Timescales Of Climate Change Research Articles

Multi-centennial evolution of the climate response and deep-ocean heat uptake in a set of abrupt stabilization scenarios with EC-Earth3

Abstract. Understanding long-term committed climate change due to anthropogenic forcing is key to informing climate policies, yet these timescales are still underexplored. We present here a set of 1000-year-long abrupt stabilization simulations performed with EC-Earth3. Each simulation follows a sudden stabilization of the external forcing at the level specified by CMIP6 for historical (1990) or SSP5-8.5 scenario (2025, 2050, 2065, 2080, 2100) conditions, with a final temperature increase ranging between 1.4 and 9.6 K with respect to the pre-industrial baseline. Remarkably, the simulation stabilized at a greenhouse gas (GHG) level close to the present day (2025) exceeds the Paris Agreement goals of 1.5 and 2° warming above pre-industrial in the long term, and only the 1990 simulation leads to a stabilized climate below 1.5° warming. We first focus on the evolution of the climate response at multi-centennial timescales and its dependence on the level of forcing. We note a decrease in the magnitude of the climate feedback parameter at longer timescales. Conversely, simulations with higher forcing exhibit a larger feedback parameter (in magnitude). Subsequently, the evolution of surface warming patterns over multi-centennial timescales is studied. While the response is generally consistent across simulations, some variations, particularly in the South Pacific and at high latitudes, suggest a certain level of state or forcing dependence. The patterns of precipitation change also evolve during the stabilization runs: the drying trends found in the subtropical oceans and in Mediterranean-like hotspots in the SSP5-8.5 scenario tend to be reduced or even reversed. We finally focus on the rate of heat storage in the global ocean, which is the main driver of the climate response at multi-centennial timescales. We find that the rate of warming of the deep ocean is almost independent from the amplitude of the forcing so that most of the additional heat remains in the upper layers at high forcing. This might be due – at least partly – to a decreased ventilation of the deep ocean, caused by changes in the Meridional Overturning Circulation (MOC). These results highlight the importance of studying multi-centennial timescales of climate change to better understand the response of the deep ocean, which will play a crucial role in determining the final state of the climate system once GHG concentrations are stabilized.

Inferring Northern Hemisphere Continental Warming Patterns from the Amplitude and Phase of the Seasonal Cycle in Surface Temperature

Abstract The seasonal cycle in temperature is a large and well-observed response to radiative forcing, suggesting its potential as a natural analog to human-caused climate change. Although there have been advances constraining some climate feedback parameters using seasonal observations, the seasonal cycle has not been used to inform about the local temperature sensitivity to greenhouse gas forcing. In this study, we uncover a nonlinear relationship between the amplitude and phase of the seasonal cycle and forced temperature trends in seven CMIP5-era large ensembles across the Northern Hemisphere extratropical continents. We develop a mixture energy balance model that reproduces this relationship and reveals the unexpected finding that the phasing of the seasonal cycle—in addition to the amplitude—contains information about local temperature sensitivity to seasonal forcing over land. Using this energy balance model framework, we compare the pattern and magnitude of the seasonally inferred sensitivity of the surface temperature response to anthropogenic radiative forcing. The seasonally constrained model largely reproduces the pattern of human-caused temperature trends seen in climate models (r = 0.81, p value < 0.01), including polar amplification, but the magnitude of the response is smaller by about a factor of 3. Our results show the relevance of both phasing and amplitude for constraining patterns of local feedbacks and suggest the utility of additional research to better understand the differences in sensitivity between seasonal and greenhouse gas forcing. Significance Statement Warming in response to increased greenhouse gases is not spatially uniform across land. We wanted to understand whether the familiar seasonal cycle in temperature could provide information about climate change. We found that climate models show a strong link between the seasonal cycle and future warming: places with a larger and more delayed temperature response to the seasonal cycle in solar forcing tend to warm more across the Northern Hemisphere midlatitudes. A very simple model for the climate system, whose parameters are based on the seasonal cycle, captures the pattern but not the magnitude of warming. Our findings suggest that there are some similarities between the processes that control temperature change on seasonal and climate change time scales, but that we must understand the difference between seasonal and longer-term sensitivity to warming before the seasonal cycle can be used to reduce uncertainty about climate change.

