Global Warming....

 

Climate Change

"Global warming" redirects here. For other uses, see Climate change (disambiguation) and Global warming (disambiguation). This article is about contemporary climate change. For historical climate trends, see Climate variability and change.

In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to Earth's climate. The current rise in global average temperature is more rapid than previous changes, and is primarily caused by humans burning fossil fuels.^[2][3] Fossil fuel use, deforestation, and some agricultural and industrial practices increase greenhouse gases, notably carbon dioxide and methane.^[4] Greenhouse gases absorb some of the heat that the Earth radiates after it warms from sunlight. Larger amounts of these gases trap more heat in Earth's lower atmosphere, causing global warming.

Climate change is causing a range of increasing impacts on the environment. Deserts are expanding, while heat waves and wildfires are becoming more common.^[5] Amplified warming in the Arctic has contributed to melting permafrost, glacial retreat and sea ice loss.^[6] Higher temperatures are also causing more intense storms, droughts, and other weather extremes.^[7] Rapid environmental change in mountains, coral reefs, and the Arctic is forcing many species to relocate or become extinct.^[8] Even if efforts to minimise future warming are successful, some effects will continue for centuries. These include ocean heating, ocean acidification and sea level rise.^[9]

Climate change threatens people with increased flooding, extreme heat, increased food and water scarcity, more disease, and economic loss. Human migration and conflict can also be a result.^[10] The World Health Organization (WHO) calls climate change the greatest threat to global health in the 21st century.^[11] Societies and ecosystems will experience more severe risks without action to limit warming.^[12] Adapting to climate change through efforts like flood control measures or drought-resistant crops partially reduces climate change risks, although some limits to adaptation have already been reached.^[13] Poorer countries are responsible for a small share of global emissions, yet have the least ability to adapt and are most vulnerable to climate change.Many climate change impacts are already felt at the current 1.2 °C (2.2 °F) level of warming. Additional warming will increase these impacts and can trigger tipping points, such as the melting of the Greenland ice sheet.^[14] Under the 2015 Paris Agreement, nations collectively agreed to keep warming "well under 2 °C". However, with pledges made under the Agreement, global warming would still reach about 2.7 °C (4.9 °F) by the end of the century.^[15] Limiting warming to 1.5 °C will require halving emissions by 2030 and achieving net-zero emissions by 2050.^[16]

Reducing emissions requires generating electricity from low-carbon sources rather than burning fossil fuels. This change includes phasing out coal and natural gas fired power plants, vastly increasing use of wind, solar, nuclear and other types of renewable energy, and reducing energy use. Electricity generated from non-carbon-emitting sources will need to replace fossil fuels for powering transportation, heating buildings, and operating industrial facilities.^[18][19] Carbon can also be removed from the atmosphere, for instance by increasing forest cover and farming with methods that capture carbon in soil.^[20]

Index Record

Global warming is the current rise in temperature of the air and oceans. It is happening mainly because humans burn coal, oil, and natural gas; and cut down forests.^[2] Average temperatures today are about 1 °C (1.8 °F) higher than before people started burning a lot of coal around 1750.^[3] In some parts of the world it is less, and in some, more. Most climate 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.^[4]

Global warming is a significant and rapidly accelerating issue caused by human activities, such as greenhouse gas emissions, deforestation, and the burning of fossil fuels. It is having a profound impact on the environment and our planet. The present global warming is mostly because of people burning things, like gasoline for cars 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 greenhouse gases, the increase of carbon dioxide in the atmosphere is the main cause of global warming. Svante Arrhenius predicted this more than a hundred years ago. Arrhenius confirmed the work of Joseph Fourier 200 years ago.When people burn fossil fuels like coal, oil and natural gas this adds carbon dioxide into the air.^[5] 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. Animals which have four places in their stomachs, like cows and sheep, also cause global warming, because their burps contain a greenhouse gas called methane.^[6]

As the Earth's surface temperature becomes hotter the sea level rises. This is partly because water over 4 °C (39 °F) expands when it gets warmer.^[7] It is also partly because warm temperatures make glaciers and ice caps melt. The sea level rise causes coastal areas to flood.^[8] Weather patterns, including where and how much rain or snow there is, are changing. Deserts will probably get bigger. Colder areas will warm up faster than warm areas. Strong storms may become more likely and farming may not make as much food. These changes will not be the same everywhere.^[9]

In the Paris Agreement almost all governments agreed to keep temperature rise below 2 °C (3.6 °F), but current plans are not enough to limit global warming that much.^[10] 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. People could adapt to some temperature change. A few people think nothing should change.

Climate change has happened constantly over the history of the Earth, including the coming and going of ice ages. But modern climate change is different because people are putting carbon dioxide into the atmosphere more quickly than before.^[11][12][13]

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. Compared with before people started burning a lot of coal for industry, the temperature has risen by about 1 °C (1.8 °F).^[3] In 1979, satellites started measuring the temperature of the Earth.^[14]

Before 1850, there were not enough temperature measurements for us to know how warm or cold it was. Climatologists measure other things 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 they were alive.

For most of the past 2000 years the average temperature of the world didn't change much. There were some times where the temperatures were a little warmer or cooler in some places. 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 (not really an ice age). Tree ring dating can only help scientists work out the temperature back to about 10,000 years ago.^[15] Ice cores are used to find out all the temperature back to almost a million years ago,^[16] and for some times to over 4 million years ago.^[17]