Atmosphere and climate change (IB)

The Earth's Atmosphere

The Earth's atmosphere is the layer of gases surrounding the Earth, essential for life on the planet. It provides oxygen, protects from harmful ultraviolet radiation, and helps regulate temperature through the greenhouse effect.

Layers of the Atmosphere:

1. Troposphere:

   • This is where all weather phenomena occur (e.g., clouds, storms, and rainfall).

   • Temperature decreases with altitude in this layer.

   • Contains around 75% of the atmosphere’s mass.

2. Stratosphere:

   • Contains the ozone layer, which absorbs harmful UV radiation from the Sun and protects life on Earth.

   • Temperature increases with altitude because the ozone layer absorbs solar radiation.

3. Mesosphere:

   • This layer extends to about 85 km above the Earth.

   • It’s where meteors burn up when they enter the atmosphere.

   • Temperature decreases with altitude in this layer.

4. Thermosphere:

   • Extends from 85 km to about 600 km.

   • The air is very thin, and temperatures increase significantly with altitude.

   • Solar activity (sunspots, solar flares) has a big influence here.

   • This is where the Northern and Southern Lights (Aurora Borealis/Australis) occur due to interactions between solar winds and the Earth's magnetic field.

5. Exosphere:

   • Above 600 km, the atmosphere becomes extremely thin and merges into outer space.

   • This layer contains hydrogen and helium atoms that can escape into space.

Composition of the Atmosphere:

• Nitrogen (78%): It is inert and does not react with other elements under normal conditions, acting as a filler.

• Oxygen (21%): Essential for respiration in animals and plants.

• Argon (0.9%): A noble gas with no significant impact on the atmosphere.

• Carbon Dioxide (0.03%): Vital for photosynthesis in plants but is a major contributor to the greenhouse effect.

• Water Vapor: Its concentration varies between 0-4%, depending on location and weather conditions.

The Greenhouse Effect

The greenhouse effect refers to the trapping of heat in the Earth's atmosphere due to the presence of certain gases. These gases allow sunlight to pass through but prevent some of the heat from escaping into space, warming the planet.

• Incoming Solar Radiation: The Sun emits energy in the form of light (visible radiation) and heat (infrared radiation). This energy passes through the atmosphere and warms the Earth's surface.

• Outgoing Infrared Radiation: The Earth then emits this absorbed energy as infrared radiation, which is absorbed and re-emitted by greenhouse gases like CO2, methane, and water vapor, trapping heat in the atmosphere.

• Enhanced Greenhouse Effect: Human activities, such as burning fossil fuels, deforestation, and industrial activities, have increased the concentration of greenhouse gases, leading to more heat being trapped and global warming.

Climate vs. Weather

• Weather: Refers to short-term atmospheric conditions in a particular location (e.g., daily temperature, humidity, rainfall).

• Climate: Refers to the long-term average of weather conditions over a prolonged period (typically 30 years). The climate can be influenced by factors such as latitude, altitude, ocean currents, and wind patterns.

Key Differences:

• Weather is variable and changes frequently, while climate is stable and predictable over long periods.

• Weather can be experienced on a daily or weekly basis, while climate is more about patterns and averages over decades.

Human Activities Contributing to Climate Change

The rapid increase in greenhouse gases due to human activities is the primary cause of contemporary climate change. Key contributors include:

• Burning of Fossil Fuels:

  • Coal, oil, and natural gas are burned for energy in electricity generation, industry, and transportation, releasing CO2 and other GHGs.

• Deforestation:

  • Trees absorb CO2 for photosynthesis. When forests are cleared for agriculture or urbanization, carbon is released, exacerbating global warming.

• Agriculture:

  • Livestock farming produces methane (a potent GHG), especially from ruminant animals (cattle, sheep).

  • Rice paddies also release methane.

  • Synthetic fertilizers used in agriculture release nitrous oxide (N2O), a greenhouse gas more powerful than CO2.

• Industrial Processes:

  • The production of cement, chemicals, and metals often releases significant amounts of CO2, as well as other industrial gases, such as hydrofluorocarbons (HFCs).

• Waste Management:

  • Landfills emit methane as organic waste decomposes anaerobically (without oxygen).

Impacts of Climate Change

Climate change brings about various physical and environmental changes. Some of these are:

• Rising Global Temperatures:

  • The Earth's average temperature has risen by approximately 1°C since the late 19th century, with significant consequences for ecosystems and human health.

