Modelling the Anthropocene

[AbruptSLR]

The linked reference provides insights in the more effective development of World-Earth models for projecting climate change during the Anthropocene:

Donges, J. F., Lucht, W., Heitzig, J., Barfuss, W., Cornell, S. E., Lade, S. J., and Schlüter, M.: Taxonomies for structuring models for World-Earth system analysis of the Anthropocene: subsystems, their interactions and social-ecological feedback loops, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-27, in review, 2018.

https://www.earth-syst-dynam-discuss.net/esd-2018-27/

Abstract. In the Anthropocene, social processes have become critical to understanding planetary-scale Earth system dynamics. The conceptual foundations of Earth system modelling have externalised social processes in ways that now hinder progress in understanding Earth resilience and informing governance of global environmental change. New approaches to global modelling are needed to address these challenges, but the current modelling landscape is highly diverse and heterogeneous, ranging from purely biophysical Earth System Models, to hybrid macro-economic Integrated Assessments Models, to a plethora of models of socio-cultural dynamics. World-Earth models, currently not yet available, will need to integrate all these elements, so future World-Earth modellers require a structured approach to identify, classify, select, and combine model components. Here, we develop taxonomies for ordering the multitude of societal and biophysical subsystems and their interactions. We suggest three taxa for modelled subsystems: (i) biophysical, where dynamics is usually represented by natural laws of physics, chemistry or ecology (i.e., the usual components of Earth system models), (ii) socio-cultural, dominated by processes of human behaviour, decision making and collective social dynamics (e.g., politics, institutions, social networks), and (iii) socio-metabolic, dealing with the material interactions of social and biophysical subsystems (e.g., human bodies, natural resource and agriculture). We show how higher-order taxonomies for interactions between two or more subsystems can be derived, highlighting the kinds of social-ecological feedback loops where new modelling efforts need to be directed. As an example, we apply the taxonomy to a stylised World-Earth system model of socially transmitted discount rates in a greenhouse gas emissions game to illustrate the effects of social-ecological feedback loops that are usually not considered in current modelling efforts. The proposed taxonomy can contribute to guiding the design and operational development of more comprehensive World-Earth models for understanding Earth resilience and charting sustainability transitions within planetary boundaries and other future trajectories in the Anthropocene.

[AbruptSLR]

Advanced Earth Systems Models need to do a better job of addressing uncertainties associated with land cover conversion:

Vittorio, et al. (2018), "Quantifying the Effects of Historical Land Cover Conversion Uncertainty on Global Carbon and Climate Estimates", Geophysical Research Letters, doi:10.1002/2017gl075124.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017GL075124

Abstract: "Previous studies have examined land use change as a driver of global change, but the translation of land use change into land cover conversion has been largely unconstrained. Here we quantify the effects of land cover conversion uncertainty on the global carbon and climate system using the integrated Earth System Model. Our experiments use identical land use change data and vary land cover conversions to quantify associated uncertainty in carbon and climate estimates. Land cover conversion uncertainty is large, constitutes a 5 ppmv range in estimated atmospheric CO2 in 2004, and generates carbon uncertainty that is equivalent to 80% of the net effects of CO2 and climate and 124% of the effects of nitrogen deposition during 1850–2004. Additionally, land cover uncertainty generates differences in local surface temperature of over 1°C. We conclude that future studies addressing land use, carbon, and climate need to constrain and reduce land cover conversion uncertainties."

[AbruptSLR]

Progress is slowly being made to overcome the computational bottleneck associated with state-of-the-art ESMs:

Fuhrer, O., Chadha, T., Hoefler, T., Kwasniewski, G., Lapillonne, X., Leutwyler, D., Lüthi, D., Osuna, C., Schär, C., Schulthess, T. C., and Vogt, H.: Near-global climate simulation at 1 km resolution: establishing a performance baseline on 4888 GPUs with COSMO 5.0, Geosci. Model Dev., 11, 1665-1681, https://doi.org/10.5194/gmd-11-1665-2018, 2018.

https://www.geosci-model-dev.net/11/1665/2018/

Abstract. The best hope for reducing long-standing global climate model biases is by increasing resolution to the kilometer scale. Here we present results from an ultrahigh-resolution non-hydrostatic climate model for a near-global setup running on the full Piz Daint supercomputer on 4888 GPUs (graphics processing units). The dynamical core of the model has been completely rewritten using a domain-specific language (DSL) for performance portability across different hardware architectures. Physical parameterizations and diagnostics have been ported using compiler directives. To our knowledge this represents the first complete atmospheric model being run entirely on accelerators on this scale. At a grid spacing of 930 m (1.9 km), we achieve a simulation throughput of 0.043 (0.23) simulated years per day and an energy consumption of 596 MWh per simulated year. Furthermore, we propose a new memory usage efficiency (MUE) metric that considers how efficiently the memory bandwidth – the dominant bottleneck of climate codes – is being used.

