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    Climate tipping points: coral reefs, AMOC, ice sheets and the Amazon

    A tipping point is a threshold beyond which part of the Earth system shifts abruptly and often irreversibly; the IPCC says such changes cannot be ruled out.[1] The Global Tipping Points Report 2025 concluded that warm-water coral reefs are already passing theirs, and put the Atlantic overturning circulation and the Amazon at risk below 2 °C of warming.[2][3][4]

    Editor reviewedUpdated ExplainerClimate science and carbon removal, Energy and climate, Science

    What a tipping point is

    Most climate change is gradual: a bit more warming brings a bit more impact. A tipping point is different. It is a threshold where a system, such as an ice sheet or a forest, starts changing on its own and may not come back even if temperatures later fall. The IPCC says abrupt changes like this, including much faster Antarctic ice melt and forest dieback, cannot be ruled out.[1]

    Tipping elements are subsystems with strong internal feedbacks, so that past a critical forcing level the change becomes self-sustaining. In AR6 the IPCC treated them as low-likelihood, high-impact outcomes, stating with high confidence that abrupt responses and tipping points, such as strongly increased Antarctic ice-sheet melt and forest dieback, cannot be ruled out.[1] The Global Tipping Points Report, a non-IPCC synthesis led by the University of Exeter with about 160 authors from 87 institutions, assesses thresholds for individual elements.[5]

    Coral reefs: the first threshold passed

    The 2025 Global Tipping Points Report concluded that warm-water coral reefs are passing their thermal tipping point, with a central threshold estimate of 1.2 °C and a range of 1–1.5 °C.[2] Current warming is above that central estimate: human-induced warming reached 1.37 °C in 2025.[6] WMO separately reported that ocean heat content reached a record in 2025.[7]

    The heat continued into 2026. Copernicus found sea surface temperatures outside the polar regions set a record for August 2026, tying the highest for any month.[8] NOAA reported a record global ocean surface temperature departure for the fourth month running in September, with persistent El Niño conditions driving record warmth across the central and eastern tropical Pacific.[9] Single months are not the same as the long-term warming level, which the indicators study put at 1.37 °C for 2025, rising about 0.27 °C per decade.[6]

    The Atlantic overturning circulation (AMOC)

    The AMOC carries warm water north in the Atlantic. The IPCC assessed that it is very likely to weaken over the 21st century in all emissions scenarios.[10] The 2025 tipping points report went further, judging it at risk of collapse below 2 °C of warming.[3] The two judgements come from different processes four years apart: a government-approved IPCC assessment in 2021 and an independent scientific synthesis in 2025.[10][5]

    Ice sheets and the Amazon

    The report warned that parts of the polar ice sheets may already have crossed tipping points that would eventually commit the world to several metres of sea-level rise, and that the Amazon rainforest is at risk below 2 °C from climate change combined with deforestation.[4] The IPCC flagged ice-sheet processes as a deep uncertainty that cannot be ruled out.[1]

    Positive tipping points

    The same report argued that “positive” tipping points, where clean technologies become self-reinforcing, have been crossed for solar PV and wind power globally.[11]

    Why it matters for carbon removal

    If warming overshoots a threshold, bringing temperatures back down requires net removal of CO2. All scenarios that reach net zero and halt warming already rely on carbon dioxide removal at gigatonne scale.[12] Whether removal can reverse tipping-point damage is an open question; see direct-air-capture and the carbon removal debate.

    Planned removal also falls short of what scenarios use. The State of CDR report found that country pledges add up to about 2.5 billion tonnes of removal a year in 2030, against 2.9 billion in the highest-ambition Paris-compatible scenarios. The gap widens to 1.2 billion tonnes in 2035 and 5.2 billion in 2050.[13] Today’s novel methods, such as enhanced-rock-weathering and ocean-carbon-dioxide-removal, removed about 2 million tonnes in 2025.[14]

    Next in the crash course

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    Questions readers ask

    Has any climate tipping point been crossed?

    The Global Tipping Points Report 2025 concluded that warm-water coral reefs are passing their thermal tipping point, with a central threshold estimate of 1.2 °C.[2]

    Will the Gulf Stream system collapse?

