Articles | Volume 24, issue 4
https://doi.org/10.5194/acp-24-2679-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Special issue:
https://doi.org/10.5194/acp-24-2679-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Opinion: Can uncertainty in climate sensitivity be narrowed further?
Steven C. Sherwood
CORRESPONDING AUTHOR
Climate Change Research Centre, UNSW Sydney, Kensington, NSW 2052, Australia
Chris E. Forest
Department of Meteorology and Atmospheric Science, The Pennsylvania State University, University Park, PA 16802, USA
Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802, USA
Center for Earth System Modeling, Analysis, and Data, The Pennsylvania State University, University Park, PA, USA
Related authors
Sina Loriani, Yevgeny Aksenov, David Armstrong McKay, Govindasamy Bala, Andreas Born, Cristiano M. Chiessi, Henk Dijkstra, Jonathan F. Donges, Sybren Drijfhout, Matthew H. England, Alexey V. Fedorov, Laura Jackson, Kai Kornhuber, Gabriele Messori, Francesco Pausata, Stefanie Rynders, Jean-Baptiste Salée, Bablu Sinha, Steven Sherwood, Didier Swingedouw, and Thejna Tharammal
EGUsphere, https://doi.org/10.5194/egusphere-2023-2589, https://doi.org/10.5194/egusphere-2023-2589, 2023
Short summary
Short summary
In this work, we draw on paleoreords, observations and modelling studies to review tipping points in the ocean overturning circulations, monsoon systems and global atmospheric circulations. We find indications for tipping in the ocean overturning circulations and the West African monsoon, with potentially severe impacts on the Earth system and humans. Tipping in the other considered systems is considered conceivable but currently not sufficiently supported by evidence.
David Fuchs, Steven C. Sherwood, Abhnil Prasad, Kirill Trapeznikov, and Jim Gimlett
EGUsphere, https://doi.org/10.5194/egusphere-2023-1954, https://doi.org/10.5194/egusphere-2023-1954, 2023
Short summary
Short summary
Machine learning (ML) of unresolved processes offers many new possibilities for improving weather and climate models, but integrating ML into the models has been an engineering challenge, and there are performance issues. We present a new software framework for this integration, TorchClim, that is scalable, fast, and flexible, and thereby allows a new level of experimentation with the ML approach. We also provide guidance on ML training and demonstrate a skillful hybrid-ML atmosphere model.
Manuel Schlund, Axel Lauer, Pierre Gentine, Steven C. Sherwood, and Veronika Eyring
Earth Syst. Dynam., 11, 1233–1258, https://doi.org/10.5194/esd-11-1233-2020, https://doi.org/10.5194/esd-11-1233-2020, 2020
Short summary
Short summary
As an important measure of climate change, the Equilibrium Climate Sensitivity (ECS) describes the change in surface temperature after a doubling of the atmospheric CO2 concentration. Climate models from the Coupled Model Intercomparison Project (CMIP) show a wide range in ECS. Emergent constraints are a technique to reduce uncertainties in ECS with observational data. Emergent constraints developed with data from CMIP phase 5 show reduced skill and higher ECS ranges when applied to CMIP6 data.
Mia H. Gross, Markus G. Donat, Lisa V. Alexander, and Steven C. Sherwood
Earth Syst. Dynam., 11, 97–111, https://doi.org/10.5194/esd-11-97-2020, https://doi.org/10.5194/esd-11-97-2020, 2020
Short summary
Short summary
This study explores the amplified warming of cold extremes relative to average temperatures for both the recent past and future in the Northern Hemisphere and the possible physical processes that are driving this. We find that decreases in snow cover and
warmer-than-usual winds are driving the disproportionate rates of warming in cold extremes relative to average temperatures. These accelerated warming rates in cold extremes have implications for tourism, insect longevity and human health.
Yoko Tsushima, Florent Brient, Stephen A. Klein, Dimitra Konsta, Christine C. Nam, Xin Qu, Keith D. Williams, Steven C. Sherwood, Kentaroh Suzuki, and Mark D. Zelinka
Geosci. Model Dev., 10, 4285–4305, https://doi.org/10.5194/gmd-10-4285-2017, https://doi.org/10.5194/gmd-10-4285-2017, 2017
Short summary
Short summary
Cloud feedback is the largest uncertainty associated with estimates of climate sensitivity. Diagnostics have been developed to evaluate cloud processes in climate models. For this understanding to be reflected in better estimates of cloud feedbacks, it is vital to continue to develop such tools and to exploit them fully during the model development process. Code repositories have been created to store and document the programs which will allow climate modellers to compute these diagnostics.
