Climate change 47512 225991859 2008-07-16T10:30:52Z Trasman 6721496 /* Climate change and agriculture */ {{pp-semi-indef}} {{atmospheric sciences}} [[Image:Vostok-ice-core-petit.png|thumb|right|350px|Variations in CO<sub>2</sub>, temperature and dust from the [[Vostok, Antarctica|Vostok]] ice core over the last 450,000 years]] {{for|current global climate change|Global warming}} '''Climate change''' is any long-term significant change in the “average weather” that a given region experiences. Average weather may include average temperature, precipitation and wind patterns. It involves changes in the variability or average state of the atmosphere over [[duration]]s ranging from decades to millions of years. These changes can be caused by dynamic processes on [[Earth]], external forces including variations in sunlight intensity, and more recently by [[human]] activities. In recent usage, especially in the context of [[environmental policy]], the term "climate change" often refers to changes in modern [[climate]] (see [[global warming]]). For information on temperature measurements over various periods, and the data sources available, see [[temperature record]]. For attribution of climate change over the past century, see [[attribution of recent climate change]]. == Climate change factors == {{Refimprove|date=February 2008}} Climate changes reflect variations within the Earth's atmosphere, processes in other parts of the Earth such as oceans and [[cryosphere|ice caps]], and the effects of human activity. The external factors that can shape climate are often called [[climate forcing]]s and include such processes as variations in [[solar radiation]], the Earth's [[orbit]], and [[greenhouse gas]] concentrations. === Variations within the Earth's climate === Weather is the day-to-day state of the atmosphere, and is a [[chaos|chaotic]] non-linear [[dynamical system]]. On the other hand, ''climate'' &mdash; the average state of weather &mdash; is fairly stable and predictable. Climate includes the average temperature, amount of precipitation, days of sunlight, and other variables that might be measured at any given site. However, there are also changes within the Earth's environment that can affect the climate. ==== Glaciation ==== [[Image:Glaciertermalp.JPG|left|thumb|300px|Percentage of advancing glaciers in the Alps in the last 80 years]] [[Glacier]]s are recognized as being among the most sensitive indicators of climate change, advancing substantially during climate cooling (e.g., the [[Little Ice Age]]) and retreating during climate warming on moderate time scales. Glaciers grow and collapse, both contributing to natural variability and greatly amplifying externally forced changes. For the last [[century]], however, glaciers have been unable to regenerate enough [[ice]] during the winters to make up for the ice lost during the summer months (see [[Retreat of glaciers since 1850|glacier retreat]]). The most significant climate processes of the last several million years are the glacial and [[interglacial]] cycles of the present [[ice age]].{{Fact|date=February 2008}} Though shaped by [[Milankovitch cycles|orbital variations]], the internal responses involving [[continental]] ice sheets and 130 m sea-level change certainly played a key role in deciding what climate response would be observed in most regions. Other changes, including [[Heinrich event]]s, [[Dansgaard–Oeschger event]]s and the [[Younger Dryas]] show the potential for glacial variations to influence climate even in the absence of specific orbital changes. ==== Ocean variability ==== [[Image:Ocean circulation conveyor belt.jpg|thumb|300px|A schematic of modern [[thermohaline]] circulation]] On the scale of decades, climate changes can also result from interaction of the atmosphere and oceans. Many climate fluctuations — including not only the [[ENSO|El Niño Southern oscillation]] (the best known) but also the [[Pacific decadal oscillation]], the [[North Atlantic oscillation]], and the [[Arctic oscillation]] — owe their existence at least in part to different ways that heat can be stored in the oceans and move between different reservoirs. On longer time scales ocean processes such as [[thermohaline circulation]] play a key role in redistributing heat, and can dramatically affect climate. ==== The memory of climate ==== More generally, most forms of internal variability in the climate system can be recognized as a form of [[hysteresis]], meaning that the current state of climate reflects not only the inputs, but also the history of how it got there. For example, a decade of dry conditions may cause lakes to shrink, plains to dry up and deserts to expand. In turn, these conditions may lead to less rainfall in the following years. In short, climate change can be a self-perpetuating process because different aspects of the environment respond at different rates and in different ways to the fluctuations that inevitably occur.