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92-509: Its software design assumes a physical/dynamical component of the climate system and, as a freely available community model, is designed to work on a variety of machine architectures powerful enough to run the model. The CESM codebase is mostly public domain with some segregable components issued under open source and other licenses. The offline chemical transport model has been described as "very efficient". The model includes four submodels (land, sea-ice, ocean and atmosphere) connected by

184-582: A 256×128 regular longitude/latitude global horizontal grid (giving a 1.4 degree resolution). It has 26 levels in the vertical. The polar component of ocean-atmosphere coupling includes sea ice geophysics using the formerly-known Los Alamos Sea Ice Model, CICE , now often referred to as the CICE Consortium model, to which NCAR has contributed code and physical improvements through the Polar Climate Working Group. CICE simulates

276-462: A barrier to winds and impact where and how much it rains. Land closer to open ocean has a more moderate climate than land farther from the ocean. For the purpose of modelling the climate , the land is often considered static as it changes very slowly compared to the other elements that make up the climate system. The position of the continents determines the geometry of the oceans and therefore influences patterns of ocean circulation. The locations of

368-405: A correlation between weather and sunspot activity, mostly without notable success. Later research has concentrated more on correlating solar activity with global temperature. Accurate measurement of solar forcing is crucial to understanding possible solar impact on terrestrial climate. Accurate measurements only became available during the satellite era, starting in the late 1970s, and even that

460-428: A coupler that exchanges information with the submodels. NCAR suggested that because of this, CCSM cannot be considered a single climate model, but rather a framework for building and testing various climate models. The Climatological Data Ocean Model (docn) is recently at version   6.0. It must be run within the framework of CCSM rather than standalone. It takes two netCDF datasets as input and sends six outputs to

552-601: A decrease in other wavelengths." In the modern era, the Sun has operated within a sufficiently narrow band that climate has been little affected. Models indicate that the combination of solar variations and volcanic activity can explain periods of relative warmth and cold between A.D. 1000 and 1900. Numerous paleoenvironmental reconstructions have looked for relationships between solar variability and climate. Arctic paleoclimate, in particular, has linked total solar irradiance variations and climate variability. A 2001 paper identified

644-425: A higher density and differences in density play an important role in ocean circulation . The thermohaline circulation transports heat from the tropics to the polar regions. Ocean circulation is further driven by the interaction with wind. The salt component also influences the freezing point temperature . Vertical movements can bring up colder water to the surface in a process called upwelling , which cools down

736-503: A higher layer of the atmosphere directly, the stratosphere , which may have an effect on the atmosphere near the surface. Slight variations in the Earth's motion can cause large changes in the seasonal distribution of sunlight reaching the Earth's surface and how it is distributed across the globe, although not to the global and yearly average sunlight. The three types of kinematic change are variations in Earth's eccentricity , changes in

828-510: A human activity, such as the combustion of biomass or fossil fuels, releases aerosols into the atmosphere. Aerosols counteract some of the warming effects of emitted greenhouse gases until they fall back to the surface in a few years or less. Although volcanoes are technically part of the lithosphere, which is part of the climate system, volcanism is defined as an external forcing agent. On average, there are only several volcanic eruptions per century that influence Earth's climate for longer than

920-421: A main driver of climate change over the millions to billions of years of the geologic time scale . Evidence that this is the case comes from analysis on many timescales and from many sources, including: direct observations; composites from baskets of different proxy observations; and numerical climate models. On millennial timescales, paleoclimate indicators have been compared to cosmogenic isotope abundances as

1012-511: A measure of known solar-terrestrial interaction, Love et al. found a statistically significant correlation between sunspots and geomagnetic activity, but not between global surface temperature and either sunspot number or geomagnetic activity. Benestad and Schmidt concluded that "the most likely contribution from solar forcing a global warming is 7 ± 1% for the 20th century and is negligible for warming since 1980." This paper disagreed with Scafetta and West, who claimed that solar variability has

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1104-403: A part of the radiation of the Sun and it emits infra-red radiation as black-body radiation . The balance of incoming and outgoing energy, and the passage of the energy through the climate system, determines Earth's energy budget . When the total of incoming energy is greater than the outgoing energy, Earth's Energy Imbalance is positive and the climate system is warming. If more energy goes out,

