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Remote Sensing of African Rainfall  

Tufa Dinku

Climate data support a suite of scientific and socioeconomic activities that can reinforce development gains and improve the lives of those most vulnerable to climate variability and change. Historical and current weather and climate observations are essential for many activities, including operational meteorology, identifying extreme events and assessing associated risks, developing climate-informed early warning systems, planning, and research. Rainfall is the most widely available and used climate variable. Thus, measurement of rainfall is crucial to society’s well-being. In general, measurements from ground meteorological stations managed by National Meteorological Agencies are the principal sources of rainfall data. The main strength of the station observations is that they are assumed to give the “true” measurements of rainfall. However, the distribution of the meteorological observation network over Africa is significantly inadequate, with declining numbers of stations and poor data quality. This problem is compounded by the fact that the distribution of existing stations is uneven, with most weather stations located in cities and towns along major roads. As a result, coverage tends to be worse in rural areas, where livelihoods may be most vulnerable to climate variability and change. This has resulted in critical gaps in the provision of climate services where it is needed the most. Space-based measurements from satellites are being used as a complement to or in place of ground observations. Satellite-derived precipitation estimates offer good spatial coverage and improved temporal and spatial resolution, as well as near-real-time availability. Moreover, a range of satellite rainfall products are freely available from many sources, and a couple of these products are available only for Africa. However, satellite rainfall products also suffer from many shortcomings that include accuracy, particularly at higher temporal resolutions; coarse spatial resolution; short time series; and temporal inhomogeneity due to varying inputs. This limits the use of the use these products for certain applications. Understanding satellite rainfall estimation errors is critical for deciding which products might be used for specific applications and requires rigorous evaluation of these products using ground observations. The challenge in Africa is lack of availability, accessibility, and quality of rain-gauge observations that could be used for this purpose. Despite these challenges, there have been some validation efforts over different parts of the continent. However, different and inconsistent approaches of validation have created challenges to using these evaluation results. A comprehensive validation of the main operational satellite products at a continental level is needed to overcome these challenges and make the best use of satellite rainfall products in different applications.


TV Meteorologists as Local Climate Change Educators  

Edward Maibach, Bernadette Woods Placky, Joe Witte, Keith Seitter, Ned Gardiner, Teresa Myers, Sean Sublette, and Heidi Cullen

Global climate change is influencing the weather in every region of the United States, often in harmful ways. Yet, like people in many countries, most Americans view climate change as a threat that is distant in space (i.e., not here), time (i.e., not now), and species (i.e., not us). To manage risk and avoid harm, it is imperative that the public, professionals, and policy-makers make decisions with an informed understanding of our changing climate. In the United States, broadcast meteorologists are ideally positioned to educate Americans about the current and projected impacts of climate change in their community. They have tremendous reach, are trusted sources of climate information, and are highly skilled science communicators. When our project began in 2009, we learned that many U.S.-based TV weathercasters were potentially interested in reporting on climate change, but few actually were, citing significant barriers including a lack of time to prepare and air stories, and lack of access to high-quality content that can be rapidly used in their broadcasts, social media, and community presentations. To test the premise that TV weathercasters can be effective climate educators—if supported with high-quality localized climate communication content—in 2010 George Mason University, Climate Central, and WLTX-TV (Columbia, SC) developed and pilot-tested Climate Matters, a series of short on-air (and online) segments about the local impacts of climate change, delivered by the station’s chief meteorologist. During the first year, more than a dozen stories aired. To formally evaluate Climate Matters, we conducted pre- and post-test surveys of local TV news viewers in Columbia. After one year, WLTX viewers had developed a more science-based understanding of climate change than viewers of other local news stations, confirming our premise that when TV weathercasters report on the local implications of climate change, their viewers learn. Through a series of expansions, including the addition of important new partners—the American Meteorological Society, National Aeronautical and Space Administration (NASA), National Oceanic and Atmospheric Administration (NOAA), and Yale University—Climate Matters has become a comprehensive nationwide climate communication resource program for American broadcast meteorologists. As of March 2016, 313 local weathercasters nationwide (at 202 stations in 111 media markets) are participating in the program, receiving new content on a weekly basis. Some leaders in the World Meteorological Organization are now promoting the concept of “TV weather presenters as climate change communicators,” and collaborative discussions are underway with Climate Central. In this article, we review the theoretical basis of the program, detail its development and national scale-up, and conclude with insights for how to develop climate communication initiatives for other professional communities of practice in the U.S. and other countries.


The Role of Local Governments in International Climate Policy  

Vanesa Castán Broto, Linda Westman, and Xira Ruiz Campillo

Local governments play an increasingly important role in international climate policy. Climate action follows existing trajectories of sustainable development action at the local level. The history of climate action in cities suggests a lot of potential for learning from previous sustainability experiences. Three aspects of climate change governance are important at the local level: the motivations for responding to climate change, the different responses deployed, and the city structures and networks representing cities in the global spheres. Current interest in climate change action at the local level follows three decades of local sustainability action. Because of engagement with environmental conflicts at the local level, environmental justice activists also influenced local climate action. Cities and settlements are exciting policy arenas with great potential to enable just transitions. However, the impacts of local government’s action at both the local level and internationally are not always evident. Cities have sought to address climate change through planning, harnessing co-benefits of climate action, and finding appropriate evaluation means. Solutions have also been developed through the insertion of cities in global circuits of knowledge production via transnational municipal networks (TMNs). Local government action can only be explained with reference to the international climate change regime. International policy events influence local government action, and local government action influences international discourses of climate action. A range of actors, from local governments to businesses, communities, and civil society, also play a role in addressing climate change. Still, they require autonomy and the resources to deliver mitigation and adaptation actions that local governments can mediate.


