copenlu/druid huggingface dataset:
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2020-10-05): The wide range of estimates of climate sensitivity is driven by uncertainties in climate feedbacks, including how water vapour, clouds, surface reflectivity and other factors will change as the Earth warms. Climate feedbacks are processes that may amplify (positive feedbacks) or diminish (negative feedbacks) the effect of warming from increased CO2 concentrations or other climate forcings – factors that initially drive changes in the climate. [...] Climate models give a wide range of sensitivity estimates, so researchers often examine subsets of climate models – selected based on how well they match different present-day observations of the climate. These are referred to here as "constrained models". [...] Climate models provide a wide range of climate sensitivity estimates. The CMIP5 models featured in the most recent IPCC report have ECS values ranging from 2.1C to 4.7C per doubling, with an average sensitivity of 3.1C.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2020-07-22): There are a number of definitions of climate sensitivity in the literature, varying depending on what is included, and how easy they are to calculate and to apply. There isn’t one definition that is perfect for each application, and so there is always a need to translate between them. For the sake of practicality and to not preclude increases in scope in climate models, this paper focuses on the Effective Climate Sensitivity (Gregory et al, 2004) (based on the 150 yr response to an abrupt change to 4 times CO2), which is a little smaller than the Equilibrium Climate Sensitivity in most climate models (Dunne et al, 2020). It can allow for a wider range of feedbacks than the standard Charney sensitivity, but limits the very long term feedbacks because of its focus on the first 150 years of the response. [...] As many have remarked, some (but not all) reputable models have come out with surprisingly high climate sensitivities, and in comparison with the likely range proposed here, about a dozen go beyond 4.5 K. Should they therefore be ruled out completely? No, or at least not yet. There may be special combinations of features that allow these models to match the diverse observations while having such a high sensitivity. While it may not be likely that they will do so, they should however be tested to see whether or not they do. That means that it is very important that these models are used for paleo-climate runs, or at least idealised versions of them, as well as the standard historical simulations.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2020-07-22): The study, which was organised by the World Climate Research Programme (WCRP) and involving many leading climate scientists (including one of us: Tim), looks at a measure called "equilibrium climate sensitivity". This refers to how much global average temperatures will increase by in the long-term following a doubling of carbon dioxide concentrations. It can be estimated using three main lines of evidence: [...] The latest climate models have a wide range of climate sensitivities, with our own Met Office models at the high end. This happens because climate sensitivity is not something that scientists input to the models, but rather it emerges from the same complex interactions the models simulate. [...] The new study allows a key aspect of climate models, their climate sensitivity, to be seen in the context of other evidence. While there is still more to be done to assess more precisely how the global climate will respond to further increases in greenhouse gases, these advances provide a much more solid base of evidence on which climate change policy can be further developed.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2021-02-15): Global climate models predict warming in response to increasing GHG concentrations, partly due to decreased tropical low-level cloud cover and reflectance. We use satellite observations that discriminate stratocumulus from shallow cumulus clouds to separately evaluate their sensitivity to warming and constrain the tropical contribution to low-cloud feedback. We find an observationally inferred low-level cloud feedback two times smaller than a previous estimate. Shallow cumulus clouds are insensitive to warming, whereas global climate models exhibit a large positive cloud feedback in shallow cumulus regions. In contrast, stratocumulus clouds show sensitivity to warming and the tropical inversion layer strength, controlled by the tropical Pacific sea surface temperature gradient. Models fail to reproduce the historical sea surface temperature gradient trends and therefore changes in inversion strength, generating an overestimate of the positive stratocumulus cloud feedback. Continued weak east Pacific warming would therefore produce a weaker low-cloud feedback and imply a more moderate climate sensitivity (3.47 ± 0.33 K) than many models predict. [...] Zelinka, M. D. et al. Causes of higher climate sensitivity in CMIP6 models. Geophys. Res. Lett.47, e2019GL085782 (2020). Andrews, T., Gregory, J. M. & Webb, M. J. The dependence of radiative forcing and feedback on evolving patterns of surface temperature change in climate models. J. Clim.28, 1630–1648 (2015).
