Mounting research on alpine treeline advance suggests that global and regional temperatures do not completely explain changes in treeline elevation and distribution. Rather, micrometeorological feedbacks may play an important role in treeline advance by increasing local temperatures. On Pikes Peak, the comparison of a transition zone microclimate at treeline to an adjacent rockslide microclimate at the same elevation showed that the transition zone microclimate heats more quickly and to a higher maximum temperature than the rockslide. Observed differential heating is particularly prevalent in the near-surface soil temperature, an important location for seedling establishment and growth. During the June observation period, daytime temperature maximums in the transition zone soil were 7C warmer on average than in the rockslide. Local warming at the treeline’s leading edge suggests that the presence of trees increases soil heat flux through a variety of mechanisms. Canopy warming, varying soil moisture, and sheltering are each considered independently as possible causes of differential heating. First, I investigate the possibility that heat captured in the canopy warms the transition zone microclimate. However, this theory is unsupported by data showing daytime canopy transpiration and cooling, and infrared photos revealing that the canopy is significantly cooler than the rockslide during the day. Second, I explore whether higher soil moisture in the transition zone is responsible for differential heating via increased conduction. However, soil moistures are actually lower in the treeline microclimate, suggesting that low soil moisture may be a characteristic of warming rather than its cause. Third, I look at the idea that trees shelter the microclimate from wind and hence reduce heat loss. While sheltering effects show some relationship with differential heating, there is no consistent correlation between high wind and differential heating. While this analysis does not offer a clear cause of differential warming, a better understanding of the treeline system is gained, and suggestions are made for how and where to look for warming feedbacks in the future. Thus, while results are inconclusive, warming feedbacks at treeline that increase soil temperatures during the critical growing season should be further considered as factors in treeline advance.
Many general connections have been made between apocalyptic language and the rhetoric of crisis in climate change discourse. However, this study aims to thoroughly examine the rhetorical and narrative elements shared by both the historically religious apocalyptic genre and contemporary climate literature. These elements are generally grouped within the temporal structure and narrative of human destiny, the claims to authoritative knowledge and power, and the identification of evil opposed to the righteous cause. When employed, these themes of apocalyptic discourse individually and collectively convey a sense of crisis of the certain impending catastrophe of authoritative power over the cause of evil in the world. Therefore, this paper argues that through the apocalyptic topoi of time, authority, and evil, the books An Inconvenient Truth by Al Gore, Eaarth by Bill McKibben, and the novel Oryx and Crake by Margaret Atwood exemplify the employment of apocalyptic rhetoric in climate literature, which works to both reflect and intensify a perceived sense of crisis surrounding the issue of climate change.
Throughout the past century, there has been a global shift in climate. Temperatures have been rising, and while precipitation has been fluctuating, it has exhibited not obvious trends. This change in climate has led to global treeline advancement, and has presented ecological, economic, and social implications. Two of the most relevant implications, especially within the context of the western United States, are changing ecosystem dynamics and water yields. Therefore this study aims to explore the effects of climate change at treeline throughout the Colorado Rockies, with the objective to use simple meteorological data to explain and predict radial tree growth. Data was collected at ten individual mountains in five mountain ranges throughout the state. The subsequent dendrochronologies for each mountain were correlated with time, local and regional meteorology, and the other nine sites. The correlation between sites was compared to the distance between sites. Chronologies were also compared to regional wind and storm patterns. Ultimately, no significant climatic trends appeared to influence individual tree growth on a regional scale throughout the Colorado Rockies. In some sites, such as those bordering the western Colorado deserts, increasing precipitation led to increased radial growth. At a small number of sites in the Front Range and the Sawatch Range, increased summer and annual temperatures led to increased radial growth as well. The remaining sites showed no connection between radial tree growth and simple local and regional meteorological data. The dendrochronologies between most mountains were significantly correlated; the correlations ranged from 0.93 to 0.25, with most of the sites correlated at 0.6 and above. Surprisingly, the correlation coefficients between sites did not respond to the distance between mountains in a statistically significant way. Based on an analysis between site correlations, three groups emerged with inter-site correlation at 0.7 and above: west of the Continental Divide, Front Range and Central Rockies, and along the Continental Divide. In general, these groups showed a southwest to northeast orientation. Storm patterns that flow from the southwest to the northeast throughout the state act as the central variable in correlating chronologies between sites. Conclusively this study does not support the hypotheses that claim climate significantly affects radial growth, but instead provides important information that can be used to further understand the implications of climate on treeline dynamics in the Colorado Rockies.
Climate change concern remains remarkably low in the United States despite extensive evidence of its current and future negative impacts on the planet. Previous research suggests this is because people perceive climate change as a distant risk that will not affect them personally. This study investigates whether experiencing an extreme adverse weather event such as the 2012-2016 California drought reduces the psychological distance of the issue, and leads those who experienced the weather event to have higher levels of concern about climate change. Using data from a survey administered to California, Oregon, and Washington residents in February 2017, regression analysis was performed to evaluate the hypotheses. It was expected that those living in California who had experienced the drought would express higher levels of concern over climate change than those in Oregon or Washington who had not experienced the drought. Additionally, it was hypothesized that those who experienced the drought would also be more likely to support environmental policy aimed at mitigating climate change than those with no drought experience. The first model in the study showed that drought experience on its own does not lead to higher levels of climate change concern. It was found, however, that experiencing climate change to a lesser degree, such as observing warming temperatures, does increase concern. The second model showed that those who express higher levels of concern over climate change are much more likely to support environmental policy.