LESSON 4.1 — Climate Change Fundamentals — Science, Sectors & Governance
A. Standard Map
| Topic | Governing Source | Exam Focus |
|---|---|---|
| Definition of climate change | UNFCCC Article 1 — distinction from “weather” | Definition; distinction climate vs weather |
| Greenhouse gases | CO₂, CH₄, N₂O, fluorinated gases (HFCs, PFCs, SF₆); GWP | Name, sources, GWP ranking |
| Global warming milestones | IPCC 1990, 1995, 2001, 2007, 2014, 2018 (1.5°C), 2021, 2023 reports | Reports → headline finding |
| Observed changes | Temperature, sea level, extreme events, ice cover | Trend direction + magnitudes |
| Sectoral impacts | Agriculture, water, health, coasts, cities, biodiversity | Sector → impact pathway |
| Mitigation vs adaptation | Distinction + tools under each | Definitions + examples |
| International governance | UNFCCC (1992), Kyoto (1997), Paris (2015), COP conferences | Year + key feature |
| India’s climate governance | NAPCC (2008), NDCs (2015, updated 2022), SAPCC | Policy → year → scope |
| Climate finance | Green Climate Fund, Adaptation Fund, NAMA, NDC financing | Mechanism → scope |
B. Why It’s Used
Paper II §4 of the TGPSC syllabus introduces climate change as a planning subject — not as distant environmental concern but as a near-term variable that changes water demand, building energy loads, disaster frequency, agricultural calendars, and migration patterns. The Town Planning Assistant will work on heat action plans, city climate resilience plans, transit investment justifications, and EIA-tier climate assessments — all of which require fluency in the science (what’s happening), the consequences (what changes for cities), and the governance (what India has committed to, what state-level plans require). The exam tests scientific basics (greenhouse gases, GWP, observed warming), sectoral impacts (agriculture, water, health, cities), and institutional memory (UNFCCC → Kyoto → Paris → India’s NAPCC → SAPCC).
C. Mechanism in Words
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Climate change is defined by the UNFCCC (Article 1) as “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.” Two key distinctions follow. Climate vs weather: weather is the day-to-day state of the atmosphere (temperature, rainfall, wind at a moment); climate is the long-term statistical average of weather over 30+ years. A single hot day is weather; a decade of above-average temperatures is climate. Anthropogenic vs natural: natural climate variability exists (volcanic eruptions, solar cycles, Milankovitch orbital cycles), but the UNFCCC definition focuses on change attributable to human activity — primarily fossil-fuel combustion, deforestation, and intensive agriculture that raise atmospheric greenhouse gas concentrations.
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The greenhouse effect is the physical mechanism. Solar radiation (short-wave, high-energy) passes largely through the atmosphere and warms the Earth’s surface. The Earth re-emits this energy as long-wave infrared radiation. Greenhouse gases (GHGs) in the atmosphere absorb some of this infrared and re-radiate it back toward the surface — warming the lower atmosphere. Without this natural greenhouse effect, Earth’s average surface temperature would be about −18°C instead of +15°C. The problem is the enhanced greenhouse effect: human activity since the Industrial Revolution has raised atmospheric CO₂ from ~280 ppm (pre-industrial) to ~420 ppm (2024), intensifying the effect and warming the planet by approximately 1.1–1.2°C above pre-industrial levels by the early 2020s.
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There are four major categories of greenhouse gases, ranked by Global Warming Potential (GWP). Carbon dioxide (CO₂) is the largest by volume and the reference gas (GWP = 1, by definition). It persists in the atmosphere for centuries. Major sources: fossil-fuel combustion (coal, oil, gas), cement production, deforestation. Methane (CH₄) has a GWP of approximately 28–34 over 100 years (about 84 over 20 years — short-lived but very potent). Major sources: livestock (enteric fermentation), rice paddies, landfills, natural gas leakage. Nitrous oxide (N₂O) has a GWP of approximately 265–298. Sources: synthetic fertilisers, manure management, industrial processes. Fluorinated gases (HFCs, PFCs, SF₆) are entirely human-made; some have GWPs in the thousands or tens of thousands. Sources: refrigeration, air conditioning, electronics, aluminium smelting. The Paris Agreement covers all four categories; the Kigali Amendment (2016) specifically phases down HFCs.
