A central skill in scientific inquiry is evaluating whether evidence supports or refutes a scientific hypothesis, model or theory. This requires understanding what hypotheses, models and theories are, and what forms of evidence are relevant.
| Term | Definition | Environmental Science Example |
|---|---|---|
| Hypothesis | A testable, falsifiable prediction about the relationship between variables | ‘Greater vegetation cover increases bird SID’ |
| Model | A simplified representation of a real system used to explain or predict phenomena | Climate model (GCM) predicting temperature response to emissions |
| Theory | A well-substantiated explanation supported by extensive evidence from multiple lines of inquiry | The theory of evolution by natural selection; plate tectonic theory |
A hypothesis is tentative and specific; a theory is robust and broadly supported.
Scientific inquiry follows a logical structure:
Falsifiability: A good hypothesis must be potentially falsifiable — there must be possible observations that could contradict it.
| Outcome | Meaning | Implication |
|---|---|---|
| Supports | Data is consistent with the hypothesis; observations match predictions | Hypothesis remains viable; collect more evidence |
| Refutes | Data is inconsistent with the hypothesis; key predictions are not met | Hypothesis should be revised or rejected |
Important: A hypothesis is never ‘proven’ beyond all doubt by a single study. Strength comes from repeated testing across diverse conditions. A hypothesis is only rejected if it is consistently contradicted across rigorous, independent studies.
Hypothesis: “The recent increase in global average temperature is caused by human greenhouse gas emissions.”
Supporting evidence:
- CO$_2$ concentrations and temperature rise correlate precisely with industrial era emissions
- Isotopic analysis of atmospheric CO$_2$ shows increasing proportion of fossil-fuel-derived carbon
- Climate models including human GHG forcing reproduce observed temperature rise; models without human forcing do not
- The pattern of warming (e.g. stratospheric cooling while troposphere warms) matches the GHG mechanism specifically — not solar activity
- Multiple independent datasets (temperature records, sea level, ice extent) all show consistent trends
Potentially refuting evidence that was NOT found:
- If solar output had increased proportionately with temperature rise — it hasn’t
- If stratosphere had warmed alongside troposphere — it has cooled, consistent with GHG warming
- If warming stopped when ocean oscillation changed — it hasn’t
Climate models are not hypotheses but tools for understanding and prediction. Evidence that a model is reliable includes:
Model limitations reduce confidence:
- Models may not adequately represent: clouds; small-scale ocean processes; permafrost feedbacks; human behavioural responses
- Regional projections have more uncertainty than global ones
When writing up an investigation, students must:
1. State clearly whether data supports or does not support the hypothesis
2. Justify this with reference to specific data (trend direction, magnitude, SID values etc.)
3. Acknowledge limitations that reduce confidence in the conclusion
4. Avoid claiming data ‘proves’ the hypothesis
Language guidance:
- ‘The data supports the hypothesis because…’
- ‘The results are consistent with the hypothesis that…’
- ‘The hypothesis cannot be supported because…’
- ‘This conclusion is limited by…’
VCAA FOCUS: A common error is stating ‘the results prove the hypothesis’. Scientific evidence supports or refutes — it does not prove. VCAA also frequently asks students to distinguish between correlation and causation in environmental data.
