Climate Change: Causes, Evidence and the Global Response

1. Climate has always changed: proxies, ice ages and the Holocene

Read the detailed note →

• Climate change means a long-term change in average weather. It has happened naturally through Earth's history. Since the industrial era, human greenhouse gas emissions drive it. Class 11 calls it "a natural and continuous process".
• Climate proxies are indirect records of past climate:
• glacial landforms in high mountains and high latitudes, which show where glaciers advanced and retreated
• sediments in glacial lakes (warm and cold periods) and tree rings (wet and dry years)
• historical records

• Beyond NCERT: ice cores (EPICA Dome C goes back about 800,000 years and shows CO2 and temperature rising and falling together), pollen, corals, cave stalagmites and ocean sediments.

• Glacial and interglacial periods: these are cold phases when ice sheets spread and warmer phases when they retreat. The Earth was warm 500–300 million years ago (Cambrian, Ordovician, Silurian).

• Pleistocene epoch (about 2.58 million to 11,700 years ago): ice ages came and went many times. NCERT says the last peak glaciation was about 18,000 years ago. Now the Last Glacial Maximum is dated about 26,000–19,000 years ago, with its peak near 21,000.
• Holocene: the present warm interglacial (NCERT: began 10,000 years ago; now: 11,700 years ago). Its latest stage, the Meghalayan Age (from 4,200 years ago), was defined in 2018 from a stalagmite in Mawmluh Cave, Meghalaya. The proposed "Anthropocene" epoch was rejected by the IUGS in March 2024.
• Past climate of Rajasthan: the region was wet and cool around 8,000 BC and wetter in 3,000–1,700 BC. It was the Harappan heartland in 2,000–1,700 BC. It has grown drier since then. The 4.2 kiloyear dry event is one explanation offered for the Harappan decline.

2. Climate in the recent past: warm spells, little ice ages and great droughts

Read the detailed note →

• Medieval Warm Period (about 950–1250, beyond NCERT): Europe had warm, dry 10th and 11th centuries, and the Vikings settled Greenland.
• Little Ice Age (1550 to about 1850): a cool period. Alpine glaciers advanced, the Thames froze and crops failed.
• Beyond NCERT, it is linked to the Maunder Minimum, a spell of very few sunspots (1645–1715).
• It is also linked to volcanoes. Tambora (1815) caused the "year without a summer" of 1816.

• Both episodes were regional and smaller than today's warming.

• Sahel drought (1967–1977, returning in the 1980s): the Sahel is the belt south of the Sahara. The drought brought famine and mass deaths. It was linked to Atlantic sea-surface temperatures and to land degradation. It led to the UN Convention to Combat Desertification (1994).

• Dust Bowl (1930s): drought hit the south-western Great Plains of the USA. Ploughed-up grassland made it worse. Topsoil blew away and farm families moved west. It led to the US Soil Conservation Service (1935).
• Variability: Class 11 calls the 1990s the warmest decade of the 20th century, and it brought some of the worst floods.
• 20th-century trend: temperatures rose from about 1885 to 1940, then rose more slowly. Beyond NCERT: aerosol pollution ("global dimming") partly hid warming after 1940.

3. Causes of climate change: astronomical and terrestrial

Read the detailed note →

• Causes of climate change fall into two groups:
• astronomical: changes in solar output (sunspots) and Milankovitch cycles

• terrestrial: volcanism and, most importantly, the human-caused rise in greenhouse gases

• Sunspots are dark, cooler patches on the Sun. Their number rises and falls in a cycle of about 11 years.

• Some meteorologists link more sunspots to cooler, wetter, stormier weather. Class 11 says these findings are "not statistically significant".
• Solar Cycle 25 began in December 2019 and peaked around 2024–25.
• India's Aditya-L1 (launched 2 September 2023; at the L1 point since 6 January 2024) studies the Sun.

• Solar output has been flat or slightly falling since 1950 while temperatures rose, so the Sun cannot explain recent warming.

• Milankovitch cycles (Milutin Milanković, Serbian scientist) are slow changes in Earth's orbit and axis that alter insolation:

• eccentricity (shape of the orbit): about 100,000 and 413,000 years
• obliquity (axial tilt, 22.1°–24.5°, now 23.44° and falling): about 41,000 years
• precession (wobble of the axis): about 26,000 years

• They set the pace of ice ages over thousands of years, not over decades.

