Climate refers to the long-term average of weather events in a specific region. Unlike weather, which changes frequently, climate changes over extended periods due to various factors. Historically, Earth’s climate has undergone transformations due to natural causes like sunspots and ice age glaciations. Today, however, “climate change” is primarily associated with alterations in global climate patterns over the last century, primarily caused by human activities. These shifts are evident through temperature changes, rainfall patterns, and wind systems over decades.
Learning Outcomes:
Understand climate change and its primary causes.
Identify the impacts of global warming on the environment.
Recognize the greenhouse effect and its relation to global warming.
Comprehend the role of greenhouse gases and their sources.
Understand climate forcings and their impact on the Earth’s climate.
Global Warming
Global warming is characterized by an average increase in the Earth’s temperature, particularly in the atmosphere and troposphere, resulting in changes to global climate patterns. This warming has accelerated over the past century, especially in the last two decades. Human-induced activities, such as the burning of fossil fuels and deforestation, are significant contributors.
Global Warming – Impacts
Sea Level Rise: Melting ice caps and glaciers contribute to the increase in sea levels, leading to coastal erosion and flooding.
Changes in Rainfall Patterns: Altered precipitation trends affect water supplies, agriculture, and ecosystems.
Extreme Weather Events: Increased instances of heatwaves, flooding, hurricanes, and wildfires are attributed to global warming.
Habitat Loss: Melting glaciers and ice caps contribute to widespread animal population decline.
Disease Spread: Warmer climates facilitate the spread of diseases such as malaria to new regions.
Coral Bleaching: Increased sea temperatures cause coral reefs to bleach and die.
Loss of Plankton: Warmer seas affect plankton populations, disrupting marine food chains.
Important Note: Melanin production increases in response to high temperatures, humidity, and reduced light, influencing the pigmentation of species, like the Black Panther.
The Greenhouse Effect
The greenhouse effect is a naturally occurring phenomenon essential for maintaining the Earth’s temperature, making it habitable. Greenhouse gases in the atmosphere trap the Sun’s energy, preventing heat from escaping and warming the planet. Without this natural process, Earth would be a frozen, lifeless planet.
Greenhouse Gases: Constituents of the atmosphere, both natural and man-made, which absorb and re-emit infrared radiation.
What is the Greenhouse Effect?
Incoming Energy: The Sun emits energy in short wavelengths that penetrate the atmosphere and warm the Earth’s surface.
Absorption: Approximately 30% of this energy is reflected back into space by clouds, the atmosphere, and the Earth’s surface. The remaining 70% is absorbed by the Earth’s system.
Emission: Earth re-emits this energy as infrared radiation. Greenhouse gases absorb a significant portion of this long-wave energy, thus trapping heat.
Role of Greenhouse Gases: Gases like carbon dioxide (CO₂), methane (CH₄), and water vapor absorb the outgoing infrared radiation, re-emitting it in all directions and thereby warming the atmosphere and the Earth’s surface.
Human Contribution: Activities such as fossil fuel combustion and deforestation increase greenhouse gas concentrations, amplifying the natural greenhouse effect.
Important Note: The absence of naturally occurring greenhouse gases would result in Earth’s average surface temperature being -19°C, rather than the current 15°C.
Greenhouse Gases
Water Vapor
Contribution: Water vapor is the largest contributor to the natural greenhouse effect, though not directly impacted by human activities.
Evaporation: The presence of other greenhouse gases like CO₂ increases temperatures, thereby boosting evaporation rates and subsequently raising water vapor levels in the atmosphere.
Cycle: Unlike CO₂, water vapor cycles quickly through the atmosphere, falling back to Earth as rain or snow.
Carbon Dioxide (CO₂)
Primary Source: Fossil fuel combustion, deforestation, and certain industrial processes are the primary sources of human-generated CO₂.
Carbon Cycle: CO₂ naturally exists in the atmosphere as part of the carbon cycle involving the exchange of carbon among the atmosphere, oceans, soil, and living organisms.
Emissions and Trends: Between 1990 and 2010, CO₂ emissions increased significantly due to population and economic growth.
Mitigation: Reducing fossil fuel consumption, increasing energy efficiency, and utilizing carbon capture and sequestration are critical strategies for reducing CO₂ emissions.
Important Note: The USA is the second-largest emitter of greenhouse gases. Cumulatively, it has the highest historical emissions.
Methane (CH₄)
Sources: CH₄ emissions arise from natural sources like wetlands and human activities such as livestock farming, leakage from natural gas systems, and landfill waste decomposition.
