Abstract: Sea level has been steadily rising over the past century, predominantly due to anthropogenic climate change. The rate of sea level rise will keep increasing with continued global warming, and, even if temperatures are stabilized through the phasing out of greenhouse gas emissions, sea level is still expected to rise for centuries. This will affect coastal areas worldwide, and robust projections are needed to assess mitigation options and guide adaptation measures. Here we combine the equilibrium response of the main sea level rise contributions with their last century's observed contribution to constrain projections of future sea level rise. Our model is calibrated to a set of observations for each contribution, and the observational and climate uncertainties are combined to produce uncertainty ranges for 21st century sea level rise. We project anthropogenic sea level rise of 28-56 cm, 37-77 cm, and 57-131 cm in 2100 for the greenhouse gas concentration scenarios RCP26, RCP45, and RCP85, respectively. Our uncertainty ranges for total sea level rise overlap with the process-based estimates of the Intergovernmental Panel on Climate Change. The "constrained extrapolation" approach generalizes earlier global semiempirical models and may therefore lead to a better understanding of the discrepancies with process-based projections.

Abstract: Global mean surface temperatures are rising in response to anthropogenic greenhouse gas emissions. The magnitude of this warming at equilibrium for a given radiative forcing—referred to as specific equilibrium climate sensitivity ( S )—is still subject to uncertainties. We estimate global mean temperature variations and S using a 784,000-year-long field reconstruction of sea surface temperatures and a transient paleoclimate model simulation. Our results reveal that S is strongly dependent on the climate background state, with significantly larger values attained during warm phases. Using the Representative Concentration Pathway 8.5 for future greenhouse radiative forcing, we find that the range of paleo-based estimates of Earth’s future warming by 2100 CE overlaps with the upper range of climate simulations conducted as part of the Coupled Model Intercomparison Project Phase 5 (CMIP5). Furthermore, we find that within the 21st century, global mean temperatures will very likely exceed maximum levels reconstructed for the last 784,000 years. On the basis of temperature data from eight glacial cycles, our results provide an independent validation of the magnitude of current CMIP5 warming projections.

Abstract: Avoiding losses from climate change requires socially engaged research that explains what people value highly, how climate change imperils these phenomena, and strategies for embracing and managing grief

Abstract: Energy budget and climate model estimates of transient climate response match when model output is processed in the same manner as an observational record. Removal of observational sampling biases infers an estimate of 1.66 °C, consistent with model estimates.

Abstract: The response of climate to external forcing is known as climate sensitivity, and its estimates are calculated from historical observations. This study estimates the efficacy of individual forcings and revises climate sensitivities accordingly.

Abstract: Decision makers and consultants are particularly interested in “detailed” information on future climate to prepare adaptation strategies and adjust design criteria. Projections of future climate at local spatial scales and fine temporal resolutions are subject to the same uncertainties as those at the global scale but the partition among uncertainty sources (emission scenarios, climate models, and internal climate variability) remains largely unquantified. At the local scale the uncertainty of the mean and extremes of precipitation is shown to be irreducible for mid and end-of-century projections because it is almost entirely due to internal climate variability (stochasticity). Conversely, projected changes in mean air temperature and other meteorological variables can be largely constrained, even at local scales, if more accurate emission scenarios can be developed. The results were obtained by applying a comprehensive stochastic downscaling technique to climate model outputs for three exemplary locations. In contrast with earlier studies, the three sources of uncertainty are considered as dependent and, therefore, non-additive. The evidence of the predominant role of internal climate variability leaves little room for uncertainty reduction in precipitation projections; however, the inference is not necessarily negative, since the uncertainty of historic observations is almost as large as that for future projections with direct implications for climate change adaptation measures.

Abstract: This paper develops an economic analysis of climate change impacts in the global forest sector. It illustrates how potential future climate change impacts can be integrated into a dynamic forestry economics model using data from a global dynamic vegetation model, the MC2 model. The results suggest that climate change will cause forest outputs (such as timber) to increase by approximately 30% over the century. Aboveground forest carbon storage also is projected to increase, by approximately 26 Pg C by 2115, as a result of climate change, potentially providing an offset to emissions from other sectors. The effects of climate mitigation policies in the energy sector are then examined. When climate mitigation in the energy sector reduces warming, we project a smaller increase in forest outputs over the timeframe of the analysis, and we project a reduction in the sink capacity of forests of around 12 Pg C by 2115.

Abstract: An analysis of the regional climate response to cumulative CO2 emissions establishes a clear quantitative link between the total amount of CO2 emitted and the magnitude of local climate warming.

