Misplaced Pages

#377622

80-600: The main methods employed by climatologists are the analysis of observations and modelling of the physical processes that determine climate. Short term weather forecasting can be interpreted in terms of knowledge of longer-term phenomena of climate, for instance climatic cycles such as the El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation (MJO), the North Atlantic oscillation (NAO),

160-497: A greenhouse ), partially controlled (e.g. FACE [Free Airborne Concentration Enhancement] experiments—add ref), or where conditions in nature are monitored. In any case, the important thing is that multiple growth factors are carefully recorded to determine what impacts growth. (Insert Fennoscandanavia paper reference ). With this information, ring width response can be more accurately understood and inferences from historic (unmonitored) tree rings become more certain. In concept, this

240-413: A common software infrastructure shared by all U.S. climate researchers, and holding an annual climate modeling forum, the report found. Cloud-resolving climate models are nowadays run on high intensity super-computers which have a high power consumption and thus cause CO 2 emissions.  They require exascale computing (billion billion – i.e., a quintillion – calculations per second). For example,

320-419: A day; the ocean is MOM-3 ( Modular Ocean Model ) with a 3.75° × 3.75° grid and 24 vertical levels. Box models are simplified versions of complex systems, reducing them to boxes (or reservoirs ) linked by fluxes. The boxes are assumed to be mixed homogeneously. Within a given box, the concentration of any chemical species is therefore uniform. However, the abundance of a species within a given box may vary as

400-560: A double-edged sword. Along with the advantages of dendroclimatology are some limitations: confounding factors , geographic coverage, annular resolution, and collection difficulties. The field has developed various methods to partially adjust for these challenges. There are multiple climate and non-climate factors as well as nonlinear effects that impact tree ring width. Methods to isolate single factors (of interest) include botanical studies to calibrate growth influences and sampling of "limiting stands" (those expected to respond mostly to

480-607: A dry-climate area unsuitable at that time for the growth of bamboo. The invention of thermometers and barometers during the Scientific Revolution allowed for systematic recordkeeping, that began as early as 1640–1642 in England. Early climate researchers include Edmund Halley , who published a map of the trade winds in 1686 after a voyage to the southern hemisphere. Benjamin Franklin (1706–1790) first mapped

560-411: A few decades to as long as millions of years. The climate system receives nearly all of its energy from the sun. The climate system also gives off energy to outer space . The balance of incoming and outgoing energy, and the passage of the energy through the climate system, determines Earth's energy budget . When the incoming energy is greater than the outgoing energy, earth's energy budget is positive and

640-405: A function of elevation (i.e. relative humidity distribution). This has been shown by refining the zero dimension model in the vertical to a one-dimensional radiative-convective model which considers two processes of energy transport: Radiative-convective models have advantages over simpler models and also lay a foundation for more complex models. They can estimate both surface temperature and

720-573: A function of time due to the input to (or loss from) the box or due to the production, consumption or decay of this species within the box. Simple box models, i.e. box model with a small number of boxes whose properties (e.g. their volume) do not change with time, are often useful to derive analytical formulas describing the dynamics and steady-state abundance of a species. More complex box models are usually solved using numerical techniques. Box models are used extensively to model environmental systems or ecosystems and in studies of ocean circulation and

800-483: A generalized, overall description of the atmosphere or ocean which can be used to characterize the factors which effect the global climate system. El Niño–Southern Oscillation (ENSO) is a coupled ocean-atmosphere phenomenon in the Pacific Ocean responsible for much of the global variability of temperature, and has a cycle between two and seven years. The North Atlantic oscillation is a mode of variability that

880-411: A global network of thermometers , to prehistoric ice extracted from glaciers . As measuring technology changes over time, records of data often cannot be compared directly. As cities are generally warmer than the areas surrounding, urbanization has made it necessary to constantly correct data for this urban heat island effect. Climate models use quantitative methods to simulate the interactions of

SECTION 10

#1732791295378

960-425: A hand-held borer device, that requires skill to get a good sample. The best samples come from felling a tree and sectioning it. However, this requires more danger and does damage to the forest. It may not be allowed in certain areas, particularly with the oldest trees in undisturbed sites (which are the most interesting scientifically). As with all experimentalists, dendroclimatologists must, at times, decide to make