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The Intergovernmental Panel on Climate Change (IPCC), established in 1988 by WMO and UNEP, is the scientific authority. Its Assessment Reports (AR) synthesise the peer-reviewed science; the headlines that shape global policy come from these reports. First Assessment Report (AR1, 1990) flagged climate change as an issue; AR2 (1995) suggested “discernible human influence”; AR3 (2001) strengthened attribution; AR4 (2007) concluded warming was “unequivocal”; AR5 (2014) quantified the global carbon budget; the Special Report on 1.5°C (SR15, 2018) warned that the world had ~12 years to act to limit warming to 1.5°C and that 2°C was far more damaging than previously thought; AR6 (2021–2023) declared human influence on climate “unequivocal” and found that 1.5°C could be reached by the early 2030s under most scenarios. The phrase to remember: each IPCC report has strengthened the language of certainty from “likely” (AR1) to “unequivocal” (AR6).
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Observed changes are now measurable across multiple indicators. Global average surface temperature has risen about 1.1°C since 1880; the rate of warming since 1970 is unprecedented in at least 2,000 years. Sea level has risen about 20 cm since 1900, with the rate accelerating to ~3.7 mm/year in the 2006–2018 window. Arctic sea ice extent is declining about 13% per decade (September minimum). Glaciers are retreating in nearly every mountain region. Extreme weather — heat waves, heavy rainfall events, intense cyclones — has increased in frequency and intensity. India-specific: the Indian subcontinent has seen rising frequency of heat waves (Hyderabad, Nagpur, parts of Telangana routinely hit 45°C+ in May); erratic monsoon patterns; more intense cyclones in the Arabian Sea (previously rare); and increased frequency of urban flooding (Hyderabad’s 2020 and 2021 floods).
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Sectoral impacts propagate through multiple pathways. Agriculture — heat stress reduces yields of wheat (sensitive to night-time temperature above 25°C) and rice; changing monsoon patterns disrupt planting dates; pests expand their range. Water — glacier retreat affects Himalayan-fed rivers (Ganga, Indus, Brahmaputra) feeding hundreds of millions; rainfall intensity changes shift recharge patterns; coastal aquifers face saline intrusion from sea-level rise. Health — heat-related mortality rises; vector-borne diseases (dengue, malaria) expand their geographic range; water-borne diseases rise during floods. Coasts — sea-level rise threatens low-lying areas (Mumbai, Kolkata, Chennai, parts of coastal Andhra and Tamil Nadu); cyclone intensity compounds storm surge. Cities — urban heat island amplifies warming; extreme rainfall overwhelms drainage; energy demand for cooling spikes. Biodiversity — species ranges shift poleward or upward; coral reefs bleach (already severe in Gulf of Mannar, Lakshadweep); ecosystem services degrade.
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Mitigation and adaptation are the two response strategies — and both are necessary. Mitigation reduces the causes of climate change by cutting GHG emissions or removing CO₂ from the atmosphere (renewable energy, energy efficiency, afforestation, carbon capture and storage, modal shift in transport, dietary change). Adaptation reduces the impacts of climate change by adjusting systems to be more resilient (heat-resilient housing, drought-resistant crops, urban drainage upgrades, early warning systems, mangrove restoration for cyclone protection). The Paris Agreement (Article 2) explicitly recognises both. India’s policy framework includes both: the National Action Plan on Climate Change (NAPCC, 2008) launches eight national missions covering solar, energy efficiency, sustainable habitat, water, Himalayan, agriculture, strategic knowledge, and green India (forests). The relative weight: developed countries must do more on mitigation (historical responsibility); developing countries like India prioritise adaptation (vulnerability) while contributing to mitigation through NDCs.
