Thesis (DPhil)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This study is informed by both the deficit/positivist and contextual/critical models for doing public understanding of science (PUS) research and seeks to investigate factors that influence the perceptions, beliefs and attitudes towards climate change in Malawi. Previous research on the public understanding of climate change conducted in the United States of America (USA) and Europe suggest that people‘s beliefs, perceptions and attitudes do influence support for both voluntary and policy initiatives to address climate change and adaption to it. However, it is equally important to understand the factors that influence public perceptions, beliefs and attitudes towards climate change. An investigation into these factors provides an understanding and appreciation of the contextual issues related to the public assimilation and renegotiation of climate change information, as well as the support or rejection of initiatives aimed at addressing climate change. Sub-Saharan African countries are most vulnerable to the effects of climate change because their national economies and populations depend on rain-fed agriculture. Malawi is no exception. The majority of the Malawian population (at least 85%) live in rural areas and depend on subsistence, rain-fed agriculture for their livelihood, and are therefore more vulnerable to climate change. Furthermore, Malawi‘s economy is agro-based (agriculture comprises about 36% of the Gross Domestic Product (GDP), 85% of exports earnings and 84% of total employment). On the basis of these facts, I hypothesised that the perceptions, beliefs and attitudes of Malawians towards climate change are influenced by a wide range of factors, including the impact of climate change on livelihoods. More specifically, I proposed that more rural inhabitants than urban residents were likely to agree that their livelihood has been negatively affected by climate change, and would also be more willing to take voluntary action to address climate change. Upon performing chi-square analyses of the responses, the results indicate that: (i) significantly more rural (91%) than urban inhabitants (51%) agree that their livelihood has been negatively affected by climate change, and (ii) significant higher proportions of the rural population have at some point taken voluntary action to address climate change Multinomial logistic regression models predicted the perceptions, beliefs and attitudes of Malawians towards climate change. The results show that location is the only predictor of whether an individual would agree that his/her livelihood has been negatively affected by climate change or not. Rural inhabitants are 6.5 times more likely than urban residents to agree that their livelihood has been negatively affected by climate change. Location is also a predictor of the belief that climate change and its impact is the will of God; the belief that the solution to climate change rests with God; and how certain or uncertain a person is regarding the effects of climate change. Binary logistic regression results show that location is also the strongest predictor of whether an individual would take a voluntary action to address climate change or not. Rural inhabitants are 2.3 times more likely than urban residents to take voluntary action to address climate change. Besides place of residence, other predictors of perceptions, beliefs and attitudes towards climate change are: level of education (predictor of three outcome variables, namely: how certain or uncertain a person is about the causes of climate change; whether an individual believes that climate change and its impact is the will of God or not; and whether an individual believes that the solution to the problem of climate change rests with God or not); environmental groups and institutions of learning as sources of information about climate change (predictors of how certain or uncertain a person is about the causes of climate change, and whether a person believes that climate change and its impact is the will of God or not, respectively); and the trustworthiness of village headmen as a source of information about climate change (predictor of whether an individual will believe that climate change and its impact is the will of God or not; and whether an individual will take personal initiative to address climate change). These findings affirm the hypothesis that the impact of climate change on livelihoods of Malawians living in rural locations influences their perceptions, beliefs and attitudes towards climate change. Additionally, the findings suggest that public education about climate change remains key to promoting understanding of climate change. The Government of Malawi and non-governmental organisations have to take up this challenge of educating the Malawian public about climate change, particularly those living in rural locations. However, public education of climate change in Malawi demands that we also take into account the contextual factors that influence Malawians‘ perceptions, beliefs and attitudes towards climate change. For future research, the study suggests that more research in Sub-Saharan Africa is warranted to unearth the contextual factors that influence the public understanding of climate change. / AFRIKAANSE OPSOMMING: Hierdie studie inkorporeer insigte uit onderskeidelik die tekortskietende/positiwistiese en kontekstuele/kritiese modelle rakende die openbare verstaan van wetenskapsnavorsing, in ‘n poging om die faktore wat die persepsies, oortuigings en