Larix gmelinii (Rupr.) Kuzen. (Dahurian larch) is an important arctic tree-line species in the northern boreal forests of Eurasia. The region’s climate is predicted to change dramatically over the next century, yet little is known about how this species will respond to secular changes in temperature and precipitation. To this end, a ring-width chronology from 25 cores from a stand of seven Dahurian larch trees growing in the Secrest Arboretum, northeastern Ohio, was developed to test the climatic sensitivity of the species in a more temperate climate. The chronology extends from 1931 to 2005 and correlation analysis with monthly precipitation and temperature records shows growth was most strongly limited by summer precipitation until recent decades when sensitivity has shifted to late spring precipitation. The results from this study serve as a contemporary analog to the future growth response of Dahurian larch under warmer and wetter growing conditions in the boreal and arctic regions of Eurasia.

A sustainable design guide has a huge potential to enhance the sustainability of the built environment. This thesis investigates the potentials of a sustainable residential design guide and develops a framework for its actualization in the three climatic regions in Nigeria. These regions are; Highland Climate Region (HCR), Tropical Savannah (TSC) and the Tropical Rainforest Climate Region (TRC). Given that Nigeria is the seventh most populous country in the world, and most populous in Africa, makes any statistical findings from Nigeria relevant to the rest of the world. This sub-Saharan country is also faced with a huge yearly housing shortage of over ten million units and yet little is known on the efforts and actions taken by Nigeria to ensure that expected new buildings are sustainably designed in line with the global concerns. A concurrent embedded strategy was used in the investigation processes which provided both primary and secondary data sources for this research. Tools for the investigation were; literature review, pilot study, questionnaires and interviews. A Cronbach’s Alpha coefficient value of 0.96 was achieved from the survey instrument used. The questionnaire had 283 participants and a total of 30 interviewees were interviewed. The quantitative data from the questionnaire survey were analysed using SPSS 20 software and the NVivo 10 software was used for the qualitative analysis. Findings suggested that the impacts of climate change are evident and significant across all three regions. However, temperature increase recorded a significant value of more than 0.000 significance (p) level at 0.88 across the three regions, an indication that temperature increase is common to all three climatic regions. On the other hand, flooding, desertification/drought and erosion are more prevalent in the HCR, TSC and TRC respectively. This research’s contributions to knowledge includes; identifying the climatic design parameters for each region and the development of a conceptual framework. Hence, this research is a pioneer study in the subject of climate change and buildings in Nigeria. The thesis concludes that, the framework would promote the production of sustainable residential buildings in Nigeria. Also, areas of future research were suggested to include; the use of New technologies, effective collaborations, policy formulation and testing of the framework.

Widespread droughts can have a significant impact on western United States streamflow, but the causes of these events are not fully understood. This dissertation examines streamflow from multiple western US basins and establishes the robust, leading modes of variability in interannual streamflow throughout the past century. I show that approximately 50% of this variability is associated with spatially widespread streamflow anomalies that are statistically independent from streamflow's response to the El Niño-Southern Oscillation (ENSO). The ENSO-teleconnection accounts for approximately 25% of the interannual variability in streamflow, across this network. These atmospheric circulation anomalies associated with the most spatially widespread variability are associated with the Aleutian low and the persistent coastal atmospheric ridge in the Pacific Northwest. I use a watershed segmentation algorithm to explicitly track the position and intensity of these features and compare their variability to the multi-basin streamflow variability. Results show that latitudinal shifts in the coastal atmospheric ridge are more strongly associated with streamflow's north-south dipole response to ENSO variability while more spatially widespread anomalies in streamflow most strongly relate to seasonal changes in the coastal ridge intensity. This likely reflects persistent coastal ridge blocking of cool-season precipitation into western US river basins. I utilize the 35 model runs of the Community Earth System Model Large Ensemble (CESMLE) to determine whether the model ensemble simulates the anomalously strong coastal ridges and extreme widespread wintertime precipitation anomalies found in the observation record. Though there is considerable bias in the CESMLE, the CESMLE runs simulate extremely widespread dry precipitation anomalies with a frequency of approximately one extreme event per century during the historical simulations (1920 - 2005). These extremely widespread dry events correspond significantly with anomalously intense coastal atmospheric ridges. The results from these three papers connect widespread interannual streamflow anomalies in the western US - and especially extremely widespread streamflow droughts - with semi-permanent atmospheric ridge anomalies near the coastal Pacific Northwest. This is important to western US water managers because these widespread events appear to have been a robust feature of the past century. The semi-permanent atmospheric features associated with these widespread dry streamflow anomalies are projected to change position significantly in the next century as a response to global climate change. This may change widespread streamflow anomaly characteristic in the western US, though my results do not show evidence of these changes within the instrument record of last century.

Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906-1999 average, the worst 15-year drought on record. At least one-sixth to one-half (average at one-third) of this loss is due to unprecedented temperatures (0.9 degrees C above the 1906-1999 average), confirming model-based analysis that continued warming will likely further reduce flows. Whereas it is virtually certain that warming will continue with additional emissions of greenhouse gases to the atmosphere, there has been no observed trend toward greater precipitation in the Colorado Basin, nor are climate models in agreement that there should be a trend. Moreover, there is a significant risk of decadal and multidecadal drought in the coming century, indicating that any increase in mean precipitation will likely be offset during periods of prolonged drought. Recently published estimates of Colorado River flow sensitivity to temperature combined with a large number of recent climate model-based temperature projections indicate that continued business-as-usual warming will drive temperature-induced declines in river flow, conservatively -20% by midcentury and -35% by end-century, with support for losses exceeding -30% at midcentury and -55% at end-century. Precipitation increases may moderate these declines somewhat, but to date no such increases are evident and there is no model agreement on future precipitation changes. These results, combined with the increasing likelihood of prolonged drought in the river basin, suggest that future climate change impacts on the Colorado River flows will be much more serious than currently assumed, especially if substantial reductions in greenhouse gas emissions do not occur. Plain Language Summary Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906-1999 average, the worst 15-year drought on record. Approximately one-third of the flow loss is due to high temperatures now common in the basin, a result of human caused climate change. Previous comparable droughts were caused by a lack of precipitation, not high temperatures. As temperatures increase in the 21st century due to continued human emissions of greenhouse gasses, additional temperature-induced flow losses will occur. These losses may exceed 20% at mid-century and 35% at end-century. Additional precipitation may reduce these temperature-induced losses somewhat, but to date no precipitation increases have been noted and climate models do not agree that such increases will occur. These results suggest that future climate change impacts on the Colorado River will be greater than currently assumed. Reductions in greenhouse gas emissions will lead to lower future temperatures and hence less flow loss.

By the end of 2016 surveillance and reconnaissance satellites will have been monitoring Arctic-wide sea ice conditions for decades. Situated at the boundary between atmosphere and ocean, Arctic sea ice retreat has been one of the most conspicuous indication of climate change, especially in the two most recent decades. The 2001 annual minimum extent of Arctic sea ice marks the last year above the 1981 -- 2012 long-term average extent. Ever since then only lower than average Arctic sea ice has been observed at the end of each summer's melt season. For more than a century climate scientists have postulated that the darkening of the Arctic due to retreating sea ice and therefore more exposed open ocean would be the consequence of global warming. In the first decade of the 2000s the human influence on that warming in the Arctic was indeed detected in observations and attributed to increasing atmospheric greenhouse-gas concentrations. In this study we direct our attention to a potential offsetting effect from other anthropogenic (OANT) forcing agents, mainly aerosols, that has potentially out masked a fraction of greenhouse-gas induced warming by a combined cooling effect. We acknowledge that multiple sources of uncertainty exist in our method, in particular in the observed records of Arctic sea ice and corresponding simulations from climate models. No formal detection and attribution (DA) analysis has yet been carried out to try to detect the combined cooling effect from aerosols in observations of Arctic sea ice extent. We use three publicly available observational data sets of Arctic sea ice and climate simulations from eight models of the Coupled Model Intercomparison Project Phase 5 (CMIP5). In our detection and attribution study observations are regressed on model-derived climate response pattern, or fingerprints, under all known historical (ALL), greenhouse-gas only (GHG) and known natural-only (NAT) forcing factors using an optimal fingerprinting method. We estimate regression coefficients (scaling factors) for each forcing group that scale the fingerprints to best match the observed record. From the scaled ALL, GHG and NAT fingerprints we calculate the relative contribution of the observed sea ice decline attributable to OANT forcing agent. Based on our DA results we show that the simulated climate response patterns to changes in GHG, OANT and NAT forcing are detected in the observed records of September Arctic sea ice extent for the 1953 to 2012 period. / Graduate

