Global warming

Global mean surface temperature change from 1880 to 2019

File:Global warming explained in 3 minutes.webm

Places that were warmer (Red) and cooler (Blue) in 2015 than in previous average

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 a steady rise in Earth's surface temperature. Temperatures today are about 1 °C (1.8 °F) higher than 150 years ago. Many scientists say that in the next 100–200 years, temperatures might be up to 6 °C (11 °F) higher than they were before the effects of global warming were discovered. Most noticeable changes by this increase in temperature is the melting of ice caps all around the world. Sea level is rising steadily because of continental ice melting into the sea. As a prediction, many cities are soon to be partially submerged in the ocean. Consequently, many part of the world have a major increase in temperature.

Among the Greenhouse gases, the concentration and increase of carbon dioxide in the atmosphere appears to be 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 use fossil fuels like coal and oil, this adds carbon dioxide in the air. 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 expands when it gets warmer. It is also partly because warm temperatures make glaciers melt. The sea level rise causes 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. The gas produced by cows digestion also causes global warming, because it contains a greenhouse gas called methane.

Temperature changes

A graph of temperatures over the past two thousand years from different 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 1 °C (1.8 ± 0.4 °F). 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 article: Greenhouse effect

Fossil fuel related CO₂ emissions compared to five IPCC scenarios. The dips are related to global 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 article: 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 when they burn coal or oil. Some of this dirt falls out within a few hours. Some is aerosol, so small that it could stay in the air for years. The aerosol particles that humans put in the atmosphere make the earth colder. The effect of dust therefore cancels out some of the effects of greenhouse gases.

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, carbon dioxide levels have continued to rise.

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. For example, a process using nanotechnology has been found to remove carbon dioxide from the air to create ethanol.

The term global warming

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. The term "global warming" was created by Wallace Smith Broecker. 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

Places the 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.

• London
• New York City
• Norfolk, Virginia, in Hampton Roads area of United States
• Southampton
• 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.
• Saint Petersburg
• Sydney, Australia
• Jakarta
• Thatta and Badin, in Sindh, Pakistan
• Malé, Maldives
• Beijing, Mumbai, Buenos Aires, Los Angeles, Mexico City, Moscow, New Delhi, Rio de Janeiro

OECD 2007 REPORT

From a 2007 OECD report

1. Miami, USA
2. Guangzhou, P.R. of China
3. New York-Newark, USA
4. Kolkata, India
5. Shanghai, P.R. of China
6. Mumbai, India
7. Tianjin, P.R. of China
8. Tokyo, Japan
9. Hong Kong, P.R. of China
10. Bangkok, Thailand
11. Ningbo, P.R. of China
12. New Orleans, USA
13. Osaka-Kobe, Japan
14. Amsterdam, The Netherlands
15. Rotterdam, The Netherlands
16. Ho Chi Minh City, Vietnam
17. Nagoya, Japan
18. Qingdao, China
19. Virginia Beach, USA
20. Alexandria, Egypt

Another seven cities that are exposed to coastal flooding:

• Rangoon, Myanmar
• Hai Phòng, Vietnam
• Khulna, Bangladesh
• Lagos, Nigeria
• Abidjan, Côte d'Ivoire
• Chittagong, Bangladesh
• Jakarta, Indonesia

Further reading

• Why you should sweat climate change March 1, 2013 USA Today
• Report Blames Climate Change for Extremes in Australia March 4, 2013 The New York Times
• It's Global Warming, Stupid November 1, 2012 BusinessWeek
• Extremely Bad Weather: Studies start linking climate change to current events November 17, 2012; Vol.182 #10 Science News
• Global Temperatures Highest in 4,000 Years March 7, 2013 The New York Times
• IPCC. 2007 Climate change 2007. the physical science basis. (summary for policy makers) IPCC.
• Jones C. Climate change: facts and impacts [online]. Available from: What effects are we seeing now and what is still to come?
• Miller C. and Edwards P.N. (eds) 2001. Changing the Atmosphere: Expert Knowledge and Environmental Governance, MIT Press.
• Ruddiman W.F. 2003. The anthropogenic greenhouse era began thousands of years ago, Climate Change 61 (3): 261-293.
• Ruddiman W.F. 2005. Plows, Plagues and Petroleum: how humans took control of climate. Princeton University Press.

Related pages

• Climate change
• James Hansen
• Stern Review
• Storms of My Grandchildren
• Intergovernmental Panel on Climate Change
• 350.org

Other websites

• The Climate Change Guide easy-to-understand information on Climate Change
• [en.citizendium.org/wiki/Global_warming Glass bal warming] -Citizendium

Public administrations and organizations

• US EPA climate change and global warming website
• The UN Climate Change Secretariat
• United Nations Environmental Program (UNEP): Climate Change Page
• Introduction to climate change: Lecture notes for meteorologists
• European Union page about Climate Change.

Other links

• Congressional Research Service (CRS) Reports regarding Climate change
• The Pew Center on Global Climate Change
• Climate Change - An Information Statement of the American Meteorological Society, updated Feb. 2007.
• Summary of the Impacts of Climate Change from The Nature Conservancy
• Climate change and global warming - World Wide Fund for Nature.
• Global Change - globalchange.org
• Impacts of a Warming Arctic: Arctic Climate Impact Assessment (2004) by the Arctic Climate Impact Assessment
• How To Help Prevent Global Warming Articles And Newsletter
• UN scientist backs '350' target for CO2 reduction
• Climate change dates back to dawn of first farmers March 3, 2013 USA Today

BBC articles

• Oct 2018: What is Global Warming?
• Ongoing: BBC Climate Change Experiment