Understanding the impact of warming on organisms, communities and ecosystems is a central problem in ecology. Although species responses to warming are well documented, our ability to scale up to predict community and ecosystem properties is limited. Improving understanding of the mechanisms that link patterns and processes over multiple levels of organisation and across spatial and temporal scales promises to enhance our ability to predict whether the biosphere will exacerbate, or mitigate, climate warming. In this thesis, I combine ideas from metabolic theory with a variety of experimental approaches to further our understanding of how warming will impact photosynthesis and respiration across scales. Firstly, I show how phytoplankton can rapidly evolve increased thermal tolerance by downregulating rates of respiration more than photosynthesis. This increased carbon-use efficiency meant that evolved populations allocated more fixed carbon to growth. I then explore how constraints on individual physiology and community size structure influence phytoplankton community metabolism. Using metabolic theory, I link community primary production and respiration to the size- and temperature- dependence of individual physiology and the distribution of abundance and body size. Finally, I show that selection on photosynthetic traits within and across taxa dampens the effects of temperature on ecosystem-level gross primary production in a set of geothermal streams. Across the thermal-gradient, autotrophs from cold streams had higher photosynthetic rates than autotrophs from warm streams. At the ecosystem-level, the temperature-dependence of gross primary productivity was similar to that of organism-level photosynthesis. However, this was due to covariance between biomass and stream temperature; after accounting for the effects of biomass, gross primary productivity was independent of temperature. Collectively, this work emphasises the importance of ecological, evolutionary and physiological mechanisms that shape how metabolism responds to warming over multiple levels of organisation. Incorporating both the direct and indirect effects of warming on metabolism into predictions of the biosphere to climate futures should be considered a priority.

Land-surface models (LSMs) are crucial components of the Earth system models (ESMs) that are used to make coupled climate-carbon cycle projections for the 21st century. The Joint UK Land Environment Simulator (JULES) is the land-surface model used in the climate and weather forecast models of the UK Met Office. JULES is also extensively used offline as a land-surface impacts tool, forced with climatologies into the future. In this study, JULES is automatically differentiated with respect to JULES parameters using commercial software from FastOpt, resulting in an analytical gradient, or adjoint, of the model. Using this adjoint, the adJULES parameter estimation system has been developed to search for locally optimum parameters by calibrating against observations. This thesis describes adJULES in a data assimilation framework and demonstrates its ability to improve the model-data fit using eddy-covariance measurements of gross primary productivity (GPP) and latent heat (LE) fluxes. The adJULES system is extended to have the ability to calibrate over multiple sites simultaneously. This feature is used to define new optimised parameter values for the five plant functional types (PFTs) in JULES. The optimised PFT-specific parameters improve the performance of JULES at over 85% of the sites used in the study, at both the calibration and evaluation stages. The new improved parameters for JULES are presented along with the associated uncertainties for each parameter. The results of the calibrations are compared to structural changes and used in a cluster analysis in order to challenge the PFT definitions in JULES. This thesis concludes with simple sensitivity studies which assess how the calibration of JULES has affected the sensitivity of the model to CO2-induced climate change.

This thesis reveals the potential pitfalls of relying on the Internet to communicate serious environmental issues. This exploratory research examines the consequences of aspects of the information society focusing on the effects of the Internet upon three reactions to climate communication: public understanding, perception of risk and support for climate change mitigation. It examines the implications of the rise of the information society on young people’s (18-25 year olds) consumption of media and climate science information. The information society literature emerged before the Internet, but predicted the increasing access to information that has arisen in the past two decades and its significant impacts on society and communication. An analytical framework is developed focusing on the sharing of information and the consequences of both misleading information and competition for the user’s attention. To explore the impact of the Internet upon public perception of risks posed by and their understanding of climate change, this research uses a mixed methodological approach. The qualitative approach of focus groups has been selected to establish how young people use the Internet and whether they share and actively engage with climate change information online. A quantitative approach of the experimental method has critically examined the impact of junk information (climate sceptic material) and information overload (competition for users’ attention) on reactions to climate science. The original contribution to knowledge of this thesis was the key finding that the lack of engagement with climate science online poses a more serious issue than the risk of climate sceptic information being virally shared. Simply having the information accessible is not enough when there is so much competition for users’ attention and the ease with which they can filter out climate change information.

