7.2 °F) expands when it gets warmer. It is also partly because warm temperatures make glaciers and ice caps melt. The sea level rise causes coastal areas to flood. Weather patterns, including where and how much rain or snow there is, are changing. 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 the Intergovernmental Panel on Climate Change (IPCC) are talking about global warming. But governments, companies, and other people do not agree on what to do about it. Some things that could reduce warming are to burn less fossil fuels, grow more trees, eat less meat, and put some carbon dioxide back in the ground. Shading the Earth from some sunlight (this is called geoengineering) could also reduce warming but we don’t understand how it might change weather in other ways. Also people could adapt to any temperature changes. The Kyoto Protocol and Paris Agreement try to reduce pollution from the burning of fossil fuels. Most governments have agreed to them but some people in government think nothing should change. The gas produced by cows digestion also causes global warming, because it contains a greenhouse gas called methane. Global warming means that Antarctica and Greenland ice sheets are melting and the oceans are expanding. Recent climate change would still cause a 6 meters (20 ft) sea-level rise even if greenhouse gas emissions were reduced in 2015 per a scientific paper in Science.
Low-lying areas such as Bangladesh, Florida, the Netherlands and other areas face massive flooding.
Cities affected by current sea level rise Edit
Places that would be flooded by a 6 meters (20 ft) sea level rise
Many cities are sea ports and under threat of flooding if the present sea level rises.
These and the other cities have either started trying to deal with rising sea level and related storm surge, or are discussing this, according to reliable sources.
New York City
Norfolk, Virginia, in Hampton Roads area of United States
Crisfield, Maryland, United States
Charleston, South Carolina
Miami, Florida, has been listed as “the number-one most vulnerable city worldwide” in terms of potential damage to property from storm-related flooding and sea-level rise.
Thatta and Badin, in Sindh, Pakistan
Mumbai, Buenos Aires, Los Angeles, Rio de Jan