Climate Science & Radiation Midterm Study Guide

Comprehensive vocabulary flashcards reviewing heat, radiation, thermodynamics, ocean circulation, the carbon cycle, paleoclimate, and climate simulation dynamics for a midterm exam.

Temperature

A measure of internal heat energy corresponding to random molecular motion, where increased molecular motion results in higher temperature.

Conduction

Heat transfer occurring through direct contact when faster-moving molecules of a warmer substance collide with slower-moving molecules of a cooler substance.

Sensible Heat Flux

The heat flux associated with measurable changes in temperature between Earth's surface and the atmosphere, measured in units of power per unit area ($\text{W/m}^2$). Upward flux ($+$) transfers heat from surface to atmosphere, while downward flux ($-$) transfers heat from atmosphere to surface.

Latent Heat Flux

The heat flux associated with phase changes of water (such as evaporation) that removes heat from the surface with no change in temperature; it is generally positive ($+$) to indicate water loss from a wet surface to the atmosphere.

Convection

The vertical transfer of heat within a fluid (liquid or gas) when it is heated from below or cooled from above, causing warmer, less dense fluid to rise and cooler, denser fluid to sink.

Radiation

Energy that propagates through space or matter in the form of waves or subatomic particles; unlike conduction and convection, it can travel through a vacuum.

Stefan-Boltzmann Law

A radiation law stating that the total energy emitted across all wavelengths by an object is proportional to the fourth power of its absolute temperature ($E = \sigma T^4$), where $\sigma = 5.67 \times 10^{-8}\,\text{W/m}^2\,\text{K}^4$.

Inverse-Square Law

The physical principle stating that the total energy flux ($\text{W/m}^2$) transferred between two objects falls off inversely with the square of the distance ($\frac{1}{d^2}$).

Albedo

The ratio of reflected solar radiation to incident radiation. For Earth, it is approximately $0.3$ (meaning $\approx 30\%$ of incoming solar flux is reflected back to space).

Solar vs. Terrestrial Radiation Spectra

Solar radiation consists of shortwave energy (ultraviolet, visible, and near-infrared) emitted by the Sun at $\sim 5800\,\text{K}$, whereas terrestrial radiation consists of longwave energy (far-infrared) emitted by Earth's surface and atmosphere at $\sim 260\,\text{K}$.

Radiative Balance

The state wherein incoming solar radiation absorbed by Earth equals outgoing longwave radiation emitted to space: $\text{ISR} = S(1 - \alpha) = 342(1 - 0.3) \approx 240\,\text{W/m}^2 \approx \text{OLR}$.

Greenhouse Gas

A gas (such as $\text{CO}_2$ or $\text{H}_2\text{O}$) that significantly absorbs infrared terrestrial radiation emitted by Earth and its atmosphere via molecular vibrations and rotations.

Absorptivity Spectrum of the Atmosphere

The wavelength-dependent fraction of incoming radiation absorbed by individual gases (such as $\text{CH}_4$, $\text{N}_2\text{O}$, $\text{O}_2/\text{O}_3$, $\text{CO}_2$, and $\text{H}_2\text{O}$) and the whole atmosphere, leaving the atmosphere mostly transparent to solar radiation and opaque to terrestrial radiation.

Earth's Radiative Energy Imbalance

A net difference in global energy fluxes of approximately $1.5\,\text{W/m}^2$ more incoming radiation than outgoing radiation, driven by increases in atmospheric greenhouse gases and causing current global warming.

Ocean Stratification

The layering of ocean water by density—governed by temperature and salinity—where lighter, warmer, and fresher water floats over cooler, saltier, and denser deep water, thereby inhibiting vertical mixing.

Ekman Drift

The net surface water current generated by wind stress, deflected to the right of the wind direction in the Northern Hemisphere and to the left of the wind direction in the Southern Hemisphere due to Earth's rotation.

Upwelling

The wind-driven vertical transport of cold, salty, and nutrient-rich water from the deep ocean to the surface layer, supporting high biological productivity and chlorophyll concentrations.

