Lesson 3.3: Explaining and Predicting Climate Change
Lesson 3.3: Explaining and Predicting Climate Change
This lesson brings you to the final part of Alberta’s geological story. At this time, climate change uncovers a landscape reshaped by geological events. You have learned that Earth's landscape and climate have changed over time. So have the organisms that live on Earth. You have seen that when Earth's environment changes, many species disappear, especially if it is sudden.
The success of humans as a species is based on using knowledge and technology to successfully take advantage of Earth's environment. And just like other species, we may not be able to adapt well to a sudden change in climate.
It is believed that Earth's climate is now quickly changing, and another great extinction event is beginning. It is important to understand the basic ideas about climate in order to understand issues around climate change. That is what this unit is about. The video on the right is a great overview.
- identify a relationship as cause or correlation
- describe the correlation between carbon dioxide in the atmosphere and average temperature.
- differentiate between weather and climate
- define heat budget
- use Figure C3.33 to describe the chanages in Earth's average temperature.
- describe 4 factors that affect how much solar energy Earth receives.
- describe 4 factors that affect where and how much solar energy is absorbs
- describe what the enhanced Greenhouse effect is
- describe how global warming could cause global cooling
- explain why computers are essential to climate prediction
- explain how continental drift could cause climate change.
- Read pages 382 to 384 in the textbook, ending at the investigation. Read and make notes on the following factors affecting Earth's climate.
Solar Radiation Received by Earth
Earths orbit can change in three ways. View "Earths Orbit and Climate"
for a summary. (You will not be tested on the terminology) Earth has
more landmass in the northern hemisphere, and how much radiation is received there plays an important part in Earths climate. The video below gives a detailed explanation.
Dust thrown into the atmosphere by volcanoes or asteroid impacts can block solar radiation for years, changing Earths climate.
The intensity of the sun changes in irregular and in regular ways.
Albedo describes the fraction of solar energy that is reflected back into space, instead of being absorbed. Snow and cloud have high albedos, while dark rock, ocean or plowed fields have low albedos.
Human land use changes albedo and affects climate. Cities and deforestation lower albedo, for example. Climate scientists worry that global warming will lead to a positive feedback effect; warming will cause melting of snow and ice at the poles, changing the albedo and increasing the amount of energy absorbed, so climate will be warmed even more.
Solar Radiation Absorbed by Earth
The tilt of the Earth determines the concentration of solar energy at a latitude. That is what determines the season.
As Earth revolves around the sun, the hemisphere are tilted towards and away from the sun.
Tectonic plates are moving. this changes where the continents are located and how much solar energy they absorb. It changes cloud patterns which affects albedo, and changes the geometry of the oceans so the the global conveyers are improved or inhibited.
Most of the sun's energy falls at the equator. Ocean currents redistribute this energy to the poles. In general, this cools the equator and warms the poles. Cold, salty water flows towards the equator to replace the water moving to the poles.
Locally, the climate of coastal locations is greatly affected by warm or cold ocean currents.
As sea ice freezes at the poles salt is 'squeezed out' of it, making cold dense water that sinks to the ocean floor. Surface water is pulled to replace it. This is the pump that drives the global conveyor. Climate scientist fear a negative feedback effect where global warming stops the formation of sea ice, stopping the global conveyor so the poles freeze and Earth enters another glaciation. (Like the movie The Day After tomorrow)
Solar energy is absorbed by Earth and re-emitted as infrared energy. Certain gases in the atmosphere will absorb the infrared energy and re-emit half of it back to Earth. You may have noticed that a night with a clear sky is colder than one with a cloudy sky; that is because water vapour is a greenhouse gas, and clouds (water vapour) re-emit energy back to Earth, making it warmer.
The 'Greenhouse' effect is natural and necessary, but an enhances greenhouse effect will cause climate change.
There are several other greenhouse gases, like nitrous oxide, and methane, but the one that is talked about the most is carbon dioxide.
Only a very small fraction of Earth's atmosphere is carbon dioxide, but it seems to significantly change Earth's heat budget. Humans seem to be increasing carbon dioxide in the atmosphere by using fossil fuels (coal, oil, natural gas) and making cement.
(more information if you like)
- Read the investigation on page 387 of the textbook. Follow the directions, and answer the questions.
Answers are below.
- Read page 388 of the textbook.
- Read the investigation on page 389 of the textbook. View "North Atlantic Conveyor". Follow the directions, and answer the questions.
- Read “3.3 Summary” on page 389 of the textbook. Use the Lesson 3.3 Targets to test your knowledge.