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Author Topic: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME  (Read 19506 times)

AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #100 on: July 05, 2017, 07:23:00 PM »
The linked reference correlates changes in large-scale weather patterns with changes in surface temperature gradients in the N.H.:

Molnos, S., Petri, S., Lehmann, J., Peukert, E., and Coumou, D.: The sensitivity of the large-scale atmosphere circulation to changes in surface temperature gradients in the Northern Hemisphere, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2017-65, in review, 2017.

http://www.earth-syst-dynam-discuss.net/esd-2017-65/

Abstract. Climate and weather conditions in the mid-latitudes are strongly driven by the large-scale atmosphere circulation. Observational data indicates that important components of the large-scale circulation have changed in recent decades including the strength of the Hadley cell, jet streams, storm tracks and planetary waves. Associated impacts cover a broad range, including changes in the frequency and nature of weather extremes and shifts of fertile habitats with implications for biodiversity and agriculture. Dynamical theories have been proposed that link the shift of the poleward edge of the Northern Hadley cell to changes in the meridional temperature gradient. Moreover, model simulations have been carried out to analyse the cause of observed and projected changes in the large-scale atmosphere circulation. However, the question of the underlying drivers and particularly the possible role of global warming is still debated. Here, we use a statistical-dynamical atmosphere model (SDAM) to analyse the sensitivity of the Northern Hemisphere Hadley cell, storm tracks, jet streams and planetary waves to changes in temperature fields by systematically altering the zonal and meridional temperature gradient as well as the global mean surface temperature.  SDAMs are computationally fast compared to more complex general circulation models (GCM) which enables us to scan a large and high-dimensional parameter space for sensitivity analyses using more than thousand individual model runs.

Our results show that the strength of the Hadley cell, storm tracks and jet streams depends almost linearly on both the global mean temperature and the meridional temperature gradient whereas the zonal temperature gradient has little or no influence. The magnitude of planetary waves is clearly affected by all three temperature components. Finally, the width of the Hadley cell behaves nonlinearly with respect to all three temperature components.

Under global warming the meridional temperature gradient is expected to change: Enhanced warming is expected in the Arctic, largely near the surface, and at the equator at high altitudes. Also there is a pronounced seasonality to these warming patterns. Using SDAMs to disentangle and separately analyse the effect of individual temperature changes might thus help to understand observed and projected changes in large-scale atmosphere dynamics.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #101 on: July 07, 2017, 04:29:15 PM »
One of the many Achilles heels (others include: Hansen's ice-climate feedback, timing of slow response feedbacks, and dynamical climate attractors) of climate change projection is uncertainty about feedbacks from CO₂ absorption/emissions from the terrestrial biosphere.  The linked article discusses new findings on how to better calibrate this feedback mechanism via tracking of carbonyl sulfide.  In the attached image GPP means gross primary production

Campbell, J. E., et al. (05 July 2017.), "Assessing a new clue to how much carbon plants take up", Eos, 98, https://doi.org/10.1029/2017EO075313

https://eos.org/features/assessing-a-new-clue-to-how-much-carbon-plants-take-up?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz070717

Extract: "Current climate models disagree on how much carbon dioxide land ecosystems take up for photosynthesis. Tracking the stronger carbonyl sulfide signal could help.

Climate change projections include an Achilles heel: We don’t know enough about feedbacks from the terrestrial biosphere. Plants and other organisms take in carbon dioxide (CO2), which they use to manufacture their own food, using photosynthesis. This process lets ecosystems sequester atmospheric CO2, creating one of the largest known feedbacks in the climate system. But models of the global climate system differ greatly in their estimates of carbon uptake, leading to critical uncertainties in global climate projections.

This predicament has inspired a search for new approaches to study the photosynthetic uptake of CO2. In response, atmospheric scientists, biogeochemists, and oceanographers have proposed measuring a gas called carbonyl sulfide (COS or OCS) to help quantify the contribution that photosynthesis makes to carbon uptake. COS is similar in structure and composition to CO2, with a sulfur atom replacing one of CO2’s oxygen atoms.

Ten years ago, scientists discovered a massive and persistent biosphere signal in atmospheric COS measurements. In these data, COS and CO2 levels follow a similar seasonal pattern, but the COS signal is much stronger over continental regions, suggesting that the terrestrial biosphere is a sink for COS"
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #102 on: July 07, 2017, 05:13:06 PM »

The linked reference provides useful insight in how to untangle the impacts of efficacies of forcing and ocean heat uptake on the evolution of radiative feedbacks:

A. D. Haugstad, K. C. Armour, D. S. Battisti & B. E. J. Rose (6 July 2017), "Relative roles of surface temperature and climate forcing patterns in the inconstancy of radiative feedbacks", Geophysical Research Letters, DOI: 10.1002/2017GL074372 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL074372/abstract?utm_content=bufferca02a&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Radiative feedbacks robustly vary over time in transient warming simulations. Published studies offer two explanations: (i) evolving patterns of ocean heat uptake (OHU) or radiative forcing give rise to OHU or forcing ‘efficacies’, and (ii) evolving patterns of surface temperature change. This study seeks to determine whether these explanations are indeed distinct. Using an idealized framework of an aquaplanet atmosphere-only model, we show radiative feedbacks depend on the pattern of climate forcing. Yet, the same feedbacks arise when the temperature pattern induced by that climate forcing is prescribed in the absence of any forcing. These findings suggest the perspective that feedbacks are influenced by ‘efficacies’ of forcing and OHU is equivalent to the perspective that feedbacks are dependent on the temperature patterns induced by those forcings. These findings suggest that prescribed surface temperature simulations are valuable for studying the temporal evolution of radiative feedbacks."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #103 on: July 09, 2017, 05:02:07 PM »
The linked reference raises an important and complex topic that is poorly understood: "The nexus between sea ice and polar emissions of marine biogenic aerosols.  I hope that the complexity of this topic does not cause climate model makers to underplay the risk that an increase in polar marine biogenic aerosols could increase rainfall, which could increase polar amplification in the future.

Albert Gabric, Patricia Matrai, Graham Jones, and Julia Middleton (July 7, 2017), "The nexus between sea ice and polar emissions of marine biogenic aerosols", BAMS, https://doi.org/10.1175/BAMS-D-16-0254.1

http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-16-0254.1?utm_content=buffer45905&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "We examine the relationship between sea ice dynamics, phytoplankton biomass and emissions of marine biogenic aerosols in both Arctic and Southern Oceans.

Accurate estimation of the climate sensitivity requires a better understanding of the nexus between polar marine ecosystem responses to warming, changes in sea ice extent and emissions of marine biogenic aerosol (MBA). Sea ice brine channels contain very high concentrations of MBA precursors that once ventilated have the potential to alter cloud microphysical properties, such as cloud droplet number, and the regional radiative energy balance. In contrast to temperate latitudes, where the pelagic phytoplankton are major sources of MBAs, the seasonal sea ice dynamic plays a key role in determining MBA concentration in both the Arctic and Antarctic. We review the current knowledge of MBA sources and the link between ice melt and emissions of aerosol precursors in the polar oceans. We illustrate the processes by examining decadal scale time series in various satellite-derived parameters such as aerosol optical depth (AOD), sea ice extent and phytoplankton biomass in the sea ice zones of both hemispheres. The sharpest gradients in aerosol indicators occur during the spring period of ice melt. In sea ice covered waters, the peak in AOD occurs well before the annual maximum in biomass in both hemispheres. The results provide strong evidence that suggests seasonal changes in sea ice and ocean biology are key drivers of the polar aerosol cycle. The positive trend in annual mean Antarctic sea ice extent is now almost one-third of the magnitude of the annual mean decrease in Arctic sea ice, suggesting the potential for different patterns of aerosol emissions in the future."

Extract: "Marine biogenic aerosol (MBA) plays an important role in the radiative budget of remote marine atmospheres by potentially shaping regional climate (McCoy et al. 2015). MBAs can influence cloud microphysical properties as cloud condensation nuclei (CCN), affecting cloud albedo and lifetime.