Revisiting the Potential to Narrow Model Uncertainty in the Projections of Arctic Runoff

AbstractDespite multiple advances in the understanding of the water cycle intensification in a warmer climate, climate models still diverge in their hydrological projections. Here we constrain annual runoff projections over individual and aggregated Arctic river basins. For this purpose, we use two ensembles of global climate models and two statistical methods: a regression scheme assuming similar runoff sensitivities at interannual versus climate change timescales, and a Bayesian method where models are used to derive a posterior runoff response conditioned on historical observations. While both techniques are shown to narrow model uncertainties, more or less substantially depending on rivers, the Bayesian method is less sensitive to the choice of the model ensemble and is more skillful when tested with synthetic observations. It has also been applied over the whole Arctic watershed, showing so far a limited narrowing of the inter‐model spread, but its skill will further improve with increasing climate change.

Probabilistic projections of the stability of small tidal inlets at century time scale using a reduced complexity approach

Climate change is widely expected to affect the thousands of small tidal inlets (STIs) dotting the global coastline. To properly inform effective adaptation strategies for the coastal areas in the vicinity of these inlets, it is necessary to know the temporal evolution of inlet stability over climate change time scales (50–100 years). As available numerical models are unable to perform continuous morphodynamic simulations at such time scales, here we develop and pilot a fast, probabilistic, reduced complexity model (RAPSTA – RAPid assessment tool of inlet STAbility) that can also quantify forcing uncertainties. RAPSTA accounts for the key physical processes governing STI stability and for climate change driven variations in system forcing. The model is very fast, providing a 100 year projection in less than 3 seconds. RAPSTA is demonstrated here at 3 STIs, representing the 3 main Types of STIs; Permanently open, locationally stable inlet (Type 1); Permanently open, alongshore migrating inlet (Type 2); Seasonally/Intermittently open, locationally stable inlet (Type 3). Model applications under a high greenhouse gas emissions scenario (RCP 8.5), accounting for forcing uncertainties, show that while the Type 1 STI will not change type over the twenty-first century, the Type 2 inlet may change into a more unstable Type 3 system around mid-century, and the Type 3 STI may change into a less unstable Type 2 system in about 20 years from now, further changing into a stable Type 1 STI around mid-century. These projections underscore the need for future adaptation strategies to remain flexible.

Implications of climate change for railway infrastructure

AbstractWeather phenomena can result in severe impacts on railway infrastructure. In future, projected changes to the frequency and/or intensity of extreme weather events could change weather–infrastructure risk profiles. Infrastructure owners and operators need to manage current weather impacts and put in place adequate plans to anticipate and adapt to changes in future weather risks, or mitigate the impacts arising from those risks. The assessment of the risk posed to railway infrastructure from current and future weather is dependent on a good understanding of the constituent components of risk: hazard, vulnerability, and exposure. A good understanding of the baseline and projected future risk is needed in order to understand the potential benefits of various climate change adaptation actions. Traditional risk assessment methods need some modification in order to be applied to climate change timescales, for which decisions need to be made under deep uncertainty. This review paper highlights some key challenges for assessing the risk, including: managing uncertainties; understanding weather‐impact relationships and how they could change with climate change; assessing the costs of current and future weather impacts and the potential cost versus benefit of adaptation; and understanding practices and tools for adapting railway infrastructure. The literature reveals examples of progress and good practice in all these areas, providing scope for effective knowledge‐sharing—across the railway infrastructure and other sectors—in support of infrastructure resilience and adaptation.This article is categorized under: Assessing Impacts of Climate Change > Evaluating Future Impacts of Climate Change