1196-510: A possible cosmic-ray effect on clouds and climate." After further investigation, the team concluded that "variations in cosmic ray intensity do not appreciably affect climate through nucleation." 1983–1994 global low cloud formation data from the International Satellite Cloud Climatology Project (ISCCP) was highly correlated with galactic cosmic ray (GCR) flux; subsequent to this period,

1288-423: A significant effect on climate forcing. Based on correlations between specific climate and solar forcing reconstructions, they argued that a "realistic climate scenario is the one described by a large preindustrial secular variability ( e.g. , the paleoclimate temperature reconstruction by Moberg et al.) with TSI experiencing low secular variability (as the one shown by Wang et al.). Under this scenario, they claimed

1380-528: A significant solar contribution to recent warming, although still smaller (between 16 and 36%) than that of greenhouse gases. A study in 2004 concluded that solar activity affects the climate - based on sunspot activity, yet plays only a small role in the current global warming. In 1991, Friis-Christensen and Lassen claimed a strong correlation of the length of the solar cycle with northern hemispheric temperature changes. They initially used sunspot and temperature measurements from 1861 to 1989 and later extended

1472-475: A solid crust , eventually allowing liquid water to exist on the surface. Three to four billion years ago the Sun emitted only 70% of its current power. Under the present atmospheric composition, this past solar luminosity would have been insufficient to prevent water from uniformly freezing. There is nonetheless evidence that liquid water was already present in the Hadean and Archean eons, leading to what

1564-428: A temperature decrease on Earth, which would then allow ice and snow cover to expand. The extra snow and ice has a higher albedo or reflectivity, and therefore reflects more of the Sun's radiation back into space before it can be absorbed by the climate system as a whole; this in turn causes the Earth to cool down further. Solar activity and climate Patterns of solar irradiance and solar variation have been

1656-427: A unified code release that included CCSM4 as the code base for its atmospheric component. Climate system Earth's climate system is a complex system with five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). Climate is the statistical characterization of

1748-431: A year by ejecting tons of SO 2 into the stratosphere . The sulfur dioxide is chemically converted into aerosols that cause cooling by blocking a fraction of sunlight to the Earth's surface. Small eruptions affect the atmosphere only subtly. Changes in land cover, such as change of water cover (e.g. rising sea level , drying up of lakes and outburst floods ) or deforestation , particularly through human use of

1840-513: A ~1500 year solar cycle that was a significant influence on North Atlantic climate throughout the Holocene. One historical long-term correlation between solar activity and climate change is the 1645–1715 Maunder minimum , a period of little or no sunspot activity which partially overlapped the " Little Ice Age " during which cold weather prevailed in Europe. The Little Ice Age encompassed roughly

1932-449: Is considered to be some combination of direct forcing by TSI changes and indirect effects of ultraviolet (UV) radiation on the stratosphere. Least certain are indirect effects induced by galactic cosmic rays. In 2002, Lean et al. stated that while "There is ... growing empirical evidence for the Sun's role in climate change on multiple time scales including the 11-year cycle", "changes in terrestrial proxies of solar activity (such as

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2024-503: Is in the system and where it goes. When the Earth's energy budget changes, the climate follows. A change in the energy budget is called a forcing. When the change is caused by something outside of the five components of the climate system, it is called an external forcing . Volcanoes, for example, result from deep processes within the earth that are not considered part of the climate system. Human actions, off-planet changes, such as solar variation and incoming asteroids, are also external to

2116-429: Is known as the faint young Sun paradox . Hypothesized solutions to this paradox include a vastly different atmosphere, with much higher concentrations of greenhouse gases than currently exist. Over the following approximately 4 billion years, the Sun's energy output increased and the composition of the Earth atmosphere changed. The Great Oxygenation Event around 2.4 billion years ago was the most notable alteration of

2208-637: Is more land in the Northern Hemisphere compared to the Southern Hemisphere , a larger part of that hemisphere is covered in snow. Both hemispheres have about the same amount of sea ice. Most frozen water is contained in the ice sheets on Greenland and Antarctica , which average about 2 kilometres (1.2 miles) in height. These ice sheets slowly flow towards their margins. The Earth's crust , specifically mountains and valleys, shapes global wind patterns: vast mountain ranges form