houdings teenoor klimaatsverandering in Malawi beïnvloed te ondersoek. Vorige navorsing oor die openbare begrip van klimaatsverandering – wat in die Verenigde State van Amerika (VSA) en Europa uitgevoer is – dui daarop dat individuele persepsies, oortuigings en houdings ‘n invloed uitoefen op die ondersteuning vir beide vrywillige sowel as beleidsinisiatiewe in klimaatsverandering. Dit is egter van groot belang om die faktore wat openbare persepsies, oortuigings en houdings teenoor klimaatsverandering beïnvloed te verstaan. ʼn Ondersoek na hierdie faktore verskaf begrip sowel as waardering vir die kontekstuele kwessies wat verband hou met die openbare assimilasie en ―heronderhandeling‖ van inligting oor klimaatsverandering. So ‘n ondersoek dra ook by tot ‘n verduideliking waarom voorgestelde klimaatsveranderingsinisiatiewe òf verwerp òf ondersteun word. Lande in sub-Sahara Afrika, waaronder Malawi, is baie kwesbaar vir die gevolge van klimaatsverandering as gevolg van die aard van hul ekonomieë en die samelewing se afhanklikheid van nie-besproeiingslandbou. Die Malawiese bevolking is grotendeels landelik (ten minste 85%) en maak staat op nie-besproeiingsbestaansboerdery, wat hulle dus meer kwesbaar maak vir die gevolge van klimaatsverandering. Malawi se ekonomie is boonop landbou-gedrewe: landbou dra by tot ongeveer 36% van die BBP, tot 85% van inkomste uit uitvoere en tot 84% van totale indiensnemingsgetalle. Gegewe hierdie feite is my hipotese dat die persepsies, oortuigings en houdings van Malawiërs teenoor klimaatsverandering deur talle uiteenlopende faktore beïnvloed word, waaronder die impak van klimaatsverandering op hul daaglikse bestaan. Die hipotese suggereer verder dat meer landelike inwoners, in teenstelling tot stedelike inwoners, geneig sal wees om saam te stem dat hul bestaan negatief deur klimaatsverandering beïnvloed word, en derhalwe ook ‘n groter gewilligheid sal openbaar tot vrywillige optrede wat klimaatsverandering aanspreek. Chi-kwadraat analises wat op die opnameresponse uitgevoer is, dui daarop dat (i) meer landelike (91%) as stedelike (51%) inwoners saamstem dat hul bestaan negatief deur klimaatsverandering beïnvloed word en dat (ii) ʼn beduidende hoër persentasie landelike inwoners op een of ander stadium vrywillig teen klimaatsverandering opgetree het. Multinomiale logistiese-regressiemodelle is gebruik om die persepsies, oortuigings en houdings van Malawiërs teenoor klimaatsverandering te voorspel. Die resultate toon dat ligging die enigste betekenisvolle voorspeller is in die uitkoms of ʼn individu saamstem dat sy/haar bestaan negatief deur klimaatsverandering beïnvloed word of nie – dit is 6.5 keer meer waarskynlik dat landelike as stedelike inwoners sal saamstem dat hul bestaan negatief deur klimaatsverandering beïnvloed word. Ligging dien ook as ʼn betekenisvolle voorspeller in drie verdere uitkomste, naamlik die oortuiging dat klimaatsverandering en die impak daarvan die wil van God is, die oortuiging dat die oplossing vir klimaatsverandering by God berus en hoe seker of onseker ʼn individu van sy/haar oortuiging is met betrekking tot die gevolge van klimaatsverandering. Volgens ‘n binêre logistiese-regressieanalise is ligging ook die sterkste voorspeller of ʼn individu vrywillig sal optree om klimaatsverandering aan te spreek, al dan nie. Dit is 2.3 keer meer waarskynlik dat landelike inwoners, in teenstelling met stedelike inwoners, vrywillig sal optree om klimaatsverandering aan te spreek. Agesien van ligging het die volgende ook na vore getree as bykomende voorspellers van individue se persepsies, oortuigings en houdings teenoor klimaatsverandering: (i) vlak van opvoeding (voorspeller van drie uitkomste-veranderlikes: hoe seker of onseker ʼn persoon is oor die oorsake van klimaatsverandering; of ʼn persoon glo dat klimaatsverandering en die gevolglike impak die wil van God is al dan nie; en of ʼn individu glo dat die oplossing vir klimaatsverandering by God berus al dan nie), (ii) die twee bronne van inligting rondom klimaatsverandering, naamlik omgewingsgroepe en opvoedingsinstellings, wat dien as voorspellers van hoe seker of onseker ʼn individu is oor die oorsake van klimaatsverandering, en of ʼn persoon glo dat klimaatsverandering en die gevolglike impak die wil van God is of nie; en (iii) die geloofwaardigheid van stamhoofde as ʼn bron van inligting oor klimaatsverandering (voorspeller van of ʼn persoon sal glo dat klimaatsverandering en die gevolglike impak die wil van God is of nie en of ʼn individu persoonlike inisiatief aan die dag sal lê om klimaatsverandering aan te spreek). Die bevindinge van die studie bevestig die voorgestelde hipotese dat die impak van klimaatsverandering op die bestaan van Malawiërs wat in landelike gebiede woon, ook hul persepsies, oortuigings en houdings teenoor klimaatsverandering beïnvloed. ʼn Verdere bevinding is dat openbare opvoeding oor klimaatsverandering ʼn sleutelrol in die bevordering van die begrip oor klimaatsverandering speel. Die uitdaging rus op die skouers van die Malawiese regering en nie-regeringsorganisasies om die Malawiese publiek, en veral diegene wat in landelike gebiede woon, oor klimaatsverandering op te voed. Die voorgestelde organisasies sal hulself egter nie van hul taak kan kwyt indien daar nie ʼn begrip is van die faktore wat Malawiërs se persepsies, oortuigings en houdings teenoor klimaatsverandering beïnvloed nie. Die studie beveel aan dat meer navorsing in sub-Sahara Afrika onderneem behoort te word om kontekstuele faktore wat die openbare begrip van klimaatsverandering beïnvloed, te identifiseer.

