Lawrence C. Hamilton

Statistics with Stata 5

Introduction to STATA data graphs frequency distributions and univariate statistics T tests, anova, and nonparametric comparisons bivariate regression multiple regression regression diagnostics fitting curves robust regression logistics regression principal components and factor analysis list of some Stata commands Monte Carlo and Bootstrap Methods.

Arctic system on trajectory to new, seasonally ice‐free state

The Arctic system is moving toward a new state that falls outside the envelope of glacialinterglacial fl uctuations that prevailed during recent Earth history. This future Arctic is likely to have dramatically less permanent ice than exists at present. At the present rate of change, a summer ice-free Arctic Ocean within a century is a real possibility, a state not witnessed for at least a million years. The change appears to be driven largely by feedback-enhanced global climate warming, and there seem to be few, if any, processes or feedbacks within the Arctic system that are capable of altering the trajectory toward this “super interglacial” state.

Predicting September sea ice: Ensemble skill of the SEARCH Sea Ice Outlook 2008–2013

Since 2008, the Study of Environmental Arctic Change Sea Ice Outlook has solicited predictions of September sea-ice extent from the Arctic research community. Individuals and teams employ a variety of modeling, statistical, and heuristic approaches to make these predictions. Viewed as monthly ensembles each with one or two dozen individual predictions, they display a bimodal pattern of success. In years when observed ice extent is near its trend, the median predictions tend to be accurate. In years when the observed extent is anomalous, the median and most individual predictions are less accurate. Statistical analysis suggests that year-to-year variability, rather than methods, dominate the variation in ensemble prediction success. Furthermore, ensemble predictions do not improve as the season evolves. We consider the role of initial ice, atmosphere and ocean conditions, and summer storms and weather in contributing to the challenge of sea-ice prediction.

Blowin' in the Wind: Short-Term Weather and Belief in Anthropogenic Climate Change

AbstractA series of polls provides new tests for how weather influences public beliefs about climate change. Statewide data from 5000 random-sample telephone interviews conducted on 99 days over 2.5 yr (2010–12) are merged with temperature and precipitation indicators derived from U.S. Historical Climatology Network (USHCN) station records. The surveys carry a question designed around scientific consensus statements that climate change is happening now, caused mainly by human activities. Alternatively, respondents can state that climate change is not happening, or that it is happening but mainly for natural reasons. Belief that humans are changing the climate is predicted by temperature anomalies on the interview day and the previous day, controlling for season, survey, and individual characteristics. Temperature effects concentrate among one subgroup, however: individuals who identify themselves as independent, rather than aligned with a political party. Interviewed on unseasonably warm days, independent...

Dynamics of Terrorism

There are important controversies over the dynamics of terrorism which have not yet been formally addressed in quantitative social research. We suggest a class of stochastic models for social contagion which may help to shed light on these controversies. Empirical estimates of model parameters were obtained from data on international terrorism in 16 countries over 1968–78. We find some evidence suggesting that the tendency of acts of terrorism to incite further violence is more easily reversed in less democratic, poorer, and less well-educated societies. This suggests that reversal of a terrorism ‘epidemic’ is more likely under conditions facilitating repression rather than reform, and that more open societies face particular difficulties in responding to terrorism effectively.

Who cares about polar regions? Results from a survey of U.S. public opinion

What do members of the general public know about polar regions, and how much do they care? Who knows or cares? This paper explores data from the General Social Survey (GSS), which in 2006 questioned a representative sample of more than 1800 U.S. adults about their knowledge and opinions concerning polar regions. The polar survey items were modeled on long-running GSS assessments of general science knowledge and opinions, recently summarized in the U.S. National Science Boards report Science and Engineering Indicators 2008. Polar knowledge proves to be limited but certainly not absent among survey respondents. Polar knowledge, general science knowledge, and education—together with individual background characteristics (age, sex, income)—predict policy-relevant opinions. Political orientation filters the impacts of education, and also shows consistent, significant effects across all the polar opinion questions. These 2006 GSS polar results will provide a baseline for comparison when the questions are repeated on a 2010 survey, after the International Polar Year concludes.

