Climate change is a change in the statistical distribution of weather patterns when the change takes place over a long period of time (ie, decades to millions of years). Climate change can refer to changes in average weather conditions, or in weather time variations in the context of long-term average conditions. Climate change is caused by factors such as biotic processes, variations in solar radiation the Earth receives, tectonic plates, and volcanic eruptions. Certain human activities have been identified as a major cause of ongoing climate change, often referred to as global warming.
Scientists actively work to understand the climate of the past and the future by using observations and theoretical models. Climate records - which extend deep into Earth's past - have been assembled, and continue to be built, based on geological evidence from the hole temperature profiles, nuclei removed from the accumulation of ice, flora and fauna records, glacial and periglacial processes. , stable-isotope and other analyzes of sedimentary layers, and sea-level records in the past. More recent data is provided by instrumental notes. General circulation models, based on physical science, are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects to climate change.
Video Climate change
Terminology
The most common definition of climate change is a change in the statistical properties (especially average and spread) of the climate system when considered for long periods of time, regardless of the cause. Thus, fluctuations during shorter periods of several decades, such as El Nià ± o, do not represent climate change.
The term "climate change" is often used to refer specifically to anthropogenic climate change (also known as global warming). Anthropogenic climate change is caused by human activity, as opposed to changes in climate that may be generated as part of Earth's natural processes. In this sense, especially in the context of environmental policy, the term climate change has become synonymous with anthropogenic global warming. In scientific journals, global warming refers to rising surface temperatures while climate change includes global warming and everything else that increases greenhouse gas levels.
The related term, "climate change", proposed by the World Meteorological Organization (WMO) in 1966 to cover all forms of climate variability on a time scale longer than 10 years, but regardless of the cause. During the 1970s, the term climate change replaces climate change to focus on anthropogenic causes, as it becomes clear that human activity has the potential to drastically change climate. Climate change is included in the heading of the Intergovernmental Panel on Climate Change (IPCC) and the United Nations Framework Convention on Climate Change (UNFCCC). Climate change is now used both as a technical description of the process, as well as a noun used to describe the problem.
Maps Climate change
Cause
On the broadest scale, the energy levels received from the Sun and its rate of loss in space determine the equilibrium temperatures and Earth's climate. This energy is distributed throughout the world by wind, ocean currents, and other mechanisms to influence the climate of different regions.
Factors that can form a climate are called climate forcings or "force mechanisms". These include processes such as variations in solar radiation, variations in Earth orbit, variations of albedo or reflectivity from continents, atmosphere, and oceans, mountain-building and continental drift and changes in greenhouse gas concentrations. There are various climate change inputs that can strengthen or reduce initial coercion. Some parts of the climate system, such as oceans and ice caps, respond more slowly as a reaction to climate change, while others respond more quickly. There is also a key threshold factor that, when exceeded, can lead to rapid changes.
Coercive mechanisms can be either "internal" or "external". The mechanism of internal coercion is a natural process in the climate system itself (eg, thermohaline circulation). External coercion mechanisms can be natural (eg, changes in solar output, earth orbit, volcanic eruptions) or anthropogenic (eg increased greenhouse gas and dust emissions).
Whether the initial coercion mechanism is internal or external, the response of the climate system may be rapid (eg, sudden cooling due to volcanic ash in the air reflecting sunlight), slow (eg heat expansion from sea water heating), or combination (eg, - in the Arctic Ocean when sea ice melts, followed by a more gradual thermal expansion of water). Therefore, the climate system can respond abruptly, but the full response to coercion mechanisms may not be fully developed for centuries or even longer.
Internal coercion mechanism
Scientists generally define the five components of the Earth's climate system to include atmospheres, hydrospheres, cryosphere, lithosphere (limited to soil surface, rocks, and sediments), and biosphere. Natural changes in the climate system ("internal forcings") produce an internal "climate variability". Examples include species type and distribution, and changes in atmospheric ocean circulation.
