The process by which radiation transfers to matter some or all of its energy.

The upper layer of permafrost that thaws in the summertime. It is known as the active layer since it is in this layer that soil processes, like the growth of plants, can occur. It generally thaws to a depth of 20-150 cm (depending on latitude) and usually refreezes in the winter.

A collection of airborne solid or liquid particles, with a typical size between 0.01 and 10 µm, that reside in the atmosphere for at least several hours. Aerosols may be of either natural or anthropogenic origin. They can both directly and indirectly influence climate (see "aerosol effect").

A climate feedback involving changes in earth's albedo. In a warming climate, Earth's overall albedo is anticipated to decrease as snow and ice cover diminishes. This will cause more solar radiation to be absorbed, increasing the warming cycle.

Occurring in the absence of oxygen.

Resulting from or produced by human beings.

A large group or chain of islands.

The gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1%) and oxygen (21%), together with a number of trace gases, such as argon (0.93%), helium, carbon dioxide (0.035%) and ozone.

Includes any form of carbon in the atmosphere, including carbon dioxide (CO₂), methane (CH₄), carbon monoxide (CO) and various gaseous organic compounds. As carbon dioxide and methane make up the majority of atmospheric carbon they are the most important gases to consider in any study or description of the carbon cycle.

The approximate amount of time it would take for the anthropogenic portion of a greenhouse gas concentration to return to its natural level as a result of either being converted to another chemical compound or being taken out of the atmosphere by a sink. This time depends on the pollutant's sources and sinks as well as its reactivity. The lifetime of a pollutant is often considered in conjunction with the mixing of pollutants in the atmosphere; a long lifetime will allow the pollutant to mix throughout the atmosphere. Average lifetimes can vary from about a week (sulfate aerosols) to more than a century (chlorofluorocarbons (CFCs), carbon dioxide).

The smallest unit of an element that can exist as a stable, independent entity.

The mass of an atom, expressed in Atomic Mass Units (AMU or U).

A measurement of an atom's mass. 1 Atomic Mass Unit is 1.66 X 10^-24g. The mass of one carbon (¹²C) atom is 12 U.

The chemical species in which an element can be taken up by an organism. For example, most plants cannot take up nitrogen when it is in the form N₂. In order to be useable by plants, the nitrogen must first be converted into NO₃^- or NH₄ by bacteria in the soil.

A chemical used in the production of polymeric plastic foams that are used to manufacture things like pool noodles, food packaging and packing peanuts to name a few.

Tropospheric gases have extremely different lifetimes. For example, methane remains in the troposphere for 21 years while sulphur hexafluoride (SF₆) can last as long as 3,200 years. There are several ways that a gas' concentration in the troposphere can decrease:
1) A gas can be broken down by hydroxyl radicals in the troposphere. These radicals can oxidize compounds such as methane. In fact, methane in our atmosphere is eventually converted to carbon dioxide as a result of reaction with hydroxyl radicals.
2) A gas can react with and be broken down by ultraviolet radiation from the sun.
3) A gas can dissapate into higher levels of the atmosphere. Molecules that have extremely strong bonds are not reactive and diffuse into higher layers of the atmosphere.

A biogenous sediment that is made of the calcium carbonate shells and skeletons of marine organisms.

The flow of carbon (in various forms, e.g., as carbon dioxide or carbonates) through the atmosphere, ocean, terrestrial biosphere and lithosphere.

A naturally occurring gas, also produced by burning fossil fuels, burning biomass, and other industrial processes; it is the principal anthropogenic greenhouse gas that affects Earth's radiative balance. It is the reference gas against which other greenhouse gases are measured.

The difference between projected yearly carbon emissions based upon humanity's current emission activity and stabilized carbon emissions. It is the region on the projected yearly carbon emissions graph between the path towards doubled emissions in 50 years and the path in which emissions do not increase over the next 50 years. The carbon stabilization triangle would prevent the emission of an additional 200 Gt C into the atmosphere over 50 years.

1 Gt of carbon over 50 years or a total of 25 Gt C that is prevented from entering the atmosphere over the next 50 years. This removes a wedge from the carbon stabilization triangle on the projected emissions of carbon graph. If 8 wedges are removed from the graph, the entire carbon stabilization triangle is removed and carbon emissions are stabilized at present day values.

The maximum population of a particular organism that a given environment can support without detrimental effects.

The process in which water and carbon dioxide interact with minerals in rock, gradually breaking them down. Erosion speeds this process by exposing more layer of rock. Chemical weathering generally has the effect of sequestering carbon from carbon dioxide in the form of calcium carbonate.