[AbruptSLR]

The DOE has now released computer code & preliminary results from ACME (Accelerated Climate Model for Energy) while the DOE has renamed the program E3SM (Energy Exascale Earth System Model), and this world's most sophisticated climate model projects that ECS for the rest of this century will be about 5.2C (& this relatively high value is likely attributable to the state-of-the-art way that ACME/E3SM models aerosols and cloud feedback mechanisms).

While some consensus scientists (like Bjorn Stevens) have said that it is difficult to determine whether the ACME findings are any more relevant than other models in the CMIP6 program; I believe that these findings from the world's most advanced ESM warrant the adoptions of the Precautionary Principle, particularly as the ACME results only partially address Hansen's ice-climate feedback mechanism:

Title: "DOE’s maverick climate model is about to get its first test"
doi:10.1126/science.aau0578

http://www.sciencemag.org/news/2018/05/does-maverick-climate-model-about-get-its-first-test

Extract: "In 2017, after President Donald Trump took office and pulled the nation out of the Paris climate accords, DOE dropped "climate" from the project name. The new name, the Energy Exascale Earth System Model (E3SM), better reflects the model's focus on the entire Earth system, says project leader David Bader of Lawrence Livermore National Laboratory in California.
..
One preliminary result, on the climate's sensitivity to carbon dioxide (CO2), will "raise some eyebrows," Bader says. Most models estimate that, for a doubling of CO2 above preindustrial levels, average global temperatures will rise between 1.5°C and 4.5°C. The E3SM predicts a strikingly high rise of 5.2°C, which Leung suspects is due to the way the model handles aerosols and clouds. And like many models, the E3SM produces two bands of rainfall in the tropics, rather than the one seen in nature near the equator.

The first test of the E3SM will be its performance in CMIP6. Nearly three dozen modeling groups, including newcomers from South Korea, India, Brazil, and South Africa, are expected to submit results to the intercomparison between now and 2020."

See also:

https://gcn.com/articles/2018/04/26/e3sm-earth-model.aspx

&

https://www.llnl.gov/news/new-exascale-system-earth-simulation

Edit2, see also:

Title: "SimEarth"

https://phys.org/news/2018-05-simearth.html

Extract: ""With this new system, we'll be able to more realistically simulate the present, which gives us more confidence to simulate the future," says David Bader, computational scientist at Lawrence Livermore National Laboratory and overall E3SM project lead."

[AbruptSLR]

The linked reference provides a mathematical framework for modeling cascading tipping mechanisms resulting in abrupt climate change; and as an illustration of this methodology it provides a conceptual model for coupling the North Atlantic Ocean Overturning Current and the ENSO system in the Pacific.  Consensus climate science should use such a methodology to better evaluate the risks associated with Hansen's ice-climate feedback mechanism:

Dekker, M. M., von der Heydt, A. S., and Dijkstra, H. A.: Cascading transitions in the climate system, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-26, in review, 2018.

https://www.earth-syst-dynam-discuss.net/esd-2018-26/
https://www.earth-syst-dynam-discuss.net/esd-2018-26/esd-2018-26.pdf

Abstract. We provide a theory of cascading tipping, i.e., a sequence of abrupt transitions occurring because a transition in one subsystem changes the background conditions for another subsystem. A mathematical framework of elementary deterministic cascading tipping points in autonomous dynamical systems is presented containing the double-fold, fold-Hopf, Hopf-fold and double-Hopf as most generic cases. Statistical indicators which can be used as early warning indicators of cascading tipping events in stochastic, non-stationary systems are suggested. The concept of cascading tipping is illustrated through a conceptual model of the coupled North Atlantic Ocean – El-Niño Southern Oscillation (ENSO) system, demonstrating the possibility of such cascading events in the climate system.

