Abstract: Economists and environmental policymakers have recently begun advocating a bottom-up approach to climate change mitigation, focusing on reduction targets for groups of nations, rather than large scale global policies. We advance this discussion by conducting a rigorous empirical analysis of the global distribution of carbon emissions along several important dimensions: groupings, polarization, mobility, and volatility. In contrast to previous work, our empirical analysis is both comprehensive and data-driven. We discuss how robust empirical evidence may aid policymakers in forging a heterogeneous carbon abatement policy.

Abstract: The Atlantic Multidecadal Oscillation (AMO) affects climate variability in the North Atlantic basin and adjacent continents with potential societal impacts. Previous studies based on model simulations and short-term satellite retrievals hypothesized an important role for cloud radiative forcing in modulating the persistence of the AMO in the tropics, but this mechanism remains to be tested with long-term observational records. Here we analyze data sets that span multiple decades and present new observational evidence for a positive feedback between total cloud amount, sea surface temperature (SST), and atmospheric circulation that can strengthen the persistence and amplitude of the tropical branch of the AMO. In addition, we estimate cloud amount feedback from observations and quantify its impact on SST with idealized modeling experiments. From these experiments we conclude that cloud feedbacks can account for 10% to 31% of the observed SST anomalies associated with the AMO over the tropics.

Abstract: The global ocean contains a massive reservoir (66232PgC) of dissolved organic carbon (DOC), and its dynamics, particularly in the deepest zones, are only slowly being understood. DOC in the deep ocean is ubiquitously low in concentration (similar to 35 to 48 mu molkg(-1)) and aged (4000 to 6000years), persisting for multiple meridional overturning circulations. Deep waters relatively enriched in DOC form in the North Atlantic, migrate to the Southern Ocean to mix with waters from Antarctic shelves and the deep Pacific and Indian Oceans, in turn forming the voluminous waters of the Circumpolar Deep Water. Here we seek evidence for local (autochthonous) versus distant (allochthonous) processes in determining the distribution of DOC in the deep Southern Ocean. Prior analyses on DOC in the deep Southern Ocean have conflicted, describing both conservative and nonconservative traits: the deep DOC field has been reported as uniform in distribution, yet local inputs have been suggested as quantitatively important. We use multiple approaches (multiple linear regression, mass transport, and mass balance calculations) with data from Climate Variability and Predictability Repeat Hydrography sections to evaluate the system. We find that DOC concentrations in the deep Southern Ocean largely reflect the conservative mixing of the several deep waters entering the system from the north. Mass balance suggests that the relatively depleted DOC radiocarbon content in the deep Southern Ocean is a conserved property as well. These analyses advance our understanding of the controls on the DOC reservoir of the Southern Ocean.

Abstract: Knowledge of spatiotemporal variability of rainfall magnitude, pattern and trend is fundamental for understanding hydrological systems and runoff prediction for both gauged and ungauged catchments. These variables can be derived from rainfall-monitoring programmes with adequate spatial distribution and temporal coverage. However, rainfall-gauging stations in most developing countries are distributed sparsely. Remotely sensed rainfall datasets are becoming alternative rainfall data sources for larger area applications and are proven to have adequate spatiotemporal resolutions. Climate forecast system re-analysis (CFSR) is one such dataset provided by the National Center for Environmental Prediction (NCEP). This dataset captures the rainfall pattern in Ethiopia but with s magnitude bias of over- and underestimations. In this study, magnitude bias correction of the CFSR dataset with a linear scaling technique resulted in a rainfall grid of the country with ∼38 km spatial resolution of a 32 year (1979–2010) daily rainfall dataset. For the bias correction, observed annual rainfall from 930 and daily rainfall from 195 rain gauges were used. The study also attempted to understand the space and time variability of the rainfall through the construction of shape, magnitude and composite rainfall regimes for the entire country. The rainfall regimes of the country were developed using the fuzzy overlay technique with multi-indices of rainfall. The rainfall regimes address the frequency, duration, timing and magnitude variability of rainfall. The performance of the dataset generation and rainfall regime classification was evaluated using Nash–Sutcliffe Efficiency (NSE) and percent bias (PBIAS) values, which were found to be 0.8 and 1.3, respectively.

Abstract: The state of Florida will be faced in the coming years with significant challenges and
opportunities for managing water in a highly dynamic and changing climate. The impacts of
climate change on water resources management will have consequences for the economic
sustainability and growth of the state. A strong awareness of climate change impact issues and
potential adaptation strategies that could be implemented by the state will increase its resilience
over the long-term to uncertain climatic conditions and sea level rise. To that end, a series of
white papers have been prepared by State University System (SUS) of Florida Universities to
coalesce our understanding of realized and predicted climate change impacts with a focus on
various topics. The report presented herein addresses water resources and adaptation issues
across the state. The primary objectives of this report are: (1) to identify Florida’s water
resources and water-related infrastructure that are vulnerable to climate change; (2) show
demographics in the state that are vulnerable to climate change impacts with a focus on water
resources and sea level rise; and (3) highlight some of the alternative technologies currently
being used to solve water resource supply issues in the state that are likely to expand and be
challenged under various scenarios of climate change.
Florida is highly vulnerable to climate change as a result of its expansive shoreline, low
elevation and highly permeable aquifers, and the location of high population centers and
economic investments close to the coastline. Further, the state receives a high frequency of
tropical storm landings that are accompanied by tidal surges that compound the risks of sea level
rise. Because the state is highly vulnerable compared to other regions globally, Florida’s
academic, governmental and non-governmental institutions are developing adaptation strategies
and conducting research on climate change. In this white paper, we highlight climate change
issues relevant to water management, but also recognize the financial challenges to implement
adaptation measures to address climate change solutions. Implementing adaptation measures
will require an unprecedented level of resource leveraging and coordination among academic,
governmental, non-governmental, and private sector entities.