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Climate change: quick recap

தமிழில் விளக்கம்

Climate change · Quick recap · Fact-checked on 8 November 2026 · how we check

Written with AI from the sources listed at the bottom of this page, then fact-checked by a separate AI.

The whole chapter in one sitting: greenhouse gases, warming and the ozone treaties; the IPCC, the UNFCCC and Kyoto; the Paris Agreement, carbon markets, finance and India's climate action.

Each idea is explained first in Tamil (தமிழ்), ending with the English and Hindi exam terms, followed by the same point in exam English. UPSC Prelims is in English or Hindi, so understand it in Tamil and revise it in English.

மூன்று பகுதிகளின் சாரம் இங்கே ஒரே இடத்தில். முதலாவது அறிவியல்: பசுமை இல்ல விளைவு, புவி வெப்பமயமாதல் கொண்டுவரும் வாயுக்கள், தனிக் கதையான ஓசோன் படலம். இரண்டாவது 1988 முதல் 2013 வரை தூதரக முயற்சி. மூன்றாவது பாரிஸ், சந்தைகள், பணம், நம் நாட்டின் திட்டங்கள். (→ English: greenhouse effect; global warming; ozone layer · हिन्दी: हरितगृह प्रभाव; वैश्विक तापन; ओज़ोन परत)

In exam EnglishClimate change was taught in three parts. Part 1 covered the science: the greenhouse effect, the gases behind global warming and their effects, and the separate story of the ozone layer. Part 2 followed the diplomacy from 1988 to 2013: the IPCC, the climate convention and the Kyoto Protocol. Part 3 covered the Paris Agreement, carbon markets, climate finance and India's own plans. This recap condenses all three for revision; the table below puts the treaties and their dates side by side.

Climate change at a glance
Treaty or body	Adopted / set up	In force	Key point
Vienna Convention	1985	1988	Framework for the ozone layer
Montreal Protocol	1987	1989	Phases out ozone-depleting substances
Kigali Amendment	2016	2019	Phases down HFCs; India freezes 2028
IPCC	1988	—	Assesses science; WMO and UNEP
UNFCCC	1992	1994	Framework; CBDR; Annex I and II
Kyoto Protocol	1997	2005	Binding cuts for Annex B; CDM
Paris Agreement	2015	2016	NDCs by all; stocktake every five years

வெயில் உள்ளே வருகிறது, வெப்பம் வெளியே போக வேண்டும்; பசுமை இல்ல வாயு போர்வை போல அதில் கொஞ்சத்தைத் தடுக்கிறது. நைட்ரஜனும் ஆக்சிஜனும் தடுப்பதில்லை. நாம் அதிகம் சேர்ப்பது கார்பன் டை ஆக்சைடு. புவி வெப்பமாக்கும் திறன் என்றால் ஒவ்வொரு வாயுவும் கார்பன் டை ஆக்சைடைவிட எத்தனை மடங்கு வெப்பம் பிடிக்கும் என்று சொல்லும் அளவு; மீத்தேன் குறுகிய காலத்தில் இன்னும் வலிமையானது. பூமி ஏற்கெனவே சுமார் 1.1 டிகிரி சூடாகிவிட்டது, ஆர்க்டிக் இன்னும் வேகமாக. (→ English: greenhouse gas; global warming potential · हिन्दी: हरितगृह गैस; वैश्विक तापन क्षमता)

In exam EnglishSunlight arrives as short waves; the warmed Earth sends out long-wave infrared, and a greenhouse gas traps part of it. Nitrogen and oxygen do not. Water vapour is the largest natural contributor but follows temperature; carbon dioxide from fossil fuels, cement and deforestation is the main human addition, passing 420 parts per million at Mauna Loa in 2023 (NOAA), against about 280 before industry. The global warming potential compares gases with carbon dioxide over 100 years: methane about 28 (about 84 over 20 years), nitrous oxide about 265, sulphur hexafluoride about 23,500 (IPCC AR5). The IPCC's Sixth Assessment found 2011–2020 about 1.1 °C warmer than 1850–1900, with the Arctic warming more than twice as fast, while sea level rose about 0.20 metres between 1901 and 2018.

