Article 2 ͉ UNFCCC ͉ climate change impacts A rticle 2 of the United Nations Framework Convention on Climate Change (UNFCCC) commits signatory nations to stabilizing greenhouse gas concentrations in the atmosphere at a level that ''would prevent dangerous anthropogenic interference (DAI) with the climate system.'' The UNFCCC also highlights 3 broad metrics with which decision-makers are to assess the pace of progress toward this goal: allow ''ecosystems to adapt naturally to climate change,'' ensure that ''food production is not threatened,'' and enable ''economic development to proceed in a sustainable manner.'' In an effort to provide some insight into impacts that might be considered DAI, authors of the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC) identified 5 ''reasons for concern'' (RFCs) in (1). Each RFC categorizes impacts of a similar type, providing a set of metrics reflecting severity of risk. Relationships between various impacts reflected in each RFC and increases in global mean temperature (GMT) were portrayed in what has come to be called the ''burning embers diagram''; the image was also included in the Summary for Policy Makers of the contribution of Working Group II to the TAR and highlighted in the Synthesis Report.In presenting the ''embers'' in the TAR, IPCC authors did not assess whether any single RFC was more important than any other; nor, as they noted, did they conclude what level of impact or what atmospheric concentrations of greenhouse gases would constitute DAI, a value judgment that would be policyprescriptive. The ''embers'' were designed primarily to communicate the associations of impacts with increases in GMT and facilitate examination of the underlying evidence for use by decision-makers contemplating responses to these concerns.The IPCC Fourth Assessment Report (AR4) states that ''the 'reasons for concern' identified in the TAR remain a viable framework for assessing key vulnerabilities'' (2). In this article, we revise sensitivities of the RFCs to increases in GMT, based on our expert judgment about new findings in the growing literature since the publication of the TAR in 2001.* Furthermore, our judgments are supported by a more thorough understanding of the concept of vulnerability that has evolved over the past 8 years, † as well as a more careful articulation of the criteria by which any specific vulnerability can be labeled ''key,'' and thus contribute to a reason for concern (3). ‡ Section 1 defines and reviews the RFCs and ''burning embers'' figure as presented in the IPCC TAR. Section 2 presents the 1 To whom correspondence may be addressed. E-mail: jsmith@stratusconsulting.com or shs@stanford.edu. *These judgments were vetted by 3 rounds of IPCC review and were approved in the Summary for Policymakers of both the AR4 Working Group 2 and Synthesis Reports by the IPCC Plenary. † Vulnerability to climate change is the degree to which geophysical, biological and socioeconomic systems are susceptible to and unable to cope with adve...

Many and varied claims have been made over many years for a relationship between weather or climate and solar variations, notably sunspot cycles. Those relating primarily to the single and double sunspot cycles (of about 11‐ and 22‐year quasi‐periodicities) are critically reviewed in the light of what is known about solar variations, the observed variability of weather and climate, and possible physical connections between the two. Various pitfalls in the application or lack of application of statistics to the problem are discussed and illustrated from the literature. Following a survey of the literature it is concluded that despite the great number of recent papers on the subject, little convincing evidence has yet been produced for real correlations between sunspot cycles and the weather/climate on the 11‐ and 22‐year time scales, although evidence for correlations with solar events on time scales of days appears to exist. The state of the literature in this particularly controversial area must raise doubts as to the prevailing standards of objectivity and critical analysis in other areas of science as well. Clearly, in the case of sun‐weather relationships, further research requires much higher standards of objectivity, with the rigorous and critical application of statistics, and step by step investigation of hypothetical mechanisms. This criticism is not addressed to the recent studies of apparently significant correlations between certain meteorological indices and the passage of interplanetary magnetic sector boundaries; however, the relevance of such correlations to time scales of climatic interest has yet to be demonstrated.

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