Understanding Climate Change - Glossary

This is the glossary for readings 1-7 for my course on climate change.

Understanding Climate Change - Glossary

(Alan Holyoak, PhD)

Absolute path (Coriolis effect) – The path of a moving object actually moves in a straight line even though the Earth is rotating under it.

Absolute reference frame (Coriolis effect) – The observer is stationary in space and the path of a moving object is in a straight line with the Earth rotating under it.

Absolute zero – This is zero degrees Kelvin (-273^oC or -459^oF), and indicates the complete absence of heat, i.e., when molecules stop vibrating.

Absorption – In terms of electromagnetic radiation, this occurs when photons of energy are taken up by matter.  When a photon is taken up, an electron becomes energized and moves to a higher energy state.  Energy is released when the energized electron releases the energy it absorbed and it then drops to a lower energy state.

Abyssal plain – A flat plain that makes up the majority of world’s seafloor 3-6 miles below the ocean surface.

Abyssalpelagic zone – Ocean depths from the 4^oC depth mark to 6000 meters, and reaches all the way down to the abyssal plain.

Aerosols – Particulate matter and droplets of liquid small enough to remain suspended in the air for an extended period of time.

Albedo – The reflectivity of a surface as measured on a scale of 1.0 to 0.0.  A perfect white surface will reflect all radiation that strikes it and have a value of 1.0, while a perfect black surface will absorb all radiation that strikes it and have a value of 0.0.

Anoxic – A situation where there is no oxygen present.

Antarctic Circle – Line of latitude at 66.5^oS that experiences one day each year where the sun does not rise above the horizon (that’s on the northern hemisphere summer solstice).

Anthropogenic – Produced or generated by humans.

Apparent path (Coriolis effect) – The path of an object moving over the Earth appears to deflect to the right in the northern hemisphere and to the left in the southern hemisphere, but only if the observer is on the surface of the rotating planet.

Arctic Circle – Line of latitude at 66.5^oN that experiences one day each year where the sun does not rise above the horizon (that’s on the northern hemisphere winter solstice).

Autumnal equinox – The day between the northern hemisphere summer and fall when everywhere on the planet has equal day and night lengths, usually around Sept 22^nd.

Bathypelagic zone – This layer in the ocean exists between the 10^oC and the 4^oC temperature layers.  This layer is in perpetual darkness.

The Big Experiment – The experiment involves the emission of increasing amounts of fossil carbon into the atmosphere, starting during the Industrial Revolution, that affects the amount of greenhouse gases there and the atmosphere’s greenhouse efficiency. 

The Boring Billion Years – The time period between about 1.8 – 0.8 billion years ago when the amount of oxygen in the atmosphere stayed at constant, low concentrations.

Calcium carbonate – A white compound made of one atom of calcium (Ca) and one carbonate ion (CO₃^-2).  This compound is extremely common, and can be made by organisms such as coral, snails, foraminiferans, etc.

Carbon cycle – The dynamic action of chemical, biological, and geological processes that release, take up, and store carbon on our planet.  

Carbon sink – Any process that removes carbon from the biosphere.

Carbon source – Any process that releases carbon into the biosphere.

Coal – Fossil fuel that was formed when ancient forests died, presumably in swamps, were covered by sedimentary rock, and under intense temperature and pressure became coal.  Coal contains carbon, hydrogen, and impurities like sulfur.

Continental shelf – Seafloor with a shallow slope that extends from the edge of a continent to the continental slope.

Continental slope – Seafloor that has a steep slope and drops from the outer edge of the continental shelf to the ocean’s abyssal plain.

Coral – Coral are animals related to sea anemones and jellyfish.  Some corals secrete calcium carbonate skeletons that form the framework for coral reefs. 

Coriolis effect – The apparent deflection of a moving object that is not attached to the earth, e.g., wind or water currents.  Coriolis effect causes moving objects to deflect to the right in the northern hemisphere and to the left in the southern hemisphere. 

Cyanobacteria – Also known as blue-green algae or blue-green bacteria.  These bacteria carry out photosynthesis, and are believed to be the first group of photosynthetic organisms that appeared on Earth. 

