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Climate sets the terms for the other systems

Part I describes systems and their couplings. It ranks no country or operator and assesses no authority.

6 min read2 figures1 table13 notesNR-SECTOR-CLIMATE-GLOBAL-2026-BASELINE

Contents
  1. ·Edition home
  2. ·Executive summary
  3. 1Climate sets the terms for the other systems
    1. 1.1 The questions this part answers
    2. 1.2 The argument
    3. 1.3 Twenty couplings between five systems
  4. 2Key findings
  5. 3Systems and sectors at baseline
  6. 4Risks and capability
  7. 5A strong El Niño on a 1.5 °C background
  8. 6Readings from the other desks
  9. 7The 2027 agenda
  10. 8Systems in depth
  11. AMethodology
  12. BData appendix
  13. CReferences and record
  14. ·Complete edition, for print

1.1The questions this part answers

Key questions

  • Where is climate risk concentrated?
  • Which couplings carry climate shocks into other systems?
  • Which climate capabilities hold under compound stress?
  • What must 2027 evidence measure first?

In this part

  • Narrative
  • Headline finding
  • Lead figure
  • Five coupling chapters
  • Twelve-domain reading
  • Sector screens
  • Dependency matrix
  • Risk objects
  • Capability ladder
  • Scenario
  • Three lenses
  • Portfolio

1.2The argument

Climate is usually reported as a temperature: one number for each year. The 2026 evidence reads it as the condition under which water, food, health, nature and the economy operate. A warmer ocean changes rainfall, a warmer atmosphere changes heat exposure, and both change what a harvest, a river or a clinic can bear22426.

The warming is large and still rising. 2025 was 1.47 °C above the pre-industrial level in ERA5, the three years 2023 to 2025 averaged 1.52 °C, and human-induced warming reached 1.37 °C at 0.27 °C a decade17. Atmospheric carbon dioxide, methane and nitrous oxide are at record levels31.

The budget is nearly spent. For a 50% chance of staying below 1.5 °C, 170 GtCO2 remain in the Global Carbon Budget and 130 GtCO2 in the Indicators of Global Climate Change, three to four years of emissions at the 2025 level67. Most of the excess heat, more than 91%, sits in the ocean2.

Impacts are concentrated and compounding. 2025 was one of the driest years for rivers in more than three decades, modelled heat deaths across European cities have risen with warming, and 645 million people faced hunger242326. A strong El Niño is now developing on top of this background48.

Figure 1.1Where does the excess heat go? Share of the extra energy held by the climate system (%)

The surface temperature that people feel is about 1% of the excess energy. The ocean holds more than 91%, which buffers land temperatures now and commits the ocean to warming and sea-level rise for centuries2.

ItemBar, scaled to the largest valueValue
Ocean91
Land5
Ice melt and warming3
Atmosphere1

Source: as cited in the note to this figure. Year 2025.

Figure ID FIG-SECTOR-CLIMATE-GLOBAL-2026-BASELINE-01-003

11cm

sea level above the 1993 start of the satellite record, 20252

11.0 to 12.2ZJ a year

ocean heating rate, 2005 to 20252

29%

of human CO2 absorbed by the ocean, 2015 to 20242

90%

of ocean surface with a marine heatwave in 20252

1.3Twenty couplings between five systems

The climate-centred matrix types the twenty couplings between the five core systems, read for their climate content. Strengths are Nexus estimates (ESTIMATED) from the cited evidence and analogue events; they set the graph that 2027 evidence will test.

Figure 1.2Couplings between the five systems

Each line is one coupling from one system to another, drawn by the strength the edition assigns. Strengths are Nexus estimates from the cited evidence and analogue events.

  • Strong
  • Moderate
  • Weak

Source: this edition’s coupling matrix (Table 1.1); status Estimated.

Table 1.1Coupling matrix: from the row system to the column system
From, toWATENEFOOHLTBIO
WAT Water·MODERATE
hydropower and cooling in dry years		STRONG
rain-fed and irrigated crops		STRONG
floods, scarcity and water-borne disease		STRONG
river flow and wetlands
ENE EnergyMODERATE
pumping and treatment		·MODERATE
cold chains and pumping		STRONG
cooling and clinic power in heat		MODERATE
mining and land use
FOO FoodMODERATE
withdrawals		WEAK
bioenergy		·STRONG
hunger and nutrition		MODERATE
land conversion
HLT HealthWEAK
workforce		WEAK
workforce		WEAK
labour		·WEAK
residues
BIO BiodiversityMODERATE
catchments		WEAK
biomass		MODERATE
pollination and soils		WEAK
zoonoses		·
Strength: strong, moderate or weak; a Nexus estimate (status Estimated) from cited evidence and analogue events. The scale is defined in Annex A.

Transmission paths

  1. 01

    CLI → WAT → FOO

    River deficits and heat cut crop and pasture output.

    Inferred 2025 river deficits24; strong El Niño 202648

  2. 02

    CLI → HLT

    Heat waves raise deaths among older people and outdoor workers.