2300-447: Is much larger than the heat held by the atmosphere. It contains seawater with a salt content of about 3.5% on average, but this varies spatially. Brackish water is found in estuaries and some lakes, and most freshwater , 2.5% of all water, is held in ice and snow. The cryosphere contains all parts of the climate system where water is solid. This includes sea ice , ice sheets , permafrost and snow cover . Because there

2392-470: Is open to some residual disputes: different teams find different values, due to different methods of cross-calibrating measurements taken by instruments with different spectral sensitivity. Scafetta and Willson argue for significant variations of solar luminosity between 1980 and 2000, but Lockwood and Frohlich find that solar forcing declined after 1987. The 2001 Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report (TAR) concluded that

2484-548: Is reduced by a factor of 5 when the background component is omitted from historical reconstructions of total solar irradiance ...This suggests that general circulation model (GCM) simulations of twentieth century warming may overestimate the role of solar irradiance variability." A 2006 review suggested that solar brightness had relatively little effect on global climate, with little likelihood of significant shifts in solar output over long periods of time. Lockwood and Fröhlich, 2007, found "considerable evidence for solar influence on

2576-449: Is the movement of water through the climate system. Not only does the hydrological cycle determine patterns of precipitation , it also has an influence on the movement of energy throughout the climate system. The hydrosphere proper contains all the liquid water on Earth, with most of it contained in the world's oceans. The ocean covers 71% of Earth's surface to an average depth of nearly 4 kilometres (2.5 miles), and ocean heat content

2668-489: Is the opposite of the expected warming if solar energy (falling primarily or wholly during daylight, depending on energy regime) were the principal means of forcing. It is, however, the expected pattern if greenhouse gases were preventing radiative escape, which is more prevalent at night. The Northern Hemisphere is warming faster than the Southern Hemisphere. This is the opposite of the expected pattern if

2760-414: Is then taken up by its roots. Without vegetation, this water would have run off to the closest rivers or other water bodies. Water taken up by plants instead evaporates, contributing to the hydrological cycle. Precipitation and temperature influences the distribution of different vegetation zones. Carbon assimilation from seawater by the growth of small phytoplankton is almost as much as land plants from

2852-467: The Maunder minimum is far too simplistic as, although solar variations may have played a minor role, a much bigger factor is known to be Little Ice Age volcanism . In recent decades observations of unprecedented accuracy, sensitivity and scope (of both solar activity and terrestrial climate) have become available from spacecraft and show unequivocally that recent global warming is not caused by changes in

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2944-580: The Pacific decadal oscillation , and the Atlantic Multidecadal Oscillation . These variations can affect global average surface temperature by redistributing heat between the deep ocean and the atmosphere; but also by altering the cloud, water vapour or sea ice distribution, which can affect the total energy budget of the earth. The oceanic aspects of these oscillations can generate variability on centennial timescales due to

3036-448: The 14C and 10Be cosmogenic isotopes and the aa geomagnetic index) can occur in the absence of long-term (i.e., secular) solar irradiance changes ... because the stochastic response increases with the cycle amplitude, not because there is an actual secular irradiance change." They conclude that because of this, "long-term climate change may appear to track the amplitude of the solar activity cycles," but that "Solar radiative forcing of climate

3128-498: The 16th to the 19th centuries. Whether the low solar activity or other factors caused the cooling is debated. The Spörer Minimum between 1460 and 1550 was matched to a significant cooling period. A 2012 paper instead linked the Little Ice Age to volcanism, through an "unusual 50-year-long episode with four large sulfur-rich explosive eruptions," and claimed "large changes in solar irradiance are not required" to explain

3220-415: The 1960s, as indicated by solar cycles 19–24, in which the maximum number of sunspots were 201, 111, 165, 159, 121 and 82, respectively. In the three decades following 1978, the combination of solar and volcanic activity is estimated to have had a slight cooling influence. A 2010 study found that the composition of solar radiation might have changed slightly, with in an increase of ultraviolet radiation and

