Climate Change

Climate change

Climate change refers to long-term shifts in temperatures and weather patterns. Such shifts can be natural, due to changes in the sun’s activity or large volcanic eruptions. But since the 1800s, human activities have been the main driver of climate change, primarily due to the burning of fossil fuels like coal, oil and gas.

Burning fossil fuels generates greenhouse gas emissions that act like a blanket wrapped around the Earth, trapping the sun’s heat and raising temperatures.

The main greenhouse gases that are causing climate change include carbon dioxide and methane. These come from using gasoline for driving a car or coal for heating a building, for example. Clearing land and cutting down forests can also release carbon dioxide. Agriculture, oil and gas operations are major sources of methane emissions. Energy, industry, transport, buildings, agriculture and land use are among the main sectors causing greenhouse gases.

Past, Present, and Future Climate Change

• Past: Earth’s climate has undergone significant changes over geological time—glacial (ice ages) and interglacial periods occurred cyclically.
  • Example: The Last Glacial Maximum (LGM) occurred about 20,000 years ago.
• Present: The current phase of climate change is rapid and anthropogenically driven, primarily due to:
  • Greenhouse gas emissions
  • Deforestation
  • Urbanization
  • Industrial activity
• Future: According to IPCC reports:
  • Global average temperatures could rise by 1.5°C to 4.5°C by 2100.
  • Sea levels could rise by up to 1 meter, impacting coastal ecosystems and populations.
  • Extreme weather events (heatwaves, floods, droughts) are expected to intensify.

Historical Examples of Climate Change

• Ice Age (Pleistocene Epoch) – Cyclical glaciations driven by Milankovitch cycles.
• Medieval Warm Period (950–1250 AD) – Unexplained warming of the Northern Hemisphere.
• Little Ice Age (1300–1850 AD) – A cooler period marked by glacial expansion in Europe.
• 20th Century Warming – Average global temperature increased by about 1°C since pre-industrial times.

Factors Affecting Climate Change

Climate change is influenced by both natural and anthropogenic factors. These factors affect Earth’s energy balance—the equilibrium between incoming solar radiation and outgoing terrestrial radiation.

Earth’s Energy Balance

• The Earth’s climate is driven by the sun’s radiation, which reaches Earth and is either absorbed, reflected, or re-radiated.
• Albedo Effect: The reflectivity of Earth’s surface—ice and snow have high albedo; forests and oceans have low albedo.
• Greenhouse Effect: Greenhouse gases (CO₂, CH₄, N₂O, water vapor) trap heat, warming the atmosphere.
• Any imbalance due to increased greenhouse gases leads to global warming.

Natural Factors Influencing Climate Change

a. Continental Drift

• The slow movement of continents (plate tectonics) affects ocean circulation and atmospheric patterns.
• Example: The separation of South America and Africa altered the Atlantic Ocean circulation.

b. Variation in Earth’s Orbit (Milankovitch Cycles)

• Includes:
  • Eccentricity – Change in Earth’s orbit shape (~100,000-year cycle).
  • Axial Tilt (Obliquity) – Changes in the angle of Earth’s axis (~41,000-year cycle).
  • Precession – Wobble in Earth’s rotational axis (~26,000-year cycle).
• These affect solar insolation distribution and cause glacial-interglacial cycles.

c. Plate Tectonics

• Volcanic activity along plate boundaries emits gases (CO₂, SO₂) that influence atmospheric composition.
• Mountain building affects wind and monsoon patterns.

d. Volcanic Activity

• Volcanic eruptions release large volumes of ash and gases.
  • SO₂ leads to aerosol formation → increases albedo → cooling effect.
  • Example: Mount Pinatubo eruption (1991) caused global cooling of ~0.5°C for 2 years.

e. Ocean Currents

• Currents distribute heat globally; disruption can change climate patterns.
  • El Niño-Southern Oscillation (ENSO) affects global temperature and rainfall.
  • Thermohaline circulation changes can disrupt climate stability, especially in Europe.

Understanding the anthropogenic factors contributing to climate change is crucial for developing effective mitigation strategies. Below is an in-depth exploration of these factors, the role of greenhouse gases, and their specific impacts on the Earth’s climate system.

Anthropogenic (Human-Caused) Factors Contributing to Climate Change

1.Greenhouse Gas Emissions

Human activities have significantly increased the concentration of greenhouse gases (GHGs) in the atmosphere, enhancing the natural greenhouse effect and leading to global warming. The primary sources of these emissions include:

• • • Burning of Fossil Fuels: Combustion of coal, oil, and natural gas for electricity, heat, and transportation is the largest single source of global GHG emissions. This process releases substantial amounts of carbon dioxide (CO₂) into the atmosphere. ​
    • Industrial Processes: Industries produce GHGs during manufacturing processes. For example, cement production releases CO₂ both from the chemical conversion process and the energy consumed. ​
    • Agricultural Practices: Agriculture contributes to GHG emissions through enteric fermentation in livestock (producing methane), rice cultivation (methane emissions), and the use of nitrogen-based fertilizers (leading to nitrous oxide emissions). ​2.Atmospheric Aerosols

Aerosols are tiny particles suspended in the atmosphere that can influence the climate by scattering and absorbing sunlight and by affecting cloud formation. Human activities, such as burning fossil fuels and biomass, release large quantities of aerosols. While some aerosols have a cooling effect by reflecting sunlight back into space, others, like black carbon, absorb heat and contribute to warming. Moreover, aerosols can alter precipitation patterns and cloud properties, further impacting the climate system.

3.Land Use Changes

Alterations in land use, particularly deforestation and urbanization, affect the Earth’s albedo (surface reflectivity) and carbon storage capacity:

• • Deforestation: Trees act as carbon sinks, absorbing CO₂ from the atmosphere. Removing forests for agriculture or urban development reduces this capacity and releases stored carbon, increasing atmospheric CO₂ levels.
  • Urbanization: The expansion of urban areas often replaces natural landscapes with impervious surfaces like asphalt, which can alter local climates (urban heat island effect) and reduce natural carbon sequestration.​

Greenhouse Gases and Their Impact

Greenhouse gases trap heat in the Earth’s atmosphere, leading to the greenhouse effect, which warms the planet. The major GHGs include:​

1.Water Vapor (H₂O)

Water vapor is the most abundant greenhouse gas and plays a crucial role in the natural greenhouse effect. Its concentration in the atmosphere is primarily controlled by temperature; as the atmosphere warms due to other GHGs, it can hold more water vapor, which in turn amplifies the warming in a feedback loop.

2.Carbon Dioxide (CO₂)

CO₂ is a significant anthropogenic greenhouse gas, with concentrations rising due to activities like fossil fuel combustion and deforestation. It has a long atmospheric lifetime, meaning its effects persist over centuries. The increase in CO₂ levels is a primary driver of recent climate change.

3.Methane (CH₄)

Methane is over 25 times more effective than CO₂ at trapping heat over a 100-year period. Major sources include livestock digestion, rice cultivation, landfills, and fossil fuel extraction. Although it has a shorter atmospheric lifetime than CO₂, its potent warming effect makes it a critical target for emission reductions.

4.Nitrous Oxide (N₂O)

N₂O is approximately 300 times more effective than CO₂ at trapping heat over a 100-year period. It is primarily emitted from agricultural activities, especially the use of synthetic fertilizers, as well as from industrial processes and combustion of organic matter.

5.Chlorofluorocarbons (CFCs)

CFCs are synthetic compounds once commonly used as refrigerants and propellants. They are potent greenhouse gases and also contribute to ozone layer depletion. International agreements like the Montreal Protocol have successfully reduced their production and use.