{
  "slug": "pacific-low-cloud-feedback-2026",
  "title": "Pacific Low-Cloud Feedback Under Warming and High CO2",
  "url": "https://solaranalytica.com/pacific-low-cloud-feedback-2026",
  "summary": "A 7,083-run Caltech-Google ensemble finds positive tropical Pacific low-cloud feedback under warming and a materially stronger shortwave response in the combined +4 K and quadrupled-CO2 state. The result strengthens mechanism evidence without producing a new global climate-sensitivity estimate.",
  "license": "Free to use with attribution to Solar Analytica (solaranalytica.com). Underlying figures are named to their public sources below.",
  "csv": "https://solaranalytica.com/reports/pacific-low-cloud-feedback-2026/data.csv",
  "datePublished": "2026-07-26",
  "lastReviewed": "2026-07-26",
  "sources": [
    {
      "title": "Chammas et al. (2026): High-resolution simulations reveal positive global warming feedback from Pacific low clouds",
      "url": "https://doi.org/10.1126/sciadv.aec8488"
    },
    {
      "title": "PubMed Central: full text and supplementary links",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC13398498/"
    },
    {
      "title": "Caltech: Low-Level Cloud Loss Amplifies Global Warming",
      "url": "https://www.caltech.edu/about/news/low-level-cloud-loss-amplifies-global-warming"
    },
    {
      "title": "IPCC AR6 Working Group I, Chapter 7: Earth energy budget, climate feedbacks and climate sensitivity",
      "url": "https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-7/"
    },
    {
      "title": "Myers et al. (2021): Observational constraints on low-cloud feedback reduce uncertainty of climate sensitivity",
      "url": "https://www.nature.com/articles/s41558-021-01039-0"
    },
    {
      "title": "Ceppi et al. (2026): Low-cloud feedback and adjustment in the 2003-2024 satellite record",
      "url": "https://acp.copernicus.org/articles/26/4153/2026/"
    },
    {
      "title": "Peng et al. (2025): Global high-resolution multiscale low-cloud response under +4 K warming",
      "url": "https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025MS005003"
    },
    {
      "title": "Schneider, Kaul and Pressel (2019): Possible climate transitions from breakup of stratocumulus decks under greenhouse warming",
      "url": "https://www.nature.com/articles/s41561-019-0310-1"
    }
  ],
  "figures": [
    {
      "id": "pacific-low-cloud-response-intervals",
      "title": "Pacific low-cloud radiative responses",
      "unit": "W m^-2 K^-1",
      "valueLabel": "Median response",
      "metricLabels": {
        "lower95": "95% CI lower",
        "upper95": "95% CI upper"
      },
      "provenance": {
        "dataSource": "Chammas et al. (2026), Science Advances",
        "dataType": "Modelled large-eddy simulation ensemble",
        "scope": "Selected tropical Pacific low-cloud states",
        "statistic": "Ensemble median",
        "interval": "95% bootstrap confidence interval where reported"
      },
      "caption": "Chammas et al. (2026). Only the warming-only row is a pure temperature-mediated feedback; the combined rows also include rapid CO2 adjustment.",
      "series": [
        {
          "label": "+4 K, baseline CO2",
          "value": 0.14,
          "lower95": 0.02,
          "upper95": 0.25,
          "responseType": "Temperature-mediated feedback"
        },
        {
          "label": "+4 K + 2x CO2",
          "value": 0.15,
          "lower95": 0.05,
          "upper95": 0.28,
          "responseType": "Total cloud-radiative response"
        },
        {
          "label": "+4 K + 4x CO2",
          "value": 0.43,
          "lower95": 0.33,
          "upper95": 0.53,
          "responseType": "Total cloud-radiative response"
        }
      ]
    },
    {
      "id": "pacific-low-cloud-radiative-components",
      "title": "Shortwave and longwave response components",
      "unit": "W m^-2 K^-1",
      "valueLabel": "Median component",
      "provenance": {
        "dataSource": "Chammas et al. (2026), Science Advances",
        "dataType": "Modelled large-eddy simulation ensemble",
        "scope": "Selected tropical Pacific low-cloud states",
        "statistic": "Ensemble median",
        "interval": "Component confidence intervals not reproduced in this figure"
      },
      "caption": "Chammas et al. (2026). Positive shortwave values dominate; negative longwave values partially offset them.",
      "series": [
        {
          "label": "+4 K: shortwave",
          "value": 0.18
        },
        {
          "label": "+4 K: longwave",
          "value": -0.03
        },
        {
          "label": "+4 K + 2x: shortwave",
          "value": 0.23
        },
        {
          "label": "+4 K + 2x: longwave",
          "value": -0.02
        },
        {
          "label": "+4 K + 4x: shortwave",
          "value": 0.49
        },
        {
          "label": "+4 K + 4x: longwave",
          "value": -0.04
        }
      ]
    },
    {
      "id": "quadrupled-co2-rapid-cloud-adjustment",
      "title": "Rapid cloud-radiative adjustment at quadrupled CO2",
      "unit": "W m^-2",
      "valueLabel": "Median adjustment",
      "metricLabels": {
        "lower95": "95% CI lower",
        "upper95": "95% CI upper"
      },
      "provenance": {
        "dataSource": "Chammas et al. (2026), Science Advances",
        "dataType": "Modelled large-eddy simulation ensemble",
        "scope": "Quadrupled CO2 with baseline sea-surface temperature; not temperature-normalised",
        "statistic": "Ensemble median",
        "interval": "95% bootstrap confidence interval where reported"
      },
      "caption": "Chammas et al. (2026). Separate from the W m^-2 K^-1 feedback rows because sea-surface temperature is held at baseline.",
      "series": [
        {
          "label": "4x CO2, baseline SST",
          "value": 1.93,
          "lower95": 1.73,
          "upper95": 2.04
        }
      ]
    }
  ]
}