3312-427: The 20th century. They predicted that continued greenhouse gas emissions would cause additional future temperature increases "at a rate similar to that observed in recent decades". In addition, the study notes "uncertainties in historical forcing" — in other words, past natural forcing may still be having a delayed warming effect, most likely due to the oceans. Stott's 2003 work largely revised his assessment, and found

3404-428: The Earth's pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century", but that "over the past 20 years, all the trends in the Sun that could have had an influence on the Earth's climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures." In a study that considered geomagnetic activity as

3496-656: The Sun might have contributed 50% of the observed global warming since 1900. Stott et al. estimated that the residual effects of the prolonged high solar activity during the last 30 years account for between 16% and 36% of warming from 1950 to 1999. Neither direct measurements nor proxies of solar variation correlate well with Earth global temperature, particularly in recent decades when both quantities are best known. The oppositely-directed trends highlighted by Lockwood and Fröhlich in 2007, with global mean temperatures continuing to rise while solar activity fell, have continued and become even more pronounced since then. In 2007

3588-757: The Sun, currently closer to the Earth during austral summer , were the principal climate forcing. In particular, the Southern Hemisphere, with more ocean area and less land area, has a lower albedo ("whiteness") and absorbs more light. The Northern Hemisphere, however, has higher population, industry and emissions. Furthermore, the Arctic region is warming faster than the Antarctic and faster than northern mid-latitudes and subtropics, despite polar regions receiving less sun than lower latitudes. Solar forcing should warm Earth's atmosphere roughly evenly by altitude, with some variation by wavelength/energy regime. However,

3680-407: The Sun. Earth formed around 4.54 billion years ago by accretion from the solar nebula . Volcanic outgassing probably created the primordial atmosphere, which contained almost no oxygen and would have been toxic to humans and most modern life. Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism. Over time, the planet cooled and formed

3772-570: The US and northern Europe and milder winters in Canada and southern Europe, with little change in global averages. More broadly, links have been suggested between solar cycles, global climate and regional events such as El Niño . Hancock and Yarger found "statistically significant relationships between the double [~21-year] sunspot cycle and the 'January thaw' phenomenon along the East Coast and between

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3864-408: The air above. The hydrological cycle or water cycle describes how it is constantly moved between the surface of the Earth and the atmosphere. Plants evapotranspirate and sunlight evaporates water from oceans and other water bodies, leaving behind salt and other minerals. The evaporated freshwater later rains back onto the surface. Precipitation and evaporation are not evenly distributed across

3956-565: The air to the right in the Northern Hemisphere and to the left in the Southern hemisphere, thus forming distinct atmospheric cells. Monsoons , seasonal changes in wind and precipitation that occur mostly in the tropics, form due to the fact that land masses heat up more easily than the ocean. The temperature difference induces a pressure difference between land and ocean, driving a steady wind. Ocean water that has more salt has

4048-427: The analysis over a specific time period, along with other arbitrarities in their methodology. Solar activity may also impact regional climates, such as for the rivers Paraná and Po . Measurements from NASA's Solar Radiation and Climate Experiment show that solar UV output is more variable than total solar irradiance. Climate modelling suggests that low solar activity may result in, for example, colder winters in

4140-571: The atmosphere is warming at lower altitudes while cooling higher up. This is the expected pattern if greenhouse gases drive temperature, as on Venus . A 1994 study of the US National Research Council concluded that TSI variations were the most likely cause of significant climate change in the pre-industrial era, before significant human-generated carbon dioxide entered the atmosphere. Scafetta and West correlated solar proxy data and lower tropospheric temperature for

4232-500: The atmosphere, mainly being emitted by people burning fossil fuels , is causing climate change . Human activity also releases cooling aerosols , but their net effect is far less than that of greenhouse gases. Changes can be amplified by feedback processes in the different climate system components. The atmosphere envelops the earth and extends hundreds of kilometres from the surface. It consists mostly of inert nitrogen (78%), oxygen (21%) and argon (0.9%). Some trace gases in

4324-449: The atmosphere, such as water vapour and carbon dioxide , are the gases most important for the workings of the climate system, as they are greenhouse gases which allow visible light from the Sun to penetrate to the surface, but block some of the infrared radiation the Earth's surface emits to balance the Sun's radiation. This causes surface temperatures to rise. The hydrological cycle