Sina Loriani, Yevgeny Aksenov, David Armstrong McKay, Govindasamy Bala, Andreas Born, Cristiano M. Chiessi, Henk Dijkstra, Jonathan F. Donges, Sybren Drijfhout, Matthew H. England, Alexey V. Fedorov, Laura Jackson, Kai Kornhuber, Gabriele Messori, Francesco Pausata, Stefanie Rynders, Jean-Baptiste Salée, Bablu Sinha, Steven Sherwood, Didier Swingedouw, and Thejna Tharammal
EGUsphere, https://doi.org/10.5194/egusphere-2023-2589, https://doi.org/10.5194/egusphere-2023-2589, 2023
Short summary
Short summary
In this work, we draw on paleoreords, observations and modelling studies to review tipping points in the ocean overturning circulations, monsoon systems and global atmospheric circulations. We find indications for tipping in the ocean overturning circulations and the West African monsoon, with potentially severe impacts on the Earth system and humans. Tipping in the other considered systems is considered conceivable but currently not sufficiently supported by evidence.
David Fuchs, Steven C. Sherwood, Abhnil Prasad, Kirill Trapeznikov, and Jim Gimlett
EGUsphere, https://doi.org/10.5194/egusphere-2023-1954, https://doi.org/10.5194/egusphere-2023-1954, 2023
Short summary
Short summary
Machine learning (ML) of unresolved processes offers many new possibilities for improving weather and climate models, but integrating ML into the models has been an engineering challenge, and there are performance issues. We present a new software framework for this integration, TorchClim, that is scalable, fast, and flexible, and thereby allows a new level of experimentation with the ML approach. We also provide guidance on ML training and demonstrate a skillful hybrid-ML atmosphere model.
Manuel Schlund, Axel Lauer, Pierre Gentine, Steven C. Sherwood, and Veronika Eyring
Earth Syst. Dynam., 11, 1233–1258, https://doi.org/10.5194/esd-11-1233-2020, https://doi.org/10.5194/esd-11-1233-2020, 2020
Short summary
Short summary
As an important measure of climate change, the Equilibrium Climate Sensitivity (ECS) describes the change in surface temperature after a doubling of the atmospheric CO2 concentration. Climate models from the Coupled Model Intercomparison Project (CMIP) show a wide range in ECS. Emergent constraints are a technique to reduce uncertainties in ECS with observational data. Emergent constraints developed with data from CMIP phase 5 show reduced skill and higher ECS ranges when applied to CMIP6 data.
Mia H. Gross, Markus G. Donat, Lisa V. Alexander, and Steven C. Sherwood
Earth Syst. Dynam., 11, 97–111, https://doi.org/10.5194/esd-11-97-2020, https://doi.org/10.5194/esd-11-97-2020, 2020
Short summary
Short summary
This study explores the amplified warming of cold extremes relative to average temperatures for both the recent past and future in the Northern Hemisphere and the possible physical processes that are driving this. We find that decreases in snow cover and
warmer-than-usual winds are driving the disproportionate rates of warming in cold extremes relative to average temperatures. These accelerated warming rates in cold extremes have implications for tourism, insect longevity and human health.
Alex G. Libardoni, Chris E. Forest, Andrei P. Sokolov, and Erwan Monier
Adv. Stat. Clim. Meteorol. Oceanogr., 4, 19–36, https://doi.org/10.5194/ascmo-4-19-2018, https://doi.org/10.5194/ascmo-4-19-2018, 2018
Short summary
Short summary
We present new probabilistic estimates of model parameters in the MIT Earth System Model using more recent data and an updated method. Model output is compared to observed climate change to determine which sets of model parameters best simulate the past. In response to increasing surface temperatures and accelerated heat storage in the ocean, our estimates of climate sensitivity and ocean diffusivity are higher. Using a new interpolation algorithm results in smoother probability distributions.
Alex G. Libardoni, Chris E. Forest, Andrei P. Sokolov, and Erwan Monier
Geosci. Model Dev., 11, 3313–3325, https://doi.org/10.5194/gmd-11-3313-2018, https://doi.org/10.5194/gmd-11-3313-2018, 2018
Short summary
Short summary
We present a transparent method for evaluating how changes to the MIT Earth System Model impact its response to anthropogenic and natural forcings. We tested the effects that changes to both model components and forcings have on the estimates of model parameters that agree with historical observations. Overall, changes to model forcings are more important than the new components, while the long-term model response is unchanged. The methodology serves as a guide for documenting model development.