Deep-water currents – Ocean currents below the thermocline, existing all the way to the seafloor.  Thermohaline circulation forms and drives these currents.

Diffuse radiation – Scattered light that reaches the Earth’s surface.

Direct solar radiation – Solar radiation that passes through the atmosphere to the Earth’s surface without being scattered, absorbed, or reflected.

Eccentricity – Milankovitch cycle describing the oscillations of the shape of Earth’s orbit around the sun.

Ekman spiral –Surface waters move due to friction between it and surface winds.  The next layer of water down also moves, but due to Coriolis effect it moves in slightly different direction, and so on for each succeeding layer of deeper water.  This produces water moving in different directions at different depths.

Ekman transport – Surface waters move due to friction with surface winds.  Where Coriolis effect surface water to move away from the shore, deeper water is pulled to the surface, upwelling.

Electromagnetic spectrum of radiation – The range of all wavelengths of radiation from gamma rays at the shortest wavelength to long radio waves at the long end.

Energy budget – This is the balance between the amount and rate of energy entering a system and the amount and rate of energy leaving a system during a period of time.

Entropy – Entropy is used to indicate the efficiency of energy transformation.  The amount of energy available to do work before energy transformation equals the amount of energy able to do work after the energy transformation plus entropy.  Or, entropy represents waste heat no longer able to do work whenever energy transformation takes place.  The amount of entropy in a closed system increases or stays the same.

Epipelagic zone – This the top layer of the water column in the world’s oceans, and it extends from the surface to a depth where only about 1% of the light that strikes the surface has not been absorbed or scattered.  This is usually the top few hundred meters of the ocean, and is where photosynthesis occurs in the ocean.

Equinox – Two days each year when the length of day and night are exactly the same everywhere on earth: Vernal (spring) equinox and Autumnal (fall) equinox.

Ferrel Cell – Air circulation pattern where air rises at 60oN & S and returns to the surface at 30^oN & S.  This produces low pressure and higher amounts of rainfall at 60^o, and high pressure and low precipitation at 30^o. 

First law of thermodynamics – The total amount of energy in closed system will remain constant.  And energy (i.e., heat) will move from a location of high energy to low energy until the amount of energy is uniform throughout the closed system.

Foraminifera – One of the most abundant groups of marine plankton.  They are related to amoeba, and they secrete a calcium carbonate (CaCO₃) shell.

Fossil carbon – Carbon that was once part of a living thing, but has been removed from the biosphere, embedded in the sediment and formed coal, oil, or natural gas.

Fossil fuel – Once living material, mainly algae, plankton, and trees, that become fossilized into coal, crude oil, and natural gas.

Freezing point depression – Water has to get colder to freeze when it contains lots of salt (solutes) compared to when it contains less salt (solutes).

Gigaton – 10¹⁵ grams (= 1000 trillion grams)

Global conveyor (a.k.a. Atlantic conveyor, conveyor belt) – Deep-ocean current established and driven by thermohaline circulation.  Water takes 100s-1000s of years to finish one complete cycle.

Global Warming Potential (GWP) – A measure of the ability of a single molecule of a substance to absorb infrared radiation.  Carbon dioxide is assigned a GWP of 1.0, and the GWP of all other greenhouse gases are based on the CO₂ standard. 

Great Oxygenation Event – Time period between about 2.5 – 1.8 billion years ago when oxygen first accumulated in Earth’s atmosphere.

Greenhouse effect – Infrared radiation is released by the Earth’s surface and by molecules in the atmosphere.  That heat is absorbed by greenhouse gases in the atmosphere that then release the energy in random directions.  This slows the rate of heat loss back into space.

Greenhouse gas – Any gas that is able to capture infrared radiation and temporarily hold that energy.  Different greenhouse gases absorb different wavelengths of energy.

Gulf Stream – Ocean surface current originating in the Caribbean Sea that moves along the east coast of North America and then moves across the North Atlantic Ocean.

Hadalpelagic zone – Water in ocean trenches.

