What is climate change and what causes it

Why is climate change happening and what are the causes?

What is climate change and what causes it


what is climate change and what causes it

Climate change

Most climate scientists agree the main cause of the current global warming trend is human expansion of the "greenhouse effect" — warming that results when the . Climate change has always happened on Earth, which is clearly seen in the geological record; it is the rapid rate and the magnitude of climate change occurring now that is of great concern worldwide. Greenhouse gases in the atmosphere absorb heat radiation.

The atmosphere is a dynamic fluid that is continually in motion. Both its physical properties and its rate and direction of motion are influenced by a variety of factors, including solar radiationthe geographic position of continentsocean currentsthe location and orientation of mountain ranges, atmospheric chemistryand vegetation growing on the land surface.

All these factors change through time. Some what is climate change and what causes it, such as the distribution of heat within the oceansatmospheric chemistry, and surface vegetation, change at very short timescales.

Others, such as the position of continents and the location and height of mountain ranges, change over very long timescales. Therefore, climate, which results from the physical properties and motion of the atmosphere, varies at every conceivable timescale. Climate is often defined loosely as the average weather at a particular place, incorporating such features as temperatureprecipitationhumidityand windiness.

A more specific definition would state that climate is the mean state and variability of these features over some extended time period. Both definitions acknowledge that the weather is always changing, owing to instabilities in the atmosphere.

And as weather varies from day to day, so too does climate vary, from daily day-and-night cycles up to periods of geologic time hundreds of millions of years long. In a very real sense, climate variation is a redundant expression—climate is always varying. No two years are exactly alike, nor are any two decades, any two centuries, or any two millennia. This article addresses the concept of climatic variation and change within the set of integrated natural features and processes known as the Earth system.

The nature of the evidence for climate change is explained, as are the principal mechanisms that have caused climate change throughout the history of Earth. Finally, a detailed description is given of climate change over many different timescales, ranging from a typical human what is deviation from social norms span to all of geologic time. For full treatment of the most critical issue of climate change in the contemporary world, see global warming.

The atmosphere is influenced by and linked to other features of Earthincluding oceansice masses glaciers and sea iceland surfaces, and vegetation. Together, they make up an integrated Earth system, in which all components interact with and influence one another in often complex ways. Earth scientists and atmospheric scientists are still seeking a full understanding of the complex feedbacks and interactions among the various components of the Earth system. This effort is being facilitated by the development of an interdisciplinary science called Earth system science.

A full understanding of the Earth system requires knowledge of how the system and its components have changed through time. The pursuit of this understanding has led to development of Earth system history, an interdisciplinary science that includes not only the contributions of Earth system scientists but also paleontologists who study the life of past geologic periodspaleoclimatologists who study past climatespaleoecologists who study past environments and ecosystemspaleoceanographers who study the history of the oceansand other scientists concerned with Earth history.

Because different components of the Earth system change at different rates and are relevant at different timescales, Earth system history is a diverse and complex science. Students of Earth system history are not just concerned with documenting what has happened; they also view the past as a series of experiments in which solar radiationocean currentscontinental configurations, atmospheric chemistry, and other important features have varied. These experiments provide opportunities to learn the relative influences of and interactions between various components of the Earth system.

Studies of Earth system history also specify the full array of states the system has experienced in the past and those the system is capable of experiencing in the future.

Undoubtedly, people have always been aware of climatic variation at the relatively short timescales of seasons, years, and decades. Biblical scripture and other early documents refer to droughtsfloodsperiods of severe cold, and other climatic events. Nevertheless, a full appreciation of the nature and what is climate change and what causes it of climatic change did not come about until the late 18th and early 19th centuries, a time when the widespread recognition of the deep antiquity of Earth occurred.

Naturalists of this time, including Scottish geologist Charles LyellSwiss-born naturalist and geologist Louis AgassizWhat is the standard interest rate for a savings account naturalist Charles DarwinAmerican botanist Asa Grayand Welsh naturalist Alfred Russel Wallacecame to recognize geologic and biogeographic evidence that made sense only in the light of past climates radically different from those prevailing today.

Geologists and paleontologists in the 19th and early 20th centuries uncovered evidence of massive climatic changes taking place before the Pleistocene —that is, before some 2.

For example, red beds indicated aridity in regions that are now humid e. Since the late 20th century the development of advanced technologies what wireless headsets work with ps3 dating rocks, together with geochemical techniques and other analytical tools, have revolutionized the understanding of early Earth system history. The occurrence of multiple epochs in recent Earth history during which continental glaciersdeveloped at high latitudes, penetrated into northern Europe and eastern North America was recognized by scientists by the late 19th century.