Floodplain fens represent an important component of the global carbon cycle through their role in carbon sequestration. Peat development depends upon rate of production exceeding rate of decomposition, yet there is little understanding of the effects of sea-level rise on these processes in lowland environments. This thesis investigates the impacts of projected sea-level rise from climate change on carbon storage in floodplain fens, using a combination of field, laboratory and simulation modelling techniques. A gradient of saline influence was determined for the Broads, UK, based on analysis of water chemistry and published water level data, allowing for the application of a space-for-time substitution technique. Increased water level had a positive effect on above-ground production of Phragmites australis (cav.) Trin. Ex Steud. (1841) - perhaps because water stress limits important photosynthetic processes. An increase in salinity had a negative effect on the growth of P. australis, probably due in part to osmotic stress. Previous management practice significantly impacted on production - as uncut vegetation became less productive with time. There was evidence to suggest that sea-level rise may lead to faster decay rates, but this will be partially offset by litter quality. Saline influenced sites had lower carbon accumulation potentials. Radiometric dating confirmed that these sites have lower carbon sequestration rates - probably as a result of increased mineral deposition in floodwaters. Carbon stock ranged between 33 and 144 kt C but depended greatly on peat depth and bulk density. Results from both field data and the model indicated that peat accretion in the Broads would not offset projected sea-level rise. Floodplain fen development under the influence of sea-level rise will be dependent on the majority of assimilate being allocated to above-ground vegetation.

The nitrogen cycle is one of the key macronutrient cycles that controls the distribution of life on Earth. The nitrogen cycle is composed of a series of distinct microbially mediated processes which may be affected differently with warming. Climate change is likely to affect all components of the nitrogen cycle. However, the extent to which each component will be affected and how this will alter interactions in natural systems is unknown. Here we used laboratory and field experiments to investigate the effect of warming on nitrogen cycling. We used a combination of pure cultures, in-situ measurements and laboratory manipulations of environmental samples to explore responses in freshwater and marine systems. In pure cultures of denitrifying bacteria, denitrification rates increased by 117-164%, with a 4oC temperature increase (11.5-15.5oC). In freshwater mesocosms, long term warming rates of sediment denitrification increased by 247%, with no significant thermal response of sediment nitrification within these systems. Marine sediment rates of denitrification and anammox increased by 4.69-16.23% and 3.71-35.39% respectively, depending on N substrate. Whereas a 3oC temperature increase in the water of the ETNP OMZ increased denitrification and anammox rates by 52.5% and 52.9% respectively, with no significant thermal response of nitrogen fixation in the OMZ surface waters. From this study, nitrogen removal processes increase with increasing temperature across systems but internal transformation and fixation of N show little to no thermal response. Further investigation into the causes of the observed variation in responses, such as substrate limitation and identification of microbes involved, will allow us to better understand and therefore better predict cross-system responses of the nitrogen cycle to global warming.