Ocean-atmosphere variation
Oceans and the atmosphere can work together to spontaneously produce internal climate variability that can last for years to decades at a time. Examples of these variability types are El NiÃÆ'Â Â o-Southern Oscillation, Pacific decadal oscillations, and South Atlantic Oscillations. This variation can affect the average global surface temperature by distributing heat between the deep ocean and the atmosphere and/or by changing the distribution of clouds/moisture/sea ice that can affect the total energy budget of the earth.
The oceanic aspect of this circulation can produce variability on a hundred-year time scale because the oceans have hundreds of times more mass than in the atmosphere, and thereby very high thermal inertia. For example, changes in ocean processes such as thermohaline circulation play a key role in distributing heat in the world's oceans. Due to the long time span of this circulation, ocean temperatures at depth still adjust to the effects of the Small Ice Age occurring between 1600 and 1800s.
Life
Life affects the climate through its role in the carbon and water cycle and through mechanisms such as albedo, evapotranspiration, cloud formation, and weathering. Examples of how life affects the past climate include:
- glaciation 2.3 billion years ago was triggered by the evolution of oxygenic photosynthesis, which depleted the greenhouse gas carbon dioxide atmosphere and introduced free oxygen.
- Another glaciation 300 million years ago was brought by a long-lasting decomposition-resistant detritus of vascular land-plants (creating carbon sinks and coal formation)
- Maximum Paleocene-Eocene termination 55 million years ago by developing marine phytoplankton
- the reversal of global warming 49 million years ago by 800,000 years of arctic azolla roses
- global cooling over the past 40 million years is driven by the expansion of the grazer-grass ecosystem
The mechanism of external coercion
Orbital variation
The slight variation in Earth movements causes a change in the seasonal distribution of sunlight that reaches the Earth's surface and how it is distributed throughout the world. There is little change in average mean sunshine averaged each year; but there can be a strong change in geographic and seasonal distribution. Three types of kinematic changes are variations in the eccentricity of the Earth, changes in the angle of the Earth's axis of rotation, and the precession of the Earth's axis. Combined together, this results in a milankovitch cycle that affects the climate and is important for their correlation to glacial and interglacial periods, their correlation with the progress and decline of the Sahara, and for their appearance in the stratigraphic record.
The IPCC notes that the Milankovitch cycle pushes the ice age cycle, CO 2 to follow changes in temperature "with lag of several hundred years", and that as a temperature change is amplified. The ocean depth has a time lag in changing the temperature (thermal inertia at that scale). After a change in sea water temperature, the solubility of CO 2 in the ocean changes, as well as other factors affecting the air-sea exchange CO 2 .
Solar power output
The sun is the main source of energy input to Earth. Other sources include geothermal energy from the Earth's core, the tidal energy of the Moon and the heat from the decay of radioactive compounds. Both long-term and short-term variations in solar intensity are known to affect global climate.
Three to four billion years ago, the Sun only emits 75 percent of its current strength. If the composition of the atmosphere is the same as today, liquid water should not exist on Earth. However, there is evidence of early Earth water, in the Hadean and Archean eons, leading to what is known as the vague Sun paradox. The hypothesis solution for this paradox includes a very different atmosphere, with a higher greenhouse gas concentration than currently available. Over the next 4 billion years, the output of solar energy increases and the composition of the atmosphere changes. The Great Oxygenation event - atmospheric oxygenation about 2.4 billion years ago - is the most important change. For the next five billion years from now, the supreme death of the Sun as he becomes a red giant and then a white dwarf will have a profound effect on the climate, with the red giant phase likely to end any life on Earth that survived until then.