1040-430: A linear dependence of ring width on the variable of interest (e.g. moisture). However, if the variable changes enough, response may level off or even turn opposite. The home gardener knows that one can underwater or overwater a house plant. In addition, it is possible that interaction effects may occur (for example "temperature times precipitation" may affect growth as well as temperature and precipitation on their own. Also,

1120-565: A robust and unambiguous picture of significant climate warming in response to increasing greenhouse gases." The World Climate Research Programme (WCRP), hosted by the World Meteorological Organization (WMO), coordinates research activities on climate modelling worldwide. A 2012 U.S. National Research Council report discussed how the large and diverse U.S. climate modeling enterprise could evolve to become more unified. Efficiencies could be gained by developing

1200-463: A substantial warming trend, tree rings from these particular sites do not display a corresponding change in their maximum latewood density or, in some cases, their width. This does not apply to all such studies. Where this applies, a temperature trend extracted from tree rings alone would not show any substantial warming. The temperature graphs calculated from instrumental temperatures and from these tree ring proxies thus "diverge" from one another since

1280-407: A year. Another major variable of climate is continentality: the distance to major water bodies such as oceans . Oceans act as a moderating factor, so that land close to it has typically less difference of temperature between winter and summer than areas further from it. The atmosphere interacts with other parts of the climate system , with winds generating ocean currents that transport heat around

1360-413: Is where The constant parameters include The constant π r 2 {\displaystyle \pi \,r^{2}} can be factored out, giving a nildimensional equation for the equilibrium where The remaining variable parameters which are specific to the planet include This very simple model is quite instructive. For example, it shows the temperature sensitivity to changes in

1440-682: Is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamic terms for various energy sources ( radiation , latent heat ). These equations are the basis for computer programs used to simulate the Earth's atmosphere or oceans. Atmospheric and oceanic GCMs (AGCM and OGCM ) are key components along with sea ice and land-surface components. GCMs and global climate models are used for weather forecasting , understanding

1520-542: Is considerable confidence that climate models provide credible quantitative estimates of future climate change, particularly at continental scales and above. This confidence comes from the foundation of the models in accepted physical principles and from their ability to reproduce observed features of current climate and past climate changes. Confidence in model estimates is higher for some climate variables (e.g., temperature) than for others (e.g., precipitation). Over several decades of development, models have consistently provided

1600-402: Is continuing research into explanations and ways to reconcile this the discrepancy between analysis of tree ring data and thermometer based data. Trees do not cover the Earth. Polar and marine climates cannot be estimated from tree rings. In perhumid tropical regions, Australia and southern Africa , trees generally grow all year round and don't show clear annual rings. In some forest areas,

1680-770: Is in excess). Conversely, lower elevation treelines are expected to be more affected by precipitation changes than temperature variation. This is not a perfect work-around as multiple factors still impact trees even at the "limiting stand," but it helps. In theory, collection of samples from nearby limiting stands of different types (e.g. upper and lower treelines on the same mountain) should allow mathematical solution for multiple climate factors . Non-climate factors include soil, tree age, fire, tree-to-tree competition, genetic differences, logging or other human disturbance, herbivore impact (particularly sheep grazing), pest outbreaks, disease, and CO 2 concentration. For factors which vary randomly over space (tree to tree or stand to stand),

SECTION 20

#1732791295378

1760-461: Is like the limiting stand principle, but it is more quantitative—like a calibration. The divergence problem is the disagreement between the temperatures measured by the thermometers (instrumental temperatures) on one side, and the temperatures reconstructed from the latewood density or width of tree rings on the other side, at many treeline sites in northern forests . While the rendering and analysis of data from thermometer records largely suggest

1840-575: Is mainly contained to the lower atmosphere, the troposphere . The layer of atmosphere above, the stratosphere is also capable of creating its own variability, most importantly the Madden–Julian oscillation (MJO), which has a cycle of approximately 30 to 60 days. The Interdecadal Pacific oscillation can create changes in the Pacific Ocean and lower atmosphere on decadal time scales. Climate change occurs when changes of Earth's climate system result in new weather patterns that remain for an extended period of time. This duration of time can be as brief as