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External Websites. Articles from Britannica Encyclopedias for elementary and high school students. Stephen T. Alternative Titles: climate variation, climatic change, climatic fluctuation, climatic variation. A series of photographs of the Grinnell Glacier taken from the summit of Mount Gould in Glacier National Park, Montana, in from left,and In the Grinnell Glacier filled the entire area at the bottom of the image.

By it had largely disappeared from this view. Britannica Quiz. Which gases play an important role in climate change? What percentage of scientists agree that humans contribute to this process? Test your knowledge of this "hot" topic with this quiz.

A timeline of important developments in climate change. How to issue cash cheque singapore a Britannica Premium subscription and gain access to exclusive content.

Subscribe Now. Tourist boat in front of a massive iceberg near the coast of Greenland. Drought-resistant plants growing in the Repetek Preserve in the southeastern Karakum Desert, Turkmenistan. Deciduous forest in fall coloration, Wasatch Mountains, Utah. Long-term data sets reveal increased concentrations of the greenhouse gas carbon dioxide in Earth's atmosphere. John P. Load Next Page.

IPCC conclusions

Jan 18,  · Climate change encompasses not only rising average temperatures but also extreme weather events, shifting wildlife populations and and habitats, rising seas, and a range of other impacts. Jun 11,  · Generally speaking, climate change happens when the earth’s climate system adjusts and displays new weather patterns that can last for as little as a few decades or up to millions of years. The climate is constantly changing, and unfortunately, this is a common argument made by people who don’t believe that climate change is something to worry about. Mar 10,  · Climate change, the periodic modification of Earth’s climate caused by atmospheric changes and the atmosphere’s interactions with geologic, chemical, biological, and geographic factors. Loosely defined, climate is the average weather at a distinct place that incorporates temperature, precipitation, and other features.

The atmosphere is a dynamic fluid that is continually in motion. Both its physical properties and its rate and direction of motion are influenced by a variety of factors, including solar radiation , the geographic position of continents , ocean currents , the location and orientation of mountain ranges, atmospheric chemistry , and vegetation growing on the land surface.

All these factors change through time. Some factors, such as the distribution of heat within the oceans , atmospheric chemistry, and surface vegetation, change at very short timescales. Others, such as the position of continents and the location and height of mountain ranges, change over very long timescales.

Therefore, climate, which results from the physical properties and motion of the atmosphere, varies at every conceivable timescale. A more specific definition would state that climate is the mean state and variability of these features over some extended time period. Climate is often defined loosely as the average weather at a particular place, incorporating such features as temperature , precipitation , humidity , and windiness.

Both definitions acknowledge that the weather is always changing, owing to instabilities in the atmosphere. And as weather varies from day to day, so too does climate vary, from daily day-and-night cycles up to periods of geologic time hundreds of millions of years long. In a very real sense, climate variation is a redundant expression—climate is always varying. No two years are exactly alike, nor are any two decades, any two centuries, or any two millennia see also Climate Change Throughout History.

This article addresses the concept of climatic variation and change within the set of integrated natural features and processes known as the Earth system. The nature of the evidence for climate change is explained, as are the principal mechanisms that have caused climate change throughout the history of Earth.

For full treatment of the most critical issue of climate change in the contemporary world, see global warming. The atmosphere is influenced by and linked to other features of Earth , including oceans , ice masses glaciers and sea ice , land surfaces, and vegetation. Together, they make up an integrated Earth system, in which all components interact with and influence one another in often complex ways. Earth scientists and atmospheric scientists are still seeking a full understanding of the complex feedbacks and interactions among the various components of the Earth system.

This effort is being facilitated by the development of an interdisciplinary science called Earth system science. A full understanding of the Earth system requires knowledge of how the system and its components have changed through time. The pursuit of this understanding has led to development of Earth system history, an interdisciplinary science that includes not only the contributions of Earth system scientists but also paleontologists who study the life of past geologic periods , paleoclimatologists who study past climates , paleoecologists who study past environments and ecosystems , paleoceanographers who study the history of the oceans , and other scientists concerned with Earth history.

Because different components of the Earth system change at different rates and are relevant at different timescales, Earth system history is a diverse and complex science. Students of Earth system history are not just concerned with documenting what has happened; they also view the past as a series of experiments in which solar radiation , ocean currents , continental configurations, atmospheric chemistry, and other important features have varied.

