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People’s perception of their own efficacy is a critical precursor for adaptive behavioural responses to the threat posed by climate change. The present study investigated whether components of climate efficacy could be enhanced by short video messages. An online study (N=161) compared groups of participants who received messages focusing on individual or collective behaviour. Relative to a control group, these groups showed increased levels of response efficacy but not self-efficacy. However, this did not translate to increased climate commitment; mediation analysis suggested that the video messages, while increasing efficacy, may also have had a counterproductive effect on behavioural intentions, possibly by reducing the perceived urgency of action. This finding reinforces the challenge faced by climate communicators seeking to craft a message that boosts efficacy and simultaneously motivates adaptive responses to the climate crisis.

A adaptação ao fenômeno das mudanças climáticas é uma questão de grande importância no atual contexto de políticas públicas voltadas ao planejamento urbano das cidades. Em se tratando de sítios de valor histórico-cultural e de bens pertencentes ao patrimônio cultural, o efeito das mudanças climáticas pode acarretar um grande desafio para a garantia da sua conservação. Assim, o presente artigo tem como objetivo apresentar uma revisão narrativa da literatura de artigos científicos e bibliografia de referência sobre o tema do impacto das mudanças climáticas no âmbito patrimonial, comparando criticamente o caso brasileiro com o contexto internacional, sobretudo europeu. Estipulou-se como delimitação temporal o período das duas últimas décadas, entre 2000 e 2020, cinco anos após a primeira conferência mundial sobre o clima da ONU (Organização das Nações Unidas), com a consolidação do compromisso climático e a ampliação de países signatários. A metodologia aplicada é a revisão bibliográfica e compilação dos dados obtidos das publicações, fazendo uso da análise crítica-comparativa. Como resultado, espera-se contribuir com o estado da arte sobre a temática, refletindo sobre os aspectos necessários para avançar no campo na esfera brasileira.

We study the Markov perfect equilibrium in a dynamic game where agents have non-constant time preference, decentralized households determine aggregate savings, and a planner chooses climate policy. The article is the first to solve this problem with general discounting and general functional forms. With time-inconsistent preferences, a commitment device that allows a planner to choose climate policy for multiple periods is potentially very valuable. Nevertheless, our quantitative results show that while a permanent commitment device would be very valuable, the ability to commit policy for “only” 100 years adds less than 2% to the value of climate policy without commitment. We solve a log-linear version of the model analytically, generating a formula for the optimal carbon tax that includes the formula in Golosov et al. (2014, Econometrica, 82, 41–88) as a special case. More importantly, we develop new algorithms to solve the general game numerically. Convex damages lead to strategic interactions across generations of planners that lower the optimal carbon tax by 45% relative to the scenario without strategic interactions.

Regional governments represent an increasingly relevant component in climate change policies, which showcase a high interest in the climate change sphere and provide several benefits connected with their governance. This study aims to shed light on this scale of governance by describing the climate change policies of 61 regions from all over the world and by analysing the possible connections between the regional environmental policy instruments and the level of mitigation and adaptation commitment. The results show that the regional governments of this work appear to be an active component in climate policy, since they all have their own GHG emission reduction targets, devise their own climate policies and instruments and participate in international climate networks. All regions have reported mitigation and adaptation commitments, with different levels of ambition. In addition, it is observable that while some regions (mainly the North) focus mostly on mitigation targets, other (the South) focus on adaptation. Finally, there does not seem to be a connection between the level of climate commitment and the preference for some policy instruments.

Across the developing world, countries are experiencing rapid growth in urbanization and motorization. While high motorization rates potentially meant hat more people will be able to claim the benefits of improved accessibility to goods and services as a consequence of enhanced mobility, there are questions about the sustainability of this future. Will countries be able to build and maintain infrastructure to accommodate increasing numbers of vehicles? Will the increasing number of vehicles and their characteristics support attainment of the Sustainable Development Goals (SDGs) Will they put in jeopardy countries’ ability to meet their climate commitments under their Nationally Determined Contributions (NDCs)? From a development impact standpoint, the nature of a country’s motor vehicle stock and how it grows affects three key and tangible outcomes. First, the quality of the motor vehicle stock affects road safety outcomes—that is, the number of people killed or seriously injured in motor vehicle crashes. The characteristics of vehicles and their fitness or roadworthiness can affect fatality and serious injury outcomes. Second, the quality of the motor vehicle fleet affects air quality, particularly in cities. Motor vehicles are a key source of harmful air pollution, including carbon monoxide (CO), fine particulates (PM2.5), sulfur oxides (SOx), and ozone precursors (oxides of nitrogen and various hydrocarbons), and the amount of these pollutants they emit is directly related to how the vehicle was built and how well it is maintained. Finally, the profile of the vehicle fleet—what is the size and weight of vehicles in the fleet, how big are their engines, what kind of power control technology do they use, and how did their manufacturers engineer the technology of the vehicle to balance power with efficiency—affects the (fossil) fuel consumption of the vehicle stock as a whole, and, consequently, the greenhouse gas (GHG) emissions profile of the road transport sector. This report presents the World Bank’s Motorization Management (MM) framework, which is intended to support client countries in the development of policies and measures aimed at managing vehicle stocks in a proactive, phased, and systematic manner to make them safer, cleaner, and more fuel efficient. The MM framework reflects a series of policy considerations and programs that can be implemented to improve the quality of fuels and vehicles in a country’s stock.