1920-470: Is sometimes modeled as a stochastic process but this is generally accepted as an approximation to processes that are otherwise too complicated to analyze. The collection of a long record of climate variables is essential for the study of climate. Climatology deals with the aggregate data that meteorologists have recorded. Scientists use both direct and indirect observations of the climate, from Earth observing satellites and scientific instrumentation such as

2000-490: Is sometimes termed hydroclimatology, in particular when studying the effects of climate change on the water cycle. The study of contemporary climates incorporates meteorological data accumulated over many years, such as records of rainfall, temperature and atmospheric composition. Knowledge of the atmosphere and its dynamics is also embodied in models , either statistical or mathematical , which help by integrating different observations and testing how well they match. Modeling

2080-400: Is still useful in that the laws of physics are applicable in a bulk fashion to unknown objects, or in an appropriate lumped manner if some major properties of the object are known. For example, astronomers know that most planets in our own solar system feature some kind of solid/liquid surface surrounded by a gaseous atmosphere. A very simple model of the radiative equilibrium of the Earth

2160-434: Is the study of climate as related to human history and is thus concerned mainly with the last few thousand years. Boundary-layer climatology concerns exchanges in water, energy and momentum near surfaces. Further identified subtopics are physical climatology, dynamic climatology, tornado climatology , regional climatology, bioclimatology , and synoptic climatology. The study of the hydrological cycle over long time scales

2240-441: Is used for understanding past, present and potential future climates. Climate research is made difficult by the large scale, long time periods, and complex processes which govern climate. Climate is governed by physical principles which can be expressed as differential equations . These equations are coupled and nonlinear, so that approximate solutions are obtained by using numerical methods to create global climate models . Climate

2320-400: Is used to represent the fluctuations of stock prices in general, climate indices are used to represent the essential elements of climate. Climate indices are generally devised with the twin objectives of simplicity and completeness, and each index typically represents the status and timing of the climate factor it represents. By their very nature, indices are simple, and combine many details into

2400-658: The Arctic oscillation (AO), the Pacific decadal oscillation (PDO), and the Interdecadal Pacific Oscillation (IPO). Climate models are used for a variety of purposes from studying the dynamics of the weather and climate system to predictions of future climate. The Greeks began the formal study of climate; in fact, the word "climate" is derived from the Greek word klima , meaning "slope", referring to

2480-549: The Frontier exascale supercomputer consumes 29 MW. It can simulate a year’s worth of climate at cloud resolving scales in a day. Techniques that could lead to energy savings, include for example: "reducing floating point precision computation; developing machine learning algorithms to avoid unnecessary computations; and creating a new generation of scalable numerical algorithms that would enable higher throughput in terms of simulated years per wall clock day." Climate models on

Climatology - Misplaced Pages Continue

2560-566: The Köppen climate classification , was developed during the late nineteenth century and is based on vegetation. It uses monthly data concerning temperature and precipitation . There are different types of variability: recurring patterns of temperature or other climate variables. They are quantified with different indices. Much in the way the Dow Jones Industrial Average , which is based on the stock prices of 30 companies,

2640-595: The NOAA Geophysical Fluid Dynamics Laboratory AOGCMs represent the pinnacle of complexity in climate models and internalise as many processes as possible. However, they are still under development and uncertainties remain. They may be coupled to models of other processes, such as the carbon cycle , so as to better model feedback effects. Such integrated multi-system models are sometimes referred to as either "earth system models" or "global climate models." Simulation of

2720-542: The carbon cycle . They are instances of a multi-compartment model . In 1961 Henry Stommel was the first to use a simple 2-box model to study factors that influence ocean circulation. In 1956, Norman Phillips developed a mathematical model that realistically depicted monthly and seasonal patterns in the troposphere. This was the first successful climate model. Several groups then began working to create general circulation models . The first general circulation climate model combined oceanic and atmospheric processes and

2800-407: The climate , and forecasting climate change . Atmospheric GCMs (AGCMs) model the atmosphere and impose sea surface temperatures as boundary conditions. Coupled atmosphere-ocean GCMs (AOGCMs, e.g. HadCM3 , EdGCM , GFDL CM2.X , ARPEGE-Climat) combine the two models. The first general circulation climate model that combined both oceanic and atmospheric processes was developed in the late 1960s at

