In this review, with supplemental data analyses, we focus on the global and regional impacts of climate change on the frequency and intensity of fire weather (conditions conducive to fire ignition and spread) and the consequences for fire activity. We find that significant increases in fire weather have occurred in most world regions during recent decades due to climate change. Corresponding increases in the area burned by fires have been seen in some regions, most notably in mesic forests, however, in many regions fire is controlled by a range of other bioclimatic and human factors whose influences mediate or override those of fire weather. Weather conditions affecting vegetation growth and the build-up of fuels, the presence of human ignitions in regions that are not naturally fire-prone, and the fragmentation of fire-prone landscapes by agriculture are key examples of factors that can locally or regionally outweigh fire weather as controls on fire activity. Climate models project that fire weather will become increasingly frequent and intense under future warming, and at an increasing rate with each additional increment of warming. The outcomes for fire activity in future will depend on other regionally important factors that control fire ignition and spread. Existing fire models represent the controls on fire incompletely and so they reproduce observed patterns of fire with only limited success. Models also disagree on historical trends, leading to low confidence in their simulations of future fire activity. Various efforts to improve the representation of fire in models are underway and should yield greater capacity to predict the future of fire activity.

Land surface temperature (LST) is a crucial geophysical parameter related to surface energy and water balance of the land-atmosphere system. Satellite remote sensing provides the best way to measure LST and generate various LST products at regional and global scales. In this review, to facilitate the application of LST products in different fields, we first present the physical meaning of satellite-derived LST. Subsequently, we summarize recent advances in LST retrieval and validation methods, with a special focus on the state-of-the-art product collections, product accuracies and intercomparisons, and main problems in current LST products as well as their possible solutions. Additionally, we also review the major applications of LST products in agricultural drought monitoring, thermal environment monitoring, thermal anomaly monitoring, and climate change. Finally, we offer recommendations or perspectives to promote LST retrieval methods and their applications. This review will aid the user in gaining a thorough comprehensive understanding of satellite-derived LST products and promoting their appropriate applications.

Mountains cover a large part of the Earth's surface and harbor distinct ecosystems, hold most of snow and ice outside the polar regions, and provide water for billions of people. This research looks at recent climate changes in mountains and compares them with simultaneous changes in lowland regions using weather station data, large global data sets, and climate models. We examine changes since 1900, but also concentrate on the last 40 years since this is when many changes have started to accelerate. Nearly all regions of the globe are getting warmer. When we make local comparisons, mountain sites are usually warming faster than lower areas nearby. However, when we average data from all global mountains and compare them with those from all lowland areas, there is no significant difference. Rainfall/snowfall on the other hand is decreasing in some areas, and increasing in others. In nearly all cases the strongest increase is occurring in the lowland areas, with increases in the mountains being more subdued (if at all). One consequence of our findings is that stores of mountain snow and ice may decline even faster than previously assumed due to the combination of enhanced mountain warming and reduced elevation dependency of rainfall/snowfall.

Heat waves (HWs) are climate extremes of major societal concern whose frequency, intensity and duration will continue increasing during this century. This review synthesizes the physical understanding and the main scientific challenges. We discuss problems involved in HW definition, including the diversity of HW indicators, and the consideration of adaptive capabilities in a changing climate. We also review observed and projected trends and the associated atmospheric patterns in different areas of the globe, with special attention to the mechanisms and drivers responsible for HW occurrence. These act at different scales, from planetary to local, and include thermodynamic and dynamical processes. There is a limited and fragmentary understanding of the interactions among these processes on regional scales, and their changes under global warming. Process-based understanding will benefit HW forecasts at time horizons longer than weather predictions, attribution of HW trends and events to human activities, and regional climate projections. Improved technological capabilities, models of diverse complexity, or machine-learning techniques will help overcome these challenges.

River damming yields great social-economic benefits, but also causes significant eco-environmental impacts, particularly on fish. Dams block fish migration routes, alter hydrological and water temperature regimes, and modify channel morphology. These changes impact fish physical habitats and associated communities. Here, we synthesize the impacts of river damming on fish physical habitats, and review potential conservation measures that could be used to off-set or mitigate the impacts of dams on fish habitats, populations and communities.

The ocean plays a major role in the global carbon cycle and the storage of anthropogenic carbon dioxide. This key function of the ocean is related to the reaction of dissolved carbon dioxide with water to form bicarbonate (and minor quantities of carbonic acid and carbonate). Alkalinity, the excess of bases, governs the efficiency at which this occurs and provides buffering capacity toward acidification. Here we discuss ocean alkalinity, buffering, and biogeochemical processes and provide quantitative tools that may help to better understand the role of the ocean in carbon cycling during times of global change.