• Melting Ice and Snow:

  • The polar ice caps and glaciers are melting rapidly, contributing to rising sea levels.

• Sea-Level Rise:

  • Rising temperatures cause seawater to expand and ice to melt, raising global sea levels. This threatens coastal regions with flooding, erosion, and loss of land.

• Extreme Weather Events:

  • Increased temperatures can lead to more frequent and severe weather events such as hurricanes, heatwaves, droughts, and floods.

• Ocean Acidification:

  • The ocean absorbs about a quarter of the CO2 emissions, leading to acidification. This harms marine ecosystems, particularly coral reefs and shellfish.

• Loss of Biodiversity:

  • Climate change alters habitats, forcing species to migrate or adapt. Some species, particularly those in sensitive ecosystems (e.g., polar regions), face extinction.

Global Climate Models (GCMs)

Global Climate Models (GCMs) simulate the Earth's climate system and predict future climate conditions based on various scenarios of greenhouse gas emissions.

• Components of GCMs: These models consider factors like solar radiation, GHG concentrations, aerosols, cloud formation, ocean circulation, and land use changes.

• Emission Scenarios: The Intergovernmental Panel on Climate Change (IPCC) uses scenarios called Representative Concentration Pathways (RCPs) to model potential future emissions, ranging from high emissions (RCP8.5) to low emissions (RCP2.6).

• Projections: GCMs predict changes in temperature, precipitation patterns, and sea level rise over different time frames (e.g., 2050, 2100).

Mitigation and Adaptation Strategies

Mitigation focuses on reducing or preventing greenhouse gas emissions, while adaptation involves adjusting to the changes that are already occurring.

Mitigation Strategies:

• Renewable Energy: Transition to energy sources such as solar, wind, hydropower, and geothermal to replace fossil fuels.

• Energy Efficiency: Improve the efficiency of buildings, vehicles, and industrial processes to reduce energy consumption.

• Carbon Capture and Storage (CCS): Capture CO2 emissions from power plants and industrial sites, and store them underground to prevent them from entering the atmosphere.

• Carbon Trading: A market-based approach where countries or companies can trade carbon credits to meet emissions reduction targets.

• Sustainable Land Use: Implement agroforestry, regenerative agriculture, and sustainable forestry practices to reduce emissions and increase carbon storage.

Adaptation Strategies:

• Infrastructure Improvements: Build flood defenses, resilient infrastructure, and seawalls to protect coastal areas from rising sea levels.

• Water Management: Improve water usage efficiency in drought-prone regions and promote water conservation.

• Climate-Resilient Crops: Develop drought- and flood-resistant crop varieties to maintain food security under changing climatic conditions.

• Public Health Adaptation: Enhance healthcare systems to respond to the increased risk of heat-related illnesses, vector-borne diseases (e.g., malaria), and other climate-sensitive health issues.

International Agreements

The global response to climate change involves numerous international agreements and collaborations aimed at reducing emissions and mitigating climate change:

• The Kyoto Protocol (1997): The first legally binding international agreement to reduce GHG emissions, though it mainly required developed countries to take action.

• The Paris Agreement (2015): A landmark agreement aiming to limit global warming to well below 2°C above pre-industrial levels. Countries submit Nationally Determined Contributions (NDCs) to reduce emissions, with regular reviews and updates.

• COP Conferences: The Conference of the Parties (COP) is held annually under the United Nations Framework Convention on Climate Change (UNFCCC), where governments discuss and negotiate actions to address climate change.

Key Terms and Concepts

• Carbon Footprint: The total amount of greenhouse gases emitted into the atmosphere due to human activities, usually expressed in tons of CO2-equivalent.

• Carbon Sequestration: The process of capturing and storing carbon from the atmosphere, either through natural methods (forests, soil) or technological means (carbon capture and storage).

• Feedback Loops: These are processes that either amplify or dampen the effects of climate change. For example, the melting of polar ice reduces the Earth's reflectivity (albedo), causing more solar radiation to be absorbed, thus accelerating warming.

Climate change represents one of the most significant global challenges in history. Understanding the science behind the atmosphere, greenhouse gases, and climate models is essential for making informed decisions about how to mitigate and adapt to climate change. Governments, industries, and individuals all have roles to play in reducing emissions and preparing for the inevitable changes caused by a warming world. Education and awareness are key to fostering a more sustainable and climate-resilient future.