ENVS200-wk11.1

Earth's Energy Budget

• Energy Inputs and Outputs

  • Earth's energy budget involves the balance of energy received from the Sun and the energy re-radiated back into space.

  • Energy inputs = energy outputs (in balance).

  • The same amount of energy that enters Earth's atmosphere is eventually re-radiated back out to space.

Student Learning Objectives

• By the end of this week, students will be able to:

  • Explain how the atmosphere is heated.

  • Outline Earth's energy budget.

  • Differentiate between incoming and outgoing radiation.

  • Describe why Earth's surface only receives a portion of incoming radiation from the Sun.

  • Explain how (and if) Earth's energy budget is balanced.

  • Define the Greenhouse Effect.

  • List the main Greenhouse Gases (GHGs) and explain their influence on atmospheric temperatures.

Reducing Air Pollution

• Laws and Standards

  • Enact, regulate, and enforce environmental laws and standards to reduce air pollution.

  • Strengthening laws can include:

    • Prevention measures.

    • Further reduction and control of emissions.

    • Setting stricter regulations.

    • Emissions trading authorization, based on initial cap settings and frequency of adjustment.

Reducing Outdoor Air Pollution: Clean Air Acts

• Major Acts: Clean Air Acts of 1970, 1977, and 1990.

• EPA Regulation

  • EPA regulates six major pollutants:

    • Carbon monoxide (CO)

    • Nitrogen dioxide (NO2)

    • Sulfur dioxide (SO2)

    • Suspended particulate matter (< PM10)

    • Ozone (O3)

    • Lead (Pb)

• Established emission standards for 188 hazardous air pollutants (HAPs).

Reducing Outdoor Air Pollution: Achievements

• Emission reductions under the Clean Air Acts led to a 67% decrease in major pollutants from 1980-2012, despite increases in population and economic factors.

Emissions Trading

• Mechanism of Trading

  • Between 1990 and 2012, emissions trading reduced SO2 emissions from power plants by 76% in the U.S.

  • Plants are allotted pollution credits, allowing exchanges between plants.

• Controversies

  • Proponents argue emissions trading is cheaper and more efficient than regulation (by ~90%).

  • Critics argue it allows over-polluting plants to avoid necessary improvements.

Reducing Indoor Air Pollution

• Methods

  • Transition from open fires and poorly vented stoves to efficient, well-vented stoves and solar cookers, particularly in less-developed countries.

  • Ban indoor smoking and enhance air circulation in buildings.

  • Set stricter emissions standards for indoor products and promote naturally-based cleaning products.

Solar Radiation

• Defined as the energy emitted by the Sun traveling outward in all directions, impacting only half of the Earth's surface at any given time.

Understanding Earth's Energy Budget

• Earth’s energy budget reflects:

  • Incoming solar radiation is shortwave radiation.

  • Some energy is absorbed by the Earth's surface and some is re-radiated back to space as longwave infrared radiation, contributing to atmospheric heating.

Albedo Effect

• Definition

  • Albedo is the measure of a surface's reflectivity from 0 to 1.

  • Albedo of 1 reflects all light (white surfaces), whereas 0 absorbs all light (black surfaces).

  • Earth's average albedo is approximately 0.3, implying 30% of incoming light is reflected without absorption.

Outgoing Longwave Radiation

• Net upward emission of energy involves:

  • Heat flow from the Earth's surface upwards into the atmosphere.

  • Heat flow from the atmosphere downwards back to the Earth's surface.

  • Total energy emitted comprises contributions from the surface, atmosphere, and clouds.

The Greenhouse Effect

• Description

  • The greenhouse effect analogy compares the Earth's atmosphere to a greenhouse that allows sunlight to warm the surface but traps heat.

  • Major greenhouse gases include:

    • Carbon dioxide (CO2)

    • Methane (CH4)

    • Nitrous oxide (N2O)

    • Water vapor (H2O)

    • Ozone (O3)

• Greenhouse gases absorb outgoing longwave radiation, re-emitting it and warming the atmosphere further.

Implications of the Greenhouse Effect

• Without the greenhouse effect, Earth's average temperature would be -18°C (0°F), but it is currently around 15°C (60°F).

• The increase in greenhouse gases due to human activities leads to anthropogenic climate change.

Weather vs. Climate

• Definitions

  • Weather: Atmospheric conditions at a specific time and place.

  • Climate: Long-term average of weather patterns in a location, determined by a minimum of 30 years of data.