Economic damage from climate change includes several aspects that need to be considered at the global and regional levels to achieve an equitable common solution to global warming. The economic literature reviewed here analyzes this issue under three general perspectives. First, the analytical estimation of the linkages between damages in monetary terms and climate variables, as projections of temperature, precipitation, and frequency of extreme events, is rapidly evolving. Damage functions are included in complex economic models in order to calculate the economic impact of the climate change on economic output and growth, thus informing the debate on the amount of resources that should be devoted to reducing greenhouse gas (GHG) emissions and limiting climate damages. The choice of the geographical aggregation in this respect is a crucial aspect to be considered if policy advice is to be formulated on the basis of model results. The higher the level of regional detail, the more reliable the results are in terms of geographical distribution of economic damages. Second, the precise estimation of the costs associated with different damages caused by climate change is attracting growing interest. Climate costs present a wide range of heterogeneity for several reasons, such as the different formulation of the damage function adopted, the modeling design of the economic impact, the temporal horizon considered, and the differentiation across sectors. Two broad categories of analysis are relevant. The first refers to the choice of the sectoral dimension under investigation, where some studies cover multiple sectors and their interactions, while others analyze specific sectors in depth. The second classification criterion refers to the choice of the economic aspects estimated, where a strand of literature analyzes only market-based costs, while other analyses also include non-market (or intangible) damages. The most common sectors investigated are agriculture, forestry, health, energy, coastal zones and sea level rise, extreme events, tourism, ecosystems, industry, air quality, and catastrophic damages. Most studies consider market-based costs, while non-market impacts need to be better detailed in economic models. Third, the computation of a single number through the analytical framework of the social costs of carbon (SCC) represents a key aspect of the process of adapting complex results in order to properly inform the political debate. SCC represents the marginal global damage cost of carbon emissions and can also be interpreted as the economic value of damages avoided for unitary GHG emission reduction. Several uncertainties still influence the robustness of the SCC analytical framework, such as the choice of the discount rate, which strongly influences the role of SCC in supporting or not mitigation action in the short term. Although the debate on the economic damages arising from climate change is flourishing, several aspects still need to be investigated in order to build a common consensus within the scientific community as a necessary condition to properly inform the political debate and to facilitate the achievement of a long-term equitable global climate agreement.

Credible commitment is central to regimes for climate mitigation policy. In the climate policy literature, it is widely argued that the solution to the credible commitment problem is legislation and delegation of goal-setting to a technical body insulated from political incentives, and the UK’s Committee on Climate Change is in part modelled on this approach. However, drawing on the comparative politics literature, this paper argues that the focus on legislation and delegation as the solution to the credible commitment problem is too narrow. Seen within the context of comparative political institutions, it is a response that fits the political logic in countries with majoritarian electoral systems. By contrast, in countries with electoral systems based on proportional representation, while legislation plays a role, an important element in the creation of credible commitment comes in the form of negotiated long-term agreements between political parties. This contrast is explored through a comparison between the Climate Change Act and associated Committee on Climate Change in the UK on the one hand, and a series of Energy and Climate Agreements in Denmark over the 2010s. Both approaches appear to have worked to date. However, while negotiated long-term agreements typically have an internal process for managing conflicts that inevitably arise after the respective mechanisms have been put in place, disputes arising following legislation and delegation must be resolved within the more informal processes of intra-party politics. Mechanisms of accountability also differ between the two approaches.

The EU has undertaken a thorough reform of its energy model. Current EU 2050 climate commitment sets an 80–95% GHG reduction goal. To reach this goal, the EU must make continued progress towards a low-carbon society. Renewable energy sources and electric vehicle play an important role for a gradual transition. The power grid faces a challenging future due to intermittency and the non-dispatchable nature of wind and solar energy production, but flexibility needs can migrate from generation to load, with the expansion of demand-side resources and storage technologies. A novel grid technique is presented and evaluated in this paper for the optimal integrated operation of renewable resources and electric vehicle to increase penetration of renewable energy. It is proposed a distribute control system to manage a charge and discharge strategy to support mismatching between load and renewable generation thru V2G technology. Demand response, peak saving and ancillary services are introduced to keep a reliable power quality, stable frequency and flatten load profile.