The Antarctic climate has undergone complex changes over the last fifty years, driven largely by stratospheric ozone depletion. By the end of this century, under the current trajectory of anthropogenic emissions, the climate of Antarctica is projected to be significantly wetter, warmer and prone to the collapse of ice shelves and loss of sea ice cover. The overarching aim of this thesis is to increase our understanding of recent and projected Antarctic climate change and its drivers. We also investigate the potential global implications of these changes and show that the effects will not be limited to the southern high latitudes. In the first half, we investigate the drivers of Antarctic climate change over the observational period. Specifically, we study the influence of the stratosphere on the southern high latitude surface climate, through stratosphere-troposphere dynamic coupling as well as stratospheric ozone depletion. We examine the impact of these on the Amundsen Sea Low, a key circulation feature near West Antarctica. We demonstrate using reanalysis that stratospheric heat flux extremes are linked to high latitude tropospheric anomalies in the Amundsen Sea region. During extreme negative (positive) events there is a westward (eastward) shift of the Amundsen Sea Low, a warming (cooling) and increase (decrease) of geopotential height over the Amundsen and Bellingshausen Seas. We find that most CMIP5 models are not able to capture this relationship. Next, we demonstrate that, since 1965, stratospheric ozone depletion has acted to deepen the Amundsen Sea Low in austral summer by 1 hPa per decade. This result was consistent across two different comprehensive climate models, each with very different model physics and climate sensitivity. It must be noted that the ozone depletion signal on the Amundsen Sea Low is small compared to the internal climate variability in this region. Using ensembles of model integrations and analysing them over the full period of ozone depletion (which started a couple of decades before the satellite era) is necessary to detect a robust signal. In the second half, we investigate the effects of future Antarctic climate change, specifically the effects of projected sea ice loss over the coming century. Climate model simulations are used to isolate the effect of end-of-the-century Antarctic sea ice loss which is compared and contrasted with the effects of projected Arctic sea ice loss. We first study the effects of projected Antarctic sea ice loss used atmosphere-only simulations. As for the Arctic, results indicated that Antarctic sea ice loss will act to shift the tropospheric jet equatorward, an internal negative feedback to the poleward shift associated with increased greenhouse gases. Antarctic sea ice loss is shown to have an important effect throughout the year whereas Arctic sea ice loss will have more seasonally varying impacts. Building upon these results we the use the same climate model but in a fully coupled setup to study the effects of projected Antarctic sea ice loss on the climate system. We show that both Arctic and Antarctic sea ice loss will have important global effects, causing a ‘mini global warming’ signal. The tropical response to Antarctic sea ice loss is shown to be remarkably similar to that of Arctic sea ice loss, with enhanced warming in the Eastern Tropical Pacific and increased precipitation throughout much of the equatorial Pacific. These results highlight how intimately coupled the Antarctic climate is to the rest of the climate system.