D. Core Concept Explanations
C1. Greenhouse gases — ranked by GWP
| Gas | Formula | GWP (100-year) | Lifetime | Major source | ~Share of warming |
|---|---|---|---|---|---|
| Carbon dioxide | CO₂ | 1 (reference) | Centuries | Fossil fuels, cement, deforestation | ~75% |
| Methane | CH₄ | 28–34 | ~12 years | Livestock, rice, landfills, gas leaks | ~16% |
| Nitrous oxide | N₂O | 265–298 | ~120 years | Fertilisers, manure, industry | ~6% |
| Fluorinated gases (HFCs, PFCs, SF₆) | various | Up to 23,500 (SF₆) | Centuries to millennia | Refrigeration, AC, electronics, aluminium | ~2% |
Critical Distinction: Volume vs warming contribution. CO₂ has the lowest GWP per tonne but the largest total warming effect because we emit so much of it. Methane is far more potent per tonne but emitted in smaller quantities. Decarbonisation (cutting CO₂) is the long-term fix; cutting methane and HFCs buys near-term cooling.
C2. IPCC reports — landmark findings
| Report | Year | Headline finding |
|---|---|---|
| AR1 | 1990 | Climate change is a concern; science should be assessed systematically |
| AR2 | 1995 | “Discernible human influence on global climate” |
| AR3 | 2001 | Strengthens attribution; introduces shared socioeconomic pathways |
| AR4 | 2007 | Warming is “unequivocal”; shared Nobel Peace Prize with Al Gore |
| AR5 | 2014 | Quantifies the global carbon budget; 2°C ceiling needs 40–70% cuts by 2050 |
| SR15 | 2018 | Limiting to 1.5°C requires 45% cuts by 2030, net zero by 2050 |
| AR6 (WG1) | 2021 | Human influence is “unequivocal”; 1.5°C may be reached by early 2030s |
| AR6 (Synthesis) | 2023 | “Likely” to breach 1.5°C between 2030 and 2035 in many scenarios |
C3. Mitigation vs adaptation — examples
| Strategy | Examples | Tools |
|---|---|---|
| Mitigation | Renewable energy; energy efficiency; afforestation; modal shift to transit; carbon pricing; CCS; reduction of methane leaks | NDC targets, carbon taxes, cap-and-trade, renewable mandates |
| Adaptation | Heat-resilient housing; urban drainage upgrades; drought-resistant crops; cyclone shelters; mangrove restoration; early warning systems; cool roofs | NAP (National Adaptation Plans); heat action plans; resilient infrastructure codes |
C4. India’s climate governance — the eight NAPCC missions
| Mission | Year | Focus |
|---|---|---|
| National Solar Mission | 2010 (revised upward) | 100 GW → 280 GW solar target by 2030 |
| National Mission for Enhanced Energy Efficiency | 2010 | PAT scheme, standards, labels |
| National Mission on Sustainable Habitat | 2010 | Urban planning, building codes, transport, waste |
| National Water Mission | 2011 | 20% improvement in water use efficiency |
| National Mission for Sustaining the Himalayan Ecosystem | 2010 | Himalayan research and monitoring |
| National Mission for a Green India | 2014 | 10 m ha afforestation; forest cover improvement |
| National Mission for Sustainable Agriculture | 2010 | Climate-resilient agriculture |
| National Mission on Strategic Knowledge for Climate Change | 2010 | Research, capacity building |
Each mission has a state-level counterpart — the State Action Plan on Climate Change (SAPCC). Telangana’s SAPCC covers water, agriculture, forests, biodiversity, energy, habitat, health, and disaster management, and is the operative document for state planners.
C5. India’s NDCs (Nationally Determined Contributions)
| Target | Original NDC (2015) | Updated NDC (2022) |
|---|---|---|
| Emissions intensity reduction (vs 2005) | 33–35% by 2030 | 45% by 2030 |
| Non-fossil installed electricity capacity | 40% by 2030 | 50% by 2030 |
| Additional carbon sink (forests) | 2.5–3.0 billion tonnes CO₂ equivalent by 2030 | Same |
| Renewable energy target | 175 GW by 2022 | 500 GW by 2030 (announced at COP26) |
| Net-zero target | None | 2070 (announced at COP26, Glasgow) |
E. Worked Numericals and Parameter Tables
E1. Carbon-equivalent emissions — worked
A factory emits 1,000 tonnes of CO₂ and 10 tonnes of methane in a year. Using GWP (100-year): methane = 28.
- CO₂-equivalent emissions = (1,000 × 1) + (10 × 28) = 1,000 + 280 = 1,280 tonnes CO₂-equivalent (CO₂e)
Methane, despite being only 1% of the mass, contributes 22% of the warming effect. This is why cutting methane is high-leverage in the near term.