    The IPCC found the Atlantic Meridional Overturning Circulation is very likely to weaken this century, and the 2025 tipping points report put it at risk of collapse below 2 °C. Timing and likelihood remain uncertain.[10][3]

    Does the IPCC agree that tipping points are a risk?

    Yes. The IPCC states with high confidence that abrupt responses and tipping points, such as strongly increased Antarctic ice-sheet melt and forest dieback, cannot be ruled out.[1]

    Are there positive tipping points?

    The 2025 report argued that positive tipping points have already been crossed in solar PV and wind power globally.[11]

    Are oceans still breaking heat records in 2026?

    Yes. NOAA found the global ocean surface temperature departure set a record for the fourth month running in September 2026, with El Niño conditions adding to the warmth.[9]

    Sources

    · 14 claims from 8 publishers

    Each numbered claim is a statement we checked against the sources listed with it. Tap a number in the text to see its sources in place.

    1. [1]

      The IPCC states with high confidence that abrupt responses and tipping points, such as strongly increased Antarctic ice-sheet melt and forest dieback, cannot be ruled out. confirmedas of 2021-08-09

    2. [2]

      The Global Tipping Points Report 2025 concluded that warm-water coral reefs are passing their thermal tipping point, with a central threshold estimate of 1.2 °C (range 1–1.5 °C), making it the first Earth system tipping point reached. reportedas of 2025-10-10· interpretation

    3. [3]

      The Global Tipping Points Report 2025 assessed the Atlantic Meridional Overturning Circulation as at risk of collapse below 2 °C of warming. reportedas of 2025-10-10· interpretation

    4. [4]

      The report warned that parts of the polar ice sheets may already have crossed tipping points that would commit the world to several metres of sea-level rise, and that the Amazon rainforest is at risk below 2 °C from climate change and deforestation combined. reportedas of 2025-10-10· interpretation

    5. [5]

      The Global Tipping Points Report 2025, led by the University of Exeter's Global Systems Institute, involved about 160 authors from 87 institutions in 23 countries. confirmedas of 2025-10-10

    6. [6]

      The Indicators of Global Climate Change 2025 study estimated human-induced warming at 1.37 °C above 1850–1900 in 2025, rising at about 0.27 °C per decade over 2016–2025. confirmedas of 2026-06-11

    7. [7]

      Ocean heat content in the upper 2,000 metres reached its highest level since records began in 1960, according to WMO. confirmedas of 2026-03-23

    8. [8]

      Copernicus found that sea surface temperature over the extra-polar oceans set a record for August 2026 and was the joint-highest for any month. confirmedas of 2026-08-31

    9. [9]

      NOAA found the global ocean surface temperature departure set a record for a fourth consecutive month in September 2026, the highest for any month on record, with persistent El Niño conditions driving record warmth in the central and eastern tropical Pacific. confirmedas of 2026-10-09

    10. [10]

      The IPCC assessed that the Atlantic Meridional Overturning Circulation is very likely to weaken over the 21st century in all emissions scenarios. confirmedas of 2021-08-09

    11. [11]

      The report also identified "positive tipping points" already crossed in solar PV and wind power globally. reportedas of 2025-10-10· interpretation

    12. [12]

      All scenarios that reach net zero and halt warming deploy CDR at gigatonne scale, while in cost-effective Paris-compatible scenarios emissions cuts provide at least 80% of the effort to reach net zero CO2. confirmedas of 2026-06-01

    13. [13]

      Country pledges add up to about 2.5 billion tonnes of CO2 removal a year in 2030 against 2.9 billion in the highest-ambition Paris-compatible scenarios, a gap that grows to 1.2 billion tonnes in 2035 and 5.2 billion in 2050. confirmedas of 2026-06-01

    14. [14]

      Removal from novel methods grew from 1.4 million tonnes of CO2 in 2023 to 2.0 million tonnes in 2025. confirmedas of 2026-06-01

    Revision history (2)
    1. Page created.
    2. Refresh: added 2026 record ocean temperatures as context for the coral threshold, and the gap between national carbon removal plans and Paris-compatible scenarios.

    Created Oct 10, 2026. Last reviewed by an editor on Oct 10, 2026. Next scheduled review: Jan 10, 2027.

    Cite this page

    "Climate tipping points: coral reefs, AMOC, ice sheets and the Amazon." ContentLora, updated Oct 10, 2026. https://contentlora.com/explain/climate-tipping-points

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