Yoko Tsushima, Florent Brient, Stephen A. Klein, Dimitra Konsta, Christine C. Nam, Xin Qu, Keith D. Williams, Steven C. Sherwood, Kentaroh Suzuki, and Mark D. Zelinka
Geosci. Model Dev., 10, 4285–4305, https://doi.org/10.5194/gmd-10-4285-2017, https://doi.org/10.5194/gmd-10-4285-2017, 2017
Short summary
Short summary
Cloud feedback is the largest uncertainty associated with estimates of climate sensitivity. Diagnostics have been developed to evaluate cloud processes in climate models. For this understanding to be reflected in better estimates of cloud feedbacks, it is vital to continue to develop such tools and to exploit them fully during the model development process. Code repositories have been created to store and document the programs which will allow climate modellers to compute these diagnostics.
E. Monier, J. R. Scott, A. P. Sokolov, C. E. Forest, and C. A. Schlosser
Geosci. Model Dev., 6, 2063–2085, https://doi.org/10.5194/gmd-6-2063-2013, https://doi.org/10.5194/gmd-6-2063-2013, 2013
M. Eby, A. J. Weaver, K. Alexander, K. Zickfeld, A. Abe-Ouchi, A. A. Cimatoribus, E. Crespin, S. S. Drijfhout, N. R. Edwards, A. V. Eliseev, G. Feulner, T. Fichefet, C. E. Forest, H. Goosse, P. B. Holden, F. Joos, M. Kawamiya, D. Kicklighter, H. Kienert, K. Matsumoto, I. I. Mokhov, E. Monier, S. M. Olsen, J. O. P. Pedersen, M. Perrette, G. Philippon-Berthier, A. Ridgwell, A. Schlosser, T. Schneider von Deimling, G. Shaffer, R. S. Smith, R. Spahni, A. P. Sokolov, M. Steinacher, K. Tachiiri, K. Tokos, M. Yoshimori, N. Zeng, and F. Zhao
Clim. Past, 9, 1111–1140, https://doi.org/10.5194/cp-9-1111-2013, https://doi.org/10.5194/cp-9-1111-2013, 2013
Related subject area
Subject: Climate and Earth System | Research Activity: Atmospheric Modelling and Data Analysis | Altitude Range: Troposphere | Science Focus: Physics (physical properties and processes)
Simulation of ozone–vegetation coupling and feedback in China using multiple ozone damage schemes
Interannual Variations in Siberian Carbon Uptake and Carbon Release Period
Significant human health co-benefits of mitigating African emissions
Opinion: Optimizing climate models with process-knowledge, resolution, and AI
Global scenarios of anthropogenic mercury emissions
Impact of Asian aerosols on the summer monsoon strongly modulated by regional precipitation biases
Water vapour exchange between the atmospheric boundary layer and free troposphere over eastern China: seasonal characteristics and the El Niño–Southern Oscillation anomaly
General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path
Assessing methane emissions from collapsing Venezuelan oil production using TROPOMI
Future reduction of cold extremes over East Asia due to thermodynamic and dynamic warming
Strong aerosol cooling alone does not explain cold-biased mid-century temperatures in CMIP6 models
Investigation of the climatology of low-level jets over North America in a high-resolution WRF simulation
Air pollution reductions caused by the COVID-19 lockdown open up a way to preserve the Himalayan glaciers
Modeling atmosphere–land interactions at a rainforest site – a case study using Amazon Tall Tower Observatory (ATTO) measurements and reanalysis data
Jiachen Cao, Xu Yue, and Mingrui Ma
Atmos. Chem. Phys., 24, 3973–3987, https://doi.org/10.5194/acp-24-3973-2024, https://doi.org/10.5194/acp-24-3973-2024, 2024
Short summary
Short summary
We implemented two widely used ozone damage schemes into a same regional model. Although the two schemes yielded distinct ozone vegetation damages, they predicted similar feedbacks to surface air temperature and ozone air quality in China. Our results highlighted the significance of ozone pollution control given its detrimental impacts on ecosystem functions, contributions to global warming, and amplifications of ozone pollution through ozone–vegetation coupling.
Dieu Anh Tran, Christoph Gerbig, Christian Rödenbeck, and Sönke Zaehle
EGUsphere, https://doi.org/10.5194/egusphere-2023-2573, https://doi.org/10.5194/egusphere-2023-2573, 2024
Short summary
Short summary
The analysis of atmospheric CO2 record from the Zotino Tall Tower Observatory (ZOTTO) in central Siberia highlights significant increases in the length and amplitude of the CO2 uptake and release in the 2010–2021period. The trend shows a stronger increase in carbon release amplitude compared to the uptake, suggesting that despite enhanced growing season uptake, during this period climate warming did not elevate the annual net CO2 uptake, as cold season respirations also responded to the warming.
