Showing papers on "Runaway climate change published in 2016"

Reconciled climate response estimates from climate models and the energy budget of Earth

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.

Distinct energy budgets for anthropogenic and natural changes during global warming hiatus

Abstract: Closure of the Earth’s energy budget relies on strong aerosol cooling since 1998, if the same feedbacks apply for anthropogenic and natural variability. An analysis of climate model simulations suggests that these feedbacks are instead distinct.

Large-scale ocean circulation-cloud interactions reduce the pace of transient climate change

Abstract: Changes to the large-scale oceanic circulation are thought to slow the pace of transient climate change due, in part, to their influence on radiative feedbacks. Here we evaluate the interactions between CO2-forced perturbations to the large-scale ocean circulation and the radiative cloud feedback in a climate model. Both the change of the ocean circulation and the radiative cloud feedback strongly influence the magnitude and spatial pattern of surface and ocean warming. Changes in the ocean circulation reduce the amount of transient global warming caused by the radiative cloud feedback by helping to maintain low cloud coverage in the face of global warming. The radiative cloud feedback is key in affecting atmospheric meridional heat transport changes and is the dominant radiative feedback mechanism that responds to ocean circulation change. Uncertainty in the simulated ocean circulation changes due to CO2 forcing may contribute a large share of the spread in the radiative cloud feedback among climate models.

Climate Change: Basic Information

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

Future Warming Patterns Linked to Today's Climate Variability.

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.

Deep time evidence for climate sensitivity increase with warming

Abstract: Future global warming from anthropogenic greenhouse gas emissions will depend on climate feedbacks, the effect of which is expressed by climate sensitivity, the warming for a doubling of atmospheric CO2 content. It is not clear how feedbacks, sensitivity, and temperature will evolve in our warming world, but past warming events may provide insight. Here we employ paleoreconstructions and new climate-carbon model simulations in a novel framework to explore a wide scenario range for the Paleocene-Eocene Thermal Maximum (PETM) carbon release and global warming event 55.8 Ma ago, a possible future warming analogue. We obtain constrained estimates of CO2 and climate sensitivity before and during the PETM and of the PETM carbon input amount and nature. Sensitivity increased from 3.3–5.6 to 3.7–6.5 K (Kelvin) into the PETM. When taken together with Last Glacial Maximum and modern estimates, this result indicates climate sensitivity increase with global warming.

Global warming: China’s contribution to climate change

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.

Change Of Climate

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.

Global Climate Models

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.

Significant implications of permafrost thawing for climate change control

Abstract: Large amounts of carbon are stored as permafrost within the Arctic and sub-Arctic regions. As permafrost thaws due to climate warming, carbon dioxide and methane are released. Recent studies indicate that the pool of carbon susceptible to future thaw is higher than was previously thought and that more carbon could be released by 2100, even under low emission pathways. We use an integrated model of the climate and the economy to study how including these new estimates influence the control of climate change to levels that will likely keep the temperature increase below 2 °C (radiative forcing of 2.6 Wm−2). According to our simulations, the fossil fuel and industrial CO2 emissions need to peak 5–10 years earlier and the carbon budget needs to be reduced by 6–17 % to offset this additional source of warming. The required increase in carbon price implies a 6–21 % higher mitigation cost to society compared to a situation where emissions from permafrost are not considered. Including other positive climate feedbacks, currently not accounted for in integrated assessment models, could further increase these numbers.

Simulated long‐term climate response to idealized solar geoengineering

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.

Arctic climate change: Greenhouse warming unleashed

Abstract: Human activity alters the atmospheric composition, which leads to global warming. Model simulations suggest that reductions in emission of sulfur dioxide from Europe since the 1970s could have unveiled rapid Arctic greenhouse gas warming.

Climate Change Indicators: U.S. and Global Temperature

Abstract: This indicator describes trends in average surface temperature for the United States and the world

