Unit 1 – Climate Change

Unit 1 – Climate Change

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Key Terms• The atmosphere is a layer of gases that

surround the Earth. Without it our days would be too hot and our nights too cold.

• Weather is the condition of the atmosphere in a specific place at a specific time. It describes factors such as wind, temperature and moisture.

• Climate refers to the condition of the atmosphere over a large area, averaged over many years.

Is climate change new?Climate change is a natural part of Earth’s history. For example, thousands of years ago, thick ice sheets covered most of Canada and a large portion of the United States.

1. The Sun 2. The Earth

3. The Atmosphere 4. The Hydrosphere

5. Moving Continents 6. Human Activity

Factors Affecting Climate Change





Climate Change and Solar EnergyThe most important factor that affects the climate on Earth is the Sun.

Solar energy travels through space as heat and light.The intensity of the energy that reaches Earth’s surface affects the temperature of air, water and land on the planet. Heat produces winds, rain and other features of climate.The amount of solar energy that reaches Earth depends on solar activity, the shape of the Earth and the tilt of the Earth.

The Sun produces a variable amount of energy. When the number of sunspots is high, the Sun emits higher amounts of solar radiation. Some scientists believe that changes in solar output are the main cause of climate change in the past.

Changes in Solar Activity





Factors on Earth that Affect Climate

1.Rotation2.Revolution3.Tilt4.Wobble5.Latitude

Rotation vs Revolution

• Earth rotates once every 24 hours around its axis, an imaginary line that goes from the North Pole to the South Pole through the center of the Earth.

• Another important detail is that the Earth’s axis of rotation is tilted at an angle of about 23.5o perpendicular to the orbital plane.

• The Earth also revolves (orbits) around the Sun over a 365 day period (1 year).

Movements of Earth in Space

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The seasons are created by Earth’s revolution and its tilted axis.

Earth’s Seasons

Eccentricity Earth’s orbit fluctuates due to the gravitational attraction of other planets in the solar system. Its path around the Sun changes very slowly from elliptical to circular. This affects the intensity of the Seasons. It does not explain all of the recent changes that have been observed and measured.

elliptical orbit – planet receives more solar radiation when near the Sun than it does when it is farthest from the Sun circular orbit – amount of solar radiation varies less throughout the year

Earths Orbit (Revolution)

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Does every point on Earth rotate at the same speed?

Do the poles rotate at the same speed as the equator?

Earth’s Tilt and Climate

The Earth’s tilt changes slightly over time. The greater the tilt the greater the differences in temperature between summer and winter.

Earth is not a perfect sphere. It wobbles slightly as it rotates on its axis.

The wobble affects the intensity of solar energy that is received by the northern and southern hemispheres at different times of the year.

This causes the changes in temperature between the seasons.

Effect of Latitude on Climate and SeasonsThe sun’s rays are most intense at the equator, where they hit the Earth perpendicular to its surface.

At latitude of 45 o south, the Sun’s rays strike the Earth’s surface at an angle and as a result the rays are spread over a larger area. The Earth here receives less solar energy because it is more spread out.

As the Sun’s position in the sky lowers the sunlight received decreases.

At the poles, the Sun’s rays are spread out over an even larger area.





Atmospheric Factors that Affect Climate

1.Greenhouse Effect2.Wind

How the Atmosphere Affects ClimateThe atmosphere starts at Earth’s surface and goes up to about 560 km into space.

It is mostly made of nitrogen (N2) and oxygen (O2) gases as well as water vapour, very low concentrations of other gases and particles of solids.

The amount of energy that reaches the Earth from the Sun, called the solar constant, is 1367 J/m2/s. What this means is that every square

metre on Earths surface receives 1367 J of energy every second. (average)

The Greenhouse Effect

Define the greenhouse effect.

The greenhouse effect is a natural process that keeps Earth’s temperatures within a certain range. Without it Earth would be colder (34oC lower) and most of the solar energy reaching Earth would radiate out back into space.

absorbed emittedthermal energy atmosphere Earth’s surface thermal energy

The Greenhouse EffectThe greenhouse effect is the natural warming caused when gases in Earth’s atmosphere absorb thermal energy that is radiated by the Sun and Earth.

The atmosphere contains greenhouse gases and solar radiation passes through them. Solar radiation warms the surface of the Earth and heat rises from the surf

Some heat is able to pass back through the gases and some cannot. The heat that is trapped adds to overall global temperatures.

Winds and EnergyWind is the movement of air from an area of high pressure to an area of lower pressure. The air moves as wind transfers thermal energy around the world from warm areas to cooler areas.

