Investigate how scientific consensus is established and how it has been challenged, using climate change as a case study

What this dot point is asking

NESA wants you to explain how scientific consensus is established, evaluate the strength of evidence behind the climate consensus and identify how organised denial has challenged it. This is one of the most heavily examined dot points in Module 7.

The answer

The scientific consensus on human-caused climate change is among the strongest in any field, supported by multiple independent lines of evidence and an unbroken physical mechanism dating back to Arrhenius in 1896. Organised denial has nonetheless successfully delayed policy in many countries, often through funded misinformation.

How scientific consensus is built

A consensus emerges through:

1. Peer-reviewed publication. Researchers report findings in journals.
2. Replication. Independent teams test the findings.
3. Synthesis. Expert panels combine the evidence (Cochrane for health, IPCC for climate, NHMRC for medicine).
4. Survey of scientific opinion. Research papers and surveys document agreement.
5. Public communication. Scientific bodies issue position statements.

When multiple independent lines of evidence converge, when no significant peer-reviewed dissent exists, and when expert panels reach high-confidence conclusions, scientific consensus is established.

The climate consensus

Surveys of opinion.

• Cook et al. (2013) reviewed 11,944 peer-reviewed climate papers. Of those expressing a position, 97.1 per cent endorsed anthropogenic warming.
• Verheggen et al. (2014) survey of 1,800 climate scientists found 90 per cent agreement with the IPCC position.
• Lynas et al. (2021) review of recent papers found 99.9 per cent endorsement among climate scientists publishing in the field.

IPCC synthesis.

The Intergovernmental Panel on Climate Change is a UN body that synthesises climate science across thousands of papers every 5 to 7 years. Each assessment report is peer reviewed by hundreds of scientists and reviewed by governments. The Sixth Assessment Report (AR6, 2021 to 2023) concluded:

"It is unequivocal that human influence has warmed the atmosphere, ocean and land."

Multiple lines of evidence.

1. Atmospheric CO2. Increased from 280 ppm in 1750 to over 425 ppm in 2024. Mauna Loa record (Keeling, since 1958), ice cores (going back 800,000 years).
2. Surface temperature. Risen 1.2 degrees Celsius since 1900. Multiple independent datasets (NASA GISS, NOAA, HadCRUT, JMA, Berkeley Earth, Bureau of Meteorology) agree.
3. Ocean heat content. Rising steadily as the ocean absorbs over 90 per cent of the extra energy.
4. Sea level. Risen approximately 20 cm since 1900 and accelerating.
5. Glacier and ice-sheet mass loss. Greenland, Antarctica and almost every mountain glacier are losing mass.
6. Sea ice. Arctic sea ice in summer reduced by about 40 per cent since 1979.
7. Isotope fingerprint. The carbon-14 ratio of atmospheric CO2 shows the added carbon is from fossil fuel combustion (depleted in C-14 because fossil fuels are too old to contain it).
8. Mechanism. CO2 absorbs infrared. Predicted by Arrhenius in 1896 and Tyndall in 1859. Confirmed by direct satellite measurements of the Earth's outgoing infrared spectrum.

Australian science contributions

• Bureau of Meteorology. Continuous Australian surface temperature record from 1910. Average warming 1.5 degrees Celsius since 1910.
• CSIRO. Greenhouse gas measurements from Cape Grim, Tasmania. The southern hemisphere reference station for global atmospheric CO2.
• Australian Antarctic Division. Antarctic ice core analysis (Vostok and EPICA records).
• Australian universities. Major contributions to IPCC working groups.

Organised denial

Denial of the climate consensus has been organised and funded primarily by fossil-fuel-related interests since the 1980s. Documented examples:

ExxonMobil internal documents (1977 to 1989)

ExxonMobil scientists privately concluded that anthropogenic warming was real and serious. The company publicly funded denial campaigns through the 1990s and 2000s.

Industry-funded think tanks

The George C. Marshall Institute, Heartland Institute, and in Australia the Institute of Public Affairs have produced reports questioning climate science.

Front organisations

The Global Climate Coalition (1989 to 2002) opposed climate policy. Its industry funders later abandoned the body, but its rhetorical strategies persisted.

Australian context

The Murdoch press (especially The Australian) has consistently published columns questioning climate science. Both the Liberal-National Coalition and Labor have at various times responded to denial pressure by weakening policy.

Common denial tactics

Why denial succeeds despite evidence

Several factors contribute:

1. Asymmetric burden. Climate scientists must explain complex evidence; deniers need only seed doubt.
2. Funding asymmetry. Industry-funded denial campaigns far outspent public communication.
3. Cognitive biases. Confirmation bias and motivated reasoning favour comforting conclusions.
4. Media practices. False balance and click-driven coverage amplify dissenting voices disproportionately.
5. Political alignment. Climate has become culturally coded with political identity in some countries.

Why this is not a failure of science

The scientific process has worked: it has produced a robust consensus, communicated it, and updated it as evidence accumulated. The failure is at the science-policy and science-public interface.

The lesson is not that consensus is unreliable, but that scientific consensus alone is insufficient to drive policy when organised counter-messaging is funded and politically aligned. This is the core challenge of public science communication today.

Comparison with smoking and tobacco

The climate denial playbook closely parallels the earlier tobacco industry playbook (Doubt is Our Product, by Big Tobacco's lawyers). Both:

• Funded contrarian scientists.
• Created front organisations.
• Demanded "scientific certainty" before policy action.
• Targeted regulatory processes.

Several key denial spokespeople (Frederick Seitz, Fred Singer) worked in both industries. The strategies, networks and tactics are documented in Naomi Oreskes and Erik Conway's Merchants of Doubt (2010).