Climatic changes

Extant literature has struggled to identify definitive purpose for shareholder proposals, finding them to depend on their context. Progressively, climate change has gathered interest at annual meetings where shareholders present proposals related to the subject. The literature builds expectations for the role of obsolescence, regulation and other forms of activism to motivate innovation with respect to these proposals. The literature also establishes how diversification can serve as a defense. I test the impact that shareholder proposals have on the information environment and on the corporate behaviors of innovation and diversification. I find that capital markets are responsive to proposal pressures and that there are improvements in the information environment. I find that firms in receipt of shareholder proposals related to climate change innovate and diversify more. I find wealth enhancements for these corporate behaviors spurred by climate-related proposals. While definitive statements on causality may elude, my results suggest that shareholder proposals have real effects.

Baseflow is the portion of the streamflow that is sustained between precipitation events, fed to streams by delayed pathways. Baseflow estimation and evaluation are two critical and essential tasks for water quality and quantity, drought management, water supply, and groundwater protection. In this research study, the influences of climate change and variability on baseflow derived from hundreds of watersheds in the continental United States are evaluated. Baseflows are estimated using streamflow data from these watersheds that are least affected by anthropogenic influences. In the initial phase of the study, an exhaustive evaluation of four different baseflow separation methods is carried out using streamflow data at several sites from the South Atlantic-Gulf region which includes a geographical region comprising of nine states in the southeastern U.S. Baseflows are estimated at different temporal scales and are used to assess the performances of different methods over a 44-year period starting from the year 1970 and the best method among these methods is selected for further analysis. Assessments of climate change influence on baseflows are then carried out using two nonparametric statistical trend tests (viz.,
Spearman’s Rho (SR) and Mann-Kendall (MK)). Trends in baseflows are evaluated at 574 sites located within the watersheds in the U.S. that are known to be least impacted by human influences. Trends were determined for annual maximum, mean, and median baseflows for the period 1970-2013. Spatially non-uniform trends and changes in characteristics of baseflows and strong influences of past precipitation events on the baseflow extremes were noted across the continental U.S. Some regions have shown decreasing baseflow trends and these are cause for concern and have severe implications for drought mitigation plans and low-flow management strategies in several watersheds in the U.S. In the final phase of the study influences of climate variability on baseflow manifested through different phases of individual and coupled oceanic and atmospheric oscillations are evaluated. Baseflows at 574 sites separated by temporal windows that coincide with two or more phases of different decadal, quasi-decadal and multi-year oscillations (viz., Pacific decadal oscillation (PDO), North Atlantic oscillation (NAO), Atlantic multidecadal oscillation (AMO), and El Niño-southern oscillation (ENSO)) are evaluated for statistically significant changes using nonparametric statistical hypothesis tests. Results from the study indicate that unlike climate change influences, climate variability effects are noted only in few specific physiographic regions of the U.S. This study documents an exhaustive and comprehensive assessment of changes in baseflows due to changing climate and results from this work can aid in short- and long-term management of low flows at a regional level that supports sustainable aquatic environment and handle droughts effectively.

Severe weather events that accompany climatic changes have been the main focus of many studies that want to highlight the large processes that surround us every day. These studies are based on years of data collection and other studies to help aid their pursuits. An area of major focus is identifying proxies and supplementary materials that help refine climate records of the geologic past. This study aims to identify reliable proxies for obtaining a record of severe weather events. The research consists of studying a coral species Pseudodiploria strigosa colonies with the goal to document, interpret, and describe the burial and re-exposure of massive coral colonies by severe storm or hurricane events, as recorded in coral growth patterns through density patterns and the analysis of CT-scanned coral specimens.

Nitrogen (N) and phosphorus (P) senescent leaf retention, as a measure of
resorption, and the subsequent decay of senescent leaves, roots and rhizomes were
examined for the dominant tropical seagrass species, Thalassia testudinum, across a
nutrient gradient in Florida Bay. Leaf nutrient loss while still attached to the short
shoot, from both resorption and decay, was highest at the nutrient-rich (88% P; 51%
N) compared to nutrient-poor site ( 49% P; 25% N). High nutrient loss rates by
attached leaves (0.37-2.5 mg P and 6.5-34 mg N m^-2 d^-1) represented significant
recycling (46-87% P and 17-48% N) oftotal estimated external nutrient loads to the
bay. In contrast, senescent leaf, rhizome and root nutrient loss rates were > 1 00-fold
lower than intact leaves. In tropical /subtropical estuaries dominated by T testudinum,
seagrasses may be acting as nutrient pumps, translocating high porewater nutrients to
the overlying waters and promoting phytoplankton blooms in the bay.

