IPCC AR6 Report: Working Groups, 1.5°C Pathway and India Implications

The IPCC AR6 report is the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, the most comprehensive scientific stocktake of the climate system produced so far. Released in stages between August 2021 and March 2023, the AR6 cycle covered three Working Group reports, three Special Reports, a Refinement to the National Greenhouse Gas Inventory methodology, and a final Synthesis Report that distilled almost a decade of climate science for the negotiators at the United Nations Framework Convention on Climate Change. The IPCC AR6 report does not prescribe policy, but it sharpens the menu of options and the cost of inaction.

The headline conclusion of the IPCC AR6 report is blunt. Human influence has unequivocally warmed the planet by approximately 1.1 °C over pre-industrial levels (1850–1900 baseline), and current policies place the world on a path to 2.7–3.1 °C of warming by 2100. Holding warming to 1.5 °C — the more ambitious target of the Paris Agreement — now requires global greenhouse gas emissions to peak before 2025 and to be cut by 43 percent below 2019 levels by 2030.

What the IPCC Is and How It Works

The Intergovernmental Panel on Climate Change was established in 1988 by the World Meteorological Organization and the United Nations Environment Programme. It does not conduct original research. Instead, hundreds of volunteer scientists assess the published literature on the physical science, impacts and adaptation, and mitigation of climate change. Reports go through three rounds of expert and government review and are finalised line by line at a plenary attended by all 195 member governments.

The Six Assessment Cycles

The First Assessment Report (FAR, 1990) helped frame the original UNFCCC. Subsequent cycles — SAR (1995), TAR (2001), AR4 (2007), AR5 (2014) and now AR6 (2021–2023) — have refined certainty levels on attribution, sea-level projections, regional impacts and mitigation pathways. AR6 introduced new tools: a more comprehensive set of Shared Socioeconomic Pathways (SSPs), an “Atlas” of regional climate change, and a much expanded chapter on losses and damages.

Structure of the AR6 Cycle

The IPCC AR6 report is not a single volume. It is a coordinated assessment delivered by three Working Groups, complemented by Special Reports and a Synthesis Report.

Working Group I: The Physical Science Basis

Released in August 2021, the WG-I report titled Climate Change 2021: The Physical Science Basis concluded that:

• Human-caused warming is unequivocal — for the first time the IPCC used the word “unequivocal” without qualification.
• Global surface temperature was about 1.09 °C higher in 2011–2020 than in 1850–1900.
• Each of the last four decades has been successively warmer than any preceding decade since 1850.
• Many observed changes — extreme heat, marine heatwaves, heavy precipitation, agricultural and ecological droughts — are unprecedented in millennia.
• Even in a low-emission scenario (SSP1-1.9), global warming will reach 1.5 °C in the early 2030s before potentially stabilising.

Working Group II: Impacts, Adaptation and Vulnerability

Released in February 2022, Climate Change 2022: Impacts, Adaptation and Vulnerability introduced the language of “climate-resilient development” and concluded that:

• Approximately 3.3 to 3.6 billion people live in contexts highly vulnerable to climate change.
• Adverse impacts on health, food security, water supply, ecosystems and livelihoods are already widespread, with the poorest, women, children and indigenous communities bearing the highest burden.
• There is a closing window for climate-resilient development. Beyond about 1.5 °C, adaptation options become severely constrained for some ecosystems.

Working Group III: Mitigation of Climate Change

Released in April 2022, Climate Change 2022: Mitigation of Climate Change assessed the response side:

• Global net anthropogenic GHG emissions reached approximately 59 gigatonnes of CO₂-equivalent in 2019, the highest in human history.
• Emissions grew by 12 percent between 2010 and 2019 but the rate of growth slowed compared with the previous decade.
• The unit costs of solar PV, wind and lithium-ion batteries fell 85, 55 and 85 percent respectively between 2010 and 2019, reshaping the feasible mitigation menu.
• Limiting warming to 1.5 °C with no or limited overshoot implies cutting global GHG emissions by 43 percent by 2030 and reaching net-zero CO₂ around 2050.

Special Reports

The AR6 cycle produced three Special Reports:

• Global Warming of 1.5 °C (SR1.5, 2018).
• Climate Change and Land (SRCCL, 2019).
• The Ocean and Cryosphere in a Changing Climate (SROCC, 2019).

The Synthesis Report

Released on 20 March 2023, the AR6 Synthesis Report integrated the three Working Groups and Special Reports for policymakers. Its core message: “the choices and actions implemented in this decade will have impacts now and for thousands of years”.

The 1.5°C Pathway

The 1.5 °C target was politically born at COP21 in Paris (2015) and scientifically interpreted by SR1.5 in 2018. AR6 confirmed the math but tightened the deadline.

What 1.5°C Requires

• Global CO₂ emissions must fall about 48 percent below 2019 levels by 2030 and reach net zero around 2050.
• All GHG emissions must fall about 43 percent below 2019 by 2030.
• Methane, the second most important GHG, must be cut by about a third by 2030.
• Renewables must supply 60 percent or more of global electricity by 2030.
• Coal without carbon capture must phase out in OECD economies by 2030 and globally by 2040.

Carbon Budgets

The remaining carbon budget for a 50 percent chance of staying below 1.5 °C was estimated at about 500 GtCO₂ from the beginning of 2020 — a budget the world is consuming at roughly 40 GtCO₂ per year. At current rates, it will be exhausted before 2032.