4416-487: The atmosphere. Liquid and solid particles in the atmosphere, collectively named aerosols , have diverse effects on the climate. Some primarily scatter sunlight, cooling the planet, while others absorb sunlight and warm the atmosphere. Indirect effects include the fact that aerosols can act as cloud condensation nuclei , stimulating cloud formation. Natural sources of aerosols include sea spray , mineral dust , meteorites and volcanoes . Still, humans also contribute as

4508-485: The atmosphere. While humans are technically part of the biosphere , they are often treated as a separate components of Earth's climate system, the anthroposphere , because of human's large impact on the planet. The climate system receives energy from the Sun, and to a far lesser extent from the Earth's core, as well as tidal energy from the Moon. The Earth gives off energy to outer space in two forms: it directly reflects

4600-449: The atmosphere. Over the next five billion years, the Sun's ultimate death as it becomes a very bright red giant and then a very faint white dwarf will have dramatic effects on climate , with the red giant phase likely already ending any life on Earth. Since 1978, solar irradiance has been directly measured by satellites with very good accuracy. These measurements indicate that the Sun's total solar irradiance fluctuates by +-0.1% over

4692-442: The carbon back to the lithosphere. The nitrogen cycle describes the flow of active nitrogen. As atmospheric nitrogen is inert, micro-organisms first have to convert this to an active nitrogen compound in a process called fixing nitrogen , before it can be used as a building block in the biosphere. Human activities play an important role in both carbon and nitrogen cycles: the burning of fossil fuels has displaced carbon from

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4784-538: The cause of increasing concentrations of some greenhouse gases, such as CO 2 , methane and N 2 O . The dominant contributor to the greenhouse effect is water vapour (~50%), with clouds (~25%) and CO 2 (~20%) also playing an important role. When concentrations of long-lived greenhouse gases such as CO 2 are increased, temperature and water vapour increase. Accordingly, water vapour and clouds are not seen as external forcings but as feedback. The weathering of carbonates and silicates removes carbon from

4876-607: The climate system vary continuously, even without external pushes (external forcing). One example in the atmosphere is the North Atlantic Oscillation (NAO), which operates as an atmospheric pressure see-saw. The Portuguese Azores typically have high pressure, whereas there is often lower pressure over Iceland . The difference in pressure oscillates and this affects weather patterns across the North Atlantic region up to central Eurasia . For instance,

4968-465: The climate system's five components. The primary value to quantify and compare climate forcings is radiative forcing . The Sun is the predominant source of energy input to the Earth and drives atmospheric circulation. The amount of energy coming from the Sun varies on shorter time scales, including the 11-year solar cycle and longer-term time scales. While the solar cycle is too small to directly warm and cool Earth's surface, it does influence

5060-438: The climate system. It represents the average weather , typically over a period of 30 years, and is determined by a combination of processes, such as ocean currents and wind patterns. Circulation in the atmosphere and oceans transports heat from the tropical regions to regions that receive less energy from the Sun. Solar radiation is the main driving force for this circulation. The water cycle also moves energy throughout

5152-461: The climate system. In addition, certain chemical elements are constantly moving between the components of the climate system. Two examples for these biochemical cycles are the carbon and nitrogen cycles . The climate system can change due to internal variability and external forcings . These external forcings can be natural, such as variations in solar intensity and volcanic eruptions, or caused by humans. Accumulation of greenhouse gases in

5244-435: The components is the speed at which they react to a forcing. The atmosphere typically responds within a couple of hours to weeks, while the deep ocean and ice sheets take centuries to millennia to reach a new equilibrium. The initial response of a component to an external forcing can be damped by negative feedbacks and enhanced by positive feedbacks . For example, a significant decrease of solar intensity would quickly lead to

5336-693: The correlation broke down. Changes of 3–4% in cloudiness and concurrent changes in cloud top temperatures correlated to the 11 and 22-year solar (sunspot) cycles, with increased GCR levels during "antiparallel" cycles. Global average cloud cover change was measured at 1.5–2%. Several GCR and cloud cover studies found positive correlation at latitudes greater than 50° and negative correlation at lower latitudes. However, not all scientists accept this correlation as statistically significant, and some who do attribute it to other solar variability ( e.g. UV or total irradiance variations) rather than directly to GCR changes. Difficulties in interpreting such correlations include