E2. Sea-level rise — worked
A coastal city has a sea-level rise of 3.5 mm/year. Projected rise by 2100 (from 2024 baseline) = (3.5 mm × 76 years) = 266 mm ≈ 27 cm. With accelerating rates (most models project 4–8 mm/year by 2050), the figure could be 50–80 cm by 2100. Planners in low-lying coastal cities (Mumbai, Chennai, Kolkata) must account for this in road levels, drainage outfalls, and building plinth heights.
E3. Energy transition arithmetic
A state has 10 GW of installed capacity, of which 4 GW is coal and 6 GW is solar + wind. To reach 50% non-fossil target, the current state already meets it (60% non-fossil). But if the state grows to 20 GW by 2030 and only adds 6 GW of new coal, non-fossil share = (6 solar + 0 new RE) / 20 = 30% → falls below target. Planning must add new renewable capacity proportional to total growth.
E4. Heat-action arithmetic
A city’s heat action plan aims to reduce heat-related mortality by 50%. Baseline mortality is 200 deaths/year during heat waves. Target = 100 deaths/year. If cool-roof installation in informal housing reduces indoor temperature by 3°C and prevents 30% of deaths in those households, the plan must combine cool roofs + early warning + drinking water kiosks + shaded bus stops to reach the 50% reduction.
F. Design Criteria
| Parameter | Standard / Typical value | Source |
|---|---|---|
| Pre-industrial CO₂ concentration | ~280 ppm | Ice core data |
| Current CO₂ concentration (2024) | ~420 ppm | Mauna Loa Observatory |
| Global average warming (2020s vs pre-industrial) | ~1.1–1.2°C | IPCC AR6 |
| Paris Agreement target | Limit warming to well below 2°C; pursue 1.5°C | UNFCCC COP21, 2015 |
| India NDC emissions intensity target | 45% reduction by 2030 (vs 2005) | Updated NDC, 2022 |
| India NDC non-fossil capacity target | 50% by 2030 | Updated NDC, 2022 |
| India renewable energy target | 500 GW by 2030 | COP26 announcement |
| India net-zero target | 2070 | COP26 announcement |
| Sea-level rise (1900–2020) | ~20 cm | IPCC AR6 |
| IPCC GWP for methane (100-year) | 28–34 | IPCC AR5/AR6 |
G. Application Zones
- Heat action plans — Ahmedabad’s heat action plan (first in India, 2013) has been a model; Hyderabad and other Telangana cities have versions. Cool roofs, drinking water, public cooling centres, early warning.
- Coastal zone planning — sea-level rise feeds into CRZ regulations (Lesson 4.2), building plinths, and mangrove conservation.
- Sustainable habitat missions — the NAPCC Mission on Sustainable Habitat translates into ECBC (Energy Conservation Building Code), transit-oriented development, and waste-to-resource systems.
- Telangana SAPCC — state planners implement SAPCC priorities: water conservation (Mission Bhagiratha, Mission Kakatiya), renewable energy (Telangana’s solar push), agriculture resilience.
- Climate finance — Green Climate Fund projects, Adaptation Fund, World Bank resilience financing flow through state planning departments.