ஓசோன் படலம் மேலே குடை போல புற ஊதாக் கதிர்களைத் தடுக்கிறது. 220-க்குக் கீழே போனால் ஓசோன் துளை என்கிறார்கள்; அண்டார்டிகாவில் வசந்தத்தில் திறக்கிறது. CFC போன்ற வேதிப்பொருட்கள் குடையில் ஓட்டை போட்டன. மான்ட்ரியல் நெறிமுறை அவற்றை நிறுத்தியது. அவற்றுக்குப் பதில் வந்த HFC-கள் ஓசோனுக்குக் கேடு இல்லை ஆனால் வெப்பம் கூட்டுகின்றன, அதனால் கிகாலி திருத்தம் அவற்றைக் குறைக்கிறது; நம் நாடு 2028 முதல். (→ English: ozone layer; ozone hole; Montreal Protocol; Kigali Amendment · हिन्दी: ओज़ोन परत; ओज़ोन छिद्र; मॉन्ट्रियल प्रोटोकॉल; किगाली संशोधन)

In exam EnglishThe ozone layer, mostly 15–35 kilometres up in the stratosphere, absorbs harmful ultraviolet light; below 220 Dobson units scientists speak of an ozone hole. CFCs, halons, methyl bromide and HCFCs release chlorine and bromine there, and the Antarctic hole opens in September–October when sunlight returns to polar stratospheric clouds. The Vienna Convention (1985) was the framework and the Montreal Protocol (1987, in force 1989) set phase-out dates, with a Multilateral Fund from 1990; both became the first treaties ratified by every country (2009). Because the substitute HFCs warm the climate, the Kigali Amendment (2016, in force 2019) phases them down by about 80–85 per cent; India freezes in 2028 and cuts 85 per cent by 2047.

காலநிலை மாற்றத்துக்கான அரசுகளிடைக் குழு சொந்தச் சோதனைகள் செய்வதில்லை, வெளியான ஆய்வுகளை எடைபோடுகிறது. காலநிலை மாற்றம் குறித்த ஐநா கட்டமைப்பு உடன்படிக்கை வீட்டின் அஸ்திவாரம் போல: விதிகள், பொதுவான ஆனால் வேறுபட்ட பொறுப்புகள், நாடுகளின் பட்டியல்கள், ஆனால் கட்டாய எண்கள் இல்லை. கியோட்டோ நெறிமுறை பணக்கார நாடுகளுக்கு மட்டும் கட்டாய வெட்டுகள் வைத்தது, சந்தை வழிகள் தந்தது. (→ English: Intergovernmental Panel on Climate Change; UN Framework Convention on Climate Change; common but differentiated responsibilities; Kyoto Protocol · हिन्दी: जलवायु परिवर्तन पर अंतर-सरकारी पैनल; जलवायु परिवर्तन पर संयुक्त राष्ट्र फ्रेमवर्क अभिसमय; साझा किंतु विभेदित उत्तरदायित्व; क्योटो प्रोटोकॉल)

In exam EnglishThe Intergovernmental Panel on Climate Change (1988, WMO and UNEP) assesses published science rather than doing research; its Sixth Assessment closed in 2023 and it shared the 2007 Nobel Peace Prize. The UN Framework Convention on Climate Change was adopted on 9 May 1992, opened for signature at Rio and came into force on 21 March 1994; it set no binding targets but laid down common but differentiated responsibilities and listed Annex I and the smaller Annex II, which owes finance. The Kyoto Protocol (1997, in force 16 February 2005) gave Annex B countries binding cuts for 2008–2012 on six gases, with emissions trading, Joint Implementation and the Clean Development Mechanism; the Doha Amendment set 2013–2020. Cancún (2010) created the Green Climate Fund and Warsaw (2013) the REDD+ framework and the loss and damage mechanism.

பாரிஸ் ஒப்பந்தம் த்தில் ஒவ்வொரு நாடும் தன் தேசிய அளவில் நிர்ணயிக்கப்பட்ட பங்களிப்பு ஐந்து ஆண்டுக்கு ஒருமுறை தருகிறது; தருவது கட்டாயம், அடைவது இல்லை. எல்லோர் முன்னேற்றத்தையும் உலகளாவிய நிலை மதிப்பீடு பார்க்கிறது. நம் நாடு: 2030-க்குள் தீவிரம் 45 சதவீதம் குறைப்பு, பாதி புதைபடிவமல்லாத மின் திறன், 2070 நிகர பூஜ்ஜியம். கார்பன் வரவுத் திட்டம் மின்துறையின் கீழ், பசுமை வரவு சுற்றுச்சூழல் துறையின் கீழ். (→ English: Paris Agreement; nationally determined contribution; global stocktake; net zero 2070 · हिन्दी: पेरिस समझौता; राष्ट्रीय स्तर पर निर्धारित योगदान; वैश्विक स्टॉकटेक; 2070 तक नेट ज़ीरो)

In exam EnglishThe Paris Agreement (12 December 2015, in force 4 November 2016; India ratified 2 October 2016) aims at well below 2 °C with efforts for 1.5 °C. Every party submits a nationally determined contribution every five years, binding to make but not to achieve, reported under a transparency framework and reviewed collectively by a global stocktake, the first at COP28 in 2023. India's 2022 update promises a 45 per cent cut in emissions intensity from 2005 and about 50 per cent non-fossil installed capacity by 2030; net zero is set for 2070. Article 6 carries markets forward; at home the Carbon Credit Trading Scheme (2023) sits under the Energy Conservation Act, the Green Credit Programme under the Environment (Protection) Act. The loss and damage fund was agreed in 2022, and the NAPCC (2008) runs eight missions.