An interaction between processes in the climate system is called a climate feedback when the result of an initial process triggers changes in a second process that in turn influences the initial one. Positive feedback intensifies the original process, and negative feedback reduces it.

A climate refugee is a person displaced by climatically induced environmental disasters resulting from incremental and rapid ecological change, resulting in increased droughts, desertification, sea level rise, and the more frequent occurrence of extreme weather events such as hurricanes, cyclones, fires, mass flooding and tornadoes.

The highly complex system consisting of five major components and the interactions among them: the atmosphere, the hydrosphere, the cryosphere, the land surface and the biosphere.

The point at which the buildup of minor changes or incidences reaches a level that triggers a more significant change, or where global climate shifts from one stable state to another stable state.

Airborne particles that serve as the initial site for the condensation of liquid water, which can lead to the formation of cloud droplets.

A problem affecting or created by multiple parties or individuals which requires the cooperative action of all parties to resolve.

The transfer of energy from one molecule to another through a collision.

The transfer of energy through direct contact and collisions between neighboring molecules.

Vertical movement of air caused by the expansion of the air heated by the earth's surface.

A chemical bond where two atoms are connected to each other by sharing a pair of electrons.

The component of the climate system consisting of all snow, ice, and frozen ground (including permafrost) on and beneath the surface of the Earth and ocean.

Deep water is formed in areas of high salinity and low temperature, where water is the most dense. This usually occurs in polar regions in the North Atlantic. Deep water production feeds the Great Ocean Conveyor Belt. This process is in jeopardy due to recent loss of polar ice sheets and arctic water freshening.

Loss of forests. At least eleven million hectares of tropical forest are lost every year. Although the causes vary by region, one estimate indicates that slash-and-burn agriculture and scavenging for wood-fuel, often in the wake of commercial road building, accounts worldwide for 40-50% of deforestation. Grazing accounts for 10%, commercial agriculture for 10-20%, forestry and plantations for 5-10% and forest fires for 1-15%.

A process carried out in bacteria in which oxidized forms of nitrogen are reduced (gain electrons) to form molecular nitrogen (N₂) as an end product.

The gradual transformation of habitable land into deserts in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variation and human activities.

A stable, less abundant isotope of hydrogen with 1 neutron and 1 proton (the most abundant form of hydrogen has 1 proton and no neutrons).

A molecule that contains only two atoms.

Typically deployed into the ocean by a ship, drifters are floating devices used to explore ocean currents, which move at a pace consistent with the average flow of water sub-surface.

A condition at which forward and reverse reactions are taking place at the same time. If the forward and reverse reactions are taking place at the same rate, then there is no net change in the amounts of reactants or products.

The altitude at which IR photons have a high probability of escaping into space relative to the altitudes below it.

Refers to the periodic climate pattern that occurs across the tropical Pacific Ocean roughly every five to seven years. It is characterized by variations in the temperature of the surface of the tropical Eastern Pacific-warming or cooling known as El Niño and La Niña respectively-and air surface pressure in the tropical Western Pacific-the Southern Oscillation. ENSO causes extreme weather (such as floods and droughts) in many regions of the world.

The ratio of the emissive power of a surface at a given temperature to that of a blackbody at the same temperature and the same surroundings.

In danger of becoming extinct. A group of organisms is considered to be endangered when there has been a recent severe population reduction, the geographic range of the group is limited, the population size is less than 250 individuals, or quantitative analysis has shown a relatively high probability of extinction in the near future.

Refers to an organism or disease that is confined to a particular locality, region, or (in the case of disease) people.

The effect of increasing greenhouse gas concentrations in the atmosphere, which leads to an increase in temperature through increased absorption of the infrared radiation emitted by Earth.

A state of rest or balance due to the equal action of opposing forces.

The amount of carbon dioxide emissions that would cause the same integrated radiative forcing, over a given time horizon, as an equivalent amount of well-mixed greenhouse gases. Equivalent carbon dioxide emission is a standard and useful metric for comparing emissions of different greenhouse gases but does not imply exact equivalence of the corresponding climate change responses.

The multinational organization of European countries that coordinates aeronautical research and technology.

An increase in the nutrient (nitrate, phosphate etc.) content of a freshwater system typically resulting in excessive growth of algae. As these algal blooms die off the decomposition of this dead organic matter depletes the water of oxygen necessary to support other organisms.

