The Greenhouse Effect and Global Warming: Causes and Consequences

The natural greenhouse effect

The greenhouse effect is a natural process that warms the Earth's surface. Short-wave radiation from the Sun passes through the atmosphere and warms the Earth's surface. The warm surface emits long-wave infrared radiation back toward space.

Greenhouse gases in the atmosphere, including carbon dioxide (CO₂), methane (CH₄) and water vapour, absorb some of this outgoing infrared radiation and re-emit it in all directions, including back toward the surface. This keeps the Earth about 33 degrees C warmer than it would otherwise be, making life possible.

The enhanced greenhouse effect

Human activities are increasing the concentration of greenhouse gases in the atmosphere:

Burning fossil fuels (coal, oil, natural gas) for energy, transport and industry releases CO₂. Deforestation reduces the number of trees absorbing CO₂ through photosynthesis, and burning the trees releases stored carbon. Agriculture produces methane from rice paddies and livestock (cattle produce methane during digestion), and nitrous oxide from fertilised soils.

The increased concentration of greenhouse gases traps more infrared radiation, raising the average global temperature. This is the enhanced greenhouse effect, leading to global warming.

Consequences of global warming

Rising sea levels: Thermal expansion of ocean water and melting of polar ice caps and glaciers cause sea levels to rise, flooding low-lying coastal areas and threatening island nations.

Changes in weather patterns: More extreme weather events including more intense storms, droughts and floods. Changes in rainfall distribution affect agriculture and water supplies.

Habitat loss and species extinction: As temperatures change, habitats shift faster than many species can migrate or adapt. Coral reefs are damaged by warmer, more acidic oceans (ocean acidification). Polar species lose habitat as ice melts.

Effects on agriculture: Changing temperatures and rainfall patterns alter growing seasons and crop yields. Some regions may become too dry for current crops while others may become suitable for new ones.

Reducing the enhanced greenhouse effect

Strategies include: reducing fossil fuel use by switching to renewable energy sources (solar, wind, hydroelectric), improving energy efficiency, reducing deforestation and increasing reforestation, reducing methane emissions from agriculture, and developing carbon capture technologies.

International agreements such as the Paris Agreement set targets for reducing greenhouse gas emissions. Individual actions such as reducing energy use, eating less meat and choosing sustainable transport also contribute.