{{Fact|date=March 2008}} === Non-climate factors driving climate change === ==== Effects of CO2 on climate change ==== {{main|Greenhouse gas}} [[Image:Phanerozoic Carbon Dioxide.png|right|thumb|300px|Carbon dioxide variations during the last 500 million years]] [[Attribution of recent climate change#Scientific literature and opinion|Current studies]] indicate that [[radiative forcing]] by [[greenhouse gas]]es is the primary cause of global warming. Greenhouse gases are also important in understanding Earth's climate history. According to these studies, the [[greenhouse effect]], which is the warming produced as greenhouse gases trap heat, plays a key role in regulating Earth's temperature. Over the last 600 million years, [[carbon dioxide]] concentrations have varied from perhaps >5000 [[parts per notation|ppm]] to less than 200 ppm, due primarily to the effect of geological processes and biological innovations. Royer et al.<ref name="royer2007">{{cite journal |author=Royer DL, Berner RA, Park J |title=Climate sensitivity constrained by CO<sub>2</sub> concentrations over the past 420 million years |journal=[[Nature]] |volume=446 |issue=7135 |pages=530–2 |year=2007 |doi=10.1038/nature05699}}</ref> have used the CO<sub>2</sub>-climate correlation to derive a value for the [[climate sensitivity]]. There are several examples of rapid changes in the concentrations of greenhouse gases in the [[Earth's atmosphere]] that do appear to correlate to strong warming, including the [[Paleocene-Eocene thermal maximum|Paleocene–Eocene thermal maximum]], the [[Permian-Triassic extinction event|Permian–Triassic extinction event]], and the end of the Varangian [[snowball earth]] event. During the modern era, the naturally rising [[carbon dioxide]] levels are implicated as the [[attribution of recent climate change|primary cause]] of [[global warming]] since 1950. According to the Intergovernmental Panel on Climate Change (IPCC), 2007, the atmospheric concentration of CO<sub>2</sub> in 2005 was 379 ppm³ compared to the pre-industrial levels of 280 ppm³. [[Thermodynamics]] and [[Le Chatelier's principle]] explain the characteristics of the dynamic equilibrium of a gas in solution such as the vast amount of CO<sub>2</sub> held in solution in the world's oceans moving into and returning from the atmosphere. These principles can be observed as bubbles which rise in a pot of water heated on a stove, or in a glass of cold beer allowed to sit at room temperature; gases dissolved in liquids are released under certain circumstances. ==== Plate tectonics ==== On the longest time scales, [[plate tectonics]] will reposition [[continent]]s, shape [[ocean]]s, build and tear down [[mountain]]s and generally serve to define the stage upon which climate exists. During the [[Carboniferous]], tectonics may have triggered the large-scale storage of Carbon and increased glaciation.<ref>{{cite journal|author=Peter Bruckschen, Susanne Oesmanna and Ján Veizer|title=Isotope stratigraphy of the European Carboniferous: proxy signals for ocean chemistry, climate and tectonics| url=http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V5Y-3XNK494-8&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7db7616e9dc94e6ed49a817195926851|journal=Chemical Geology|date=1999-09-30|volume=161|issue=1-3|doi=10.1016/S0009-2541(99)00084-4|pages=127}}</ref> More recently, plate motions have been implicated in the intensification of the present [[ice age]] when, approximately 3 million years ago, the North and South American plates collided to form the [[Isthmus of Panama]] and shut off direct mixing between the [[Atlantic]] and [[Pacific]] Oceans. ==== Solar variation ==== {{main|Solar variation}} [[Image:Solar Activity Proxies.png|right|thumb|250px|Variations in solar activity during the last several centuries based on observations of [[sunspot]]s and [[beryllium]] isotopes.]] The [[sun]] is the ultimate source of essentially all heat in the climate system. The energy output of the sun, which is converted to heat at the