A research report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science by Coursework and Research Report. Johannesburg 2014. / Climate change is an issue of global significance resulting in trans-boundary environmental and socio-economic impacts. South Africa is involved in the international efforts to address climate change, has accepted the findings of the Intergovernmental Panel on Climate Change (IPCC) Assessment Report and developed a National Climate Change Response Policy, listing the impacts of climate change on the sustainable development in South Africa. The main causes of climate change are Greenhouse Gases (GHGs), which have been emitted from different development activities over temporal and spatial scales. In order to reduce the emissions of GHGs and protect proposed development projects from climate change impacts, climate change mitigation and adaptation measures should be incorporated into Environmental Impact Assessment (EIA). This research aimed to describe climate change incorporation into the EIA legal regime and practice in South Africa, based on climate change impacts on sustainable development and the role of EIA in considering climate change. The methodology involved reviewing EIA regulations and related legislation, EIA case studies from Gauteng province conducted between 2010 and 2013, key informant interviews with Environmental Assessment Practitioners (EAPs), and discussion on the linkedin group of the International Association for Impact Assessment of South Africa (IAIAsa). The study concluded that climate change is not explicitly incorporated into the EIA regime, but it is implied in the EIA regulations and related legislation. Largely as a result of the lack of climate change incorporation in the EIA legal regime, climate change is not adequately considered in the EIA practice. In order to support the contribution of EIA to sustainable development in South Africa, It is recommended that climate change should be incorporated into EIA regulations in the next amendment of NEMA. This can be done through including listed activities that require climate change incorporation into the EIA based on type of an activity and/or specific receiving environments. It is also suggested that EIA guidelines for climate change consideration be developed. Further recommendations include supporting the role that Strategic Environmental Assessment (SEA) and Environmental Management Framework (EMF) play, in conjunction with the EIA, in considering climate change; increasing the availability of accurate, local climate change data and modelling technology; developing staff capacity and awareness about climate change, and building EAP’s ability to incorporate climate change in the EIA through the support of government related authorities and associations such as IAIAsa and EAPSA. Key words: climate change, EIA, mitigation, adaptation, EIA legal regime, EIA practice.

Extreme temperatures, heat waves, heavy rainfall events, drought, and extreme air pollution events have adverse effects on human health, infrastructure, agriculture and economies. The frequency, magnitude and duration of these events are expected to change in the future in response to increasing greenhouse gases and decreasing aerosols, but future climate projections are uncertain. A significant portion of this uncertainty arises from uncertainty in the effects of aerosol forcing: to what extent were the effects from greenhouse gases masked by aerosol forcing over the historical observational period, and how much will decreases in aerosol forcing influence regional and global climate over the remainder of the 21st century? The observed frequency and intensity of extreme heat and precipitation events have increased in the U.S. over the latter half of the 20th century. Using aerosol only (AER) and greenhouse gas only (GHG) simulations from 1860 to 2005 in the GFDL CM3 chemistry-climate model, I parse apart the competing influences of aerosols and greenhouse gases on these extreme events. I find that small changes in extremes in the “all forcing” simulations reflect cancellations between the effects of increasing anthropogenic aerosols and greenhouse gases. In AER, extreme high temperatures and the number of days with temperatures above the 90th percentile decline over most of the U.S., while in GHG high temperature extremes increase over most of the U.S. The spatial response patterns in AER and GHG are significantly anti-correlated, suggesting a preferred regional mode of response that is largely independent of the type of forcing. Extreme precipitation over the eastern U.S. decreases in AER, particularly in winter, and increases over the eastern and central U.S. in GHG, particularly in spring. Over the 21st century under the RCP8.5 emissions scenario, the patterns of extreme temperature and precipitation change associated with greenhouse gas forcing dominate. The temperature response pattern in AER and GHG is characterized by strong responses over the western U.S. and weak or opposite signed responses over the southeast U.S., raising the question of whether the observed U.S. “warming hole” could have a forced component. To address this question, I systematically examine observed seasonal temperature trends over all time periods of at least 10 years during 1901-2015. In the northeast and southern U.S., significant summertime cooling occurs from the early 1950s to the mid 1970s, which I partially attribute to increasing anthropogenic aerosol emissions (median fraction of the observed temperature trends explained is 0.69 and 0.17, respectively). In winter, the northeast and southern U.S. cool significantly from the early 1950s to the early 1990s, which I attribute to long-term phase changes in the North Atlantic Oscillation and the Pacific Decadal