The Earth\'s atmosphere is warming due to a combination of natural effects and anthropic activities, which are directly related to the increment of greenhouse gas (GHG) emissions by burning fossil fuel. Brazil stands out in the world economic scenario as the main producer of ethanol, from sugar cane, considered a source of clean, renewable and economically viable energy. The expansion of this crop into pasture areas, in the Center-South region of Brazil, and the intensification in the production of this biofuel to supply the market have raised concerns about its sustainability. The agricultural is one of the main sectors responsible for the emission of GHG into the atmosphere, therefore, more studies are needed about how land use change (LUC) and production intensification, mainly due to the application of agricultural inputs rich in carbon and nitrogen, can affect GHG emissions. In the Center-South region of Brazil, the main LUC is composed of the succession native vegetation areas to pasture, and in sequence to sugarcane. Therefore, two studies were carried out aiming to determine soil GHG emissions under different land uses in the Center-South region of Brazil (Valparaíso-SP), as well as to characterize the emission factor of the main agricultural inputs in either sugarcane planting or ratoon areas. In the first study, three different land use areas were evaluated, composed of native vegetation, pasture and sugarcane. Among the land uses evaluated in this study, the soil under pasture exhibited the highest emission of carbon equivalents (CO2-eq), which was 41-fold higher than under native vegetation and 5.6-fold higher than under sugarcane. In the second study, two experiments were set up to determine the soil GHG emission fluxes after the application of sources of carbon and nitrogen during sugarcane cultivation. Experiment I: set up in a sugarcane planting area with application of ammonium nitrate, limestone and filter cake, in addition to a control treatment without application of any input. Experiment II: set up in a sugarcane ratoon area with application of vinasse and urea in the first year, and vinasse in the second year. In the first experiment, the soil tillage during the planting process produced a larger increase of soil GHG emissions when compared to the sugarcane ratoon area. Among the inputs applied to the cane plant, filter cake or ammonium nitrate produced the highest GHG emissions from the soil. On the other hand, in the area of sugarcane ratoon, the highest emissions were observed with the application of a combination of organic and mineral fertilizers (vinasse and urea), but with the application of only vinasse, the emission increment was less intense. The emission factors for C-CO2 and N-N2O reported by the IPCC are higher than those observed in this study, in the Center-South region of Brazil. The highest emission factor was observed for ammonium nitrate, with 0.13% for N-N2O in the rainy season. Thus, the expansion of sugarcane planted areas plays an important role in GHG emission. New studies on this contribution to GHG emissions are urgently needed in different regions around the world, in order to define measures to limit emissions and aiming at maintaining the sustainability of this biofuel / O aquecimento da Terra decorrente de atividades antrópicas, está diretamente relacionado ao aumento das emissões de gases de efeito estufa (GEE) por queima de combustíveis fósseis. O Brasil se destaca no cenário econômico mundial como o principal produtor de etanol, de cana-de-açúcar, considerado uma fonte de energia limpa, renovável e economicamente viável. A expansão desta cultura sobre áreas de pastagem, na região Centro-Sul do Brasil, e a intensificação da produção deste biocombustível, necessárias para suprir o mercado têm levantado preocupações sobre a sua sustentabilidade. O setor agrícola é uma das principais fases relacionadas à emissão de GEE na atmosfera, sendo necessário maior entendimento sobre como as mudanças de uso da terra (MUT) e intensificação de produção podem afetar as emissões GEE, principalmente após a aplicação no solo de insumos agrícolas ricos em carbono e nitrogênio. Na região Centro-Sul do Brasil, a principal MUT é composta pela sucessão de áreas de vegetação nativa- pastagem- cana-de-açúcar. Foram realizados dois estudos com o objetivo de determinar as emissões de GEE do solo em diferentes usos da terra em Valparaíso-SP, bem como caracterizar o fator de emissão dos principais insumos agrícolas utilizados em áreas de cana planta e cana soca. No primeiro estudo, foram avaliadas três áreas de uso da terra, compostas por vegetação nativa, pastagem e cana-de-açúcar. Entre os sistemas de usos da terra avaliados neste estudo, a pastagem apresentou a maior emissão de carbono equivalente (CO2-eq), no qual representou cerca de 41 vezes maior do que a vegetação nativa e 5,6 vezes maior do que a cana-de-açúcar. No segundo estudo, dois experimentos foram conduzidos simultaneamente para determinar os fluxos de emissões de gases do solo após a aplicação de fontes de carbono e nitrogênio durante diferentes fases do ciclo da cana-de-açúcar. Experimento I: realizado em uma área de plantio de cana-de-açúcar com aplicação de nitrato de amônio, calcário e torta de filtro, além de um tratamento controle sem aplicação de nenhum insumo. Experimento II: área de cana soca com aplicação de vinhaça e ureia no primeiro ano, e vinhaça no segundo ano. No primeiro experimento o revolvimento do solo no processo de plantio proporcionou as maiores emissões de GEE quando comparada a área de cana soca. Dentre os insumos aplicados na cana planta, a torta de filtro ou nitrato de amônio proporcionaram as maiores emissões de GEE do solo. Por outro lado, na área de cana soca, as maiores emissões foram verificadas quando houve a combinação de fertilizante orgânico e mineral (vinhaça e ureia), sendo que com a aplicação somente de vinhaça, o aumento das emissões foi menos intenso. Os fatores de emissão para C-CO2 e N-N2O relatados pelo IPCC ainda são maiores do que os observados neste estudo, realizado na região Centro-Sul do Brasil, no qual o maior fator de emissão foi observado para nitrato de amônio, com 0,13% para N-N2O, na estação chuvosa. A expansão das áreas plantadas de cana de açúcar tem importante papel na emissão de GEE, sendo necessários novos estudos sobre essa contribuição em distintas regiões de produção em todo o mundo, na busca de medidas menos emissoras, visando a sustentabilidade deste biocombustível

