Greenhouse Effect and Human Impact

Climate change refers to long-term shifts in temperatures and weather patterns. Such shifts can be natural, due to changes in the sun’s activity or large volcanic eruptions, or due to anthropogenic activities such as unsustainable industrialization, urbanization and deforestation etc. 

Variations observed in climate: Natural Cycles and Human Impact on Greenhouse Effect

• Our earth has witnessed many variations in climate since the beginning. 
• Geological records: They show alteration of glacial and interglacial periods.
  • The geomorphological features, especially in high altitudes and high latitudes, exhibit traces of advances and retreats of glaciers.
  • The sediment deposits in glacial lakes also reveal the occurrence of warm and cold periods.
  • The rings in the trees provide clues about wet and dry periods.

• Alternate: Many such historical records describe the vagaries in climate. 
  • All this evidence indicates that change in the climate is a natural and continuous process. 
  • But since the 1800s, human activities, including the Greenhouse effect, have been the main driver of the Greenhouse Effect and climate change, primarily due to the burning of fossil fuels like coal, oil and gas and uncontrolled industrial activities. 

Climate in the recent past: Historical Extremes and Global Warming Trends

• Extreme Weather Events in the 1990s: Prevalence of extreme weather events during the 90s.
  • The 1990s recorded the warmest temperature of the century.
  • Some of the worst floods occurred globally during this decade.
• Sahel Region Drought (1967-1977): The Sahel region of the Sahara desert experienced a devastating drought from 1967-1977.
  • Highlighting the impact and variability of climate conditions in the region.
• Dust Bowl in the 1930s (Southwestern Great Plains, USA): Severe drought and the occurrence of the Dust Bowl in the southwestern Great Plains of the United States during the 1930s.
• Significance of this event in the context of climate variability.
• Little Ice Age in Europe (1550-1850): Europe’s experience of the “Little Ice Age” from 1550 to 1850.
  • Describing the prolonged period of cooler temperatures and its impact on the continent.
• Temperature Trends in the 20th Century: Temperature trends from 1885-1940, showing an upward trajectory.
  • After 1940, the rate of temperature increase slowed down gradually.
• Global Temperature Variability: The annual average near-surface air temperature of the world is approximately 14 degrees Celsius.
  • The greatest warming of the 20th century occurred during the periods 1901-44 and 1977-99.
  • Over each of these two periods, global temperatures rose by about 0.4 degrees Celsius.

Causes of Climate Change: Astronomical, Terrestrial, and the Greenhouse Effect

Mainly astronomical and terrestrial factors are responsible for the Greenhouse Effect and climate change. 

Table : Causes of Climate Change

What is Global Warming? – Greenhouse Effect, Global Trends, and Consequences

• Greenhouse Effect: The atmosphere transmits incoming solar radiation but absorbs the majority of long-wave radiation emitted by the Earth’s surface.

• • This phenomenon, known as the greenhouse effect, results in the warming of the atmosphere.

• Global Warming and Greenhouse Gases (GHGs): Long-term warming of the planet’s temperature, referred to as global warming, is primarily attributed to the increasing concentration of greenhouse gases.

• • The alarming rise in global temperatures over the last few decades is a consequence of this enhanced greenhouse effect.

• Temperature Trends: Globally averaged annual mean temperature at the end of the 20th century was approximately 0.6 degrees Celsius higher than that recorded at the end of the 19th century.

• • The year 1998 is noted as the warmest year, potentially spanning not only the 20th century but the entire millennium.

• Impact on Sea Levels: The rise in global temperatures contributes to the melting of glaciers, ice caps, and thermal expansion of the sea.

• • This, in turn, raises sea levels, posing a threat to coastal areas and islands and potentially causing social problems.

• Consequences of Climate Change: The melting of ice and rising sea levels may lead to the inundation of significant portions of coastal areas, impacting ecosystems and human habitation.

• • Recognizing the broader social and environmental implications of these changes.

Greenhouse Gasses (GHGs): Major Contributors and Impact

• Characteristics: The Greenhouse Effect involves Major GHGs include carbon dioxide (CO2), Chlorofluorocarbons (CFCs), methane (CH4), nitrous oxide (N2O), and ozone (O3), contributing to the Greenhouse effect.

• • Nitric oxide (NO) and carbon monoxide (CO) react with GHGs, influencing their atmospheric concentration.
  • The effectiveness of GHGs depends on concentration increase, atmospheric lifetime, and radiation absorption wavelength.

• Specific GHGs: Chlorofluorocarbons (CFCs) are highly effective due to their characteristics.

• • Ozone is effective in absorbing terrestrial radiation in the lower troposphere.

• Carbon Dioxide (CO2) and Emissions: Carbon dioxide is the most prevalent GHG in the atmosphere.

• • Mainly emitted from fossil fuel combustion (oil, gas, and coal).

• Points to Ponder – Climate Change Impact: Climate change affects all climatic groups globally.

• • Identifying the most vulnerable and resilient climatic groups amid the emerging climate change crisis is crucial.

• Forests, Oceans, and CO2: Forests and oceans serve as carbon sinks, absorbing CO2 during growth.

• • Deforestation contributes to increased CO2 concentrations.

• CO2 Dynamics: Atmospheric CO2 takes 20-50 years to adjust to source-to-sink changes.

• • CO2 concentration is rising at approximately 0.5 percent annually.

Efforts initiated for reducing the emission of GHGs into the atmosphere: Mitigating GHG Emissions and Climate Impact

• There are global frameworks and agreements to deal with Greenhouse Effect and climate change, such as the Sustainable Development Goals, the UN Framework Convention on the Greenhouse Effect and Climate Change and the Paris Agreement, Kyoto Protocol etc.
• The most important one among these is the Kyoto protocol proclaimed in 1997. This protocol went into effect in 2005, ratified by 141 nations. Kyoto protocol binded the 35 industrialized countries to reduce their emissions by the year 2012 to 5 per cent less than the levels prevalent in the year 1990.

Global experiences have highlighted the need for a collaborative effort for addressing the Greenhouse Effect and climate change. Many such initiatives can deliver economic benefits while improving our lives and protecting the environment.

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