Relating to a mathematical expression containing one or more exponents. Something is said to increase or decrease exponentially if its rate of change increases as the function's value increases and must be expressed using exponents. The basic formula for this function is of the form a·x^b. A graph of such a rate would appear not as a straight line, but as a curve that continually becomes steeper or shallower. Often, this term is used to desribe rapid, unchecked growth.

A species is considered extinct when there are no living members on the planet. Some causes for extinction include disease, habitat destruction, natural disasters and climate change.

A process of system dynamics in which a system reacts to amplify or suppress the effects of a force that is acting upon it. For example, in the climate system, warmer temperatures may melt snow and ice cover, revealing the darker land surface underneath. The darker surface absorbs more solar energy, causing further temperature increase, thus melting even more snow and ice cover and so on. This is positive feedback, in which warming reinforces itself. In negative feedback, a force ultimately reduces its own effect. For example, when the Earth's surface grows warmer, more water evaporates, forming more clouds. If the clouds are large and widely distributed, they will tend to reflect more solar radiation back into space than the dark ground underneath would, cooling the earth's surface and reducing the impact of warmer temperatures.

Increased rate of plant growth in conditions of higher carbon dioxide concentration. Generally applies to plants with a C3 photosynthetic pathway.

A type of particulate matter in which the particles have diameters less than 2.5 µm.

Emissions of greenhouse gases (in particular carbon dioxide) resulting from the combustion of fuels from fossil carbon deposits such as oil, gas, and coal.

A technique for separating compounds in a mixture by differences in their abilities to be removed from a solid phase into a passing gas stream.

One gigatonne is equal to 10¹⁵ grams, which is also equivalent to one billion tonnes, or one petagram.

The glacial time scale is on the order of thousands of years and includes the oscillation between glacial and interglacial time periods.

Concerned with or relating to conservation of the world's natural resources and improvement of the environment.

The process of designing chemical products and processes to reduce or eliminate the generation of hazardous substances.

An industrial process used to produce ammonia by reacting nitrogen gas and hydrogen gas over an enriched iron or ruthenium catalyst at high temperature and pressure. This process is responsible for the production of around 100 million tons of fertilizer each year.

A collective term for partially halogenated organic species, including the chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), halons, methyl chloride, methyl bromide, etc. Many of the halocarbons have large Global Warming Potentials. The chlorine and bromine-containing halocarbons are also involved in the depletion of the ozone layer.

The amount of heat energy required to raise the temperature of a substance by a unit temperature interval under specified conditions, usually measured in joules per kelvin. Materials with high heat capacities, such as water, require greater amounts of heat to increase their temperatures than do substances with low heat capacities, such as metals.

The energy contained in a substance due to the movement of the particles in the substance. It is also called thermal energy.

Water molecules that contain a larger proportion of heavier hydrogen isotopes. As these heavier hydrogen isotopes, also known as 'deuterium' atoms, contain 1 neutron and 1 proton, they are 10% more heavy than regular water and much less abundant. The ratio of heavy water to regular water molecules is roughly 1:20 million.

The Holocene geological epoch is the latter of two Quaternary epochs, extending from about 11.6 kya to the present.

A molecule such as N₂ or O₂ that is made of two atoms of the same element.

Organic molecules made of carbon, hydrogen, chlorine, and fluorine that are used in insulating foams, aerosol propellants, as well as refrigerants in refrigerators and air conditioners.

Is a different term for the water cycle. The water cycle involves the exchange of water between the atmosphere, the cryosphere (frozen water: glaciers, ice, snow) and the hydrosphere (liquid water: lakes, rivers, oceans). Exchange processes include evaporation, precipitation, freezing, melting and runoff, among others.

The component of the climate system comprising liquid water, such as oceans, seas, rivers, fresh water lakes, underground aquifers, etc.

A hydroxyl (OH) group that has an unpaired electron. This species is formed by reaction of O₂ with UV light from the sun and is a very reactive species, typically lasting only a second or so before undergoing a reaction of some sort. A hydroxyl radical will usually act as an oxidizing agent, taking an electron from a species with a weaker affinity for electrons.

An ice age or glacial period is characterised by a long-term reduction in the temperature of Earth's climate, resulting in the growth of continental ice sheets and mountain glaciers.

A cylinder of ice drilled out of a glacier or ice sheet.

A period of rapid industrial growth with far-reaching social and economic consequences, beginning in Britain during the second half of the eighteenth century and quickly spreading to continental Europe and the United States. The industrial revolution marks the beginning of a substantial increase in the use of fossil fuels and the emission of carbon dioxide. The terms pre-industrial and industrial refer to the period before and after 1750, respectively.

