Notes Class 11 Chapter 5 Geography Maharashtra Board

Global Climate Change

Introduction

• Definition: Global climate change refers to long-term shifts in weather patterns, temperature, precipitation, and other climatic elements, primarily driven by human activities, though natural factors also play a role.
• Significance: The Earth’s average surface temperature has risen by approximately 0.8°C over the last century, leading to significant environmental and societal impacts.
• Scope: This chapter explores the causes, indicators, effects, tools for studying climate change, and measures to combat it, with a focus on global and Indian contexts.

1. Measuring Global Temperature Changes

Global Temperature Trends:

• From 1985 to 2015, global monthly temperatures were compared to the 20th-century average (Fig. 5.1).

• Key Observations:
  • 1985: Least difference in temperature (close to 0°C).
  • 2015: Highest difference, approximately 1.21°C above the 20th-century mean.
  • Temperature differences vary by month due to seasonal variations, regional climate patterns, and atmospheric circulation (e.g., monsoons, jet streams).
• Scientific Method:
  • Scientists combine air temperature data from land (weather stations) and ocean surfaces (ships, buoys, satellites).
  • Anomalies: Differences between daily temperatures and a 30-year average (“normal”) for a location. Positive anomalies indicate warmer conditions; negative indicate cooler.
  • Monthly and seasonal anomalies are averaged to track long-term trends.
• Earth’s Surface Temperature:
  • Average global temperature: ~14°C, suitable for life compared to other planets (e.g., Venus: 460°C, Mars: -60°C).
  • A 0.8°C rise, though small, has profound impacts due to its global scale and rapid rate.

2. Causes of Climate Change

A. Natural Causes

1. Solar Output Variations:
   • Changes in the Sun’s energy output affect Earth’s insolation. Low output can cool the planet.
2. Milankovitch Oscillations:
   • Variations in Earth’s orbit, axial tilt, and precession alter insolation, influencing climate (e.g., triggering ice ages when Earth is farther from the Sun).
3. Volcanism:
   • Eruptions release aerosols (e.g., sulfur dioxide) that reflect sunlight, temporarily cooling Earth. Examples: El Chichón (1982), Pinatubo (1991).
4. Goldilocks Zone:
   • Earth’s position in the habitable zone shifts as the Sun’s size changes, affecting long-term climate (cooler in early history, warming over time).

B. Anthropogenic Causes

Primary Driver: Human activities since the mid-20th century, especially post-industrialization.

Key Contributors:

1. Fossil Fuel Combustion: Releases CO2, the primary greenhouse gas (GHG), from industries, vehicles, and power plants.
2. Deforestation: Reduces CO2 absorption by trees and releases stored carbon when forests are burned.
3. Industrialization: Increases emissions of CO2, methane (CH4), and nitrous oxide (N2O) through manufacturing and agriculture.

CO2 Levels:

• Pre-industrial: ~280 ppm; 2017: >400 ppm (Fig. 5.4).
• WHO: >350 ppm is harmful to the environment.
• Atmospheric CO2 takes 20-25 years to stabilize, amplifying human impact.

3. Greenhouse Gases and Their Role

Definition: Gases that trap heat in the atmosphere, increasing Earth’s temperature (greenhouse effect).

Major Greenhouse Gases (Fig. 5.1, Global Greenhouse Gas Emissions):

1. Water Vapour: Highest contribution (~95%), natural but amplified by warming.
2. Carbon Dioxide (CO2): ~3.6%, from fossil fuels, deforestation (human and natural sources).
3. Methane (CH4): ~0.95%, from agriculture, livestock, landfills (human and natural).
4. Nitrous Oxide (N2O): ~0.36%, from fertilizers, industrial processes (mostly human).
5. Miscellaneous Gases: ~0.072%, e.g., CFCs (human-made, ozone-depleting).

Human Control:

• CO2, CH4, N2O, and CFCs can be controlled through reduced emissions, afforestation, and regulations.
• Water vapour is largely natural and harder to control directly.

