Papers on anthropogenic global warming and next glaciation

This is a list of papers on anthropogenic global warming and next glaciation. List also contains some papers that discuss next glaciation more generally. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Impact of anthropogenic CO₂ on the next glacial cycle – Herrero et al. (2013) “The model of Paillard and Parrenin (Earth Planet Sci Lett 227(3–4):263–271, 2004) has been recently optimized for the last eight glacial cycles, leading to two different relaxation models with model-data correlations between 0.8 and 0.9 (García-Olivares and Herrero (Clim Dyn 1–25, 2012b)). These two models are here used to predict the effect of an anthropogenic CO₂ pulse on the evolution of atmospheric CO₂, global ice volume and Antarctic ice cover during the next 300 kyr. The initial atmospheric CO₂ condition is obtained after a critical data analysis that sets 1300 Gt as the most realistic carbon Ultimate Recoverable Resources (URR), with the help of a global compartmental model to determine the carbon transfer function to the atmosphere. The next 20 kyr will have an abnormally high greenhouse effect which, according to the CO₂ values, will lengthen the present interglacial by some 25 to 33 kyr. This is because the perturbation of the current interglacial will lead to a delay in the future advance of the ice sheet on the Antarctic shelf, causing that the relative maximum of boreal insolation found 65 kyr after present (AP) will not affect the developing glaciation. Instead, it will be the following insolation peak, about 110 kyr AP, which will find an appropriate climatic state to trigger the next deglaciation.” Carmen Herrero, Antonio García-Olivares, Josep L. Pelegrí, Climatic Change, December 2013, DOI: 10.1007/s10584-013-1012-0.

Determining the natural length of the current interglacial – Tzedakis et al. (2012) “No glacial inception is projected to occur at the current atmospheric CO₂ concentrations of 390 ppmv (ref. 1). Indeed, model experiments suggest that in the current orbital configuration—which is characterized by a weak minimum in summer insolation—glacial inception would require CO₂ concentrations below preindustrial levels of 280 ppmv (refs 2, 3, 4). However, the precise CO₂ threshold^{4, 5, 6} as well as the timing of the hypothetical next glaciation⁷ remain unclear. Past interglacials can be used to draw analogies with the present, provided their duration is known. Here we propose that the minimum age of a glacial inception is constrained by the onset of bipolar-seesaw climate variability, which requires ice-sheets large enough to produce iceberg discharges that disrupt the ocean circulation. We identify the bipolar seesaw in ice-core and North Atlantic marine records by the appearance of a distinct phasing of interhemispheric climate and hydrographic changes and ice-rafted debris. The glacial inception during Marine Isotope sub-Stage 19c, a close analogue for the present interglacial, occurred near the summer insolation minimum, suggesting that the interglacial was not prolonged by subdued radiative forcing⁷. Assuming that ice growth mainly responds to insolation and CO₂ forcing, this analogy suggests that the end of the current interglacial would occur within the next 1500 years, if atmospheric CO₂ concentrations did not exceed 240±5 ppmv.” P. C. Tzedakis, J. E. T. Channell, D. A. Hodell, H. F. Kleiven & L. C. Skinner, Nature Geoscience 5, 138–141(2012), doi:10.1038/ngeo1358. [Full text]

How can a glacial inception be predicted? – Crucifix (2011) “The Early Anthropogenic Hypothesis considers that greenhouse gas concentrations should have declined during the Holocene in absence of humankind activity, leading to glacial inception around the present. It partly relies on the fact that present levels of northern summer incoming solar radiation are close to those that, in the past, preceded a glacial inception phenomenon, associated with declines in greenhouse gas concentrations. However, experiments with various numerical models of glacial cycles show that next glacial inception may still be delayed by several tens of thousands of years, even with the assumption of a decline in greenhouse gas concentrations during the Holocene. Furthermore, as we show here, conceptual models designed to capture the gross dynamics of the climate system as a whole suggest also that small disturbances may sometimes cause substantial delays in glacial events, causing a fair level of unpredictability on ice age dynamics. This suggests the need for a validated mathematical description of climate system dynamics that allows us to quantify uncertainties on predictions. Here, it is proposed to organise our knowledge about the physics and dynamics of glacial cycles through a Bayesian inference network. Constraints on the physics and dynamics of climate can be encapsulated into a stochastic dynamical system. These constraints include, in particular, estimates of the sensitivity of the components of climate to external forcings, inferred from plans of experiments with large simulators of the atmosphere, oceans and ice sheets. On the other hand, palaeoclimate observations are accounted for through a process of parameter calibration. We discuss promises and challenges raised by this programme.” Michel Crucifix, The Holocene August 2011 vol. 21 no. 5 831-842, doi: 10.1177/0959683610394883. [Full text]