Using Patterns of Recurring Climate Cycles to Predict Future Climate Changes

Abstract: The past is the key to the future—recurring cyclic patterns of the magnitude and intensity of climate changes in the geologic past can be used to predict future climate changes. The magnitude and exceedingly abrupt rate of change of climate changes in the late Pleistocene (∼20°F/century) were vastly greater than any climate changes that have occurred in recent centuries. Ice-core oxygen isotope and paleo-temperature data clearly show remarkable swings in climate over the past 100,000 years. In just the past 500 years, Greenland warming/cooling temperatures fluctuated back and forth about 40 times, with changes every 25–30 years (27 years on average). At least three warming events in the past 25,000 years were 20–24 times the magnitude of warming over the past century and four were 6–9 times the magnitude of warming over the past century. The magnitude of the only modern warming that might possibly have been caused by CO2 (1978–98) is insignificant compared to the earlier periods of warming. The Pacific Decadal Oscillation (PDO) shows excellent correlation with climate changes during the past century—two periods of global warming and three periods of global cooling exactly match switches in PDO. In 2000, I projected these cyclic patterns into the future and predicted 25–30 years of global cooling, and over the past 15 years, the climate has cooled slightly. As we enter a Solar Minimum strongly resembling the Dalton Minimum when strong global cooling occurred, we can expect further cooling.

Influence of altered low cloud parameterizations for seasonal variation of Arctic cloud amount on climate feedbacks

Abstract: This study investigates the alteration of climate feedbacks due to overestimated wintertime low-level cloud amount bias over the Arctic region (60°N–90°N) in a climate model. The climate feedback was quantitatively examined through radiative kernels that are pre-calculated radiative responses of climate variables to doubling of carbon dioxide concentration in NCAR Community Atmosphere Model version 3 (CAM3). Climate models have various annual cycle of the Arctic cloud amount at the low-level particularly with large uncertainty in winter and CAM3 may tend to overestimate the Arctic low-level cloud. In this study, the seasonal variation of low-level cloud amount was modified by reducing the wintertime cloud amount by up to 35 %, and then compared with the original without seasonal variation. Thus, we investigate how that bias may affect climate feedbacks and the projections of future Arctic warming. The results show that the decrease in low-level cloud amount slightly affected the radiation budgets because of a small amount of incident solar insolation in winter, but considerably changed water vapor and temperature profiles. Consequently, the most distinctive was decreases in water vapor feedback and contribution of heat transport (by −0.20 and −0.55 W m−2 K−1, respectively) and increases in the lapse rate feedback and cloud feedback (by 0.13 and 0.58 W m−2 K−1, respectively) during winter in this model experiment. This study suggests that the change in Arctic cloud amount effectively reforms the contributions of individual climate feedbacks to Arctic climate system and leads to opposing effects on different feedbacks, which cancel out in the model.

Investing in disaster risk management in an uncertain climate

Abstract: Climate change will exacerbate the challenges associated with weather variability and extremes in developing countries. As such, it reinforces the development case for investment in disaster risk management (DRM). Uncertainty about how climate change will affect particular locations makes optimal investment planning more difficult. In particular, our inability to derive meaningful probabilities from climate models limits the usefulness of standard project evaluation techniques such as cost–benefit analysis , that attempt to optimise risk–return trade-offs. This chapter offers a simple decision framework that enables policy-makers to identify the particular circumstances under which uncertainty about future climate change becomes critical for DRM investment decisions. Accounting for climate uncertainty is likely to shift the optimal balance of DRM strategies towards more flexible, low-regret-type interventions, especially those that promote ‘development-first’ or ‘risk-coping ’ objectives. Such investments are likely to confer additional development dividends, regardless of the climate future in a given location. The analysis also demonstrates that climate uncertainty does not necessarily motivate a “wait and see” approach. Instead, where opportunities exist to avail of adaptation co-benefits—for example where DRM initiatives could help avoid locking in future exposure to climate risk—climate uncertainty provides additional motivation for early investment in DRM.

Radiative forcing and feedback by forests in warm climates – a sensitivity study

Abstract: . We evaluate the radiative forcing of forests and the feedbacks triggered by forests in a warm, basically ice-free climate and in a cool climate with permanent high-latitude ice cover using the Max Planck Institute for Meteorology Earth System Model. As a paradigm for a warm climate, we choose the early Eocene, some 54 to 52 million years ago, and for the cool climate, the pre-industrial climate, respectively. To isolate first-order effects, we compare idealised simulations in which all continents are covered either by dense forests or by deserts with either bright or dark soil. In comparison with desert continents covered by bright soil, forested continents warm the planet for the early Eocene climate and for pre-industrial conditions. The warming can be attributed to different feedback processes, though. The lapse-rate and water-vapour feedback is stronger for the early Eocene climate than for the pre-industrial climate, but strong and negative cloud-related feedbacks nearly outweigh the positive lapse-rate and water-vapour feedback for the early Eocene climate. Subsequently, global mean warming by forests is weaker for the early Eocene climate than for pre-industrial conditions. Sea-ice related feedbacks are weak for the almost ice-free climate of the early Eocene, thereby leading to a weaker high-latitude warming by forests than for pre-industrial conditions. When the land is covered with dark soils, and hence, albedo differences between forests and soil are small, forests cool the early Eocene climate more than the pre-industrial climate because the lapse-rate and water-vapour feedbacks are stronger for the early Eocene climate. Cloud-related feedbacks are equally strong in both climates. We conclude that radiative forcing by forests varies little with the climate state, while most subsequent feedbacks depend on the climate state.