2880-481: The climate system , such as the widespread melt of glaciers , sea level rise and shifts of flora and fauna. In contrast to meteorology , which emphasises short term weather systems lasting no more than a few weeks, climatology studies the frequency and trends of those systems. It studies the periodicity of weather events over years to millennia, as well as changes of long-term average weather patterns in relation to atmospheric conditions. Climatologists study both

2960-530: The "limiting stand" helps somewhat to isolate the variable of interest. For instance, at the upper treeline, where the tree is "cold limited", it's unlikely that nonlinear effects of high temperature ("inverted quadratic") will have a numerically significant impact on ring width over the course of a growing season. Botanical studies can help to estimate the impact of confounding variables and in some cases guide corrections for them. These experiments may be either ones where growth variables are all controlled (e.g. in

3040-428: The 1950s, which is the origin of the term. This divergence raises obvious questions of whether other, unrecognized divergences have occurred in the past, prior to the era of thermometers. There is evidence suggesting that the divergence is caused by human activities, and so confined to the recent past, but use of affected proxies can lead to overestimation of past temperatures, understating the current warming trend. There

3120-422: The Earth's land surface areas). Topics that climatologists study comprise three main categories: climate variability , mechanisms of climatic change, and modern changes of climate. Various factors affect the average state of the atmosphere at a particular location. For instance, midlatitudes will have a pronounced seasonal cycle of temperature whereas tropical regions show little variation of temperature over

3200-698: The Earth. Any unbalance results in a change of the average temperature of the Earth. Most climate models include the radiative effects of greenhouse gases such as carbon dioxide . These models predict a trend of increase of surface temperatures , as well as a more rapid increase of temperature at higher latitudes. Models can range from relatively simple to complex: Additionally, they are available with different resolutions ranging from >100 km to 1 km. High resolutions in global climate models are computational very demanding and only few global datasets exists. Examples are ICON or mechanistically downscaled data such as CHELSA (Climatologies at high resolution for

3280-566: The Sun is in the form of short wave electromagnetic radiation , chiefly visible and short-wave (near) infrared . The outgoing energy is in the form of long wave (far) infrared electromagnetic energy. These processes are part of the greenhouse effect . Climate models vary in complexity. For example, a simple radiant heat transfer model treats the Earth as a single point and averages outgoing energy. This can be expanded vertically (radiative-convective models) and horizontally. More complex models are

Climatology - Misplaced Pages Continue

3360-479: The annual growth of the tree leaves other traces. In particular maximum latewood density (MXD) is another metric used for estimating environmental variables. It is, however, harder to measure. Other properties (e.g. isotope or chemical trace analysis) have also been tried most notably by L. M. Libby in her 1974 paper "Temperature Dependence of Isotope Ratios in Tree Rings". In theory, multiple measurements on

3440-498: The atmosphere in the late 19th century. Other EBMs similarly seek an economical description of surface temperatures by applying the conservation of energy constraint to individual columns of the Earth-atmosphere system. Essential features of EBMs include their relative conceptual simplicity and their ability to sometimes produce analytical solutions . Some models account for effects of ocean, land, or ice features on

3520-400: The atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the weather and climate system to projections of future climate. All climate models balance, or very nearly balance, incoming energy as short wave (including visible) electromagnetic radiation to the Earth with outgoing energy as long wave (infrared) electromagnetic radiation from

3600-504: The basic laws of physics , fluid motion , and chemistry . Scientists divide the planet into a 3-dimensional grid and apply the basic equations to those grids. Atmospheric models calculate winds , heat transfer , radiation , relative humidity , and surface hydrology within each grid and evaluate interactions with neighboring points. These are coupled with oceanic models to simulate climate variability and change that occurs on different timescales due to shifting ocean currents and

3680-452: The best of imperfect data, rather than resample. This tradeoff is made more difficult, because sample collection (in the field) and analysis (in the lab) may be separated significantly in time and space. These collection challenges mean that data gathering is not as simple or cheap as conventional laboratory science. Initial work focused on measuring the tree ring width—this is simple to measure and can be related to climate parameters. But