Earth's surface, is an integral part of shaping the Earth's climate. On the longest time scales, the sun itself is getting brighter with higher energy output; as it continues its [[main sequence]], this slow change or evolution affects the Earth's atmosphere. It is thought that, early in [[History of Earth|Earth's history]], the sun was too cold to support liquid water at the Earth's surface, leading to what is known as the [[Faint young sun paradox]]. {{Fact|date=December 2007}}. On more modern time scales, there are also a variety of forms of [[solar variation]], including the 11-year [[solar cycle]] and longer-term modulations. However, the 11-year sunspot cycle does not manifest itself clearly in the climatological data. Solar intensity variations are considered to have been influential in triggering the [[Little Ice Age]], and for some of the warming observed from 1900 to 1950. The cyclical nature of the sun's energy output is not yet fully understood; it differs from the very slow change that is happening within the sun as it ages and evolves. {{Fact|date=December 2007}}. ==== Orbital variations ==== In their effect on climate, orbital variations are in some sense an extension of solar variability, because slight variations in the Earth's [[orbit]] lead to changes in the distribution and abundance of sunlight reaching the Earth's surface. Such orbital variations, known as [[Milankovitch cycles]], are a highly predictable consequence of basic physics due to the mutual interactions of the Earth, its moon, and the other planets. These variations are considered the driving factors underlying the glacial and interglacial cycles of the present ice age. Subtler variations are also present, such as the repeated advance and retreat of the [[Sahara]] desert in response to orbital [[precession]]. ==== Volcanism ==== A single [[volcano|eruption]] of the kind that occurs several times per century can affect climate, causing cooling for a period of a few years. For example, the eruption of [[Mount Pinatubo]] in 1991 affected climate substantially. Huge eruptions, known as [[large igneous province]]s, occur only a few times every hundred million years, but can reshape climate for millions of years and cause [[mass extinction]]s. Initially, scientists thought that the dust emitted into the atmosphere from large volcanic eruptions was responsible for the cooling by partially blocking the transmission of [[solar radiation]] to the Earth's surface. However, measurements indicate that most of the dust thrown in the atmosphere returns to the Earth's surface within six months. Volcanoes are also part of the extended [[carbon cycle]]. Over very long (geological) time periods, they release carbon dioxide from the earth's interior, counteracting the uptake by sedimentary rocks and other geological [[carbon dioxide sink]]s. However, this contribution is insignificant compared to the current anthropogenic emissions. The [[US Geological Survey]] estimates that human activities generate more than 130 times the amount of carbon dioxide emitted by volcanoes.<ref>{{cite web|url=http://volcanoes.usgs.gov/Hazards/What/VolGas/volgas.html|title= Volcanic Gases and Their Effects|accessdate=2008-01-21|date=[[2006-01-10]]|publisher= U.S. Department of the Interior}}</ref> [[Image:Climate Change Attribution.png|thumb|left|[[Attribution of recent climate change]]]] === Human influences on climate change === Anthropogenic factors are human activities that change the environment and influence climate. In some cases the chain of causality is direct and unambiguous (e.g., by the effects of irrigation on temperature and humidity), while in others it is less clear. Various hypotheses for human-induced climate change have been debated for many years, though it is important to note that the scientific debate has moved on from scepticism, as there is [[Scientific_opinion_on_climate_change|scientific consensus on climate change]] that human activity is beyond reasonable doubt as the main explanation for the current rapid changes in the world's climate.<ref name=IPCC1>IPCC. (2007) Climate change 2007: the physical science basis (summary for policy makers), IPCC.