There are few global challenges as widespread, as complex, as significant to our future, and politically as controversial as that of global warming. The goal of this chapter is, in essence, to motivate this textbook; to convince you, the reader, that very nearly all of the topics in this text need to be understood in order to grasp the subtleties of a subject such as global warming.

Insolation is the incoming energy from the Sun. It is at shorter wavelengths of ultraviolet, the visible spectrum, and the near infrared. Albedo is the reflection of incoming energy back into space by the planet. To maintain a given temperature, the Earth radiates energy back into space at invisible infrared wavelengths. In doing so, it must redistribute the energy. But the weather is inherently chaotic. The major components of Earth’s climate system are air, earth, ice, and water: the atmosphere, hydrosphere, cryosphere, and land. Climatic regions are commonly classified by their vegetation, which integrates the climate signal over time. Some uncertainties in the components of the climate scheme remain.

Australia has been one of the majority countries in the world which has committed to the Paris Agreement and has implemented it to cut their emission. Climate change is a tremendous challenge for human being for the past 20 years, since the development of technology and the growing needs of human has driven us to find more source to fulfil our needs. Australia has agreed to cut their emission for 26-28% that is envisioned to be realized in 2030. However, the Australia’s commitment becomes questionable since the massive approval of Liquified Natural Gas in 2016. Experts claim the approval of Liquified Natural Gas will disturb the steady graph emission of Australia. This study aims to find out and analyze the reason behind Australia massive approval to Liquified Natural Gas Project. This study is qualitative research using descriptive analysis method with secondary data types. The result of study shows that, the reason behind the massive approval of Liquified Natural Gas in Australia are to increase and boost up the economy for Australia while at same time open a wider job opportunities for its people.

Climate change is affecting the health of millions of people through altering the geographic distribution and incidence of climate-sensitive health outcomes, including through injuries, illnesses, and deaths due to extreme weather events, food-, water-, and vectorborne diseases, air pollution, aeroallergens, and malnutrition (1). The magnitude of impacts is projected to increase as the climate continues to change. The scope and scale of projected impacts mean that climate change will touch the professional and personal lives of many public health and health care professionals. Avoiding, preparing for, and effectively responding to the health risks of climate change will require broad engagement of scientists, decision-makers, and the public. Achieving this engagement means that increased scientific literacy is needed of the causes and implications of climate change for human health. There are growing numbers of assessments of the potential health impacts of climate change (1–4) and summaries for various audiences (5). Instead of summarizing current knowledge of the causes and consequences for human health of anthropogenic climate change, this paper will highlight a few issues that may help with understanding the human health impacts of climate change. Energy drives climate change as well as its consequences Energy refers to both the energy derived from burning fossil fuels, which, along with deforestation, is the primary cause of anthropogenic climate change, and to the resulting increased energy within the climate system that is manifest in the form of increased temperatures, alterations of the hydrologic cycle, and more frequent and intense extreme weather events. The principal driving force for weather and climate is the uneven warming of the Earth’s surface (due to the angle of rotation). Complex and changing atmospheric and oceanic patterns redistribute the absorbed solar energy from the equator to the poles. In addition, some absorbed energy is reradiated as long-wave (infrared) radiation. Some of this infrared radiation is then absorbed by the atmospheric greenhouse gases (including water vapour, carbon dioxide, methane, nitrous oxide, halocarbons, and ozone) and reradiated back to the Earth, thereby adding additional energy to the atmosphere and oceans. This greenhouse effect warms the surface by more than would be achieved by incoming solar radiation alone and raises the global average surface temperature to its current 15°C (6). Without this warming, the Earth’s diurnal temperature range would increase dramatically, and the global average surface temperature would be about 33°C colder. Increasing concentrations of greenhouse gases are increasing the energy in the atmosphere, further warming the planet. Current concentrations of atmospheric CO2 and ethane far exceed pre-industrial values found in polar ice core records dating back 650,000 years; the concentration of atmospheric CO2 has increased from a pre-industrial value of about 280 ppm to 379 ppm in 2005 (7). Since 1750, it is estimated that about 2/3rd of anthropogenic CO2 emissions have come from fossil fuel burning and about 1/3rd from land use change. Ambient temperatures increased 0.74°C worldwide over the period 1906–2005. The rate of warming averaged over the past 50 years (0.13°C + 0.03°C per decade) is nearly twice that for the last 100 years (Figure 1), and at least six times faster than at any time during the 2,000 years. Figure 1: Figure 1: Global mean temperature increase (°C) from 1850 to 2005 (7). Annual global mean temperatures (black dots) with linear fits to the data. The left axis shows temperature anomalies relative to 1961–1990 and the right hand axis shows ... The Earth is committed to decades of climate change Figure 2, from the Intergovernmental Panel on Climate Change (IPCC), shows projected temperature changes over this century based on different scenarios of greenhouse gas emissions (7). These scenarios are based on differing assumptions of future demographic, economic, and technology changes that determine the amount of fossil fuels that will be burned. The IPCC projected that the global mean temperature of the Earth would increase by the end of the 21st century by between 1.1 and 6.4°C (7). This projected rate of warming is much larger than the observed changes during the 20th century and is very likely to be without precedent during at least the last 10,000 years. Figure 2: Observed and Projected Global Mean Surface Temperatures (°C), 1900 to 2100. Solid lines are multi-model global averages of surface warming (relative to 1980–1999) for the scenarios A2, A1B and B1, shown as continuations of the 20th century ... The orange line on the figure is the climate change commitment or the amount of warming that will occur no matter the degree to which greenhouse gas emissions are reduced over the next few decades. This commitment is due to the inherent inertia in the climate system. Natural processes currently remove about half the incremental anthropogenic CO2 added to the atmosphere annually; the balance is removed over one to two hundred years (7). The Earth is committed to nearly as much warming as has already occurred.