Hadley Cell – Air circulation pattern where air rises at the equator and returns to the surface at 30^oN & S.  This produces low pressure and higher amounts of rainfall at the equator, and high pressure and low precipitation at 30^o.

Heat sink – Matter or process that absorbs heat. 

Heat source – Matter or process that releases heat.

Heavy oxygen – An isotope of oxygen with a molecular weight of 18 (¹⁸O)

Henry’s Law – The amount of gas that can be dissolved in water is a function of temperature and pressure.  Water under high pressure and at low temperature can hold more gas in solution than water that is warm and under low pressure.

Incident solar radiation – Solar radiation that strikes the Earth/Atmosphere system.  This is the radiation that is subsequently reflected, scattered, or absorbed.

Industrial Revolution – A significant change between 1750-1850 where the mechanization of agriculture, industry, transportation, etc., caused profound changes in the way we live, work, produce goods, etc., made possible by the development of steam power and the use of fossil fuels.

Insolation – A measure of solar radiation received per some unit area, e.g., Watts per meter squared.

Intertidal zone – The narrow zone around ocean shorelines where seafloor is exposed to the air during low tides and covered by water during high tides.

Intertropical convergence zone (ITCZ) – Surface air flowing north and south converge at the equator, heats up, and rises.  A perpetual band of cloud cover indicates the latitude of the ITCZ.

Isotope – Variants of a chemical element.  All (isotopes) variants have the same number of protons but different variants (isotopes) have different numbers of neutrons. E.g., ¹²C ¹³C ¹⁴C

Jet stream – Narrow, fast-moving currents of air in the upper troposphere that form along the boundaries between Hadley, Ferrel, and Polar cells. 

Joule – Unit of measurement for energy used doing work.  One Joule is the same expending one Watt of energy per second.

Latent heat – Heat that is absorbed by something without that matter changing temperature.  For example, latent heat is released when water vapor changes into liquid water.  Latent heat is absorbed as ice melts, but the temperature of the ice does not change. 

Law of conservation of matter – The amount of matter in a closed system will remain constant.  Matter can be rearranged by location or undergo chemical change, but the total amount of matter does not change.

Light oxygen  - An isotope of oxygen with a molecular weight of 16 (¹⁶O)

The Little Ice Age – A period of cool climate between 1600-1700 when no sunspots were observed.  Also called the Maunder Minimum.

Mass extinction event – A time period where many species go extinct in a short period of time.  Extinction events are often associated with rapid climate change.

Maunder Minimum – A period of cooling climate between about 1600-1700 when no sunspots were observed.  Also called “The Little Ice Age”.

Mesopelagic zone – This zone extends from the bottom of the epipelagic zone down to several hundred meters to a depth where water temps cool to about 10^oC.

Mesosphere – The layer of the atmosphere that extends from about 30-53 miles in altitude.  Meteorites usually burn up as shooting stars here.

Micrometer – 1/1000^th of a millimeter. Designated by “μm”.

Mid-oceanic ridges – An interconnecting series of undersea mountain ranges, the longest in the world, formed where tectonic forces cause seafloor spreading and new oceanic crust is produced.

Milankovitch cycles – natural oscillations in the shape of Earth’s orbit, tilt of Earth’s axis, and the direction the axis is pointing relative to the sun.  See also eccentricity, obliquity, and precession.

Montreal Protocol – The official name is “The Montreal Protocol on Substances that Deplete the Ozone Layer.”  This is an international agreement to stop producing chlorine and bromine containing substances (such as CFCs) that were discovered to deplete the stratospheric ozone layer.  The agreement was signed in 1987 and implemented in 1989. 

Nanometer – 1/1,000,000^th of a millimeter. Designated by “nm”.

Natural gas – Small molecules made of carbon and hydrogen are formed when crude oil and coal are also formed, and are gases under normal conditions.  E.g., Methane, propane, butane.

Neritic zone – The part of the ocean above the continental shelf.

Net radiation (R_net) – This is used to indicate the net balance of energy entering and energy leaving a particular area of Earth’s surface.  This is greatly affected by latitude.