</ref> Consequently in politics, the debate has largely shifted onto ways to reduce human impact and adapt to change that is already 'in the system.' <ref name=policies> See for example [[emissions trading]], [[cap and share]], [[personal carbon trading]], [[UNFCCC]]</ref> The biggest factor of present concern is the increase in CO<sub>2</sub> levels due to emissions from [[fossil fuel]] combustion, followed by [[particulate|aerosols]] (particulate matter in the atmosphere), which exert a cooling effect, and [[cement]] manufacture. Other factors, including land use, [[ozone depletion]], animal agriculture<ref name="Steinfeld2006">{{cite book | last = Steinfeld | first = H. | coauthors = P. Gerber, T. Wassenaar, V. Castel, M. Rosales, C. de Haan | title = Livestock’s long shadow | date = 2006 | url = http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.htm}}</ref> and deforestation, also affect climate. ==== Fossil fuels ==== [[Image:Carbon Dioxide 400kyr.png|thumb|250px|right|Carbon dioxide variations over the last 400,000 years, showing a rise since the industrial revolution.]] Beginning with the [[industrial revolution]] in the 1850s and accelerating ever since, the [[human]] [[Overconsumption|consumption]] of fossil fuels has elevated CO<sub>2</sub> levels from a concentration of ~280 ppm to ~387 ppm today.<ref>{{cite news | title = World CO2 levels at record high, scientists warn | publisher = [[The Guardian]] | date = [[2008-05-12]] | url = http://www.guardian.co.uk/environment/2008/may/12/climatechange.carbonemissions}}</ref> These increasing concentrations are projected to reach a range of 535 to 983 ppm by the end of the 21st century.<ref>[http://www.epa.gov/climatechange/science/futureac.html | Future Atmosphere Changes in Greenhouse Gas and Aerosol Concentrations]</ref> It is known that carbon dioxide levels are substantially higher now than at any time in the last 750,000 years.<ref>{{cite news | last = Amos | first = Jonathan | title = Deep ice tells long climate story | publisher = [[BBC]] | date = [[2006-09-04]] | url = http://news.bbc.co.uk/2/hi/science/nature/5314592.stm | accessdate = 2008-01-21}}</ref> Along with rising [[methane]] levels, these changes are anticipated to cause an increase of 1.4–5.6 °[[Celsius|C]] between 1990 and 2100 (see [[global warming]]). ==== Aerosols ==== Anthropogenic aerosols, particularly sulphate aerosols from fossil fuel combustion, exert a cooling influence<ref>{{cite journal | last = Charlson | first = R. J. | coauthors = S. E. SCHWARTZ, J. M. HALES, R. D. CESS, J. A. COAKLEY JR., J. E. HANSEN, and D. J. HOFMANN | title = Climate Forcing by Anthropogenic Aerosols | journal = [[Science (journal)|Science]] | volume = 255 | issue = 5043 | pages = 423–430 | date = [[1992-01-24]] | url = http://www.sciencemag.org/cgi/content/abstract/255/5043/423 | doi = 10.1126/science.255.5043.423 | accessdate = 2008-01-28 | pmid = 17842894}}</ref>. This, together with natural variability, is believed to account for the relative "plateau" in the graph of 20th-century temperatures in the middle of the century. ====Cement manufacture==== [[Cement#Climate|Cement manufacture contributes CO<sub>2</sub>]] when [[calcium carbonate]] is heated, producing lime and carbon dioxide, and also as a result of burning [[fossil fuels]]. The cement industry produces 5% of global man-made CO<sub>2</sub> emissions, of which 50% is from the chemical process, and 40% from burning fuel. The amount of CO2 emitted by the cement industry is nearly 900 kg of CO2 for every 1000 kg of cement produced. ==== Land use ==== Prior to widespread fossil fuel use, humanity's largest effect on local climate is likely to have resulted from [[land use]]. [[Irrigation]], [[deforestation]], and [[agriculture]] fundamentally change the environment. For example, they change the amount of water going into and out of a given location. They also may change the local [[albedo]] by influencing the ground cover and altering the amount of sunlight that is absorbed. For example, there is evidence to suggest that the climate of Greece and other Mediterranean countries was permanently changed by widespread deforestation between 700 BC and 1 AD (the wood being used for [[shipbuilding]], [[construction]] and fuel), with the result that the modern climate in the region is significantly hotter and drier, and the species of trees that were used for shipbuilding in the ancient world can no longer be found in the area. An assessment of conterminous U.S. biomass burning speculated that the approximate 8 fold reduction in [[Wildland Fire Emissions]] ([[aerosols]]) from the preindustrial era to present caused by land use changes and land management decisions may have had a regional warming affect if not for fossil fuel burning emission increases occurring