There is now strong evidence to suggest that ocean biology augments the aerosol and cloud droplet concentration and radiative forcing also over the biologically active SO by a significant amount (McCoy et al. 2015; Vallina et al. 2006)."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #104 on: July 10, 2017, 04:51:49 AM »
Hopefully, CMIP6 will learn that summertime atmospheric may contribute up to 60% of the September sea-ice extent loss:

Qinghua Ding, Axel Schweiger, Michelle L’Heureux, David S. Battisti, Stephen Po-Chedley,Nathaniel C. Johnson, Eduardo Blanchard-Wrigglesworth, Kirstin Harnos, Qin Zhang, Ryan Eastman & Eric J. Steig (2017), “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice”, Nature Climate Change, 7, 289–295, doi:10.1038/nclimate3241

http://www.nature.com/nclimate/journal/v7/n4/abs/nclimate3241.html

Abstract: “The Arctic has seen rapid sea-ice decline in the past three decades, whilst warming at about twice the global average rate. Yet the relationship between Arctic warming and sea-ice loss is not well understood. Here, we present evidence that trends in summertime atmospheric circulation may have contributed as much as 60% to the September sea-ice extent decline since 1979. A tendency towards a stronger anticyclonic circulation over Greenland and the Arctic Ocean with a barotropic structure in the troposphere increased the downwelling longwave radiation above the ice by warming and moistening the lower troposphere. Model experiments, with reanalysis data constraining atmospheric circulation, replicate the observed thermodynamic response and indicate that the near-surface changes are dominated by circulation changes rather than feedbacks from the changing sea-ice cover. Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30–50% of the overall decline in September sea ice since 1979.”
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #105 on: July 10, 2017, 05:15:52 AM »
My last post focused on research focused on Arctic summertime sea ice, while the linked reference discusses a positive feedback (associated with longwave radiation) for Arctic sea ice during wintertime (I hope CMIP6 is paying attention):

Kwang-Yul Kim, Jinju Kim, Saerim Yeo, Hanna Na , Benjamin D. Hamlington, and Robert R. Leben (2017), “Understanding the Mechanism of Arctic Amplification and Sea Ice Loss”, The Cryosphere Discuss., doi:10.5194/tc-2017-39

http://www.the-cryosphere-discuss.net/tc-2017-39/tc-2017-39.pdf

Abstract: “Sea ice reduction is accelerating in the Barents and Kara Seas. Several mechanisms are proposed to explain the accelerated loss of polar sea ice, which remains an open question. In the present study, the detailed physical mechanism of sea ice reduction in winter is identified using the daily ERA interim reanalysis data. Downward longwave radiation is an essential element for sea ice reduction, but can only be sustained by excessive upward heat flux from the sea surface exposed to air in the region of sea ice loss. The increased turbulent heat flux is used to increase air temperature and specific humidity in the lower troposphere, which in turn increases downward longwave radiation. This feedback process is clearly observed in the Barents and Kara Seas in the reanalysis data. A quantitative assessment reveals that this feedback process is amplifying at the rate of ~8.9 % every year during 1979-2016. Based on this estimate, sea ice will completely disappear in the Barents and Kara Seas by around 2025. Availability of excessive heat flux is necessary for the maintenance of this feedback process; a similar mechanism of sea ice loss is expected to take place over the sea-ice covered polar region when sea ice is not fully recovered in winter.”
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #106 on: July 11, 2017, 05:39:25 PM »
The linked reference indicates that current climate models are biased w.r.t. methane emissions from global wetlands (as in ESLD), and recommends that the uncertainties associated with such bias be reduced.

Bowen Zhang, Hanqin Tian , Chaoqun Lu, Guangsheng Chen, Shufen Pan, Christopher Anderson & Benjamin Poulter (September 2017), "Methane emissions from global wetlands: An assessment of the uncertainty associated with various wetland extent data sets", Atmospheric Environment, Volume 165, Pages 310–321, https://doi.org/10.1016/j.atmosenv.2017.07.001

http://www.sciencedirect.com/science/article/pii/S1352231017304429

Abstract: "A wide range of estimates on global wetland methane (CH4) fluxes has been reported during the recent two decades. This gives rise to urgent needs to clarify and identify the uncertainty sources, and conclude a reconciled estimate for global CH4 fluxes from wetlands. Most estimates by using bottom-up approach rely on wetland data sets, but these data sets show largely inconsistent in terms of both wetland extent and spatiotemporal distribution. A quantitative assessment of uncertainties associated with these discrepancies among wetland data sets has not been well investigated yet. By comparing the five widely used global wetland data sets (GISS, GLWD, Kaplan, GIEMS and SWAMPS-GLWD), it this study, we found large differences in the wetland extent, ranging from 5.3 to 10.2 million km2, as well as their spatial and temporal distributions among the five data sets. These discrepancies in wetland data sets resulted in large bias in model-estimated global wetland CH4 emissions as simulated by using the Dynamic Land Ecosystem Model (DLEM). The model simulations indicated that the mean global wetland CH4 emissions during 2000–2007 were 177.2 ± 49.7 Tg CH4 yr−1, based on the five different data sets. The tropical regions contributed the largest portion of estimated CH4 emissions from global wetlands, but also had the largest discrepancy. Among six continents, the largest uncertainty was found in South America. Thus, the improved estimates of wetland extent and CH4 emissions in the tropical regions and South America would be a critical step toward an accurate estimate of global CH4 emissions. This uncertainty analysis also reveals an important need for our scientific community to generate a global scale wetland data set with higher spatial resolution and shorter time interval, by integrating multiple sources of field and satellite data with modeling approaches, for cross-scale extrapolation."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #107 on: July 12, 2017, 12:47:16 AM »
The linked reference confirms that the Earth is warming at unprecedented rates, and which provides data that can be used to better calibrate climate models:

PAGES2k Consortium (2017), "A global multiproxy database for temperature reconstructions of the Common Era", Scientific Data 4, Article number: 170088, doi:10.1038/sdata.2017.88

http://www.nature.com/articles/sdata201788

Abstract: "Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850–2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #108 on: July 14, 2017, 06:32:00 PM »
he linked reference discusses efforts to improve the calibration of models for the Greenland Ice Sheet in CMIP6:

Goelzer, H., Nowicki, S., Edwards, T., Beckley, M., Abe-Ouchi, A., Aschwanden, A., Calov, R., Gagliardini, O., Gillet-Chaulet, F., Golledge, N. R., Gregory, J., Greve, R., Humbert, A., Huybrechts, P., Kennedy, J. H., Larour, E., Lipscomb, W. H., Le clec´h, S., Lee, V., Morlighem, M., Pattyn, F., Payne, A. J., Rodehacke, C., Rückamp, M., Saito, F., Schlegel, N., Seroussi, H., Shepherd, A., Sun, S., van de Wal, R., and Ziemen, F. A.: Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-129, in review, 2017.

http://www.the-cryosphere-discuss.net/tc-2017-129/

Abstract. Earlier large-scale Greenland ice sheet sea-level projections (e.g., those run during the ice2sea and SeaRISE initiatives) have shown that ice sheet initial conditions can have a large effect on the projections and give rise to important uncertainties. The goal of the initMIP-Greenland intercomparison exercise is to compare, evaluate and improve the initialisation techniques used in the ice sheet modelling community and to estimate the associated uncertainties. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6). Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participating models of 1) the initial present-day state of the ice sheet and 2) the response in two schematic forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface mass balance anomaly), and should not be interpreted as sea-level projections. We present and discuss results that highlight the wide diversity of data sets, boundary conditions and initialisation techniques used in the community to generate initial states of the Greenland ice sheet. We find good agreement across the ensemble for the dynamic response to SMB changes in areas where the simulated ice sheets overlap, but in general differences arise due to the initial size of the ice sheet. The spread in model drift is reduced compared to earlier intercomparison exercises.
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #109 on: July 14, 2017, 06:34:30 PM »
The linked reference discusses efforts to improve modeling of black carbon impacts on the Third Pole.

Zhang, Y., Kang, S., Sprenger, M., Cong, Z., Gao, T., Li, C., Tao, S., Li, X., Zhong, X., Xu, M., Meng, W., and Sillanpää, M.: Black carbon and mineral dust in snow cover on the Third Pole, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-111, in review, 2017.

http://www.the-cryosphere-discuss.net/tc-2017-111/

Abstract. Light-absorbing impurities (including black carbon, organic carbon, and mineral dust) deposited on snow can reduce surface albedo and contribute to the near-worldwide melting of snow cover and ice. This study found that the black carbon, organic carbon, and dust concentrations in snow cover ranged generally from 202–17 468 ng g−1, 491–13 880 ng g−1, and 22–846 µg g−1, respectively, with higher concentrations in the central to northern areas of the Third Pole region (referred to by scientists also as the Tibetan Plateau and its surrounding mountains). Footprint analyses suggested that the northern Third Pole was influenced mainly by air masses from Central Asia with some Euro-Asia influence; air masses in the central and Himalayan region originated mainly from Central and South Asia. The open burning-sourced black carbon contributions decreased from ~ 50 % in the southern Third Pole region to ~ 30 % in the northern Third Pole region. The contribution of black carbon and dust to snow albedo reduction reached approximately 37 % and 15 %, respectively. The effect of black carbon and dust reduced the average snow cover duration by 3.1 ± 0.1 days to 4.4 ± 0.2 days. Meanwhile, the black carbon and dust had an import implication for snowmelt water loss over the Third Pole region. Findings indicate that the impacts of black carbon and mineral dust need to be properly accounted for in future regional climate projections, particularly in the high-altitude cryosphere.
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #110 on: July 15, 2017, 08:45:36 PM »
Low cloud cover (LCC) is associated with negative climate change feedback; thus the finding of the linked reference that LCC decreases with continued warming indicates that ECS is likely higher than assumed by AR5:

Daniel T. McCoy, Ryan Eastman, Dennis L. Hartmann, and Robert Wood (2017), “The Change in Low Cloud Cover in a Warmed Climate Inferred from AIRS, MODIS, and ERA-Interim”, Journal of Climate, https://doi.org/10.1175/JCLI-D-15-0734.1

http://journals.ametsoc.org/doi/10.1175/JCLI-D-15-0734.1

Abstract: “Decreases in subtropical low cloud cover (LCC) occur in climate model simulations of global warming. In this study 8-day-averaged observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Atmospheric Infrared Sounder (AIRS) spanning 2002–14 are combined with European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis to compute the dependence of the observed variability of LCC on various predictor variables. Large-scale thermodynamic and dynamic predictors of LCC are selected based on insight from large-eddy simulations (LESs) and observational analysis. It is found that increased estimated inversion strength (EIS) is associated with increased LCC. Drying of the free troposphere is associated with decreased LCC. Decreased LCC accompanies subsidence in regions of relatively low EIS; the opposite is found in regions of high EIS. Finally, it is found that increasing sea surface temperature (SST) leads to a decrease in LCC. These results are in keeping with previous studies of monthly and annual data. Based upon the observed response of LCC to natural variability of the control parameters, the change in LCC is estimated for an idealized warming scenario where SST increases by 1 K and EIS increases by 0.2 K. For this change in EIS and SST the LCC is inferred to decrease by 0.5%–2.7% when the regression models are trained on data observed between 40°S and 40°N and by 1.1%–1.4% when trained on data from trade cumulus–dominated regions. When the data used to train the regression model are restricted to stratocumulus-dominated regions the change in LCC is highly uncertain and varies between −1.6% and +1.4%, depending on the stratocumulus-dominated region used to train the regression model.”
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #111 on: July 21, 2017, 05:07:48 PM »
In the way of color commentary, it seems to me that the linked reference (and associated article) about biospheric feedback effect in a synchronously coupled model of human and Earth system is a play to try to document the potential validity of negative emissions technology like BECCS using ACME (Phase 1).  While ACME tries to account for the impact of phosphorous on the biosphere, I am concerned that much of their focus on BECCS is just happy talk, which will not prevent a socio-economic collapse in the 2050 to 2060 timeframe.

Peter E. Thornton et al, Biospheric feedback effects in a synchronously coupled model of human and Earth systems, Nature Climate Change (2017). DOI: 10.1038/nclimate3310

http://www.nature.com/nclimate/journal/v7/n7/full/nclimate3310.html?foxtrotcallback=true

Abstract: "Fossil fuel combustion and land-use change are the two largest contributors to industrial-era increases in atmospheric CO 2 concentration. Projections of these are thus fundamental inputs for coupled Earth system models (ESMs) used to estimate the physical and biological consequences of future climate system forcing. While historical data sets are available to inform past and current climate analyses, assessments of future climate change have relied on projections of energy and land use from energy–economic models, constrained by assumptions about future policy, land-use patterns and socio-economic development trajectories. Here we show that the climatic impacts on land ecosystems drive significant feedbacks in energy, agriculture, land use and carbon cycle projections for the twenty-first century. We find that exposure of human-appropriated land ecosystem productivity to biospheric change results in reductions of land area used for crops; increases in managed forest area and carbon stocks; decreases in global crop prices; and reduction in fossil fuel emissions for a low–mid-range forcing scenario. The feedbacks between climate-induced biospheric change and human system forcings to the climate system—demonstrated here—are handled inconsistently, or excluded altogether, in the one-way asynchronous coupling of energy–economic models to ESMs used to date."

See also the associated linked article entitled:  Titan simulations show importance of close two-way coupling between human and Earth systems"

https://phys.org/news/2017-07-titan-simulations-importance-two-way-coupling.html

Extract: "Through the Advanced Scientific Computing Research Leadership Computing Challenge program, Thornton's team was awarded 85 million compute hours to improve the Accelerated Climate Modeling for Energy (ACME) effort, a project sponsored by the Earth System Modeling program within DOE's Office of Biological and Environmental Research. Currently, ACME collaborators are focused on developing an advanced climate model capable of simulating 80 years of historic and future climate variability and change in 3 weeks or less of computing effort.

Now in its third year, the project has achieved several milestones—notably the development of ACME version 1 and the successful inclusion of human factors in one of its component models, the iESM.

"What's unique about ACME is that it's pushing the system to a higher resolution than has been attempted before," Thornton said. "It's also pushing toward a more comprehensive simulation capability by including human dimensions and other advances, yielding the most detailed Earth system models to date.

The development of iESM started before the ACME initiative when a multilaboratory team aimed to add new human dimensions—such as how people affect the planet to produce and consume energy—to Earth system models. The model—now a part of the ACME human dimensions component—is being merged with ACME in preparation for ACME version 2.

ACME version 1 will be publicly released in late-2017 for analysis and use by other researchers. Results from the model will also contribute to the Coupled Model Intercomparison Project, which provides foundational material for climate change assessment reports."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #112 on: July 29, 2017, 08:45:48 PM »
In my last post (Reply #111), I expressed my concern that under Rick Perry's supervision, the DOE's ACME projections may very likely make too optimistic assumptions about what they call: "Biospheric feedback effects in a synchronously coupled model of human and Earth systems", which I take to be code language for assumed negative emissions technology associated with wide scale use of BECCS.  In this post I provide likes to evidence that coming climate change would likely have negative impacts on any such BECCS due to such considerations as: extreme weather events, changes in precipitation patterns and eutrophication of water resources/bodies:


M Zampieri, A Ceglar, F Dentener, A Toreti. Wheat yield loss attributable to heat waves, drought and water excess at the global, national and subnational scales. Environmental Research Letters, 2017; 12 (6): 064008 DOI: 10.1088/1748-9326/aa723b

http://iopscience.iop.org/article/10.1088/1748-9326/aa723b/meta;jsessionid=D378EF4B95BF302736DCF87FBB2ED691.ip-10-40-1-105

Abstract
Heat waves and drought are often considered the most damaging climatic stressors for wheat. In this study, we characterize and attribute the effects of these climate extremes on wheat yield anomalies (at global and national scales) from 1980 to 2010. Using a combination of up-to-date heat wave and drought indexes (the latter capturing both excessively dry and wet conditions), we have developed a composite indicator that is able to capture the spatio-temporal characteristics of the underlying physical processes in the different agro-climatic regions of the world. At the global level, our diagnostic explains a significant portion (more than 40%) of the inter-annual production variability. By quantifying the contribution of national yield anomalies to global fluctuations, we have found that just two concurrent yield anomalies affecting the larger producers of the world could be responsible for more than half of the global annual fluctuations. The relative importance of heat stress and drought in determining the yield anomalies depends on the region. Moreover, in contrast to common perception, water excess affects wheat production more than drought in several countries. We have also performed the same analysis at the subnational level for France, which is the largest wheat producer of the European Union, and home to a range of climatic zones. Large subnational variability of inter-annual wheat yield is mostly captured by the heat and water stress indicators, consistently with the country-level result.

See also:

https://www.sciencedaily.com/releases/2017/07/170704094104.htm

"Extreme weather conditions and climate change account for 40% of global wheat production variability
Date: July 4, 2017
Source: European Commission, Joint Research Centre (JRC)
Summary: A new approach for identifying the impacts of climate change and extreme weather on the variability of global and regional wheat production has been proposed by researchers. The study analyzed the effect of heat and water anomalies on crop losses over a 30-year period."

&

E. Sinha, A. M. Michalak & V. Balaji (28 Jul 2017), "Eutrophication will increase during the 21st century as a result of precipitation changes", Science, Vol. 357, Issue 6349, pp. 405-408, DOI: 10.1126/science.aan2409

http://science.sciencemag.org/content/357/6349/405

"More rain means more pollution
Nitrogen input from river runoff is a major cause of eutrophication in estuaries and coastal waters. This is a serious problem that is widely expected to intensify as climate change strengthens the hydrological cycle. To address the current lack of adequate analysis, Sinha et al. present estimates of riverine nitrogen loading for the continental United States, based on projections of precipitation derived from climate models (see the Perspective by Seitzinger and Phillips). Anticipated changes in precipitation patterns are forecast to cause large and robust increases in nitrogen fluxes by the end of the century.
Science, this issue p. 405; see also p. 350

Abstract
Eutrophication, or excessive nutrient enrichment, threatens water resources across the globe. We show that climate change–induced precipitation changes alone will substantially increase (19 ± 14%) riverine total nitrogen loading within the continental United States by the end of the century for the “business-as-usual” scenario. The impacts, driven by projected increases in both total and extreme precipitation, will be especially strong for the Northeast and the corn belt of the United States. Offsetting this increase would require a 33 ± 24% reduction in nitrogen inputs, representing a massive management challenge. Globally, changes in precipitation are especially likely to also exacerbate eutrophication in India, China, and Southeast Asia. It is therefore imperative that water quality management strategies account for the impact of projected future changes in precipitation on nitrogen loading."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #113 on: July 29, 2017, 09:48:10 PM »
As a follow-on to my last two posts, the linked reference concludes that: "A key conclusion is that, regardless of the biomass and region studied, the sustainability of BECCS relies heavily on intelligent management of the supply chain."  Now ask yourself, with the DOE under the guidance of Rick Perry how intelligent do you think the implementation of BECCS is likely to be?