Brasil ha sido históricamente un actor relevante en la gobernanza global del cambio climático. A finales de los 2000s, bajo la Presidencia de Lula, el país parecía convertirse además en un líder global, dando muestras de compromiso climático en varios niveles de análisis, con emisiones decreciendo y actores nacionales, subnacionales, organizaciones de la sociedad civil y del mercado comprometidos con la mitigación. A 10 años de aquella euforia, el contraste no podría ser mayor. El gobierno federal está comandado por uno de los pocos líderes negadores del cambio climático a nivel global, Jair Bolsonaro, que ha coronado un proceso de retracción conservadora en todos los niveles iniciada en 2011. Este artículo analiza la trayectoria del compromiso climático brasileño entre 2009 y 2020, desde una perspectiva de gobernanza multinivel y usando como marco analítico el enfoque del compromiso climático. Brazil has historically been a relevant actor in the global governance of climate change. In the late 2000s, under President Lula, the country also seemed to become a global leader, showing signs of climate commitment at various levels of analysis, with declining emissions and national, sub-national, civil society and market actors committed to mitigation. Ten years after that euphoria, the contrast could not be greater. The federal government is led by one of the few global climate change denial leaders, Jair Bolsonaro, who has crowned a process of conservative retrenchment at all levels that began in 2011. This article analyses the trajectory of Brazil’s climate commitment between 2009 and 2020, from a multilevel governance perspective and using the climate commitment approach as an analytical framework.

Energy efficiency improvement and energy substitution are not only main ways to reduce energy consumption and carbon dioxide emissions in China, but also play important roles in achieving China’s international commitments and coping with the challenges of global climate change. From the beginning of the 11th Five-Year Plan (FYP), China has adopted a series of policies and measures in ways of improving energy efficiency, optimizing energy structure, developing low-carbon city pilots and so forth. This study takes use of the China-in-Global Energy Model to analyze the future carbon dioxide emissions and energy consumption under different scenarios, and then calculates the contributions of energy efficiency improvement and energy substitution to realizing the mitigation target of China’s National Determined Contributions. The results show that energy efficiency improvement plays more important role in reducing carbon intensity than energy substitution. But as time goes on, the contribution of energy substitution will increase while the effect of energy efficiency improvement will diminish gradually. In addition, energy substitution can play a greater role in achieving China’s climate pledge when increasing the strength of carbon emissions reduction.

Recently we have had abnormal weather events worldwide that are attributed by climate scientists to the global warming induced by human activities. If the global warming continues in the future and such events occur more frequently and someday become normal, we will have an unprecedented climate. This study intends to answer when we will have an unprecedented warm climate, focusing more on the regional characteristics of the timing of unprecedented climate. Using an in-situ observational data from weather stations of annual-mean surface air temperature in Korea from 1973 to 2015, we estimate a timing of unprecedented climate with a linear regression method. Based on the in-situ data with statistically significant warming trends at 95% confidence level, an unprecedented climate in Korea is projected to occur first in Cheongju by 2043 and last in Haenam by 2168. This 125-year gap in the timing indicates that a regional difference in timing of unprecedented climate is considerably large in Korea. Despite the high sensitivity of linear estimation to the data period and resolution, our findings on the large regional difference in timing of unprecedented climate can give an insight into making policies for climate change mitigation and adaptation, not only for the central government but for provincial governments.