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2012-04-12): Origins of differences in climate sensitivity, forcing and feedback in climate models [...] We diagnose climate feedback parameters and CO2 forcing including rapid adjustment in twelve atmosphere/mixed-layer-ocean ("slab") climate models from the CMIP3/CFMIP-1 project (the AR4 ensemble) and fifteen parameter-perturbed versions of the HadSM3 slab model (the PPE). In both ensembles, differences in climate feedbacks can account for approximately twice as much of the range in climate sensitivity as differences in CO2 forcing. In the AR4 ensemble, cloud effects can explain the full range of climate sensitivities, and cloud feedback components contribute four times as much as cloud components of CO2 forcing to the range. Non-cloud feedbacks are required to fully account for the high sensitivities of some models however. The largest contribution to the high sensitivity of HadGEM1 is from a high latitude clear-sky shortwave feedback, and clear-sky longwave feedbacks contribute substantially to the highest sensitivity members of the PPE. Differences in low latitude ocean regions (30°N/S) contribute more to the range than those in mid-latitude oceans (30–55°N/S), low/mid latitude land (55°N/S) or high latitude ocean/land (55–90°N/S), but contributions from these other regions are required to account fully for the higher model sensitivities, for example from land areas in IPSL CM4.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2015-11-19): How sensitive is the earth to carbon dioxide? It’s a question that’s at the heart of climate science. [...] Climate sensitivity is the warming we can expect when the concentration of carbon dioxide in the atmosphere reaches double what it was in preindustrial times. [...] Climate sensitivity estimates using climate models support the higher end of the IPCC’s likely range. Such estimates are rooted in the behaviour of known physical processes but contain large uncertainties, such as the interaction of aerosols with clouds.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2021-05-19): Short-lived climate forcers have long-term climate impacts via the carbon–climate feedback [...] where \(\alpha \equiv \Delta T_A/\Delta C_A\) is the sensitivity of climate to atmospheric CO2 (in a unit of K GtC−1), which represents the change in temperature in response to a change in CO2 concentration7,19. The α is a useful measure to quantify the feedbacks between climate and carbon cycle over both preindustrial and industrial periods. The \({\mathrm{TCRE}} \equiv \Delta T_A/\Delta C_E\) is transient climate response to cumulative CO2 emission (in a unit of K GtC−1)20, which quantifies the ratio of change in temperature to cumulative carbon emissions, providing another useful measure to estimate the total allowable emissions for a given temperature change, as there is a near-linear relationship between cumulative CO2 emissions and global temperature change20.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2013-02-06): Sensitivity of tropical carbon to climate change constrained by carbon dioxide variability [...] The release of carbon from tropical forests may exacerbate future climate change1, but the magnitude of the effect in climate models remains uncertain2. Coupled climate–carbon-cycle models generally agree that carbon storage on land will increase as a result of the simultaneous enhancement of plant photosynthesis and water use efficiency under higher atmospheric CO2 concentrations, but will decrease owing to higher soil and plant respiration rates associated with warming temperatures3. At present, the balance between these effects varies markedly among coupled climate–carbon-cycle models, leading to a range of 330 gigatonnes in the projected change in the amount of carbon stored on tropical land by 2100. Explanations for this large uncertainty include differences in the predicted change in rainfall in Amazonia4,5 and variations in the responses of alternative vegetation models to warming6. Here we identify an emergent linear relationship, across an ensemble of models7, between the sensitivity of tropical land carbon storage to warming and the sensitivity of the annual growth rate of atmospheric CO2 to tropical temperature anomalies8. Combined with contemporary observations of atmospheric CO2 concentration and tropical temperature, this relationship provides a tight constraint on the sensitivity of tropical land carbon to climate change.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2017-09-04): Short-lived climate forcers have long-term climate impacts via the carbon–climate feedback [...] Huneeus, N. et al. Forcings and feedbacks in the GeoMIP ensemble for a reduction in solar irradiance and increase in CO2 . J. Geophys. Res. Atmos.119, 5226–5239 (2014). [...] Manabe, S. & Stouffer, R. J. Sensitivity of a global climate model to an increase of CO2 concentration in the atmosphere. J. Geophys. Res.85, 5529–5554 (1980).