Used to determine connectivity patterns between atoms in molecules by measuring the absorption of infrared radiation as a function of the wavelength, which can reveal details about a molecule's composition. Also used to determine if a gas is a greenhouse gas.

The solar radiation received at any particular area of the Earth's surface, which varies from region to region depending on latitude and weather.

Isotope Ratio Mass Spectrometry (IRMS) is used to find the isotopic composition of elements within a sample. This is accomplished by measuring the mass-to-charge ratio of individual molecules. IRMS is a sensitive technique that is able to measure very small differences in the masses and abundances of isotopes in a sample. Isotope ratios can be used in a variety of applications including determining the origin of atmospheric gases such as methane and carbon dioxide.

Atoms of the same element with different numbers of neutrons.

The longest continual set of data measuring the concentration of carbon dioxide in our atmosphere. This data set was begun in 1958 at Mauna Loa Hawaii under the supervision of Charles David Keeling.

The scientific unit of measurement for temperature where a change of 1°C is equivalent to 1°K. Absolute zero, the temperature at which all thermal motion ceases, is the null point for this unit of measurement, so 0°K is equal to -273.15°C.

The energy of motion.

The rate at which temperate changes with altitude.

The Last Glacial Maximum refers to the time of maximum extent of the ice sheets during the last glaciation, approximately 21 kya. This period has been widely studied because its global cooling patterns are comparable to 21st century.

The regular geometrical arrangement of atoms in a crystal.

A principle used to predict the changes in a chemical equilibrium when conditions are changed: If a chemical system in dynamic equilibrium is disturbed by changing conditions, it will shift to counteract that change.

The upper layer of the solid Earth, both continental and oceanic, which includes the Earth's crust and upper mantle.

A period, between approximately 1400 and 1900 AD, marked by frequent cold episodes in Europe, North America, and Asia. Mountain glaciers, especially in the Alps, Norway, Iceland, and Alaska, expanded substantially.

A technique for measuring relative molecular mass by accelerating charged particles through an electric field.

The Montreal Protocol is short for the Montreal Protocol on Substances That Deplete the Ozone Layer. It is an international treaty designed to protect the ozone layer by gradually phasing out the substances responsible for ozone depletion. Originally signed in 1987 it has undergone several revisons since that time and is currently ratified by the majority of the nations on our the planet (196 total).

When anthropogenic emissions by sources and sinks of greenhouse gases are balanced so that the amount of greenhouse gases being emitted are equal to the amount of greenhouse gases being removed from the atmosphere.

A process in which ammonia (NH₃) donates electrons to oxygen (is oxidized) to form nitrites (NO₃^-), which are then oxidized into nitrates (NO₂^-). This process is carried out by certain species of ammonia-oxidizing bacteria and archaea. Often the two parts of the process are carried out in separate species of bacteria or archaea that are often found together.

A set of chemical pathways whereby nitrogen moves in different chemical forms such as N₂, N₂O, and nitrates through the biosphere.

A natural process in which nitrogen from the atmosphere (in the form of N₂) is converted into ammonia (NH₃). This process is most often carried out in bacteria known as diazotrophs.

Greenhouse gases, such as carbon dioxide, that do not condense and precipitate on earth; as opposed to condensing greenhouse gases, such as water vapour, which readily condenses and precipitates on earth.

A decrease in the pH of sea water due to the uptake of anthropogenic carbon dioxide.

A measure of the rate at which heat storage by the global ocean increases as global surface temperatures rise. Ocean heat uptake efficiency is a useful parameter for climate change experiments; it can be compared with the climate sensitivity parameter to gauge the relative importance of climate response and ocean heat uptake in determining the rate of climate change.

Ozone, the triatomic form of oxygen (O₃), is a gaseous atmospheric constituent. In the troposphere, it is created both naturally and by photochemical reactions involving gases resulting from human activities (smog). Tropospheric ozone acts as a greenhouse gas. In the stratosphere, it is created by the interaction between solar ultraviolet radiation and molecular oxygen (O₂). Stratospheric ozone plays a dominant role in the stratospheric radiative balance. Its concentration is highest in the ozone layer.

A region of the stratosphere, about 20 to 25 km above the Earth's surface, where ozone concentrations are highest. This layer has been depleted by human emissions of chlorine and bromine compounds, which produce free radicals that break down stratospheric ozone molecules.