Nature Geoscience, 10 (10), ISSN:1752-0908, ISSN:1752-0894

Whether a cloud is predominantly water or ice strongly influences interactions between clouds and radiation coming down from the Sun or up from the Earth. Being able to simulate cloud phase transitions accurately in climate models based on observational data sets is critical in order to improve confidence in climate projections, because this uncertainty contributes greatly to the overall uncertainty associated with cloud-climate feedbacks. Ultimately, it translates into uncertainties in Earth's sensitivity to higher CO2 levels. While a lot of effort has recently been made toward constraining cloud phase in climate models, more remains to be done to document the radiative properties of clouds according to their phase. Here we discuss the added value of a new satellite data set that advances the field by providing estimates of the cloud radiative effect as a function of cloud phase and the implications for climate projections.

The expanding interest in decadal climate variability, predictability, and prediction highlights the importance of understanding the sources and mechanisms of decadal and interdecadal climate fluctuations. The purpose of this paper is to provide a critical review of our current understanding of externally forced decadal climate variability. In particular, proposed mechanisms determining decadal climate responses to variations in solar activity, stratospheric volcanic aerosols, and natural as well as anthropogenic tropospheric aerosols are discussed, both separately and in a unified framework. The review suggests that the excitation of internal modes of interdecadal climate variability, particularly centered in the Pacific and North Atlantic sectors, remains a paradigm to characterize externally forced decadal climate variability and to interpret the associated dynamics. Significant recent advancements are the improved understanding of the critical dependency of volcanically forced decadal climate variability on the relative phase of ongoing internal variability and on additional external perturbations, and the recognition that associated uncertainty may represent a serious obstacle to identifying the climatic consequences even of very strong eruptions. Particularly relevant is also the recent development of hypotheses about potential mechanisms (reemergence and synchronization) underlying solar forced decadal climate variability. Finally, outstanding issues and, hence, major opportunities for progress regarding externally forced decadal climate variability are discussed. Uncertain characterization of forcing and climate histories, imperfect implementation of complex forcings in climate models, limited understanding of the internal component of interdecadal climate variability, and poor quality of its simulation are some of the enduring critical obstacles on which to progress. It is suggested that much further understanding can be gained through identification and investigation of relevant periods of forced decadal climate variability during the preindustrial past millennium. Another upcoming opportunity for progress is the analysis of focused experiments with coupled ocean–atmosphere general circulation models within the umbrella of the next phase of the coupled model intercomparison project.

Estimates of equilibrium climate sensitivity differ depending on the method of calculation. This study shows estimates based on the historical energy budget are low as climate feedbacks vary with time and the bias depends on the sensitivity of the system. Global energy budget constraints1,2,3 suggest an equilibrium climate sensitivity around 2 °C, which is lower than estimates from palaeoclimate reconstructions4, process-based observational analyses5,6,7, and global climate model simulations8,9. A key assumption is that the climate sensitivity inferred today also applies to the distant future. Yet, global climate models robustly show that feedbacks vary over time, with a strong tendency for climate sensitivity to increase as equilibrium is approached9,10,11,12,13,14,15,16,17,18. Here I consider the implications of inconstant climate feedbacks for energy budget constraints on climate sensitivity. I find that the long-term value of climate sensitivity is, on average, 26% above that inferred during transient warming within global climate models, with a larger discrepancy when climate sensitivity is high. Moreover, model values of climate sensitivity inferred during transient warming are found to be consistent with energy budget observations1,2,3, indicating that the models are not overly sensitive. Using model-based estimates of how climate feedbacks will change in the future, in conjunction with recent energy budget constraints1,19, produces a current best estimate of equilibrium climate sensitivity of 2.9 °C (1.7–7.1 °C, 90% confidence). These findings suggest that climate sensitivity estimated from global energy budget constraints is in agreement with values derived from other methods and simulated by global climate models.

The warming caused by past CO2 emissions is known to persist for centuries to millennia, even in the absence of additional future emissions. Other non-CO2 greenhouse gas emission have caused additional historical warming, though the persistence of this non-CO2 warming varies among gases owing to their different atmospheric lifetimes. Under deep mitigation scenarios or in an idealized scenario of zero future greenhouse gas emissions, the past warming from shorter-lived non-CO2 gases has been shown to be considerably more reversible than that caused by CO2 emissions. Here we use an intermediate-complexity global climate model coupled to an atmospheric chemistry module to quantify the warming commitment and its reversibility for individual and groups of non-CO2 greenhouse gases. We show that warming caused by gases with short atmospheric lifetimes will decrease by more than half its peak value within 30 years following zeroed emissions at present day, with more 80 percent of peak temperature reversed by the end of this century. Despite the fast response of atmospheric temperature to the elimination of non-CO2 emissions, the ocean responds much more slowly: past ocean warming does not reverse, but rather continues for several centuries after zero emissions. Further consequences are shown for the land carbon pool, which decreases as an approximately linear function of historical non-CO2 greenhouse gas induced warming. Given that CO2 and non-CO2 greenhouse gas emissions share common emission sources, we also explore a set of scenarios where sets of emissions are zeroed according to two broad source categories: (1) fossil fuel combustion, and (2) land-use and agriculture. Using these additional mode runs, we investigate the temperature change that is avoided if all CO2 and non-CO2 greenhouse gas emissions from a particular source abruptly stops while others are allowed to continue. These results indicate the possibility of land-use change and agriculture activities continuing under deep mitigation scenarios and ambitious climate targets, without leading to exceedance of global climate targets. Though we analyze unlikely scenarios, our work provides baselines from which more realistic mitigation scenarios can be assessed. The reversibility of peak temperature caused by historical non-CO2 gases is a relevant measure for policy frameworks seeking to limit global warming to ambitious targets, such as the 1.5 oC target adopted by the Paris Agreement

