Climate
A summary of the weather in a particular region over a period of at least ten years, but more commonly defined over 20 - 30 years. The climate describes both the average weather conditions (for example temperature, rain, snow and wind) in a particular region as well as the extremes.
Internal variability
A change in one of the components of the climate, not caused by an external factor such as a change in the Sun’s activity, that causes wider climate changes. An example of internal variability is El Niño, a warming cycle in the Pacific Ocean which has a big impact on the global climate.
El Nino/La Nina
A warming and cooling cycle of the Pacific Ocean off the coast of South America that occurs about two to three times per decade. The changes in ocean temperature affect weather patterns around the world. When the ocean is warm it is known as El Niño, meaning ‘the boy’ in Spanish, and when it cools it is known as La Niña or ‘the girl’.
Global warming
An increase in the global average temperature at the Earth’s surface. Global warming can have both natural and human causes.
Global warming is commonly used to refer to the warming effect of increased amounts of greenhouse gases emitted by human activities into the atmosphere.
Sunspot
A small visibly dark area on the surface of the Sun caused by changes in the Sun’s magnetic field. The number of sunspots on the Sun’s surface varies over time. There is evidence that past changes in the Earth’s climate are linked to changes in sunspot activity.
Satellite
Any object in orbit around a larger body. Satellites can be natural – such as the Moon – but more often the term is used to refer to an object made by humans which is orbiting the Earth. Scientists use these satellites to collect data about the Earth, its weather and its climate.
Solar energy
Energy given out by the Sun. Solar energy mainly comprises visible and ultraviolet energy, but also includes smaller amounts of infrared energy.
Lava
Hot, melted rock that has been ejected by volcanic activity onto the Earth’s surface. It differs from magma, which is hot, melted rock below the Earth’s surface.
Carbon dioxide
An important greenhouse gas, with the chemical formula CO2. After water vapour, carbon dioxide is the biggest contributor to the greenhouse effect.
Aerosols
Tiny particles in the atmosphere which affect the climate by scattering sunlight or helping clouds to form. Aerosols can be liquid or solid. They occur naturally, for example in dust from volcanic eruptions or sea spray, and also as a result of human activities, such as those producing smoke or other kinds of air pollution.
Ice age
A period of time during which the Earth’s average temperature is reduced. Polar ice caps and glaciers grow in size and global sea levels fall dramatically. The world began to emerge from the last ice age about 22,000 years ago and reached the current warm conditions about 12,000 years ago.
Feedback
A process with two interconnected factors whereby the first factor affects the second, and the change in the second factor in turn affects the first. This can either increase the rate of the process (positive feedback) or decrease it (negative feedback).
An example of a positive feedback process is the melting of ice floating on an ocean. When the local temperature increases it melts the ice and reveals the dark ocean underneath. The ocean absorbs more of the Sun’s energy than the ice, causing the local temperature to increase further and leading to even more melting.