Oscillation. Rather than being a single phenomenon stemming from a single cause, both the warming hole and its dominant drivers vary by season, region, and time period. Finally, I examine historical and projected future changes in atmospheric stagnation. Stagnation, which is characterized by weak winds and an absence of precipitation, is a meteorological contributor to heat waves, extreme pollution, and drought. Using CM3, I show that regional stagnation trends over the historical period (1860-2005) are driven by changes in anthropogenic aerosol emissions, rather than rising greenhouse gases. In the northeastern and central United States, aerosol-induced changes in surface and upper level winds produce significant decreases in the number of stagnant summer days, while decreasing precipitation in the southeast US increases the number of stagnant summer days. Outside of the U.S., significant drying over eastern China in response to rising aerosol emissions contributed to increased stagnation during 1860-2005. Additionally, this region was found to be particularly sensitive to changes in local aerosol emissions, indicating that decreasing Chinese emissions in efforts to improve air quality will also decrease stagnation. In Europe, I find a dipole response pattern during the historical period wherein stagnation decreases over southern Europe and increases over northern Europe in response to global increases in aerosol emissions. In the future, declining aerosol emissions will likely lead to a reversal of the historical stagnation trends, with increasing greenhouse gases again playing a secondary role. Aerosols have a significant effect on a number of societally important extreme events, including heat waves, intense rainfall events, drought, and stagnation. Further, uncertainty in the strength of aerosol masking of historical greenhouse gas forcing is a significant source of spread in future climate projections. Quantifying these aerosol effects is therefore critical for our ability to accurately project and prepare for future changes in extreme events.

The complex interplay between climate change, demographics and socioeconomic conditions is transforming the global environmental health landscape. In the aftermath of recent heat waves around the world, especially the 2003 heat wave in Europe, heat is being recognized as an emerging public health issue worldwide, particularly in urban areas. This work explores the historical and future heat-related mortality in New York City, from the beginning of the 20th until the end of the 21st century. New York City is among the largest cities in the world and has been a thriving metropolis over the entire period covered by this study. The unique makeup of the city makes it particularly suitable for studying the impacts of heat over an extended period of time. The presented work encompasses multiple domains of knowledge and illustrates the necessity for applying highly interdisciplinary approaches in addressing the emerging challenges of our time. The background chapter provides an overview of methodological approaches and findings from previous studies with direct relevance to the specific aims of this work. Chapter I is focused on characterizing the impacts of heat on daily mortality since 1900. Here, heat effects are presented in a historical context and changes over time are analyzed and discussed. Chapter II provides a comparative assessment of recent historical and heat impacts until 2100 in New York City, Boston and Philadelphia. This analysis illustrates the differences and similarities between heat impacts in New York City and the other two major urban areas in the U.S. Northeast. Chapter III provides a more comprehensive assessment of future heat-related mortality in New York City under a number of adaptation, climate change and demographic scenarios. The concluding chapter presents a summary of findings and recommendations for future research.

The complex interplay between climate change, demographics and socioeconomic conditions is transforming the global environmental health landscape. In the aftermath of recent heat waves around the world, especially the 2003 heat wave in Europe, heat is being recognized as an emerging public health issue worldwide, particularly in urban areas. This work explores the historical and future heat-related mortality in New York City, from the beginning of the 20th until the end of the 21st century. New York City is among the largest cities in the world and has been a thriving metropolis over the entire period covered by this study. The unique makeup of the city makes it particularly suitable for studying the impacts of heat over an extended period of time. The presented work encompasses multiple domains of knowledge and illustrates the necessity for applying highly interdisciplinary approaches in addressing the emerging challenges of our time. The background chapter provides an overview of methodological approaches and findings from previous studies with direct relevance to the specific aims of this work. Chapter I is focused on characterizing the impacts of heat on daily mortality since 1900. Here, heat effects are presented in a historical context and changes over time are analyzed and discussed. Chapter II provides a comparative assessment of recent historical and heat impacts until 2100 in New York City, Boston and Philadelphia. This analysis illustrates the differences and similarities between heat impacts in New York City and the other two major urban areas in the U.S. Northeast. Chapter III provides a more comprehensive assessment of future heat-related mortality in New York City under a number of adaptation, climate change and demographic scenarios. The concluding chapter presents a summary of findings and recommendations for future research.

