IB Environmental systems and societies 6.1 Introduction to the Atmosphere Key Definitions

Aerosols are tiny solid or liquid particles suspended in the atmosphere.

Albedo refers to how much solar energy is reflected by the Earth's surface.

Anthropocene means “the age of humans”, emphasizing the unprecedented role humans play in altering Earth’s geology, atmosphere, and biosphere.

A biome is a group of ecosystems that share similar climatic conditions, regardless of their geographic location.

A dynamic atmospheric system is one in which gases, energy, and particles are continuously transformed and redistributed through interacting physical and chemical processes.

The enhanced greenhouse effect refers to additional warming caused by increased concentrations of greenhouse gases from human activities.

The greenhouse effect is a natural warming process where greenhouse gases absorb and re-emit infrared radiation, preventing heat from escaping into space.

Greenhouse gases are atmospheric gases that absorb infrared radiation emitted from the Earth’s surface and re-radiate it back, contributing to atmospheric warming.

The Hadley cell is the largest and strongest atmospheric circulation cell, driven by intense heating at the equator and responsible for tropical climates and the formation of deserts in the subtropics.

Milankovitch cycles are long-term variations in Earth’s orbital geometry and axial behaviour that alter solar radiation distribution and drive natural climate cycles such as ice ages and interglacial warm periods.

Obliquity refers to the angle of Earth’s axial tilt, which determines how strongly sunlight is concentrated at different latitudes.

The ozone layer is a concentration of ozone molecules located in the stratosphere that protects living organisms from harmful ultraviolet radiation.

The pre-biotic atmosphere refers to Earth’s early atmosphere before life evolved, dominated by CO₂, methane, and nitrogen, and lacking oxygen.

Pressure gradient force is the force that drives air movement due to differences in atmospheric pressure.

The Quaternary Period is the geological time span from 2.58 million years ago to the present, marked by repeated cycles of glaciation and interglacial warming.

Radiative forcing describes how different factors, such as GHGs, aerosols, and albedo, alter the balance of heat in Earth’s atmosphere.

The standard lapse rate refers to the rate of temperature decrease with height.

The tricellular model of atmospheric circulation explains the global movement of air and how it influences temperature, precipitation, and the distribution of biomes.