Climate during periods prior to the development of measuring instruments, including historic and geologic time, for which only proxy climate records are available.

The study of past climates. This is most often done by examining the physical, chemical or biological properties of a sequence of sediments.  In various parts of the world, marine sediments, lake sediments, peat bogs, corals, ice cores, speleothems (stalagmites and stalactites) and tree rings are studied.  For more ancient times, fossils found in sedimentary rocks can indicate what past environments were like.

Tiny solid or liquid particles dispersed and suspended in the air.

The point in time when the maximum rate of oil production is reached, after which production will gradually decline. American geophysicist M. King Hubbert posited a theory in 1956 that, for any given geographical area, oil production would follow a bell-shaped curve that can be used to predict future oil production, given past discovery and production data.

A measure of how inaccurate a measurment is; found by the following formula: (measured value-actual value)/ actual value x 100%.

Compounds containing only fluorine and carbon that were designed to replace CFCs. Perfluorocarbons are in household and industrial products such as stain repellants, lubricants, fire retardants, fire suppressants and pesticides. These compounds generally have high global warming potentials.

A layer of soil a few tens of centimeters to several hundred metres thick that remains frozen year round. "Perennially frozen ground."

One petagram is equal to 10¹⁵ grams, which is also equivalent to one gigatonne, or one billion tonnes.

A pH indicator is a coloured chemical compound that is added in small amounts to a soloution so that the pH (acidity or basicity) of the solution can be determined visually.

An individual bundle or "particle" of light energy.

The process by which plants convert carbon dioxide (CO₂) and water (H₂O) to sugars, releasing oxygen in the process. There are several pathways of photosynthesis with different responses to atmospheric carbon dioxide concentrations.

The capacity of organisms with the same genotype to vary in developmental pattern, in phenotype, or in behavior, according to varying environmental conditions.

This epoch was characterised by numerous (at least 17) worldwide changes of climate, cycling between glacial (cool) and interglacial (warmer) period.

A warm epoch with only limited glaciation, the mid-Pliocene was the last period that had comparable temperature to those predicted to occur over the next 300 years.

A process in system dynamics in which a system reacts to amplify the effects of a force that is acting upon it. An example of a positive feedback loop in the climate system is the effect of warmer temperatures on Earth's albedo. As the Earth warms, the increasing temperatures may cause snow and ice cover to melt, revealing the darker land surface underneath. The darker surface absorbs more solar energy, causing further temperature increase, thus melting even more snow and ice cover.

An area dominated by extensive tracts of tall grasses and very few trees. These areas are found in the mid-Western regions of North America and are usually characterized by very fertile soil, making them ideal for agriculture.

A proxy is a record that is interpreted, using scientific principles, to represent a historical variable that cannot be directly measured. Examples of proxies include tree ring records, characteristics of corals and various data derived from ice cores.

The movement of electromagnetic energy through a medium or through space.

The difference between total incoming and total outgoing energy. If this balance is positive, warming occurs; if it is negative, cooling occurs. Averaged over the globe and over long time periods, this balance must be zero to maintain a stable climate. Zero balance implies that, globally, the amount of incoming solar radiation must equal the sum of outgoing reflected solar radiation and outgoing thermal infrared radiation emitted by the climate system. A perturbation of this global radiation balance is called radiative forcing.

Gases, present in small quantities in the atmosphere, that absorb incoming solar radiation or outgoing infrared radiation, thus affecting the vertical temperature profile of the atmosphere. These gases include water vapour, carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and ozone.

An instrument that makes quantitative measurements of the amount of electromagnetic radiation falling on it in a specified wavelength interval.

The rate of change, or the slope of a graph, is calculated by dividing the change in the y-value by the change in the x-value. These changes are often calculated by subtracting the values at the starting point from the values at the end point of a graph.

When an electromagnetic wave changes direction, returning to the media from which it originated.

A component of the climate system, other than the atmosphere, which has the capacity to store, accumulate or release a substance of concern. Oceans, soils, and forests are examples of reservoirs of carbon. A pool is an equivalent term. The absolute quantity of the substance of concern held within a reservoir at a specified time is called the stock.

A group of mammals, including the cow, sheep, buffalo and goat, which possess four stomachs and regurgitate undigested food from their first stomach. This process is known as chewing cud. They live in a symbiotic relationship with microorganisms in their digestive tract that enable them to digest cellulose, releasing methane in the process.

The maximum quantity of water vapour air can hold before it becomes saturated, at which point some of the water vapour must condense into liquid water, or sublime into solid ice crystals.