[AbruptSLR]

A new version of CESM has been recently released that includes several new features including improved modeling of aerosol interactions and of ice sheet modeling:

Joel, L. (2018), New version of popular climate model released, Eos, 99, https://doi.org/10.1029/2018EO101489. Published on 22 June 2018

https://eos.org/articles/new-version-of-popular-climate-model-released?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz062918

Extract: "One year ago this month, climate researchers met at a workshop in Boulder, Colo., to fix a big glitch in the second version of the Community Earth System Model (CESM), a computer program that scientists around the world use to simulate Earth’s complex climate system.
…
Specifically, in CESM2 simulations, there was a stretch of about 2 decades in the middle of the 20th century that showed global temperatures minutely falling by 0.3°C or 0.4°C, despite real-world observations pointing toward a steady rise in global temperatures over the same 20-year period. This contrary trend occurred when the model calculated how sulfate aerosols changed the properties of clouds, a phenomenon known as the “aerosol indirect effect.” When sufficiently strong, this effect can cause cooling on a global scale.
…
Despite their efforts, the contrary trend still crops up in CESM2. “But it’s much, much reduced from last year,” Lamarque said, adding that it will take many more years of work “by very smart people” to untangle what is really going on under the model’s hood. The cloud-aerosol mechanism currently outputs a temperature drop of about 0.1°C, effectively curtailing the glitch by more than half.
…
One of those new features is a capability that will allow users to model the behavior of Greenland’s ice sheet in greater detail. “You can have prognostic evolution of the Greenland ice sheet,” Danabasoglu said. This means that when the model runs, the parts of the ice sheet abutting the ocean melt at a relatively faster clip than ice farther inland, a process that more closely matches reality. This mechanism, Danabasoglu explained, is rather new among today’s climate models."

[AbruptSLR]

Lesson learned from paleo mollusks: if you want to survive a socio-economic collapse, slowdown your pace of life:

Luke C. Strotz, Erin E. Saupe, Julien Kimmig, Bruce S. Lieberman (22 August 2018), "Metabolic rates, climate and macroevolution: a case study using Neogene molluscs", Proceedings of the Royal Society B – Biological Sciences, DOI: 10.1098/rspb.2018.1292

http://rspb.royalsocietypublishing.org/content/285/1885/20181292

Abstract: "Basal metabolic rate (BMR) is posited to be a fundamental control on the structure and dynamics of ecological networks, influencing organism resource use and rates of senescence. Differences in the maintenance energy requirements of individual species therefore potentially predict extinction likelihood. If validated, this would comprise an important link between organismic ecology and macroevolutionary dynamics. To test this hypothesis, the BMRs of organisms within fossil species were determined using body size and temperature data, and considered in the light of species' survival and extinction through time. Our analysis focused on the high-resolution record of Pliocene to recent molluscs (bivalves and gastropods) from the Western Atlantic. Species-specific BMRs were calculated by measuring the size range of specimens from museum collections, determining ocean temperature using the HadCM3 global climate model, and deriving values based on relevant equations. Intriguingly, a statistically significant difference in metabolic rate exists between those bivalve and gastropod taxa that went extinct and those that survived throughout the course of the Neogene. This indicates that there is a scaling up from organismic properties to species survival for these communities. Metabolic rate could therefore represent an important metric for predicting future extinction patterns, with changes in global climate potentially affecting the lifespan of individuals, ultimately leading to the extinction of the species they are contained within. We also find that, at the assemblage level, there are no significant differences in metabolic rates for different time intervals throughout the entire study period. This may suggest that Neogene mollusc communities have remained energetically stable, despite many extinctions."

[AbruptSLR]

The following is related to the ACME modelling effort:

Fyke, J, O Sergienko, M Lofverstrom, S Price, and J Lenaerts.  2018.  "An Overview of Interactions and Feedbacks Between Ice Sheets and the Earth System."  Reviews of Geophysics, doi:10.1029/2018rg000600.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018RG000600

Abstract
Ice sheet response to forced changes—such as that from anthropogenic climate forcing—is closely regulated by two‐way interactions with other components of the Earth system. These interactions encompass the ice sheet response to Earth system forcing, the Earth system response to ice sheet change, and feedbacks resulting from coupled ice sheet/Earth system evolution. Motivated by the impact of Antarctic and Greenland ice sheet change on future sea level rise, here we review the state of knowledge of ice sheet/Earth system interactions and feedbacks. We also describe emerging observation and model‐based methods that can improve understanding of ice sheet/Earth system interactions and feedbacks. We particularly focus on the development of Earth system models that incorporate current understanding of Earth system processes, ice dynamics, and ice sheet/Earth system couplings. Such models will be critical tools for projecting future sea level rise from anthropogenically forced ice sheet mass loss.
Plain Language Summary
Sea level rise from ice sheets depends closely on interactions between ice sheets and the surrounding Earth system. These interactions determine how forcings to the climate system (such as from anthropogenic climate influences) translate to ice sheet change, which in turn impact the surrounding environment. This set of two‐way interactions between ice sheets and the Earth system forms the basis for important, yet poorly understood feedback loops. This review article describes the current state of knowledge of ice sheet/Earth system interactions and feedbacks and describes promising observational techniques for better understanding their behavior. It also highlights challenges and opportunities in modeling these interactions and feedbacks using coupled ice sheet/Earth system models, which will ultimately be used to predict future sea level rise caused by ice sheet loss.