To determine the maximum carbon dioxide (CO2) emissions consistent with a given global warming threshold, the scientific community must robustly quantify what proportion of human emitted CO2 will be taken up by the terrestrial and marine carbon reservoirs. The North Atlantic Ocean is a region of intense uptake of atmospheric CO2. To assess how the North Atlantic CO2 sink has evolved over the past decades and understand the mechanisms involved in that uptake, observations and models are used. To appreciate the strengths and limitations of observation-based and modelled products, I explore the sources of uncertain- ties of two widely-used biogeochemical observational products (GLODAP and SOCAT), and carefully evaluate the latest generation of Earth System Models (ESMs) (i.e. the CMIP5 models) against these data. The lack of robust uncertainties on observation-based estimates of the North Atlantic CO2 uptake has so far limited the community’s ability to use observed trends to evaluate CO2 uptake behaviour simulated by the models. Here, by making use of the strengths of observation-based and modelled products, a novel gap-filling and uncertainty assessment method is developed to (1) robustly quantify the recent change in the basin-wide North Atlantic CO2 sink, and (2) evaluate simulations of the recent uptake in ESMs. Through the assessment of robust interpolation uncertainties on the annually-varying North Atlantic CO2 uptake and on the resulting trends over the period 1992-2014, I find that (1) the North Atlantic CO2 uptake increased at a rate of 0.081 ± 0.012 PgC/yr/decade from 1992- 2014, corresponding to an additional uptake of 2.2 PgC over this interval relative the flux in the 1992, and (2) state-of-the-art ESMs are consistently biased to lower trend values, with a mean that is about three times smaller than the observation-based trend, equating to an additional uptake of only 0.72 ± 0.40 PgC over the period 1992-2014. I further show that the inability of these models to capture the observed increase in CO2 uptake is due primarily to biases in modelled ocean biogeochemistry, which I explore through comparison with observations. Our current understanding of the ocean carbon-cycle, as synthesised by ESMs, cannot explain the recent behaviour of the North Atlantic CO2 sink. Current projections may therefore underestimate the contribution of the North Atlantic to mitigating increasing future atmospheric CO2 concentrations.

Climate change is one of the greatest threats to marine environments globally. Fisheries are being increasingly affected, with impacts not only to fish stocks but also the fishers who rely on marine resources for their livelihoods. This thesis uses an interdisciplinary, mixed methods approach to examine climate change impacts on fisheries within the under-studied, yet rapidly warming, south-west region of the UK. The thesis begins with a comprehensive review of the literature regarding climate change impacts on UK fisheries, the vulnerability of these fishery systems to future climate change and how climate change is perceived among fishers. In Chapter 2 a methodology is developed to standardise abundance data across multiple scientific fisheries survey datasets in order to facilitate future projections to be generated for the south-west UK region. Chapter 3 presents future projections of abundances and distributions for eight key commercial fish species under future warming scenarios until the end of the century. Results suggest that increasing temperatures and limitations of bathymetry are key drivers of species responses. Certain cold-water species including Atlantic cod (Gadus morhua L.) and anglerfish (Lophius piscatorius L.) will experience declines, while warm-water species such as red mullet (Mullus surmuletus L.) and John dory (Zeus faber L.) are expected to expand across the region. The uncertainty associated with future projections is explored through the use of 11 separate climate-ensembles. Chapter 4 uses information gained through interviews with fishers from a UK fishing port—Brixham—to explore how climate change is perceived and the factors influencing these perceptions. Findings suggest that while fishers generally felt that climate change posed a low risk to the future of their businesses and fisheries in the region, three groups emerged that showed differences in the extent to which they perceived climate change as a risk. A number of key factors were important in influencing these three groups. Chapter 5 develops further insight into fishers’ perceptions by exploring how fishers anticipate climate change to affect the physical environment, fishery resources, and their own practices in the future. Many fishers felt they would not need to alter their fishing practices in the future, with various reasons cited including personal preferences and perceived constraints to their adaptation. Fishers’ ability to adapt was further explored and three main groups were identified who differed according to a number of core dimensions of their adaptive capacity. Through adopting an interdisciplinary approach, the research in this thesis presents a number of new findings that have important implications for fisheries management and climate adaptation policies.