Climate and Simulation  

Gabriele Gramelsberger

Climate and simulation have become interwoven concepts during the past decades because, on the one hand, climate scientists shouldn’t experiment with real climate and, on the other hand, societies want to know how climate will change in the next decades. Both in-silico experiments for a better understanding of climatic processes as well as forecasts of possible futures can be achieved only by using climate models. The article investigates possibilities and problems of model-mediated knowledge for science and societies. It explores historically how climate became a subject of science and of simulation, what kind of infrastructure is required to apply models and simulations properly, and how model-mediated knowledge can be evaluated. In addition to an overview of the diversity and variety of models in climate science, the article focuses on quasiheuristic climate models, with an emphasis on atmospheric models.


Fear Appeals in Climate Change Communication  

Joseph P. Reser and Graham L. Bradley

There is a strong view among climate change researchers and communicators that the persuasive tactic of arousing fear in order to promote precautionary motivation and behavior is neither effective nor appropriate in the context of climate change communication and engagement. Yet the modest research evidence that exists with respect to the use of fear appeals in communicating climate change does not offer adequate empirical evidence—either for or against the efficacy of fear appeals in this context—nor would such evidence adequately address the issue of the appropriateness of fear appeals in climate change communication. Extensive research literatures addressing preparedness, prevention, and behavior change in the areas of public health, marketing, and risk communication generally nonetheless provide consistent empirical support for the qualified effectiveness of fear appeals in persuasive social influence communications and campaigns. It is also noteworthy that the language of climate change communication is typically that of “communication and engagement,” with little explicit reference to targeted social influence or behavior change, although this is clearly implied. Hence underlying and intertwined issues here are those of cogent arguments versus largely absent evidence, and effectiveness as distinct from appropriateness. These matters are enmeshed within the broader contours of the contested political, social, and environmental, issues status of climate change, which jostle for attention in a 24/7 media landscape of disturbing and frightening communications concerning the reality, nature, progression, and implications of global climate change. All of this is clearly a challenge for evaluation research attempting to examine the nature and effectiveness of fear appeals in the context of climate change communication, and for determining the appropriateness of designed fear appeals in climate change communications intended to both engage and influence individuals, communities, and “publics” with respect to the ongoing threat and risks of climate change. There is an urgent need to clearly and effectively communicate the full nature and implications of climate change, in the face of this profound risk and rapidly unfolding reality. All such communications are, inherently, frightening warning messages, quite apart from any intentional fear appeals. How then should we put these arguments, evidence, and challenges “on the table” in our considerations and recommendations for enhancing climate change communication—and addressing the daunting and existential implications of climate change?


Impact of Land–Atmosphere Interactions on Sahel Climate  

Yongkang Xue

The Sahel of Africa has been identified as having the strongest land–atmosphere (L/A) interactions on Earth. The Sahelian L/A interaction studies started in the late 1970s. However, due to controversies surrounding the early studies, in which only a single land parameter was considered in L/A interactions, the credibility of land-surface effects on the Sahel’s climate has long been challenged. Using general circulation models and regional climate models coupled with biogeophysical and dynamic vegetation models as well as applying analyses of satellite-derived data, field measurements, and assimilation data, the effects of land-surface processes on West African monsoon variability, which dominates the Sahel climate system at intraseasonal, seasonal, interannual, and decadal scales, as well as mesoscale, have been extensively investigated to realistically explore the Sahel L/A interaction: its effects and the mechanisms involved. The Sahel suffered the longest and most severe drought on the planet in the 20th century. The devastating environmental and socioeconomic consequences resulting from drought-induced famines in the Sahel have provided strong motivation for the scientific community and society to understand the causes of the drought and its impact. It was controversial and under debate whether the drought was a natural process, mainly induced by sea-surface temperature variability, or was affected by anthropogenic activities. Diagnostic and modeling studies of the sea-surface temperature have consistently demonstrated it exerts great influence on the Sahel climate system, but sea-surface temperature is unable to explain the full scope of the Sahel climate variability and the later 20th century’s drought. The effect of land-surface processes, especially land-cover and land-use change, on the drought have also been extensively investigated. The results with more realistic land-surface models suggest land processes are a first-order contributor to the Sahel climate and to its drought during the later 1960s to the 1980s, comparable to sea surface temperature effects. The issues that caused controversies in the early studies have been properly addressed in the studies with state-of-the-art models and available data. The mechanisms through which land processes affect the atmosphere are also elucidated in a number of studies. Land-surface processes not only affect vertical transfer of radiative fluxes and heat fluxes but also affect horizontal advections through their effect on the atmospheric heating rate and moisture flux convergence/divergence as well as horizontal temperature gradients.