Following a land cover and land management change (LCMC), local surface temperature responds to both a change in available energy and a change in the way energy is redistributed by various non-radiative mechanisms. However, the extent to which non-radiative mechanisms contribute to the local direct temperature response for different types of LCMC across the world remains uncertain. Here, we combine extensive records of remote sensing and in situ observation to show that non-radiative mechanisms dominate the local response in most regions for eight of nine common LCMC perturbations. We find that forest cover gains lead to an annual cooling in all regions south of the upper conterminous United States, northern Europe, and Siberia—reinforcing the attractiveness of re-/afforestation as a local mitigation and adaptation measure in these regions. Our results affirm the importance of accounting for non-radiative mechanisms when evaluating local land-based mitigation or adaptation policies. Remote sensing and in situ observations show that non-radiative mechanisms dominate the local climatic response to land cover and land management changes in most regions of the globe for 8 of 9 common land cover and management perturbations.

There is large uncertainty in the simulation of transient climate sensitivity. This study aims to understand how such uncertainty is related to the simulation of the base climate by comparing two simulations with the same model but in which CO2 is increased from either a preindustrial (1860) or a present-day (1990) control simulation. This allows different base climate ocean circulations that are representative of those in current climate models to be imposed upon a single model. As a result, the model projects different transient climate sensitivities that are comparable to the multimodel spread. The greater warming in the 1990-start run occurs primarily at high latitudes and particularly over regions of oceanic convection. In the 1990-start run, ocean overturning circulations are initially weaker and weaken less from CO2 forcing. As a consequence, there are smaller reductions in the poleward ocean heat transport, leading to less tropical ocean heat storage and less moderated high-latitude surface warming. This process is evident in both hemispheres, with changes in the Atlantic meridional overturning circulation and the Antarctic Bottom Water formation dominating the warming differences in each hemisphere. The high-latitude warming in the 1990-start run is enhanced through albedo and cloud feedbacks, resulting in a smaller ocean heat uptake efficacy. The results highlight the importance of improving the base climate ocean circulation in order to provide a reasonable starting point for assessments of past climate change and the projection of future climate change.

Climate projections are based on emission scenarios. The emission scenarios used by the IPCC and by mainstream climate scientists are largely derived from the predicted demand for fossil fuels, and in our view take insufficient consideration of the constrained emissions that are likely due to the depletion of these fuels. This paper, by contrast, takes a supply-side view of CO 2 emission, and generates two supply-driven emission scenarios based on a comprehensive investigation of likely long-term pathways of fossil fuel production drawn from peer-reviewed literature published since 2000. The potential rapid increases in the supply of the non-conventional fossil fuels are also investigated. Climate projections calculated in this paper indicate that the future atmospheric CO 2 concentration will not exceed 610 ppm in this century; and that the increase in global surface temperature will be lower than 2.6 °C compared to pre-industrial level even if there is a significant increase in the production of non-conventional fossil fuels. Our results indicate therefore that the IPCC’s climate projections overestimate the upper-bound of climate change. Furthermore, this paper shows that different production pathways of fossil fuels use, and different climate models, are the two main reasons for the significant differences in current literature on the topic.

Forty-five years after it was first proposed, climate change has revived debates around the concept of limits to growth. This Review reflects on economic perspectives on limits to growth, and proposes a third option to reduce resistance to climate policies. Climate change has revived debates around the concept of limits to growth, 45 years after it was first proposed. Many citizens, scientists and politicians fear that stringent climate policy will harm economic growth. Some are anti-growth, whereas others believe green growth is compatible with a transition to a low-carbon economy. As the window to curb warming at 2 °C closes, this debate will intensify. This Review critically reflects on both positions, providing an overview of existing literature on the growth versus climate debate. Both positions are argued here to jeopardize environmental or social goals. A third position, labelled an 'agrowth' strategy, is proposed to depolarize the debate and reduce resistance to climate policies.