5428-487: The coupler, to be integrated with the output of the other submodels. The Community Atmosphere Model (CAM) can also be run as a standalone atmosphere model. Its most current version is 3.1, while 3.0 was the fifth generation. On May 17, 2002, its name was changed from the NCAR Community Climate Model to reflect its role in the new system. It shares the same horizontal grid as the land model of CCSM:

5520-634: The cycle, maybe storminess in New England would. Respected scientists and enthusiastic amateurs insisted they had found patterns reliable enough to make predictions. Sooner or later though every prediction failed. An example was a highly credible forecast of a dry spell in Africa during the sunspot minimum of the early 1930s. When the period turned out to be wet, a meteorologist later recalled "the subject of sunspots and weather relationships fell into dispute, especially among British meteorologists who witnessed

5612-468: The difference in the trends was apparent after about 1987 and that difference has grown and accelerated in subsequent years. The updated figure (right) shows the variations and contrasts solar cycles 14 and 24, a century apart, that are quite similar in all solar activity measures (in fact cycle 24 is slightly less active than cycle 14 on average), yet the global mean air surface temperature is more than 1 degree Celsius higher for cycle 24 than cycle 14, showing

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5704-400: The different components of the climate system. The carbon cycle is directly important for climate as it determines the concentrations of two important greenhouse gases in the atmosphere: CO 2 and methane . In the fast part of the carbon cycle, plants take up carbon dioxide from the atmosphere using photosynthesis ; this is later re-emitted by the breathing of living creatures. As part of

5796-501: The double sunspot cycle and 'drought' (June temperature and precipitation) in the Midwest." Recent research at CERN's CLOUD facility examined links between cosmic rays and cloud condensation nuclei, demonstrating the effect of high-energy particulate radiation in nucleating aerosol particles that are precursors to cloud condensation nuclei. Kirkby (CLOUD team leader) said, "At the moment, it [the experiment] actually says nothing about

5888-403: The energy imbalance is negative and Earth experiences cooling. More energy reaches the tropics than the polar regions and the subsequent temperature difference drives the global circulation of the atmosphere and oceans . Air rises when it warms, flows polewards and sinks again when it cools, returning to the equator. Due to the conservation of angular momentum , the Earth's rotation diverts

5980-617: The fact that many aspects of solar variability change at similar times, and some climate systems have delayed responses. Physicist and historian Spencer R. Weart in The Discovery of Global Warming (2003) wrote: The study of [sun spot] cycles was generally popular through the first half of the century. Governments had collected a lot of weather data to play with and inevitably people found correlations between sun spot cycles and select weather patterns. If rainfall in England didn't fit

6072-401: The globe, with some regions such as the tropics having more rainfall than evaporation, and others having more evaporation than rainfall. The evaporation of water requires substantial quantities of energy, whereas a lot of heat is released during condensation. This latent heat is the primary source of energy in the atmosphere. Chemical elements, vital for life, are constantly cycled through

6164-627: The growth, movement, deformation and melt of sea ice , critical for calculating energy and mass fluxes between the polar atmosphere and oceans in the earth system . The first version of CCSM was created in 1983 as the Community Climate Model (CCM). Over the next two decades it was steadily improved and was renamed CCSM after the Climate System Model (CSM) components were introduced in May 1996. In June 2004 NCAR released

6256-492: The land, can affect the climate. The reflectivity of the area can change, causing the region to capture more or less sunlight. In addition, vegetation interacts with the hydrological cycle, so precipitation is also affected. Landscape fires release greenhouse gases into the atmosphere and release black carbon , which darkens snow, making it easier to melt. The different elements of the climate system respond to external forcing in different ways. One important difference between

6348-484: The late-20th century warming. Some studies associate solar cycle-driven irradiation increases with part of twentieth century warming . Three mechanisms are proposed by which solar activity affects climate: Climate models have been unable to reproduce the rapid warming observed in recent decades when they only consider variations in total solar irradiance and volcanic activity. Hegerl et al. (2007) concluded that greenhouse gas forcing had "very likely" caused most of