Mathilde Fajardy and Niall Mac Dowell (2017), "Can BECCS deliver sustainable and resource efficient negative emissions?", Energy & Environmental Science, 10, 1389-1426, DOI: 10.1039/C7EE00465F

http://pubs.rsc.org/en/Content/ArticleLanding/2017/EE/C7EE00465F#!divAbstract

Abstract
Negative emissions technologies (NETs) in general and bioenergy with CO2 capture and storage (BECCS) in particular are commonly regarded as vital yet controversial to meeting our climate goals. In this contribution we present a whole-systems analysis of the BECCS value chain associated with cultivation, harvesting, transport and conversion in dedicated biomass power stations in conjunction with CCS, of a range of biomass resources – both dedicated energy crops (miscanthus, switchgrass, short rotation coppice willow), and agricultural residues (wheat straw). We explicitly consider the implications of sourcing the biomass from different regions, climates and land types. The water, carbon and energy footprints of each value chain were calculated, and their impact on the overall system water, carbon and power efficiencies was evaluated. An extensive literature review was performed and a statistical analysis of the available data is presented. In order to describe the dynamic greenhouse gas balance of such a system, a yearly accounting of the emissions was performed over the lifetime of a BECCS facility, and the carbon “breakeven time” and lifetime net CO2 removal from the atmosphere were determined. The effects of direct and indirect land use change were included, and were found to be a key determinant of the viability of a BECCS project. Overall we conclude that, depending on the conditions of its deployment, BECCS could lead to both carbon positive and negative results. The total quantity of CO2 removed from the atmosphere over the project lifetime and the carbon breakeven time were observed to be highly case specific. This has profound implications for the policy frameworks required to incentivise and regulate the widespread deployment of BECCS technology. The results of a sensitivity analysis on the model combined with the investigation of alternate supply chain scenarios elucidated key levers to improve the sustainability of BECCS: (1) measuring and limiting the impacts of direct and indirect land use change, (2) using carbon neutral power and organic fertilizer, (3) minimising biomass transport, and prioritising sea over road transport, (4) maximising the use of carbon negative fuels, and (5) exploiting alternative biomass processing options, e.g., natural drying or torrefaction. A key conclusion is that, regardless of the biomass and region studied, the sustainability of BECCS relies heavily on intelligent management of the supply chain.

P.S.: I note that while BECCS sounds "green", we would do well to remember that under our current global market economic system, agriculture is among the largest contributors to global warming, emitting more GHGs worldwide than all cars, trucks, trains and airplanes combined.  Thus as the linked reference warns, the widespread worldwide implementation of BECCS has the potential for serving as a net carbon source rather than a net carbon sink; especially when considering the likely negative impacts (which are nonlinear with growing GMSTA) of continuing climate change on BECCS.
« Last Edit: July 30, 2017, 05:10:00 AM by AbruptSLR »
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #114 on: July 30, 2017, 05:11:04 AM »
As a follow-on to my last three posts, the linked article makes it clear that relying on BECCS as a magic bullet to solve climate change is a very bad bet:

Title: “Failure of Kemper County “clean coal” plant casts more doubts on BECCS”

http://www.geoengineeringmonitor.org/2017/07/failure-of-kemper-county-clean-coal-plant-casts-more-doubts-on-beccs/

Extract: “The project’s failure should cast serious doubts on the prospects of both “clean coal” as well as Bioenergy with Carbon Capture and Storage (BECCS) – the current star child of techno-fix solutions to climate change.

BECCS would involve capturing CO2 from biofuel refineries or biomass-burning power stations and pumping it into geological formations, or – more likely due to economics – pumping it into oil wells in order to extract more oil. Despite lack of evidence as to the technological and economic viability of BECCS, the models underpinning the Paris Agreement’s 2°C target overwhelmingly rely upon BECCS as a “negative emissions technology” capable of being deployed at a scale large enough to balance out emissions by mid-century.

The failure of the Kemper County project, which featured the cleanest and most efficient CCS power plant technology, should therefore be seen as a warning for policy-makers expecting CCS – including BECCS – technologies to magically close the emissions gap by mid-century.

It’s important to note that exchanging biomass for coal would add even more challenges to an IGCC with CCS plant. Biomass gasification results in a syngas which is chemically quite different from that generated through coal gasification, and therefore requires different treatment in order to produce a gas clean enough for burning to power a gas turbine.”
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #115 on: July 30, 2017, 07:54:43 PM »
My last post indicates that BECCS is not economically/technically practicable; however, I suspect that governments will find the use of geoengineering irresistible circa 2040 to 2060.  Therefore, I provide a link to the referenced research of the first climate model examination of 'cocktail geoengineering' using a combination of: "… stratospheric sulfate aerosol increase (SAI) that deflects sunlight to space and cirrus cloud thinning (CCT) that enables more longwave radiation to escape to space."  The study finds that combining both SAI & CCT can restore both GMSTA and total global precipitation back to pre-industrial levels, it finds that the regional patterns would be substantially different.  Thus, I would not be surprised that the DOE will authorize an ACME Phase II in 2018 that includes modeling capabilities to study such 'cocktail geoengineering' proposal in greater detail.  That said, I am concerned that any such studies will not consider Hansen's ice-climate feedback from a potential collapse of the WAIS this century; which would like mean that any implementation of such 'cocktail geoengineering' plans would be misguided, and potential worse than if they had not been implemented:

Long Cao, Lei Duan, Govindasamy Bala & Ken Caldeira (2017), "Simultaneous stabilization of global temperature and precipitation through cocktail geoengineering", Geophysical Research Letters. DOI: 10.1002/2017GL074281

http://onlinelibrary.wiley.com/doi/10.1002/2017GL074281/abstract;jsessionid=CD4EEF992F073831F2A191EFA5491888.f03t02

Abstract: "Solar geoengineering has been proposed as a backup plan to offset some aspects of anthropogenic climate change if timely CO2 emission reductions fail to materialize. Modeling studies have shown that there are trade-offs between changes in temperature and hydrological cycle in response to solar geoengineering. Here we investigate the possibility of stabilizing both global mean temperature and precipitation simultaneously by combining two geoengineering approaches: stratospheric sulfate aerosol increase (SAI) that deflects sunlight to space and cirrus cloud thinning (CCT) that enables more longwave radiation to escape to space. Using the slab ocean configuration of National Center for Atmospheric Research Community Earth System Model, we simulate SAI by uniformly adding sulfate aerosol in the upper stratosphere and CCT by uniformly increasing cirrus cloud ice particle falling speed. Under an idealized warming scenario of abrupt quadrupling of atmospheric CO2, we show that by combining appropriate amounts of SAI and CCT geoengineering, global mean (or land mean) temperature and precipitation can be restored simultaneously to preindustrial levels. However, compared to SAI, cocktail geoengineering by mixing SAI and CCT does not markedly improve the overall similarity between geoengineered climate and preindustrial climate on regional scales. Some optimal spatially nonuniform mixture of SAI with CCT might have the potential to better mitigate climate change at both the global and regional scales."

Plain Language Summary: "Increases in atmospheric carbon dioxide cause increase in both global temperatures and precipitation. Solar geoengineering has been proposed as a means to counteract this climate change by deliberately deflecting more sunlight from the Earth's climate system. Numerous climate modeling studies have shown that proposed solar geoengineering schemes, such as injection of sulfate aerosols into the stratosphere, can cool climate, but the amount of precipitation change per degree of temperature change is greater than that for CO2, meaning that such proposals cannot simultaneously globally restore both average temperatures and average precipitation. It has also been suggested that the Earth could be cooled by thinning cirrus clouds, but the amount of precipitation change per degree of temperature change for this method is less than that for CO2. Our climate modeling study shows, for the first time, that a cocktail of these two approaches would decrease precipitation and temperature in the same ratios as they are increased by CO2, which would allow simultaneous recovery of preindustrial temperature and precipitation in a high CO2 world at global scale. We show that although the average temperatures and precipitation can be recovered at global scale, substantial differences between the geoengineered and natural climates persist at regional scale."

See also: "Could 'cocktail geoengineering' save the climate?"

https://phys.org/news/2017-07-cocktail-geoengineering-climate.html

Extract: "The team—which includes Carnegie's Ken Caldeira, Long Cao and Lei Duan of Zhejiang University, and Govindasamy Bala of the Indian Institute of Science—used models to simulate what would happen if sunlight were scattered by particles at the same time as the cirrus clouds were thinned. They wanted to understand how effective this combined set of tools would be at reversing climate change, both globally and regionally.

The good news is that their simulations showed that if both methods are deployed in concert, it would decrease warming to pre-industrial levels, as desired, and on a global level rainfall would also stay at pre-industrial levels. But the bad news is that while global average climate was largely restored, substantial differences remained locally, with some areas getting much wetter and other areas getting much drier."

