Global Environmental Issues: Greenhouse Effect, Ozone Depletion, and Water Pollution

Posted on Sep 4, 2024 in Geology

Actual Problems of Atmosphere and Global Climate

Greenhouse Effect, Ozone Depletion, Chemical Pollution of Seas: Causes, International Cooperation in Prevention, Impact on Human Health

The Greenhouse Effect

The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases and is re-radiated in all directions.

  • Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere.
  • As a result, the temperature there is higher than it would be if direct heating by solar radiation were the only warming mechanism.

What are Greenhouse Gases?

  • A greenhouse gas is a gas in the atmosphere that absorbs and emits infrared thermal radiation (e.g., water vapor, carbon dioxide, methane, nitrous oxide, ozone).
  • Greenhouse gases increase the temperature of the Earth’s surface (without them, it would be 33°C colder).
  • The sun is responsible for virtually all energy that reaches the Earth’s surface.
  • Direct overhead sunlight at the top of the atmosphere provides 1366 W/m2; however, geometric effects and reflective surfaces limit the light absorbed to an annual average of ~235 W/m2.
  • If this were the total heat received at the surface, then the Earth’s surface would be expected to have an average temperature of -18°C.
  • Instead, the Earth’s atmosphere recycles heat coming from the surface and delivers an additional 324 W/m2, which results in an average surface temperature of roughly +14°C.
  • Of the surface heat captured by the atmosphere, more than 75% can be attributed to the action of greenhouse gases that absorb thermal radiation emitted by the Earth’s surface.
  • The atmosphere, in turn, transfers the energy it receives both into space (38%) and back to the Earth’s surface (62%).
  • This process, by which energy is recycled in the atmosphere to warm the Earth’s surface, is known as the greenhouse effect and is an essential piece of Earth’s climate.

Under stable conditions, the total amount of energy entering the system from solar radiation will exactly balance the amount being radiated into space, thus allowing the Earth to maintain a constant average temperature over time.

The Problem of Global Warming

  • Strengthening of the greenhouse effect through human activities is known as the enhanced greenhouse effect.
  • This increase in radiative forcing from human activity is attributable mainly to increased atmospheric carbon dioxide levels.
  • CO2 is produced by fossil fuel burning and other activities such as cement production and tropical deforestation.

Global warming refers to the rising average temperature of Earth’s atmosphere and oceans and its related effects.

  • In the last 100 years, Earth’s average surface temperature increased by about 0.8°C.
  • An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, and a probable expansion of subtropical deserts.
  • Other likely effects of the warming include more frequent occurrences of extreme weather events, including heat waves, droughts and heavy rainfall events, species extinctions due to shifting temperature regimes, and changes in agricultural yields.

Effects of Global Warming

  • Although global warming may bring some localized benefits, such as fewer winter deaths in temperate climates and increased food production in certain areas, the overall health effects of a changing climate are likely to be overwhelmingly negative.
  • Climate change affects social and environmental determinants of health: clean air, safe drinking water, sufficient food, and secure shelter.
Extreme Heat
  • Extreme heat contributes directly to deaths from cardiovascular and respiratory disease, particularly among elderly people.
  • In the heat wave of summer 2003 in Europe, for example, more than 70,000 excess deaths were recorded.
  • High temperatures also raise the levels of ozone and other pollutants in the air that exacerbate cardiovascular and respiratory disease.
  • Pollen and other aeroallergen levels are also higher and may trigger asthma.
Natural Disasters
  • Globally, the number of reported weather-related natural disasters has more than tripled since the 1960s.
  • Every year, these disasters result in over 60,000 deaths, mainly in developing countries.
Changes to Rainfall
  • Increasingly variable rainfall patterns are likely to affect the supply of fresh water.
  • A lack of safe water can compromise hygiene and increase the risk of diarrheal disease, which kills almost 600,000 children under age 5 every year.
  • Floods are also increasing in frequency and intensity.
  • Floods contaminate freshwater supplies, heighten the risk of water-borne diseases, and create breeding grounds for disease-carrying insects such as mosquitoes.
  • They also cause drownings and physical injuries, damage homes, and disrupt the supply of medical and health services.
Patterns of Infection
  • Climatic conditions strongly affect water-borne diseases and diseases transmitted through insects, snails, or other cold-blooded animals.
  • Changes in climate can lengthen the transmission seasons and alter their geographic range.
  • For example, studies suggest that climate change could expose an additional 2 billion people to dengue transmission by the 2080s.

Prevention of Global Warming

Prevention is possible via policies and individual choices, such as:

  • Cleaner energy systems
  • Promoting the safe use of public transportation and active movement – such as cycling or walking

The WHO (2009) work plan on climate change and health includes:

  • Advocacy: to raise awareness that climate change is a fundamental threat to human health
  • Partnerships: to coordinate with partner agencies within the UN system and ensure that health is properly represented in the climate change agenda
  • Science and evidence: to coordinate reviews of the scientific evidence on the links between climate change and health, and develop a global research agenda
  • Health system strengthening: to assist countries to assess their health vulnerabilities and build capacity to reduce health vulnerability to climate change

Ozonosphere Injury (Ozone Depletion)

  • The ozone layer is a layer in Earth’s atmosphere that contains relatively high concentrations of ozone (O3).
  • This layer absorbs 97–99% of the Sun’s high-frequency ultraviolet light, which is potentially damaging to life forms on Earth.
  • Ozone depletion describes two distinct but related phenomena: a steady decline of about 4% per decade in the total volume of Earth’s stratosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone over Earth’s polar regions.
  • The most important process in both is the catalytic destruction of ozone by atomic halogens.
  • The main source of these halogen atoms in the stratosphere is the photodissociation of man-made halocarbon refrigerants (CFCs, freons, halons).
  • These compounds are transported into the stratosphere after being emitted at the surface.
  • In the presence of UV light, these gases dissociate and release chlorine atoms, which then catalyze ozone destruction.
  • CFCs and other contributory substances are referred to as ozone-depleting substances (ODS).
  • It is suspected that a variety of biological consequences, such as increases in skin cancer, cataracts, damage to plants, and a reduction of plankton populations in the ocean’s photic zone, may result from the increased UV exposure due to ozone depletion.
  • Consequence: Higher levels of UVB reaching the Earth’s surface → skin cancer, cataracts

Water Pollution

(See topic 3)