[AbruptSLR]

The linked reference deals with ice sheet modeling in the Energy Exascale Earth System Model (E3SM) version 1 program:

Hoffman, M. J., Perego, M., Price, S. F., Lipscomb, W. H., Jacobsen, D., Tezaur, I., Salinger, A. G., Tuminaro, R. and Zhang, T.: MPAS-Albany Land Ice (MALI): A variable resolution ice sheet model for Earth system modeling using Voronoi grids, Geosci. Model Dev. Discuss., in review, 1–47, doi:10.5194/gmd-2018-78, 2018.

https://www.geosci-model-dev-discuss.net/gmd-2018-78/

Abstract: "We introduce MPAS-Albany Land Ice (MALI), a new, variable resolution land ice model that uses unstructured Voronoi grids on a plane or sphere. MALI is built using the Model for Prediction Across Scales (MPAS) framework for developing variable resolution Earth System Model components and the Albany multi-physics code base for solution of coupled systems of partial-differential equations, which itself makes use of Trilinos solver libraries. MALI includes a three-dimensional, first-order momentum balance solver ("Blatter-Pattyn") by linking to the Albany-LI ice sheet velocity solver, as well as an explicit shallow ice velocity solver. Evolution of ice geometry and tracers is handled through an explicit first-order horizontal advection scheme with vertical remapping. Evolution of ice temperature is treated using operator splitting of vertical diffusion and horizontal advection and can be configured to use either a temperature or enthalpy formulation. MALI includes a mass-conserving subglacial hydrology model that supports distributed and/or channelized drainage and can optionally be coupled to ice dynamics. Options for calving include "eigencalving", which assumes calving rate is proportional to extensional strain rates. MALI is evaluated against commonly used exact solutions and community benchmark experiments and shows the expected accuracy. We report first results for the MISMIP3d benchmark experiments for a Blatter-Pattyn type model and show that results fall in-between those of models using Stokes flow and L1L2 approximations. We use the model to simulate a semi-realistic Antarctic Ice Sheet problem for 1100 years at 20km resolution. MALI is the glacier component of the Energy Exascale Earth System Model (E3SM) version 1, and we describe current and planned coupling to other components."

[AbruptSLR]

Accounting for model dependence in CMIP6 will be a challenge:

Abramowitz, G., Herger, N., Gutmann, E., Hammerling, D., Knutti, R., Leduc, M., Lorenz, R., Pincus, R., and Schmidt, G. A.: Model dependence in multi-model climate ensembles: weighting, sub-selection and out-of-sample testing, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-51, in review, 2018.

https://www.earth-syst-dynam-discuss.net/esd-2018-51/

Abstract. The rationale for using multi-model ensembles in climate change projections and impacts research is often based on the expectation that different models constitute independent estimates, so that a range of models allows a better characterisation of the uncertainties in the representation of the climate system than a single model. However, it is known that research groups share literature, ideas for representations of processes, parameterisations, evaluation data sets and even sections of model code. Thus, nominally different models might have similar biases because of similarities in the way they represent a subset of processes, or even be near duplicates of others, weakening the assumption that they constitute independent estimates. If there are near-replicates of some models, then treating all models equally is likely to bias the inferences made using these ensembles. The challenge is to establish the degree to which this might be true for any given application. While this issue is recognized by many in the community, quantifying and accounting for model dependence in anything other than an ad-hoc way is challenging. Here we present a synthesis of the range of disparate attempts to define, quantify and address model dependence in multi-model climate ensembles in a common conceptual framework, and provide guidance on how users can test the efficacy of approaches that move beyond the equally weighted ensemble. In the upcoming Coupled Model Intercomparison Project phase 6 (CMIP6), several new models that are closely related to existing models are anticipated, as well as large ensembles from some models. We argue that quantitatively accounting for dependence in addition to model performance, and thoroughly testing the effectiveness of the approach used will be key to a sound interpretation of the CMIP ensembles in future scientific studies.