Sea levels can change, both globally and locally, due to (i) changes in the shape of the ocean basins, (ii) changes in the total mass of water and (iii) changes in water density (steric changes). Density changes induced by temperature changes only are called thermosteric, while density changes induced by salinity changes are called halosteric.

Of, pertaining to, or having the nature of solid fragmented material, such as silt, sand, gravel, chemical precipitates, and fossil fragments, that is transported and deposited by water, ice, or wind, or that accumulates through chemical precipitation or secretion by organisms, and that forms layers on the earth's surface.

The desired value of a closed-loop feedback system.

Refers to a condition in which an individual has one sickle gene and one normal adult hemoglobin gene. Because the sickle gene is recessive, this person does not have sickle-cell disease, a condition caused by two sickle genes which can lead to death or severe illness. Sickle-cell trait provides protection against malaria.

The Sun exhibits periods of high activity observed by sunspots, high radiative output, magnetic activity and emission of high-energy particles. These variations take place on a range of times scales from millions of years to minutes.

A quasi-regular modulation of solar activity with varying amplitude and a period of between 9 and 13 years.

Electromagnetic radiation emitted by the Sun, also referred to as shortwave radiation. Solar radiation has a distinctive range of wavelengths (spectrum) determined by the temperature of the Sun.

The amount of radiation or energy received from the Sun at any given point.

The Special Report on Emissions Scenarios have been used to make projections of possible future climate change.

The speciation of an element is the distribution of an element amongst defined chemical species in a system.

A region of the upper atmosphere that extends from the tropopause (the upper boundary of the troposphere at an altitude between 9 and 16 km above the earth) to about 50 km above the Earth. In this layer, temperature rises slowly with altitude. The properties of the stratosphere include very little vertical mixing, strong horizontal motions, and low water-vapour content compared to the troposphere. This region contains ozone, which absorbs incoming UV radiation.

Dark blotches on the Sun indicating increased solar activity.

Greenhouse gases with extremely large global warming potentials on a mass per mass basis as compared to CO₂. The majority absorb at the peak of earth's IR emission spectrum and have extremely long atmospheric lifetimes. Many are anthropogenic in origin. Though currently present in the atmosphere in extremely small quantities they have the potential to build up in the atmosphere.

To cause a chemical solution to be more highly concentrated than is normally possible under certain conditions of temperature and pressure.

A unit of energy used over the course of a year. 1 terawatt hour is an energy unit produced by multiplying power in terawatts by time in hours. A TWh is equal to 10⁶ kWh.

The tendency of matter to change in volume in response to a change in temperature. When a substance is heated, its particles begin moving more rapidly, and thus usually maintain a greater average separation, leading to expansion.

The amount of solar radiation received outside the Earth's atmosphere on a surface normal to the incident radiation, and at the Earth's mean distance from the Sun. Reliable measurements of solar radiation can only be made from space and the precise record extends back only to 1978. The generally accepted value is 1,368 Wm^-2.

The lower atmosphere, from the ground to an altitude of about 8 km at the pole, about 12 km in mid-latitudes, and about 16 km in the tropics. Clouds and weather systems take place in the troposphere. This is the region with the highest concentration of greenhouse gases.

The rate at which temperate decreases with increasing altitude within the troposphere.

The United Nations is an international organization founded in 1945 that aims to facilitate cooperation among its member states in international law, security, economic development, social development and human rights. It is compromised of 193 member states, including almost every country in the world.

A liquid's vapour pressure is an indication of the tendency of the molecules in the liquid to evaporate from liquid to gaseous form. A liquid with a high vapour pressure will be volatile and evaporate easily, while a liquid with a low vapour pressure will not easily evaporate.

An infection transmitted by the bite of an infected organism, such as a mosquito, a tick, a sandfly or a blackfly.

In a molecule, the stretching, bending or twisting of bonds.

Water vapour pressure is an indication of the tendency of water molecules to evaporate and move from liquid to gaseous form. It is a measure of the pressure water vapour exerts on liquid water, which will increase as the relative number of molecules tending to escape into a gaseous state increases. Water vapour pressure is directly related to temperature.

A measure of the number of waves in unit of distance. Wavenumber is inversely proportional to wavelength, as shorter wavelengths will have more waves per unit of distance.

The chemical or physical breakdown of rocks by atmospheric agents and physical processes.

A sudden, abrupt cold episode, which interrupted the sustained warming trend between the Last Glacial Maximum and the Holocene.