Christopher D. Wells, Matthew Kasoar, Majid Ezzati, and Apostolos Voulgarakis
Atmos. Chem. Phys., 24, 1025–1039, https://doi.org/10.5194/acp-24-1025-2024, https://doi.org/10.5194/acp-24-1025-2024, 2024
Short summary
Short summary
Human-driven emissions of air pollutants, mostly caused by burning fossil fuels, impact both the climate and human health. Millions of deaths each year are caused by air pollution globally, and the future trends are uncertain. Here, we use a global climate model to study the effect of African pollutant emissions on surface level air pollution, and resultant impacts on human health, in several future emission scenarios. We find much lower health impacts under cleaner, lower-emission futures.
Tapio Schneider, L. Ruby Leung, and Robert C. J. Wills
EGUsphere, https://doi.org/10.5194/egusphere-2024-20, https://doi.org/10.5194/egusphere-2024-20, 2024
Short summary
Short summary
This paper lays out an approach to achieve substantial progress in climate modeling, balancing increases in resolution with advances in process-based modeling and the use of AI to learn from Earth observations.
Flora Maria Brocza, Peter Rafaj, Robert Sander, Fabian Wagner, and Jenny M. Jones
EGUsphere, https://doi.org/10.5194/egusphere-2024-41, https://doi.org/10.5194/egusphere-2024-41, 2024
Short summary
Short summary
To understand how atmospheric mercury levels will change in the future, we model how our Hg releases will change following developments in human energy use, mercury use, as well as our efforts in reducing pollution and battling climate change. This study models human Hg emissions until 2050, using different narratives of future developments which influence Hg emissions, such as energy use, climate policy and sector-specific pollution reduction measures for mercury and traditional air pollutants.
Zhen Liu, Massimo Bollasina, and Laura Wilcox
EGUsphere, https://doi.org/10.5194/egusphere-2023-3136, https://doi.org/10.5194/egusphere-2023-3136, 2024
Short summary
Short summary
The aerosol impact on monsoon precipitation and circulation is strongly influenced by a model simulated spatiotemporal variability of the climatological monsoon precipitation across Asia, which critically modulates the efficacy of aerosol-cloud-precipitation interactions, the predominant driver of the total aerosol response. There is a strong interplay between South and East Asia monsoon precipitation biases and their relative predominance in driving the overall monsoon response.
Xipeng Jin, Xuhui Cai, Xuesong Wang, Qianqian Huang, Yu Song, Ling Kang, Hongsheng Zhang, and Tong Zhu
Atmos. Chem. Phys., 24, 259–274, https://doi.org/10.5194/acp-24-259-2024, https://doi.org/10.5194/acp-24-259-2024, 2024
Short summary
Short summary
This work presents a climatology of water vapour exchange flux between the atmospheric boundary layer (ABL) and free troposphere (FT) over eastern China. The water vapour exchange maintains ABL humidity in cold months and moistens the FT in warm seasons, and its distribution has terrain-dependent features. The exchange flux is correlated with the El Niño–Southern Oscillation (ENSO) index and precipitation pattern. The study provides new insight into moisture transport and extreme weather.
Johannes Mülmenstädt, Edward Gryspeerdt, Sudhakar Dipu, Johannes Quaas, Andrew S. Ackerman, Ann M. Fridlind, Florian Tornow, Susanne E. Bauer, Andrew Gettelman, Yi Ming, Youtong Zheng, Po-Lun Ma, Hailong Wang, Kai Zhang, Matthew W. Christensen, Adam C. Varble, L. Ruby Leung, Xiaohong Liu, David Neubauer, Daniel G. Partridge, Philip Stier, and Toshihiko Takemura
EGUsphere, https://doi.org/10.5194/egusphere-2024-4, https://doi.org/10.5194/egusphere-2024-4, 2024
Short summary
Short summary
Human activities release copious amounts of small particles, called aerosols, into the atmosphere. These particles change how much sunlight clouds reflect to space, an important human perturbation of the climate whose magnitude is highly uncertain. We found that the latest climate models show a negative correlation but a positive causal relationship between aerosols and cloud water. This means we need to be very careful when we interpret observational studies that can only see correlation.
Brian Nathan, Joannes D. Maasakkers, Stijn Naus, Ritesh Gautam, Mark Omara, Daniel J. Varon, Melissa P. Sulprizio, Alba Lorente, Tobias Borsdorff, Robert J. Parker, and Ilse Aben
EGUsphere, https://doi.org/10.5194/egusphere-2023-2887, https://doi.org/10.5194/egusphere-2023-2887, 2023
Short summary
Short summary
As oil infrastructure around Lake Maracaibo in Venezuela deteriorates, significant methane leaks become likely. We perform an analysis that combines inventory estimates and TROPOMI satellite observations for 2018–2020 over Lake Maracaibo, as well as for Venezuela as a whole for 2019 using a different atmospheric model in order to provide context. Our findings may indicate significant, persistent leaks around the Lake Maracaibo region that are independent of the recent drop in oil production.
