Introduction

This guide explains how climate science evidence is used in climate litigation and outlines evidentiary needs across different case types. As climate lawsuits expand globally, courts increasingly rely on scientific evidence to assess climate risks, policy adequacy and responsibility for emissions. The guide clarifies how scientific research, expert testimony and climate modelling support legal arguments.

Climate litigation and the role of evidence

Scientific evidence plays a central role in demonstrating links between greenhouse gas emissions, climate change and resulting harms. Courts rely on established climate science to evaluate responsibility and policy adequacy. Evidence often includes peer-reviewed research, climate models, emissions data and impact studies. Climate attribution science increasingly supports claims connecting emissions to specific climate damages.

Structure of the guide

The guide explains evidentiary standards used in climate litigation and examines how scientific evidence supports three major categories of cases: government framework cases, corporate framework cases and polluter-pays cases. It highlights the role of scientific consensus, expert interpretation and emerging research methods in supporting legal arguments.

Overview of case strategies

Climate litigation strategies broadly fall into three categories. Government framework cases challenge whether national climate policies align with international climate goals. Corporate framework cases assess whether companies’ strategies and emissions reductions align with climate targets. Polluter-pays cases seek liability or compensation for damages caused by greenhouse gas emissions.

Part 1. Standards of evidence: Similarities across cases

An emerging hierarchy of evidence in climate litigation

Courts increasingly rely on a hierarchy of scientific evidence. At the highest level are widely accepted scientific assessments, particularly those synthesised in major international reports. Below this are peer-reviewed studies, climate models and observational datasets. Expert reports prepared for litigation translate scientific findings into case-specific analysis.

The role of the IPCC and the landmark special report on 1.5 degrees

The Intergovernmental Panel on Climate Change (IPCC) provides authoritative assessments widely used in climate litigation. The Special Report on Global Warming of 1.5°C established strong scientific consensus on the urgency of limiting warming and defined emissions pathways consistent with this goal. Courts frequently rely on IPCC findings to establish baseline climate facts and assess policy adequacy.

The role of scientists as experts in climate litigation

Scientists often serve as expert witnesses, providing independent analysis of climate data, emissions pathways and attribution studies. Expert testimony helps courts interpret complex scientific information and apply it to legal questions. Credibility, transparency of methods and reliance on peer-reviewed research are key factors determining evidentiary weight.

Other roles scientists can play in climate litigation

Scientists may also support litigation indirectly by advising legal teams, interpreting technical evidence or assessing scientific claims made by opposing parties. Collaboration between scientists and legal practitioners can strengthen evidentiary arguments and ensure scientific accuracy in court proceedings.

Part 2. Evidence across different climate litigation case types

Government framework cases

Government framework cases evaluate whether national climate policies align with international climate commitments and scientific benchmarks. Scientific evidence is used to assess emissions trajectories, carbon budgets and policy effectiveness relative to global climate targets.

Understanding global climate targets

Global climate targets are derived from international agreements such as the Paris Agreement. Climate science defines emissions reductions needed to limit warming to 1.5°C or well below 2°C. Carbon budget analyses estimate the remaining allowable emissions consistent with these temperature limits.

Assessing conformity of national action with global targets

Courts assess whether government policies and emissions pathways are consistent with Paris-aligned trajectories. Scientific modelling and emissions projections help evaluate whether national targets adequately contribute to global mitigation goals.

Climate impacts
Evidence on climate impacts supports claims about harm and urgency. Observational data and modelling studies demonstrate rising temperatures, sea-level rise and increased frequency of extreme weather events, providing context for assessing policy adequacy.

Corporate framework cases

Pathways for companies

Corporate framework litigation evaluates whether companies’ strategies align with sectoral decarbonisation pathways consistent with global climate targets. Scientific benchmarks and industry transition pathways provide reference points for assessing corporate climate commitments.

Assessing defendants’ actions

Courts assess companies’ emissions reductions, transition plans and disclosure practices. Evidence may include corporate emissions data, climate strategies and comparisons with scientifically defined pathways.

Non-pathway approaches and ‘Red Lines’

Some litigation evaluates corporate conduct against broader scientific or ethical thresholds rather than specific pathways. Examples include continued expansion of fossil fuel production or failure to align business strategies with climate goals.

Polluter pays cases

Causal chains

Polluter-pays cases seek to establish causal chains linking emissions to climate change and resulting damages. Scientific evidence connects greenhouse gas emissions to temperature increases and to specific impacts such as extreme weather events.

Knowledge and historical responsibility

Historical emissions data and documentary evidence may demonstrate that companies or governments understood climate risks but failed to act. Such evidence can support arguments regarding responsibility for cumulative emissions.

Assessing and quantifying damage

Attribution science and impact assessments help quantify climate-related damages. Studies linking climate change to specific events enable courts to estimate losses associated with climate impacts.

Conclusion and outlook: Science in new settings

Climate litigation is expanding as scientific evidence becomes more sophisticated and accessible. Advances in attribution science, climate modelling and emissions accounting strengthen the ability of courts to assess responsibility and damages. Continued collaboration between scientists and legal practitioners will likely shape future climate litigation.