6440-482: The latter are a proxy for solar activity. These have also been used on century times scales but, in addition, instrumental data are increasingly available (mainly telescopic observations of sunspots and thermometer measurements of air temperature) and show that, for example, the temperature fluctuations do not match the solar activity variations and that the commonly-invoked association of the Little Ice Age with

6532-405: The lithosphere to the atmosphere, and the use of fertilizers has vastly increased the amount of available fixed nitrogen. Climate is constantly varying, on timescales that range from seasons to the lifetime of the Earth. Changes caused by the system's own components and dynamics are called internal climate variability . The system can also experience external forcing from phenomena outside of

6624-493: The measured impact of recent solar variation is much smaller than the amplification effect due to greenhouse gases , but acknowledged that scientific understanding is poor with respect to solar variation. Estimates of long-term solar irradiance changes have decreased since the TAR. However, empirical results of detectable tropospheric changes have strengthened the evidence for solar forcing of climate change. The most likely mechanism

6716-400: The most comprehensive model simulations of 20th century climate to that date. Their study looked at both "natural forcing agents" (solar variations and volcanic emissions) as well as "anthropogenic forcing" (greenhouse gases and sulphate aerosols). They found that "solar effects may have contributed significantly to the warming in the first half of the century although this result is dependent on

6808-424: The observed global warming since the mid-20th century. In making this conclusion, they allowed for the possibility that climate models had been underestimating the effect of solar forcing. Another line of evidence comes from looking at how temperatures at different levels in the Earth's atmosphere have changed. Models and observations show that greenhouse gas results in warming of the troposphere , but cooling of

6900-435: The ocean having hundreds of times more mass than the atmosphere , and therefore very high thermal inertia. For example, alterations to ocean processes such as thermohaline circulation play a key role in redistributing heat in the world's oceans. Understanding internal variability helped scientists to attribute recent climate change to greenhouse gases. On long timescales, the climate is determined mainly by how much energy

6992-465: The period using four centuries of climate records. Their reported relationship appeared to account for nearly 80 per cent of measured temperature changes over this period. The mechanism behind these claimed correlations was a matter of speculation. In a 2003 paper Laut identified problems with some of these correlation analyses. Damon and Laut claimed: the apparent strong correlations displayed on these graphs have been obtained by incorrect handling of

7084-457: The phenomenon. A 2010 paper suggested that a new 90-year period of low solar activity would reduce global average temperatures by about 0.3 °C, which would be far from enough to offset the increased forcing from greenhouse gases. The link between recent solar activity and climate has been quantified and is not a major driver of the warming that has occurred since early in the twentieth century. Human-induced forcings are needed to reproduce

7176-423: The physical data. The graphs are still widely referred to in the literature, and their misleading character has not yet been generally recognized. Damon and Laut stated that when the graphs are corrected for filtering errors, the sensational agreement with the recent global warming, which drew worldwide attention, totally disappeared. In 2000, Lassen and Thejll updated their 1991 research and concluded that while

7268-583: The preindustrial era, before significant anthropogenic greenhouse forcing, suggesting that TSI variations may have contributed 50% of the warming observed between 1900 and 2000 (although they conclude "our estimates about the solar effect on climate might be overestimated and should be considered as an upper limit.") If interpreted as a detection rather than an upper limit, this would contrast with global climate models predicting that solar forcing of climate through direct radiative forcing makes an insignificant contribution. In 2000, Stott and others reported on

7360-435: The reconstruction of total solar irradiance that is used. In the latter half of the century, we find that anthropogenic increases in greenhouses gases are largely responsible for the observed warming, balanced by some cooling due to anthropogenic sulphate aerosols, with no evidence for significant solar effects." Stott's group found that combining these factors enabled them to closely simulate global temperature changes throughout

7452-554: The rise is not associated with solar activity. The total solar irradiance (TSI) panel shows the PMOD composite of observations with a modelled variation from the SATIRE-T2 model of the effect of sunspots and faculae with the addition of a quiet -Sun variation (due to sub-resolution photospheric features and any solar radius changes) derived from correlations with comic ray fluxes and cosmogenic isotopes. The finding that solar activity