Meridional Migration of Eastern North Pacific Tropical Cyclogenesis: Joint Contribution of Interhemispheric Temperature Differential and ENSO

AbstractThis study finds that the meridional migration of tropical cyclogenesis (TCG) between June and November over the eastern North Pacific is mainly due to changes in the Hadley circulation and associated changes in the location of the intertropical convergence zone as modulated by ENSO and the interhemispheric temperature differential (ITD). These two factors are largely independent of each other and play significant and nearly equivalent roles in the meridional migration of TCG over the ENP from 1979 to 2018. Through the use of regression models, we find that the combination of these two factors has significant skill in capturing annual TCG meridional distribution over the ENP basin. June–October ENSO, as defined by Niño‐3.4, can be skillfully predicted with ∼1 season lead time, while ITD can be skillfully predicted ∼3 seasons in advance. This predictability allows for the potential for seasonal outlooks of TCG meridional movement over the ENP. The influence of ITD on TCG meridional migration over the ENP has repercussions on climate change timescales as well, due to the potential TCG meridional migration over the ENP in response to global warming. Under the Shared Socioeconomic Pathways 2–4.5 scenario, the ITD shows a robust increase among the 23 models of version 6 of the Coupled Model Intercomparison Project. However, the considerable uncertainty in the model response of ENSO to global warming reduces confidence in projections of TCG meridional migration over the ENP.

Considering the Role of Adaptive Evolution in Models of the Ocean and Climate System.

Numerical models have been highly successful in simulating global carbon and nutrient cycles in today's ocean, together with observed spatial and temporal patterns of chlorophyll and plankton biomass at the surface. With this success has come some confidence in projecting the century‐scale response to continuing anthropogenic warming. There is also increasing interest in using such models to understand the role of plankton ecosystems in past oceans. However, today's marine environment is the product of billions of years of continual evolution—a process that continues today. In this paper, we address the questions of whether an assumption of species invariance is sufficient, and if not, under what circumstances current model projections might break down. To do this, we first identify the key timescales and questions asked of models. We then review how current marine ecosystem models work and what alternative approaches are available to account for evolution. We argue that for timescales of climate change overlapping with evolutionary timescales, accounting for evolution may to lead to very different projected outcomes regarding the timescales of ecosystem response and associated global biogeochemical cycling. This is particularly the case for past extinction events but may also be true in the future, depending on the eventual degree of anthropogenic disruption. The discipline of building new numerical models that incorporate evolution is also hugely beneficial in itself, as it forces us to question what we know about adaptive evolution, irrespective of its quantitative role in any specific event or environmental changes.

Climate finance and disclosure for institutional investors: why transparency is not enough

The finance sector’s response to pressures around climate change has emphasized disclosure, notably through the recommendations of the Financial Stability Board’s Task Force on Climate-related Financial Disclosures (TCFD). The implicit assumption—that if risks are fully revealed, finance will respond rationally and in ways aligned with the public interest—is rooted in the “efficient market hypothesis” (EMH) applied to the finance sector and its perception of climate policy. For low carbon investment, particular hopes have been placed on the role of institutional investors, given the apparent matching of their assets and liabilities with the long timescales of climate change. We both explain theoretical frameworks (grounded in the “three domains”, namely satisficing, optimizing, and transforming) and use empirical evidence (from a survey of institutional investors), to show that the EMH is unsupported by either theory or evidence: it follows that transparency alone will be an inadequate response. To some extent, transparency can address behavioural biases (first domain characteristics), and improving pricing and market efficiency (second domain); however, the strategic (third domain) limitations of EMH are more serious. We argue that whilst transparency can help, on its own it is a very long way from an adequate response to the challenges of ‘aligning institutional climate finance’.