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2017-05-23): Climate models are based on physical processes and our understanding of how the climate system works. Their sensitivity to CO2 is in line with estimates based on modern observations and records of past climate changes. Unsupported: There is no evidence that climate models systematically overestimate the climate’s sensitivity to CO2. Rather, independent lines of research produces sensitivity estimates consistent with models. [...] The statement that climate models overestimate the warming in response to CO2 is incorrect; it is based on either too short time periods that are dominated by natural variability, by the comparison of models with datasets that do not have global coverage, by comparing to models that were run many years ago with emissions and forcings that differed from what actually happened, by the use of oversimplified energy balance models1, or a combination of it. Recent studies have shown that once the changes in climate feedbacks over time2, datasets with full coverage are considered3 and all forcings are considered, the agreement between predicted and observed warming is excellent, even over the recent hiatus period4.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2017-02-09): Heartland Institute report’s claim that climate models are too sensitive to CO2 does not reflect evidence
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2024-04-06): The increase of carbon-dioxide-doubling-induced warming (climate sensitivity) in the latest climate models is primarily attributed to a larger extratropical cloud feedback. This is thought to be partly driven by a greater ratio of supercooled liquid-phase clouds to all clouds, termed liquid phase ratio. We use an instrument simulator approach to show that this ratio has increased in the latest climate models and is overestimated rather than underestimated as previously thought. In our analysis of multiple models, a greater ratio corresponds to stronger negative cloud feedback, in contradiction with single-model-based studies. We trace this unexpected result to a cloud feedback involving a shift from supercooled to warm clouds as climate warms, which corresponds to greater cloud amount and optical depth and weakens the extratropical cloud feedback. Better constraining this ratio in climate models – and thus this supercooled cloud feedback – impacts their climate sensitivities by up to 1 ˚C and reduces inter-model spread. [...] Zelinka, M. D. et al. Causes of higher climate sensitivity in CMIP6 Models. Geophys. Res. Lett.47, 1–12 (2020). [...] Qin, Y., Zelinka, M. D. & Klein, S. A. On the correspondence between atmosphere-only and coupled simulations for radiative feedbacks and forcing from CO2. J. Geophys. Res. Atmos.127, e2021JD035460 (2022).
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2022-03-24): Creating a fair and effective global arena for market-based solutions to climate change requires attention to all the ways that forests affect climate, including the biophysical effects. Future metrics of forest climate impacts should consider the effects of deforestation beyond CO2. Only recently have modelers begun to include BVOC. Doing so means that the albedo of intact forests (or the atmosphere above them) is higher due to the creation of SOA and subsequent cloud formation. Modeled deforestation thus results in less of a change in albedo, reducing the biophysical cooling effect. Similarly, accounting for the ozone and methane effects of BVOC reduces the biogeochemical warming from deforestation (Scott et al., 2018). In addition, especially in the tropics, deforestation reduces the strength of the soil CH4 sink (Dutaur and Verchot, 2007). While a small change relative to the atmospheric pool of CH4 (the second most important greenhouse gas), the loss of this sink is equivalent to approximately 13% of the current rate of increase in atmospheric CH4 (Saunois et al., 2016). We already have the data (Figure 5) to begin conceptualizing measures to coarsely scale CO2 impacts of forest change by latitude.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2023-11-15): Community-systemic issues are systematic errors shared by multiple diverse climate models (e.g., across CMIP ESMs) and are typically due to a community-wide issue related to the absence, or manner of treatment, of one or more physical processes. [...] Similarly, OMIP-like ocean-only experiments that systematically change out only the observed wind stress for the CanESM5 wind stress are not definitive: the specification of other surface forcing from observations (e.g., surface air temperature and SSS) carries with it the imprint of observed sea-ice distributions, and the lack of coupled feedbacks suppresses the true effect that wind stress bias would have in the coupled model. [...] Zelinka, M. D., Myers, T. A., McCoy, D. T., Po-Chedley, S., Caldwell, P. M., Ceppi, P., Klein, S. A., and Taylor, K. E.: Causes of Higher Climate Sensitivity in CMIP6 Models, Geophys. Res. Lett., 47, e2019GL085782, https://doi.org/10.1029/2019GL085782, 2020. a, b