Donghuan Li, Tianjun Zhou, Youcun Qi, Liwei Zou, Chao Li, Wenxia Zhang, and Xiaolong Chen
EGUsphere, https://doi.org/10.5194/egusphere-2023-2806, https://doi.org/10.5194/egusphere-2023-2806, 2023
Short summary
Short summary
Two sets of climate model simulations are used to investigate the dynamic and thermodynamic factors to future change of cold extreme in East Asia. Dynamic factor accounted for over 80% of cold-month temperature anomalies in past 50 years. The intensity of cold extreme is expected to decrease by 5℃, with thermodynamic factor contributing about 75% by the end of the 21st century. Changes in dynamic factor are driven by an upward trend of positive Arctic Oscillation-like sea level pressure pattern.
Clare Marie Flynn, Linnea Huusko, Angshuman Modak, and Thorsten Mauritsen
Atmos. Chem. Phys., 23, 15121–15133, https://doi.org/10.5194/acp-23-15121-2023, https://doi.org/10.5194/acp-23-15121-2023, 2023
Short summary
Short summary
The latest-generation climate models show surprisingly cold mid-20th century global-mean temperatures, often despite exhibiting more realistic late 20th/early 21st century temperatures. A too-strong aerosol forcing in many models was thought to the be primary cause of these too-cold mid-century temperatures, but this was found to only be a partial explanation. This also partly undermines the hope to construct a strong relationship between the mid-century temperatures and aerosol forcing.
Xiao Ma, Yanping Li, Zhenhua Li, and Fei Huo
EGUsphere, https://doi.org/10.5194/egusphere-2023-2342, https://doi.org/10.5194/egusphere-2023-2342, 2023
Short summary
Short summary
This research studies the climatological attributes of low-level jets (LLJs) across North America using a 4km simulation. The study identifies significant LLJ systems such as the Great Plains LLJs. It also provides insights into less adequately represented LLJ systems by coarser models, such as the Quebec Northerly LLJ and small-scale low-level wind maxima around the Rocky Mountains. Additionally, the study investigates three distinct LLJs' diverse physical mechanisms driving their formation.
Suvarna Fadnavis, Bernd Heinold, T. P. Sabin, Anne Kubin, Katty Huang, Alexandru Rap, and Rolf Müller
Atmos. Chem. Phys., 23, 10439–10449, https://doi.org/10.5194/acp-23-10439-2023, https://doi.org/10.5194/acp-23-10439-2023, 2023
Short summary
Short summary
The influence of the COVID-19 lockdown on the Himalayas caused increases in snow cover and a decrease in runoff, ultimately leading to an enhanced snow water equivalent. Our findings highlight that, out of the two processes causing a retreat of Himalayan glaciers – (1) slow response to global climate change and (2) fast response to local air pollution – a policy action on the latter is more likely to be within the reach of possible policy action to help billions of people in southern Asia.
Amelie U. Schmitt, Felix Ament, Alessandro C. de Araújo, Marta Sá, and Paulo Teixeira
Atmos. Chem. Phys., 23, 9323–9346, https://doi.org/10.5194/acp-23-9323-2023, https://doi.org/10.5194/acp-23-9323-2023, 2023
Short summary
Short summary
Tall vegetation in forests affects the exchange of heat and moisture between the atmosphere and the land surface. We compared measurements from the Amazon Tall Tower Observatory to results from a land surface model to identify model shortcomings. Our results suggest that soil temperatures in the model could be improved by incorporating a separate canopy layer which represents the heat storage within the forest.
