There is a low but uncertain probability that climate change could trigger “mega-catastrophes, ” severe and at least partly irreversible adverse effects across broad regions. This paper first discusses the state of current knowledge and the defining characteristics of potential climate change mega-catastrophes. While some of these characteristics present difficulties for using standard rational choice methods to evaluate response options, there is still a need to balance the benefits and costs of different possible responses with appropriate attention to the uncertainties. To that end, the authors present a qualitative analysis of three options for mitigating the risk of climate mega-catastrophes—drastic abatement of greenhouse gas emissions, development and implementation of geoengineering, and large-scale ex ante adaptation—against the criteria of efficacy, cost, robustness, and flexibility. They discuss the composition of a sound portfolio of initial investments in reducing the risk of climate change mega-catastrophes. This paper—a product of the Environment and Energy Team, Development Research Group—is part of a larger effort in

Climate change is characterized by deep structural uncertainty in the science coupled with an economic inability to evaluate meaningfully the welfare losses from high temperature changes. The probability of a disastrous collapse of planetary welfare from too much CO2 is non-negligible, even if this low probability is not objectively knowable. This paper attempts to explain (in not excessively technical language) some of the most basic issues in modeling the economics of catastrophic climate change. The paper builds to a tentative conclusion that, no matter what else is done realistically to slow CO2 buildups, economic analysis lends some support to undertaking serious research now into the prospects of “fast geoengineering preparedness ” – as a state-contingent emergency option o¤ering at least the possibility of knocking down catastrophic temperatures rapidly. 1

Malicious software (“malware”) has become a serious security risk to all users of the Internet, whether they are large or small organizations or home users. Viruses, worms and numerous other variants of malware have developed from a nuisance to sophisticated tools for criminals. Computers all across the world, some estimate as many as 1 in 10 to 1 in 5, are infected with

he that increaseth knowledge increaseth sorrow Ecclesiastes 1:18 Information hazards are risks that arise from the dissemination or the potential dissemination of true information that may cause harm or enable some agent to cause harm. Such hazards are often subtler than direct physical threats, and, as a consequence, are easily overlooked. They can, however, be important. This paper surveys the terrain and proposes a taxonomy. 1.

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Humanity faces many important decisions about space exploration. An important but controversial decision making paradigm is cost-benefit analysis (CBA). This paper discusses some ethical considerations in CBA that are important to decision making about space exploration, including: how we define costs and benefits; space exploration’s non-market value; the standing of future humans and of extraterrestrials; and the role of discounting in evaluating long-term space exploration projects. 1.

Risk is generally defined as the product of probability and magnitude. Global catastrophic risks (GCRs) are risks of the highest magnitude, regardless of their probability. As defined by Bostrom and Ćirković, global catastrophes are events that cause roughly 10 million deaths or $10 trillion in damages or more (p.2). Thus, even if the probability of a global catastrophe is low, it may constitute a substantial risk. GCR has attracted a modest amount of recent attention, including Leslie (1996), Rees (2003), Posner (2004), Matheny (2007), and Sunstein (2007). The present book is a very welcome addition to this literature. Whereas the preceding writings are all solo-author efforts, the present book brings together 25 authors across 22 chapters covering a near-comprehensive wide range of GCRs as well as a rich section on cross-GCR methodology. GCR is a massively interdisciplinary topic and thus is more conducive to this sort of collaborative effort. Traditionally, GCRs are studied individually by independent research communities. This book is an effort to redirect research towards more integrated efforts. One might object that quality suffers in the face of such breadth. However, only by studying multiple GCRs together can one consider which might be most pressing. Furthermore, integrated GCR study also reveals many