Title: Climate change Content: Climate change is the climate of Earth changing. The Earth's climate has been much hotter and colder than it is today. Climate change this century and last century is sometimes called global warming, because the average temperature on the surface has risen. The climate is now changing much faster than it has in the recent past. This is because people are putting heat-trapping greenhouse gases in Earth's atmosphere. When people talk about climate change they are usually talking about the problem of human-caused global warming, which is happening now (see global warming for more details). But the climate of the Earth has changed over not just thousands of years, but tens or hundreds of millions of years. Sometimes, before there were people, the Earth's climate was much hotter than it is today. For example about 60 million years ago there were a lot of volcanoes, which burnt a lot of underground organic matter (squashed and fossilized dead plants and animals like coal, gas and oil) so a lot of carbon dioxide and methane went up in the air like nowadays. This made the Earth hot enough for giant tortoises and alligators to live in the Arctic. At times in the past, the temperature was much cooler, with the last glaciation ending about ten thousand years ago.Imbrie J. & Imbrie, K.P. 1979. Ice ages: solving the mystery. Short Hills NJ: Enslow. ISBN 978-0-89490-015-0Alley R.B. 2000. The two-mile time machine: ice cores, abrupt climate change, and our future. Princeton University Press. ISBN 0-691-10296-1 Ice Ages are long times when the Earth got colder, and more ice froze at the North and South Poles. Sometimes even the whole Earth was covered in ice, and was much colder than today. There is no one reason why there are Ice Ages. Changes in the Earth's orbit around the Sun, and the Sun getting brighter or dimmer are events which do happen. Also how much the Earth is tilted compared to the Sun might make a difference. Another source of change is the activities of living things (see Great Oxygenation Event and Huronian glaciation). A snowball period, c2.4–c2.0 billion years ago, triggered by the Great Oxygenation Event == Hot Earth == Sometimes, before there were people, the Earth's climate was much hotter than it is today. For example about 60 million years ago there were a lot of volcanoes, which burnt a lot of underground organic matter (squashed and fossilized dead plants and animals like coal, gas and oil) so a lot of carbon dioxide and methane went up in the air like nowadays. This made the Earth hot enough for giant tortoises and alligators to live in the Arctic. == Cold Earth == === Glaciations === At times in the past, the temperature was much cooler, with the last glaciation ending about ten thousand years ago. === Ice Ages === Ice Ages are long times (much much longer than glaciations) when the Earth got colder, and more ice froze at the North and South Poles. Sometimes even the whole Earth was covered in ice, and was much colder than today. There is no one reason why there are Ice Ages. Changes in the Earth's orbit around the Sun, and the Sun getting brighter or dimmer are events which do happen. Also how much the Earth is tilted compared to the Sun might make a difference. Another source of change is the activities of living things (see Great Oxygenation Event and Huronian glaciation). == History of climate change studies == Joseph Fourier in 1824, Claude Poulliet in 1827 and 1838, Eunace Foote (18191888) in 1856, Irish physicist John Tyndall (1820–1893) in 1863 onwards,Tyndall J. 1863. Heat as a mode of motion. London & New York. Svante Arrhenius in 1896, and Guy Stewart Callendar (1898–1964) discovered the importance of carbon dioxide (CO2) in climate change. Foote's work was not appreciated, and not widely known. Tyndall proved there were other greenhouse gases as well. Nils Gustaf Ekholm in 1901 invented the term. === The 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. Therefore the changes in the Sun are not causing the global warming which is happening now. ==Related pages== *Ecology *Intergovernmental Panel on Climate Change