Strategic reasoning and bargaining in catastrophic climate change games

Abstract: Two decades of international negotiations show that agreeing on emission levels for climate change mitigation is a hard challenge. However, if early warning signals were to show an upcoming tipping point with catastrophic damage, theory and experiments suggest this could simplify collective action to reduce greenhouse gas emissions. At the actual threshold, no country would have a free-ride incentive to increase emissions over the tipping point, but it remains for countries to negotiate their emission levels to reach these agreements. We model agents bargaining for emission levels using strategic reasoning to predict emission bids by others and ask how this affects the possibility of reaching agreements that avoid catastrophic damage. It is known that policy elites often use a higher degree of strategic reasoning, and in our model this increases the risk for climate catastrophe. Moreover, some forms of higher strategic reasoning make agreements to reduce greenhouse gases unstable. We use empirically informed levels of strategic reasoning when simulating the model.

Heterogeneous Beliefs and Climate Catastrophes

Abstract: We study how heterogeneous beliefs about the causes and extent of global warming affect local mitigation and adaptation strategies and therefore global climate dynamics. Local policies are determined by expectations of policy makers about future climate. There are three types of expectations: strong skeptic, weak skeptic and ‘science-based’. Strong skeptics deny human-induced climate change and a possibility of a climate catastrophe. Weak skeptics believe that industrial emissions cause global warming, but deny catastrophic climate change. Science-based policy makers, considering the warning of the scientific community, account for both: human influence on climate and possible catastrophic shifts. Aggregate behavior of policy makers determines the total emission level which influences global climate dynamics. The paper argues that even if there are only skeptical policy makers the climate catastrophe can still be avoided.

Early Action on Hfcs Mitigates Future Atmospheric Change

Abstract: As countries take action to mitigate global warming, both by ratifying the UNFCCC Paris Agreement and enacting the Kigali Amendment to the Montreal Protocol to manage hydrofluorocarbons (HFCs), it is important to consider the relative importance of the pertinent greenhouse gases and the distinct structure of their atmospheric impacts, and how the timing of potential greenhouse gas regulations would affect future changes in atmospheric temperature and ozone. HFCs should be explicitly considered in upcoming climate and ozone assessments, since chemistry-climate model simulations demonstrate that HFCs could contribute substantially to anthropogenic climate change by the mid-21st century, particularly in the upper troposphere and lower stratosphere i.e., global average warming up to 0.19 K at 80 hPa. The HFC mitigation scenarios described in this study demonstrate the benefits of taking early action in avoiding future atmospheric change: more than 90% of the climate change impacts of HFCs can be avoided if emissions stop by 2030.

Climate Warming and Its Sensitivity to CO_2 Concentrations——Progress on “Climate Sensitivity” Group of CAS Strategic Priority Research Program “Climate Change: Carbon Budget and Relevant Issues”