• Volcanism and climate:

• Eruptions put sulphur dioxide into the stratosphere. It forms sulphate droplets that reflect sunlight and cool the Earth for a few years.
• Pinatubo (Philippines, 1991) cooled the globe by about 0.5 °C. El Chichón (Mexico, 1982) also had a cooling effect. Class 11 spells these "Pinatoba and El Cion".
• Volcanoes emit well under 1% as much CO2 as humans.

4. The greenhouse effect and greenhouse gases

Read the detailed note →

• Greenhouse effect: air lets incoming shortwave sunlight through but absorbs outgoing longwave heat. It works like glass in a greenhouse or a closed car in summer.
• The natural effect keeps Earth about 33 °C warmer, at roughly 14–15 °C instead of –18 °C.

• Humans have added gases "in just a few centuries" (Class 7), which makes the effect stronger.

• Greenhouse gases are gases that absorb longwave heat. Class 11 lists CO2, CFCs, methane, nitrous oxide and ozone. Water vapour is the largest natural one, but it acts as a feedback, not a driver.

• Global warming potential (GWP) compares the heat a gas traps over 100 years with the same mass of CO2 (GWP = 1).

Gas	Main sources	Lifetime	GWP (100 yr)
CO2	fossil fuels, deforestation	centuries	1
Methane	paddy, livestock, wetlands, landfills, gas leaks	~12 yr	~28
Nitrous oxide	fertilisers, manure	>100 yr	~270 (also destroys ozone)
Chlorofluorocarbons	refrigerants, aerosol sprays	long	thousands; cause the Antarctic ozone hole

• CO2 levels: NCERT says CO2 rises about 0.5% a year. Now it rises about 2.3–2.5 ppm a year and reached about 424 ppm in 2024, against 280 ppm before industry (verify current).
• Ozone laws: the Montreal Protocol (1987) phased out CFCs. The Kigali Amendment (2016) phases down HFCs; India freezes use in 2028 and cuts 85% by 2047. India has not joined the Global Methane Pledge (COP26).
• Tropospheric ozone forms near the ground from vehicle and factory pollution in sunlight. There it is a greenhouse gas and a pollutant. In the stratosphere, ozone is protective.
• Carbon sink: anything that absorbs more CO2 than it releases, such as forests, oceans and soils. Oceans take about a quarter of emissions and land about 30%. NCERT gives 20–50 years for CO2 to adjust to changes in sources and sinks, but much CO2 lasts for centuries.
• Climate sensitivity: the warming from doubling CO2 over its pre-industrial level. IPCC AR6's best estimate is 3 °C (likely range 2.5–4 °C).
• Carbon budget: the CO2 that can still be emitted for a given warming limit. AR6 gave about 500 GtCO2 from 2020 for a 50% chance of staying under 1.5 °C. Only a few years of current emissions remain (verify current).

5. Global warming: the record, the evidence and the risks

Read the detailed note →

• Global warming is the rise in Earth's average surface temperature, mainly from greenhouse gases.
• Global temperature record:
• NCERT: the world average is about 14 °C. Temperatures rose about 0.4 °C in each of 1901–44 and 1977–99, about 0.6 °C by 2000, and 1998 was the warmest year.
• Now: 2011–2020 was about 1.1 °C above 1850–1900 (AR6).
• WMO: 2024 was the warmest year on record, about 1.55 °C above pre-industrial. It was the first calendar year above 1.5 °C. One year does not breach the Paris goal, which uses 20-year averages. 2025 ranked among the three warmest years (verify current).

• India: 2024 was its warmest year since 1901 (IMD). In early 2025 temperatures were 1–3 °C above normal, giving a short, mild winter that hurt crops and small industries (Class 7).

• Sea-level rise comes from melting land ice and from warming water expanding.

• NCERT projects 48 cm by 2100. AR6 projects 0.3–0.6 m under low emissions and 0.6–1.0 m under very high emissions.
• Sea level has risen about 20 cm since 1901.

• At risk: deltas (Ganga-Brahmaputra, Mekong, Nile), the Maldives, Tuvalu and Kiribati, and Mumbai, Kolkata and Chennai.

• Arctic amplification: the Arctic has warmed nearly four times faster than the globe since 1979. Melting ice exposes darker sea, which absorbs more sunlight (ice-albedo feedback). September sea ice is shrinking about 12–13% per decade.