concurrently <ref> Leenhouts, B. 1998. Assessment of biomass burning in the conterminous United States. Conservation Ecology [online] 2(1): 1. [http://www.ecologyandsociety.org/vol2/iss1/art1/#Climaticsystemeffects] </ref>. A controversial hypothesis by [[William Ruddiman]] called the [[early anthropocene]] hypothesis<ref>{{cite web | last = Ruddiman | first = William | authorlink = William Ruddiman | title = Debate over the Early Anthropogenic Hypothesis | publisher = [[RealClimate]] | date = [[2005-12-05]] | url = http://www.realclimate.org/index.php/archives/2005/12/early-anthropocene-hyppothesis/ | accessdate = 2008-01-21}}</ref> suggests that the rise of agriculture and the accompanying deforestation led to the increases in carbon dioxide and methane during the period 5000–8000 years ago. These increases, which reversed previous declines, may have been responsible for delaying the onset of the next glacial period, according to Ruddimann's [[overdue-glaciation]] hypothesis. In modern times, a 2007 [[Jet Propulsion Laboratory]] study <ref>[http://www.npr.org/templates/story/story.php?storyId=9242114 California Warming Attributed to Growth] by [[Mandalit del Barco]]. ''[[Day to Day]]'', [[National Public Radio]]. 30 Mar 2007.</ref> found that the average temperature of [[California]] has risen about 2 degrees over the past 50 years, with a much higher increase in urban areas. The change was attributed mostly to extensive human development of the landscape. ==== Livestock ==== According to a 2006 United Nations report, [[Livestock's Long Shadow]], livestock is responsible for 18% of the world’s greenhouse gas emissions as measured in CO<sub>2</sub> equivalents. This however includes land usage change, meaning deforestation in order to create grazing land. In the [[Amazon Rainforest]], 70% of deforestation is to make way for grazing land, so this is the major factor in the 2006 UN [[Food and Agriculture Organization|FAO]] report, which was the first agricultural report to include land usage change into the radiative forcing of livestock. In addition to CO<sub>2</sub> emissions, livestock produces 65% of human-induced [[nitrous oxide]] (which has 296 times the [[global warming potential]] of CO<sub>2</sub>) and 37% of human-induced methane (which has 23 times the global warming potential of CO<sub>2</sub>).<ref name="Steinfeld2006" /> == Interplay of factors == If a certain forcing (for example, solar variation) acts to change the climate, then there may be mechanisms that act to amplify or reduce the effects. These are called [[positive feedback|positive]] and [[negative feedback|negative]] feedbacks. As far as is known, the climate system is generally stable with respect to these feedbacks: positive feedbacks do not "[[feedback runaway|run away]]". Part of the reason for this is the existence of a powerful negative feedback between temperature and emitted radiation: radiation increases as the [[fourth power]] of [[thermodynamic temperature|absolute temperature]]. However, a number of important positive feedbacks do exist. The glacial and interglacial cycles of the present ice age provide an important example. It is believed that orbital variations provide the timing for the growth and retreat of ice sheets. However, the ice sheets themselves reflect sunlight back into space and hence promote cooling and their own growth, known as the ice-albedo feedback. Further, falling sea levels and expanding ice decrease plant growth and indirectly lead to declines in carbon dioxide and methane. This leads to further cooling. Conversely, rising temperatures caused, for example, by anthropogenic emissions of greenhouse gases could lead to decreased snow and ice cover, revealing darker ground underneath, and consequently result in more absorption of sunlight. <ref>{{cite web | last = Ahlenius | first = Hugo | title = Climate feedbacks | publisher = United Nations Environment Programme/GRID-Arendal | date = [[June 2007]] | url = http://maps.grida.no/go/graphic/climate-feedbacks-the-connectivity-of-the-positive-ice-snow-albedo-feedback-terrestrial-snow-and-vegetation-feedbacks-and-the-negative-cloud-radiation-feedback | accessdate = 2008-01-21}}</ref> Water vapor, methane, and carbon dioxide can also act as significant positive feedbacks, their levels rising in response to a warming trend, thereby accelerating that trend. Water vapor acts strictly as a feedback (excepting small amounts in the [[stratosphere]]), unlike the other major