Overshoot and Removal

AR6 finds that most 1.5 °C pathways now imply some overshoot — temporary breach above 1.5 °C — followed by carbon removal to bring temperatures back down. Removal technologies include afforestation, bioenergy with carbon capture and storage (BECCS), direct air capture, soil carbon, blue carbon and enhanced rock weathering. None are yet deployed at the scale assumed in modelled pathways.

India in the AR6 Report

India features prominently across all three Working Groups, both as a region facing severe physical risk and as a major emitter whose mitigation choices will shape the global trajectory.

Physical Risks for India

WG-I and the Regional Atlas project for India:

• Intensification of the South Asian summer monsoon under all scenarios, with greater interannual variability.
• A higher frequency and intensity of heatwaves, with the Indo-Gangetic plain a hotspot.
• Glacial retreat in the Hindu Kush Himalaya, with implications for the Ganga, Indus and Brahmaputra basins.
• Sea-level rise along the Bay of Bengal and Arabian Sea coasts, with mid-century projections of 25–35 cm above 1995–2014 levels under intermediate scenarios.
• Increased tropical cyclone intensity in the Arabian Sea — a trend already documented since the 2000s.

Impacts and Adaptation

WG-II identifies India among the regions most exposed to compound climate risk. Wheat and rice yields decline above certain thresholds; coastal cities such as Mumbai, Chennai, Kolkata and Visakhapatnam face flooding from sea-level rise combined with storm surge; the Sundarbans, Western Ghats and Himalayan ecosystems face transformational risk.

Mitigation Pathways

WG-III recognises India’s commitments under its updated Nationally Determined Contribution (NDC):

• Reduce GDP emissions intensity by 45 percent below 2005 levels by 2030.
• Achieve 50 percent of installed electric power capacity from non-fossil sources by 2030.
• Create an additional carbon sink of 2.5–3 GtCO₂-equivalent through forest and tree cover.
• Reach net-zero emissions by 2070 — a target announced at COP26 in Glasgow.

India’s per capita emissions remain about a third of the global average, and historical cumulative emissions are less than 4 percent of the world total — a context the AR6 report acknowledges through the framework of equity and Common but Differentiated Responsibilities and Respective Capabilities (CBDR-RC). For India’s diplomacy on these issues, see COP-28 of the UNFCCC.

Adaptation, Loss and Damage

A distinctive contribution of AR6 was its sharper treatment of adaptation and loss and damage.

Adaptation Limits

The report distinguishes between soft limits — typically financial, institutional or informational — and hard limits, where no adaptation can prevent intolerable risks. Coral reefs face hard limits around 1.5 °C; some small island states and low-lying coastal communities face hard limits beyond 2 °C.

Loss and Damage

WG-II provided the strongest scientific framing yet for losses and damages — economic and non-economic harms beyond the reach of adaptation. The framing fed directly into the establishment of the Loss and Damage Fund at COP27 (Sharm el-Sheikh, 2022) and its operationalisation at COP28 (Dubai, 2023).

Methodology Innovations in AR6

Shared Socioeconomic Pathways (SSPs)

Replacing the older RCPs, AR6 used five SSPs that combine plausible socioeconomic narratives with emissions trajectories: SSP1 (sustainability), SSP2 (middle of the road), SSP3 (regional rivalry), SSP4 (inequality) and SSP5 (fossil-fuelled development). Each is paired with a radiative forcing level — for example, SSP1-1.9 keeps warming close to 1.5 °C, while SSP5-8.5 traces a high-emission future of about 4 °C by 2100.

Confidence and Likelihood Language

AR6 retained and refined the IPCC’s calibrated language. Phrases such as “very likely” (90–100 percent probability), “high confidence” and “robust evidence with high agreement” have specific meanings designed to communicate uncertainty without dilution.

Critiques and Limitations

The IPCC AR6 report has been praised for its scientific rigour but also faces critiques:

• Equity treatment: many developing-country governments and researchers argue that historical responsibility for cumulative emissions remains under-emphasised in mitigation chapters.
• Reliance on carbon removal: most 1.5 °C pathways assume large-scale deployment of removal technologies that are not yet proven at scale.
• Underestimation of tipping points: some scientists argue AR6’s treatment of Arctic sea ice, Greenland and West Antarctic ice sheets, Amazon dieback and permafrost methane release is conservative.
• Policy translation: the Summaries for Policymakers are negotiated word by word with governments, which can soften some statements present in the underlying technical chapters.

Way Forward

The AR7 cycle, agreed in 2023, will begin reporting from around 2028. In the meantime, the IPCC AR6 report’s policy implications are clear:

• Front-load mitigation in this decade. Peak emissions before 2025 globally.
• Scale finance. Adaptation finance flows must roughly quadruple by 2030; mitigation finance must increase three- to six-fold.
• Operationalise the Loss and Damage Fund with predictable contributions.
• Embed climate risk in macroeconomic planning, sovereign debt frameworks, infrastructure standards and disaster response.
• Integrate mitigation and adaptation through climate-resilient development pathways — a phrase coined by AR6 and now central to IPCC discourse.

For India, the IPCC AR6 report is both a warning and a roadmap. The country sits at the intersection of high physical risk, low historical responsibility and high mitigation opportunity. The choices it makes on coal, renewables, agriculture, urbanisation and forest cover will determine not just its own development trajectory but also a meaningful share of the global carbon budget.

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