Agriculture: Livestock, through their digestive processes, produce significant methane emissions. The agriculture sector is the primary source of CH₄ emissions globally.
Industry: Natural gas production, processing, and distribution release CH₄ into the atmosphere.
Nitrous Oxide (N₂O)
Sources: Emitted through natural processes and human activities, such as agriculture, fossil fuel combustion, and wastewater management.
Agriculture: The use of synthetic fertilizers and the decomposition of livestock manure contribute to N₂O emissions.
Removal: N₂O is removed from the atmosphere via bacterial absorption or through destruction by ultraviolet radiation.
Fluorinated Gases
Industrial Emissions: Emitted during industrial processes like aluminum and semiconductor manufacturing.
Categories: Main types include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆).
High GWPs: These gases have high global warming potentials and remain in the atmosphere for extended periods.
Black Carbon
Characteristics: A solid particle produced from incomplete combustion of fossil fuels, biomass burning, and diesel exhaust.
Impact: Absorbs heat directly in the atmosphere and reduces albedo (reflectivity) when deposited on ice and snow, accelerating melting.
Brown Carbon
Composition: Light-absorbing organic matter found in atmospheric aerosols.
Sources: Primarily from biomass burning and domestic wood burning.
Important Note: Black carbon from India and China accounts for 25-35% of global emissions due to cooking methods and heating with wood and cow dung.
Climate Forcings
Climate forcings are factors influencing the climate system, leading to warming (positive forcings) or cooling (negative forcings). Forcings affect the Earth’s energy balance, with radiative forcing measuring the change caused by these factors.
Natural Forcings
Solar Variations: Changes in the amount of energy emitted by the Sun affect the Earth’s climate.
Volcanic Eruptions: Volcanic ash and gases, such as sulfate aerosols, cool the atmosphere by reflecting sunlight.
Human-Induced Forcings
Greenhouse Gas Emissions: The increase in CO₂ from fossil fuel combustion is the most significant human-induced climate forcing, accounting for more than half of total positive forcing since 1750.
Aerosols: Human-generated aerosols from burning fossil fuels reflect sunlight, providing a cooling effect.
Concept: Global Warming Potential (GWP) measures the energy a gas absorbs over a set time, compared to CO₂.
Estimating Greenhouse Gas Effects
Concentration: Measured in parts per million (ppm), billion (ppb), or trillion (ppt).
Atmospheric Lifetime: Determines how long the gas remains in the atmosphere, affecting its overall impact.
Global Warming Potential (GWP): Reflects how strongly the gas affects global temperatures.
GWP & Lifetime of Greenhouse Gases
GAS
GWP (100-year)
LIFETIME (years)
Carbon dioxide (CO₂)
1
100
Methane (CH₄)
21
12
Nitrous oxide (N₂O)
310
120
Hydrofluorocarbons (HFCs)
140-11,700
1-270
Perfluorocarbons (PFCs)
6,500-9,200
| 800-50,000 |
| Sulfur hexafluoride (SF₆)| 23,900 | 3,200 |
Note: Methane (CH₄), though short-lived, has a GWP 21 times that of CO₂ over a 100-year time frame.
Receding Glaciers – A Symptom of Global Climate Change
Glacial retreat serves as a clear indicator of global climate change. The Himalayan glaciers, Andes glaciers, and glaciers in Glacier National Park are all receding rapidly, threatening regional ecosystems and water supplies. As glaciers vanish, they signal broader climate variations affecting both human and natural systems.
Impact of Glacial Retreat
Water Supply: Glacial meltwater is crucial for water supplies in dry countries such as Mongolia and Pakistan.
Ecosystem Changes: The disappearance of glaciers alters regional ecosystems, affecting biodiversity and local climates.
Flooding: Melting glaciers contribute to rising sea levels, resulting in flooding and coastal submersion.
Important Note: Shola forests in the Western Ghats serve as natural water conservation systems, highlighting the interconnection between ecosystems and climate.
Chain of Events
Fossil Fuel Combustion ➜ Increase in Greenhouse Gases ➜ Global Warming ➜ Climatic Changes.
Glacial Melting ➜ Flooding ➜ Submergence of Coastal Lands ➜ Destruction of Ecosystems.
Important Note: Project Surya in India aims to reduce black carbon emissions through solar cooking technologies, biogas plants, and efficient stoves.
MCQ: What is the primary human-induced source of methane emissions?