Cited articles
Andrews, T., Bodas-Salcedo, A., Gregory, J. M., Dong, Y., Armour, K. C., Paynter, D., Lin, P., Modak, A., Mauritsen, T., Cole, J. N. S., Medeiros, B., Benedict, J. J., Douville, H., Roehrig, R., Koshiro, T., Kawai, H., Ogura, T., Dufresne, J.-L., Allan, R. P., and Liu, C.: On the Effect of Historical SST Patterns on Radiative Feedback, J. Geophys. Res., 127, 36675, https://doi.org/10.1029/2022JD036675, 2022. a
Andronova, N. and Schlesinger, M.: Objective estimation of the probability density function for climate sensitivity, J. Geophys. Res., 106, 22605–22611, https://doi.org/10.1029/2000JD000259, 2001. a
Arrhenius, S.: On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground, Phil. Mag., 41, 237–276, 1896. a
Brown, R. M., Chalk, T. B., Crocker, A. J., Wilson, P. A., and Foster, G. L.: Late Miocene cooling coupled to carbon dioxide with Pleistocene-like climate sensitivity, Nat. Geosci., 15, 664+, https://doi.org/10.1038/s41561-022-00982-7, 2022. a
Ceppi, P. and Nowack, P.: Observational evidence that cloud feedback amplifies global warming, P. Nat. Acad. Sci. USA, 118, e2026290118, https://doi.org/10.1073/pnas.2026290118, 2021. a
Chao, L.-W., Muller, J. C., and Dessler, A. E.: Impacts of the Unforced Pattern Effect on the Cloud Feedback in CERES Observations and Climate Models, Geophys. Res. Lett., 49, 96299, https://doi.org/10.1029/2021GL096299, 2022. a
Charney, J., Arakawa, A., Baker, D. J., Bolin, B., Dickenson, R. E., Goody, R. M., Leith, C. E., Stommel, H. M., and Wunsch, C. I.: Carbon Dioxide and Climate:A scientific assessment, Tech. rep., National Academy of Sciences, Woods Hole, MA, https://doi.org/10.17226/12181, 34 pp., 1979. a, b
Dvorak, M. T., Armour, K. C., Frierson, D. M. W., Proistosescu, C., Baker, M. B., and Smith, C. J.: Estimating the timing of geophysical commitment to 1.5 and 2.0 degrees C of global warming, Nat. Clim. Change, 12, 547+, https://doi.org/10.1038/s41558-022-01372-y, 2022. a
Edwards, T. L., Crucifix, M., and Harrison, S. P.: Using the past to constrain the future: how the palaeorecord can improve estimates of global warming, Prog. Phys. Geog., 31, 481–500, 2007. a
Gleckler, P. J., Durack, P. J., Stouffer, R. J., Johnson, G. C., and Forest, C. E.: Industrial-era global ocean heat uptake doubles in recent decades, Nat. Clim. Change, 6, 394–398, https://doi.org/10.1038/nclimate2915, 2016. a
Grose, M. R., Gregory, J., Colman, R., and Andrews, T.: What Climate Sensitivity Index Is Most Useful for Projections?, Geophys. Res. Lett., 45, 1559–1566, https://doi.org/10.1002/2017GL075742, 2018. a
Hall, A., Cox, P., Huntingford, C., and Klein, S.: Progressing emergent constraints on future climate change, Nat. Clim. Change, 9, 269–278, https://doi.org/10.1038/s41558-019-0436-6, 2019. a
Harding, S.: “Strong objectivity”: a response to the new objectivity question, Synthese, 104, 331–349, 1995. a
Heede, U. K. and Fedorov, A. V.: Eastern equatorial Pacific warming delayed by aerosols and thermostat response to CO2 increase, Nat. Clim. Change, 11, 696+, https://doi.org/10.1038/s41558-021-01101-x, 2021. a, b
Hegerl, G. C. and Wallace, J. M.: Influence of Patterns of Climate Variability on the Difference between Satellite and Surface Temperature Trends, J. Climate, 15, 2412–2428, 2002. a
Knutti, R., Stocker, T., Joos, F., and Plattner, G.: Constraints on radiative forcing and future climate change from observations and climate model ensembles, Nature, 416, 719–723, https://doi.org/10.1038/416719a, 2002. a
Kramer, R. J., Soden, B. J., and Pendergrass, A. G.: Evaluating Climate Model Simulations of the Radiative Forcing and Radiative Response at Earth’s Surface, J. Climate, 32, 4089–4102, https://doi.org/10.1175/JCLI-D-18-0137.1, 2019. a
Kramer, R. J., He, H., Soden, B. J., Oreopoulos, L., Myhre, G., Forster, P. M., and Smith, C. J.: Observational Evidence of Increasing Global Radiative Forcing, Geophys. Res. Lett., 48, e2020GL091585, https://doi.org/10.1029/2020GL091585, 2021. a
Kuma, P., Bender, F. A.-M., Schuddeboom, A., McDonald, A. J., and Seland, Ø.: Machine learning of cloud types in satellite observations and climate models, Atmos. Chem. Phys., 23, 523–549, https://doi.org/10.5194/acp-23-523-2023, 2023. a