The impact of insolation, greenhouse gas forcing and ocean circulation changes on glacial inception – Vettoretti & Peltier (2011) “In this study we employ the NCAR CCSM3 coupled model to investigate the onset of high northern latitude perennial snow cover. Two periods of Earth’s insolation history, that of the pre-industrial period and that of 116 ka before present (BP), are used as benchmarks in an investigation of the influences of interglacial greenhouse gas (GHG) concentration and insolation upon the occurrence of permanent summer snow cover. An additional two experiments at 10 ka and 51 ka into the future (AP) using a typical interglacial GHG level are used to investigate the length of the current interglacial. Results from this set of multicentury sensitivity experiments demonstrate the relative importance of forcings due to insolation and atmospheric greenhouse gases at the millennial scale, and of Atlantic ocean overturning strength (AMOC) at the century scale. We find that while areas of perennial snow cover are sensitive to GHG concentrations, they are much more sensitive to the contemporaneous insolation regime. The goodness of fit of the climatology of the control model to the modern observed climatology is found to influence the modeling results. While there is a strong correlation between AMOC decadal variability and high latitude surface temperature in our control climates, we find little change in AMOC strength during our simulations of 116 ka BP climate nor do we find significant correlation between high latitude snow accumulation and the AMOC. Both the 10 ka AP and 51 ka AP future simulations produce inception events which are much stronger than that of the equivalent pre-industrial simulation. The simulation of inception at 10 ka into the future suggests a maximum duration of the current interglacial of approximately 20 ka in the absence of modern anthropogenic forcing.” G. Vettoretti, W.R. Peltier, The Holocene August 2011 vol. 21 no. 5 803-817, doi: 10.1177/0959683610394885.

A movable trigger: Fossil fuel CO₂ and the onset of the next glaciation – Archer & Ganopolski (2005) “The initiation of northern hemisphere ice sheets in the last 800 kyr appears to be closely controlled by minima in summer insolation forcing at 65°N. Beginning from an initial typical interglacial pCO₂ of 280 ppm, the CLIMBER-2 model initiates an ice sheet in the Northern Hemisphere when insolation drops 0.7 σ (standard deviation) or 15 W/m² below the mean. This same value is required to explain the history of climate using an orbitally driven conceptual model based on insolation and ice volume thresholds (Paillard, 1998). When the initial baseline pCO₂ is raised in CLIMBER-2, a deeper minimum in summertime insolation is required to nucleate an ice sheet. Carbon cycle models indicate that ∼25% of CO₂ from fossil fuel combustion will remain in the atmosphere for thousands of years, and ∼7% will remain beyond one hundred thousand years (Archer, 2005). We predict that a carbon release from fossil fuels or methane hydrate deposits of 5000 Gton C could prevent glaciation for the next 500,000 years, until after not one but two 400 kyr cycle eccentricity minima. The duration and intensity of the projected interglacial period are longer than have been seen in the last 2.6 million years.” David Archer, Andrey Ganopolski, Geochemistry, Geophysics, Geosystems, Volume 6, Issue 5, May 2005, DOI: 10.1029/2004GC000891. [Full text]

The Earth’s Climate in the Next Hundred Thousand years (100 kyr) – Berger et al. (2003) “One of the most striking features of the Quaternary paleoclimate records remains the so-called 100-kyr cycle which is undoubtedly linked to the future of our climate. Such a 100-kyr cycle is indeed characterised by long glacial periods followed by a short-interglacial (∼10–15 kyr long). As we are now in an interglacial, the Holocene, the previous one (the Eemian, which corresponds quite well to Marine Isotope Stage 5e, peaking at ∼125 kyr before present, BP) was assumed to be a good analogue for our present-day climate. In addition, as the Holocene is 10 kyr long, paleoclimatologists were naturally inclined to predict that we are quite close to the next ice age. Simulations using the 2-D climate model of Louvain-la-Neuve show, however, that the current interglacial will most probably last much longer than any previous ones. It is suggested here that this is related to the shape of the Earth’s orbit around the Sun, which will be almost circular over the next tens of thousands of years. As this is primarily related to the 400-kyr cycle of eccentricity, the best and closest analogue for such a forcing is definitely Marine Isotopic Stage 11 (MIS-11), some 400 kyr ago, not MIS-5e. Because the CO₂ concentration in the atmosphere also plays an important role in shaping long-term climatic variations – especially its phase with respect to insolation – a detailed reconstruction of this previous interglacial from deep sea and ice records is urgently needed. Such a study is particularly important in the context of the already exceptional present-day CO₂ concentrations (unprecedented over the past million years) and, even more so, because of even larger values predicted to occur during the 21st century due to human activities.” A. Berger, M. F. Loutre, M. Crucifix, Surveys in Geophysics, March 2003, Volume 24, Issue 2, pp 117-138. [Full text]

An Exceptionally Long Interglacial Ahead? – Berger & Loutre (2002) “Today’s comparatively warm climate has been the exception more than the rule during the last 500,000 years or more. If recent warm periods (or interglacials) are a guide, then we may soon slip into another glacial period. But Berger and Loutre argue in their Perspective that with or without human perturbations, the current warm climate may last another 50,000 years. The reason is a minimum in the eccentricity of Earth’s orbit around the Sun.” A. Berger, M. F. Loutre, Science 23 August 2002: Vol. 297 no. 5585 pp. 1287-1288, DOI: 10.1126/science.1076120. [Full text]