7544-400: The seas are important in controlling the transfer of heat and moisture across the globe, and therefore, in determining global climate. Lastly, the biosphere also interacts with the rest of the climate system. Vegetation is often darker or lighter than the soil beneath, so that more or less of the Sun's heat gets trapped in areas with vegetation. Vegetation is good at trapping water, which

7636-406: The slow carbon cycle, volcanoes release CO 2 by degassing, releasing carbon dioxide from the Earth's crust and mantle. As CO 2 in the atmosphere makes rain a bit acidic , this rain can slowly dissolve some rocks, a process known as weathering . The minerals that are released in this way, transported to the sea, are used by living creatures whose remains can form sedimentary rocks , bringing

7728-418: The solar cycle accounted for about half the temperature rise since 1900, it failed to explain a rise of 0.4 °C since 1980. Benestad's 2005 review found that the solar cycle did not follow Earth's global mean surface temperature. In 2022, Chatzistergos updated the cycle length series with recent sunspot and solar plages data, extending them to more recent periods than previous studies, and also considering

7820-499: The stratosphere. Depletion of the ozone layer by chemical refrigerants stimulated a stratospheric cooling effect. If the Sun was responsible for observed warming, warming of the troposphere at the surface and warming at the top of the stratosphere would be expected as the increased solar activity would replenish ozone and oxides of nitrogen. The assessment of the solar activity/climate relationship involves multiple, independent lines of evidence. Early research attempted to find

7912-486: The system (e.g. a change in Earth's orbit). Longer changes, usually defined as changes that persist for at least 30 years, are referred to as climate changes , although this phrase usually refers to the current global climate change . When the climate changes, the effects may build on each other, cascading through the other parts of the system in a series of climate feedbacks (e.g. albedo changes ), producing many different effects (e.g. sea level rise ). Components of

8004-570: The third version, which included new versions of all of the submodels. In 2007 this new version (commonly given the acronym CCSM3 or NCCCSM) was used in the IPCC Fourth Assessment Report , alongside many others. In May 2010 NCAR released CCSM version   4 (CCSM4). On June 25, 2010 NCAR released the successor to CCSM, called the Community Earth System Model (CESM), version   1.0 (CESM1), as

8096-458: The tilt angle of Earth's axis of rotation , and precession of Earth's axis. Together these produce Milankovitch cycles , which affect climate and are notable for their correlation to glacial and interglacial periods . Greenhouse gases trap heat in the lower part of the atmosphere by absorbing longwave radiation. In the Earth's past, many processes contributed to variations in greenhouse gas concentrations. Currently, emissions by humans are

8188-442: The various available time series. This is important because of the plentiful updates and corrections that have been applied to the sunspot data over the last decade. He showed that cycle lengths significantly diverge from Earth's temperatures and concluded that the strong correlation reported by Friis-Christensen and Lassen was an artefact of their analysis. Owing largely to their guess of next extrema times, arbitrarily restricting

8280-530: The weather in Greenland and Canada is cold and dry during a positive NAO. Different phases of the North Atlantic oscillation can be sustained for multiple decades. The ocean and atmosphere can also work together to spontaneously generate internal climate variability that can persist for years to decades at a time. Examples of this type of variability include the El Niño–Southern Oscillation ,

8372-418: The ~11 years of the solar cycle , but that its average value has been stable since the measurements started in 1978. Solar irradiance before the 1970s is estimated using proxy variables , such as tree rings , the number of sunspots , and the abundances of cosmogenic isotopes such as Be , all of which are calibrated to the post-1978 direct measurements. Solar activity has been on a declining trend since

8464-529: Was approximately the same in cycles 14 and 24 applies to all solar outputs that have, in the past, been proposed as a potential cause of terrestrial climate change and includes total solar irradiance, cosmic ray fluxes, spectral UV irradiance, solar wind speed and/or density, heliospheric magnetic field and its distribution of orientations and the consequent level of geomagnetic activity. Global average diurnal temperature range has decreased. Daytime temperatures have not risen as fast as nighttime temperatures. This

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