IPCC’s New Report: Does It Make any Ethical Difference that Confidence Levels About Human Causation Have Increased?



The New York Times reported on August 19 that the Intergovernmental Panel on Climate Change (IPCC) will soon issue its 5th assessment report that will  state that the scientific consensus that humans are causing climate change has increased from a 90% probability in 2007 to a 95% probability in the new report.  This new report, according to the New York Times, will assert that expected warming in this century will lead to wide-spread melting of land ice, extreme heat waves, difficulty growing food and massive changes in plant and animal life, probably including a wave of extinctions.  Yet such predictions about climate change’s impacts have been made for well over thirty years.

One might ask whether the change in confidence levels from 90% to 95% makes a difference as a matter of ethics.  We believe it does not because those causing climate change have had clear ethical duties to reduce the threat of climate change once they were put on notice that their actions were likely putting others at great risk. This is information that was widely available three decades ago. Ethical duties to not create harm begin once someone is put on notice that their behavior is likely to cause great harm particularly in regard to actions about which:

  • Waiting to take action will make the problem worse;
  • Delays will make it much harder to prevent catastrophic impacts;
  • Those who are most at risk have not consented to be placed at further risk;
  • The harms from the dangerous behavior are not mere inconveniences but potentially catastrophic destruction of life and ecological system on which life depends;
  •  Much of the science on which the projections of catastrophic harms is based is not controversial and has been well established for many decades;
  •  The vast majority of the scientists that do peer-reviewed science on climate change support the conclusion that humans are likely changing the Earth’s climate in ways that will create great harms for the most vulnerable people on the planet.

new book description for website-1_01Under these circumstances, one does not need complete certainty before ethical obligations to do no harm are triggered. Once someone is put on notice that his or her behavior is greatly dangerous, they have a duty to stop the dangerous behavior. This duty is particularly strong when the harms are potentially great as they are in the case of climate change. This ethical duty to cease dangerous behavior is widely recognized in criminal codes around  the world that make many kinds of dangerous behavior criminal. In the United States, for instance, reckless driving and reckless endangerment are criminal violations. (For more on ethics and uncertainty see, On Confusing Two Roles of Science and Their Relation to Ethics.)

Some economists will argue that a change from 90% to 95% confidence levels is ethically relevant when calculating expected utility from climate change policies when cost-benefit analyses of policies are applied to climate change policies. Yet, as we have explained in many articles on this subject, cost-benefit analysis is a deeply ethically problematic policy tool for climate change. Its use seeks to find polices which maximizes utility while ignoring questions of distributive justice, ethical obligations based upon duties to prevent harm, human rights violations, procedural justice considerations that would give victims of harms rights to participate in decisions that impose risks,  and many other ethical issues. (See, Ethical Issues Entailed By Economic Arguments Against Climate Change Policies.)

We do not deny that higher levels of confidence that activities are harming others strengthen the ethical duty to take action, however the duty to reduce ghg emissions has existed since the scientific community has been describing the threats of climate change three decades ago.

Insistence on absolute certainty before governments intervene in markets on climate change has been a tactic of the climate change disinformation campaign on climate change for several decades. As a matter of ethics high-emitting nations and individuals have had clear ethical duties to reduce ghg emissions to their fair share of safe global emissions for over thirty years.



Donald A. Brown

Scholar In Residence, Sustainability Ethics and Law


Widener University School of Law

Visting Professor, Nagoya University, Nogoya, Japan




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