Future Climatic Changes: Are We Entering an Exceptionally Long Interglacial? – Loutre & Berger (2000) “Various experiments have been conducted using the Louvain-la-Neuve two-dimensional Northern Hemisphere climate model (LLN 2-D NH) to simulate climate for the next 130 kyr into the future. Simulations start with values representing the present-day Northern Hemisphere ice sheet, using different scenarios for future CO₂ concentrations. The sensitivity of the model to the initial size of the Greenland ice sheet, and to possible impacts of human activities, has also been tested. Most of the natural scenarios indicate that: (i) the climate is likely to experience a longlasting (∼50 kyr) interglacial; (ii) the next glacial maximum is expected to be most intense at around 100 kyr after present (AP), with a likely interstadial at ∼60 kyr AP; and (iii) after 100 kyr AP continental ice rapidly melts, leading to an ice volume minimum 20 kyr later. However, the amplitude and, to a lesser extent, the timing of future climatic changes depend on the CO₂ scenario and on the initial conditions related to the assumed present-day ice volume. According to our modelling experiments, man’s activities over the next centuries may significantly affect the ice-sheet’s behaviour for approximately the next 50 kyr. Finally, the existence of thresholds in CO₂ and insolation, earlier shown to be significant for the past, is confirmed to be also important for the future.” M. F. Loutre, A. Berger, Climatic Change, July 2000, Volume 46, Issue 1-2, pp 61-90, DOI 10.1023/A:1005559827189. [Full text]

The end of the present interglacial: how and when? – Broecker (1998) “Despite the large decline in Northern Hemisphere summer insolation during the last 8000 years, neither sea level nor polar temperatures have as yet undergone any significant downturn. This behavior is consistent with the prediction by Kukla and Matthews (1972) that the Holocene interglacial will terminate suddenly with a jump to another of the climate system’s modes of operation. This is what happened at the end of the last period of peak interglaciation. However, complicating the situation is evidence that ice sheet growth during the transition from marine stage 5e to 5d preceded the shut down of the Atlantic’s conveyor circulation which is thought to have brought Europe’s Eemian to a close. If so, then in the natural course of events, the end of the present interglaciation awaits the onset of icecap growth. However, it must be kept in mind that the ongoing buildup of greenhouse gases may alter the natural course of events. In particular, the warming and wetting of the planet will gradually reduce the density of surface waters in the regions where deep waters form. As this reduction is not likely to be symmetrical between the northern Atlantic and the margin of the Antarctic continent, the current near balance between deep water production in the north and south may be disrupted causing an abrupt reorganization of the ocean’s thermohaline circulation. Based on the paleoclimatic record, such a reorganization would have had a profound impact on the planet’s climate.” Broecker, W.S., Quaternary Science Reviews, Volume 17, Number 8, 1 August 1998 , pp. 689-694(6), DOI: http://dx.doi.org/10.1016/S0277-3791(98)00037-7. [Full text]

Summer solstice solar radiation, the 100 kyr Ice Age cycle, and the next Ice Age – Ledley (1995) “Modeling studies suggest that the summer solstice solar radiation is more important than the caloric half-year solar radiation in producing glacial/interglacial cycles because it is more representative of the energy available to melt ice during the short melt season. Here it is shown that the correlation between the summer solstice solar radiation and the rate of change of the oxygen isotope record is generally greater than that between the caloric half-year radiation and the rate of change of the oxygen isotope record. These results also suggest that the sawtoothed nature of the 100 kyr cycle may be produced by periods of relatively slow changes in ice volume, punctuated by periods of rapid growth that are initiated at times of extremely low summer solstice radiation; and that it is unlikely that an ice age will begin in the next 70 kyr.” Tamara Shapiro Ledley, Geophysical Research Letters, Volume 22, Issue 20, pages 2745–2748, 15 October 1995, DOI: 10.1029/95GL03027.

Possible effects of anthropogenically-increased CO₂ on the dynamics of climate: Implications for ice age cycles – Saltzman et al. (1993) “A dynamical model, developed to account for the observed major variations of global ice mass and atmospheric CO₂ during the late Cenozoic, is used to provide a quantitative demonstration of the possibility that the anthropogenically-forced increase of atmospheric CO₂, if maintained over a long period of time (perhaps by tectonic forcing), could displace the climatic system from an unstable regime of oscillating ice ages into a more stable regime representative of the pre-Pleistocene. This stable regime is characterized by orbitally-forced oscillations that are of much weaker amplitude than prevailed during the Pleistocene.” Barry Saltzman, Kirk A. Maasch, Mikhail Ya. Verbitsky, Geophysical Research Letters, Volume 20, Issue 11, pages 1051–1054, 7 June 1993, DOI: 10.1029/93GL01015.

Quaternary Research special issue: The end of the present interglacial – several authors, 24 papers (1972) Only abstracts are available for individual papers. Quaternary Research, Volume 2, Issue 3, Pages 261-445 (November 1972).