அத்தியாயத்தின் சாரம்: ஓசோன் சிக்கல் எளிதாகத் தீர்ந்தது, ஏனெனில் மாற்றுகள் தயாராக இருந்தன. காலநிலை கடினம்; கியோட்டோ சிலர் மேல் மட்டும் சுமை வைத்தது, பாரிஸ் எல்லோரையும் வாக்குத் தரச் சொன்னது. நியாயம் என்றால் பொதுவான ஆனால் வேறுபட்ட பொறுப்புகள், பண உதவி: இதுவே எப்போதும் பெரிய வாதம். (→ English: common but differentiated responsibilities · हिन्दी: साझा किंतु विभेदित उत्तरदायित्व)

In exam EnglishThe thread through the chapter is a shift in design. Ozone was solved by a framework convention, a protocol with deadlines and money for poorer countries, helped by ready substitutes. Climate followed the same first steps, but Kyoto's binding targets for a 1992 list never held all major emitters, so Paris replaced them with pledges from everyone, checked by transparency and the stocktake. Fairness, through common but differentiated responsibilities and finance, has stayed the central quarrel, and India's own commitments are framed around it.

Exam traps

Ozone depletion does not cause global warming; they are separate problems in separate layers, linked only by gases such as CFCs and HFCs.
HFCs do not harm the ozone layer; the Kigali Amendment phases them down (about 80–85 per cent) because they warm the climate. India's freeze year is 2028.
Methane's GWP is higher over 20 years (about 84) than over 100 years (about 28).
The UNFCCC sets no binding targets; Kyoto's binding targets applied only to Annex B countries. India has never been in Annex I or II.
Kyoto was adopted in 1997 but came into force in 2005; Paris was adopted in 2015 and came into force in 2016.
A Paris NDC is binding to submit and update, not to achieve. India's NDC cuts emissions intensity, not absolute emissions, and its net zero year is 2070.
The Carbon Credit Trading Scheme falls under the Energy Conservation Act; the Green Credit Programme under the Environment (Protection) Act.

Recap

Greenhouse effect: short waves in, long-wave infrared out, part trapped; nitrogen and oxygen are not greenhouse gases.
CO2 passed 420 ppm at Mauna Loa in 2023 (NOAA); warming about 1.1 °C for 2011–2020 over 1850–1900 (IPCC AR6).
GWP (100-year, AR5): methane about 28, nitrous oxide about 265, SF6 about 23,500.
Ozone: hole below 220 Dobson units; Antarctic hole in September–October; Vienna 1985, Montreal 1987, Kigali 2016 (India: freeze 2028, 85 per cent cut by 2047).
IPCC 1988 (WMO, UNEP); UNFCCC 1992, in force 1994; CBDR; Annex I, Annex II.
Kyoto 1997, in force 2005; Annex B targets 2008–2012; six gases; CDM, JI, emissions trading; Doha Amendment 2013–2020.
Paris 2015, in force 2016; well below 2 °C, efforts for 1.5 °C; NDCs every five years; first global stocktake COP28 (2023).
India: 45 per cent intensity cut and about 50 per cent non-fossil capacity by 2030; net zero 2070; CCTS 2023; NAPCC 2008 with eight missions; ISA and CDRI.

Practice questions

Q1. Which one of the following gases is NOT a greenhouse gas?

Methane
Nitrous oxide
Nitrogen
Sulphur hexafluoride

Show answer

Answer: C. Nitrogen

Nitrogen, the main gas of the air, hardly absorbs infrared and so is not a greenhouse gas. Methane, nitrous oxide and sulphur hexafluoride all trap heat and are among the gases counted under the climate treaties, so they cannot be the answer.

Q2. Consider the following statements:
1. Hydrofluorocarbons deplete the stratospheric ozone layer.
2. Under the Kigali Amendment, India is to freeze its HFC consumption in 2028.
Which of the statements given above is/are correct?

