SCIENCE · INVESTIGATE AND EXPLAIN

Interpret assessed human and natural contributions

Distinguish combined human influence from warming and cooling components over a shared historical period.

Learning outcome: Explain the assessed attribution conclusion without double-counting totals or treating central zero as absence.

Starting recap

The contributions panel assesses 2010–2019 relative to 1850–1900, independently of the highlighted annual row.

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Try

Observed warming is 1.06°C centrally; total human influence is 1.07°C, with greenhouse-gas warming partly offset by other human drivers.

Open the experiment

Predict

Can greenhouse-gas warming exceed the observed net change when other influences contribute cooling?

Your prediction and reason

Experiment

Highlight all five driver categories and build a hierarchy showing which human categories are contained in the total.

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

Read contributions over one shared interval

The assessed-contributions panel concerns warming in 2010–2019 relative to 1850–1900. Its values are decade-scale assessments, not annual temperatures at the highlighted year in the neighboring timeline. Keep those periods written beside your paper calculations.

Observed warming has a central estimate of 1.06°C. The central estimate attributed to total human influence is 1.07°C. Their closeness supports the assessment that human influence accounts for the observed warming over this interval. The 0.01°C difference between central estimates is not a newly detected cooling process or an exact residual to assign to a single cause.

These values come from IPCC AR6 Figure SPM.2 data archived at CEDA. They summarize attribution studies combining observations and models. They are not direct thermometer readings of separate human and natural effects.

Separate a total from its components

Highlight total human influence, then well-mixed greenhouse gases and other human drivers. The greenhouse-gas central contribution is +1.50°C. Other human drivers have a central contribution of −0.40°C, reflecting a net cooling influence from that category. Human activities can therefore contribute effects with opposite signs.

Total human influence already includes human warming and cooling contributions. Adding 1.07 + 1.50 − 0.40 would count overlapping categories twice. Instead, use the total for a statement about combined human influence and the component categories to explain why that total is smaller than greenhouse-gas warming alone.

The rounded component centers sum to +1.10°C rather than exactly +1.07°C. Do not alter the source total to force an exact identity. Rounded summaries and separately assessed totals need not close like an exact numerical conservation ledger. Their uncertainty and estimation methods matter.

For a paper activity, draw a large box labeled total human influence, with greenhouse gases and other human drivers inside it. Place solar/volcanic drivers and internal variability outside that box. This hierarchy prevents a visually attractive stacked chart from silently double-counting the human total.

Keep natural forcing and internal variability distinct

Solar and volcanic drivers have a central contribution of 0.00°C with an assessed likely range from −0.10 to +0.10°C. Internal variability has a central contribution of 0.00°C with a likely range from −0.20 to +0.20°C. A central zero over this assessed interval does not mean either category is physically absent or unable to affect individual years.

Natural forcing changes external influences on the climate system. Internal variability arises within the system. They should not be merged into a vague category called “anything uncertain.” Their intervals are much smaller than the observed warming over the shared assessed period, supporting the broader attribution conclusion rather than an explanation based solely on natural contributions.

The IPCC Summary for Policymakers, section A.1.3 gives the assessed ranges and interpretation. It is the scientific synthesis behind these summaries, not the result of a new statistical test performed by the browser.

Use signs without inventing policy conclusions

The other-human category includes a net cooling contribution; that is not a recommendation to increase harmful pollutants. The panel describes contributions to historical temperature change, not health effects, environmental costs or a policy optimization. A scientific explanation should preserve the category’s scope.

Highlight each driver and write one sentence identifying its sign, range and relationship to the total. Then explain why greenhouse-gas warming can exceed observed net warming when other contributions partly offset it. This is an accounting interpretation of the assessment, not a forecast obtained by switching a driver off today.

Transfer by repairing a total

A report adds total human influence to the greenhouse-gas and other-human categories, claiming a combined human contribution of 2.17°C. Identify the overlap and write an appropriate historical claim instead.

Check the warming-contributions transfer

The total human category already includes the component human categories. Use the assessed total central estimate 1.07°C, with its likely 0.80–1.30°C range, for 2010–2019 relative to 1850–1900. The components explain the opposing influences; they are not additional contributions on top of the total.

Apply

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

Explain the supported historical conclusion, category signs and why rounded components need not exactly reconstruct the assessed total.

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: Compare observed warming with forcing counterfactuals Next: Match attribution intervals to their meaning

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