greenhouse gases, which can also act as forcings. More complex feedbacks include heat movement from the equatorial regions to the northern latitudes and involve the possibility of altered water currents with in the oceans or air currents with in the atmosphere. A significant concern is that melting glacial ice from [[Greenland]] may interfere and change the thermohaline circulation of water in the North Atlantic, affecting the [[Gulf Stream]] which brings warmer water to replace sinking colder water; which would change the distribution of heat to [[Europe]] and the east coast of the [[United States]]. Other potential feedbacks are not well understood and may either inhibit or promote warming. For example, it is unclear whether rising temperatures promote or inhibit vegetative growth, which could in turn draw down either more or less carbon dioxide. Similarly, increasing temperatures may lead to either more or less [[cloud cover]].<ref>[http://www.grida.no/climate/ipcc_tar/wg1/271.htm Climate Change 2001: The Scientific Basis<!-- Bot generated title -->]</ref> Since on balance cloud cover has a strong cooling effect, any change to the abundance of clouds also affects climate.<ref>For additional discussion of feedbacks relevant to ongoing climate change, see http://www.grida.no/climate/ipcc_tar/wg1/260.htm</ref> == Monitoring the current status of climate == Testing for [[spatial dependence]] between independently measured values in an ordered set is based on applying Fisher’s [[F-test]] to the variance of a set and the first variance term of the ordered set. Charting statistically significant variance terms gives a [[sampling variogram]] that shows where spatial dependence in our sample space of time dissipates into randomness. The lag of a sampling variogram is a statistically robust measure for a change in a climate statistic. Scientists use "Indicator [[time series]]" that represent the many aspects of climate and ecosystem status. The time history provides a historical context. Current status of the climate is also monitored with climate indices.<ref>[http://www.arctic.noaa.gov/detect Arctic Change Indicators]</ref><ref>[http://www.beringclimate.noaa.gov Bering Sea Climate and Ecosystem Indicators]</ref><ref>[http://www.arctic.noaa.gov/essay_bond.html How scientists study climate change]: Some important research concepts used by scientists to study climate variations</ref><ref>{{Citation | editor-last = Baxter | editor-first = JM | editor2-last = Buckley PJ and Wallace CJ | title = Marine Climate Change Impacts Annual Report Card 2007–2008 | year = 2008 | place = Lowestoft | publisher = Marine Climate Change Impacts Partnership | url = http://www.mccip.org.uk/arc/2007/default.htm}}</ref> == Evidence for climatic change == Evidence for climatic change is taken from a variety of sources that can be used to reconstruct past climates. Most of the evidence is indirect—climatic changes are inferred from changes in indicators that reflect climate, such as [[vegetation]], [[dendrochronology]], [[ice core]]s<ref>{{cite journal | last = Petit | first = J. R. | coauthors = J. Jouzel, D. Raynaud, N. I. Barkov, J.-M. Barnola, I. Basile, M. Bender, J. Chappellaz, M. Davis, G. Delaygue, M. Delmotte, V. M. Kotlyakov, M. Legrand, V. Y. Lipenkov, C. Lorius, L. PÉpin, C. Ritz, E. Saltzman and M. Stievenard | title = Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica | journal = [[Nature]] | volume = 399 | pages = 429–436 | date = [[1999-06-03]] | url = http://www.nature.com/nature/journal/v399/n6735/full/399429a0.html | doi = 10.1038/20859 | accessdate = 2008-01-22}}</ref>, [[sea level change]], and [[glacial retreat]]. === Pollen analysis === [[Palynology]] is the science that studies contemporary and fossil [[palynomorph]]s, including [[pollen]]. Palynology is used to infer the geographical distribution of plant species, which vary under different climate conditions. Different groups of plants have [[pollen]] with distinctive shapes and surface textures, and since the outer surface of pollen is composed of a very resilient material, they resist decay. Changes in the type of pollen found in different sedimentation levels in lakes, bogs or river deltas indicate changes in plant communities; which are dependent on climate conditions<ref>{{cite journal | last = Langdon | first = PG | coauthors = Barber KE, Lomas-Clarke SH | title = Reconstructing climate and environmental change in northern England through chironomid and pollen