Global Warming: Understanding Causes and Scientific Evidence

Climate Change: Causes, Evidence, and Controversy

Defining Climate Change

Climate change is a long-term shift in the Earth's climate, especially a change due to an increase in the average atmospheric temperature.

The Climate Change Debate

The discussion surrounding climate change often involves differing viewpoints:

Scientific Consensus vs. Skepticism

• Scientific View: Climate scientists assert there is strong proof that humans are causing climate change. Evidence includes rising temperatures, melting polar ice, and increased extreme weather events (like floods and heatwaves). These indicators suggest that human activities, such as burning fossil fuels, are harming the planet.
• Alternative Views: Some politicians and groups do not fully agree. They suggest climate change might be primarily part of natural cycles and not mainly caused by humans. Others express concern that mitigating climate change could be too expensive or detrimental to the economy.

These different opinions significantly influence policy making and subsequent actions.

Evidence and Indicators of Global Warming

Temperature Data (Referencing Graph A)

Data, as shown in Graph A, indicates that the planet's average temperature is rising, increasing by 0.8ºC over the past 100 years. Most of this warming occurred in the past 35 years, with 16 of the 17 warmest years on record occurring since 2001. The warmest year on record was 2016.

Two Key Indicators of Global Warming

• Melting Ice: Glaciers are shrinking because the Earth is heating up.
• Rising Sea Levels: The sea level has risen approximately 10 to 20 cm in the last 100 years. This is due to melting ice and the thermal expansion of water as it warms.

Understanding the Greenhouse Effect

Definition of the Greenhouse Effect

The greenhouse effect is the natural warming of the atmosphere that occurs when heat given off from the Earth is absorbed by liquids and gases, such as carbon dioxide.

Sources of Greenhouse Gases

Natural Causes

A greenhouse gas is any gas in the atmosphere that traps heat. The main natural gases include carbon dioxide, methane, water vapor, and nitrous oxide.

• Water Vapor: This is the most abundant gas in the atmosphere and occurs naturally as part of the water cycle.
• Carbon Dioxide: Emitted naturally by erupting volcanoes, soil, and natural vegetation.
• Methane: Released in low-oxygen environments, such as the roots of certain plants.

Anthropogenic (Human) Causes

Human activity is thickening the "greenhouse blanket." As the world population grows, so does the demand for energy, transport, and food.

• Industrial Emissions: Power stations, factories, homes, and cars burn fossil fuels (coal, oil, and natural gas, which are mined from rock layers).
• Synthetic Chemicals: Chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs) are entirely man-made.
• Deforestation: Forests absorb greenhouse gases, but people are cutting them down or burning them, which releases more carbon dioxide.
• Agriculture: Food production (especially livestock) releases methane.

Mechanism of the Greenhouse Effect (Referencing Diagram A)

As illustrated in Diagram A, the greenhouse effect mechanism shows that solar radiation often reflects back into space. However, gases created by human activity trap this heat, preventing it from escaping the atmosphere.