[AbruptSLR]

The linked reference discusses a new modeling tool for projecting how melting permafrost may 'affect carbon release, wetland and river deltas' with continuing global warming:

Overeem, I., E. Jafarov, K. Wang, K. Schaefer, S. Stewart, G. Clow, M. Piper, and Y. Elshorbany (2018), A modeling toolbox for permafrost landscapes, Eos, 99, https://doi.org/10.1029/2018EO105155. Published on 28 September 2018.

https://eos.org/project-updates/a-modeling-toolbox-for-permafrost-landscapes?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz100518

Extract: "A new resource makes it easier for researchers to explore predictions of how melting permafrost might affect carbon release, wetlands, and river deltas as they evolve and other interacting effects."

[vox_mundi]

New Interactive Scenario Explorer for 1.5°C Pathways

IIASA and the Integrated Assessment Modeling Consortium (IAMC) have made the scenarios underlying last week’s Intergovernmental Panel on Climate Change (IPCC) 1.5°C Special Report publicly available, in an interactive online resource. The resource provides scenarios and a suite of visualization and analysis tools, making the assessment more transparent to researchers, policymakers, and the public.

The new scenario explorer—which was developed by IIASA on behalf of the Integrated Assessment Modeling Consortium (IAMC) and the IPCC—includes 414 scenarios for future climate change developed by more than a dozen research teams from around the world. These scenarios, which focus on limiting temperature rise to below 1.5°C or 2°C above pre-industrial levels, include information related to the energy system, greenhouse gas emissions, land-use change, and other factors connected with climate change and sustainable development. 

It also includes visualization tools for exploring the data, so that policymakers and researchers in related fields such as climate finance can explore different options for climate action and their potential consequences. And it is freely accessible to the general public, so that anyone who is interested can explore the scenarios to better understand mitigation options and their synergies and trade-offs with sustainable development and other societal priorities.

https://data.ene.iiasa.ac.at/iamc-1.5c-explorer/#/login?redirect=%2Fworkspaces


http://www.iiasa.ac.at/
https://www.nature.com/articles/s41558-018-0317-4

[AbruptSLR]

While I am not good at using the associated data, I note that the CMIP6 model output is starting to come out and can be accessed at the following links:

https://esgf-node.llnl.gov/projects/cmip6/
&
https://esgf-node.llnl.gov/search/cmip6/

[vox_mundi]

Modest Warming Risks 'Irreversible' Ice Sheet Loss

Scientists have known for decades that the ice sheets of Greenland and Antarctica are shrinking, but it had been assumed that they would survive a 1.5-2C temperature rise relatively intact.

However, according to a new analysis published in the journal Nature Climate Change, even modest global warming could cause irreversible damage to the polar ice, contributing to catastrophic sea level rises.

"We say that 1.5-2C is close to the limit for which more dramatic effects may be expected from the ice sheets," Frank Pattyn, head of the department of geosciences, Free University of Brussels and lead study author, told AFP.

 Many models of the 1.5-2C scenario allow for the threshold to be breached in the short term, potentially heating the planet several degrees higher, before using carbon capture and other technologies to bring temperatures back into line by 2100.

The study warned against this approach, however, saying that a feedback loop set off by higher temperatures would "lead to self-sustained melting of the entire ice sheet" even if those rises were later offset.

For Greenland, the team said with 95 percent certainty that major ice sheet decline would occur at 1.8C worth of warming.

"For both Greenland and Antarctica, tipping points are known to exist for warming levels that could be reached before the end of this century," said Pattyn.

The Greenland and Antarctic ice sheets under 1.5 °C global warming, Nature Climate Change (2018

[AbruptSLR]

Due to Neven's management style, I have decided to stop posting in this forum.

Sayonara,
ASLR

[wdmn]

New study published today: Pliocene and Eocene provide best analogs for near-future climatesmates https://www.pnas.org/content/early/2018/12/05/1809600115.