These experiments provide opportunities to learn the relative influences of and interactions between various components of the Earth system. Studies of Earth system history also specify the full array of states the system has experienced in the past and those the system is capable of experiencing in the future. Undoubtedly, people have always been aware of climatic variation at the relatively short timescales of seasons, years, and decades. Biblical scripture and other early documents refer to droughts , floods , periods of severe cold, and other climatic events.

Nevertheless, a full appreciation of the nature and magnitude of climatic change did not come about until the late 18th and early 19th centuries, a time when the widespread recognition of the deep antiquity of Earth occurred.

Naturalists of this time, including Scottish geologist Charles Lyell , Swiss-born naturalist and geologist Louis Agassiz , English naturalist Charles Darwin , American botanist Asa Gray , and Welsh naturalist Alfred Russel Wallace , came to recognize geologic and biogeographic evidence that made sense only in the light of past climates radically different from those prevailing today.

Geologists and paleontologists in the 19th and early 20th centuries uncovered evidence of massive climatic changes taking place before the Pleistocene —that is, before some 2. For example, red beds indicated aridity in regions that are now humid e. Since the late 20th century the development of advanced technologies for dating rocks, together with geochemical techniques and other analytical tools, have revolutionized the understanding of early Earth system history.

The occurrence of multiple epochs in recent Earth history during which continental glaciers , developed at high latitudes, penetrated into northern Europe and eastern North America was recognized by scientists by the late 19th century. All historical sciences share a problem: As they probe farther back in time, they become more reliant on fragmentary and indirect evidence. Earth system history is no exception.

High-quality instrumental records spanning the past century exist for most parts of the world, but the records become sparse in the 19th century, and few records predate the late 18th century. Within strict geographic contexts, these sources can provide information on frosts , droughts , floods , sea ice , the dates of monsoons , and other climatic features—in some cases up to several hundred years ago.

Fortunately, climatic change also leaves a variety of signatures in the natural world. Paleoclimatologists study the traces of these effects, devising clever and subtle ways to obtain information about past climates. Most of the evidence of past climatic change is circumstantial, so paleoclimatology involves a great deal of investigative work.

Wherever possible, paleoclimatologists try to use multiple lines of evidence to cross-check their conclusions. They are frequently confronted with conflicting evidence, but this, as in other sciences, usually leads to an enhanced understanding of the Earth system and its complex history. New sources of data, analytical tools, and instruments are becoming available, and the field is moving quickly. Climatic changes of the past — years, especially since the early s, are documented by instrumental records and other archives.

These written documents and records provide information about climate change in some locations for the past few hundred years. Some very rare records date back over 1, years. Researchers studying climatic changes predating the instrumental record rely increasingly on natural archives, which are biological or geologic processes that record some aspect of past climate. These natural archives, often referred to as proxy evidence, are extraordinarily diverse; they include, but are not limited to, fossil records of past plant and animal distributions, sedimentary and geochemical indicators of former conditions of oceans and continents, and land surface features characteristic of past climates.

Paleoclimatologists study these natural archives by collecting cores, or cylindrical samples, of sediments from lakes, bogs , and oceans; by studying surface features and geological strata; by examining tree ring patterns from cores or sections of living and dead trees; by drilling into marine corals and cave stalagmites ; by drilling into the ice sheets of Antarctica and Greenland and the high-elevation glaciers of the Plateau of Tibet , the Andes , and other montane regions; and by a wide variety of other means.

Techniques for extracting paleoclimatic information are continually being developed and refined, and new kinds of natural archives are being recognized and exploited. It is much easier to document the evidence of climate variability and past climate change than it is to determine their underlying mechanisms.

Climate is influenced by a multitude of factors that operate at timescales ranging from hours to hundreds of millions of years. Many of the causes of climate change are external to the Earth system. Others are part of the Earth system but external to the atmosphere. Still others involve interactions between the atmosphere and other components of the Earth system and are collectively described as feedbacks within the Earth system.

Feedbacks are among the most recently discovered and challenging causal factors to study. Nevertheless, these factors are increasingly recognized as playing fundamental roles in climate variation.

The most important mechanisms are described in this section. The luminosity, or brightness, of the Sun has been increasing steadily since its formation. Low solar luminosity during Precambrian time underlies the faint young Sun paradox, described in the article Climate Change Throughout History. Radiative energy from the Sun is variable at very small timescales, owing to solar storms and other disturbances, but variations in solar activity, particularly the frequency of sunspots , are also documented at decadal to millennial timescales and probably occur at longer timescales as well.

