6.1 Introduction to the Atmosphere

How much of the atmosphere is composed of nitrogen and oxygen?

78% nitrogen 21% oxygen

What are the other gases in the atmosphere?

• CO2

• Argon

• Water vapour

• Methane, ozone

What are layers of atmosphere divided into based on?

Temperature changes

What are the atmospheric layers where most interactions related to living systems occur?

At troposphere and stratosphere

What is the lowest layer of the atmosphere?

Troposphere- 10km

Describe the troposphere

Where weather phenomena occurs e.g. cloud formation, precipitation, mixing of gases

What’s the second lowest layer?

Stratosphere (10 to 50km)

Describe the stratosphere

• Contains ozone layer

• High concentration of ozone that absorb and block most of the sun’s harmful UV

Why is the ozone layer crucial?

Protecting life on earth from excessive UV radiation

What are the reactions in the troposphere?

Chemical reactions involving pollutants, greenhouse gases and atmospheric particles can impact air quality and climate

What are the reactions in the stratosphere?

Chemical reactions involving ozone play vital role in maintaining ozone layer and protecting earth from harmful UV radiation

What are the storages in the atmosphere?

• Storage for gases (greenhouse gases)

What are the flows in an atmospheric system?

• Flows of gases and particles

• Driven by air currents, weather patterns and atmospheric circulation

• Contribute to movement and redistribution of gases

What are the inputs of the atmospheric system?

• Natural inputs: gases from volcanic eruptions, gas emissions from plants and others living organisms, dust particles from desert regions

• Anthropogenic inputs from human activities (release of greenhouse gases, air pollutants from industrial processes, aerosols from combustion)

What are the outputs of the atmospheric system?

• Releases gases by respiration / photosynthesis

• Pollutants and aerosols can be removed through precipitation, dry deposition and chemical reactions

What are the exchanges with other earth systems?

• Biosphere (plants, animals, microorganisms)

• Hydrosphere (oceans, lakes, rivers)

• Lithosphere (landmasses, rocks)

Why is exchanging gases important?

Shaping climate patterns and weather events

Why has the composition of the atmosphere changed over time?

• Atmosphere had high levels of CO2, lacked oxygen in early stages

• Millions of years, photosynthetic organism evolved, released oxygen

• Volcanic activity, meteorite impacts have influenced atmospheric composition

Where do clouds form?

Troposphere

What is this layer characterised by?

• Decreasing temperature

• Increasing altitude

• Cooling + condensation of water vapour

What contributes to the albedo effect?

Clouds

Define albedo

Reflectivity of a surface, indicating how much solar radiation reflected back into space

What does this reflection of solar radiation help with?

Cool the Earth’s surface

How can clouds act as a feedback mechanism?

• Low clouds: net cooling effect by reflecting more sunlight

• High clouds: net warming effect by trapping more outgoing IR

What can affect cloud formation?

• Aerosol pollution

• Changes in atmospheric circulation patterns

• Climate change

What are the gases affected by human activity?

• Ozone

• Carbon dioxide

• Water vapour

• Methane

• Nitrous oxide

• Aerosols

What human activity affects ozone?

• Release of ozone-depleting substances e.g. CFCs (aerosols, refrigerants, pesticides) reduces ozone

What is the effect of depleting ozone?

Increases UV radiation reaching earth’s surface, harming organisms (phytoplankton, plants, humans)

What human activity affects carbon dioxide?

Burning fossil fuels, deforestation and industrial processes increase carbon dioxide

What is the effect of CO2?

Enhances greenhouse effect, leading to global warming and climate change, affecting ecosystems and biodiversity

What human activity affects water vapour?

Land use changes, agriculture, industrial processes

What is the effect of water vapour?

• Alters precipitation patterns

• Contribute to droughts, excessive rainfall

• Impact ecosystems, agriculture, water availability

What human activity affects methane?

• Agriculture

• Fossil fuel extraction

• Waste management

What is the effect of methane?

Enhances greenhouse effect, leading to global warming and climate change

- Melts permafrost, ice caps

- Contributes to sea-level rise

What is the human activity affecting nitrous oxide?

• Agriculture

• Combustion processes

• Industrial activities

What is the effect of nitrous oxide?

Contributes to global warming and climate change, affects air quality

What is the human activity on aerosols?

Produced by industrial processes, biomass, burning and vehicle emissions

What is the effect of aerosols?

• Alters radiative properties of atmosphere

• Affects air quality

• Influence cloud formation

• Impact ecosystems and human health

What form of energy does sun emit?

Solar radiation, including visible light and UV

What happens to solar radiation when it reaches the Earth’s atmosphere?

• Some thermal energy is reflected from the earth’s surface

• Most thermal energy is absorbed and re-emitted by the earth’s surface

What happens to the thermal energy after being re-emitted from the surface?

• Some thermal energy passes straight through the atmosphere and is emitted into space

• Some thermal energy is absorbed by greenhouse gases and re-emitted in all directions

What are the main greenhouse gases?

Carbon dioxide, methane, water vapour

How do greenhouse gases affect Earth’s thermal energy?

They act like a blanket, allowing sunlight to pass through but prevent significant amount of IR from escaping back into space

What is the result of greenhouse gases trapping IR?

Reduces thermal energy lost to space and keeps the earth warm

What is the greenhouse effect?

The process where greenhouse gases trap heat within the Earth’s atmosphere keeping the planet warm

Why is the greenhouse effect important?

• Ensures Earth is warm enough for life

• Without it, the Earth would experience dramatic temperature fluctuations

• Planet would be uninhabitable without insulating effect of greenhouse gases