Thermohaline Circulation

Also called the Great Ocean Conveyor belt; a large-scale, density-driven ocean circulation moving deep and bottom water across global ocean basins, initiated by deep convection in cold, high-salinity sub-polar regions.

Clausius-Clapeyron Relation

The physical relationship showing that the saturation vapor pressure (the maximum amount of water vapor air can hold in equilibrium with liquid water) increases exponentially with temperature.

Relative Humidity (RH)

The ratio of the actual amount of water vapor in an air parcel divided by the amount of water vapor that the air would hold at saturation for that temperature, expressed in $\text{g/kg}$ or parts per thousand.

Atmospheric Lapse Rate

The nearly constant rate at which air temperature decreases with increasing altitude in the troposphere, approximately $6.5\,^\circ\text{C/km}$.

Hadley Cell

A large-scale atmospheric circulation cell where air converges and rises near the equator (forming clouds and precipitation) and sinks in the subtropics, creating warm, dry, arid zones.

Climate Proxies

Physical, chemical, and biological indicators preserved within the geologic record (such as ice cores or ocean sediments) used to infer past climate parameters like temperature and sea level.

$\delta^{18}\text{O}$ Sedimentary Proxy

An isotopic geochemical ratio measured in ocean sediments that serves as a proxy for continental ice volume and sea level; a larger $\delta^{18}\text{O}$ value indicates greater ice sheet volume on land.

Milankovitch Cycles

Cyclical variations in Earth's orbital parameters—eccentricity (orbit shape), obliquity (axial tilt), and precession (axial wobble)—that modify the distribution and intensity of incoming solar radiation to pace glacial-interglacial epochs.

Snowball Earth

The coldest climate regime in Earth's history, characterized by a completely frozen surface with extensive ice sheets covering all continents.

Glacial Moraines

Massive accumulations of rock and sediment deposited directly by advancing and retreating ice sheets at mid-latitudes, responsible for geologic structures such as Long Island, New York.

Ocean Carbon Sink

The oceanic uptake of approximately $26\%$ of anthropogenic $\text{CO}_2$ emissions, primarily through the physical dissolution of $\text{CO}_2$ in seawater and subsequent changes in ocean chemistry.

Land Carbon Sink

The terrestrial uptake of approximately $29\%$ of anthropogenic $\text{CO}_2$ emissions driven by a combination of forest regrowth and $\text{CO}_2$ fertilization.

Internal Climate Variability

Natural temperature fluctuations (from year to decadal scales) caused by the internal coupled dynamics of the climate system rather than external forcings like greenhouse gases, volcanoes, or orbital cycles.

El Niño-Southern Oscillation (ENSO)

A coupled ocean-atmosphere phenomenon in the tropical Pacific involving reinforcing feedbacks between surface pressure patterns (Southern Oscillation) and sea surface temperature anomalies (El Niño/La Niña).

Atlantic Multi-decadal Oscillation (AMO)

A large-scale climate oscillation involving the periodic weakening and strengthening of the Atlantic thermohaline circulation, driving multi-decadal warm and cold temperature periods.

Parameterizations

Approximations used in numerical climate models to represent physical processes (such as cloud formation and turbulence) that occur at spatial scales smaller than a single model grid cell.

Radiative Forcing

The net radiation change in $\text{W/m}^2$ imposed at the top of the atmosphere caused by a climate forcing agent, such as greenhouse gases or aerosols, where a positive value induces warming.

Climate Sensitivity

The expected global mean surface temperature warming resulting from an equilibrium doubling of atmospheric $\text{CO}_2$ concentration, amplified beyond the direct radiative effect by internal climate feedbacks.

Water Vapor Feedback

A powerful positive climate feedback where higher temperatures increase atmospheric water vapor via the Clausius-Clapeyron relation, enhancing the greenhouse effect and amplifying warming.

Ice-Albedo Feedback

A positive climate feedback where warming temperatures melt snow and ice, exposing darker surfaces, lowering planetary albedo, and absorbing more solar radiation, leading to polar amplification.

Cloud Feedback

A climate feedback involving complex changes in cloud coverage, height, and optical thickness, acting simultaneously as reflective agents and greenhouse agents; it constitutes the largest source of uncertainty in modern climate models.