analyses: evidence from Talkin Tarn, Cumbria | journal = Journal of Paleolimnology | volume = 32 | issue = 2 | pages = 197–213 | date = [[August 2004]] | url = http://www.springerlink.com/content/t7m324u675701133/ | doi = 10.1023/B:JOPL.0000029433.85764.a5 | accessdate = 2008-01-28}}</ref><ref>{{cite journal | last = Birks | first = HH | title = The importance of plant macrofossils in the reconstruction of Lateglacial vegetation and climate: examples from Scotland, western Norway, and Minnesota, USA | journal = Quarternary Science Reviews | volume = 22 | issue = 5-7 | pages = 453–473 | date = [[March 2003]] | url = http://www.sciencedirect.com/science/article/B6VBC-47YH3W8-2/2/fde5760538b5b3adb92d8564ea968b9a | doi = 10.1016/S0277-3791(02)00248-2 | accessdate = 2008-01-28}}</ref>. === Beetles === Remains of [[beetle]]s are common in freshwater and land sediments. Different species of beetles tend to be found under different climatic conditions. Knowledge of the present climatic range of the different species, and of the age of the sediments in which remains are found, allows past climatic conditions to be inferred.<ref name=Coope1999>{{cite journal | last = Coope | first = G.R. | coauthors = Lemdahl, G.; Lowe, J.J.; Walkling, A. | title = Temperature gradients in northern Europe during the last glacial--Holocene transition(14--9 14 C kyr BP) interpreted from coleopteran assemblages | journal = [[Journal of Quaternary Science]] | volume = 13 | issue = 5 | pages = 419–433 | publisher = John Wiley & Sons, Ltd. | date = [[1999-05-04]] | url = http://www3.interscience.wiley.com/cgi-bin/abstract/61001707/ABSTRACT | accessdate = 2008-02-18 | doi = 10.1002/(SICI)1099-1417(1998090)13:5<419::AID-JQS410>3.0.CO;2-D}}</ref> ===Glacial geology=== Advancing glaciers leave behind [[moraine]]s and other features that often have datable material in them, recording the time when a glacier advanced and deposited a feature. Similarly, by [[tephrochronology|tephrochronological]] techniques, the lack of glacier cover can be identified by the presence of datable soil or volcanic [[tephra]] horizons. Glaciers are considered one of the most sensitive climate indicators by the [[IPCC]], and their recent observed variations provide a global signal of climate change. See [[Retreat of glaciers since 1850]]. == Examples of climate change == Climate change has continued throughout the entire history of Earth. The field of [[paleoclimatology]] has provided information of climate change in the ancient past, supplementing modern observations of climate. #Climate of the deep past #*[[Faint young sun paradox]] #*[[Snowball earth]] #*[[Oxygen Catastrophe]] #Climate of the last 500 million years #*[[:Image:Phanerozoic Climate Change.png|Phanerozoic overview]] #*[[Paleocene-Eocene Thermal Maximum|Paleocene–Eocene Thermal Maximum]] #*[[Cretaceous Thermal Maximum]] #*[[Permo-Carboniferous Glaciation|Permo–Carboniferous Glaciation]] #*[[Ice age]]s #Climate of recent glaciations #*[[Dansgaard-Oeschger event|Dansgaard–Oeschger event]] #*[[Younger Dryas]] #*[[:Image:Ice Age Temperature.png|Ice age temperatures]] #Recent climate #*[[Holocene Climatic Optimum]] #*[[Medieval Warm Period]] #*[[Little Ice Age]] #*[[Year Without a Summer]] #*[[Temperature record of the past 1000 years]] #*[[Global warming]] #*[[Hardiness Zone Migration]] ==Climate change and agriculture== {{main|Climate change and agriculture}} ==Climate change and biodiversity== The life cycles of many wild plants and animals are closely linked to the passing of the seasons; climatic changes can lead to [[mutualism|interdependent]] pairs of species (e.g. a wild flower and its pollinating insect) losing synchronization, if, for example, one has a cycle dependent on [[day length]] and the other on temperature or precipitation. In principle, at least, this could lead to extinctions or changes in the distribution and abundance of species. One phenomenon is the movement of species northwards in Europe. A recent study by [[Butterfly Conservation]] in the UK<ref>{{cite web | last = Fox | first = R.