• Glacier retreat in the Himalaya:
• ICIMOD (2023) found Hindu Kush Himalayan glaciers melted 65% faster in 2011–20 than in the decade before. They may lose 30–50% of their volume by 2100 even at 1.5–2 °C.
• This threatens the Indus, Ganga and Brahmaputra.

• It also creates new glacial lakes that can burst (Kedarnath 2013; South Lhonak, Sikkim, 2023).

• Climate tipping points are thresholds after which a system changes suddenly and often cannot recover. Examples: the Greenland and West Antarctic ice sheets, the Amazon, permafrost, the AMOC (a major Atlantic ocean current) and warm-water coral reefs. The 2025 Global Tipping Points Report judged that coral reefs have likely crossed theirs (verify current).

6. Climate change and India: lives, floods and individual action

Read the detailed note →

• Class 9 definition: climate change is a long-term change in temperature, rainfall and wind, caused mainly by human activities: burning fossil fuels, deforestation and industrial pollution.
• Carbon footprint: the total greenhouse gas released by a person, product, organisation or country, counted in CO2-equivalent. Class 9's "My Carbon Footprint" activity scores transport, electricity, water and plastics.
• India emits about 2 tonnes CO2 per person a year. The world average is about 4.7 and the USA about 14.

• India is the third-largest emitter in total, but has only about 3–4% of cumulative historical CO2 (verify current).

• Punjab floods 2025 (Class 9 case study):

• Natural causes: heavy monsoon rain, made worse by western disturbances, fell over Punjab, Himachal Pradesh and J&K. The Satluj, Beas, Ravi and Ghaggar overflowed.
• Human causes: weak, old dhussi bandh (earthen embankments), building on floodplains, silted rivers and dams, and late or unclear warnings.
• Effects: deaths, relief camps, drowned paddy, dead livestock, broken roads, bridges and border fencing, and waterborne disease.

• Lesson: warming makes heavy rain more likely, while poor land and water management turns that rain into a disaster.

• Climate change mitigation means cutting the causes of warming: lower emissions, renewables, energy efficiency, tree planting and sustainable lifestyles. Class 7 notes it often clashes with the wish for growth and consumption.

• Climate change adaptation means adjusting to change to reduce harm. Resilience is the ability to withstand a shock or recover quickly. Examples:
• heat action plans (Ahmedabad 2013, the first in South Asia)
• climate-resilient seeds
• better forecasts through the National Monsoon Mission and Mission Mausam (approved September 2024)
• mangrove planting under MISHTI (2023)

7. The international regime: UNFCCC, CBDR, Kyoto and the IPCC

Read the detailed note →

• Intergovernmental Panel on Climate Change (IPCC): set up in 1988 by WMO and UNEP. It assesses climate science for governments and does no research of its own.
• AR1 (1990) fed into the UNFCCC. AR4 (2007) shared the Nobel Peace Prize with Al Gore.
• AR6 (2021–23) said human influence has "unequivocally" warmed the climate.
• Special reports: 1.5 °C (2018), Ocean and Cryosphere (2019), Land (2019).

• The seventh cycle, under chair Jim Skea, includes a Special Report on Cities (verify current).

• United Nations Framework Convention on Climate Change (UNFCCC): opened at the Rio Earth Summit in 1992 and in force since 21 March 1994. Its secretariat is in Bonn, and parties meet yearly at the COP (COP1 was in Berlin, 1995).

• Aim (Article 2): stabilise greenhouse gases at a safe level.

• Groups: Annex I (industrialised countries), Annex II (rich countries that must pay), non-Annex I (developing countries, including India).

• Common but differentiated responsibilities (CBDR-RC, Article 3): all countries must act, but developed countries emitted most of the gases and have more money, so they must lead and help others. This is India's main negotiating principle, along with equity and climate justice.

• Kyoto Protocol: adopted at COP3 in 1997 and in force on 16 February 2005.
• Binding targets only for industrialised (Annex B) countries: an average cut of about 5% below 1990 levels in 2008–12. NCERT says 35 countries and 141 ratifications, which was the 2005 count.
• Market tools: emissions trading, Joint Implementation and the Clean Development Mechanism (India was a big CDM host).
• Weaknesses: the USA never ratified, Canada left in 2011, and big developing emitters had no targets.
• The Doha Amendment (2012) added a second period (2013–20) but only came into force on 31 December 2020.