Thermal remote sensing is a powerful tool for measuring the spatial variability of
evapotranspiration due to the cooling effect of vaporization. The residual method is a
popular technique which calculates evapotranspiration by subtracting sensible heat from
available energy. Estimating sensible heat requires aerodynamic surface temperature
which is difficult to retrieve accurately. Methods such as SEBAL/METRIC correct for
this problem by calibrating the relationship between sensible heat and retrieved surface
temperature. Disadvantage of these calibrations are 1) user must manually identify
extremely dry and wet pixels in image 2) each calibration is only applicable over limited
spatial extent. Producing larger maps is operationally limited due to time required to
manually calibrate multiple spatial extents over multiple days. This dissertation develops
techniques which automatically detect dry and wet pixels. LANDSAT imagery is used
because it resolves dry pixels. Calibrations using 1) only dry pixels and 2) including wet
pixels are developed. Snapshots of retrieved evaporative fraction and actual evapotranspiration are compared to eddy covariance measurements for five study areas in
Florida: 1) Big Cypress 2) Disney Wilderness 3) Everglades 4) near Gainesville, FL. 5)
Kennedy Space Center. The sensitivity of evaporative fraction to temperature, available
energy, roughness length and wind speed is tested. A technique for temporally
interpolating evapotranspiration by fusing LANDSAT and MODIS is developed and
tested.
The automated algorithm is successful at detecting wet and dry pixels (if they
exist). Including wet pixels in calibration and assuming constant atmospheric
conductance significantly improved results for all but Big Cypress and Gainesville.
Evaporative fraction is not very sensitive to instantaneous available energy but it is
sensitive to temperature when wet pixels are included because temperature is required for
estimating wet pixel evapotranspiration. Data fusion techniques only slightly
outperformed linear interpolation. Eddy covariance comparison and temporal
interpolation produced acceptable bias error for most cases suggesting automated
calibration and interpolation could be used to predict monthly or annual ET. Maps
demonstrating spatial patterns of evapotranspiration at field scale were successfully
produced, but only for limited spatial extents. A framework has been established for
producing larger maps by creating a mosaic of smaller individual maps.

This study focuses on two main broad areas of active research on climate: climate variability and climate change and their implications on regional precipitation characteristics. All the analysis is carried out for a climate change-sensitive region, the state of Florida, USA. The focus of the climate variability analysis is to evaluate the influence of individual and coupled phases (cool and warm) of Atlantic multidecadal oscillation (AMO) and El Niäno southern oscillation (ENSO) on regional precipitation characteristics. The two oscillations in cool and warm phases modulate each other which have implications on flood control and water supply in the region. Extreme precipitation indices, temporal distribution of rainfall within extreme storm events, dry and wet spell transitions and antecedent conditions preceding extremes are evaluated. Kernel density estimates using Gaussian kernel for distribution-free comparative analysis and bootstrap sampling-based confidence intervals are used to compare warm and cool phases of different lengths. Depth-duration-frequency (DDF) curves are also developed using generalized extreme value (GEV) distributions characterizing the extremes. ... This study also introduces new approaches to optimally select the predictor variables which help in modeling regional precipitation and further provides a mechanism to select an optimum spatial resolution to downscale the precipitation projections. New methods for correcting the biases in monthly downscaled precipitation projections are proposed, developed and evaluated in this study. The methods include bias corrections in an optimization framework using various objective functions, hybrid methods based on universal function approximation and new variants.

This thesis focuses on evaluation of joint occurrence of extreme precipitation and streamflow events at several hydrologic structures in South Florida. An analysis of twelve years storm events and their corresponding peak streamflow events during wet and dry season including annual peaks considering two seasons was performed first. Dependence analysis using time series data of precipitation and streamflow was carried out next. The analysis included use of storm events with different temporal lags from the time of occurrence of peak streamflow events. Bi-variate joint probability was found to be appropriate to analyze the joint occurrence of events. Evaluation of joint exceedence probabilities under two phases of Atlantic multidecadal oscillation (AMO) influencing south Florida was also evaluated. All methodologies are evaluated for application using observations at several structures in the case study region to provide advances and valuable insights on joint extremes of precipitation and streamflows.

Increasing sea levels have the potential to place important portions of the infrastructure we rely on every day at risk. The transportation infrastructure relies on roads, airports, and seaports to move people, services, and goods around in an ever connected global economy. Any disturbances of the transportation modes have reverberating effects throughout the entire economic spectrum. The effects include delays, alterations of routes, and possible changes in the origin and destinations of services and goods. The purpose of this project is to develop an improved methodology for a sea level rise scenario vulnerability assessment model. This new model uses the groundwater elevation as a limiting factor for soil storage capacity in determining previously underestimated areas of vulnerability. The hope is that early identification of vulnerability will allow planners and government officials an opportunity to identify and either remediate or create alternative solutions for vulnerable land areas before high consequence impacts are felt.

Significant changes in climate and their impacts are now visible in various places around the globe and are expected to become more evident in the coming decades. For each increase in temperature, there are environmental and societal consequences. It has important implications for existing water resources systems as well as for future water resources planning and management. Water accounting (identifying, quantifying and reporting information of water flow in a system) is the first step towards formulating productive and sustainable water management strategies in a region. Thus, water balance models could be an empowering tool for water resource managers to prepare for and mitigate the effects of climate change on their local hydrologic resources. This thesis offers an insight into how such a tool can be used to assess and predict future stream flow trends in an effort to mitigate or manage any potential effects.