Contemporary Fiction vs. the Challenge of Imagining the Timescale of Climate Change

Fiction writers who try to do justice to the vast temporal and spatial scales and the enormous complexity of climate change are faced with the problem that the phenomenon exceeds human perception and that it is not dramatic in the traditional sense. In this article we explore the formal challenges that arise when fiction takes on the temporality of climate change by examining three very different novels that seek to capture the geological timescale. We analyze Richard McGuire’s time-bending graphic novel Here (2014), Dale Pendell’s fictional future history The Great Bay (2010), and Jeanette Winterson’s cautionary science-fiction tale The Stone Gods (2007) through the lens of Barbara Adam’s concept of the timescape, Rob Nixon’s idea of slow violence, and Timothy Clark’s notion of destructive doubles to see what kinds of literary innovations and translations the timescale of climate change has provoked. In doing so, we ponder Clark’s question, posed in his recent book Ecocriticism on the Edge: The Anthropocene as a Threshold Concept (2015), whether humans are constitutionally incapable of imagining the Anthropocene—the new geological epoch defined by the action of humans of which climate change is the most salient manifestation—or whether authors can adequately depict and convey it by disrupting conventional modes of representation. We conclude that while each of the three novels ultimately falls short in this regard, collectively they do chart possible pathways for successful literary treatment of the most pressing ecological threat of our time.

“Polyvalent Adaptation”: Design in a Temporal Context of Uncertain High-Risk Futures

If greenhouse gas emissions ceased today, sea levels will continue to rise for centuries due to the time scale of climate change. This demands a fundamental shift from solely mitigating impacts to adapting to this new reality. Architects can play a key role but are often restrained by outmoded disciplinary norms, and financial and regulatory limitations. What we require is a new design paradigm that extends beyond site-specific needs and draws on the context of our high-risk future. “Polyvalent Adaptation” could significantly impact the profession and the future of our communities. This approach combines two concepts that are not new to architecture or to discussions surrounding sustainability and climate change, but, when married, amplify each others’ potential. Combining the temporal concepts of polyvalence and adaptation provides a new lens for tackling the conflict between the permanence of the built environment and the changing climate. From this perspective, projects can be designed and constructed to meet current needs, to provide projective agency capable of assisting in the aftermath of extreme weather, and to become support infrastructures for new settlement patterns.

Challenging climate change and migration discourse: Different understandings of timescale and temporality in the Maldives

This article draws on ongoing research in the Maldives to explore differences between elite and non-elite perceptions of climate change and migration. It argues that, in addition to variations in perceptions based on diverse knowledge, priorities and agendas, there exists a more fundamental divergence based upon different understandings of the timescale of climate change and related ideas of urgency and crisis. Specifically, elites tend to focus on a distant future, which is generally abstracted from people's everyday lived realities, and to utilise the language of a climate change-induced migration ‘crisis’ in their discussions about impacts in a manner not envisaged by non-elites. The article concludes that, rather than unproblematically mapping global, external facing narratives wholesale onto ordinary people's lives and experiences, there needs to be more dialogue between elites and non-elites on climate change and migration issues. These perspectives should be integrated more effectively into the development of policy interventions designed to support people in adapting to the impacts of global environmental change.

A perspective on sustained marine observations for climate modelling and prediction.

Here, I examine some of the many varied ways in which sustained global ocean observations are used in numerical modelling activities. In particular, I focus on the use of ocean observations to initialize predictions in ocean and climate models. Examples are also shown of how models can be used to assess the impact of both current ocean observations and to simulate that of potential new ocean observing platforms. The ocean has never been better observed than it is today and similarly ocean models have never been as capable at representing the real ocean as they are now. However, there remain important unanswered questions that can likely only be addressed via future improvements in ocean observations. In particular, ocean observing systems need to respond to the needs of the burgeoning field of near-term climate predictions. Although new ocean observing platforms promise exciting new discoveries, there is a delicate balance to be made between their funding and that of the current ocean observing system. Here, I identify the need to secure long-term funding for ocean observing platforms as they mature, from a mainly research exercise to an operational system for sustained observation over climate change time scales. At the same time, considerable progress continues to be made via ship-based observing campaigns and I highlight some that are dedicated to addressing uncertainties in key ocean model parametrizations. The use of ocean observations to understand the prominent long time scale changes observed in the North Atlantic is another focus of this paper. The exciting first decade of monitoring of the Atlantic meridional overturning circulation by the RAPID-MOCHA array is highlighted. The use of ocean and climate models as tools to further probe the drivers of variability seen in such time series is another exciting development. I also discuss the need for a concerted combined effort from climate models and ocean observations in order to understand the current slow-down in surface global warming.