8. The Paris Agreement and the COPs since: NDCs, stocktake, loss and damage, finance

Read the detailed note →

• Paris Agreement: adopted at COP21 on 12 December 2015 and in force on 4 November 2016. India ratified on 2 October 2016.
• Goal: keep warming "well below 2 °C" and try for 1.5 °C.
• Key articles: Article 7 adaptation, 8 loss and damage, 9 finance, 13 transparency.
• Differentiation stays, but in softer words: "in the light of different national circumstances".

• The USA withdrew again from January 2026 (verify current).

• Nationally Determined Contributions (NDCs): each country's own climate pledge, sent every five years and stronger each time (the "ratchet").

• Net zero: emissions balanced by removals. Targets: EU 2050, China 2060, India 2070.
• Global Stocktake (Article 14): a review of joint progress every five years.
• The first ended at COP28 in Dubai (2023). It called for "transitioning away from fossil fuels in energy systems", tripling renewables and doubling the rate of energy-efficiency gains by 2030.

• The next stocktake is in 2028.

• Loss and damage fund: helps poor countries cope with harm that adaptation cannot prevent. It was agreed at COP27 in Sharm el-Sheikh (2022) and started working at COP28 (2023). Pledges are small compared with the need.

• Green Climate Fund: set up at COP16 in Cancún (2010), based in Songdo, South Korea. The old goal of $100 billion a year by 2020 was met only in 2022 (OECD).
• New Collective Quantified Goal (NCQG), COP29 Baku (2024): developed countries are to lead in raising at least $300 billion a year by 2035, within a call to reach $1.3 trillion. India called it too little.
• COP30 Belém (Brazil, November 2025):
• The "Global Mutirão" decision called for at least tripling adaptation finance by 2035.
• The Tropical Forests Forever Facility was launched and a just-transition mechanism was agreed.
• No fossil-fuel roadmap made it into the formal text.
• COP31 (2026) is in Antalya, Turkey, with Australia leading the negotiations (verify current).

9. Markets, forests, technology and trade: Article 6, REDD+, CCS and CBAM

Read the detailed note →

• Article 6 carbon markets let countries cooperate to meet their targets:
• 6.2: one country can transfer emission cuts to another (ITMOs). "Corresponding adjustments" stop the same cut being counted twice.
• 6.4: a UN-supervised crediting system that replaces the CDM.
• 6.8: cooperation without markets.

• The rules were finished at COP29 (2024). India has listed activities open to 6.2 deals, such as green hydrogen, offshore wind and storage (verify current).

• REDD+ (Reducing Emissions from Deforestation and forest Degradation, plus conservation, sustainable management and enhancement of forest carbon stocks): pays developing countries for verified forest results.

• Framework: the Warsaw Framework (COP19, 2013) and Paris Article 5.

• India: National REDD+ Strategy (2018). Its NDC aims for an extra forest sink of 2.5–3 billion tonnes CO2-equivalent by 2030.

• Carbon capture and storage (CCS/CCUS): CO2 is captured from plants, factories or directly from the air, then stored underground or used.

• Examples: Sleipner, Norway (since 1996) and direct-air-capture plants in Iceland. NITI Aayog published a CCUS report in 2022.

• Critics: it can be an excuse to delay giving up fossil fuels. Supporters: it is needed for cement and steel.

• Carbon Border Adjustment Mechanism (CBAM): an EU charge on the carbon emitted in making imports of iron and steel, aluminium, cement, fertilisers, electricity and hydrogen.

• Reporting began in October 2023 and charging in January 2026.
• India calls it a unilateral trade barrier that goes against CBDR (verify current).

10. India's response: NAPCC, NDC, Panchamrit, ISA, LiFE and the carbon market

Read the detailed note →

• National Action Plan on Climate Change (NAPCC), 30 June 2008, has eight missions: 1. Solar 2. Enhanced Energy Efficiency (includes the PAT scheme) 3. Sustainable Habitat 4. Water 5. Himalayan Ecosystem 6. Green India 7. Sustainable Agriculture 8. Strategic Knowledge for Climate Change

States also make State Action Plans.

• National Solar Mission (2010): its target was raised in 2015 to 100 GW by 2022, which was reached later. Solar is central to the 500 GW non-fossil goal.
• National Mission for Sustaining the Himalayan Ecosystem (NMSHE): studies glaciers and ecosystems, sets up climate cells in Himalayan states and records traditional knowledge.
• Green India Mission: raise forest and tree cover on 5 million ha and improve forest quality on another 5 million ha.
• Panchamrit (COP26 Glasgow, 2021), five pledges:
• 500 GW non-fossil capacity by 2030
• 50% of energy needs from renewables by 2030
• 1 billion tonnes less projected emissions by 2030
• 45% lower emission intensity of GDP than 2005 by 2030

• net zero by 2070

• NDC and progress:

• The updated NDC (August 2022) promises a 45% cut in emission intensity and about 50% of power capacity from non-fossil sources by 2030.
• India's long-term low-emission strategy (LT-LEDS) was submitted at COP27 (2022).