The movement of air affects: • ocean currents• precipitation patternsWind is caused by uneven heating of Earth’s surface.wind moves energy from warm cool areasair moves from high pressure low pressureair moves from warm cool areas

*** Winds disperse energy through the atmosphere.

Winds and Ocean CurrentsWhen winds blow, energy is transferred to the surface of the ocean and causes the water to move in surface ocean currents.

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Since oceans absorb energy from the Sun, the movement of water transfers heat around the Earth’s surface.

Prevailing WindsWinds blow in fairly constant directions around the world. These are known as prevailing winds.

Winds Affect PrecipitationAs air masses of different densities move across the Earth’s surface, they interact. When air masses meet (called a front), one air mass usually rises over the other. The rising air cools and any water vapour in the air condenses to form precipitation.

Winds also affect precipitation through jet streams. Jet streams are high-altitude winds that travel long distances at very high speeds.

These winds may carry warm, moist air, which can produce precipitation in areas from the origin of the jet stream. They may also carry dry, cool air, which causes dry weather in areas affected by the jet stream. Canada’s weather is mostly influenced by the polar jet stream.





How the Hydrosphere Affects ClimateTwo thirds of the Earth is covered by oceans.

• The hydrosphere includes all of the water on the planet in its different forms. With the atmosphere, water transfers heat from one part of the planet to another.

Water is found in many forms:

• vapour and clouds of water droplets in the atmosphere

• ice and snow in temperate and colder regions

How the Hydrosphere Affects Climate• Oceans and lakes act as heat reservoirs. They buffer

temperatures in the atmosphere.

• The oceans can hold a lot more heat than the atmosphere can. The top 2.3 metres of the oceans hold as much heat as all of the air on the planet.

• Large bodies of water influence climate because water has a large specific heat capacity compared with other substances.

Specific Heat Capacity• Specific heat capacity is the amount of heat required to raise the

temperature of one gram of a substance by one degree Celsius. • Water has a large specific heat capacity. This means it takes more

heat to raise the temperature of 1 g of water by 1oC than it does to do the same to many other substances.

• The higher the heat capacity, the longer it takes to warm the substance up and the slower the substance loses its heat. Water’s high specific heat capacity means that a land mass near a large body of water will have its temperature “moderated” by the water – it will warm up more slowly in summer and cool down slowly in winter than will a land mass further from water.

Temperature Result:• large bodies of water change slowly and by small amounts• land masses change more quickly and by large amounts

Specific Heat CapacitySome Common Specific Heat Capacity Values

Substance Specific Heat Capacity in “The number of joules of heat energy needed to raise the temperature of 1 g of the substance by 1oC.”

Pure Water 4.18

Sea Water 3.89

Dry Air 1.00

Wet mud 2.51

Sandy soil 0.92

Ice and Snow Reflect Heat• The light colour of ice and snow allow them to reflect solar radiation.

The amount of energy that is reflected by a surface is known as albedo.

• Light-coloured surfaces reflect energy, and dark surfaces absorb energy.

Example:

• Because of their large differences in albedo, the distribution of water, ice and land on Earth’s surface greatly affects the average global temperature.





How Moving Continents Affect Climate• Earth’s outer layer is made of massive pieces of

solid rock, called tectonic plates. Earth has about 12 major plates that move at a rate of a few centimeters per year.

• The plates carry the continents with them as they move. This means that the shape of the oceans and continents is always changing.

• Patterns of air and water circulation are affected which in turn affects the thermal energy around the world. The formation of mountain chains also affects the patterns of wind and precipitation around the globe.

Uplift and Weathering

Upthrusting mountain ranges expose minerals to weathering. (Weathering is the breaking down of Earth's rocks, soils and minerals through direct contact with the planet's atmosphere. ) The exposed minerals change chemically into carbonates. This process removes carbon dioxide from the atmosphere and cools the Earth.

Volcanic Eruptions• Most volcanoes are located at the boundaries of

tectonic plates. Plate movement affects climate by producing volcanic activity. In these areas, molten rock and gases from below the Earth’s crust rise up through cracks in the rock and spew into the air as volcanic eruptions.

• Particles called aerosols (such as ash) are released into the atmosphere.

Aerosols:• reflect solar radiation and have a cooling effect on the

global climate

• scatter light• Some volcanic eruptions can raise global

temperatures by releasing greenhouse gases.





How Human Activity Affects Climate

Many human technologies burn fossil fuels (coal, oil and natural gas). Since the late 1700s they have been affecting our atmosphere, each time a new machine was invented. During the Industrial Revolution, many new machines requiring fossil fuel power were invented.

What are some examples of technologies that use fossil fuels?

When fossil fuels are burned to release energy, they release gases and other pollutants into the atmosphere as waste produces. Many of these gases affect the natural processes that produce the greenhouse effect.

Burning of Fossil Fuels

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Unit 1 – Climate Change