Tropospheric ozone is one of the six criteria pollutants regulated by the United States Environmental Protection Agency under the Clean Air Act and has been linked with several adverse health effects, including mortality. Due to the strong dependence on weather conditions, ozone may be sensitive to climate change and there is great interest in studying the potential effect of climate change on ozone, and how this change may affect public health. In this paper we develop a Bayesian spatial model to predict ozone under different meteorological conditions, and use this model to study spatial and temporal trends and to forecast ozone concentrations under different climate scenarios. We develop a spatial quantile regression model that does not assume normality and allows the covariates to affect the entire conditional distribution, rather than just the mean. The conditional distribution is allowed to vary from site-to-site and is smoothed with a spatial prior. For extremely large datasets our model is computationally infeasible, and we develop an approximate method. We apply the approximate version of our model to summer ozone from 1997-2005 in the Eastern U.S., and use deterministic climate models to project ozone under future climate conditions. Our analysis suggests that holding all other factors fixed, an increase in daily average temperature will lead to the largest increase in ozone in the Industrial Midwest and Northeast. / Dissertation

This thesis provides a critical review of the Transition movement, a grassroots response to peak oil and climate change, co-founded by this author. It focuses on two key aspects of the Transition approach, resilience and economic relocalisation, with the aim of analysing whether and how they can be implemented in a locality based on the Transition approach, and assessing what socio-economic and community-related structures would be necessary to implement such a process. The focus of the research is Totnes, Devon, which because of its status as the UK’s first Transition initiative and the longer history of various initiatives to promote local resilience, offers a valuable case study of attempts to practically implement resilience and localisation. A variety of research methods were employed, including surveys, focus groups, oral history and in-depth interviews, as well less conventional public participation methods such as Open Space and World Café. The first major finding was that Transition Town Totnes (TTT) has become a significant organisation in the town, with a high level of popular support. It was also found that the obstacles to resilience and relocalisation lie not, as was hypothesised, in a lack of skills or an absence of community cohesion, but in issues of governance and the need for increased social entrepreneurship. It was found that what researchers call the ‘Value Action Gap’ (i.e. the gap between people’s declared sympathies and intentions and their actions) exists in Totnes as much as anywhere else, but that some of TTT’s projects, such as ‘Transition Together’, are working imaginatively to overcome this and to reduce emissions. From this evidence is it concluded that Transition’s approach towards relocalisation and reducing carbon emissions can be argued to be effective in, generating engagement and initiating new enterprises. Like other ‘green’ initiatives, it struggles to engage those from more disadvantaged backgrounds, but some of its initiatives are showing promise for overcoming this. Its primary contribution is in suggesting a redefining of resilience, not as a state of preparedness for disaster, but as a desired characteristic of a sustainable society. A more resilient community, it is argued, would be one more in control of its food and energy production, as well as being one that enables inward financial investment. It also argues that the government focus on ‘localism’, the devolving of political power to the local level, ought to be expanded to include ‘localisation’, the strengthening of local production to meet local needs, a shift which would financially benefit local communities. It argues that the key challenge for Transition initiatives such as TTT is going to be scaling up from being ‘niche’ organisations to become economically viable organisations with a broad appeal and engagement, and also articulates the need for ‘Resilience Indicators’ which would allow communities to measure the degree to which their levels of resilience are increasing.

Potential impacts of climate change on grain sorghum (Sorghum bicolor) productivity were investigated using the CERES-sorghum model in the Decision Support System for Agrotechnology Transfer v4.5. The model was first calibrated for a sorghum cultivar grown in a free air CO2 enrichment experiment at the University of Arizona, Maricopa, Arizona, USA in 1998. The model was then validated with an independent dataset collected in 1999. The simulated grain yield, growth, and soil water of sorghum for the both years were in statistical agreement with the corresponding measurements, respectively. Neither simulated nor measured yields responded to elevated CO2, but both were sensitive to water supply. The validated model was then applied to simulate possible effects of climate change on sorghum grain yield and water use efficiency in western North America for the years 2080-2100. The projected CO2 fertilizer effect on grain yield was dominated by the adverse effect of projected temperature increases. Therefore, temperature appears to be a dominant driver of the global climate change influencing future sorghum productivity. These results suggest that an increase in water demand for sorghum production should be anticipated in a future high-CO2 world.

