Pollution and its impact on Biosphere | Zoology Optional Notes for UPSC PDF Download

Climate vs. Weather

• Climate refers to the long-term, predictable atmospheric conditions of a specific area and is characterized by consistent temperature and annual rainfall ranges.
• Weather, on the other hand, refers to the atmospheric conditions during a short period of time, typically within a 48-hour cycle.
• Climate is what you would consider when planning an outdoor event based on historical weather patterns, while weather is the specific atmospheric conditions on a given day.

• Global climate change is a term used to describe altered global weather patterns, including a worldwide increase in temperature, primarily due to rising levels of atmospheric carbon dioxide.
• It involves changes in the long-term, predictable climate conditions of the planet.

Evidence for Global Climate Change

• Scientists rely on historical evidence to indirectly measure temperature and other climatic variables.
• Antarctic ice cores are a crucial source of evidence, providing samples of polar ice that can reveal historical temperature and carbon dioxide data.
• By analyzing these ice cores, scientists have estimated Earth's temperature over the past 400,000 years.
• The data from the ice cores show periodic cycles of increasing and decreasing temperatures.
• These temperature cycles are linked to the historical atmospheric concentration of carbon dioxide, indicating a relationship between carbon dioxide levels and temperature.
• Carbon dioxide levels in the atmosphere have historically cycled between 180 and 300 parts per million (ppm) by volume.

Natural Drivers of Climate Change

1. Milankovitch Cycles: These cycles describe the effects of slight changes in Earth's orbit on its climate. They operate on timeframes ranging from 19,000 to 100,000 years.

2. Solar Intensity: Changes in solar intensity, the amount of solar energy emitted by the sun, can directly impact Earth's temperature. There is a direct relationship between solar intensity and temperature.

3. Volcanic Eruptions: Volcanic eruptions release gases and solids, including carbon dioxide, sulfur dioxide, and more. These events can cause short-term climate changes, typically cooling due to haze-effect.

• Greenhouse gases, including carbon dioxide, methane, water vapor, nitrous oxide, and ozone, play a crucial role in Earth's climate. They trap heat energy in the atmosphere, similar to the way glass panes in a greenhouse keep heat from escaping.

• The more greenhouse gases there are in the atmosphere, the more thermal energy is reflected back to Earth's surface, leading to the greenhouse effect and an increase in global temperatures.

• The link between rising atmospheric concentrations of carbon dioxide and global temperature increases. It mentions that the concentration of atmospheric carbon dioxide has increased significantly since 1950.

Human-Induced Climate Change

• Human activities, such as burning fossil fuels (gasoline, coal, natural gas), deforestation, cement manufacturing, animal agriculture, land clearing, and forest burning, release carbon dioxide into the atmosphere.

• Methane is another significant greenhouse gas produced by human activities, including bacterial breakdown of organic matter, decomposition in landfills, and methane release from melting clathrates (frozen ice and methane).

• The he presence of modern human society is the primary reason for the rapid increase in atmospheric carbon dioxide levels and emphasizes that no other natural driver of climate change has caused such a rapid and significant increase.

• The release of greenhouse gases is linked to the accelerated rate of global warming, creating a positive feedback loop.

Geological Evidence of Climate Change

1. Permian Extinction Event (251 Million Years Ago)
   • The Permian extinction occurred during the Permian period, one of Earth's warmest geological periods.
   • Approximately 70% of terrestrial and 84% of marine species went extinct.
   • Organisms adapted to wet and warm conditions struggled to survive.

Contemporary Climate Change Effects

2. Glacier Recession in Glacier National Park

   • Glacier National Park in Montana has witnessed a significant retreat of its glaciers over time.
   • In 1850, the park had around 150 glaciers, but by 2010, only about 24 glaciers > 25 acres remained.
   • For example, Grinnell Glacier at Mount Gould shrank by 40% between 1966 and 2005.

3. Melting Ice Sheets in Greenland and Antarctica

   • Both Greenland and Antarctic ice sheets are losing mass, contributing to sea-level rise.
   • Greenland lost 150-250 km³ of ice annually from 2002 to 2006.

4. Decreasing Arctic Sea Ice

   • The size and thickness of Arctic sea ice are diminishing.
   • These changes have led to rising global sea levels at an average rate of 1.8 mm per year.

5. Factors Influencing Ocean Volume

   • Ocean volume is influenced by factors like water temperature and the contribution of liquid water from melting glaciers, polar ice caps, and sea ice.

6. Impact on Organisms

   • Changes in temperature and precipitation affect the distribution and timing of plant and animal life events (phenology).
   • In Great Britain, 385 plant species now flower 4.5 days earlier than in the past 40 years.
   • Insect-pollinated species tend to flower earlier, potentially leading to ecosystem disruptions due to mismatches with their pollinators.

Climate Change History and Causes

7. Historical Climate Variability

   • The Earth has experienced temperature fluctuations over the past 2000 years, including the Medieval Climate Anomaly (warmer) and Little Ice Age (cooler) periods.

8. Natural Climate Drivers

   • Natural drivers of climate change include Milankovitch cycles, solar activity changes, and volcanic eruptions.

9. Human Influence on Climate

   • Burning fossil fuels is a significant source of greenhouse gases, contributing to the greenhouse effect.

10. Permian Extinction

    • The Permian extinction serves as historical evidence of the impact of global warming, resulting in a large-scale extinction event documented in the fossil record.

11. Contemporary Climate Change Effects on Plants and Animals

    • Modern climate change affects organisms when the timing of seasonal events (phenology) is disrupted by global warming, potentially causing ecosystem imbalances.