Non-renewable energy – Any energy source that is finite or that takes such a long time to replenish itself that it is essentially non-renewable.  E.g., Fossil fuels can be replenished, but it takes millions of years for that to happen so it is considered to be non-renewable.

Obliquity – Milankovitch cycle describing the oscillation of the angle of tilt of the Earth’s axis.

Oceanic carbon sink – CO₂ diffuses into seawater from the atmosphere.  It or carbonates are then taken up by living things and incorporated into their bodies.  They die, and that carbon settles to the seafloor where it is covered by sediment.

Oceanic trenches – The deepest locations in the ocean, and exist where tectonic forces cause one plate to subduct under another plate.  Volcanoes are commonly formed and earthquakes occur regularly along trenches.

Oceanic zone – The part of the ocean over everything except the continental shelf.

Oil (crude oil, petroleum) – The remains of dead plankton and algae are covered by sediment, and under intense temperature and pressure becomes a mixture of carbon-containing molecules of different sizes that remain in a liquid state under normal conditions.  There is an immense amount of energy stored in these compounds that is released when it burns.

Ozone – A molecule made of three atoms of oxygen bonded to each other.  This is a harmful greenhouse gas when it is found in the troposphere, and it protects us from UV radiation when it is in the stratosphere.

Paleocene-Eocene Thermal Maximum (PETM) – A spike in global temperature that occurred about 55 million years ago, as indicated by proxy data from ocean sediment cores. 

Paleoclimatology – The study of climate changes throughout Earth’s history.

Pelagic zone – The part of the ocean where the seafloor is never uncovered by a low tide (everything other than the intertidal zone).

Petagram – Equal to one gigaton = 10¹⁵ grams (=1000 trillion grams, one liter of water = 10³ grams)

Photosynthesis – The biochemical process where energy from light is used make glucose (a carbohydrate) from carbon dioxide and water. 

Plate margins – This is where the edges of tectonic plates meet.

Polar Cell – Air circulation pattern where air rises at 60oN & S and returns to the surface near the poles.  This produces low pressure and higher amounts of rainfall at 60oN and high pressure and low precipitation at the poles.

Polar jet stream – Jet stream that sometimes forms at the boundary between Ferrel and Polar cells.

Precession – Milankovitch cycle describing oscillation of the direction Earth’s axis points relative to the sun. 

Radiation – This is electromagnetic energy.  This is NOT the same as radioactivity/radioactive decay.

Radiometric dating – A method for determining the absolute age of a sample by measuring the rate of radioactive decay of radioactive atoms in it.

Rayleigh scattering – The phenomenon that produces yellows, oranges, and reds seen at dawn and dusk, and that makes the sky appear blue the rest of the time.  Most Rayleigh scattering is done by molecules in the atmosphere, and blue light scatters more than other colors.  This is what gives the sky it’s blue color.  At dawn and dusk light travels through more light to reach the surface, scattering all blue light and leaving only longer wavelength light – reds, oranges.  Air pollution can accentuate Rayleigh scattering since there are more particles in the air and light scatters more than otherwise.

Ridge (jet stream) - In the northern hemisphere where a jet stream swoops toward the north, and at the same time rises to a higher altitude.  A high-pressure cell forms at lower altitudes as air from a jet stream descends from a ridge toward a trough.

Relative reference frame (Coriolis Effect) – The observer is on the surface of the planet, and is thus changing position as the Earth rotates.  From this frame of reference the apparent path of an object deflects to the right in the northern hemisphere and to the left in the southern hemisphere.

Renewable energy – Energy that comes from natural sources that can be replenished in a short period of time by natural processes, e.g., wood, wind, hydroelectric, solar panels, tides, biofuels, etc.

Rotational motion – The amount of spin a body experiences as the Earth rotates.  A body experiences 100% rotational motion when it is at one of Earth’s poles, and 0% rotational motion when it is on the equator.

Salinity – The salt content of water.

Scattering (of light) – The redirection of a ray of solar energy resulting from contact with aerosols.