Impact: Increased heat-holding capacity of the atmosphere drives global warming.

4. Effects of Global Warming

A. Direct Effects

1. Heat Waves:
   • Increased atmospheric heat capacity intensifies summer temperatures, leading to deadly heat waves (e.g., Chicago 1995, Paris 2003).
2. Heat Islands:
   • Urban areas with paved surfaces and concrete absorb and retain heat, amplifying temperatures compared to rural areas.
3. Sea Level Rise (Fig. 5.2):
   • Global sea level has risen ~50 mm since the 1990s, at ~3 mm/year.
   • Causes: Melting glaciers, ice sheets, and thermal expansion of seawater.
   • Impacts: Flooding of coastal areas, submersion of islands (e.g., Maldives), loss of habitats for fish, birds, and plants.
   • India: Projected rise of 9-90 cm by 2100, threatening Kutch, Mumbai, Konkan, Kerala, and eastern deltas (Ganga, Krishna, Godavari, Kaveri, Mahanadi).

1. Glacial Retreat (Fig. 5.3 A & B):
   • Glaciers like Gangotri (Himalayas) have retreated >850 m in 25 years (~22 m/year).
   • Other examples: Mt. Kilimanjaro, Alps, polar regions.
   • Cause: Faster melting than ice formation due to rising temperatures.

B. Indirect Effects

1. Jellyfish Proliferation:
   • Warmer, more acidic oceans favor jellyfish reproduction, altering marine ecosystems.
2. Spread of Insects:
   • Warmer temperatures and wetter conditions increase mosquito populations, spreading diseases like dengue in new regions.
3. Coral Bleaching:
   • Temperature rises of 1°-2°C cause corals to expel algae, leading to bleaching and death.
   • Over 20% of coral reefs lost globally, impacting marine biodiversity.
4. Changes in Seasons:
   • Altered monsoon arrivals, rainfall patterns, and flowering seasons, as observed by elders.
5. Increased Extreme Weather:
   • More frequent and intense floods (e.g., Mumbai 2005, Kedarnath 2013), cyclones (e.g., Chennai 2015), and droughts (doubled land area since 1970s).

5. Indicators of Climate Change

• Retreat of Glaciers: Visible in Gangotri, Alps, and polar regions.
• Increased Floods: Flash floods in urban areas and coastal flooding (e.g., Venice).
• Increased Cyclones: Higher frequency and intensity in tropical regions.
• Temperature Extremes: Rising minimum and maximum temperatures globally.
• Sea Level Rise: Measurable through tidal and satellite data.
• Ecosystem Changes: Shifts in species distribution (e.g., mosquitoes, jellyfish) and coral bleaching.

6. Tools for Studying Paleoclimatology

Paleoclimatology: Study of past climates using proxy data, as direct measurements are available only for the last 140 years.

Key Tools:

1. Ice Cores (Fig. 5.7, 5.8):

• • Samples from Greenland, Antarctica, and mountain glaciers show annual snow layers.
  • Summer and winter snow differ, revealing past climate conditions.

2. Tree Rings (Fig. 5.6):

• • Variations in ring width reflect environmental conditions (e.g., wet vs. dry years).

3. Coral Reefs (Fig. 5.5):

• • Seasonal growth rings (calcium carbonate density) indicate past ocean temperatures.

4. Ocean Sediments:

• • Deposits preserve climate signals, e.g., temperature and precipitation patterns.

Historical Evidence:

• • Geological records (glacial lake sediments), fossil records (e.g., mammoths), and tree rings indicate past glacial and interglacial periods.