| coauthors = Warren, M.S., Asher, J., Brereton, T.M. and Roy | title = The state of Britain’s butterflies 2007 | publisher = Butterfly Conservation and the Centre for Ecology and Hydrology, Wareham, Dorset | date = [[2007]] | url = http://www.butterfly-conservation.org/downloads/75/The_State_of_Britain's_Butterflies.html | accessdate = 2008-01-21}}</ref>, has shown that relatively common species with a southerly distribution have moved north, whilst scarce upland species have become rarer and lost territory towards the south. This picture has been mirrored across several invertebrate groups. Drier summers could lead to more periods of drought<ref>{{cite web | last = McGuirk | first = Rod | coauthors = Bernard Lagan, Joseph Kerr | title = Australian Drought | date = [[2007-01-30]] | url = http://www.lilith-ezine.com/articles/environmental/Australian-Drought.html | accessdate = 2008-01-21}}</ref>, potentially affecting many species of animal and plant. For example, in the UK during the drought year of 2006 significant numbers of trees died or showed [[dieback]] on light sandy soils. In Australia, since the early 90s, tens of thousands of flying foxes ([[Pteropus]]) have died as a direct result of extreme heat<ref>{{cite journal | last = Welbergen| first = J. A. | coauthors = Klose, S. M., Markus, N. & Eby, P. | title = Climate change and the effects of temperature extremes on Australian flying-foxes | journal = Proceedings of the Royal Society B | volume = 275 | issue = 1633 | pages = 419–425 | publisher = Royal Society Publishing | date = [[2008-02-22]] | url = http://journals.royalsociety.org/content/2682344508637641/| doi = 10.1098/rspb.2007.1385 | accessdate = 2008-01-21}}</ref>. Wetter, milder winters might affect temperate mammals or insects by preventing them [[hibernation|hibernating]] or entering [[torpor]] during periods when food is scarce. One predicted change is the ascendancy of 'weedy' or opportunistic species at the expense of scarcer species with narrower or more specialized ecological requirements. One example could be the expanses of [[bluebells|bluebell]] seen in many woodlands in the UK. These have an early growing and flowering season before competing weeds can develop and the [[canopy (forest)|tree canopy]] closes. Milder winters can allow weeds to overwinter as adult plants or germinate sooner, whilst trees leaf earlier, reducing the length of the window for bluebells to complete their life cycle. Organisations such as [[Wildlife Trusts|Wildlife Trust]], [[World Wide Fund for Nature]], [[Birdlife International]] and the [[Audubon Society]] are actively monitoring and research the effects of climate change on biodiversity and advance policies in areas such as [[landscape scale conservation]] to promote [[adaptation]] to climate change<ref>{{cite web | title = Biodiversity and climate change | work = United Nations Environment Programme | publisher = [[World Conservation Monitoring Centre|UNEP-WCMC]] | url = http://www.unep-wcmc.org/climate/home.htm | accessdate = 2008-01-28}}</ref>. == See also == {{Wikinewscat|Climate change}} {{Portal|Environment}} {{EnergyPortal}} * [[Glossary of climate change]] * [[List of climate change topics]] ==Notes== *Emanuel, K. A. (2005) ''Increasing destructiveness of tropical cyclones over the past 30 years.'', ''Nature'', '''436'''; 686-688 {{PDFlink|ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdf}} *IPCC. (2007) ''Climate change 2007: the physical science basis (summary for policy makers)'', IPCC. *Miller, C. and Edwards, P. N. (ed.)(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 *Ruddiman, W. F., Vavrus, S. J. and Kutzbach, J. E. (2005) ''A test of the overdue-glaciation hypothesis'', ''Quaternary Science Review'', '''24''':11 *Schmidt, G. A., Shindel, D. T. and Harder, S. (2004) ''A note of the relationship between ice core methane concentrations and insolation'' GRL v31 L23206 == References== {{reflist|2}} {{global warming}} [[Category:Climate change| ]] [[Category:Climate change feedbacks and causes]] [[Category:History of climate]] [[Category:Global warming| ]] [[Category:Carbon finance]] [[Category:Climate and weather statistics]] {{Link FA|es}} [[bg:Изменение на климата]] [[ca:Canvi climàtic]] [[da:Klimaændring]] [[de:Klimaveränderung]] [[et:Kliimamuutus]] [[es:Cambio climático]] [[eo:Klimata ŝanĝo]] [[eu:Klima aldaketa]] [[fa:تغییرات آب و هوا]] [[fr:Changement climatique]] [[ga:Athrú aeráide]] [[gl:Cambio climático]] [[ko:기후 변화]] [[it:Mutamento climatico]] [[hu:Klímaváltozás]] [[ms:Perubahan iklim]] [[nl:Klimaatverandering]] [[ja:気候変動]] [[no:Klimaendring]] [[nn:Klimaendring]] [[oc:Cambiament climatic]] [[pl:Zmiana klimatu]] [[pt:Mudança do clima]] [[ru:Изменение климата]] [[sq:Ndryshimi i klimës]] [[simple:Climate change]] [[sk:Klimatické zmeny]] [[sl:Spremembe podnebja]] [[sh:Promjena klime]] [[fi:Ilmastonmuutos]] [[sv:Klimatförändring]] [[uk:Зміна клімату]]