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #116 on: August 02, 2017, 03:21:58 AM »
The linked references & associated article indicate that subglacial lakes in Antarctica make the ice flow faster & indicate that the glacial models need to be upgraded to account for this observed behavior:

Kuhn, G., Hillenbrand, C.-D., Kasten, S., Smith, J. A., Nitsche, F. O., Frederichs, T., Wiers, S., Ehrmann, W., Klages, J. P., Mogollón, J. M.: Evidence for a palaeo-subglacial lake on the Antarctic continental shelf. Nature Communications. DOI: 10.1038/NCOMMS15591

&

Graham, A. G. C., Kuhn, G., Meisel, O., Hillenbrand, C.-D., Hodgson, D. A., Ehrmann, W., Wacker, L., Wintersteller, P., dos Santos Ferreira, C., Römer, M., White, D., Bohrmann, G.: Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation. Nature Communications 8, 14798, DOI: 10.1038/ncomms14798

See also:

https://phys.org/news/2017-06-meltwater-lakes-antarctic-ice-sheet.html

Extract: “Satellite-monitoring shows that the movement of water from one lake to another can cause glaciers draining the Antarctic Ice Sheet to move more quickly. "This aspect needs to be taken into account in models designed to make predictions on the future behaviour and dynamics of ice masses, and with them, the degree to which the sea level will rise," explains AWI marine geologist Kuhn.”
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #117 on: August 05, 2017, 04:38:50 PM »
The linked reference emphasizes that climate models need more calibration in order to adequately account for long-term ocean heat content variability and its impacts on GMSTA this century:

de Boisséson, E., Balmaseda, M.A. & Mayer, M. (2017), "Ocean heat content variability in an ensemble of twentieth century ocean reanalyses", Clim Dyn, https://doi.org/10.1007/s00382-017-3845-0

https://link.springer.com/article/10.1007%2Fs00382-017-3845-0?utm_content=buffered755&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "This paper presents a ten-member ensemble of twentieth century Ocean ReAnalyses called ORA-20C. ORA-20C assimilates temperature and salinity profiles and is forced by the ECMWF twentieth century atmospheric reanalysis (ERA-20C) over the 1900–2010 period. This study attempts to identify robust signals of ocean heat content change in ORA-20C and detect contamination by model errors, initial condition uncertainty, surface fluxes and observing system changes. It is shown that ORA-20C trends and variability in the first part of the century result from the surface fluxes and model drift towards a warmer mean state and weak meridional overturning circulation. The impact of the observing system in correcting the mean state causes the deceleration of the warming trend and alters the long-term climate signal. The ensemble spread reflects the long-lasting memory of the initial conditions and the convergence of the system to a solution compatible with surface fluxes, the ocean model and observational constraints. Observations constrain the ocean heat uptake trend in the last decades of the twentieth century, which is similar to trend estimations from the post-satellite era. An ocean heat budget analysis attributes ORA-20C heat content changes to surface fluxes in the first part of the century. The heat flux variability reflects spurious signals stemming from ERA-20C surface fields, which in return result from changes in the atmospheric observing system. The influence of the temperature assimilation increments on the heat budget is growing with time. Increments control the most recent ocean heat uptake signals, highlighting imbalances in forced reanalysis systems in the ocean as well as in the atmosphere."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #118 on: August 08, 2017, 05:10:34 PM »
Many people do not focus very much on the impact of global warming on both ocean ventilation and on deoxygenation; largely because current climate models do not project significant changes (w.r.t. impacts on humans) in the near-term.  That said, I will post a series of references indicating that our current state of the art Earth System Models significantly under estimate the currently observed impacts and associated mechanisms for ocean ventilation and deoxygenation.  I begin with the linked reference that indicates while there is still meaningful uncertainties, the potential impacts of both ocean ventilation and deoxygenation are large on different timeframes:

John G. Shepherd, Peter G. Brewer, Andreas Oschlies, Andrew J. Watson (7 August 2017), "Ocean ventilation and deoxygenation in a warming world: introduction and overview", Philosophical Transactions of the Royal Society A, DOI: 10.1098/rsta.2017.0240

http://rsta.royalsocietypublishing.org/content/375/2102/20170240

Abstract: "Changes of ocean ventilation rates and deoxygenation are two of the less obvious but important indirect impacts expected as a result of climate change on the oceans. They are expected to occur because of (i) the effects of increased stratification on ocean circulation and hence its ventilation, due to reduced upwelling, deep-water formation and turbulent mixing, (ii) reduced oxygenation through decreased oxygen solubility at higher surface temperature, and (iii) the effects of warming on biological production, respiration and remineralization. The potential socio-economic consequences of reduced oxygen levels on fisheries and ecosystems may be far-reaching and significant. At a Royal Society Discussion Meeting convened to discuss these matters, 12 oral presentations and 23 posters were presented, covering a wide range of the physical, chemical and biological aspects of the issue. Overall, it appears that there are still considerable discrepancies between the observations and model simulations of the relevant processes. Our current understanding of both the causes and consequences of reduced oxygen in the ocean, and our ability to represent them in models are therefore inadequate, and the reasons for this remain unclear. It is too early to say whether or not the socio-economic consequences are likely to be serious. However, the consequences are ecologically, biogeochemically and climatically potentially very significant, and further research on these indirect impacts of climate change via reduced ventilation and oxygenation of the oceans should be accorded a high priority.

This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #119 on: August 08, 2017, 05:13:21 PM »
The next post in this series, cites a reference that indicates that human impacts on the phosphorus cycle could contribute to positive feedbacks for more deoxygenation, that could last for thousands of years once triggered:

Andrew J. Watson, Timothy M. Lenton, Benjamin J. W. Mills (7 August 2017), "Ocean deoxygenation, the global phosphorus cycle and the possibility of human-caused large-scale ocean anoxia", Philosophical Transactions of the Royal Society A, DOI: 10.1098/rsta.2016.0318

http://rsta.royalsocietypublishing.org/content/375/2102/20160318

Abstract: "The major biogeochemical cycles that keep the present-day Earth habitable are linked by a network of feedbacks, which has led to a broadly stable chemical composition of the oceans and atmosphere over hundreds of millions of years. This includes the processes that control both the atmospheric and oceanic concentrations of oxygen. However, one notable exception to the generally well-behaved dynamics of this system is the propensity for episodes of ocean anoxia to occur and to persist for 105–106 years, these ocean anoxic events (OAEs) being particularly associated with warm ‘greenhouse’ climates. A powerful mechanism responsible for past OAEs was an increase in phosphorus supply to the oceans, leading to higher ocean productivity and oxygen demand in subsurface water. This can be amplified by positive feedbacks on the nutrient content of the ocean, with low oxygen promoting further release of phosphorus from ocean sediments, leading to a potentially self-sustaining condition of deoxygenation. We use a simple model for phosphorus in the ocean to explore this feedback, and to evaluate the potential for humans to bring on global-scale anoxia by enhancing P supply to the oceans. While this is not an immediate global change concern, it is a future possibility on millennial and longer time scales, when considering both phosphate rock mining and increased chemical weathering due to climate change. Ocean deoxygenation, once begun, may be self-sustaining and eventually could result in long-lasting and unpleasant consequences for the Earth's biosphere.

This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #120 on: August 08, 2017, 05:17:10 PM »
The next reference in this series, discusses the sensitivity of deoxygenation patterns in the ocean subjected to both natural and anthropogenic forcing.  The reference finds that particularly portions of the ocean with tropical thermoclines are more sensitive than current models project:

Andreas Oschlies, Olaf Duteil, Julia Getzlaff, Wolfgang Koeve, Angela Landolfi, Sunke Schmidtko (7 August 2017), "Patterns of deoxygenation: sensitivity to natural and anthropogenic drivers", Philosophical Transactions of the Royal Society A, DOI: 10.1098/rsta.2016.0325

http://rsta.royalsocietypublishing.org/content/375/2102/20160325

Abstract: "Observational estimates and numerical models both indicate a significant overall decline in marine oxygen levels over the past few decades. Spatial patterns of oxygen change, however, differ considerably between observed and modelled estimates. Particularly in the tropical thermocline that hosts open-ocean oxygen minimum zones, observations indicate a general oxygen decline, whereas most of the state-of-the-art models simulate increasing oxygen levels. Possible reasons for the apparent model-data discrepancies are examined. In order to attribute observed historical variations in oxygen levels, we here study mechanisms of changes in oxygen supply and consumption with sensitivity model simulations. Specifically, the role of equatorial jets, of lateral and diapycnal mixing processes, of changes in the wind-driven circulation and atmospheric nutrient supply, and of some poorly constrained biogeochemical processes are investigated. Predominantly wind-driven changes in the low-latitude oceanic ventilation are identified as a possible factor contributing to observed oxygen changes in the low-latitude thermocline during the past decades, while the potential role of biogeochemical processes remains difficult to constrain. We discuss implications for the attribution of observed oxygen changes to anthropogenic impacts and research priorities that may help to improve our mechanistic understanding of oxygen changes and the quality of projections into a changing future.

This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #121 on: August 08, 2017, 05:20:53 PM »
The next reference in this series indicates that current climate models do not adequately account for all of the mechanisms for ocean ventilation in the high-latitude oceans.  This adds a significant area of risk of potential negative impacts due to continued global warming:

Alberto C. Naveira Garabato, Graeme A.  MacGilchrist, Peter J. Brown, D. Gwyn Evans, Andrew J. S. Meijers, Jan D. Zika (7 August 2017), "High-latitude ocean ventilation and its role in Earth's climate transitions", Philosophical Transactions of the Royal Society A, DOI: 10.1098/rsta.2016.0324

http://rsta.royalsocietypublishing.org/content/375/2102/20160324?utm_content=buffer039b9&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "The processes regulating ocean ventilation at high latitudes are re-examined based on a range of observations spanning all scales of ocean circulation, from the centimetre scales of turbulence to the basin scales of gyres. It is argued that high-latitude ocean ventilation is controlled by mechanisms that differ in fundamental ways from those that set the overturning circulation. This is contrary to the assumption of broad equivalence between the two that is commonly adopted in interpreting the role of the high-latitude oceans in Earth's climate transitions. Illustrations of how recognizing this distinction may change our view of the ocean's role in the climate system are offered.