Lewis, N.: Objectively combining climate sensitivity evidence, Clim. Dyn., 60, 3139–3165, https://doi.org/10.1007/s00382-022-06468-x, 2022. a
Li, Q., England, M. H., Hogg, A. M., Rintoul, S. R., and Morrison, A. K.: Abyssal ocean overturning slowdown and warming driven by Antarctic meltwater, Nature, 615, 841–847, 2023. a
Libardoni, A. G., Forest, C. E., Sokolov, A. P., and Monier, E.: Underestimating Internal Variability Leads to Narrow Estimates of Climate System Properties, Geophys. Res. Lett., 46, 10000–10007, https://doi.org/10.1029/2019GL082442, 2019. a, b
Loeb, N. G., Wang, H., Allan, R. P., Andrews, T., Armour, K., Cole, J. N. S., Dufresne, J.-L., Forster, P., Gettelman, A., Guo, H., Mauritsen, T., Ming, Y., Paynter, D., Proistosescu, C., Stuecker, M. F., Willen, U., and Wyser, K.: New Generation of Climate Models Track Recent Unprecedented Changes in Earth's Radiation Budget Observed by CERES, Geophys. Res. Lett., 47, 86705, https://doi.org/10.1029/2019GL086705, 2020. a
Mahowald, N. M., Li, L., Albani, S., Hamilton, D. S., and Kok, J. F.: Opinion: The importance of historical and paleoclimate aerosol radiative effects, Atmos. Chem. Phys., 24, 533–551, https://doi.org/10.5194/acp-24-533-2024, 2024. a
Meehl, G. A., Hu, A., Castruccio, F., England, M. H., Bates, S. C., Danabasoglu, G., McGregor, S., Arblaster, J. M., Xie, S.-P., and Rosenbloom, N.: Atlantic and Pacific tropics connected by mutually interactive decadal-timescale processes, Nat. Geosci., 14, 36–43, https://doi.org/10.1038/s41561-020-00669-x, 2021. a
Myers, T. A., Scott, R. C., Zelinka, M. D., Klein, S. A., Norris, J. R., and Caldwell, P. M.: Observational constraints on low cloud feedback reduce uncertainty of climate sensitivity, Nat. Clim. Change, 11, 501–507, 2021. a
PALAEOSENS Project Members: Making sense of palaeoclimate sensitivity, Nature, 491, 683–691, 2012. a
Peixoto, J. P. and Oort, A. H.: Physics of Climate, American Institute of Physics, New York, 1992. a
Raghuraman, S. P., Paynter, D., Menzel, R., and Ramaswamy, V.: Forcing, cloud feedbacks, cloud masking, and internal variability in the cloud radiative effect satellite record, J. Climate, 36, 1–38, https://doi.org/10.1175/JCLI-D-22-0555.1, 2023. a, b
Renoult, M., Annan, J. D., Hargreaves, J. C., Sagoo, N., Flynn, C., Kapsch, M.-L., Li, Q., Lohmann, G., Mikolajewicz, U., Ohgaito, R., Shi, X., Zhang, Q., and Mauritsen, T.: A Bayesian framework for emergent constraints: case studies of climate sensitivity with PMIP, Clim. Past, 16, 1715–1735, https://doi.org/10.5194/cp-16-1715-2020, 2020. a
Scafetta, N.: Advanced Testing of Low, Medium, and High ECS CMIP6 GCM Simulations Versus ERA5-T2m, Geophys. Res. Lett., 49, 97716, https://doi.org/10.1029/2022GL097716, 2022. a, b
Seltzer, A. M., Blard, P.-H., Sherwood, S. C., and Kageyama, M.: Terrestrial amplification of past, present, and future climate change, Sci. Adv., 9, eadf8119, https://doi.org/10.1126/sciadv.adf8119, 2023. a
Senior, C. A. and Mitchell, J. F. B.: The time-dependence of climate sensitivity, Geophys. Res. Lett., 27, 2685–2688, 2000. a
Sherwood, S. C., Sen Gupta, A., and Schwartz, S. E.: Probability of committed warming exceeding 1.5 °C and 2.0 °C Paris targets, Environ. Res. Lett., 17, 064022, https://doi.org/10.1088/1748-9326/ac6ff6, 2022. a, b
Sherwood, S. C., Webb, M. J., Annan, J. D., Armour, K. C., Forster, P. M., Hargreaves, J. C., Hegerl, G., Klein, S. A., Marvel, K. D., Rohling, E. J., Watanabe, M., Andrews, T., Braconnot, P., Bretherton, C. S., Foster, G. L., Hausfather, Z., Heydt, A. S., Knutti, R., Mauritsen, T., Norris, J. R., Proistosescu, C., Rugenstein, M., Schmidt, G. A., Tokarska, K. B., and Zelinka, M. D.: An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence, Rev. Geophys., 58, https://doi.org/10.1029/2019RG000678, 2020. a
Smith, C. J., Forster, P. M., Allen, M., Fuglestvedt, J., Millar, R. J., Rogelj, J., and Zickfeld, K.: Current fossil fuel infrastructure does not yet commit us to 1.5 °C warming, Nat. Commun., 10, 101, https://doi.org/10.1038/s41467-018-07999-w, 2019. a
Sokolov, A. P. and Stone, P. H.: A flexible climate model for use in integrated assessments, Clim. Dynam., 14, 291–303, 1998. a
