2.1.3 Enhanced Greenhouse Effect Notes

Human-induced Emissions Are Increasing

Emission Trends Reflect Industrialization and Urbanization

1. The anthropogenic greenhouse emissions include variety of gasses with carbon dioxide accounting for ~75% of human-induced emissions.
2. The CO₂ emissions have been increasing since the beginning of the Industrial Revolution.
3. Originally most of the CO₂ emissions came from HICs - in 1980 the US and Europe constituted two thirds of the emissions.
4. Since the end of the 20th Century the emissions have significantly increased in Asian RICs and emerging economies while they have declined in some HICs (especially in the EU).
5. Now the largest emitters are: China (31%), the US (13%), India (8%), and the EU (6%)

Emissions Pattern Reflects Global Shift in Demographic and Economic Processes

1. The CO₂ emissions are influenced mostly by:
   1. The Size of the Population: More demand for energy and food leads to higher levels of emissions.
   2. The Amount of Energy Used per Person: This reflects the level of socio-economic development.
   3. The Energy Mix: Using more nuclear and renewable energy allows for reducing emissions.
2. Consequently, the largest emitters per capita are still HICs, especially the ones relying on fossil fuels and remaining energy inefficient, e.g. Australia, Canada, Saudi Arabia, US, Qatar (the highest per capita emitter).
3. The lowest levels of per capita emissions are in LICs, especially in LDCs.
4. The major challenge the world faces are future emission trends reflecting further population growth (e.g. in India and in Africa), as well as economic growth powered by fossil fuels.

Human Activities Are Driving the Enhanced Greenhouse Effect

1. Human activities like burning fossil fuels, deforestation, and industrial processes release excess carbon dioxide (CO₂), methane (CH₄), and chlorofluorocarbons (CFCs) into the atmosphere.
2. These gases trap more heat, amplifying the natural greenhouse effect.
3. This leads to rising global temperatures, causing:
   1. Extreme Weather Events: Increased droughts, floods, and storms.
   2. Sea Level Rise: Melting ice caps and thermal expansion of seawater.

Sources of Anthropogenic Greenhouse Gases

1. Obtaining Energy by Fossil Fuel Combustion

1. Fossil fuels - coal, oil, and natural gas - are the primary energy sources for transportation, electricity, and energy used in industry and buildings.
2. When burned, they release carbon dioxide (CO₂), the most significant anthropogenic greenhouse gas (GHG).

2. Agriculture, Forestry and Land Use

1. Agriculture

1. Methane (CH₄) is a potent GHG, primarily emitted through agricultural activities.

2. Deforestation and Land Use

1. Forests act as carbon sinks, absorbing CO₂ through photosynthesis.
2. When trees are cut down or burned to make space for agriculture or human settlements, this stored carbon is released back into the atmosphere and deforested areas become carbon sources.

3. Industrial Processes

1. Chlorofluorocarbons (CFCs) and other synthetic gases are used in refrigeration, air conditioning, and manufacturing.
2. These gases are thousands of times more effective at trapping heat than CO₂.