We assess climate impacts of global warming using ongoing observations and paleoclimate data. We use Earth’s measured energy imbalance, paleoclimate data, and simple representations of the global carbon cycle and temperature to define emission reductions needed to stabilize climate and avoid potentially disastrous impacts on today’s young people, future generations, and nature. A cumulative industrial-era limit of ∼500 GtC fossil fuel emissions and 100 GtC storage in the biosphere and soil would keep climate close to the Holocene range to which humanity and other species are adapted. Cumulative emissions of ∼1000 GtC, sometimes associated with 2°C global warming, would spur “slow” feedbacks and eventual warming of 3–4°C with disastrous consequences. Rapid emissions reduction is required to restore Earth’s energy balance and avoid ocean heat uptake that would practically guarantee irreversible effects. Continuation of high fossil fuel emissions, given current knowledge of the consequences, would be an act of extraordinary witting intergenerational injustice. Responsible policymaking requires a rising price on carbon emissions that would preclude emissions from most remaining coal and unconventional fossil fuels and phase down emissions from conventional fossil fuels.

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Navigating global changes requires a coevolving set of collaborative, global institutions.

The integrated assessment models (IAMs) that economists use to analyze the expected costs and benefits of climate policies frequently suggest that the "optimal" policy is to go slowly and to do relatively little in the near term to reduce greenhouse gas emissions. We trace this finding to the contestable assumptions and limitations of IAMs. For example, they typically discount future impacts from climate change at relatively high rates. This practice may be appropriate for short-term financial decisions but its extension to intergenerational environmental issues rests on several empirically and philosophically controversial hypotheses. IAMs also assign monetary values to the benefits of climate mitigation on the basis of incomplete information and sometimes speculative judgments concerning the monetary worth

Many analytical approaches to setting environmental standards require some consideration of costs and benefits. Even technologybased regulation, maligned by cost-benefit enthusiasts as the worst form of regulatory excess, typically entails consideration of economic costs. Cost-benefit analysis differs, however, from other analytical approaches in the following respect: it demands that the advantages and disadvantages of a regulatory policy be reduced, as far as possible, to numbers, and then further reduced to dollars and cents. In this feature of cost-benefit analysis lies its doom. Indeed, looking closely at the products of this pricing scheme makes it seem not only a little cold, but a little crazy as well. Consider the following examples, which we are not making up. They are not the work of a lunatic fringe, but, on the contrary, they reflect the work products of some of the most influential and reputable of today's cost-benefit practitioners. We are not sure whether to laugh or cry; we find it impossible to treat these studies as serious contributions to a rational discussion. Several years ago, states were in the middle of their litigation against tobacco companies, seeking to recoup the medical expenditures they had incurred as a result of smoking. At that time, W. Kip Viscusi-a professor of law and economics at Harvard and the primary source of the current $6.3 million estimate for the value of a statistical life'-undertook research concluding that states, in fact, saved money

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More than 25 years after the discovery that the equilibrium point of a general equilibrium model is not necessarily either unique or stable, there is still a need for an intuitively comprehensible explanation of the reasons for this discovery. Recent accounts identify two causes of the finding of instability: the inherent difficulties of aggregation, and the individualistic model of consumer behaviour. The mathematical dead end reached by general equilibrium analysis is not due to obscure or esoteric aspects of the model, but rather arises from intentional design features, present in neoclassical theory since its beginnings. Modification of economic theory to overcome these underlying problems will require a new model of consumer choice, nonlinear analyses of social interactions, and recognition of the central role of institutional and social constraints.General Equilibrium Theory, Instability, Sonnenschein-MANTEL-DEBREU Theorem, Mathematical Modelling, Economics And Physics, Mirowski,