Self-Reported and Actual Savings in a Water Conservation Campaign

Data from a survey questionnaire and from water utility billing records are used to compare self-reported and actual water savings for 471 households during a conservation campaign. Self-reports are only weakly related to actual changes in water consumption. Errors are widespread, and not wholly random: The accuracy of self-reports increases with household socioeconomic status and with the extent of conservation behavior. The large and nonrandom error component makes self-reports questionable as a proxy for objective measures of overall water savings in conservation research. Because knowledge about water use is both generally low and related to conservation behavior, informational feedback may be a particularly effective strategy for increasing conservation. The effectiveness of this feedback may increase with social class, however.

Warming winters and New Hampshire’s lost ski areas: An integrated case study

New Hampshire’s mountains and winter climate support a ski industry that contributes substantially to the state economy. Through more than 70 years of history, this industry has adapted and changed with its host society. The climate itself has changed during this period too, in ways that influenced the ski industry’s development. During the 20th century, New Hampshire’s mean winter temperature warmed about 2.1° C (3.8° F). Much of that change occurred since 1970. The mult‐decadal variations in New Hampshire winters follow global temperature trends. Snowfall exhibits a downward trend, strongest in southern New Hampshire, and also correlates with the North Atlantic Oscillation. Many small ski areas opened during the early years while winters were cold and snowy. As winters warmed, areas in southern or lowelevation locations faced a critical disadvantage. Under pressure from both climate and competition, the number of small ski areas leveled off and then fell steeply after 1970. The number of larger, chairliftoperating ski areas began falling too after 1980. Aprolonged warming period increased the importance of geographic advantages, and also of capital investment in snowmaking, grooming and economic diversification. The consolidation trend continues today. Most of the surviving ski areas are located in the northern mountains. Elsewhere around the state, one can find the remains of “lost” ski areas in places that now rarely have snow suitable for downhill skiing. This case study demonstrates a general approach for conducting integrated empirical research on the human dimensions of climate change.

Social Change, Ecology and Climate in 20th-Century Greenland

Two great transitions, from seal hunting to codfishing, then from cod fishing to shrimp, affectedpopulation centers of southwest Greenland during the20th century. These economic transitionsreflected large-scale shifts in the underlying marineecosystems, driven by interactions between climate andhuman resource use. The combination of climaticvariation and fishing pressure, for example, provedfatal to west Greenlands cod fishery. We examine thehistory of these transitions, using data down to thelevel of individual municipalities. At this level,the uneven social consequences of environmental changeshow clearly: some places gained, while others lost. Developments in 20th-century Greenland resemblepatterns of human-environment interactions in themedieval Norse settlements, suggesting some generalpropositions relevant to the human dimensions ofclimatic change.

Public knowledge and concern about polar-region warming

In 2006 and 2010, before and after the International Polar Year, the General Social Survey asked cross-sections of the US public for their knowledge and opinions about polar regions. The opinion items sought respondents’ levels of concern about global warming in polar regions, and whether they favored opening Antarctica for development or reserving it for science. Polar knowledge scores show significant improvement from 2006 to 2010, while general science literacy scores and opinions remain largely unchanged. Regression of concern and Antarctic items on background characteristics, ideology, education and the two knowledge tests finds that ideology and knowledge have the most consistent effects. Conservative ideology negatively predicts all six concern items and supports for reserving the Antarctic. Polar knowledge exhibits a positive effect on most of the concern items and on support for reserving the Antarctic. General science knowledge has mainly positive effects on concern and Antarctic opinions as well, but its effects are moderated by ideology. These findings support two contrasting but not mutually exclusive views about the role of information: that more science information generally leads to greater concern about environmental changes, or greater support for science; but also that some informed but strongly ideological respondents acquire information selectively in ways that reinforce their existing beliefs.