Introduction. Weather changes from day to day, but when such changes in temperature, rainfall, wind patterns and other climatic elements persist over decades, we speak of climate change. In the past, Earth’s climate has always undergone slow natural variations. However, in recent decades, the rate and pattern of change have become unusually rapid, largely due to human activities. Climate change today is not only a scientific issue but also a major environmental, economic and social challenge, affecting every country and every sector of society. Hence, it occupies a central place in Environmental Studies.
Meaning and concept of climate and climate change
Before defining climate change, it is useful to distinguish between weather and climate:
- Weather: The day-to-day, short-term condition of the atmosphere (temperature, rainfall, humidity, wind, etc.) at a particular place.
- Climate: The long-term average pattern of weather, usually calculated over a period of 30 years or more, for a region.
Definition of climate change (exam-oriented):
“Climate change refers to a significant, long-term alteration in the average weather patterns or climatic conditions of the Earth or a particular region, occurring over decades or longer, due to natural factors and human activities.”
In present-day discussion, climate change usually refers to human-induced (anthropogenic) changes that alter the composition of the atmosphere and modify the natural climate system.
Key elements of the concept of climate change
- It involves changes in averages, variability and extremes of climatic variables—such as temperature, rainfall, frequency of heat waves, storms and droughts.
- It is not a short-term fluctuation but a persistent trend over decades.
- It is closely linked with the greenhouse effect, global warming, changes in the hydrological cycle, melting of ice and sea-level rise.
- It has global causes and global consequences, but the impacts are felt differently at local and regional levels, depending on geography and socio-economic conditions.
Major causes of climate change
The question specifically asks for natural as well as human-induced causes. Both act together, but in the present era human influences dominate.
I. Natural causes of climate change
Over geological time scales (thousands to millions of years), several natural factors have caused changes in Earth’s climate:
1. Variations in solar output
- The sun is the primary source of energy driving Earth’s climate system. Small variations in solar radiation (e.g., due to sunspot cycles) can influence climate.
- Periods of slightly lower solar activity have been associated with cooler climates in the past (e.g., “Little Ice Age” in Europe).
2. Changes in Earth’s orbital parameters (Milankovitch cycles)
- Over tens of thousands of years, slow changes in the shape of Earth’s orbit (eccentricity), the tilt of its axis and the wobble (precession) alter the distribution of solar energy received.
- These cycles have been linked with the advance and retreat of ice ages in geological history.
3. Volcanic eruptions
- Large volcanic eruptions inject ash and sulphur-containing gases into the stratosphere, which form aerosol particles.
- These aerosols reflect sunlight and can cause temporary cooling of the Earth’s surface for a few years after a major eruption.
4. Natural variability in ocean–atmosphere systems
- Phenomena such as El Niño–Southern Oscillation (ENSO) produce periodic warming or cooling of sea-surface temperatures, affecting rainfall and temperature patterns globally.
- These are examples of natural climate variability on shorter time scales.
While these natural factors continue to operate, scientific evidence shows that the recent, rapid warming trend cannot be explained by natural causes alone and is mainly due to human activities.
II. Human-induced (anthropogenic) causes of climate change
1. Increase in greenhouse gas concentrations
The most important human cause is the enhanced greenhouse effect. Certain gases in the atmosphere— carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), ozone (O₃) and industrial gases like chlorofluorocarbons (CFCs)—trap outgoing long-wave radiation and keep the Earth warm. This natural greenhouse effect is essential for life, but human activities have increased the concentration of these gases, leading to additional warming.
- Burning of fossil fuels: Coal, oil and natural gas used for electricity, transport and industry release large amounts of CO₂.
- Deforestation and land-use change: Cutting down forests for agriculture, urbanisation and logging reduces the planet’s capacity to absorb CO₂ and releases carbon stored in trees and soil.
- Agriculture and livestock: Rice cultivation, enteric fermentation in cattle and sheep, and improper manure management produce methane; fertiliser use increases nitrous oxide emissions.
- Industrial processes: Cement production, chemical industries and use of synthetic gases (CFCs, HCFCs, HFCs) contribute additional greenhouse gases.
2. Aerosols and particulate pollution
- Human activities emit aerosols (fine particles) like sulphates, nitrates, black carbon (soot) and dust from industries, vehicles and biomass burning.
- Aerosols have complex effects: some cool the atmosphere by reflecting sunlight, while others (black carbon) warm it by absorbing heat and darkening snow and ice surfaces.
3. Changes in land use and land cover
- Urbanisation, intensive agriculture and deforestation alter the albedo (reflectivity) and surface roughness of the land.
- Cities create “urban heat islands” where temperatures are higher than surrounding rural areas due to concrete surfaces, reduced vegetation and waste heat from human activities.
Consequences of climate change
The question requires significant environmental, economic and social consequences at both global and local levels. These aspects are closely interlinked.
