SCIENCE · INVESTIGATE AND EXPLAIN

Compare observed warming with forcing counterfactuals

Inspect archived human-plus-natural and natural-only simulations alongside compatible observations.

Learning outcome: Calculate descriptive residuals and interpret long-term comparisons without treating ensemble bands as a standalone attribution test.

Starting recap

All three traces use 1850–1900 as reference. Highlighting a year does not refit the archived series.

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Try

In 2019, observed 1.226°C minus the all-forcing mean 1.18995°C is about +0.03605°C.

Open the experiment

Predict

Will an early-year comparison separate the two forcing histories as clearly as a recent one?

Your prediction and reason

Experiment

Compare 1950, 2000 and 2019 while retaining the full timeline, then inspect the missing model values in 2020.

Compare archived attribution evidence

Published attribution evidence · archived model comparisons and assessments · Frozen attribution-v1: IPCC AR6 SPM.1 annual observations and archived CMIP6 comparisons, plus SPM.2 assessed 2010–2019 contributions. All use 1850–1900 as reference, but annual values and a decade are distinct. Simulation bands are ensemble 5th–95th percentiles; assessment ranges retain their own likely/very-likely labels. No models are trained, fitted or rerun here.

Highlighted annual year: 2019 Assessed driver to inspect: Total human influence

Reset keeps your prediction, captures and practice history.

This investigation interprets published evidence for human influence on warming. The archived natural-only comparison differs from simulations including human and natural influences. The IPCC assessment attributes the observed warming over its assessed period to human influence; the viewer helps inspect that evidence but does not perform a new attribution study.

Annual comparison at 2019 (°C relative to 1850–1900)
Evidence	Value / ensemble mean	5th percentile	95th percentile	Observed − mean
Observed annual change	1.226	Not supplied here	Not supplied here	Not a model comparison
Human + natural simulations	1.190	0.738	1.871	0.036
Natural-only simulations	0.049	-0.136	0.307	1.177

The residual subtracts the archived ensemble mean from the observed annual estimate. It is not an attributed human contribution, a forecast error score or a significance test. Individual years can depart from ensemble means because variability is not synchronized. Inside or outside a model band is not, by itself, a complete causal test. The observational series has no uncertainty column in this file; that does not mean it is perfectly known.

Total human influence: Total human influence is an aggregate assessed contribution. Do not add it again to its greenhouse-gas and other-human component categories.

Published centers and ranges for the assessed 2010–2019 decade
Quantity	Center °C	Lower °C	Upper °C	Range label
Observed warming (observations)	1.06	0.88	1.21	Very likely
Total human influence	1.07	0.80	1.30	Likely
Well-mixed greenhouse gases	1.50	1.00	2.00	Likely
Other human drivers	-0.40	-0.80	0.00	Likely
Solar and volcanic drivers	0.00	-0.10	0.10	Likely
Internal variability	0.00	-0.20	0.20	Likely

Total human influence is an aggregate, so adding it to its component categories double-counts. Rounded component centers need not reproduce the independently assessed total exactly; adding lower and upper endpoints does not produce a valid combined uncertainty range. The source does not supply a joint distribution for that operation. A zero center for natural influences or internal variability does not imply zero effects in every year.

The annual panel and decade panel address different time averages. Neither should be subtracted directly from the earlier NASA series, which uses a 1951–1980 reference. That frozen NASA record starts in 1880 and cannot reconstruct the entire 1850–1900 reference. This historical assessment is not a latest-year estimate. These two IPCC panels draw on overlapping scientific evidence, not two statistically independent replications.

Inspect source versions and range definitions

Snapshot attribution-v1 preserves SPM.1 version 20221116 and SPM.2 version 20210809. The SPM.1 file marks missing model values with 1.00E+20; they are normalized to unavailable and never plotted as real temperatures. Its model fields contain archived historical-ssp245 and natural-only comparisons, not forecasts run in this browser. CEDA's generic SPM.2 panel-b description says “very likely,” but the official figure caption and SPM A.1.3 say “likely.” This viewer follows the official caption and report, retaining the discrepancy in provenance. No Gaussian distributions or new probability levels are inferred.

Data adapted under CC BY 4.0: Gillett, Malinina, Kaufman and Neukom (2023), SPM.1 data; Szopa and colleagues (2021), SPM.2 data; and IPCC (2021), Summary for Policymakers, pp. 3–32, doi:10.1017/9781009157896.001. This site normalizes missing values, selects records and redraws the numerical evidence; it does not reproduce the published figure artwork.