    Reported Europe 2022 and 2000 to 20252223

  3. 03

    CLI → INF → FIN

    Storms and fires destroy assets and strain public budgets.

    Reported Jamaica and Los Angeles 20253

  4. 04

    CLI → BIO

    Ocean heat and acidification push reefs past thresholds.

    Reported reefs at 1.4 °C16; acidification19

  5. 05

    CLI → FOO → HLT

    Weather extremes raise food insecurity and malnutrition.

    Inferred hunger projections omit El Niño26; extremes and food3

Notes

Numbers are the edition’s reference numbers, so a note reads the same in every chapter. The full list, with every source and its licence, is in Annex C. Annex C, references

  1. 2WMO (ed.), State of the Global Climate 2025 (publication page and press release of 23 March 2026). World Meteorological Organization, Geneva. Observation year 2025. Opened: page and press release; the full report was not opened. Accessed 2026-11-03.back
  2. 24WMO (ed.), State of Global Water Resources 2025 (publication page, 17 September 2026). World Meteorological Organization, Geneva. Observation year 2025. Opened: publication page with key messages; the full report was not opened. Accessed 2026-11-03.back
  3. 26FAO, IFAD, UNICEF, WFP and WHO (eds.), The State of Food Security and Nutrition in the World 2026, joint news release of 21 July 2026 (as published by WHO). Rome. Observation year 2025. Opened: news release; the report was not opened. Accessed 2026-11-03.back
  4. 1Copernicus Climate Change Service (C3S), ECMWF (ed.), Global Climate Highlights 2025 (published 14 January 2026, updated 28 January 2026). ECMWF, Bonn. DOI 10.24381/b3nm-p354. Observation year 2025. Opened in full (PDF). Accessed 2026-11-03. doi:10.24381/b3nm-p354back
  5. 7Forster, P.M. et al., Indicators of Global Climate Change 2025: annual update of key indicators of the state of the climate system and human influence, Earth System Science Data 18, 3889 to 3933, 2026. DOI 10.5194/essd-18-3889-2026. Observation year 2025. Opened in full (PDF). Accessed 2026-11-03. doi:10.5194/essd-18-3889-2026back
  6. 31WMO (ed.), Greenhouse Gas Bulletin No. 21 (16 October 2025). World Meteorological Organization, Geneva. Observation year 2024. Opened: publication page and bulletin summary with the headline values (CO2 423.9 ppm, CH4 1942 ppb, N2O 338.0 ppb). Accessed 2026-11-03.back
  7. 6Friedlingstein, P. et al., Global Carbon Budget 2025, Earth System Science Data 18, 3211 to 3288, 2026. Global Carbon Project. DOI 10.5194/essd-18-3211-2026. Observation year 2024 (2025 preliminary). Opened in full (PDF). Accessed 2026-11-03. doi:10.5194/essd-18-3211-2026back
  8. 23Barnes, G. et al., Heat-related urban mortality attributable to human-induced climate change in Europe from 2000 to 2025, Nature Health 4, 2026. Observation year 2025. Opened: abstract through PubMed and Europe PMC. A preprint version of the study reports different totals (463,730 deaths; 45% to 64%) and is not used. Accessed 2026-11-03.back
  9. 48NOAA Climate Prediction Center, ENSO diagnostic discussion of 10 September 2026. National Weather Service, College Park. Observation year 2026. Opened: discussion page. Accessed 2026-11-03.back
  10. 22Ballester, J. et al., Heat-related mortality in Europe during the summer of 2022, Nature Medicine 29, 2023. DOI 10.1038/s41591-023-02419-z. Observation year 2022. Opened: abstract through Europe PMC. Accessed 2026-11-03. doi:10.1038/s41591-023-02419-zback
  11. 3WMO (ed.), State of the Global Climate 2025, supplement on extreme events and impacts (May 2026). World Meteorological Organization, Geneva. Observation year 2025. Opened in full (PDF). Accessed 2026-11-03.back
  12. 16Global Tipping Points Report 2025 (160 authors, University of Exeter), key messages. Global Tipping Points project, Exeter. Observation year 2025. Opened: project page with key messages; the full report was not opened. Accessed 2026-11-03.back
  13. 19Findlay, H.S. et al., Ocean Acidification: Another Planetary Boundary Crossed, Global Change Biology, June 2025. DOI 10.1111/gcb.70238. Observation year 2020. Opened: abstract through Crossref and Europe PMC. Accessed 2026-11-03. doi:10.1111/gcb.70238back

Cite this chapter

Valadbaygi, S. (Ed.). (2026). Chapter 1: Climate sets the terms for the other systems. In Global Climate Risk and Resilience Report 2026: Baseline Edition, The State of the World’s Climate and Earth System. (Baseline Edition 2026, Report No. NR-SECTOR-CLIMATE-GLOBAL-2026-BASELINE) [Draft under review]. The Global Centre for Risk and Innovation (GCRI).

Every citation form of the whole report, BibTeX and RIS included, is on the edition home. Cite this report

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