Abstract
Past Earth system states offer possible model systems for the warming world of the coming decades. These include the climate states of the Early Eocene (ca. 50 Ma), the Mid-Pliocene (3.3–3.0 Ma), the Last Interglacial (129–116 ka), the Mid-Holocene (6 ka), preindustrial (ca. 1850 CE), and the 20th century. Here, we quantitatively assess the similarity of future projected climate states to these six geohistorical benchmarks using simulations from the Hadley Centre Coupled Model Version 3 (HadCM3), the Goddard Institute for Space Studies Model E2-R (GISS), and the Community Climate System Model, Versions 3 and 4 (CCSM) Earth system models. Under the Representative Concentration Pathway 8.5 (RCP8.5) emission scenario, by 2030 CE, future climates most closely resemble Mid-Pliocene climates, and by 2150 CE, they most closely resemble Eocene climates. Under RCP4.5, climate stabilizes at Pliocene-like conditions by 2040 CE. Pliocene-like and Eocene-like climates emerge first in continental interiors and then expand outward. Geologically novel climates are uncommon in RCP4.5 (<1%) but reach 8.7% of the globe under RCP8.5, characterized by high temperatures and precipitation. Hence, RCP4.5 is roughly equivalent to stabilizing at Pliocene-like climates, while unmitigated emission trajectories, such as RCP8.5, are similar to reversing millions of years of long-term cooling on the scale of a few human generations. Both the emergence of geologically novel climates and the rapid reversion to Eocene-like climates may be outside the range of evolutionary adaptive capacity.

graph source: Bob Kopp @bobkopp

[Pmt111500]

Thanks wdmn. I only wonder why they left early Miocene out of the periods they compared to. Not that it is much different from Eocene. Interesting result that interiors of the continents would see the change first, just like expected. Oceans heat up more slowly even in those conditions as well.

[wdmn]

Thanks wdmn. I only wonder why they left early Miocene out of the periods they compared to. Not that it is much different from Eocene. Interesting result that interiors of the continents would see the change first, just like expected. Oceans heat up more slowly even in those conditions as well.

Not very good news for agriculture in North America...

[gerontocrat]

At last a study to tell us what many of us knew already. There are connections between various forms of environmental destruction, and they can reinforce each other. The article is, of course, paywalled.

(Now knocking down these barriers to dissemination of knowledge would be a good use of Gates's foundation money instead of ludicrous schemes for global extinction of the mosquito https://philanthropynewsdigest.org/news/gates-foundation-awards-35-million-for-mosquito-research)


http://science.sciencemag.org/content/362/6421/1379
https://www.theguardian.com/environment/2018/dec/20/risks-of-domino-effect-of-tipping-points-greater-than-thought-study-says

Risks of 'domino effect' of tipping points greater than thought, study says

Scientists warn policymakers not to ignore links, and stress that ‘every action counts’

Policymakers have severely underestimated the risks of ecological tipping points, according to a study that shows 45% of all potential environmental collapses are interrelated and could amplify one another.

The authors said their paper, published in the journal Science, highlights how overstressed and overlapping natural systems are combining to throw up a growing number of unwelcome surprises.

“The risks are greater than assumed because the interactions are more dynamic,” said Juan Rocha of the Stockholm Resilience Centre. “The important message is to recognise the wickedness of the problem that humanity faces.”

The study collated existing research on ecosystem transitions that can irreversibly tip to another state, such as coral reefs bleaching and being overrun by algae, forests becoming savannahs and ice sheets melting into oceans. It then cross-referenced the 30 types of shift to examine the impacts they might have on one another and human society.

Only 19% were entirely isolated. Another 36% shared a common cause, but were not likely to interact. The remaining 45% had the potential to create either a one-way domino effect or mutually reinforcing feedbacks......

The authors of the new paper say their work goes beyond climate studies by mapping a wider range of ecological stress points, such as biodiversity loss, agricultural expansion, urbanisation and soil erosion.

Rocha has spent 10 years building a database of tipping points, or “regime shifts” as he calls them. He urges policymakers to adopt a similar interdisciplinary approach so they can better grasp what is happening.

[Tom_Mazanec]

Is using the Pliocene, the PETM, etc. a good analog for global warming today?
In the Pliocene the Panama Isthmus did not exist, nor did the Gulf Stream, so the climate would be altered just by that. Go to the Miocene and the Mediterranean was a salt desert. In the PETM the Himalayan Mountains, with their effect on atmospheric circulation, did not exist. Can we rely on these models?

[b_lumenkraft]

Is using the Pliocene, the PETM, etc. a good analog for global warming today?
In the Pliocene the Panama Isthmus did not exist, nor did the Gulf Stream, so the climate would be altered just by that. Go to the Miocene and the Mediterranean was a salt desert. In the PETM the Himalayan Mountains, with their effect on atmospheric circulation, did not exist. Can we rely on these models?

Also, today's climate change is happening way faster. In the past, these things took thousands of years to evolve.

[Pmt111500]

In pliocene the equatorial counter current in Pacific (the one which is involved in El Nino) indeed likely kept the North Atlantic warmer than today, as it got through the channel. Nowadays the warmth that couldn't enter the Atlantic went partly to north Pacific and it should warm up Alaska, partly NW north america and the Arctic Seas up there.

