Greenhouse Effect and Gases

• Greenhouse gases in the atmosphere absorb infrared radiation from Earth's surface, emitting it back and causing warming, known as the greenhouse effect.
• Most greenhouse gases persist for many years, contributing to long-term warming.

Greenhouse Effect

• Thermal radiation from a planet's surface is absorbed by atmospheric greenhouse gases.
• These gases then re-radiate the energy in all directions, leading to a rise in temperature.
• Gases like water vapor, CO2, nitrous oxide, and methane trap energy from the sun.
• This process elevates the average surface temperature.

Greenhouse Gases

• Greenhouse gases have different atmospheric concentrations, residency times, and efficiencies in absorbing/emitting longwave radiation.
• Key greenhouse gases: water vapour, carbon dioxide, methane, nitrous oxide, and halocarbons.

Water Vapour

• Water vapour is the most abundant greenhouse gas and an effective absorber of radiation, contributing significantly to global warming.
• As air temperature increases, the atmosphere can hold more water vapour, leading to further warming.
• Additional water vapour in the atmosphere is not directly added by humans..
• The increase in water vapour amplifies climate change through a positive feedback loop.
• Water vapour unlike other greenhouse gases, will precipitate out of the atmosphere.
• Water vapour's atmospheric lifetime is short, lasting days, not decades or centuries.

Carbon Dioxide (CO2)

• Atmospheric carbon dioxide levels have risen from about 280 ppm in pre-industrial times to around 400 ppm today, an increase of over 40%.
• Over 80% of carbon dioxide emissions come from burning fossil fuels in industries, cutting and burning trees, and thermal power plants.
• Deforestation accounts for approximately 20% of the human-caused increase in carbon dioxide.

Carbon Dioxide from Automobile Exhaust

• Burning one gallon of gasoline releases 22 pounds of carbon dioxide.
• Carbon combines with oxygen when burned, creating carbon dioxide.
• The resulting carbon dioxide weighs more than the original fuel due to the added oxygen.
• There are over 600 million motor vehicles globally.
• If trends continue, vehicle numbers are likely to double in the next 30 years.

Methane (CH4)

• Methane is naturally produced by bacteria called methanogens in marshes, swamps, and wetland soils.
• Methane also escapes from garbage landfills, open dumps, and leaks during coal, oil, and natural gas extraction/transport.
• Research in 2006 showed permafrost melting in the Arctic is releasing trapped methane, as a result of global warming.

Methane from Animals

• Bacteria in cattle guts break down food, converting some of it to methane gas.
• A cow can emit up to half a pound of methane daily.
• Sheep, goats, buffalo, and camels also produce methane.
• World population growth increases the demand for meat and dairy products.
• The number of cattle has doubled in the last 40 years.

Nitrous Oxide

• Nitrous oxide is released naturally from oceans and soil bacteria.
• Each year, 7 to 13 million tons of nitrous oxide are added to the atmosphere.
• Human sources include: nitrogen-based fertilizers, disposal of human and animal wastes, and automobile exhausts.

Nitrous Oxide and Chemical Fertilizers

• Nitrogen-based fertilizer use has doubled in the past 15 years.
• Nitrogen fertilizers provide essential nutrients for crops.
• Nitrous oxide is released into the air when these fertilizers break down in the soil.

Halocarbons/Fluorocarbons

• Fluorocarbons are almost entirely the result of human activities.
• These chemicals are used in fire retardants and air conditioners.
• CFCs (chlorofluorocarbons), HCFCs (hydrochlorofluorocarbons), and HFCs (hydrofluorocarbons) are examples of halocarbons.
• Halocarbons trap significant amounts of radiation, so they have a very potent greenhouse potential.
• These compounds can remain in the environment for longer durations than other greenhouse gases.

History of Greenhouse Effect

• In 1896, Swedish scientist Svante Arrhenius (1859-1927) first claimed that fossil fuel combustion may result in enhanced global warming.
• A relation between atmospheric carbon dioxide concentrations and temperature was proposed.
• Water vapor and carbon dioxide created an average surface temperature of the earth of about 15°C.
• Naturally occurring greenhouse effect.
• It was not until 1987 it was actually verified.
• Increased levels of atmospheric carbon dioxide led to more infrared radiation absorption in the 1940s.
• Scientists began questioning greenhouse effect theory in the 1990s due to data uncertainties.
• Global warming discussion remains ongoing with continuous data checking and renewal.
• Models are updated to incorporate new discoveries and theories.
• Climate change is hard to tackle by individual countries, as it presents a global concern.
• The Kyoto Protocol was negotiated in Kyoto, Japan in 1998.
• This required participating countries to reduce greenhouse gas emissions by at least 5% below 1990 levels between 2008-2012.
• The Kyoto Protocol was signed in Bonn in 2001 by 186.

Recent role of greenhouse effect

• Since the Industrial Revolution began around 1750, human activities have dramatically contributed to climate change, from addition of other heat-trapping gases with CO2.
• These greenhouse gas emissions increased the greenhouse effect and caused Earth's surface temperature to rise.
• The main human activity causing climate change is greenhouse gas emission from burning fossil fuels.

Chlorofluorocarbons (CFCs)

• CFCs deplete the ozone layer.
• International efforts have led to banning CFC production and release.
• The Montreal Protocol effectively reduced CFCs in the environment.
• Dependence shifted to HCFCs and HFCs as a result of this ban.
• Although processes are in place to phase out these products they will continue to contribute to warming for centuries to come.

Impacts of Greenhouse Gas Emissions

• Continued warming from greenhouse gases is projected to impact the environment, human health, and the economy.
• Average annual temperatures are expected to increase overall.
• Resulting in decreasing snow, sea ice, and glacier will cause, rising sea levels and increased coastal flooding.
• Rising temperatures will thaw permafrost in the Arctic.
• Storm and heatwave severity are likely to be exacerbated.
• Many species may struggle to adjust to a warmer climate, and will be susceptible to diseases.

Global Problem

• Rising global temperatures affect every nation on Earth.
• This requires international approaches.
• Individual country is responsible for own greenhouse gas production.

Controlling Measures

• Reducing the consumption of fossil fuels.
• Afforestation to remove carbon dioxide from the atmosphere.
• Eco friendly alternative CFC.
• Carbon dioxide pumped to underground storage.
• Bioremediation.
• Sulphate aerosols.