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Judgments of moral responsibility should be informed by both scientific analysis and societal standards. Society distinguishes responsibilities into positive and negative, general and special, and backward-looking and forward-looking. Ekwurzel et al. in Clim Chang 2017 shows that 90 major carbon producers have contributed most of the atmospheric CO 2 emissions. Once it became clear no later than the 1960s that continuing CO 2 emissions would progressively undermine the climate, the major carbon producers could see that they were marketing harmful products. The simple and merely negative responsibility to “do no harm” required them to reduce that harm rapidly either by modifying the product in order to capture its dangerous emissions or by developing safe substitutes to perform the same function, that is, by developing non-carbon-based forms of energy. The seriousness of the harms brought by climate change made this responsibility especially compelling. Ceasing to contribute to harm includes ending exploration for additional fossil fuels. The half century of failure by corporate carbon producers to reduce the harms caused by their products now gives them additional responsibility to correct the damage done by their decades of neglect of the underlying negative responsibility. If major carbon producers also wish to fulfill the general responsibility to make more than a minimal positive social contribution, their distinctive capacities of political power, wealth, and expertise qualify them for leadership in the transition to an energy regime that would be safe for future generations to rely on.

The science of event attribution meets a mounting demand for reliable and timely information about the links between climate change and individual extreme events. Studies have estimated the contribution of human-induced climate change to the magnitude of an event as well as its likelihood, and many types of event have been investigated including heatwaves, floods, and droughts. Despite this progress, such approaches have been criticised for being unreliable and for being overly conservative. We argue that such criticisms are misplaced. Rather, a false dichotomy has arisen between “conventional” approaches and new alternative framings. We have three points to make about the choice of statistical paradigm for event attribution studies. First, different approaches to event attribution may choose to occupy different places on the conditioning spectrum. Providing this choice of conditioning is communicated clearly, the value of such choices depends ultimately on their utility to the user concerned. Second, event attribution is an estimation problem for which either frequentist or Bayesian paradigms can be used. Third, for hypothesis testing, the choice of null hypothesis is context specific. Thus, the null hypothesis of human influence is not inherently a preferable alternative to the usual null hypothesis of no human influence.

Grassi et al comment on a study by Plugge et al. (2012) in which they analyzed the implications of applying the principle of conservativeness in the context of uncertainties of carbon stock change estimates in reducing emissions from deforestation and forest degradation ( REDD+). Grassi et al make the case that implementing conservativeness in REDD+ is realistic and useful in addressing uncertain estimates of carbon stock to reduce such emissions.

A recent paper in this journal argues that the choice of statistical model is responsible for the divergence in damage estimates of climate change on US agriculture. We provide five arguments why we believe this assertion is misguided.

REDD+, a mechanism for reducing emissions from deforestation and forest degradation, which has now been extended to include conservation, management, and enhancement of forest carbon stocks (thus REDD+), is intended to reward developing countries for the mitigation of greenhouse gas emissions (UNFCC 2010). Knoke comments on a study by Plugge et al in which they propose using the principle of conservativeness to guarantee emission reductions. Inspired by their paper, Knoke will develop some considerations of his own in an attempt to broaden the discussion on possible implications of an implementation of the conservativeness approach.

The history of science is a chronicle of epistemic frailty: both facts and theories have toppled in the face of new evidence and new interpretations of old evidence. From this, philosophers make a pessimistic meta-induction: since previously well-established scientific knowledge has been shown to be wrong, incomplete, partial or false, what does this say about our current knowledge? We must conclude that at least some of it will be rejected in the future as having been mistaken.

Myanna Lahsen is concerned about the backlash to climate policy triggered by Climategate in 2009. To counteract such backlash in the future she recommends more symmetrical studies of the social aspects of climate science. There is a need to study distorting extra-scientific factors on standard climate science. The study of climate deniers or contrarians as in Merchants of Doubt (Oreskes and Conway 2010) is not enough. There is a dominance of idealized understandings of science on both sides in the climate debates, and this makes the public vulnerable to backlash campaigns, claims Lahsen (2013). And this widespread misunderstanding needs to be revealed before political progress can be made.

Assessments conducted by the Intergovernmental Panel on Climate Change (IPCC) are significant undertakings that require input from experts and practitioners in multiple scientific disciplines, integrating local to international information across spatial and temporal scales. An IPCC report is a unique collaboration between the scientific community and policymakers, with governments (through their Focal Points) providing guidance and input to the scientists conducting an assessment at several stages during the process. This commentary reviews the IPCC mandate and process; summarizes key themes to be addressed in the Working Group II contribution to the 5th assessment report; discusses challenges for the WGII report when assessing qualitative literature, incorporating local knowledge, and identifying particularly vulnerable groups; and touches on the expertise and commitment of the WGII authors. Active engagement of the wider scientific community in IPCC assessments through publication and review will enhance their relevance to decision- and policy-makers.

The current approach to climate action has been to throw things against the wall to see what sticks. Figuring out the correct response first requires an examination of current approaches. The business case is the most common and non-confrontational solution. It seems reasonable that a solution should focus on values too.