Hydrologic benchmarking of meteorological drought indices at interannual to climate change timescales: a case study over the Amazon and Mississippi river basins

Abstract. Widely used metrics of drought are still derived solely from analyses of meteorological variables such as precipitation and temperature. While drought is generally a consequence of atmospheric anomalies, the impacts to society are more directly related to hydrologic conditions. The present study uses a standardized runoff index (SRI) as a proxy for river discharge and as a benchmark for various meteorological drought indices (scPDSI, SPI, SPEI_th, and SPEI_hg respectively). Only 12-month duration droughts are considered in order to allow a direct (no river routing) comparison between meteorological anomalies and their hydrological counterpart. The analysis is conducted over the Mississippi and Amazon river basins, which provide two contrasted test beds for evaluating drought indices at both interannual (using detrended data) and climate change (using raw data) timescales. Looking first at observations over the second half of the 20th century, the simple SPI based solely on precipitation is no less suitable than more sophisticated meteorological drought indices at detecting interannual SRI variations. Using the detrended runoff and meteorological outputs of a five-member single model ensemble of historical and 21th century climate simulations leads to the same conclusion. Looking at the 21st century projections, the response of the areal fraction in drought to global warming is shown to be strongly metric dependent and potentially overestimated by the drought indices which account for temperature variations. These results suggest that empirical meteorological drought indices should be considered with great caution in a warming climate and that more physical water balance models are needed to account for the impact of the anthropogenic radiative forcings on hydrological droughts.

A multi-resolution approach to global ocean modeling

A new global ocean model (MPAS-Ocean) capable of using enhanced resolution in selected regions of the ocean domain is described and evaluated. Three simulations using different grids are presented. The first grid is a uniform high-resolution (15km) mesh; the second grid has similarly high resolution (15km) in the North Atlantic (NA), but coarse resolution elsewhere; the third grid is a variable resolution grid like the second but with higher resolution (7.5km) in the NA. Simulation results are compared to observed sea-surface height (SSH), SSH variance and selected current transports. In general, the simulations produce subtropical and subpolar gyres with peak SSH amplitudes too strong by between 0.25 and 0.40m. The mesoscale eddy activity within the NA is, in general, well simulated in both structure and amplitude. The uniform high-resolution simulation produces reasonable representations of mesoscale activity throughout the global ocean. Simulations using the second variable-resolution grid are essentially identical to the uniform case within the NA region. The third case with higher NA resolution produces a simulation that agrees somewhat better in the NA with observed SSH, SSH variance and transports than the two 15km simulations. The actual throughput, including I/O, for the x1-15km simulation is the same as the structured grid Parallel Ocean Program ocean model in its standard high-resolution 0.1° configuration. Our overall conclusion is that this ocean model is a viable candidate for multi-resolution simulations of the global ocean system on climate-change time scales.