The solar output varies on shorter time scales, including an 11-year solar cycle and long-term modulation. Variations in the intensity of the sun, possibly as a result of Wolf, SpÃÆ'¶rer, and Maunder Minima, are considered influential in triggering the Little Ice Age. The event was extended from 1550 to 1850 A.D. and characterized by relative cooling and a greater degree of glaciers than the centuries before and after. Sun variations may also have an impact on some observed heating from 1900 to 1950. The nature of the solar energy output cycle is not fully understood; it differs from the very slow changes that take place inside the Sun as it is centuries and evolved.
Some studies show that solar radiation increases from sunspots activity that affects global warming, and climate may be affected by the sum of all effects (solar variations, anthropogenic radiation forcings, etc.).
A 2010 study showed "that the effects of solar variability at temperatures throughout the atmosphere may be contrary to current expectations."
In 2011, CERN announced preliminary results from CLOUD experiments in the journal Nature. The results show that ionization of cosmic rays significantly increases aerosol formation in the presence of sulfuric acid and water, but in lower atmospheres where ammonia is also needed, this is not enough to take into account the formation of aerosols and additional steam traces should be involved. The next step is to discover more about this steam trail, including whether it comes from nature or humans.
Volcanism
The eruptions considered large enough to affect Earth's climate on a scale of more than 1 year are those that inject more than 100,000 tons of SO 2 into the stratosphere. This is due to the optical properties of SO 2 and sulfate aerosols, which greatly absorb or disperse solar radiation, creating a global layer of sulfuric acid mist. On average, such eruptions occur several times per century, and cause cooling (by blocking some of the transmission of solar radiation to the Earth's surface) for a period of several years.
The eruption of Mount Pinatubo in 1991, the second largest terrestrial eruption in the 20th century, affected the climate substantially, then global temperatures decreased by about 0.5 ° C (0.9 ° F) to three years. Thus, cooling in most of the Earth reduced surface temperatures in 1991-93, equivalent to a reduction in 4 watts of radiation per square meter. The eruption of Mount Tambora in 1815 led to a Year Without a Summer. A much larger eruption, known as large coal provinces, occurs only a few times every fifty - one hundred million years - through basal floods, and causes the Earth to pass through global warming and mass extinctions.
Small eruptions, with injections of less than 0.1 Mt sulfur dioxide into the stratosphere, have only an impact on the atmosphere, as temperature changes are proportional to natural variability. However, because smaller eruptions occur at much higher frequencies, they also have a significant impact on Earth's atmosphere.
Seismic mapping maps current and future trends in volcanic activity, and tries to develop early warning systems. In climate modeling, the goal is to study the physical mechanism and feedback of volcanic forces.
Volcanoes are also part of an extended carbon cycle. Over a very long period of time (geologically), they release carbon dioxide from the Earth's crust and mantle, counteracting absorption by sedimentary rocks and other geological carbon dioxide sinks. The US Geological Survey estimates that volcanic emissions are at a much lower level than the effects of current human activities, which produce 100-300 times the amount of carbon dioxide emitted by volcanoes. The published study review shows that annual volcanic carbon dioxide emissions, including volumes that are detached from the mountains in the middle of the ocean, volcanic arcs, and hot spot volcanoes, are only equivalent to 3 to 5 days of human-induced output. The annual number spent by human activities may be greater than the amount released by supererup, the most recent being the Toba eruption in Indonesia 74,000 years ago.
Although volcanoes are technically part of the lithosphere, which is part of the climate system, the IPCC explicitly defines volcanism as an external coercive agent.
Plate tectonics
For millions of years, tectonic plate movements are repeating global terrain and oceans and producing topography. This can affect climate patterns and global and local atmospheric-ocean circulations.
The position of the continent determines the geometry of the oceans and therefore affects the pattern of ocean circulation. Sea locations are essential in controlling heat transfer and humidity worldwide, and therefore, in determining the global climate. The latest example of tectonic controls on ocean circulation is the formation of the Isthmus of Panama about 5 million years ago, which shut off direct mixing between the Atlantic Ocean and the Pacific. This greatly affects the dynamics of the ocean from what is now a Gulf Stream and may have caused an ice sheet in the northern hemisphere. During the Carboniferous period, some 300 to 360 million years ago, tectonic plates may have triggered large-scale carbon storage and increased glaciation. Geological evidence suggests "megamonsoonal" circulation patterns during the Pangea supercontinent, and climate modeling suggests that the presence of the supercontinent is conducive to monsoon formation.
