Global Warming and Climate Change

Greenhouse Gases Overview

Two key greenhouse gases are carbon dioxide (CO₂) and methane (CH₄).

• Carbon dioxide (CO₂) is released mainly by burning fossil fuels (coal, oil, gas) in power stations, vehicles, and industry. It is also produced by respiration and volcanic activity.
• Methane (CH₄) is produced by natural processes such as decomposition of organic matter in wetlands and by human activities like livestock farming (especially cows), rice paddies, and landfill sites.

Both gases are present naturally in the atmosphere but human activities have increased their concentrations significantly.

These gases trap heat in the Earth’s atmosphere, helping to keep the planet warm enough to support life.

Other greenhouse gases such as nitrous oxide and water vapour also contribute to the greenhouse effect, though they are less emphasized at GCSE level.

Greenhouse Effect

The greenhouse effect is the process by which greenhouse gases absorb infrared radiation (heat) emitted by the Earth’s surface and re-radiate it back, warming the atmosphere.

Without this natural effect, the Earth would be too cold for life as we know it, with an average temperature around −18°C instead of the current +15°C.

However, human activities have enhanced this effect by increasing greenhouse gas levels, causing more heat to be trapped. This is called the enhanced greenhouse effect and leads to global warming.

The main greenhouse gases involved are:

• Carbon dioxide (CO₂) – most significant due to large emissions from burning fossil fuels.
• Methane (CH₄) – more effective at trapping heat per molecule but present in smaller amounts.
• Other gases like water vapour and nitrous oxide also contribute but are less covered at GCSE level.

The greenhouse gases absorb infrared radiation because their molecular vibrations change when they absorb energy, unlike nitrogen and oxygen which make up most of the atmosphere but do not absorb infrared.

For instance, CO₂ molecules absorb infrared radiation emitted by the Earth’s surface and then re-emit it in all directions, including back towards the surface, raising the temperature.

Global Warming and Climate Change

Global warming refers to the long-term increase in Earth’s average surface temperature due to the enhanced greenhouse effect.

This warming causes changes in climate patterns, known as climate change, which include:

• More frequent and intense heatwaves.
• Changes in rainfall patterns, causing droughts in some areas and flooding in others.
• Melting of polar ice caps and glaciers, contributing to rising sea levels.
• Disruption of ecosystems and habitats, affecting wildlife and agriculture.

Melting ice caps reduce the Earth's albedo (reflectivity), meaning less sunlight is reflected back into space, which further increases warming in a feedback loop.

For example, the Arctic sea ice has been shrinking over recent decades, contributing to rising sea levels that threaten low-lying coastal areas in the UK and worldwide.

Reducing Carbon Footprint

Reducing the carbon footprint means lowering the amount of greenhouse gases released into the atmosphere.

• Renewable energy use: Using energy sources like wind, solar, and hydroelectric power reduces CO₂ emissions because they do not burn fossil fuels.
• Energy efficiency: Improving insulation, using energy-saving appliances, and switching off unused electrical devices reduce energy consumption and CO₂ emissions.
• Reducing methane emissions: Methane can be reduced by better management of landfill sites (capturing methane gas), improving livestock farming techniques, and reducing food waste.

These steps help slow down global warming and lessen climate change impacts.

For example, switching from petrol cars to electric vehicles reduces CO₂ emissions from transport.

Example inline calculation: If the concentration of CO₂ in the atmosphere rises from 0.03% to 0.04%, by what percentage has it increased? Percentage increase = ((0.04 - 0.03) / 0.03) × 100 = 33.3%