Surface albedo feedbacks from climate variability and change

AbstractSnow and sea ice surface albedo feedback is evaluated in models from the World Climate Research Program Coupled Model Intercomparison Project phase 3 using the radiative “kernel” technique. A comparison is carried out between feedbacks at climate change timescales and those operating under seasonal, interannual, and decadal variability. A primary motivation is to examine possible relationships across these timescales. Similarities are found in the mean model meridional distribution of feedback, although uncertainties are large due to model spread and uncertainties from regressions. Climate change feedback appears stronger over the Arctic north of 75°N. Consistent with findings elsewhere, climate change feedback strengths over Northern Hemisphere (NH) snow and sea ice are uncorrelated, although a weak correlation is found between NH and Southern Hemisphere (SH) sea ice. By contrast, at other timescales, moderate positive correlations are found between NH snow and sea ice albedo feedbacks, as well as between NH and SH sea ice albedo feedbacks. Statistically significant correlations are not found between surface albedo feedbacks at climate change and other timescales, either for global feedback or for NH and SH sea ice. Notably, however, correlations are found for NH snow albedo feedback against both seasonal and interannual feedbacks. This suggests that NH snow albedo feedback is a “special case,” potentially revealing short‐term analogues appropriate for close comparison with climate change, with such relationships not holding for other components of the surface albedo feedback.

Conceptions of time in (paleo)climate science and some implications

AbstractPalaeoscientists of necessity deal with time as a fundamental part of the research process and have developed understandings within the discipline of how to deal with a range of timescales from the deep time of Archaean geology to recent time, that is the last few centuries. Time has however largely been seen as providing a chronology, the ability to place events in sequence and through the implementation of various dating techniques to relate these sequences across space, providing fundamental information toward understanding cause and effect within the Earth system. Variability in the units of time, the differences between radiometric and sidereal or calendrical years is accounted for and not deemed significant. When dealing with other disciplines, either through research into the relationship of past societies to climate change, or when contributing to the concerns over future directions of climate problems arise in attempting to communicate the nature of timescales. The real issue is to reinforce the idea of change as a basic quality of the climate system, something that can occur very rapidly. It is open to question whether a concentration on timescales of climate change is proving a distraction in terms of communication from the most important issue. Change is a fundamental property of the global climate system, and from our paleoscience knowledge it is clear that change will continue into the future and could well be very rapid. WIREs Clim Change 2012 doi: 10.1002/wcc.178This article is categorized under: Climate, History, Society, Culture > Disciplinary Perspectives

On atmospheric radiative feedbacks associated with climate variability and change

Using the method of radiative ‘kernels’ an analysis is made of water vapour, lapse rate and ‘Planck’ (uniform vertical temperature) long wave feedbacks in models participating in the World Climate Research Program (WCRP) Coupled Model Intercomparison Project phase 3 (CMIP3). Feedbacks are calculated at climate change timescales from the A1B scenario, and at three ‘variability’ timescales from the corresponding preindustrial experiments: seasonal, interannual and decadal. Surface temperature responses show different meridional patterns for the different timescales, which are then manifest in the structures of the individual feedbacks. Despite these differences, mean water vapour feedback strength in models is positive for all models and timescales, and of comparable global magnitude across all timescales except for seasonal, where it is much weaker. Taking into consideration the strong positive lapse rate feedback at seasonal timescales, combined water vapour/lapse rate feedback is indeed similar across all timescales. To a good approximation, global water vapour feedback is found to be well represented by the temperature response along with an assumption of unchanged relative humidity under both variability and climate change. A comparison is also made of model feedbacks with reanalysis derived feedbacks for seasonal and interannual timescales. No strong relationships between individual modelled feedbacks at different timescales are evident: i.e., strong feedbacks in models at variability timescales do not in general predict strong climate change feedback, with the possible exception of seasonal timescales. There are caveats on this (and other) findings however, from uncertainties associated with the kernel technique and from, at times, very large uncertainties in estimating variability related feedbacks from temperature regressions.