2019 observed change 1.226 °C. Observed minus human-plus-natural mean 0.036 °C; observed minus natural-only mean 1.177 °C.

Total human influence: assessed center 1.07 °C, likely range 0.80 to 1.30 °C for 2010–2019 relative to 1850–1900. Annual residuals are descriptive comparisons, not significance tests or independently estimated causal contributions.

Observation to attach to a capture

Captures preserve year and driver selections in attribution-v1. They replay comparisons of archived observations, simulation summaries and assessed contributions, not a new attribution analysis or causal experiment.

Understand

Compare explanations with different imposed influences

A counterfactual asks what would happen under a different set of conditions. Here the archived climate simulations compare human-plus-natural forcing with natural-only forcing. Observations provide a third trace. You are inspecting published evidence, not running either climate-model ensemble in the browser.

The natural-only comparison includes solar and volcanic forcing. It does not mean a world without weather fluctuations or internally generated variability. The human-plus-natural comparison includes additional human influences. Asking which comparison reproduces the long-term observed change is more informative than placing two unrelated rising curves beside each other.

The IPCC AR6 Summary for Policymakers presents this comparison as part of a larger attribution assessment. The browser supplies a readable view of archived results; it does not independently repeat that assessment or estimate a new causal probability.

Establish a compatible reference

All three traces describe global surface temperature change relative to 1850–1900. The highlighted-year control selects a row for inspection while the full 1850–2020 context remains visible. Changing the highlighted year does not refit the curves or change their baseline.

This differs from the earlier NASA record, whose native baseline is 1951–1980. A 2024 NASA anomaly cannot be subtracted directly from an AR6 value with another reference and averaging period. Matching the word “temperature” and the unit °C is necessary but insufficient for a valid comparison.

The CEDA SPM.1 archive identifies these as annual observed estimates and CMIP6 simulation summaries. The two simulation series extend through 2019, with observations continuing through 2020. Their bands give the 5th and 95th percentiles across the archived ensembles.

Work through one year

Highlight 2019. Observed change is 1.226°C. The human-plus-natural ensemble mean is about 1.18995°C, while the natural-only mean is about 0.04939°C. Calculate observed minus mean separately: approximately +0.03605°C and +1.17661°C.

These descriptive residuals show that the observed value is much closer to the human-plus-natural mean in this year. The all-forcing band is approximately 0.73826–1.87079°C, while the natural-only band is approximately −0.13632–0.30654°C. Record the observation’s position relative to both without converting band membership into a formal hypothesis test.

On paper, make a ledger with year, observed value, both means, both residuals and a sentence about the full trajectory. Repeat for 1950 and 2000. Predict whether a single early-year comparison will distinguish the trajectories as clearly as a recent one. Inspect the pattern across years rather than selecting only the most persuasive point.

Interpret the evidence without overstating the method

The long-term comparison contributes evidence that human influence is needed to explain the observed warming, consistent with the IPCC attribution synthesis. This conclusion is stronger than “two things happen to increase together”: the assessment combines observations with physically structured comparisons and other evidence.

An ensemble mean is not expected to reproduce every observed annual fluctuation. The source bands describe model spread, not observational error bars or a probability that one explanation is true. A small residual at one date does not validate every process in a model, and a larger residual at another date does not automatically falsify its long-term forced response.

Highlight 2020 as an audit. Observations are present at 1.256°C, but the archived simulation fields are missing. The correct response is to preserve missing means, bounds and residuals. Extending the previous values would fabricate a comparison not supplied by this archive.

Transfer to a missing counterfactual

An unfamiliar annual record supplies an observed anomaly but no natural-only simulation for that year. A learner copies the preceding natural-only mean and reports a residual as though both values were supplied. What should the report do instead?

Check the climate-counterfactuals transfer

Retain the missing simulation and residual as unavailable. Report the observed value with its year and reference, and use a year with both sources for a direct comparison. Copying or extrapolating a value would require an explicitly separate estimation method and would no longer be the archived comparison.

Apply

Public practice checks a specific claim. It does not establish independent mastery.

Explain the counterfactual comparison, what a residual describes and why missing simulation values cannot be silently extended.

Your explanation and limitations

Continue

Completion requires a saved prediction, at least one capture and a reflection. Presence checks do not grade your reasoning.

Skipping retains experiments and awards no mastery.

Previous: Diagnose response curves with independent clues Next: Interpret assessed human and natural contributions

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