Understanding how structure and function change across environmental gradients is a fundamental goal of ecology, with important applications in a changing world. In this dissertation, I explore how environmental variations in temperature and precipitation affect three-dimensional canopy structure, and how this, in turn, affects forest function. Characterising how climatic variations affect forest structure and function is particularly important in tropical forests, which are globally important carbon stores that have already shown vulnerability to climate change. The future of tropical forest carbon stocks is highly uncertain, with plant physiological responses representing the largest source of model uncertainties. As such, my dissertation research comprises empirical investigations into how tropical forests will respond to high temperatures and drought. Firstly, I examine tropical forest response to high temperature by conducting a comparison of natural forest sites and a tropical forest mesocosm using eddy-covariance data. I present evidence that high temperature declines in tropical forest photosynthesis are not due to direct temperature effects (i.e., that cause damage to the photosynthetic machinery), but instead are predominantly due to indirect temperature effects that result from concurrent increases in vapour pressure deficit (VPD). While both mechanisms reduce photosynthesis, the impact of increased VPD under future climate may be partly mitigated by enhanced water-use efficiency associated with rising atmospheric CO2 concentrations, suggesting that tropical forests may have opportunities for resilience in the face of global warming. The second part of my dissertation research examines how tropical forest canopy structure responds to seasonal dry periods and anomalous droughts on seasonal and interannual timescales, using data from ground-based LiDAR (Light Detection and Ranging). I show that total leaf area index (LAI) does not represent the seasonality of forest structure, since the upper and lower canopy levels exhibit divergent seasonal responses. The seasonal pattern of upper canopy LAI shows good agreement with the seasonal pattern of enhanced vegetation index (EVI) measured from satellites, suggesting that satellites are not capturing the response of the lower canopy. These results indicate that smaller trees are responding to seasonal water limitations and larger trees to light availability. I found that the response of canopy structure to anomalous (El Niño-induced) drought was similar to seasonal dry periods, but that the trends in LAI and vertical canopy structure were amplified. In particular, I document a delayed loss of LAI from the upper canopy following extreme drought, which supports the idea that while smaller trees may be more responsive to shorter, less severe dry periods, larger trees are more susceptible to prolonged or more severe droughts. Finally, I combine a long-term ground-based LiDAR dataset with tree inventory data in order to identify the mechanisms (i.e., changes in leaf area and/or woody biomass) of structural changes caused by droughts. I present evidence that loss of lower canopy LAI following an El Niño-induced drought was due to the mortality of small trees, not loss of leaf area, while an increase in LAI in the upper canopy predominantly resulted from plastic leaf area changes. If small trees are susceptible to drought-induced mortality and the incidence of droughts increases, this could prevent the recovery of tropical forests from drought-induced disturbances.

Shifting climatic regimes can increase or decrease the frequency of extreme hydrologic events (e.g., high and low streamflows) causing large societal and environmental impacts. The impacts are numerous and include human health and safety, the destruction of infrastructure, water resources, nutrient and sediment transport, and within stream ecological health. It is unclear how the hydrology of a given region will shift in response to climate change. This is especially the case in areas that are seasonally snow covered as the interplay of changing temperature, precipitation, and resulting snowpack can lead to an increased risk of flood or drought. This research aimed to understand the ways temperature and precipitation are changing using general circulation models and observed weather station data in the northeastern United States. With the knowledge that general circulation models do not accurately represent precipitation statistics and trends from the historical period, a large network of climate stations was utilized to further investigate shifts in precipitation. A hydrology model was utilized for further study of regional hydrology. The model used was the Regional Hydro-Ecologic Simulation System, which was calibrated to snow coverage and streamflow for a historical time period. The hydrology model was used to investigate the relationship of snow and streamflow in a changing climate. We characterized climate change and related impacts in the northeastern United States and estimated a decrease in snowfall of 50% and the number of days below freezing by 45 days by the end of the century. We also showed that precipitation is not only becoming more intense, but it is also more persistent -- a finding that may have significant hydrological implications including increased flood risk throughout the year. The 95th percentile of daily precipitation has increased by 0.5 mm per day per decade, while the probability of successive days with precipitation increased by 0.6 percent per decade. We also explored the role of snowpack in a changing climate. We found that temperature plays a larger role than precipitation in shifting hydrologic regime, because the warming-induced reduction of snowpack reduced the maximum flows more than the increasing precipitation increased the maximum flows. However, because of the increasing intensity and persistence of precipitation, instantaneous peak flows occurring outside of the snowmelt season will likely continue to increase during all times of the year. We shed light on the complexity of the modes of climate change and the interactions that increases in temperature and precipitation can have on the hydrology of a region.