Temperature responses and optimal climate policies depend crucially on the choice of a particular climate model. To illustrate, the temperature responses to given emission reduction paths implied by the climate modules of the well-known integrated assessments models DICE, FUND and PAGE are described and compared. A dummy temperature module based on the climate denialists' view is added. Using a simple welfare-maximising growth model of the global economy, the sensitivity of the optimal carbon price, renewable energy subsidy and energy transition to each of these climate models is discussed. The paper then derives max-min, max-max and min-max regret policies to deal with this particular form of climate (model) uncertainty and with climate scepticism. The max-min or min-max regret climate policies rely on a non-sceptic view of global warming and lead to a substantial and moderate amount of caution, respectively. The max-max leads to no climate policies in line with the view of climate sceptics.

The 2015 Paris Climate Conference elicited largely independent and individual commitments from the participating countries (so-called intended nationally determined contributions) in an effort to c...

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.

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.

Summary In the ongoing debate about the climate benefits of fuel switching from coal to natural gas for power generation, the metrics used to model climate impacts may be important. In this article, we evaluate the life cycle greenhouse gas emissions of coal and natural gas used in new, advanced power plants using a broad set of available climate metrics in order to test for the robustness of results. Climate metrics included in the article are global warming potential, global temperature change potential, technology warming potential, and cumulative radiative forcing. We also used the Model for the Assessment of Greenhouse-gas Induced Climate Change (MAGICC) climate-change model to validate the results. We find that all climate metrics suggest a natural gas combined cycle plant offers life cycle climate benefits over 100 years compared to a pulverized coal plant, even if the life cycle methane leakage rate for natural gas reaches 5%. Over shorter time frames (i.e., 20 years), plants using natural gas with a 4% leakage rate have similar climate impacts as those using coal, but are no worse than coal. If carbon capture and sequestration becomes available for both types of power plants, natural gas still offers climate benefits over coal as long as the life cycle methane leakage rate remains below 2%. These results are consistent across climate metrics and the MAGICC model over a 100-year time frame. Although it is not clear whether any of these metrics are better than the others, the choice of metric can inform decisions based on different societal values. For example, whereas annual temperature change reported may be a more relevant metric to evaluate the human health effects of increased heat, the cumulative temperature change may be more relevant to evaluate climate impacts, such as sea-level rise, that will result from the cumulative warming.

Reconstructions of historical climate changes indicate that surface air temperatures decreased over the preindustrial last millennium. Conflicting explanations have been proposed for the cause of the transition from the Medieval Climate Anomaly (MCA) in the early part of the last millennium to the Little Ice Age (LIA) near its end. The possible causes include volcanic emissions, total solar irradiance (TSI) variations, greenhouse gas concentration fluctuations, and orbital forcing variations. In the present paper, it is demonstrated that all of these climate forcings contribute significantly to simulated surface air temperature (SAT) and sea ice concentration changes over this period. On the other hand, simulated ocean heat content appears to respond significantly only to volcanic and TSI variations. In model simulations at T85 spectral resolution, TSI reductions and volcanic emissions together generate significant increases in sea ice extent in the Barents Sea, which is found to be responsible for most of the temperature reductions over northwestern Europe. TSI appears less important to Arctic sea ice and SAT changes in simulations at T42 spectral resolution, which are weaker than at T85 resolution. Such resolution dependence is attributed to differences in background conditions in the responses to these external climate forcings. Nonlinearities in the forcing responses and sensitivities to background conditions challenge the assumption that sensitivity tests for given forcings can be run independently. Additionally, it is demonstrated that an ensemble of model simulations is required to isolate forcing responses even over a period as long as the last millennium.

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.

The projected warming of surface air temperature at the global and regional scale by the end of the century is directly related to emissions and Earth’s climate sensitivity. Projections are typically produced using an ensemble of climate models such as CMIP5, however the range of climate sensitivity in models doesn’t cover the entire range considered plausible by expert judgment. Of particular interest from a risk-management perspective is the lower impact outcome associated with low climate sensitivity and the low-probability, high-impact outcomes associated with the top of the range. Here we scale climate model output to the limits of expert judgment of climate sensitivity to explore these limits. This scaling indicates an expanded range of projected change for each emissions pathway, including a much higher upper bound for both the globe and Australia. We find the possibility of exceeding a warming of 2 °C since pre-industrial is projected under high emissions for every model even scaled to the lowest estimate of sensitivity, and is possible under low emissions under most estimates of sensitivity. Although these are not quantitative projections, the results may be useful to inform thinking about the limits to change until the sensitivity can be more reliably constrained, or this expanded range of possibilities can be explored in a more formal way. When viewing climate projections, accounting for these low-probability but high-impact outcomes in a risk management approach can complement the focus on the likely range of projections. They can also highlight the scale of the potential reduction in range of projections, should tight constraints on climate sensitivity be established by future research.