Abstract: Over the last decade, our understanding of climate sensitivity has improved considerably. The climate system shows variability on many timescales, is subject to non-stationary forcing and it is most likely out of equilibrium with the changes in the radiative forcing. Slow and fast feedbacks complicate the interpretation of geological records as feedback strengths vary over time. In the geological past, the forcing timescales were different than at present, suggesting that the response may have behaved differently. Do these insights constrain the climate sensitivity relevant for the present day? In this paper, we review the progress made in theoretical understanding of climate sensitivity and on the estimation of climate sensitivity from proxy records. Particular focus lies on the background state dependence of feedback processes and on the impact of tipping points on the climate system. We suggest how to further use palaeo data to advance our understanding of the currently ongoing climate change.

Abstract: There is a continually increasing demand for near-term (i.e., lead times up to a couple of decades) climate information. This demand is partly driven by the need to have robust forecasts and is partly driven by the need to assess how much of the ongoing climate change is due to natural variability and how much is due to anthropogenic increases in greenhouse gases or other external factors. Here we discuss results from a set of state-of-the-art climate model experiments in comparison with observational estimates that show that an assessment of predictability requires models that capture the variability of major oceanic fronts, which are, at best, poorly resolved and may even be absent in the near-term prediction of Intergovernmental Panel on Climate Change class models. This is the first time that air-sea interactions associated with resolved Gulf Stream sea surface temperature have been identified in the context of a state-of-the-art global coupled climate model with inferred near-term predictability.

Abstract: Information on the basics of climate change, including science, causes, impacts, and ways to address it.

Abstract: The reliability of model projections of greenhouse gas (GHG)-induced future climate change is often assessed based on models' ability to simulate the current climate, but there has been little evidence that connects the two. In fact, this practice has been questioned because the GHG-induced future climate change may involve additional physical processes that are not important for the current climate. Here I show that the spatial patterns of the GHG-induced future warming in the 21(st) century is highly correlated with the patterns of the year-to-year variations of surface air temperature for today's climate, with areas of larger variations during 1950-1979 having more GHG-induced warming in the 21(st) century in all climate models. Such a relationship also exists in other climate fields such as atmospheric water vapor, and it is evident in observed temperatures from 1950-2010. The results suggest that many physical processes may work similarly in producing the year-to-year climate variations in the current climate and the GHG-induced long-term changes in the 21(st) century in models and in the real world. They support the notion that models that simulate present-day climate variability better are likely to make more reliable predictions of future climate change.

Abstract: One of the key issues in international climate negotiations is the formulation of targets for emissions reduction for all countries based on the principle of “common but differentiated responsibilities”. This formulation depends primarily on the quantitative attribution of the responsibilities of developed and developing countries for historical climate change. Using the Commuity Earth System Model (CESM), we estimate the responsibilities of developed countries and developing countries for climatic change from 1850 to 2005 using their carbon dioxide, methane and nitrous oxide emissions. The results indicate that developed countries contribute approximately 53%–61%, and developing countries approximately 39%–47%, to the increase in global air temperature, upper oceanic warming, sea-ice reduction in the NH, and permafrost degradation. In addition, the spatial heterogeneity of these changes from 1850 to 2005 is primarily attributed to the emissions of greenhouse gases (GHGs) in developed countries. Although uncertainties remain in the climate model and the external forcings used, GHG emissions in developed countries are the major contributor to the observed climate system changes in the 20th century.

Abstract: Evidence-Based Climate Science: Data Opposing CO2 Emissions as the Primary Source of Global Warming, Second Edition, includes updated data related to the causes of global climate change from experts in meteorology, geology, atmospheric physics, solar physics, geophysics, climatology, and computer modeling. This book objectively gathers and analyzes scientific data concerning patterns of past climate changes, influences of changes in ocean temperatures, the effect of solar variation on global climate, and the effect of CO2 on global climate. This analysis is then presented as counter-evidence to the theory that CO2 is the primary cause behind global warming. Increasingly, scientists are pointing to data which suggests that climate changes are a result of natural cycles, which have been occurring for thousands of years. Unfortunately, global warming has moved into the political realm without enough peer-reviewed research to fully validate and exclude other, more natural, causes of climate change. For example, there is an absence of any physical evidence that CO2 causes global warming, so the only argument for CO2 as the cause of warming rests entirely in computer modeling. Thus, the question becomes, how accurate are the computer models in predicting climate? What other variables could be missing from the models? In order to understand modern climate changes, we need to look at the past history of climate changes. Vast amounts of physical evidence of climate change over the past centuries and millennia have been gathered by scientists. Significant climate changes have clearly been going on for many thousands of years, long before the recent rise in atmospheric CO2 Evidence-Based Climate Science, Data Opposing CO2 Emissions as the Primary Source of Global Warming, Second Edition, documents past climate changes and presents physical evidence for possible causes.Provides scientific evidence for issues related to global climate change that is not readily available elsewhereOffers detailed analysis of temperature measurements with the goal of helping readers to understand conflicting claims about global warming heard every day in the news mediaPresents real-time data on polar icePresents the real-time effect of CO2 on global warming, rather than forecasts based on computer models

