Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorological variables that are commonly measured are temperature, humidity, atmospheric pressure, wind, and precipitation. In a broader sense, climate is the state of the components of the climate system, including the atmosphere, hydrosphere, cryosphere, lithosphere and biosphere and the interactions between them. The climate of a location is affected by its latitude, longitude, terrain, altitude, land use and nearby water bodies and their currents.
Wood is a structural tissue found in the stems and roots of trees and other woody plants. It is an organic material – a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or more broadly to include the same type of tissue elsewhere, such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, woodchips, or fiber.
Dendrochronology is the scientific method of dating tree rings to the exact year they were formed in a tree. As well as dating them, this can give data for dendroclimatology, the study of climate and atmospheric conditions during different periods in history from the wood of old trees. Dendrochronology derives from the Ancient Greek dendron, meaning "tree", khronos, meaning "time", and -logia, "the study of".
Paleoclimatology is the scientific study of climates predating the invention of meteorological instruments, when no direct measurement data were available. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important to understand natural variation and the evolution of the current climate.
Climatology or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. Climate concerns the atmospheric condition during an extended to indefinite period of time; weather is the condition of the atmosphere during a relative brief period of time. The main topics of research are the study of climate variability, mechanisms of climate changes and modern climate change. This topic of study is regarded as part of the atmospheric sciences and a subdivision of physical geography, which is one of the Earth sciences. Climatology includes some aspects of oceanography and biogeochemistry.
The temperature record of the last 2,000 years is reconstructed using data from climate proxy records in conjunction with the modern instrumental temperature record which only covers the last 170 years at a global scale. Large-scale reconstructions covering part or all of the 1st millennium and 2nd millennium have shown that recent temperatures are exceptional: the Intergovernmental Panel on Climate Change Fourth Assessment Report of 2007 concluded that "Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1,300 years." The curve shown in graphs of these reconstructions is widely known as the hockey stick graph because of the sharp increase in temperatures during the last century. As of 2010 this broad pattern was supported by more than two dozen reconstructions, using various statistical methods and combinations of proxy records, with variations in how flat the pre-20th-century "shaft" appears. Sparseness of proxy records results in considerable uncertainty for earlier periods.
Quantitative research is a research strategy that focuses on quantifying the collection and analysis of data. It is formed from a deductive approach where emphasis is placed on the testing of theory, shaped by empiricist and positivist philosophies.
A speleothem is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on their depositional history and environment. Their chemical composition, gradual growth, and preservation in caves make them useful paleoclimatic proxies.
The tree line is the edge of a habitat at which trees are capable of growing and beyond which they are not. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions. The tree line is sometimes distinguished from a lower timberline, which is the line below which trees form a forest with a closed canopy.
In the study of past climates ("paleoclimatology"), climate proxies are preserved physical characteristics of the past that stand in for direct meteorological measurements and enable scientists to reconstruct the climatic conditions over a longer fraction of the Earth's history. Reliable global records of climate only began in the 1880s, and proxies provide the only means for scientists to determine climatic patterns before record-keeping began.
The global temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. There are numerous estimates of temperatures since the end of the Pleistocene glaciation, particularly during the current Holocene epoch. Some temperature information is available through geologic evidence, going back millions of years. More recently, information from ice cores covers the period from 800,000 years before the present time until now. A study of the paleoclimate covers the time period from 12,000 years ago to the present. Tree rings and measurements from ice cores can give evidence about the global temperature from 1,000-2,000 years before the present until now. The most detailed information exists since 1850, when methodical thermometer-based records began. Modifications on the Stevenson-type screen were made for uniform instrument measurements around 1880.
Dendroarchaeology is a term used for the study of vegetation remains, old buildings, artifacts, furniture, art and musical instruments using the techniques of dendrochronology. It refers to dendrochronological research of wood from the past regardless of its current physical context. This form of dating is the most accurate and precise absolute dating method available to archaeologists, as the last ring that grew is the first year the tree could have been incorporated into an archaeological structure.
A paleothermometer is a methodology that provides an estimate of the ambient temperature at the time of formation of a natural material. Most paleothermometers are based on empirically-calibrated proxy relationships, such as the tree ring or TEX86 methods. Isotope methods, such as the δ18O method or the clumped-isotope method, are able to provide, at least in theory, direct measurements of temperature.
In geochemistry, paleoclimatology and paleoceanography δ18O or delta-O-18 is a measure of the deviation in ratio of stable isotopes oxygen-18 (18O) and oxygen-16 (16O). It is commonly used as a measure of the temperature of precipitation, as a measure of groundwater/mineral interactions, and as an indicator of processes that show isotopic fractionation, like methanogenesis. In paleosciences, 18O:16O data from corals, foraminifera and ice cores are used as a proxy for temperature.
Hockey stick graphs present the global or hemispherical mean temperature record of the past 500 to 2000 years as shown by quantitative climate reconstructions based on climate proxy records. These reconstructions have consistently shown a slow long term cooling trend changing into relatively rapid warming in the 20th century, with the instrumental temperature record by 2000 exceeding earlier temperatures.
Sclerochronology is the study of periodic physical and chemical features in the hard tissues of animals that grow by accretion, including invertebrates and coralline red algae, and the temporal context in which they formed. It is particularly useful in the study of marine paleoclimatology. The term was coined in 1974 following pioneering work on nuclear test atolls by Knutson and Buddemeier and comes from the three Greek words skleros (hard), chronos (time) and logos (science), which together refer to the use of the hard parts of living organisms to order events in time. It is, therefore, a form of stratigraphy. Sclerochronology focuses primarily upon growth patterns reflecting annual, monthly, fortnightly, tidal, daily, and sub-daily (ultradian) increments of time.
The divergence problem is an anomaly from the field of dendroclimatology, the study of past climate through observations of old trees, primarily the properties of their annual growth rings. It is the disagreement between instrumental temperatures and the temperatures reconstructed from latewood densities or, in some cases, from the widths of tree rings in far northern forests.
The International Tree-Ring Data Bank (ITRDB) is a data repository for tree ring measurements that has been maintained since 1990 by the United States' National Oceanic and Atmospheric Administration Paleoclimatology Program and World Data Center for Paleoclimatology. The ITRDB was initially established by Hal Fritts through the Laboratory of Tree-Ring Research at the University of Arizona, with a grant from the US National Science Foundation, following the First International Workshop on Dendrochronology in 1974. The ITRDB accepts all tree ring data with sufficient metadata to be uploaded, but its founding focus was on tree ring measurements intended for climatic studies.
Paleohydrology, or palaeohydrology, is the scientific study of the movement, distribution, and quality of water on Earth during previous periods of its history. The discipline uses indirect evidence to infer changes in deposition rates, the existence of flooding, changes in sea levels, changes in groundwater levels and the erosion of rocks. It also deals with alterations in the floral and faunal assemblages which have come about in previous periods because of changes in hydrology.
Rosanne D'Arrigo is a professor at Lamont–Doherty Earth Observatory at Columbia University known for her research into climate change using dendrochronology, or dating based on tree rings.
