Climate Change: Causes & Impacts

An exploration of the driving forces behind our changing climate and its far-reaching consequences.

Understanding the causes and multifaceted impacts of climate change is crucial for appreciating the urgency of the problem and for formulating effective responses. The current rapid warming trend is overwhelmingly attributed to human activities.

A. Causes of Climate Change

I. Natural Causes (Climate Variability)

These factors influence climate over geological timescales but don't explain current rapid warming.

Variations in Solar Output

Sun's energy output varies (e.g., ~11-year solar cycle). Satellite data since 1970s show no net increase to explain current warming. Recent solar activity has been low while temperatures rise.

Milankovitch Cycles

Long-term orbital changes driving past ice ages. Operates on too long timescales (10,000s-100,000s years) for current warming.

  • Eccentricity: Orbit shape (~100,000 yrs)
  • Obliquity: Axial tilt (~41,000 yrs)
  • Precession: Axis wobble (~26,000 yrs)

Volcanic Eruptions

Large eruptions inject SO₂ (sulfate aerosols) causing short-term cooling (1-3 yrs, e.g., Mt. Pinatubo ~0.5°C). CO₂ release is minimal compared to human emissions.

Plate Tectonics

Continental drift over millions of years, affecting ocean currents and long-term climate patterns. Geological timescales.

Ocean Variability

Natural fluctuations like ENSO (El Niño) and PDO cause short-term (years-decades) regional/global variations, but not the long-term warming trend.

II. Anthropogenic (Human-Caused) Causes

The dominant drivers of current rapid climate change, primarily through the enhanced greenhouse effect.

Increased Greenhouse Gases (GHGs)

Primary driver of current global warming.

For electricity, transport, industry, heating/cooling. Releases vast CO₂ (most significant), CH₄, N₂O.

Reduces CO₂ absorption (loss of carbon sinks). Burning/decomposition releases stored CO₂. Alters soil carbon & albedo.

CH₄ (Methane): Livestock digestion, manure, rice cultivation.

N₂O (Nitrous Oxide): Nitrogen fertilizers, manure management.

F-gases (HFCs, PFCs, SF₆, NF₃): Potent GHGs from refrigerants, solvents, etc.

CO₂: Cement production (calcination).

Other CH₄ & N₂O emissions.

CH₄: Landfill decomposition.

CH₄ & N₂O: Wastewater treatment.

CO₂: Waste incineration.

Aerosols (Particulate Matter)

Complex effects:

  • Cooling Effect (most aerosols, e.g., sulfates): Reflect solar radiation, modify clouds. Partially offsets GHG warming.
  • Warming Effect (e.g., black carbon/soot): Absorbs solar radiation, reduces snow/ice albedo.

Overall net effect estimated as cooling (with uncertainty). Reducing aerosol pollution could unmask more GHG warming.

Changes in Land Surface Albedo

Albedo = surface reflectivity. Lighter surfaces (snow, ice) = high albedo; darker (forests, oceans) = low albedo. Deforestation, urbanization, melting ice alter albedo and energy balance.

B. Impacts of Climate Change

Impacts are observed globally, interconnected, and projected to intensify. They can create cascading effects.

I. Physical Impacts

Rising Global Temperatures

Increased average land/ocean temperatures.

More frequent, intense, longer heatwaves (health, agriculture, ecosystem risks).

Changes in temperature extremes.

Changes in Precipitation

Increased variability: intense rainfall/floods in some regions, severe droughts in others.

Shifts in seasonal patterns affecting water availability.

Melting Ice and Snow (Cryosphere)

Threatens water supply, increases GLOF risk, contributes to sea-level rise (Greenland, Antarctica).
Impacts ecosystems, weather, infrastructure. Releases CO₂/CH₄ (positive feedback).

Sea Level Rise

Caused by thermal expansion & melting land ice.

Impacts: Coastal inundation/erosion, flooding, salinization, displacement, infrastructure damage. SIDS vulnerable.

Ocean Acidification

Oceans absorb CO₂, forming carbonic acid, lowering pH.

Hinders shell/skeleton formation in marine calcifiers (corals, shellfish). Disrupts food webs.

Extreme Weather Events

More frequent/intense heatwaves, heavy precipitation/floods, droughts, intense tropical cyclones, wildfires.

II. Impacts on Ecosystems & Biodiversity

Species Range & Phenology Shifts

Species shift distributions (poleward, higher altitude). Changes in life cycle timing (flowering, migration). Can cause ecological mismatches.

Habitat Degradation & Loss

Direct alteration (coral bleaching, permafrost thaw). Exacerbates other habitat loss factors (e.g., drought + fire).

Increased Extinction Risk

Species unable to adapt/move fast enough face extinction. Island, mountain, polar species highly vulnerable.

Spread of Pests & Diseases

Warmer conditions expand ranges of disease vectors (mosquitoes, ticks) and agricultural pests.

III. Impacts on Human Systems

Human Health

Heat stress, vector-borne diseases, malnutrition, respiratory illnesses, mental health impacts.

Agriculture & Food Security

Crop yield changes, livestock impacts, fisheries disruption, threats to global food security.

Water Resources

Changes in water availability/quality, reduced reliability from snow/glaciers, increased demand, saltwater intrusion.

Infrastructure & Settlements

Damage from extreme weather, sea-level rise, permafrost thaw. Risks to coastal cities.

Economic Impacts

Losses from disasters, reduced productivity, infrastructure damage, healthcare costs, tourism impacts. Threat to global economic stability.

Social Impacts

Displacement/migration, increased poverty/inequality, resource conflicts, impacts on Indigenous peoples, security risks ("threat multiplier").

Differential Impacts

Impacts are not uniform. Developing countries, SIDS, Arctic regions, and marginalized communities are often most vulnerable due to location, dependence on climate-sensitive sectors, and limited adaptive capacity.

Feedback Loops

Illustrative GHG Contributions (Conceptual)

CO₂ (Fossil Fuels):
CH₄ (Agriculture):
N₂O (Fertilizers):
F-Gases:

Note: Proportions are illustrative.

UPSC Exam Relevance

Prelims Focus

  • Natural vs. Anthropogenic causes.
  • Major GHG sources, Global Warming Potential (GWP).
  • Impacts: Coral bleaching, ocean acidification, sea-level rise, permafrost thaw.
  • Concepts: Albedo, Milankovitch cycles, ENSO.
  • Feedback loops.

Mains Focus (GS-I, GS-III)

  • Anthropogenic causes & diverse impacts on India.
  • Ocean acidification: phenomenon & consequences.
  • Impacts on Indian agriculture & water resources; adaptation strategies.
  • Climate change as a developmental & security challenge.
  • Linkages to disaster management (extreme weather).

Related Previous Year Questions (PYQs) Insights

  • Factors for 'water stress' (climate change exacerbates).
  • Importance of 'Blue Carbon' initiative.
  • 'Climate Neutral Now' initiative.
  • Questions on GHGs, sources, GWP, specific impacts.
  • "Climate Change is a global problem. How India will be affected...?" (UPSC Mains 2017)
  • Causes of mangrove depletion (sea-level rise relevant).
  • Consequences of 'Dead Zones' (warming exacerbates).
  • Causes/effects of landslides (climate change can increase risk).