Students should be able to: evaluate the quality of evidence in a report…

The idea

When you read a report about global climate change, judge the evidence rather than accept the conclusion. Check the source, whether data are peer reviewed, how many measurements and how long a record they cover, whether the method is reproducible and whether the conclusion follows. Uncertainty is normal: measurements have limits, natural variation is large, and models simplify reality, so scientists give ranges rather than single values. Peer review means other experts examine methods and conclusions before publication, which improves quality but does not prove a claim. Communicating results to the public, policymakers and other scientists allows scrutiny and informed decisions. A useful method is to list strengths, weaknesses and what further evidence would reduce uncertainty.

What earns the marks

• Judge evidence by source, peer review, sample size, timescale, reproducibility and whether the conclusion follows from the data.
• Describe uncertainty as a range or limitation arising from measurement, natural variation or model simplification, not as a failure of science.
• Explain that peer review involves independent experts checking methods, data and conclusions before publication.
• Explain that communicating results to scientists, policymakers and the public allows scrutiny, replication and informed decisions.
• Use a specific example, such as a long temperature record from many stations being stronger evidence than one local measurement.
• Suggest how uncertainty could be reduced, for example by more measurements, longer records or improved models.

Common mistakes and how to put them right

• Saying peer review proves a result is true.

  Put it right by saying it checks quality and reduces the chance of error, but conclusions can still be revised.

• Treating uncertainty as meaning scientists know nothing.

  Put it right by explaining that uncertainty is a quantified range around a well-supported finding.

• Judging a report only by whether you agree with it.

  Put it right by checking the evidence, method and source instead.

Exam tips

• Use the supplied information: name the specific strength or weakness you can see rather than giving general opinions.
• Structure an evaluation as strengths, weaknesses and a justified overall judgement.
• When describing uncertainty, give a cause and an effect, such as limited stations leading to a wider range.