The size of the continent is also important. Due to the effect of stable oceans on temperature, annual temperature variations are generally lower in coastal areas than on land. Therefore, the larger superbenua will have more areas where the climate is very seasonal than some smaller continents or islands.
Human influence
In the context of climate variations, anthropogenic factors are human activities that affect the climate. The scientific consensus on climate change is "that the climate is changing and that this change is largely due to human activity," and that "it is very irreversible".
"... there is strong and credible evidence, based on various fields of research, documenting that the climate is changing and that this change is largely due to human activity.While much remains to be learned, core phenomena, scientific questions, and hypotheses have been examined thoroughly and has stood firm in the face of serious scientific debate and careful evaluation of alternative explanations. "
The most concerning factor in this anthropogenic factor is the increase in CO 2 . This is due to emissions from burning fossil fuels, followed by aerosols (particle matter in the atmosphere), and CO 2 released by the cement plant. Other factors, including land use, ozone depletion, livestock (ruminants like cattle produce methane, as well as termites), and deforestation, are also a concern in the role they play - both separately and along with other factors - in influencing climate, micro climate, and the size of climate variables.
Other mechanisms
The Earth receives the entry of ionized particles known as cosmic rays from various external sources, including the Sun. A hypothesis states that increasing cosmic ray flux increases ionisation in the atmosphere, leading to a larger cloud cover. This, in turn, will tend to cool the surface. Non-solar cosmic ray fluxes may vary as a result of nearest supernova events, the solar system passing through interstellar interstellar clouds, or oscillatory motions from the Sun's position with respect to the galactic plane. The latter can increase the high-energy cosmic ray flux derived from the Virgo cluster.
There is evidence that the impact of Chicxulub about 66 million years ago has greatly affected Earth's climate. A large number of sulfate aerosols are kicked into the atmosphere, lowering global temperatures by 26 ° C and producing sub-frozen temperatures over a 3-16 year period. The recovery time for this event takes more than 30 years.
Physical evidence
Evidence for climate change is drawn from a variety of sources that can be used to reconstruct the past climate. Complete global records of available surface temperatures from the mid-19th century. For the previous period, most of the evidence is indirect climate change inferred from changes in proxies, indicators that reflect climate, such as vegetation, ice cores, dendrochronology, sea-level changes, and glacial geology.
Measurement and proxy temperature
Note the instrumental temperatures of surface stations are equipped with radioactive balloons, extensive atmospheric monitoring in the mid-20th century, and, from the 1970s, with global satellite data as well. Taking the record as a whole, most of the 20th century has never been warm before, whereas the 19th and 17th centuries are quite cold. The ratio of 18 O/ 16 O in the calcite sample and the ice core used to infer marine temperature in the past is an example of a temperature proxy method, as are other climate metrics. recorded in subsequent categories.
Historical and archaeological evidence
Climate change in the past can be detected with appropriate changes in residential and agricultural patterns. Archaeological evidence, oral history and historical documents can provide insight into past changes in the climate. The effects of climate change have been attributed to the rise and also the collapse of various civilizations.
Glacier
Glaciers are considered one of the most sensitive indicators of climate change. Their size is determined by the mass balance between the snow input and the melting output. When temperatures are warm, glaciers retreat except for increased snowfall to cover additional thaws; The converse is also true.
Glaciers grow and shrink due to natural variability and external forcings. The variability of temperature, precipitation, and hydrology of the hydrology and oclacial greatly determine the evolution of glaciers in certain seasons. Therefore, one should average more than a decade or more time scale and/or more individual glaciers to smooth local short-term variability and gain glacier history associated with climate.
