This is the first part of a three-volume work on the nature of power in human societies. In it, Michael Mann identifies the four principal 'sources' of power as being control over economic, ideological, military, and political resources. He examines the interrelations between these in a narrative history of power from Neolithic times, through ancient Near Eastern civilisations, the classical Mediterranean age, and medieval Europe, up to just before the Industrial Revolution in England. Rejecting the conventional monolithic concept of a 'society', Dr. Mann's model is instead one of a series of overlapping, intersecting power networks. He makes this model operational by focusing on the logistics of power - how the flow of information, manpower, and goods is controlled over social and geographical space-thereby clarifying many of the 'great debates' in sociological theory. The present volume offers explanations of the emergence of the state and social stratification.
Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008. We find that this hiatus in warming coincides with a period of little increase in the sum of anthropogenic and natural forcings. Declining solar insolation as part of a normal eleven-year cycle, and a cyclical change from an El Nino to a La Nina dominate our measure of anthropogenic effects because rapid growth in short-lived sulfur emissions partially offsets rising greenhouse gas concentrations. As such, we find that recent global temperature records are consistent with the existing understanding of the relationship among global surface temperature, internal variability, and radiative forcing, which includes anthropogenic factors with well known warming and cooling effects. (1), combined with rising concentrations of atmospheric CO 2 and other greenhouse gases, prompts some popular commentators (2, 3) to doubt the existing understanding of the relationship among radiative forcing, internal variability, and global surface temperature. This seeming disconnect may be one reason why the public is increasingly sceptical about anthropogenic climate change (4).Recent analyses address this source of scepticism by focusing on internal variability or expanding the list of forcings. Model simulations are used to suggest that internal variability can generate extended periods of stable temperature similar to 1999-2008 (5). Alternatively, expanding the list of forcings to include recent changes in stratospheric water vapor (6) may account for the recent lack of warming. But neither approach evaluates whether the current understanding of the relationship among radiative forcing, internal variability, and global surface temperature can account for the timing and magnitude of the 1999-2008 hiatus in warming.Here we use a previously published statistical model (7) to evaluate whether anthropogenic emissions of radiatively active gases, along with natural variables, can account for the 1999-2008 hiatus in warming. To do so, we compile information on anthropogenic and natural drivers of global surface temperature, use these data to estimate the statistical model through 1998, and use the model to simulate global surface temperature between 1999 and 2008. Results indicate that net anthropogenic forcing rises slower than previous decades because the cooling effects of sulfur emissions grow in tandem with the warming effects greenhouse gas concentrations. This slow-down, along with declining solar insolation and a change from El Nino to La Nina conditions, enables the model to simulate the lack of warming after 1998. These findings are not sensitive to a wide range of assumptions, including the time series used to measure temperature, the omission of black carbon and stratospheric water vapor, and uncertainty about anthropogenic sulfur emissions and its effect on radiative forcing (SI Appendix: Sections 2.4-7).
The costly interactions between humans and wildfires throughout California demonstrate the need to understand the relationships between them, especially in the face of a changing climate and expanding human communities. Although a number of statistical and process-based wildfire models exist for California, there is enormous uncertainty about the location and number of future fires, with previously published estimates of increases ranging from nine to fifty-three percent by the end of the century. Our goal is to assess the role of climate and anthropogenic influences on the state’s fire regimes from 1975 to 2050. We develop an empirical model that integrates estimates of biophysical indicators relevant to plant communities and anthropogenic influences at each forecast time step. Historically, we find that anthropogenic influences account for up to fifty percent of explanatory power in the model. We also find that the total area burned is likely to increase, with burned area expected to increase by 2.2 and 5.0 percent by 2050 under climatic bookends (PCM and GFDL climate models, respectively). Our two climate models show considerable agreement, but due to potential shifts in rainfall patterns, substantial uncertainty remains for the semiarid inland deserts and coastal areas of the south. Given the strength of human-related variables in some regions, however, it is clear that comprehensive projections of future fire activity should include both anthropogenic and biophysical influences. Previous findings of substantially increased numbers of fires and burned area for California may be tied to omitted variable bias from the exclusion of human influences. The omission of anthropogenic variables in our model would overstate the importance of climatic ones by at least 24%. As such, the failure to include anthropogenic effects in many models likely overstates the response of wildfire to climatic change.
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