7. Historical Context of Climate Change

• Not a New Phenomenon:
  • Earth has experienced multiple climate shifts, including ice ages and interglacial periods.
  • Example: Rajasthan was wet and cool 8,000 years ago; last glacial period ended ~10,000 years ago.
• Ice Ages:
  • Periods of significant polar ice expansion due to global cooling.
  • Current era: Interglacial period within an ice age, characterized by warmer conditions.
• Evidence:
  • Geological records (sediments, fossils), tree rings, and coral reefs show natural climate variability.
  • Warm periods (e.g., 500-300 million years ago) and cool periods (e.g., early Earth in outer Goldilocks Zone).
• Why Current Warming is Concerning:
  • Rate: Current warming is ~10 times faster than post-glacial warming.
  • Cause: Largely anthropogenic (post-1950s), driven by GHG emissions.
  • Scale: Global impacts observed via satellites, ice cores, and other advanced technologies.

8. Measures to Combat Climate Change

A. Global Efforts

• Research and Monitoring:
  • 1950s: Precise CO2 measurements confirmed rising levels.
  • 1980s: Established link between rising temperatures and GHGs.
• Intergovernmental Panel on Climate Change (IPCC):
  • Publishes reports (5 annual, latest: 2018 SR1.5 on 1.5°C warming).
  • Sets targets to limit warming to 1.5°C, requiring zero emissions by 2030-2050.
• International Agreements:
  • UNFCCC (1992): Framework for global climate action.
  • Kyoto Protocol: Commits countries to reduce GHG emissions.
  • Montreal Protocol (1987): Phases out ozone-depleting substances.
  • Paris Agreement (2016): Aims to limit warming to 1.5°C-2°C.
• Nobel Peace Prize (2007): Awarded to IPCC for climate change efforts.

B. India’s Initiatives

• Vulnerabilities:
  • Peculiar economy (agriculture-dependent) and geography (coastal areas, Himalayas).
  • High risk to sea level rise, floods, and droughts.
• Key Measures:
  1. National Action Plan on Climate Change (NAPCC, 2008):
     • 8 sub-missions to address mitigation, adaptation, and clean energy.
  2. National Adaptation Fund for Climate Change (NAFCC):
     • Supports states/UTs vulnerable to climate impacts; managed by NABARD.
  3. National Clean Energy Fund (NCEF):
     • Funds R&D in clean energy using carbon tax on coal; provides up to 40% project cost as loans/grants.
  4. Clean Energy Promotion: Solar, wind, and other renewables to reduce fossil fuel dependence.
  5. Environmental Protection: Afforestation, pollution control, and sustainable development.

C. Lifestyle Changes

• Individual Actions:
  • Use energy-efficient devices, reduce plastic use, and conserve water.
  • Walk or cycle for short distances, compost organic waste, and support recycling.
  • Reduce dependence on wood and non-renewable resources.
• Community Efforts:
  • Educate others, participate in tree-planting drives, and advocate for local policies.

9. Climate Change and India

• Challenges:
  • Developing nation with high emissions from industrialization and urbanization.
  • Balancing development needs with environmental sustainability.
  • Vulnerable regions: Coastal areas (Mumbai, Kerala), Himalayan glaciers, eastern deltas.
• Opportunities:
  • Leadership in global climate action (e.g., Paris Agreement commitments).
  • Investment in renewables and sustainable agriculture to enhance resilience.

10. Key Graphs and Questions

A. Fig. 5.1: Global Temperature Anomalies (1985-2015)

• Shows: Difference between global monthly temperatures and 20th-century average.
• Key Points:
  • 2015: Highest anomaly (1.21°C).
  • 1985: Least difference (~0°C).
  • Monthly variations due to seasonal and regional climate dynamics.

B. Fig. 5.2: Sea Level Change (1880-2020)

• Shows: Global sea level rise (~50 mm since 1990s, ~3 mm/year).
• Key Points:
  • ~225 mm rise around 2015-2020.
  • Correlates with rising temperatures (melting ice, thermal expansion).
  • Indicates accelerating climate change impacts.

C. Fig. 5.4: CO2 Concentration (1900-2017)

• Shows: CO2 levels in ppm, rising from ~300 ppm (1900) to >400 ppm (2017).
• Key Points:
  • Phenomenal increase since the 1950s.
  • Causes: Fossil fuel burning, deforestation, industrialization.
  • Impacts: Health, agriculture, air pollution, and global warming.