The contribution of timescales to the temperature response of climate models

Both the magnitude and timescale of climate change in response to anthropogenic forcing are important consideration in climate change decision making. Using a familiar, yet simple global energy balance model combined with a novel method for estimating the amount of gain in the global surface temperature response to radiative forcing associated with timescales in the range 100–103 years we show that the introduction of large-scale circulation such as meridional overturning leads to the emergence of discrete gain–timescale relationships in the dynamics of this model. This same feature is found in the response of both an intermediate complexity and two atmosphere–ocean general circulation models run to equilibrium. As a result of this emergent property of climate models, it is possible to offer credible partitioning of the full equilibrium gain of these models, and hence their equilibrium climate sensitivity, between two discrete timescales; one decadal associated with near surface ocean heat equilibration; and one centennial associated with deep ocean heat equilibration. Timescales of approximately 20 and 700 years with a 60:40 partitioning of the equilibrium gain are found for the models analysed here. A re-analysis of the emulation results of 19 AOGCMs presented by Meinshausen et al. (Atmos Chem Phys Discuss 8:6153–6272, 2008) indicates timescales of 20 and 580 years with an approximate 50:50 partition of the equilibrium gain between the two. This suggests near equal importance of both short and long timescales in determining equilibrium climate sensitivity.

Planning for Impacts of Climate Change at U.S. Ports

U.S. ports need to better understand climate change and how it may affect them. In the coming decades, ports are likely to experience higher sea levels and storm surges, as well as other direct and indirect impacts, due to climate change. Most ports do not appear to be thinking about, let alone actively preparing to address, the effects of climate change. Ports do not have specific information about either the types of impacts that they can expect on their facilities or the probabilities of different types of impacts occurring. Although climate change science is making considerable advances, projections of impacts at levels smaller than the regional scale are not available. In addition, ports’ typical planning processes are ill equipped to respond to the high levels of uncertainty associated with the impacts of climate change, the timescales of climate change, and the geographical scale of climate change. The data that ports typically use for planning purposes do not incorporate climate change forecasts. Some ports also believe that climate change does not pose an immediate threat to their facilities. However, several ports are beginning to think about how to prepare for climate change. These include the Port of Miami (Miami, Florida), the Port Authority of New York and New Jersey, the Massachusetts Port Authority, the Port of Seattle (Seattle, Washington), the Port of Corpus Christi (Corpus Christi, Texas), and the Georgia Ports Authority. To help these and other ports assess their risk, more and better data are needed, as well as better planning tools and methods.

Testing palaeo-environmental proxies in Jurassic belemnites: Mg/Ca, Sr/Ca, Na/Ca, δ 18O and δ 13C

We test the hypothesis that the noise in belemnite records through time results from changing climate. We do so by comparing palaeo-proxies (Mg/Ca, Sr/Ca, Na/Ca, δ 18O, δ 13C) in two species of Toarcian belemnites, Acrocoelites ( Odontobelus) vulgaris (14 specimens) and Acrocoelites ( Acrocoelites) subtenuis (10 specimens), deposited in a period of time that was short relative to the timescale of climate change. The specimens are interpreted to have been regurgitated from the stomach of a marine predator and so were deposited together in a geological instant of Early Jurassic time. In A. ( O.) vulgaris, isotopic and elemental palaeo-proxies group tightly, suggesting that this belemnite occupied a restricted environmental niche. In A. ( A.) subtenuis, elemental and isotopic compositions spread more widely, suggesting that this species occupied a greater range of habitats. Possible sexual dimorphism in A. ( O.) vulgaris is reflected in bimodal Mg/Ca and differing intra-rostral distribution of Mg in putative dimorphs; concentrations decline by 30% from apical line to rim in specimens with high Mg/Ca, but are largely invariant radially in specimens with lower Mg/Ca. Sexual dimorphism in A. ( A.) subtenuis yields a bimodality in size, Mg/Ca, and intra-rostral distribution of Mg; larger specimens have a higher Mg/Ca, and Mg concentrations that increase along radial traverses from apical line to rim, whilst the smaller specimens show a mid-rostral minimum in Mg concentration. Radial profiles of concentrations for Sr and Na vary little in all forms. Toarcian belemnites of these species thus show strong biofractionation effects on Mg/Ca, and little or no observable biofractionation of Sr/Ca or Na/Ca. It follows that much of the noise in belemnite records results from biofractionation, and from a cosmopolitan life-style of some belemnite species, rather than climate-change. For Toarcian belemnites, we suggest that Sr/Ca is the best indicator of palaeo-temperature.