Abstract: Climate change is one of the global issue that would affect the sustainable development of many regions. The objective of this review is the effect of climate change on water resources. Climate change affects certain components of the hydrological cycle, especially precipitation and runoff. A change in climate can alter the spatial and temporal availability of water resources. The effects of minor levels of climate change are already being felt, with impacts across many economic sectors. These changes will result in increased floods and drought, which will have significant impacts on the availability of freshwater. These impacts on freshwater will be further compounded by rising sea levels, and melting glaciers. In general a warmer climate will accelerate the hydrologic cycle, altering rainfall, magnitude and timing of run-off.

Abstract: available alternative trajectory. The international climate change negotiations can be seen as an opportunity to create an environment that will help in the discovery of a more sustainable urbanisation. This paper explores a limited set of emergent issues that will have to be considered as India develops its domestic approach to urbanisation, while negotiating its international position on climate change. It is structured into three broad sections, viz, (a) the feedback loops from urbanisation to climate change and vice versa, (b) actions needed at multiple levels to influence these processes, and (c) the implications of these for India's negotiating position on climate change.

Abstract: Global warming and energy transition are two of the most important challenges humanity will ever meet. These are complex issues by themselves and by the interconnection they have with each other. The purpose of this chapter is to present an integrated picture of these problems, of their connections, and of a number of scientific and historical facts that should be known before elaborating scenarios for the future.

Abstract: In this study the relationship between climate model biases in the control climate and the simulated climate sensitivity are discussed on the basis of perturbed physics ensemble simulations with a globally resolved energy balance (GREB) model. It is illustrated that the uncertainties in the simulated climate sensitivity (estimated by the transient response to CO2 forcing scenarios in the twenty first century or idealized 2 × CO2 forcing experiments) can be conceptually split into two parts: a direct effect of the perturbed physics on the climate sensitivity independent of the control mean climate and an indirect effect of the perturbed physics by changing the control mean climate, which in turn changes the climate sensitivity, as the climate sensitivity itself is depending on the control climate. Biases in the control climate are negatively correlated with the climate sensitivity (colder climates have larger sensitivities), if no physics are perturbed. Perturbed physics that lead to warmer control climate, would in average also lead to larger climate sensitivities, if the control climate is held at the observed reference climate by flux corrections. Thus the effects of control biases and perturbed physics are opposing each other and are partially cancelling each other out. In the GREB model the biases in the control climate are the more important effect for the regional climate sensitivity uncertainties, but for the global mean climate sensitivity both, the biases in the control climate and the perturbed physics, are equally important.

Abstract: Carbon dioxide emissions from fossil-fuel use in China have grown dramatically in the past few decades, yet it emerges that the country's relative contribution to global climate change has remained surprisingly constant. See Letter p.357 Rapid industrialization is often thought to have increased China's impact on the climate system, but the magnitude of the change has remained stubbornly difficult to quantify. Bengang Li et al. use biogeochemical and atmospheric models, combined with a suite of observational data sets, to provide sectoral estimates, with uncertainties. They find that China is responsible for about 10% of the global increase in radiative forcing (essentially, the additional warming) since pre-industrial conditions. Carbon dioxode is the single biggest warming factor, but methane and black carbon are also important. Sulfate aerosols provide a strong counteractive effect, and efforts to reduce pollution could have the effect of accelerating China's contribution to radiative forcing, unless simultaneous emission reductions are put into place.

Abstract: Global Climate Models that are used to simulate past, current and future climates are described, along with their strengths and weaknesses. The various component parts of a climate model that model the atmosphere, hydrosphere, cryosphere, and land surface are briefly described. Climate models provide state-of-the-art assessments of feedback processes that can be compared with observations. The simulations by climate models of the basic feedbacks that control the response to climate forcing are described. The expected responses of the atmospheric and ocean circulation to warming and their effects on surface climate are introduced.

Abstract: A YEAR ago we met hot on the heels of thegeneral election. The mood in Harrogatematched the mood of the nation. There was a feeling that tilings were about to change -that after a gruelling few years locked in pointless local pay negotiations, things were about to get better for nurses.