Global glacier inventories have been compiled since the 1970s, initially based primarily on aerial photographs and maps but now rely more on satellites. The compilation tracked over 100,000 glaciers covering an area of ​​approximately 240,000 km 2 , and initial estimates indicate that the remaining ice sheet is about 445,000 km 2 . The Glacier Monitoring Service collects annual data about glaciers and the mass balance of glaciers. From this data, glaciers around the world have been found to shrink significantly, with strong glacier cracks in the 1940s, stable or evolving conditions during the 1920s and 1970s, and back again from the mid-1980s to the present.
The most significant climatic processes from mid to late Pliocene (about 3 million years ago) were glacial and interglacial cycles. The current interglacial period (Holocene) has lasted approximately 11,700 years. Formed by orbital variations, responses such as the rise and fall of continental ice sheets and significant sea level changes help create a climate. Other changes, including the Heinrich event, the Dansgaard-Oeschger and Younger Dryas events, however, illustrate how glacial variations can also affect the climate without orbital coercion.
Glaciers leave moraines containing a lot of material - including organic matter, quartz, and potasium that may be dated - noting the period in which the glaciers progressed and retreated. Similarly, with tephrochronological techniques, the lack of glacier cover can be identified by the presence of a tiger soil or volcanic tephra that dates of deposits can also be ascertained.
Data from NASA's Grace satellite show that Antarctic soil ice sheets (top graphs) and Greenland (lower) have been losing mass since 2002. Both ice sheets have seen accelerated ice loss loss since 2009.
Arctic sea ice loss
The decline of Arctic sea ice, both in size and thickness, over the last few decades is further evidence for rapid climate change. Sea ice is frozen sea water that floats on the sea surface. It covers millions of square kilometers in the polar regions, varying with the seasons. In the Arctic, some sea ice remains year to year, whereas almost all the Southern Ocean or Antarctic sea ice melts and changes every year. Satellite observations show that Arctic sea ice is now declining at a rate of 13.2 percent per decade, relative to the 1981 to 2010. An unprecedented 2007 Arctic sea ice crack. Decades of shrinking and thinning in a warm climate have put Arctic sea ice in a dangerous position, now vulnerable to atmospheric anomalies. "Both the level and the volume anomaly fluctuate slightly from January to July and then decline sharply in August and September". This decrease is due to reduced ice production as a result of the extraordinarily high SAT. During the Arctic summer, the slower rate of sea ice production is similar to the faster rate of melting sea ice.
Vegetation
Changes in the type, distribution and coverage of vegetation can occur due to climate change. Some changes in climate can lead to increased rainfall and warmth, resulting in better plant growth and sequestration of CO2 in the air 2 . A gradual increase in warmth in a region will lead to a flowering and flowering period before, inducing changes in the lifecycle settings of the dependent organism. Conversely, the cold will cause the bioprocess cycle to be lag. Larger, faster or more radical changes, however, can lead to vegetation stress, rapid plant loss and desertification under certain circumstances. This example occurred during Carboniferous Rainforest Collapse (CRC), an extinction event 300 million years ago. Today the vast rainforest covers the equatorial regions of Europe and America. Climate change destroys this tropical rain forest, suddenly breaking the habitat into an isolated 'island' and causing the extinction of many plant and animal species.
Forest genetic resources
Although this is a field with a lot of uncertainty, it is expected that over the next 50 years climate change will have an impact on the diversity of genetic resources of the forest and thus on the distribution of forest tree species and forest composition. The diversity of forest genetic resources allows the potential for a species (or population) to adapt to climate change and related future challenges such as changes in temperature, drought, pests, diseases and forest fires. However, species are not naturally able to adapt in the rate of climate change and temperature increases will most likely facilitate the spread of pests and diseases, creating additional threats to forest trees and their populations. To inhibit these problems, human intervention, such as the transfer of forest reproduction materials, may be necessary.