Stainforth, D. A., Allen, M. R., Tredger, E. R., and Smith, L. A.: Confidence, uncertainty and decision-support relevance in climate predictions, Phil. Trans. Royal Soc. A, 365, 2145–2161, https://doi.org/10.1098/rsta.2007.2074, 2007. a
Stauffer, C. L. and Wing, A. A.: Properties, Changes, and Controls of Deep-Convecting Clouds in Radiative-Convective Equilibrium, J. Adv. Model. Earth Sys., 14, e2021MS002917, https://doi.org/10.1029/2021MS002917, 2022. a
von der Heydt, A. S., Dijkstra, H. A., van de Wal, R. S. W., Caballero, R., Crucifix, M., Foster, G. L., Huber, M., Köhler, P., Rohling, E., Valdes, P. J., Ashwin, P., Bathiany, S., Berends, T., van Bree, L. G. J., Ditlevsen, P., Ghil, M., Haywood, A. M., Katzav, J., Lohmann, G., Lohmann, J., Lucarini, V., Marzocchi, A., Pälike, H., Baroni, I. R., Simon, D., Sluijs, A., Stap, L. B., Tantet, A., Viebahn, J., and Ziegler, M.: Lessons on Climate Sensitivity From Past Climate Changes, Curr. Clim. Change Rep., 2, 148–158, 2016. a
Wall, C. J., Norris, J. R., Possner, A., McCoy, D. T., McCoy, I. L., and Lutsko, N. J.: Assessing effective radiative forcing from aerosol-cloud interactions over the global ocean, P. Nat. Acad. Sci. USA, 119, https://doi.org/10.1073/pnas.2210481119, 2022a. a
Wall, C. J., Storelvmo, T., Norris, J. R., and Tan, I.: Observational Constraints on Southern Ocean Cloud-Phase Feedback, J. Climate, 35, 5087–5102, https://doi.org/10.1175/JCLI-D-21-0812.1, 2022b. a
Williams, A. I. L., Stier, P., Dagan, G., and Watson-Parris, D.: Strong control of effective radiative forcing by the spatial pattern of absorbing aerosol, Nat. Clim. Change, 12, 735+, https://doi.org/10.1038/s41558-022-01415-4, 2022. a
Wunderling, N., Staal, A., Sakschewski, B., Hirota, M., Tuinenburg, O. A., Donges, J. F., Barbosa, H. M. J., and Winkelmann, R.: Recurrent droughts increase risk of cascading tipping events by outpacing adaptive capacities in the Amazon rainforest, P. Nat. Acad. Sci. USA, 119, e2120777119, https://doi.org/10.1073/pnas.2120777119, 2022. a
Zhu, J., Otto-Bliesner, B. L., Brady, E. C., Poulsen, C. J., Tierney, J. E., Lofverstrom, M., and DiNezio, P.: Assessment of Equilibrium Climate Sensitivity of the Community Earth System Model Version 2 Through Simulation of the Last Glacial Maximum, Geophys. Res. Lett., 48, 91220, https://doi.org/10.1029/2020GL091220, 2021. a
Zhu, J., Otto-Bliesner, B. L., Brady, E. C., Gettelman, A., Bacmeister, J. T., Neale, R. B., Poulsen, C. J., Shaw, J. K., McGraw, Z. S., and Kay, J. E.: LGM Paleoclimate Constraints Inform Cloud Parameterizations and Equilibrium Climate Sensitivity in CESM2, J. Adv. Model. Earth Sys., 14, e2021MS002776, https://doi.org/10.1029/2021MS002776, 2022. a, b
Executive editor
Equilibrium climate sensitivity (ECS), with a specific definition, has been used as a convenient measure, encapsulated in a single number, of the response of the climate to increases in long-lived greenhouse gases. The authors recall some of the history of how ECS has been estimated, by models and observations, including paleoclimate data and note recent progress in reducing uncertainty in the value of ECS. However they also note that there are important aspects of future potential climate change that are not captured by the ECS measure and therefore that there will be limited usefulness in too strong a focus on reducing uncertainty in ECS alone.
Equilibrium climate sensitivity (ECS), with a specific definition, has been used as a convenient...
Short summary
The most fundamental parameter used to gauge the severity of future climate change is the so-called equilibrium climate sensitivity, which measures the warming that would ultimately occur due to a doubling of atmospheric carbon dioxide levels. Due to recent advances it is now thought to probably lie in the range 2.5–4 °C. We discuss this and the issues involved in evaluating and using the number, pointing to some pitfalls in current efforts but also possibilities for further progress.
The most fundamental parameter used to gauge the severity of future climate change is the...
Special issue
Altmetrics
Final-revised paper
Preprint