1 only
2 only
Both 1 and 2
Neither 1 nor 2

Show answer

Answer: B. 2 only

Statement 2 is correct. Statement 1 is wrong: HFCs contain no chlorine and do not destroy ozone; they were brought under the Montreal Protocol because they are strong greenhouse gases. Option 1 picks the false statement, option 3 includes it, and option 4 rejects the true statement 2.

Q3. The Antarctic ozone hole is usually at its deepest during:

June–July
September–October
December–January
March–April

Show answer

Answer: B. September–October

It is deepest in the southern spring, September–October, when sunlight returns to the polar stratospheric clouds formed in winter and frees active chlorine. June–July is the dark winter, when there is not yet enough sunlight; December–January is summer, when the vortex has broken up; March–April is autumn, before the clouds form.

Q4. Consider the following statements:
1. The WMO and UNEP jointly set up the IPCC in 1988.
2. The UNFCCC sets legally binding emission targets for Annex I countries.
Which of the statements given above is/are correct?

1 only
2 only
Both 1 and 2
Neither 1 nor 2

Show answer

Answer: A. 1 only

Statement 1 is correct (1988). Statement 2 is wrong: the convention is a framework with only a non-binding aim; binding targets came with the Kyoto Protocol for Annex B countries. Option 2 picks the false statement, option 3 includes it, and option 4 rejects the true statement 1.

Q5. Which of the Kyoto Protocol's mechanisms allowed projects in developing countries to earn tradable credits?

Joint Implementation
International emissions trading
Clean Development Mechanism
REDD+

Show answer

Answer: C. Clean Development Mechanism

The CDM (Article 12) issued certified emission reductions for projects in developing countries. Joint Implementation works between two Annex B countries; emissions trading moves allowances among Annex B countries; REDD+ is a later UNFCCC framework of results-based forest payments, not a Kyoto mechanism.

Q6. India's target year for net zero emissions, announced at COP26 in Glasgow, is:

2047
2050
2060
2070

Show answer

Answer: D. 2070

India announced net zero by 2070. 2047 is India's Kigali deadline for an 85 per cent HFC cut; 2050 is the year many developed economies chose; 2060 is China's announced year.

Q7. Consider the following pairs:
Scheme : Law under which it rests
1. Carbon Credit Trading Scheme : Energy Conservation Act, 2001
2. Green Credit Programme : Environment (Protection) Act, 1986
3. Ozone Depleting Substances Rules, 2000 : Air (Prevention and Control of Pollution) Act, 1981
How many of the pairs given above are correctly matched?

Only one
Only two
All three
None

Show answer

Answer: B. Only two

Pairs 1 and 2 are correct. Pair 3 is wrong: the Ozone Depleting Substances (Regulation and Control) Rules, 2000 were made under the Environment (Protection) Act, 1986, not the Air Act. So 'only one' undercounts, 'all three' includes the wrong pair, and 'none' rejects two correct pairs.

Q8. Arrange the following in chronological order of adoption:
1. Kyoto Protocol
2. Montreal Protocol
3. Paris Agreement
4. UN Framework Convention on Climate Change
Select the correct answer using the code given below:

2-4-1-3
4-2-1-3
2-1-4-3
4-1-2-3

Show answer

Answer: A. 2-4-1-3

Montreal 1987, UNFCCC 1992, Kyoto 1997, Paris 2015. Option 2 puts the UNFCCC before Montreal; option 3 puts Kyoto before the convention it belongs to; option 4 places Montreal after Kyoto.

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Sources

IPCC Fifth Assessment Report (2013, global warming potentials) and Sixth Assessment Report, Working Group I (2021); NOAA Global Monitoring Laboratory, Mauna Loa carbon dioxide record (2023 annual mean) — https://www.ipcc.ch/report/ar6/wg1/
United Nations Framework Convention on Climate Change, 1992; Kyoto Protocol, 1997, and Doha Amendment, 2012; COP decisions from Bali (2007) to Warsaw (2013) — https://unfccc.int/resource/docs/convkp/conveng.pdf
Paris Agreement, 2015; India's Updated First NDC (August 2022); Energy Conservation Act, 2001, as amended in 2022, and Carbon Credit Trading Scheme, 2023; Green Credit Rules, 2023; National Action Plan on Climate Change (2008) — https://unfccc.int/sites/default/files/english_paris_agreement.pdf
Vienna Convention for the Protection of the Ozone Layer (1985); Montreal Protocol (1987) and its Kigali Amendment (2016); Ozone Depleting Substances (Regulation and Control) Rules, 2000 — https://ozone.unep.org/treaties