Unit 6: Climate Change

Introduction

This unit explores the scientific concepts of climate change, its causes and effects, and the impact of human activities. It also discusses the effects of climate change on living things and elaborates on measures to combat climate change.

Definition and Key Concepts

Definition of Climate Change

• Climate change is the global phenomenon of climate transformation characterized by changes in the usual climate of the planet (temperature, precipitation, and wind) over long periods, especially those caused by human activities.

• It is a systematic change in the long-term state of the atmosphere over multiple decades or longer.

Keyword: Climate change is a long-term change in the earth’s climate, especially a change due to an increase in the average atmospheric temperature.

Causes of Climate Change

Human Activities and Greenhouse Gases

• Humans influence the climate by increasing the earth’s temperature through activities such as burning fossil fuels, cutting down forests, and other activities that increase atmospheric CO2 levels.

• Over half of the increase in atmospheric CO2 since 1970 is due to human activities.

• These activities enhance the greenhouse effect and global warming.

Greenhouse Effect

• Greenhouse gases (GHGs) are gases in the earth’s atmosphere that trap heat. Major GHGs include carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).

• These gases allow sunlight to enter the atmosphere and warm the earth’s surface, but they trap heat that is radiated back from the earth, preventing it from escaping into space.

• This process keeps the earth’s average temperature at about 14°C (57°F), which is suitable for life. Without the greenhouse effect, the earth would be much colder (about -18°C or 0°F).

Major Greenhouse Gases and Their Sources

The following table summarizes the main greenhouse gases and their major sources:

Role of Carbon Dioxide (CO2)

• CO2 is the greenhouse gas responsible for the greatest amount of warming to date.

• It is released from the incomplete combustion of fossil fuels (coal, oil, gas) and from deforestation, transportation, and industrial processes.

• CO2 absorbs less heat per molecule than methane or nitrous oxide, but it is more abundant and remains in the atmosphere longer.

• CO2 is responsible for about two-thirds of the total energy imbalance causing the earth’s temperature to rise.

Trends in Atmospheric CO2

• There has been a progressive increase in atmospheric CO2 concentrations since 1750, as shown in Figure 6.2 (not displayed here).

• This increase is closely linked to industrialization and the burning of fossil fuels.

Effects of Climate Change

• Climate change affects weather patterns, sea levels, and biodiversity.

• It can lead to more frequent and severe weather events, such as hurricanes, droughts, and floods.

• Changes in climate can impact agriculture, water resources, and human health.

Discussion and Reflection

• Students are encouraged to discuss the differences between weather, climate, climate variability, and climate change.

• Reflect on how human activities contribute to climate change and what measures can be taken to combat it.

Key Terms

• Climate change: Long-term alteration of temperature and typical weather patterns in a place.

• Greenhouse gases (GHGs): Gases that trap heat in the atmosphere, contributing to the greenhouse effect.

• Greenhouse effect: The process by which radiation from a planet's atmosphere warms the planet's surface.

• Global warming: The ongoing rise in global average temperature near Earth's surface.

Example

• Example: The increase in atmospheric CO2 from burning fossil fuels since the Industrial Revolution has led to a measurable rise in global temperatures.

Self-Questioning

• What is the difference between global warming and climate change?

Additional info: The notes have been expanded to provide clear definitions, context, and examples suitable for college-level General Biology students. The table of greenhouse gases and their sources has been reconstructed for clarity.