3760-488: The best solution is to collect sufficient data (more samples) to compensate for confounding noise. Tree age is corrected for with various statistical methods: either fitting spline curves to the overall tree record or using similar aged trees for comparison over different periods (regional curve standardization). Careful examination and site selection helps to limit some confounding effects, for example picking sites undisturbed by modern man. In general, climatologists assume

3840-413: The climate system in full 3-D space and time was impractical prior to the establishment of large computational facilities starting in the 1960s. In order to begin to understand which factors may have changed Earth's paleoclimate states, the constituent and dimensional complexities of the system needed to be reduced. A simple quantitative model that balanced incoming/outgoing energy was first developed for

3920-551: The climate system is warming. If more energy goes out, the energy budget is negative and earth experiences cooling. Climate change also influences the average sea level . Modern climate change is caused largely by the human emissions of greenhouse gas from the burning of fossil fuel which increases global mean surface temperatures . Increasing temperature is only one aspect of modern climate change, which also includes observed changes of precipitation , storm tracks and cloudiness. Warmer temperatures are causing further changes of

4000-465: The coupled atmosphere–ocean– sea ice global climate models . These types of models solve the full equations for mass transfer, energy transfer and radiant exchange. In addition, other types of models can be interlinked. For example Earth System Models include also land use as well as land use changes . This allows researchers to predict the interactions between climate and ecosystems . Climate models are systems of differential equations based on

4080-525: The course of the Gulf Stream for use in sending mail from North America to Europe. Francis Galton (1822–1911) invented the term anticyclone . Helmut Landsberg (1906–1985) fostered the use of statistical analysis in climatology. During the early 20th century, climatology mostly emphasized the description of regional climates. This descriptive climatology was mainly an applied science, giving farmers and other interested people statistics about what

SECTION 50

#1732791295378

4160-481: The decades that followed, and while the history of climate change science started earlier, climate change only became one of the main topics of study for climatologists during the 1970s and afterward. Various subtopics of climatology study different aspects of climate. There are different categorizations of the sub-topics of climatology. The American Meteorological Society for instance identifies descriptive climatology, scientific climatology and applied climatology as

4240-416: The dynamics of the climate system and to make projections of future climate and of climate change . Climate models can also be qualitative (i.e. not numerical) models and contain narratives, largely descriptive, of possible futures. Climate models take account of incoming energy from the Sun as well as outgoing energy from Earth. An imbalance results in a change in temperature . The incoming energy from

4320-423: The effect of ice-albedo feedback on global climate sensitivity has been investigated using a one-dimensional radiative-convective climate model. The zero-dimensional model may be expanded to consider the energy transported horizontally in the atmosphere. This kind of model may well be zonally averaged. This model has the advantage of allowing a rational dependence of local albedo and emissivity on temperature –

4400-479: The future. Some refer to this type of forecasting as pattern recognition, which remains a useful method of estimating rainfall over data voids such as oceans using knowledge of how satellite imagery relates to precipitation rates over land, as well as the forecasting of precipitation amounts and distribution of the future. A variation of this theme, used for medium range forecasting, is known as teleconnections , when systems in other locations are used to help determine

4480-560: The globe. Classification is an important method of simplifying complicated processes. Different climate classifications have been developed over the centuries, with the first ones in Ancient Greece . How climates are classified depends on what the application is. A wind energy producer will require different information (wind) in a classification than someone more interested in agriculture, for whom precipitation and temperature are more important. The most widely used classification,

4560-451: The instrumental record. Then one is justified in extending the dendroclimatology inferences to areas where no suitable tree ring samples are obtainable. Tree rings show the impact on growth over an entire growing season. Climate changes deep in the dormant season (winter) will not be recorded. In addition, different times of the growing season may be more important than others (i.e. May versus September) for ring width. However, in general

4640-445: The location of a system within the regime surrounding. One method of using teleconnections are by using climate indices such as ENSO-related phenomena. Climate model Numerical climate models (or climate system models ) are mathematical models that can simulate the interactions of important drivers of climate . These drivers are the atmosphere , oceans , land surface and ice . Scientists use climate models to study