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2023-11-20): Failed Fact Checks - Work requirements "have been proven to help impoverished families move from dependency to self-sufficiency." – MOSTLY FALSE - "Model outputs published in successive IPCC reports since 1990 project a doubling of CO2 could cause warming of up to 6°C by 2100. Instead, global warming ceased around the end of the twentieth century and was followed (since 1997) by 19 years of stable temperature. Earth has not warmed significantly for the past 18 years despite an 8 percent increase in atmospheric CO2." – INACCURATE - "[climate models] systematically over-estimate the sensitivity of climate to carbon dioxide … and modelers exclude forcings and feedbacks that run counter to their mission." – INCORRECT - "Solar forcings are not too small to explain twentieth century warming. In fact, their effect could be equal to or greater than the effect of CO2 in the atmosphere." – INCORRECT - "Forward projections of solar cyclicity imply the next few decades may be marked by global cooling rather than warming, despite continuing CO2emissions." – INCORRECT - Wildfires were worse in the early part of the 1900s than they are today – Mostly False - "NOAA makes it official.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2021-05-05): Prof. John Christy incorrectly claims to show climate models are too sensitive to carbon dioxide CLAIM the real atmosphere is less sensitive to CO2 than what has been forecast by climate models [...] Heartland Institute report’s claim that climate models are too sensitive to CO2 does not reflect evidence
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2017-04-28): GCMs systematically over-estimate the sensitivity of climate to carbon dioxide (CO2), many known forcings and feedbacks are poorly modeled, and modelers exclude forcings and feedbacks that run counter to their mission to find a human influence on climate. Doubling the concentration of atmospheric CO2 from its pre-industrial level, in the absence of other forcings and feedbacks, would likely cause a warming of ~0.3°C to 1.1°C, almost 50 percent of which must already have occurred.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2005-01-15): In a more systematic evaluation of the sensitivity of a model to cloud parameterization, Mitchell et al. (1987) and later Senior and Mitchell (1993) examined the response of a GCM model to a doubling of CO2 when different versions of a cloud parameterization were employed in the same model. The results of their studies are summarized in Fig. 13 showing a sequence of global warming predictions as different feedbacks are systematically introduced. The first estimate corresponds to the warming in the absence of feedback, the next with water vapor feedback added, the third with snow/ice albedo feedbacks added to water vapor feedback and finally the case when cloud feedback is added. Senior and Mitchell (1993) found that the presence and absence of microphysical and optical thickness feedbacks, which were permitted in different versions of the parameterizations, produce a range in warming between 1.9° and 5.4°C. Yao and Del Genio (2002) also reported that the 2 × CO2 sensitivity of the Goddard Institute for Space Studies (GISS) GCM was similarly dependent on the details of the moist convection and large-scale cloud parameterizations. [...] The sensitivity of coupled ocean–atmospheric models to cloud feedbacks differs from the sensitivity of models with fixed SSTs (e.g., Ma et al. 1994; Williams et al. 2003; and also acknowledged in Cess and Potter 1988). CMIP (Meehl et al. 2000), under the auspices of the World Climate Research Program (WCRP) Working Group on Coupled Models (WGCM) was created specifically to examine and compare coupled models forced by 1% yr−1 increases in CO2.
Claim: [climate models] systematically over-estimate the sensitivity of climate to carbon dioxide ... and modelers exclude forcings and feedbacks that run counter to their mission (Craig Idso, Robert Carter, S. Fred Singer, 2017-05-23)
Evidence (2019-12-14): In the years since the 5th Assessment Report, the uncertainty has grown. The latest climate model results – prepared for the forthcoming IPCC 6th Assessment Report – shows that a majority of the climate models are producing values of ECS exceeding 5oC. The addition of poorly understood additional processes into the models has increased confusion and uncertainty. At the same time, refined efforts to determine values of the equilibrium climate sensitivity from the historical data record obtain values of ECS about 1.6oC, with a range from 1.05 to 2.7oC. [...] To further complicate climate model projections for the 21st century, the climate models focus only on manmade climate change – they make no attempt to predict natural climate variations from the sun’s output, volcanic eruptions and long-term variations in ocean circulation patterns. We have no idea how natural climate variability will play out in the 21st century, and whether or not natural variability will dominate over manmade warming.