This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #122 on: August 08, 2017, 05:23:30 PM »
My last reference in this current series indicates that deep convection mechanisms can develop in the Arctic Ocean with continued anthropogenic global warming; which would increase ocean ventilation:

Lique, C., Johnson, H.L. & Plancherel, Y. (2017), "Emergence of deep convection in the Arctic Ocean under a warming climate", Clim Dyn, DOI https://doi.org/10.1007/s00382

https://rd.springer.com/article/10.1007%2Fs00382-017-3849-9?utm_content=buffer841ba&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "The appearance of winter deep mixed layers in the Arctic Ocean under a warming climate is investigated with the HiGEM coupled global climate model. In response to a four times increase of atmospheric CO 2 levels with respect to present day conditions, the Arctic Basin becomes seasonally ice-free. Its surface becomes consequently warmer and, on average, slightly fresher. Locally, changes in surface salinity can be far larger (up to 4 psu) than the basin-scale average, and of a different sign. The Canadian Basin undergoes a strong freshening, while the Eurasian Basin undergoes strong salinification. These changes are driven by the spin up of the surface circulation, likely resulting from the increased transfer of momentum to the ocean as sea ice cover is reduced. Changes in the surface salinity field also result in a change in stratification, which is strongly enhanced in the Canadian Basin and reduced in the Eurasian Basin. Reduction, or even suppression, of the stratification in the Eurasian Basin produces an environment that is favourable for, and promotes the appearance of, deep convection near the sea ice edge, leading to a significant deepening of winter mixed layers in this region (down to 1000 m). As the Arctic Ocean is transitioning toward a summer ice-free regime, new dynamical ocean processes will appear in the region, with potentially important consequences for the Arctic Ocean itself and for climate, both locally and on larger scales."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #123 on: August 08, 2017, 06:30:46 PM »
The linked reference indicates that the color of melt ponds on Arctic sea ice is a better indicator of ice thickness than current means of remotely measuring sea ice thickness.  This could help to better calibrate climate models:

Lu, P., Leppäranta, M., Cheng, B., Li, Z., Istomina, L., and Heygster, G.: The color of melt ponds on Arctic sea ice, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-117, in review, 2017.

https://www.the-cryosphere-discuss.net/tc-2017-117/

Abstract. Pond color, which creates the visual appearance of melt ponds on Arctic sea ice in summer, is quantitatively investigated in this study. A two-stream radiative transfer model is used for ponded sea ice: the upwelling irradiance from the pond surface is determined, and then the upwelling spectrum is transformed into the RGB color space through a colorimetric method. The dependence of pond color on various factors such as water and ice properties and incident solar radiation is investigated. The results reveal that increasing underlying ice thickness Hi enhances both the green and blue components of pond color, whereas the red component is mostly sensitive to Hi for thin ice (Hi < 1.5 m) and to pond depth Hp for thick ice (Hi > 1.5 m), similar to the behavior of melt-pond albedo. The distribution of the incident solar spectrum F0 with wavelength affects the pond color rather than its level. The pond color changes from dark blue to brighter blue with increasing scattering in ice, but the influence of absorption in ice on pond color is limited. The pond color reproduced by the model agrees well with field observations on Arctic sea ice in summer, which supports the validity of this study. More importantly, pond color has been confirmed to contain information about meltwater and underlying ice, and therefore it can be used as an index to retrieve Hi and Hp. The results show that retrievals of Hi for thin ice agree better with field measurements than retrievals for thick ice, but that retrievals of Hp are not good. Color has been shown to be a new potential method to obtain ice thickness information, especially for melting sea ice in summer, although more validation data and improvements to the radiative transfer model will be needed in future.
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #124 on: August 09, 2017, 05:57:50 PM »
Hopefully, the findings of the linked reference will be used to improve modeling of cloud feedback:

Stanford, M. W., Varble, A., Zipser, E., Strapp, J. W., Leroy, D., Schwarzenboeck, A., Potts, R., and Protat, A.: A ubiquitous ice size bias in simulations of tropical deep convection, Atmos. Chem. Phys., 17, 9599-9621, https://doi.org/10.5194/acp-17-9599-2017, 2017.

https://www.atmos-chem-phys.net/17/9599/2017/

Abstract. The High Altitude Ice Crystals – High Ice Water Content (HAIC-HIWC) joint field campaign produced aircraft retrievals of total condensed water content (TWC), hydrometeor particle size distributions (PSDs), and vertical velocity (w) in high ice water content regions of mature and decaying tropical mesoscale convective systems (MCSs). The resulting dataset is used here to explore causes of the commonly documented high bias in radar reflectivity within cloud-resolving simulations of deep convection. This bias has been linked to overly strong simulated convective updrafts lofting excessive condensate mass but is also modulated by parameterizations of hydrometeor size distributions, single particle properties, species separation, and microphysical processes. Observations are compared with three Weather Research and Forecasting model simulations of an observed MCS using different microphysics parameterizations while controlling for w, TWC, and temperature. Two popular bulk microphysics schemes (Thompson and Morrison) and one bin microphysics scheme (fast spectral bin microphysics) are compared. For temperatures between −10 and −40 °C and TWC  >  1 g m−3, all microphysics schemes produce median mass diameters (MMDs) that are generally larger than observed, and the precipitating ice species that controls this size bias varies by scheme, temperature, and w. Despite a much greater number of samples, all simulations fail to reproduce observed high-TWC conditions ( >  2 g m−3) between −20 and −40 °C in which only a small fraction of condensate mass is found in relatively large particle sizes greater than 1 mm in diameter. Although more mass is distributed to large particle sizes relative to those observed across all schemes when controlling for temperature, w, and TWC, differences with observations are significantly variable between the schemes tested. As a result, this bias is hypothesized to partly result from errors in parameterized hydrometeor PSD and single particle properties, but because it is present in all schemes, it may also partly result from errors in parameterized microphysical processes present in all schemes. Because of these ubiquitous ice size biases, the frequently used microphysical parameterizations evaluated in this study inherently produce a high bias in convective reflectivity for a wide range of temperatures, vertical velocities, and TWCs.
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #125 on: August 15, 2017, 12:18:02 AM »
The linked reference discusses methodology for improving the calibration of models to paleodata:

Walter A. Perkins and Gregory J. Hakim (2017), "Reconstructing paleoclimate fields using online data assimilation with a linear inverse model", Clim. Past, 13, 421–436, doi:10.5194/cp-13-421-2017

https://www.clim-past.net/13/421/2017/cp-13-421-2017.pdf

Abstract. We examine the skill of a new approach to climate field reconstructions (CFRs) using an online paleoclimate data assimilation (PDA) method. Several recent studies have foregone climate model forecasts during assimilation due to the computational expense of running coupled global climate models (CGCMs) and the relatively low skill of these forecasts on longer timescales. Here we greatly diminish the computational cost by employing an empirical forecast model (linear inverse model, LIM), which has been shown to have skill comparable to CGCMs for forecasting annualto- decadal surface temperature anomalies. We reconstruct annual-average 2m air temperature over the instrumental period (1850–2000) using proxy records from the PAGES 2k Consortium Phase 1 database; proxy models for estimating proxy observations are calibrated on GISTEMP surface temperature analyses. We compare results for LIMs calibrated using observational (Berkeley Earth), reanalysis (20th Century Reanalysis), and CMIP5 climate model (CCSM4 and MPI) data relative to a control offline reconstruction method. Generally, we find that the usage of LIM forecasts for online PDA increases reconstruction agreement with the instrumental record for both spatial fields and global mean temperature (GMT). Specifically, the coefficient of efficiency (CE) skill metric for detrended GMT increases by an average of 57% over the offline benchmark. LIM experiments display a common pattern of skill improvement in the spatial fields over Northern Hemisphere land areas and in the high-latitude North Atlantic–Barents Sea corridor. Experiments for non- CGCM-calibrated LIMs reveal region-specific reductions in spatial skill compared to the offline control, likely due to aspects of the LIM calibration process. Overall, the CGCM calibrated LIMs have the best performance when considering both spatial fields and GMT. A comparison with the persistence forecast experiment suggests that improvements are associated with the linear dynamical constraints of the forecast and not simply persistence of temperature anomalies.
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #126 on: August 18, 2017, 05:57:29 PM »
The linked reference discusses work to better calibrate GCM projections using PETM paleodata associated with hydrological and biogeochemical consequences of rapid global warming:

Matthew J. Carmichael et. al. (2017), "Hydrological and associated biogeochemical consequences of rapid global warming during the Paleocene-Eocene Thermal Maximum", Global and Planetary Change, https://doi.org/10.1016/j.gloplacha.2017.07.014

http://www.sciencedirect.com/science/article/pii/S0921818117300723

Abstract: "The Paleocene-Eocene Thermal Maximum (PETM) hyperthermal, ~ 56 million years ago (Ma), is the most dramatic example of abrupt Cenozoic global warming. During the PETM surface temperatures increased between 5 and 9 °C and the onset likely took < 20 kyr. The PETM provides a case study of the impacts of rapid global warming on the Earth system, including both hydrological and associated biogeochemical feedbacks, and proxy data from the PETM can provide constraints on changes in warm climate hydrology simulated by general circulation models (GCMs). In this paper, we provide a critical review of biological and geochemical signatures interpreted as direct or indirect indicators of hydrological change at the PETM, explore the importance of adopting multi-proxy approaches, and present a preliminary model-data comparison. Hydrological records complement those of temperature and indicate that the climatic response at the PETM was complex, with significant regional and temporal variability. This is further illustrated by the biogeochemical consequences of inferred changes in hydrology and, in fact, changes in precipitation and the biogeochemical consequences are often conflated in geochemical signatures. There is also strong evidence in many regions for changes in the episodic and/or intra-annual distribution of precipitation that has not widely been considered when comparing proxy data to GCM output. Crucially, GCM simulations indicate that the response of the hydrological cycle to the PETM was heterogeneous – some regions are associated with increased precipitation – evaporation (P – E), whilst others are characterised by a decrease. Interestingly, the majority of proxy data come from the regions where GCMs predict an increase in PETM precipitation. We propose that comparison of hydrological proxies to GCM output can be an important test of model skill, but this will be enhanced by further data from regions of model-simulated aridity and simulation of extreme precipitation events."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #127 on: August 20, 2017, 07:31:33 PM »
Figure 5 of the reference on findings of the CloudSat & CALIPSO within the A-Train, so a dramatic increase (more positive) in observed net cloud feedback as compared to prior assumptions.  This of course means that ECS is higher than previously assumed.

Graeme Stephens et. al. (2017), "CloudSat and CALIPSO within the A-Train: Ten years of actively observing the Earth system", BAMS, https://doi.org/10.1175/BAMS-D-16-0324.1

http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-16-0324.1?utm_content=bufferebbb9&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer
or
http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-16-0324.1

Abstract: "The more than 10 years of observations jointly collected by CloudSat and CALIPSO satellites has resulted in new ways of looking at aerosol, clouds, and precipitation and new discoveries about processes that connect them.

One of the most successful demonstrations of an integrated approach to observe Earth from multiple perspectives is the A-Train satellite constellation (e.g. Stephens et al., 2002). The science enabled by this constellation flourished with the introduction of the two active sensors carried by the NASA CloudSat and the NASA/CNES Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellites that were launched together on April 28th, 2006. These two missions have provided a 10-year demonstration of coordinated formation flying that made it possible to develop integrated products and that offered new insights on key atmospheric processes. The progress achieved over this decade of observations, summarized in this paper, clearly demonstrate the fundamental importance of the vertical structure of clouds and aerosol for understanding the influences of the larger scale atmospheric circulation on aerosol, the hydrological cycle, the cloud-scale physics and on the formation of the major storm systems of Earth. The research also underscored inherent ambiguities in radiance data in describing cloud properties and how these active systems have greatly enhanced passive observation. It is now clear that monitoring the vertical structure of clouds and aerosol is essential and a climate data record is now being constructed. These pioneering efforts are to be continued with EarthCARE mission planned for launch in 2019."

Caption: "Figure 5 Upper three panels are from Hartmann et al (1992) who estimate the contribution to the cloud radiative effects (CRE) of five classes of clouds as defined according to the ISCCP radiance classification (upper left). The bottom panels are the equivalent analysis but with classification determined by the radar-lidar data of CloudSat and CALIPSO where true cloud heights establish the types and cloud thickness (x axis) are from water and ice path information which is proportional to cloud optical depth. The differences in CRE between this latter analysis and that of Hartmann et al underscores the effects of misclassification of clouds on the interpretation of their radiative effects. Ci=cirrus, D.C.=Deep Convection, M.L.=multi-layer, AS=Altostratus, AC-Alto-cumulus, NS=Nimbostratus, St=stratus, SC=stratocumulus and Cu=cumulus."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #128 on: August 21, 2017, 11:17:43 PM »
The linked website has abstracts from papers on carbon cycle feedback mechanisms at an August 24, 2017 conference entitled: "10th International Carbon Dioxide Conference 2017".  These findings could be used to help calibrate ESM projections:

https://www.conftool.com/icdc10/index.php?page=browseSessions&print=head&form_session=43

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #129 on: August 23, 2017, 04:21:22 PM »
The final results of the linked research on the influence of ocean spray on the atmosphere can but used in the future to help calibrate state-of-the-art ESM projections.  Until then I believe that uncertainty entails risk, and we would be wise to follow the Precautionary Principle.

Title: "The surprising effect of ocean waves on global climate"

https://ensia.com/articles/waves/

Extract: "Evidence mounts of the important role of sea spray in shaping Earth’s atmosphere"

See also:

Richard E.Cochran, et. al. (11 May 2017), "Molecular Diversity of Sea Spray Aerosol Particles: Impact of Ocean Biology on Particle Composition and Hygroscopicity", Chem, Volume 2, Issue 5, Pages 655-667, https://doi.org/10.1016/j.chempr.2017.03.007

http://www.sciencedirect.com/science/article/pii/S2451929417301201

Summary
"The impact of sea spray aerosol (SSA) on climate depends on the size and chemical composition of individual particles that make up the total SSA ensemble. There remains a lack of understanding as to the composition of individual particles within the SSA ensemble and how it changes in response to dynamic ocean biology. Here, we characterize the classes of organic compounds as well as specific molecules within individual SSA particles. The diversity of molecules within the organic fraction was observed to vary between submicrometer- and supermicrometer-sized particles and included contributions from fatty acids, monosaccharides, polysaccharides, and siliceous material. Significant changes in this molecular diversity were observed to coincide with the rise and fall of phytoplankton and heterotrophic bacteria populations within the seawater. Furthermore, the water uptake of individual particles was affected, as learned from studying the hygroscopicity of model systems composed of representative mixtures of salts and organic compounds."

&

Xiaofei Wang et. al. (2017),"The role of jet and film drops in controlling the mixing state of submicron sea spray aerosol particles", PNAS, vol. 114 no. 27,  6978–6983, doi: 10.1073/pnas.1702420114

http://www.pnas.org/content/114/27/6978.short

Abstract: "The oceans represent a significant global source of atmospheric aerosols. Sea spray aerosol (SSA) particles comprise sea salts and organic species in varying proportions. In addition to size, the overall composition of SSA particles determines how effectively they can form cloud droplets and ice crystals. Thus, understanding the factors controlling SSA composition is critical to predicting aerosol impacts on clouds and climate. It is often assumed that submicrometer SSAs are mainly formed by film drops produced from bursting bubble-cap films, which become enriched with hydrophobic organic species contained within the sea surface microlayer. In contrast, jet drops formed from the base of bursting bubbles are postulated to mainly produce larger supermicrometer particles from bulk seawater, which comprises largely salts and water-soluble organic species. However, here we demonstrate that jet drops produce up to 43% of total submicrometer SSA number concentrations, and that the fraction of SSA produced by jet drops can be modulated by marine biological activity. We show that the chemical composition, organic volume fraction, and ice nucleating ability of submicrometer particles from jet drops differ from those formed from film drops. Thus, the chemical composition of a substantial fraction of submicrometer particles will not be controlled by the composition of the sea surface microlayer, a major assumption in previous studies. This finding has significant ramifications for understanding the factors controlling the mixing state of submicrometer SSA particles and must be taken into consideration when predicting SSA impacts on clouds and climate."

&

M. E. Salter et. al. (3 August 2016), "Calcium enrichment in sea spray aerosol particles", Geophysical Research Letters, DOI: 10.1002/2016GL070275

http://onlinelibrary.wiley.com/doi/10.1002/2016GL070275/full

Abstract: "Sea spray aerosol particles are an integral part of the Earth's radiation budget. To date, the inorganic composition of nascent sea spray aerosol particles has widely been assumed to be equivalent to the inorganic composition of seawater. Here we challenge this assumption using a laboratory sea spray chamber containing both natural and artificial seawater, as well as with ambient aerosol samples collected over the central Arctic Ocean during summer. We observe significant enrichment of calcium in submicrometer (<1 μm in diameter) sea spray aerosol particles when particles are generated from both seawater sources in the laboratory as well as in the ambient aerosols samples. We also observe a tendency for increasing calcium enrichment with decreasing particle size. Our results suggest that calcium enrichment in sea spray aerosol particles may be environmentally significant with implications for our understanding of sea spray aerosol, its impact on Earth's climate, as well as the chemistry of the marine atmosphere."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #130 on: August 23, 2017, 06:12:15 PM »
Clouds are complex and it is a good idea to calibrate their response to global warming using the best parameters available, as discussed for low cloud cover in the linked reference:

Hideaki Kawai, Tsuyoshi Koshiro and Mark J. Webb (2017), "Interpretation of Factors Controlling Low Cloud Cover and Low Cloud Feedback Using a Unified Predictive Index", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0825.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0825.1?utm_content=buffer89d4d&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "This paper reports a new index for low cloud cover (LCC), the Estimated Cloud-Top Entrainment Index (ECTEI), which is a modification of estimated inversion strength (EIS) and takes into account a cloud top entrainment (CTE) criterion. Shipboard cloud observation data confirm that the index is strongly correlated with LCC. We argue here that changes in LCC cannot be fully determined from changes in EIS only, but can be better determined from changes in both EIS and sea surface temperature (SST) based on the ECTEI. Furthermore, we argue that various proposed predictors of LCC change, including the moist static energy vertical gradient, SST, and mid-level clouds, can be better understood from the perspective of the ECTEI."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #131 on: August 25, 2017, 02:01:33 AM »
The linked reference discusses the use of HIAPER data to help calibrate cloud modeling:

Wu, C., Liu, X., Diao, M., Zhang, K., Gettelman, A., Lu, Z., Penner, J. E., and Lin, Z. (2017), "Direct comparisons of ice cloud macro- and microphysical properties simulated by the Community Atmosphere Model version 5 with HIPPO aircraft observations", Atmos. Chem. Phys., 17, 4731-4749, https://doi.org/10.5194/acp-17-4731-2017, DOI: 10.5194/acp-17-4731-2017

https://www.atmos-chem-phys.net/17/4731/2017/

Abstract: "In this study we evaluate cloud properties simulated by the Community Atmosphere Model version 5 (CAM5) using in situ measurements from the HIAPER Pole-to-Pole Observations (HIPPO) campaign for the period of 2009 to 2011. The modeled wind and temperature are nudged towards reanalysis. Model results collocated with HIPPO flight tracks are directly compared with the observations, and model sensitivities to the representations of ice nucleation and growth are also examined. Generally, CAM5 is able to capture specific cloud systems in terms of vertical configuration and horizontal extension. In total, the model reproduces 79.8 % of observed cloud occurrences inside model grid boxes and even higher (94.3 %) for ice clouds (T ≤ −40 °C). The missing cloud occurrences in the model are primarily ascribed to the fact that the model cannot account for the high spatial variability of observed relative humidity (RH). Furthermore, model RH biases are mostly attributed to the discrepancies in water vapor, rather than temperature. At the micro-scale of ice clouds, the model captures the observed increase of ice crystal mean sizes with temperature, albeit with smaller sizes than the observations. The model underestimates the observed ice number concentration (Ni) and ice water content (IWC) for ice crystals larger than 75 µm in diameter. Modeled IWC and Ni are more sensitive to the threshold diameter for autoconversion of cloud ice to snow (Dcs), while simulated ice crystal mean size is more sensitive to ice nucleation parameterizations than to Dcs. Our results highlight the need for further improvements to the sub-grid RH variability and ice nucleation and growth in the model."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #132 on: September 01, 2017, 11:09:20 PM »
Given the importance of cloud feedback, the linked reference discusses key work to better correlate model and satellite data:

Swales, D. J., Pincus, R., and Bodas-Salcedo, A.: The Cloud Feedback Model Intercomparison Project Observational Simulator Package: Version 2 (COSP2), Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2017-148, in review, 2017.

https://www.geosci-model-dev-discuss.net/gmd-2017-148/
https://www.geosci-model-dev-discuss.net/gmd-2017-148/gmd-2017-148.pdf

Abstract. The Cloud Feedback Model Intercomparison Project Observational Simulator Package (COSP) gathers together a collection of observation proxies or satellite simulators that translate model-simulated cloud properties to synthetic observations as would be obtained by a range of satellite observing systems. This paper introduces COSP 2, an evolution focusing on more explicit and consistent separation between host model, coupling infrastructure, and individual observing proxies. Revisions also enhance flexibility by allowing for model-specific representation of sub-grid scale cloudiness, provide greater clarity by clearly separating tasks, support greater use of shared code and data including shared inputs across simulators, and follow more uniform software standards to simplify implementation across a wide range of platforms. The complete package including a testing suite is freely available.
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #133 on: September 06, 2017, 05:07:15 PM »
The linked reference presents paleo data from Greenland ice cores regarding oxidant levels during the last glacial-interglacial cycle, that can be used to help calibrate ESMs:

Geng et al (2017) "Isotropic evidence of multiple controls on atmospheric oxidants over climate transitions", Nature, Vol 546, Issue 7656, pp 133-136, doi:10.1038/nature22340

http://www.nature.com/nature/journal/v546/n7656/abs/nature22340.html?foxtrotcallback=true

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #134 on: September 06, 2017, 05:20:29 PM »
The linked reference helps to quantify one of the many different feedback mechanisms that contribute to Arctic Amplification.  Helpfully, this information can help to better calibrate ESM projections:

Kwang-Yul Kim et al (2017), "Understanding the Mechanism of Arctic Amplification and Sea Ice Loss", The Cryosphere Discuss., doi:10.5194/tc-2017-39, 2017

https://www.the-cryosphere-discuss.net/tc-2017-39/tc-2017-39.pdf

Abstract: "Sea ice reduction is accelerating in the Barents and Kara Seas. Several mechanisms are proposed to explain the accelerated loss of polar sea ice, which remains an open question. In the present study, the detailed physical mechanism of sea ice reduction in winter is identified using the daily ERA interim reanalysis data. Downward longwave radiation is an essential element for sea ice reduction, but can only be sustained by excessive upward heat flux from the sea surface exposed to air in the region of sea ice loss. The increased turbulent heat flux is used to increase air temperature and specific humidity in the lower troposphere, which in turn increases downward longwave radiation. This feedback process is clearly observed in the Barents and Kara Seas in the reanalysis data. A quantitative assessment reveals that this feedback process is amplifying at the rate of ~8.9 % every year during 1979-2016. Based on this estimate, sea ice will completely disappear in the Barents and Kara Seas by around 2025. Availability of excessive heat flux is necessary for the maintenance of this feedback process; a similar mechanism of sea ice loss is expected to take place over the sea-ice covered polar region when sea ice is not fully recovered in winter."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #135 on: September 14, 2017, 04:17:48 PM »
The linked reference's findings that methane emissions from boreal wetlands and that the area of tropical wetlands is decreasing is not comforting:

Benjamin Poulter, Philippe Bousquet, Josep G Canadell, Philippe Ciais & Anna Peregon (2017), "Global wetland contribution to 2000–2012 atmospheric methane growth rate dynamics", Environmental Research Letters, Volume 12, Number 9, DOI: https://doi.org/10.1088/1748-9326/aa8391

http://iopscience.iop.org/article/10.1088/1748-9326/aa8391/meta;jsessionid=3D6FF28E9F0A87ED717E47D4AB7BA992.ip-10-40-2-120

Abstract: "Increasing atmospheric methane (CH4) concentrations have contributed to approximately 20% of anthropogenic climate change. Despite the importance of CH4 as a greenhouse gas, its atmospheric growth rate and dynamics over the past two decades, which include a stabilization period (1999–2006), followed by renewed growth starting in 2007, remain poorly understood. We provide an updated estimate of CH4 emissions from wetlands, the largest natural global CH4 source, for 2000–2012 using an ensemble of biogeochemical models constrained with remote sensing surface inundation and inventory-based wetland area data. Between 2000–2012, boreal wetland CH4 emissions increased by 1.2 Tg yr−1 (−0.2–3.5 Tg yr−1), tropical emissions decreased by 0.9 Tg yr−1 (−3.2−1.1 Tg yr−1), yet globally, emissions remained unchanged at 184 ± 22 Tg yr−1. Changing air temperature was responsible for increasing high-latitude emissions whereas declines in low-latitude wetland area decreased tropical emissions; both dynamics are consistent with features of predicted centennial-scale climate change impacts on wetland CH4 emissions. Despite uncertainties in wetland area mapping, our study shows that global wetland CH4 emissions have not contributed significantly to the period of renewed atmospheric CH4 growth, and is consistent with findings from studies that indicate some combination of increasing fossil fuel and agriculture-related CH4 emissions, and a decrease in the atmospheric oxidative sink."
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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on ACME
« Reply #136 on: September 14, 2017, 11:26:10 PM »
The linked reference helps to calibrate paleo-proxies hosted in alluvial strata:

Brady Z. Foreman and Kyle M. Straub (13 Sep 2017), "Autogenic geomorphic processes determine the resolution and fidelity of terrestrial paleoclimate records", Science Advances, Vol. 3, no. 9, e1700683, DOI: 10.1126/sciadv.1700683

http://advances.sciencemag.org/content/3/9/e1700683

Abstract: "Terrestrial paleoclimate records rely on proxies hosted in alluvial strata whose beds are deposited by unsteady and nonlinear geomorphic processes. It is broadly assumed that this renders the resultant time series of terrestrial paleoclimatic variability noisy and incomplete. We evaluate this assumption using a model of oscillating climate and the precise topographic evolution of an experimental alluvial system. We find that geomorphic stochasticity can create aliasing in the time series and spurious climate signals, but these issues are eliminated when the period of climate oscillation is longer than a key time scale of internal dynamics in the geomorphic system. This emergent autogenic geomorphic behavior imparts regularity to deposition and represents a natural discretization interval of the continuous climate signal. We propose that this time scale in nature could be in excess of 104 years but would still allow assessments of the rates of climate change at resolutions finer than the existing age model techniques in isolation."
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