Pollen analysis
Palynology is the study of contemporary and fossil palynomorphs, including pollen. Palynology is used to infer the geographic distribution of plant species, which vary under different climatic conditions. Different plant groups have pollen with a distinctive surface shape and texture, and since the outer surface of the pollen consists of highly resistant materials, they resist decay. Changes in the type of pollen found in different layers of sediment in lakes, swamps, or river deltas show changes in the plant community. This change is often a sign of climate change. For example, palitography studies have been used to track changes in vegetation patterns across Quaternary glaciers and especially since the last glacial maximum.
Cloud cover and precipitation
Past precipitation can be estimated in the modern era with a global network of rainfall gauges. Surface coverage over oceans and remote areas is relatively rare, but, reducing dependence on interpolation, satellite clouds and rainfall data has been available since the 1970s. Quantification of climatological variations of precipitation in the previous century was incomplete but was estimated to use proxies such as marine sediments, ice cores, cavernous stalagmites, and tree rings. In July 2016, scientists published evidence of an increase in cloud cover in the polar regions, as predicted by climate models.
Climatological temperatures substantially affect cloud cover and rainfall. For example, during the last Glacial Maximum of 18,000 years ago, thermal evaporation was driven from the ocean to a low continent, causing a vast desert area, including a polar desert (cold but with cloud cover and low rainfall). In contrast, the world's climate is more cloudy and wetter than it was today before the start of the warm Atlantic Period 8000 years ago.
Global rainfall estimates rose by about 2% during the 20th century, although the calculated trends varied if different endpoints were selected, complicated by ENSO and other oscillations, including greater global cloud cover rainfall in the 1950s and 1970s rather than the later 1980s and 1990s despite the positive trends over the entire century. The same overall small increase in global river runoff and average soil moisture has been perceived.
Dendroclimatology
Dendroclimatology is the analysis of tree ring growth patterns to determine past climate variations. Wide and thick rings show a fertile, well-watered period of growth, while thin and narrow rings show lower periods of rainfall and less ideal growth conditions.
Ice core
Ice analysis in the core drilled from ice sheets such as Antarctic ice sheets can be used to show the relationship between global temperature and sea level variations. The air trapped in bubbles in ice can also reveal the variations of CO 2 from the atmosphere from the past, long before the effects of modern environments. This study of ice cores has been a significant indicator of changes in CO 2 for several millennia, and continues to provide valuable information about the difference between ancient and modern atmospheric conditions.
Animal
The remains of beetles are commonly found in freshwater and soil sediments. Different beetle species tend to be found under different climatic conditions. Given the lineage of beetles that are genetically unchanged significantly over thousands of years, knowledge of the current climate range of different species, and the age of sediments where remains found, climatic conditions in the past can be inferred. Studies on the impact on vertebrates are few from developing countries, where there are fewest studies; between 1970 and 2012, vertebrates dropped by 58 percent, with freshwater, marine and terrestrial populations declining by 81, 36, and 35 percent respectively.
Similarly, the historical abundance of various fish species has been found to have a substantial relationship with observed climatic conditions. Changes in the major productivity of autotrophs in the oceans can affect seafood nets.
Sea level change
Global sea level changes for much of the last century are generally estimated using tidal gauge measurements collected over a long period of time to provide long-term average. Recently, altimeter measurements - in combination with precisely specified satellite orbits - have provided increased measurements of global sea level changes. To measure sea level before instrument measurements, scientists have dated coral reefs that grow near the surface of the ocean, coastal sediments, sea terraces, limestone water, and archaeological remains near the shore. The main dating method used is the uranium and radiocarbon series, with cosmogenic radionuclides that are sometimes used to date with terraces that have experienced relative sea level decline. At the beginning of Pliocene, global temperatures are 1-2 Â ° C warmer than current temperatures, but sea levels are 15-25 meters higher than current.
Source of the article : Wikipedia
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