The response of temperature to CO2 change (climate sensitivity) in the geologic past may help inform future climate predictions. Proxies for CO2 and temperature generally imply high climate sensitivities: ≥3 K per CO2 doubling during ice-free times (fast-feedback sensitivity) and ≥6 K during times with land ice (Earth-system sensitivity). Climate models commonly underpredict the magnitude of climate change and have fast-feedback sensitivities close to 3 K. A better characterization of feedbacks in warm worlds raises climate sensitivity to values more in line with proxies and produces climate simulations that better fit geologic evidence. As CO2 builds in our atmosphere, we should expect both slow (e.g., land ice) and fast (e.g., vegetation, clouds) feedbacks to elevate the long-term temperature response over that predicted from the canonical fast-feedback value of 3 K. Because temperatures will not decline for centuries to millennia, climate sensitivities that integrate slower processes have relevance for current climate policy.

The atmospheric response to increasing CO2 concentrations is often described in terms of the equilibrium climate sensitivity (ECS). Yet the response to CO2 forcing in global climate models is not limited to an increase in global-mean surface temperature: for example, the midlatitude jets shift poleward, the Hadley circulation expands, and the subtropical dry zones are altered. These changes, which are referred to here as “dynamical sensitivity,” may be more important in practice than the global-mean surface temperature. This study examines to what degree the intermodel spread in the dynamical sensitivity of 23 Coupled Model Intercomparison Project phase 5 (CMIP5) models is captured by ECS. In the Southern Hemisphere, intermodel differences in the value of ECS explain ~60% of the intermodel variance in the annual-mean Hadley cell expansion but just ~20% of the variance in the annual-mean midlatitude jet response. In the Northern Hemisphere, models with larger values of ECS significantly expand the Hadley circulation more during winter months but contract the Hadley circulation more during summer months. Intermodel differences in ECS provide little significant information about the behavior of the Northern Hemisphere subtropical dry zones or midlatitude jets. The components of dynamical sensitivity correlated with ECS appear to be driven largely by increasing sea surface temperatures, whereas the components of dynamical sensitivity independent of ECS are related in part to changes in surface temperature gradients. These results suggest that efforts to narrow the spread in dynamical sensitivity across global climate models must also consider factors that are independent of global-mean surface temperature.

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.

This article discusses the phenomenon and mechanisms of climate change and the models used to study climate dynamics and predict future climate change. It describes past climate variations on the geological timescales reconstructed using paleoclimatological methods and a more recent climate change derived from observations. The article presents the scientific basis and the spectrum of existing climate models. An overview of modeling predictions of future climate change is given and principal uncertainties associated with climate predictions are discussed. A possible impact of future climate change on natural ecosystems, food production, and human health is also discussed.

PrefaceAbbreviations1. Climate in Context2. The Character of the Atmosphere3. The World Ocean4. The Carbon Cycle and How It Influences Climate5. A Scientific Framework for Thinking About Climate Change6. Learning from Climates Past7. A Century of Warming and Some Consequences8. More Consequences: The Sensitive Arctic and Sea-Level Rise9. Climate Models and the Future10. Energy and the FutureNotesGlossaryBibliographyIndex

At present, global climate models used to project changes in climate poorly resolve mesoscale ocean features such as boundary currents and eddies. These missing features may be important to realistically project the marine impacts of climate change. Here we present a framework for dynamically downscaling coarse climate change projections utilising a near-global ocean model that resolves these features in the Australasian region, with coarser resolution elsewhere. A time-slice projection for a 2060s ocean was obtained by adding climate change anomalies to initial conditions and surface fluxes of a near-global eddy-resolving ocean model. Climate change anomalies are derived from the differences between present and projected climates from a coarse global climate model. These anomalies are added to observed fields, thereby reducing the effect of model bias from the climate model. The downscaling model used here is ocean-only and does not include the effects that changes in the ocean state will have on the atmosphere and air–sea fluxes. We use restoring of the sea surface temperature and salinity to approximate real-ocean feedback on heat flux and to keep the salinity stable. Extra experiments with different feedback parameterisations are run to test the sensitivity of the projection. Consistent spatial differences emerge in sea surface temperature, salinity, stratification and transport between the downscaled projections and those of the climate model. Also, the spatial differences become established rapidly (< 3 yr), indicating the importance of mesoscale resolution. However, the differences in the magnitude of the difference between experiments show that feedback of the ocean onto the air–sea fluxes is still important in determining the state of the ocean in these projections. Until such a time when it is feasible to regularly run a global climate model with eddy resolution, our framework for ocean climate change downscaling provides an attractive way to explore the response of mesoscale ocean features with climate change and their effect on the broader ocean.

The aim of climate research is to increase our knowledge about the nature of climate and the causes of climate variability and change. Increasing our understanding of the physical processes on various spatial and temporal scales will ultimately reduce uncertainty and improve our capabilities to predict climate on monthly to seasonal timescales and allow us to separate the anthropogenic and natural causes of long term climate change.