Abstract: . In our first study on possible flood damages under climate change in Germany, we reported that a considerable increase in flood-related losses can be expected in a future warmer climate. However, the general significance of the study was limited by the fact that outcome of only one global climate model (GCM) was used as a large-scale climate driver, while many studies report that GCMs are often the largest source of uncertainty in impact modelling. Here we show that a much broader set of global and regional climate model combinations as climate drivers show trends which are in line with the original results and even give a stronger increase of damages.

Abstract: The transport sector is currently the second largest emitter of carbon dioxide (CO2) emissions, which is the main anthropogenic greenhouse gas (IPCC, 2013). On the global perspective, transport emissions are increasing fast and they might soon catch up with those from the electricity and heat provision sector (IEA, 2015). In 2010 transport generated about 7.0 gigatonnes of direct greenhouse gas emissions. Mainly driven by fast development of emerging economies, transport might double its emissions by 2050 (IEA, 2015). Decarbonising transport is seen as more challenging compared to other sectors (cf. Creutzig et al., 2015). The fifth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC) indicates that the increase in global average surface temperature is very likely due to the observed raise in anthropogenic greenhouse gas emissions and the target to keep global warming below 2L requires severe efforts by the society (IPCC, 2015). In contradiction, transport has not been in the focus of the political agenda (Creutzig et al., 2015) – mainly because policy makers believe that the economy is strongly dependent on cheap mobility and they fear to annoy their voters. The scientific community should strengthen their proclamation that current societies are still focusing on inefficient and oil dependent mobility technologies. Non-motorised modes, public transport, and electric vehicles might provide competitive and efficient abatement options with further social benefits in the future (Creutzig, 2015; Jochem et al., 2015). Otherwise, the ongoing increase in greenhouse gas emissions from transport will highly probably continue for the next decades, due to the rising global vehicle fleet and increasing volumes in freight transport and aviation.

Abstract: While climate models and observations generally agree that climate feedbacks collectively amplify the surface temperature response to radiative forcing, the strength of the feedback estimates varies greatly, resulting in appreciable uncertainty in equilibrium climate sensitivity. Because climate feedbacks respond differently to different spatial variations in temperature, short-term observational records have thus far only provided a weak constraint for climate feedbacks operating under global warming. Further complicating matters is the likelihood of considerable time variation in the effective global climate feedback parameter under transient warming. There is a need to continue to revisit the underlying assumptions used in the traditional forcing-feedback framework, with an emphasis on how climate models and observations can best be utilized to reduce the uncertainties. Model simulations can also guide observational requirements and provide insight on how the observational record can most effectively be analyzed in order to make progress in this critical area of climate research.

Abstract: . Numerous studies have focused on the local and regional climate effects of irrigated agriculture and other land cover and land use change (LCLUC) phenomena, but there are few studies on the role of ocean–atmosphere interaction in modulating irrigation climate impacts. Here, we compare simulations with and without interactive sea surface temperatures of the equilibrium effect on climate of contemporary (year 2000) irrigation geographic extent and intensity. We find that ocean–atmosphere interaction does impact the magnitude of global-mean and spatially varying climate impacts, greatly increasing their global reach. Local climate effects in the irrigated regions remain broadly similar, while non-local effects, particularly over the oceans, tend to be larger. The interaction amplifies irrigation-driven standing wave patterns in the tropics and midlatitudes in our simulations, approximately doubling the global-mean amplitude of surface temperature changes due to irrigation. The fractions of global area experiencing significant annual-mean surface air temperature and precipitation change also approximately double with ocean–atmosphere interaction. Subject to confirmation with other models, these findings imply that LCLUC is an important contributor to climate change even in remote areas such as the Southern Ocean, and that attribution studies should include interactive oceans and need to consider LCLUC, including irrigation, as a truly global forcing that affects climate and the water cycle over ocean as well as land areas.

Abstract: Solar geoengineering has been proposed as a potential means to counteract anthropogenic climate change, yet it is unknown how such climate intervention might affect the Earth's climate on the millennial time scale. Here we use the HadCM3L model to conduct a 1000year sunshade geoengineering simulation in which solar irradiance is uniformly reduced by 4% to approximately offset global mean warming from an abrupt quadrupling of atmospheric CO2. During the 1000year period, modeled global climate, including temperature, hydrological cycle, and ocean circulation of the high-CO2 simulation departs substantially from that of the control preindustrial simulation, whereas the climate of the geoengineering simulation remains much closer to that of the preindustrial state with little drift. The results of our study do not support the hypothesis that nonlinearities in the climate system would cause substantial drift in the climate system if solar geoengineering was to be deployed on the timescale of a millennium.