Second law of thermodynamics – The amount of energy able to do work decreases whenever energy is transformed.  Every time energy is transformed entropy is produced and released as waste heat.

Sediment core – A cylindrical a sample of the sediment removed from the bottom of the ocean or a lake by using a plug or a drill. 

Solar faculae – Brighter, hotter areas on the surface of the sun that form when sunspots are also present. 

Specific heat – The amount of heat needed to change a substance’s temperature.  E.g., A substance with a high specific heat absorbs lots of heat before its temperature will change very much.  Water has the highest specific heat of any common substance.

Speleotherm – Stalactites, stalagmites, and other formations are formed when ions and other materials are dissolved by water as it percolates through rock layers, and that material is deposited when that water drips into a cave.

Stalagmite – A speleotherm that rises from the floor of a cave/cavern.

Stratosphere – The layer of the atmosphere that extends from 7-30 miles above the Earth’s surface.  This is where the ozone layer exists that protects us from harmful UV radiation.

Subduction/Subducted – A tectonic process where one crust plate is pushed underneath another crust plate. 

Subtropical jet stream – Jet stream that sometimes forms at the boundary between Hadley and Ferrel cells.

Summer solstice – The longest day of the year in the northern hemisphere, around June 22^nd.

Sunspot – A markedly darker and cooler area on the surface of the sun than surrounding sun surface.

Supercontinent – Two or more major continental plates that are temporarily fused together to form a larger landmass, e.g., Pangea.

Surface currents (ocean) – Movement of surface waters to 100s of meters deep that are formed and driven by surface winds and deflected by Coriolis effect.

Thermocline – Narrow depth separating warm surface waters from deep cold water; a narrow depth of rapid temperature change indicates it. 

Thermohaline circulation – The circulation of ocean waters driven by a combination of temperature and salinity factors that causes seawater to become dense enough to sink.  Major centers of thermohaline circulation are the North Atlantic and the waters surrounding Antarctica.

Thermosphere – The layer of the atmosphere that extends from 53-90 miles in altitude.  This is the top layer of Earth’s atmosphere.

Translational motion - The degree to which a body changes position as the Earth rotates.  A body experiences 0% motion when it is at one of Earth’s poles (it spins, but doesn’t change position), and 100% rotational motion when it is on the equator (it moves, but doesn’t spin at all).

Tree ring – Trees that experience seasonal growth produce one wide ring and one narrow ring of wood.  Together these rings represent one year’s worth of growth.  A tree’s age and annual growing conditions can be inferred from these rings.

Tropic of Cancer – A line of latitude 23.5^oN, the farthest north you can go and have the sun directly overhead for only one day a year (on the summer solstice).

Tropic of Capricorn – A line of latitude 23.5^oS, the farthest south you can go and have the sun directly overhead for only one day a year (on the winter solstice).

Troposphere – The layer of the atmosphere closest to the Earth’s surface, extending to an altitude of 3-12 miles.  This is where the vast majority of Earth’s weather events take place.

Trough (jet stream) – In the northern hemisphere where a jet stream dips toward the south, and at the same time dips to a lower altitude.  A low pressure cell forms in lower altitudes as a jet stream rises from a trough toward a ridge.

Upwelling – When deep, cool, nutrient-rich water is pulled up to the surface, usually by Ekman transport or offshore winds.

Ultraviolet (UV) radiation – Electromagnetic radiation with a wavelength of 10-400nm.  Exposure to shorter wavelength UV radiation can produce skin cancer and cataracts.

Vernal equinox – The day between the northern hemisphere winter and spring when everywhere on the planet has equal day and night lengths, usually around March 22^nd.

Visible light –The wavelengths of radiation we can detect with our eyes, between 380-740nm.

Watt – Unit used to express the expenditure of energy. One Watt = 1.0 Joule/second.  When used in climate science Watts are usually used to refer to the amount of energy per unit area, e.g., Watts/m².

Wavelength – The distance between two peaks or crests of a wave.

Winter solstice – The shortest day of the year in the northern hemisphere.  Usually around December 22^nd.