This might lead to some arctic air masses coming down on Atlantic side of Arctic leading f.e. to rather massive snowstorms in Eastern America and occasionally in western Europe. Niagara Falls might freeze up. Even the Gulf stream could be weakened and be directed more southwards possibly leading to early springs in middle Europe and cooling the British winters. Well, some of these might have already happened.

[mitch]

Paleoclimatologists/Paleoceanographers don't use the Pliocene as an  analog but as a means to study the dynamics on a warm earth. They can infer if models contain all the processes that maintained global warmth.

Contrary to what a few people have posted, the Isthmus was almost emergent, with only a few passages around 50-100 m at the beginning of the Pliocene (5.3 million years ago [Ma]). Mammals started crossing between North and South America at around 3 Ma, which dates essential closure.

The Gulf Stream existed at that time, and so did the Pacific trade winds driving the South equatorial current.  The eastern Pacific was warmer, but that is due to warmer subarctic conditions.  If you want to get an idea what is being done, here is a site to look at:
https://geology.er.usgs.gov/egpsc/prism/index.html

[Tom_Mazanec]

The Anthropocene could last a long time:
 
Released Carbon (Gton)        pCO2 (100,000 AD)
300                                      ~290
1000                                    ~320
2000                                    ~350
5000                                    ~550
Figure 1
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004JC002625

[Tor Bejnar]

Anthropocene edging closer to being ‘official’
Steve Drury - May 31, 2019 - in his Earth-logs blog (formerly "Earth-Pages")

The issue of erecting a new stratigraphic Epoch encompassing the time since humans had a global effect on the Earth System has irked me ever since the term emerged for discussion and resolution by the scientific community in 2000.
…
In the 3rd week of May 2019 the 34-member Anthropocene Working Group (AWG) of the International Commission on Stratigraphy (ICS) sat down to decide on when the Anthropocene actually started. That date would be passed on up the hierarchy of the geoscientific community  eventually to meet the scrutiny of its highest body, the executive committee of the International Union of Geological Sciences, and either be ratified or not. In the meantime the AWG is seeking a site at which the lower boundary of the Anthropocene would be defined by the science’s equivalent of a ‘golden spike’; the Global boundary Stratotype Section and Point (GSSP).
…
Around 1963 there are also clear signs that plastics, aluminium, artificial fertilisers, concrete and lead from petrol began to increase in sediments. It is this … option upon which the AWG settled
…
The decision, in my opinion, signifies that the Anthropocene is an Epoch that includes the future, which is somewhat pessimistic as well as being scientific nonsense. Yet, coinciding as it does with rapidly escalating efforts, mainly by young people, to end massive threats to the Earth System, that can only be welcomed. It is an essentially political statement, albeit with a learned cloak thrown over it.  The only way to erase the exponentially growing human buttock print on our home world is for growth-dependent economics to be removed too. That is the only logical basis for the ‘green’ revolt that is unfolding. If that social revolution doesn’t happen, there will be a mass extinction to join the ‘Big Five’, and society in all its personifications will collapse. That is known as barbarism… [this ellipsis in original]

[sidd]

I was unsure if i should post this in the AMOC thread or elsewhere, but i post here:

Haustein et al. find no necessity to invoke AMOC change to explain temperature record over 20th century ... if you put the aerosols in.

"Using a two-box impulse response model, we demonstrate that multidecadal ocean variability was unlikely to be the driver of observed changes in global mean surface temperature (GMST) after 1850 A.D. Instead, virtually all (97-98%) of the global low-frequency variability (>30 years) can be explained by external forcing. "

TCR over the period is 1.57K ...

"our most precise TCR estimate is 1.57K with an associated inter-decile uncertainty range of 0.87-2.27K(10-90th percentiles)."

They can't really pin down ECS.

ENSO isnt too important either except for shorter timescales:

" low-frequency ENSO variability has little bearing on the outcome of our response model results."

Atlantic variability appears to be forced, rather than internal:

"There is room for 1-5 year unforced feedbacks,  but apart from the cooling due to the long-term decline in AMOC strength (Fig. 8m), high- and low-frequency AMV pattern appear to be externally forced according to our response model results."

AMV is atlantic multidecadal variation.