Weather – cold, wet, hot and windy – pervades life, material and social. So present and obvious as to provide a challenge for research, material though ephemeral too, weather breaks boundaries and refuses categorisation. While night becomes day, the cold season warms up over weeks and annual patterns are changing on a scale of years, practices in the face of weather transitions are themselves shifting. Based on ten months of fieldwork in the small village of Gau in the Pahari Indian Himalayas this thesis interrogates the saliencies and permeations of weather in people’s lives. It investigates how people intra-act (Barad 2007) with the weather, though practices, infrastructures and relationships with others. My approach argues for the validity of weather as a means by which to learn about socio-material lives. Pahari villagers live and act within the weather that moves around them. They are subject to, but also modify, their thermal environment. Through housing, clothing and tools such as the fire and the fan they affect the impact of the weather as it meets their bodies, but also daily patterns of movement are coloured by weather considerations. This work views weather in relation to health practices (such as refraining from working during the rain so as not to fall ill), for care of others (such as domestic bovines), for house-building and hospitable relationship-building among neighbours, for negotiation of landslide-fraught access roads to elsewhere and for understandings of pollution in the air. This focus on weather is intended to connect dots for people working on climate change, both within and beyond anthropology, and to contribute to discussions in areas including human-animal relations, health and illness and housing.

Carbon forestry projects have proliferated over last few years on the premise of cost efficient climate mitigation along with co-benefits of biodiversity conservation and livelihood improvement. Multilateral, bilateral, public and private sources have invested billions of dollars in the carbon forestry projects based on these claims. However, there is little empirical evidence to support the enthusiasm. This gap is further accentuated by the insufficient understanding of the governance challenges of these projects. These issues are social, political and ecological in nature and hence require a multidisciplinary political ecology framework for a comprehensive analysis. This thesis explores the multiple benefit claims and governance issues by analysing two forestry-based Clean Development Mechanism projects from India. One, in Haryana state focuses on private lands, the other in Himachal involves three different types of lands viz. community, public and private for plantation activities. This thesis examines the carbon, biodiversity and livelihood benefits of each project, and the governance challenges associated with them. I show that both projects have sequestered substantially less carbon than was originally predicted, which has serious implications for carbon revenues and hence economic viability of these projects. In the case of biodiversity, the results are mixed. In Haryana, the tree and herb biodiversity has improved in the project plots as compared to control plots, whereas shrub biodiversity has marginally declined. In case of Himachal project, biodiversity has declined at tree, shrub and herb levels. I have analysed livelihood impacts in terms of foregone crop, fodder and fuel wood benefits across small, medium and large category of farmers. Both the projects have adverse livelihood impacts on the participants, more so in Haryana because of the plantations on private lands. Although the project has adversely affected the livelihoods of all three categories of farmers, however it has affected small farmers the most due to their low incomes and risk-bearing capacities. Hence, these projects have serious equity implications. This thesis also explores the governance challenges of carbon forestry in terms of their interaction with existing policy mechanisms, especially the Forest Rights Act of 2006, which recognises the ownership and use rights of forest dependent communities comprehensively first time in independent India. The analysis suggests that there are various issues that carbon forestry projects pose for the implementation of the Act due to which civil society groups are opposing these projects. This thesis contributes to our understanding of the multiple benefit claims of carbon forestry projects with empirical evidence and a political ecological analysis. It shows that there is possibility of tradeoffs and many other scenarios in carbon forestry projects rather than just the projected 'win-win-win' outcomes. It contributes to the political economy literature by establishing that changes in global commodity markets can influence land use choices at local level, affecting the sustainability of such efforts. This thesis also advances the literature on governance of carbon forestry projects by reflecting on various policy and implementation level issues related to property rights, community institutions, transparency and accountability.