• Emission intensity fell 36% between 2005 and 2020. Non-fossil sources passed 50% of installed capacity in mid-2025, five years early. The 2035 NDC is due (verify current).

• Carbon Credit Trading Scheme (CCTS): notified in June 2023 under the Energy Conservation Act 2001 (amended 2022) and run by the Bureau of Energy Efficiency (BEE).

• It has a compliance market, where heavy industries get emission-intensity targets, and a voluntary offset market.

• Trading is expected around 2026 (verify current). The Green Credit Programme (2023) rewards voluntary actions such as tree planting.

• International Solar Alliance (India and France, COP21, 2015): headquarters in Gurugram, framework agreement in force since 2017.

• Mission LiFE (launched October 2022): "mindful, not mindless, consumption".

---

Exam angles

Prelims — high-yield facts and traps

• Milankovitch cycles: eccentricity about 100,000 years, obliquity about 41,000, precession about 26,000. The sunspot cycle is about 11 years. Pinatubo (1991) cooled the globe by about 0.5 °C.
• "Sunspot–weather links are statistically proven": FALSE (Class 11).
• CO2 is the largest GHG by amount. Methane lasts about 12 years with GWP about 28. N2O has GWP about 270 and also destroys ozone. CFCs are both GHGs and ozone destroyers.
• Ozone near the ground is a GHG and pollutant. In the stratosphere it protects us.
• Montreal (1987) covers ozone-depleting substances, Kigali (2016) covers HFCs and Kyoto (1997) covers GHGs. "India joined the Global Methane Pledge": FALSE.
• Key dates: IPCC 1988 (WMO + UNEP); UNFCCC 1992, in force 1994; Kyoto 1997, in force 2005; Paris 2015, in force 2016; GCF 2010 (Songdo).
• Loss and damage fund: agreed at COP27, working from COP28. NCQG ($300 billion by 2035) at COP29 Baku. COP30 in Belém.
• NAPCC (2008) has eight missions. Net zero by 2070. NDC: 45% intensity cut versus 2005 by 2030. ISA headquarters: Gurugram. CCTS is run by BEE under the Energy Conservation Act.
• CBAM covers steel, aluminium, cement, fertilisers, electricity and hydrogen.
• 2024 was the warmest year (about 1.55 °C). "1998 is still the warmest year" (NCERT): FALSE. "One year above 1.5 °C breaches Paris": FALSE.
• The Arctic is warming nearly four times as fast as the globe.
• Past climate: Little Ice Age 1550–1850; Sahel drought 1967–77; Dust Bowl 1930s; Meghalayan Age defined from a Mawmluh Cave stalagmite. The Holocene began 11,700 years ago (NCERT: 10,000).

Mains — GS-I and GS-III themes

1. Natural versus human causes of climate change: how scientists show that recent warming comes from humans.
2. CBDR-RC and climate justice: from Kyoto's binding split to Paris's self-chosen pledges, and who pays for loss and damage.
3. India's vulnerability: monsoon extremes, Himalayan glaciers and GLOFs, heat waves and coasts. The Punjab 2025 floods as a disaster with both natural and human causes.
4. India's 2070 net zero versus development and energy security: coal, renewables and the carbon market.
5. CBAM: green protectionism or fair climate policy?
6. Mitigation versus adaptation: why adaptation finance lags and why it matters for the Global South.
7. Tipping points and why urgent action is needed.

Current-affairs hooks

• COP31 (Antalya, 2026): 2035 NDCs, adaptation finance and fossil-fuel roadmaps (verify current).
• India's 2035 NDC, progress towards 500 GW and the start of CCTS trading (verify current).
• WMO and Copernicus annual temperature reports and the long-term 1.5 °C threshold.
• The CBAM charging phase and India-EU trade talks.
• GLOFs, cloudbursts and floods in the Himalaya and Punjab; heat action plans.
• US withdrawal from Paris and its effect on climate finance; IPCC seventh-cycle reports (verify current).