"our analysis strongly suggests that the impact of internally generated NA ocean dynamics on Global, NHem and Land temperatures is rather limited"

" changes to the mean state are dominated by radiative forcings on longer timescales and ENSO-related variability on shorter timescales"

Amazing what you can do with a simplish two box model.

doi: 10.1175/JCLI-D-18-0555.1

" internal variability could explain only 7% of the record. Instead, soot from industry drove early 20th century warming as it drifted into the Arctic, darkening snow and absorbing sunlight. After World War II, light-reflecting sulfate haze from power plants increased, holding off potential warming from rising greenhouse gases. Then, pollution controls arrived in the 1970s, cutting haze and allowing warming to speed ahead."

"a future ocean cooling is unlikely to buy society time to address global warming. But the demise of the AMO also might make it easier to predict what is in store. “All we're going to get in the future,” Haustein says, “is what we do.” "

https://science.sciencemag.org/content/364/6443/814

https://www.carbonbrief.org/guest-post-why-natural-cycles-only-play-small-role-in-rate-of-global-warming

sidd

[Tom_Mazanec]

More from https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004JC002625

Gton release                  Mean ocean T change at 102,000 AD
300                               ~0.17 C
1000                             ~0.5 C
2000                             ~0.9 C
5000                             ~2 C

[sidd]

Realclimate has a post up on the Haustein paper by the authors:

http://www.realclimate.org/index.php/archives/2019/06/unforced-variations-vs-forced-responses/

sidd

[bligh8]

Conclusions: It was us.

The findings presented in our paper highlight that we are now able to explain almost all the warming patterns since 1850, including the Early Warming period. We achieve this by separating different forcing factors, by including an updated aerosol dataset and by removing notable SST biases. We have avoided overfitting by virtue of a strict non-regression policy. We ask the different research communities to take these findings as food for thought, particularly with regard to the Early Warming. We most definitely believe that it is time to rethink the role of the AMV and recommend using our newly introduced NAVI definition instead. This will also help to understand contemporary AMOC changes and its relation to climate change better, and perhaps provide guidance as to which climate models best approximate internal ocean variability on longer timescales.

Very Nice Paper...Thanks Mr sidd

bligh

[sidd]

The thing that struck me about that paper is how far you can get with just a two box ocean model.

sidd

[bligh8]

Eggzackly .. and no speed humps

[Tom_Mazanec]

Ocean color and modeling AGW:
https://psmag.com/environment/how-scientists-use-ocean-color-to-determine-its-temperature

EDIT: Must include microbes in climate modeling:
https://newsroom.unsw.edu.au/news/science-tech/leaving-microbes-out-climate-change-conversation-has-major-consequences-experts

[sidd]

DOI: 10.1126/science.aax1192


is a new paper on early anthro influence on ecosystems. Extends the HYDE and KK10 frameworks. Very nice.

sidd

[longwalks1]

Archaeological assessment reveals Earth’ s early transformation through land use

Here, we present a global assessment of archaeological expert knowledge on land use from 10,000 years before the present (yr B.P.) to 1850 CE, showing that existing global reconstructions underestimate the impact of early human land use on Earth’s current ecology.

Have not read yet.  To find the authors is a bit of a slog.  The ArchaeoGLOBE Project was  listed via 2 capital letters for each individual.  sleuthed.  http://globe.umbc.edu/archaeoglobe/archaeoglobe-authors/     has the authors. 

2 blogs about the article
https://www.washington.edu/news/2019/08/29/crowdsourced-archaeology-shows-how-humans-have-influenced-earth-for-thousands-of-years/

“There are archaeologists working all over the world, but they aggregate data differently, and it can be difficult to find larger patterns,” said co-author Ben Marwick, an associate professor of anthropology at the UW. “By asking archaeologists a series of questions rather than combining datasets, we’ve created a brilliant workaround — essentially, what were people doing, and how much, in different parts of the world?”

https://www.science20.com/news_staff/archaeoglobe_project_if_there_is_an_anthropocene_epoch_it_started_4000_years_ago-241227

The scholars pooled extensive datasets summarizing decades of archaeological research. Nicole Boivin, Director of the Department of Archaeology at the Max Planck Institute for the Science of Human History and a lead author on the study, notes that "archaeologists possess critical datasets for assessing long-term human impacts to the natural world, but these remain largely untapped in terms of global-scale assessments".

[sidd]

paper on long (millennial scale) model intercomparison:

doi: 10.1175/BAMS-D-19-0068.1

Nice paper. open access. many usual suspects are authors

sidd

[DanLittle]

https://youtu.be/zZ-lMDtiI-k?feature=shared

High Resolution visual of C02 being released into the atmosphere.