Climate change is a major environmental threat and likely one of the most important challenges of our time. In particular, climate extremes –such as heat waves– can have a significant negative effect on society. Yet, many impacts of climate change are poorly understood and binding international climate change agreements are notoriously hard to reach. This work deals with the economics of climate change in three separate essays. The first one introduces a new methodology to estimate the impacts of climate extremes on public health. The second utilizes this methodology to assess the impacts of several climate change scenarios on Europe. The third explores a way to increase cooperation on climate change mitigation policies through explicit communication of the uncertainty of future climate change impacts. In general, human mortality shows an oscillatory pattern on top of a nonlinear trend. It tends to be highest in winter and lowest in summer. The nonlinear trend follows changes in health policies, economic growth rates, and other institutional factors. The first essays shows that singular spectrum analysis can be used for the estimation of this base rate mortality and thus allows to isolate the impacts of climate extremes on human mortality. This methodology is an improvement over approaches based on fixed effects or classic spectral analysis. It makes it possible to extend climate impact analysis to regions and countries for which there are no detailed data from hospital records as only coarse monthly data on mortality are needed. The danger of climate change lies not necessarily in the shift in average temperatures, but more so the increase in frequency of extreme heat events. Yet, while heat waves become more common, cold spells become less frequent. As both types of extreme temperature events increase human morbidity and mortality, the net effect of this shift is unknown. The second essay finds that a scenario of moderate warming can have a positive net effect on some European countries, creating winners and losers. In contrast –severe warming as a result of failed climate change mitigation policies– affects all examined European countries in a negative way. There would be no winners, just losers. As a result of the uncertainty associated with it, climate change poses a different challenge than other social dilemma situations: The negative effects of climate change do not necessarily take place incrementally. While this should be a focal point for policy makers, the costs of climate change tend to be presented within an expected utility framework. Yet, the potential behavioral reactions to this uncertainty are –so far– neither explored nor accounted for in game-theoretic models of climate coalition building. The third essay finds that cooperation in a public goods game can be increased when the uncertainty is communicated explicitly. This means that uncertainty should not be hidden behind expected costs and benefits, but rather be acknowledged when the goal is to form a climate change mitigation agreement.

Shaped by countless influences from the atmosphere, biosphere, hydrosphere, and anthroposphere acting across a wide spectrum of spatiotemporal scales, spatial variations in climate are ubiquitous. Meanwhile, the warming signal from anthropogenically elevated greenhouse-gas concentrations is emerging as an overriding determinant for more and more aspects of the climate system, extreme heat among them. In this dissertation, I explore the interaction of these two effects, and the implications of the patterns they create. A key finding is that rapid increases in extreme heat are already occurring, by some metrics having already doubled in the past 40 years, and further nonlinear increases are expected. Another is the strong dependence of extreme heat-humidity combinations on atmospheric moisture, creating subseasonal and interannual patterns dictated by the principal source of regional warm-season moisture — pre-monsoonal advection in some cases, local evapotranspiration in others. These relationships lead to the demonstrated potential for improvements in predictive power, on the basis of sea-surface temperatures and other canonical modes of large-scale climate variability. In contrast to this overall confidence in current temporal patterns and long-term projections, I show that extreme heat at small spatial scales is much more poorly characterized in gridded products, and that these biases are especially acute along coastlines. While summer daytime temperature differences between the shoreline of the Northeast U.S. and locations 60 km inland are often 5°C or more, I find that recent high-resolution downscaled Earth-system models typically represent no more than 25% of this difference. Across the globe, ERA-Interim reanalysis similarly underestimates extreme humid heat by >3°C, a highly significant margin given the large sensitivity of health and economic impacts to marginal changes in the most extreme conditions. I find that these biases propagate into projections, and their importance is also amplified by the large populations living in the affected areas. Rapid mean warming is pushing the climate system to more and more frequently include extreme heat-humidity combinations beyond that which the human species has likely ever experienced. Such conditions, which had not been previously reported in weather-station data, are described in detail and some of the associated characteristics examined. Several channels of analysis highlight that these events are driven primarily by rising sea-surface temperatures in shallow subtropical gulfs, and the subsequent impingement of marine air on the coastline. Given the severity of potential impacts on infrastructure and agriculture, and the size of the populations exposed, this result underscores that major research and adaptation efforts are needed to avoid calamitous outcomes from the emergence of extreme heat-humidity combinations too severe to tolerate in the absence of artificial cooling. This dissertation discusses strategies for advancing knowledge of extreme heat’s natural variations and its behavior under climate change, in order to design metrics, models, methodologies, and presentation types such that essential findings are translated into tangible action in the most effective way possible. Sustained and integrated efforts are necessary to transition to a climate-system management style encompassing more foresight than the effectively unplanned experiment which has been pursued so far, and which has already exacerbated extreme heat events so much.

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