H. Common Confusions
| Confusion | Reality |
|---|---|
| “Weather and climate are the same thing.” | No — weather is short-term (days); climate is the 30-year statistical average. |
| “CO₂ is the most potent greenhouse gas.” | No — CO₂ has GWP 1; methane is 28–34× more potent; SF₆ is 23,500× more potent. CO₂ dominates total warming due to volume, not potency. |
| “The IPCC conducts original climate research.” | No — IPCC assesses and synthesises existing peer-reviewed science. It does not run models itself. |
| “Paris Agreement sets binding emission cuts for India.” | No — NDCs are voluntary, nationally determined. India’s targets are self-set. |
| “India’s net-zero target is 2050.” | No — 2070 (announced at COP26). The 2050 target is for developed countries. |
| “Adaptation and mitigation are alternatives.” | No — both are needed; the debate is about relative emphasis and who pays for each. |
| “1.5°C of warming is harmless.” | No — IPCC SR15 found that 1.5°C of warming (vs pre-industrial) is already associated with severe impacts; 2°C is significantly worse. Every fraction of a degree matters. |
| “Methane’s lifetime is centuries.” | No — methane’s atmospheric lifetime is about 12 years; it is short-lived but potent. |
I. Compare & Contrast
I1. Kyoto Protocol vs Paris Agreement
| Dimension | Kyoto Protocol (1997) | Paris Agreement (2015) |
|---|---|---|
| Approach | Top-down; binding emission cuts on Annex I (developed) countries only | Bottom-up; all countries submit NDCs (nationally determined contributions) |
| Coverage | ~25% of global emissions (developed countries only) | ~97% of global emissions (all countries) |
| Legal character | Binding under international law | Hybrid — binding procedural commitments, voluntary targets |
| US participation | Signed but never ratified (Clinton → Bush) | Signed by US, withdrawn by Trump (2020), re-joined under Biden (2021) |
| Outcome | Limited; emissions grew globally | NDCs updated every 5 years (ratchet mechanism) |
I2. Mitigation vs Adaptation
| Dimension | Mitigation | Adaptation |
|---|---|---|
| Goal | Reduce causes | Reduce impacts |
| Timescale | Long-term benefit | Near-term benefit |
| Required by | Everyone; especially high emitters | Especially vulnerable countries |
| Tools | Renewables, efficiency, CCS, afforestation, carbon pricing | Heat plans, drainage, drought-resistant crops, cyclone shelters |
| India’s emphasis | Significant (NDCs) but secondary to development | High (vulnerability) — Mission on Sustainable Habitat, SAPCC |
J. Memory Hooks
- “CO₂-Methane-N₂O-Fluorinated” — the four GHG categories, ranked by GWP.
- “280 → 420 ppm” — pre-industrial vs current CO₂.
- “1.1–1.2°C” — current warming above pre-industrial.
- “Well below 2°C; pursue 1.5°C” — Paris Agreement in one phrase.
- “45-50-500-2070” — India’s updated NDC: 45% intensity cut, 50% non-fossil, 500 GW renewable, net-zero by 2070.
- “UNFCCC 1992, Kyoto 1997, Paris 2015” — the three pillars of international climate governance.
- “NAPCC = 8 missions” — Solar, Energy Efficiency, Sustainable Habitat, Water, Himalayan, Green India, Sustainable Agriculture, Strategic Knowledge.
- “AR6 = unequivocal” — the headline word from the 2021 IPCC report.
K. Revision Ladder
| Order | Item | Time |
|---|---|---|
| 1 | Memorise UNFCCC definition of climate change | 15 min |
| 2 | Memorise the four GHG categories with GWP values | 30 min |
| 3 | Memorise the IPCC report sequence with one headline per report | 30 min |
| 4 | Memorise observed changes (warming, sea level, ice, extremes) | 30 min |
| 5 | Memorise sectoral impacts (agriculture, water, health, coasts, cities, biodiversity) | 45 min |
| 6 | Memorise Kyoto vs Paris table | 20 min |
| 7 | Memorise India’s NAPCC 8 missions | 30 min |
| 8 | Memorise India’s updated NDC targets (45-50-500-2070) | 15 min |
| 9 | Practise the carbon-equivalent and warming arithmetic | 30 min |
| 10 | Map Telangana SAPCC priorities | 30 min |
L. Exam Traps
| Trap | Correct response |
|---|---|
| Question states climate and weather are the same. | False — climate is 30-year statistical average; weather is day-to-day. |
| Question lists CO₂ as the most potent GHG. | False — fluorinated gases and methane are more potent per tonne; CO₂ dominates by volume. |
| Question attributes Kyoto Protocol to 2015. | False — Kyoto is 1997; Paris is 2015. |
| Question states India’s net-zero target is 2050. | False — 2070. |
| Question lists “discernible human influence” as AR1’s finding. | False — that was AR2 (1995). AR1 (1990) was more cautious. |
| Question asks the GWP of methane (100-year). | 28–34 (per IPCC AR5/AR6). |
| Question asks India’s emissions intensity target for 2030. | 45% (updated NDC, 2022). |
| Question asks the IPCC report that declared human influence “unequivocal.” | AR6 (2021). |
M. Answer-Writing Cues
- For definition questions, cite the source: “Per UNFCCC Article 1, climate change is defined as…”
- For GHG questions, give gas + formula + GWP + source.