4720-412: The much larger heat storage capacity of the global ocean. External drivers of change may also be applied. Including an ice-sheet model better accounts for long term effects such as sea level rise . There are three major types of institution where climate models are developed, implemented and used: Big climate models are essential but they are not perfect. Attention still needs to be given to

4800-406: The nature of climates – local, regional or global – and the natural or human-induced factors that cause climates to change. Climatology considers the past and can help predict future climate change . Phenomena of climatological interest include the atmospheric boundary layer , circulation patterns , heat transfer ( radiative , convective and latent ), interactions between the atmosphere and

4880-518: The nature of questions asked and the pertinent time scales, there are, on the one extreme, conceptual, more inductive models, and, on the other extreme, general circulation models operating at the highest spatial and temporal resolution currently feasible. Models of intermediate complexity bridge the gap. One example is the Climber-3 model. Its atmosphere is a 2.5-dimensional statistical-dynamical model with 7.5° × 22.5° resolution and time step of half

SECTION 60

#1732791295378

4960-411: The normal weather was and how great chances were of extreme events. To do this, climatologists had to define a climate normal , or an average of weather and weather extremes over a period of typically 30 years. While scientists knew of past climate change such as the ice ages , the concept of climate as changing only very gradually was useful for descriptive climatology. This started to change during

5040-403: The oceans and land surface (particularly vegetation, land use and topography ), and the chemical and physical composition of the atmosphere. A relative difficult method of forecast, the analog technique requires remembering a previous weather event which is expected to be mimicked by an upcoming event. What makes it a difficult technique is that there is rarely a perfect analog for an event of

5120-531: The planet's surface, have an average emissivity of about 0.5 (which must be reduced by the fourth power of the ratio of cloud absolute temperature to average surface absolute temperature) and an average cloud temperature of about 258 K (−15 °C; 5 °F). Taking all this properly into account results in an effective earth emissivity of about 0.64 (earth average temperature 285 K (12 °C; 53 °F)). Dimensionless models have also been constructed with functionally separated atmospheric layers from

5200-520: The poles can be allowed to be icy and the equator warm – but the lack of true dynamics means that horizontal transports have to be specified. Early examples include research of Mikhail Budyko and William D. Sellers who worked on the Budyko-Sellers model . This work also showed the role of positive feedback in the climate system and has been considered foundational for the energy balance models since its publication in 1969. Depending on

5280-461: The radiative heat transfer processes which underlie the greenhouse effect. Quantification of this phenomenon using a version of the one-layer model was first published by Svante Arrhenius in year 1896. Water vapor is a main determinant of the emissivity of Earth's atmosphere. It both influences the flows of radiation and is influenced by convective flows of heat in a manner that is consistent with its equilibrium concentration and temperature as

5360-437: The real world (what is happening and why). The global models are essential to assimilate all the observations, especially from space (satellites) and produce comprehensive analyses of what is happening, and then they can be used to make predictions/projections. Simple models have a role to play that is widely abused and fails to recognize the simplifications such as not including a water cycle. A general circulation model (GCM)

5440-646: The ring width is used to infer the overall climate change during the corresponding year (an approximation). Another problem is "memory" or autocorrelation . A stressed tree may take a year or two to recover from a hard season. This problem can be dealt with by more complex modeling (a "lag" term in the regression) or by reducing the skill estimates of chronologies. Tree rings must be obtained from nature, frequently from remote regions. This means that special efforts are needed to map sites properly. In addition, samples must be collected in difficult (often sloping terrain) conditions. Generally, tree rings are collected using

5520-503: The rings from sample to sample. This allows extension backwards in time using deceased tree samples, even using samples from buildings or from archeological digs. Another advantage of tree rings is that they are clearly demarked in annual increments, as opposed to other proxy methods such as boreholes . Furthermore, tree rings respond to multiple climatic effects (temperature, moisture, cloudiness), so that various aspects of climate (not just temperature) can be studied. However, this can be

5600-668: The slope or inclination of the Earth's axis. Arguably the most influential classic text concerning climate was On Airs, Water and Places written by Hippocrates about 400 BCE . This work commented on the effect of climate on human health and cultural differences between Asia and Europe. This idea that climate controls which populations excel depending on their climate, or climatic determinism , remained influential throughout history. Chinese scientist Shen Kuo (1031–1095) inferred that climates naturally shifted over an enormous span of time, after observing petrified bamboos found underground near Yanzhou (modern Yan'an , Shaanxi province),

