Overview & Definition (परिचय तथा परिभाषा)

Climate change refers to long‑term alterations in temperature, precipitation, wind patterns, and other aspects of the Earth’s climate system. While natural variations have occurred over geological time, the term today predominantly denotes the rapid warming observed since the mid‑20th century, driven largely by human activities that increase greenhouse gas (GHG) concentrations in the atmosphere.

Core Concepts (मुख्य अवधारणाहरू)

1. Greenhouse Effect

The greenhouse effect is a natural process where gases such as carbon dioxide (CO₂), methane (CH₄), and water vapour trap infrared radiation, keeping the planet warm enough to sustain life. Human‑induced emissions amplify this effect, leading to a net increase in global temperatures.

2. Drivers of Climate Change

• Anthropogenic Sources: Fossil‑fuel combustion, deforestation, industrial processes, and agricultural practices.
• Natural Sources: Volcanic eruptions, solar radiation variability, and natural greenhouse gas releases.

3. Global Warming vs. Climate Change

Global warming describes the rise in average surface temperature, whereas climate change encompasses broader changes, including sea‑level rise, altered precipitation patterns, and increased frequency of extreme weather events.

4. Climate Feedback Loops

Feedback mechanisms can either amplify (positive feedback) or dampen (negative feedback) climate change. Examples include ice‑albedo feedback, permafrost methane release, and increased cloud cover.

Key Points / Rules / Functions

• Atmospheric CO₂ levels have risen from ~280 ppm pre‑industrial to over 420 ppm today.
• The Intergovernmental Panel on Climate Change (IPCC) estimates a 1.1 °C rise above pre‑industrial levels as of 2023.
• Every 1 °C of warming increases the probability of extreme heatwaves, droughts, and heavy rainfall.
• Sea levels have risen about 20 cm since 1900, with an accelerating rate of ~3.3 mm per year.
• Climate change impacts are uneven; low‑lying coastal regions and vulnerable economies face disproportionate risks.

Comparison / Summary Table

Practical Application / Real‑World Relevance

Understanding climate change is essential for:

1. Public Policy: Designing mitigation (e.g., renewable energy incentives) and adaptation strategies (e.g., flood‑resilient infrastructure).
2. Exam Preparation: PSC, TSC, and other competitive exams frequently ask about causes, impacts, and mitigation measures.
3. Professional Roles: Computer operators and data analysts can contribute by managing climate‑related datasets, supporting GIS mapping, and developing monitoring dashboards.
4. Local Context – Nepal: Glacial melt in the Himalayas threatens water security; increased monsoon variability affects agriculture and disaster risk management.

"Climate change is not a distant threat; it is a present reality that shapes every sector of society." – IPCC Summary for Policymakers

Quick Review Questions & Answers (अभ्यासका लागि प्रश्नोत्तर)

Short Answer

1. What is the greenhouse effect? A natural process where certain atmospheric gases trap heat, keeping Earth warm enough for life.
2. Name two major anthropogenic sources of CO₂. Fossil‑fuel combustion and deforestation.
3. How much has global average temperature increased since pre‑industrial times? Approximately 1.1 °C.

Multiple‑Choice Questions

1. Which of the following is a positive feedback mechanism that accelerates warming?
   
   • A) Increased cloud albedo
   • B) Ice‑albedo feedback
   • C) Oceanic carbon uptake
   • D) Volcanic aerosol cooling
   Answer: B
2. Sea‑level rise is primarily caused by:
   
   • A) Expansion of seawater as it warms
   • B) Melting of land‑based ice
   • C) Both A and B
   • D) Changes in ocean currents
   Answer: C
3. In Nepal, accelerated glacial melt most directly threatens which sector?
   
   • A) Information technology
   • B) Tourism
   • C) Agriculture and water supply
   • D) Manufacturing
   Answer: C