Volcanic activity can influence climate in a number of ways at different timescales. A recent example is the eruption in the Philippines of Mount Pinatubo , which had measurable influences on atmospheric circulation and heat budgets. New England and Europe experienced snowfalls and frosts throughout the summer of Volcanoes and related phenomena, such as ocean rifting and subduction, release carbon dioxide into both the oceans and the atmosphere. Emissions are low; even a massive volcanic eruption such as Mount Pinatubo releases only a fraction of the carbon dioxide emitted by fossil-fuel combustion in a year.

At geologic timescales, however, release of this greenhouse gas can have important effects. Variations in carbon dioxide release by volcanoes and ocean rifts over millions of years can alter the chemistry of the atmosphere. Such changeability in carbon dioxide concentrations probably accounts for much of the climatic variation that has taken place during the Phanerozoic Eon. These movements have changed the shape, size, position, and elevation of the continental masses as well as the bathymetry of the oceans.

Topographic and bathymetric changes in turn have had strong effects on the circulation of both the atmosphere and the oceans. For example, the uplift of the Tibetan Plateau during the Cenozoic Era affected atmospheric circulation patterns, creating the South Asian monsoon and influencing climate over much of the rest of Asia and neighbouring regions.

Tectonic activity also influences atmospheric chemistry, particularly carbon dioxide concentrations. Carbon dioxide is emitted from volcanoes and vents in rift zones and subduction zones. Even the chemical weathering of rock constitutes an important sink for carbon dioxide. A carbon sink is any process that removes carbon dioxide from the atmosphere by the chemical conversion of CO 2 to organic or inorganic carbon compounds.

Carbonic acid, formed from carbon dioxide and water , is a reactant in dissolution of silicates and other minerals. Weathering rates are related to the mass, elevation, and exposure of bedrock. Tectonic uplift can increase all these factors and thus lead to increased weathering and carbon dioxide absorption. For example, the chemical weathering of the rising Tibetan Plateau may have played an important role in depleting the atmosphere of carbon dioxide during a global cooling period in the late Cenozoic Era.

The orbital geometry of Earth is affected in predictable ways by the gravitational influences of other planets in the solar system. This variation occurs on a cycle of 41, years. In general, the greater the tilt, the greater the solar radiation received by hemispheres in summer and the less received in winter.

These two processes create a 26,year cycle, called precession of the equinoxes , in which the position of Earth at the equinoxes and solstices changes. Today Earth is closest to the Sun perihelion near the December solstice, whereas 9, years ago perihelion occurred near the June solstice. Vegetation also influences greenhouse gas concentrations; living plants constitute an important sink for atmospheric carbon dioxide, whereas they act as sources of carbon dioxide when they are burned by wildfires or undergo decomposition.

These orbital variations cause changes in the latitudinal and seasonal distribution of solar radiation, which in turn drive a number of climate variations. Orbital variations play major roles in pacing glacial-interglacial and monsoonal patterns. Their influences have been identified in climatic changes over much of the Phanerozoic.

For example, cyclothems —which are interbedded marine, fluvial, and coal beds characteristic of the Pennsylvanian Subperiod Carbon dioxide , methane , and water vapour are the most important greenhouse gases, and they have a profound effect on the energy budget of the Earth system despite making up only a fraction of all atmospheric gases.

In general, greenhouse gas concentrations have been particularly high during warm periods and low during cold phases. A number of processes influence greenhouse gas concentrations.

Some, such as tectonic activities, operate at timescales of millions of years, whereas others, such as vegetation, soil, wetland, and ocean sources and sinks, operate at timescales of hundreds to thousands of years. Human activities—especially fossil-fuel combustion since the Industrial Revolution—are responsible for steady increases in atmospheric concentrations of various greenhouse gases, especially carbon dioxide, methane, ozone , and chlorofluorocarbons CFCs.

Perhaps the most intensively discussed and researched topic in climate variability is the role of interactions and feedbacks among the various components of the Earth system.

The feedbacks involve different components that operate at different rates and timescales. Ice sheets, sea ice , terrestrial vegetation, ocean temperatures, weathering rates, ocean circulation, and greenhouse gas concentrations are all influenced either directly or indirectly by the atmosphere ; however, they also all feed back into the atmosphere, thereby influencing it in important ways.

At the same time, the transfer of water molecules from soil to the atmosphere is mediated by vegetation, both directly from transpiration through plant stomata and indirectly from shading and temperature influences on direct evaporation from soil.



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