- For policy questions, give year + scope: “Per the Paris Agreement (2015), Article 2 commits parties to limit warming to well below 2°C…”
- For India’s commitments, always give the updated NDC (2022), not the 2015 numbers — they have been revised upward.
- For sectoral impacts, structure as: sector → exposure → sensitivity → adaptive capacity (the IPCC vulnerability framework).
N. PYQ Integration
Pattern questions only:
Pattern question 1 — Definition
Q. As per UNFCCC Article 1, “climate change” is defined as change attributed directly or indirectly to:
– (A) Solar cycles only
– (B) Volcanic eruptions
– (C) Human activity altering the composition of the global atmosphere ✓
– (D) Natural climate variability alone
Ans: (C). The UNFCCC definition focuses on anthropogenic change.
Pattern question 2 — GHG GWP
Q. Which of the following greenhouse gases has the highest Global Warming Potential over a 100-year time horizon?
– (A) Carbon dioxide
– (B) Methane
– (C) Nitrous oxide
– (D) Sulphur hexafluoride (SF₆) ✓
Ans: (D). SF₆ has a GWP of approximately 23,500. (The question excludes even more potent fluorinated gases; among standard options, SF₆ is highest.)
Pattern question 3 — India’s NDC
Q. India’s updated Nationally Determined Contribution (2022) commits to reduce emissions intensity of GDP by what percentage by 2030 (from 2005 levels)?
– (A) 20–25%
– (B) 33–35%
– (C) 45% ✓
– (D) 60%
Ans: (C). The original 2015 NDC was 33–35%; the 2022 update raised it to 45%.
Pattern question 4 — Net-zero
Q. India announced its target to achieve net-zero emissions by the year:
– (A) 2050
– (B) 2060
– (C) 2070 ✓
– (D) 2080
Ans: (C). Announced by PM Modi at COP26 in Glasgow (2021).
Pattern question 5 — Numerical
A factory emits 2,000 tonnes of CO₂ and 5 tonnes of methane in a year. Using GWP of 28 for methane, the total CO₂-equivalent emissions are:
– (A) 2,000 tonnes
– (B) 2,140 tonnes ✓
– (C) 2,500 tonnes
– (D) 2,800 tonnes
Ans: (B). 2,000 + (5 × 28) = 2,000 + 140 = 2,140 tonnes CO₂e.
O. Mini-Check — Lesson 4.1
- Define climate change per UNFCCC Article 1.
- State the difference between climate and weather.
- Name the four greenhouse gas categories and rank by GWP.
- What was the atmospheric CO₂ concentration pre-industrial and currently?
- State the Paris Agreement temperature target in one phrase.
- List the eight missions of the NAPCC.
- State India’s four headline NDC commitments (45-50-500-2070).
- Distinguish mitigation from adaptation with one example each.
- Which IPCC report declared human influence “unequivocal,” and in what year?
- Compute: 5,000 tonnes CO₂ + 10 tonnes methane × GWP 28 = ?
Answers:
1. A change of climate attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability.
2. Weather is day-to-day; climate is the 30-year statistical average.
3. CO₂ (GWP 1) < Methane (28–34) < N₂O (265–298) < Fluorinated gases (up to 23,500 for SF₆).
4. ~280 ppm pre-industrial; ~420 ppm currently (2024).
5. “Limit warming to well below 2°C above pre-industrial, and pursue efforts to limit to 1.5°C.”
6. Solar; Enhanced Energy Efficiency; Sustainable Habitat; Water; Sustaining Himalayan Ecosystem; Green India; Sustainable Agriculture; Strategic Knowledge for Climate Change.
7. 45% emissions intensity cut by 2030; 50% non-fossil capacity by 2030; 500 GW renewable by 2030; net-zero by 2070.
8. Mitigation reduces causes (e.g. renewable energy); adaptation reduces impacts (e.g. heat-resilient housing, cyclone shelters).
9. AR6 (2021) declared human influence “unequivocal.”
10. 5,000 + (10 × 28) = 5,280 tonnes CO₂e.
Next: Lesson 4.2 — Eco-Sensitive Zones & Bioclimatic Planning.