5680-506: The solar constant, Earth albedo, or effective Earth emissivity. The effective emissivity also gauges the strength of the atmospheric greenhouse effect , since it is the ratio of the thermal emissions escaping to space versus those emanating from the surface. The calculated emissivity can be compared to available data. Terrestrial surface emissivities are all in the range of 0.96 to 0.99 (except for some small desert areas which may be as low as 0.7). Clouds, however, which cover about half of

5760-494: The surface budget. Others include interactions with parts of the water cycle or carbon cycle . A variety of these and other reduced system models can be useful for specialized tasks that supplement GCMs, particularly to bridge gaps between simulation and understanding. Zero-dimensional models consider Earth as a point in space, analogous to the pale blue dot viewed by Voyager 1 or an astronomer's view of very distant objects. This dimensionless view while highly limited

5840-595: The surface. The simplest of these is the zero-dimensional, one-layer model , which may be readily extended to an arbitrary number of atmospheric layers. The surface and atmospheric layer(s) are each characterized by a corresponding temperature and emissivity value, but no thickness. Applying radiative equilibrium (i.e conservation of energy) at the interfaces between layers produces a set of coupled equations which are solvable. Layered models produce temperatures that better estimate those observed for Earth's surface and atmospheric levels. They likewise further illustrate

5920-440: The temperature variation with elevation in a more realistic manner. They also simulate the observed decline in upper atmospheric temperature and rise in surface temperature when trace amounts of other non-condensible greenhouse gases such as carbon dioxide are included. Other parameters are sometimes included to simulate localized effects in other dimensions and to address the factors that move energy about Earth. For example,

6000-509: The three subcategories of climatology, a categorization based on the complexity and the purpose of the research. Applied climatologists apply their expertise to different industries such as manufacturing and agriculture . Paleoclimatology is the attempt to reconstruct and understand past climates by examining records such as ice cores and tree rings ( dendroclimatology ). Paleotempestology uses these same records to help determine hurricane frequency over millennia. Historical climatology

6080-421: The tree growth is too much influenced by multiple factors (no "limiting stand") to allow clear climate reconstruction . The coverage difficulty is dealt with by acknowledging it and by using other proxies (e.g. ice cores, corals) in difficult areas. In some cases it can be shown that the parameter of interest (temperature, precipitation, etc.) varies similarly from area to area, for example by looking at patterns in

6160-404: The variable of interest). Climate factors that affect trees include temperature, precipitation, sunlight, and wind. To differentiate among these factors, scientists collect information from "limiting stands." An example of a limiting stand is the upper elevation treeline: here, trees are expected to be more affected by temperature variation (which is "limited") than precipitation variation (which

6240-781: The web: Dendroclimatology Dendroclimatology is the science of determining past climates from trees (primarily properties of the annual tree rings ). Tree rings are wider when conditions favor growth, narrower when times are difficult. Other properties of the annual rings, such as maximum latewood density (MXD) have been shown to be better proxies than simple ring width. Using tree rings, scientists have estimated many local climates for hundreds to thousands of years previous. By combining multiple tree-ring studies (sometimes with other climate proxy records), scientists have estimated past regional and global climates. Tree rings are especially useful as climate proxies in that they can be well-dated via dendrochronology , i.e. matching of

6320-568: Was developed in the late 1960s at the Geophysical Fluid Dynamics Laboratory , a component of the U.S. National Oceanic and Atmospheric Administration . By 1975, Manabe and Wetherald had developed a three-dimensional global climate model that gave a roughly accurate representation of the current climate. Doubling CO 2 in the model's atmosphere gave a roughly 2 °C rise in global temperature. Several other kinds of computer models gave similar results: it

6400-520: Was impossible to make a model that gave something resembling the actual climate and not have the temperature rise when the CO 2 concentration was increased. The Coupled Model Intercomparison Project (CMIP) has been a leading effort to foster improvements in GCMs and climate change understanding since 1995. The IPCC stated in 2010 it has increased confidence in forecasts coming from climate models: "There

#377622