I. Environmental consequences
1. Global increase in temperature (global warming)
- The most direct indicator of climate change is the observed rise in average global surface temperature.
- Even an increase of 1–2°C above pre-industrial levels significantly alters weather patterns and affects ecosystems.
2. Melting of glaciers, ice caps and polar ice
- Higher temperatures cause glaciers in mountain ranges (such as the Himalayas) and polar ice sheets in Greenland and Antarctica to melt more rapidly.
- This contributes to sea-level rise, threatening low-lying coastal areas and small island nations.
3. Changes in rainfall patterns and hydrological cycle
- Some regions experience more intense rainfall and floods, while others face more frequent droughts.
- Shifts in timing and intensity of monsoon and other seasonal rains affect agriculture, water availability and ecosystem health.
4. Increased frequency and intensity of extreme weather events
- Climate change is associated with more frequent heat waves, heavy rainfall events, cyclones and storms.
- These events cause loss of life, damage to infrastructure and long-term socio-economic disruption.
5. Impacts on biodiversity and ecosystems
- Many species have specific temperature and moisture requirements. Rapid climate change may exceed their capacity to adapt or migrate.
- Coral reefs are highly sensitive to warming and acidification, leading to coral bleaching and decline of reef ecosystems.
- Shifts in distribution of species, changes in migration patterns and disruption of ecological relationships (pollination, predator–prey interactions) are likely.
II. Economic consequences
1. Impacts on agriculture and food security
- Changes in temperature, rainfall patterns and increased frequency of droughts and floods affect crop yields, cropping seasons and water availability.
- Some crops may benefit in certain regions, but overall climate variability increases the risk of crop failure and threatens food security, especially for small farmers.
2. Damage to infrastructure and property
- Extreme weather events—storms, floods, cyclones—destroy houses, roads, bridges, power lines and other infrastructure.
- Coastal erosion and sea-level rise damage ports, tourism infrastructure and coastal settlements.
3. Economic losses in key sectors
- Sectors such as agriculture, fisheries, forestry, tourism and insurance are particularly sensitive to climate variability.
- Countries may face increased expenditure on disaster relief, adaptation measures and health care, reducing resources available for development.
III. Social consequences
1. Impacts on human health
- Heat waves increase the risk of heat stress, dehydration and cardiovascular problems, particularly among elderly and poor people.
- Changing climate affects the distribution of vector-borne diseases (e.g., malaria, dengue), water-borne diseases and malnutrition due to food insecurity.
2. Displacement and climate-induced migration
- Sea-level rise, coastal erosion, desertification and repeated disasters may force communities to migrate, creating “climate refugees”.
- Such displacement often leads to social conflict, pressure on urban areas and challenges in providing basic services.
3. Inequality and vulnerability
- Climate change affects everyone, but its impacts are not evenly distributed. Poor countries and marginalised communities, who have contributed least to greenhouse gas emissions, are often the most vulnerable.
- Within countries, small farmers, landless labourers, indigenous peoples and urban slum dwellers have fewer resources to adapt, leading to increased inequality.
IV. Global and local dimensions
Climate change is a global phenomenon because greenhouse gases mix in the atmosphere and affect the entire planet. However, impacts are felt locally and regionally:
- Globally, we observe rising mean temperatures, loss of ice cover, sea-level rise and increased frequency of extreme events.
- Locally, a village may experience delayed monsoon, more intense rainfall events, crop failures, drying of local water sources, or increased heat stress in cities.
- Therefore, climate change requires both international cooperation (agreements, protocols) and local adaptation and mitigation measures.
Exam-oriented recap (how to structure the 15-mark answer)
- Begin with a clear distinction between weather and climate, followed by a neat definition of climate change.
- Explain key features of the concept: long-term, significant changes in averages and extremes.
- Write separate headings for natural causes (solar variation, orbital changes, volcanoes, ENSO) and human-induced causes (greenhouse gases from fossil fuels, deforestation, agriculture, industry, aerosols, land-use change).
- Discuss consequences under three main headings: environmental, economic and social, with at least 3–4 points under each.
- Emphasise both global impacts (temperature rise, sea-level, ice melt) and local impacts (monsoon changes, floods/droughts, agricultural stress, health effects).
- Use key terms such as “greenhouse gases”, “global warming”, “extreme weather events”, “vulnerability” and “climate refugees”.
Conclusion: In conclusion, climate change may be defined as a long-term, significant shift in the Earth’s climatic conditions, caused by both natural processes and, increasingly, by human activities such as burning fossil fuels, deforestation and unsustainable development. Its consequences are deep and wide-ranging: it alters ecosystems, threatens biodiversity, affects agriculture and water resources, damages infrastructure, and increases health risks and social inequalities. Although it is a global problem, its impacts are felt very strongly at the local level, including in countries like India. A sound understanding of the concept, causes and consequences of climate change is therefore essential for planning effective mitigation and adaptation strategies and for moving towards truly sustainable and climate-resilient development.