Abstract: The increases in atmospheric concentrations of CO_2 and associated global warming are of worldwide concerns. In the 2009 Copenhagen Accord, many nations agreed to limit the increase in global temperature since pre-industrial times to below 2°C by initiating significant cuts in global emissions of greenhouse gases, assuming that the global warming of 2°C would occur if greenhouse gas concentrations rose above 450 ppm CO_2 equivalent by volume. Climate sensitivity(the ratio of change in global mean surface temperature to that in CO_2-equivalent concentration) is the scientific fundamental for policies to reduce emissions of greenhouse gases. To support the nation's mitigation and adaptation to climate change, a group of projects within the Chinese Academy of Sciences Strategic Priority Research Program of ‘Climate Change: Carbon Budget and Relevant Issues' examine the key factors that influence climate sensitivity, including natural variability of climate, the feedback of clouds and water vapor, the cooling effect of atmospheric aerosols, and the uncertainties associated with the global climate simulations. During the past four and a half years, the CAS scientists have improved the understanding of warming in China and climate sensitivity in the following aspects:(1) New time series of temperature are obtained and analyzed to understand the amplitude, rate, periodicity, and abrupt change of temperature in China. Time series of temperature for different regions over the past 2000 years are reconstructed based on datasets from tree rings, lake sediments, ice cores, coral, etc., and the time series of observed temperature from meteorological stations over the past 100 years are compiled. For climate series over the past 100 years, a homogenization approach is used to remove systematic biases in the observation series because of relocation of meteorological stations or changes in observation instruments, rules, and methods. The homogenized temperatures show that the average temperature over China increased by 1.52 oC(100 yr)-1, which is much higher than the global warming of 0.89 oC over 1901—2012.(2) Observational networks are launched to measure size-resolved speciated aerosol concentrations and optical properties of aerosols. The continuous measurements nationwide provide valuable datasets for studies of climatic effect of aerosols. Comparisons of simulated aerosol concentrations from climate models with measurements show that current aerosol-climate models worldwide generally underestimate aerosol concentrations in China, suggesting that the climate models might have underestimated the roles of aerosols in climate sensitivity.(3) The key parameterization schemes of cloud-aerosol-radiation and dynamic vegetation have been implemented into the CAS Earth System Model, which allow us to better quantify the feedbacks of clouds and water vapor in climate system.(4) The multi-model transient simulations of future climate indicate that, under the Intergovernmental Panel on Climate Change(IPCC)future emissions scenarios(the Representative Concentration Pathways, RCPs), the warming of 2°C would not occur under RCP2.6 and would likely occur when CO_2 equivalent concentrations are approximately 550 ppm under RCP4.5, RCP6.0, and RCP8.5.

Climate Change and Global Warming

Abstract: Why does climate change? How does climate change? This chapter describes flows of energy in the climate system. Climate can change when there are changes to energy flows between the different components of the climate system—internal changes. Climate can also change as a response to a change in total input or output energy—external changes. The energy budget of the planet is critical for understanding how the climate system may change over time, because on long timescales, climate is governed largely by the total amount of energy in the system and how that energy is stored and moves. Examples of interactions and internal feedbacks from past changes to the climate are described, and where the energy may go in the future is discussed.

Global Population and Public Health

Abstract: Although it took all of human history up until the 1800s for the global population to reach one billion, the most recent billion was added in a mere 12 years. This unprecedented growth in the global population has contributed to many serious moral problems, but arguably the most dire of these is climate change. The Earth’s atmosphere can only absorb so much greenhouse gas before it violently disrupts the climate, and the number of people on the planet make staying below that limit very difficult. In this chapter, I will argue that the relationship between the world’s population and the threat of catastrophic climate change entails that we have a global population crisis, and that the fact of this crisis constitutes a public health emergency.

My Climate Change

Abstract: Presented on March 27, 2018 from 3:00 p.m.-4:00 p.m. in the Reinsch-Pierce Family Auditorium, Architecture East Building, Georgia Tech.

The geopolitics of climate justice: collective interest or raison de système?

Abstract: If we fail to coordinate a systemic decarbonisation of the global economy sufficient to prevent runaway climate change, no amount of effort put towards adaptation will be sufficient. Our attention to the task of mitigation, which by itself must negotiate enormous geopolitical obstacles, requires priority if we are truly concerned with alleviating the human costs of climate change. This choice of framing of the human challenges we face from climate change, however, is at odds with the standard conception of climate justice, which seeks to provide reforms to the international legal and political order to address increasing systemic inequities. What these two perspectives have in common is the recognition that climate change necessitates systemic reforms to the international order. To the extent that international law can facilitate these reforms, the question seems to be how can we better enforce equitable international obligations. This commentary asserts that the distribution of costs and benefits inheren...

Climate Change Impacts, Adaptation and Policies for Agriculture in African Small States

Abstract: Climate change is arguably one of the leading developmental challenges of our time. Its ability to cut across national, social, economic and political boundaries means that it will invariably affect everyone on the planet, one way or another. Given that fact, concerted global efforts have been made to address climate change since the Rio Conference in 1992, through Kyoto in 1998, to the recent Paris Agreement in 2015. The Paris Agreement advocates strong and decisive action to reduce greenhouse gas emissions and arrest runaway climate change, while at the same time strengthening the resilience and adaptation of economic and livelihood systems.