The Climate System 8.4 The climate system keeps Earth’s global temperature constant by absorbing energy from the Sun trapping, storing, and transporting this energy from one place to another eventually radiating all the energy back out to space The climate system has four main components: Atmosphere-- Hydrosphere-- Lithosphere-- Biosphere Each component receives energy from the Sun. Each component interacts with the other components. Individual parts of the climate system are continuously changing (e.g., organisms grow, clouds form, ocean currents flow). atmosphere hydrosphere lithosphere

The Climate System 8.4 The atmosphere is made of 78% nitrogen, 21% oxygen, and 1% mixture of other gases. It also contains water vapour and dust. The two lowest parts of the atmosphere are the troposphere and the stratosphere. The atmosphere reflects some of the Sun’s energy, absorbs and radiates some, and transmits some to Earth’s surface. The atmosphere traps lower-energy radiation coming back out from the Earth, keeping Earth warm. The blanket model states that the atmosphere is like a layer of blankets wrapped around Earth, conserving thermal energy to keep Earth warm. atmosphere

8.4 The Climate System Ozone in the Stratosphere Ozone, O3, in the stratosphere prevents most dangerous UV radiation from reaching Earth’s surface. Human-made compounds (CFCs) cause ozone depletion in the stratosphere, which have caused ozone “holes” to form over Antarctica and the Arctic. Due to the Montréal Protocol in 1987, CFCs were banned, and the ozone layer will recover in about 50 years.   Ozone in the Troposphere UV radiation combines with car exhaust to produce smog (toxic chemicals and ozone). This ozone is in the troposphere. It does not move up into the stratosphere, and does not shield us from UV radiation. Smog is harmful to human health, buildings, plants, and animals.

8.4 The Climate System The Hydrosphere Liquid water absorbs energy from warm air and the Sun, and then releases energy back. It also reflects some of the Sun’s energy. Water vapour and clouds reflect, absorb, and transmit the Sun’s energy. Ice reflects about 75% of the Sun’s energy. Because it reflects so much energy, permanent ice plays a vital role in the climate system.   Large Bodies of Water and Climate Zones Recall that large bodies of water are one of the factors affecting climate zones. Water absorbs and stores more thermal energy than land. As a result, large bodies of water affect the climate of nearby regions. hydrosphere A large body of water takes a long time to warm up or cool down. Regions near an ocean or lake tend to be cooler in summer and warmer in the fall. Air passing over unfrozen water in winter absorbs water vapour. Once the air reaches land, the water vapour condenses as snow. Regions downwind from a large body of water have more snowfall in winter.

8.4 The Climate System The Lithosphere The exposed lithosphere absorbs higher-energy radiation from the Sun, converts it into thermal energy, and emits the energy back as lower-energy infrared radiation.   Land Formations, Altitude, and Climate Zones Mountains and other land formations affect how air moves over an area. Altitude affects pressure and temperature. lithosphere As clouds are blown up over mountains, they lose moisture as rain on the windward side. The leeward side of a mountain receives little rain (the rain shadow effect). As air rises, it expands and cools down. At high altitudes, the air is cooler than at low altitudes.

8.4 The Climate System Living Things All organisms are part of the climate system. Plants and animals change the relative amounts of gases in the atmosphere: Through photosynthesis, plants take in CO2 gas and release O2 gas. Through cellular respiration, organisms take in O2 gas and release CO2 gas. Cows and sheep produce CH4 gas as they digest food. Termites and some bacteria also produce CH4 gas. Some gases in the atmosphere (for example, CO2 and CH4) absorb lower-energy radiation emitted by Earth. If the amounts of CO2 and CH4 change, it affects how much radiation the atmosphere can absorb.