scholarly journals The Earth's climate lagged, recurrent and non-linear solar and lunar multi-millennial scale responses: An oceanic hypothesis, evidence, verifications and forecasts

2021 ◽  
Author(s):  
Jorge Sánchez-Sesma
Keyword(s):  
Climate Models ◽  
Conveyor Belt ◽  
Global Temperature ◽  
Temperature Record ◽  
Climate Modelling ◽  
Multi Scale ◽  
Non Linear ◽  
Global Impacts ◽  
Earth’S Climate ◽  
Millennial Scale

Abstract. This work provides a hypothesis of the links between the multi-millennia scale recurrent solar and tidal influences and Earth's climate lagged responses, associated with the oceanic transport mechanisms with a variable modulation. As a part of this hypothesis, empirical and simple, non-linear lagged models are proposed for five of the most representative Earth's climate variables (a continental tropical temperature, an Antarctic temperature [at James Ross Island], the Greenland temperature, the global temperature and the southeast asian monsoon) with multi-millennia records to account for the lagged responses to solar forcing. The proposed models implicitely include a well-known oceanic heat transport mechanism: the Ocean Conveyor Belt. This oceanic mechanism appears to generate a climate modulation through the intensity of the ocean/atmosphere circulation, and a heat and mass transport, with a consequent climate lag of several thousands of years. Tidal forcing is also considered for global temperature modelling and forecast. The consequent millennia-scale global forecasts, after being integrated/verified with an accumulated ocean travelled distance from the tropical East Pacific, and with a double evaluation of the tidal influences based on similarities and on the NASA’s solar system astronomical dynamics, indicates a cooling for the next century, and gentle oscillations over the next millennia. Our preliminary results that strongly suggest that millennial scale changes in solar activity induce circulation and thermal global impacts, also suggest that the Younger Dryas event, may be influenced by the lagged outcomes of solar driven changes in the tropical Pacific, and by tidal influences. The detected Earth's climate delayed responses, that have been working in the past and present climates, and will be working in the future climates, must be, as soon as possible, independently verified and theoretically sustained, before to be fully included in a multi-scale climate models as a scientific theory. A final example for the global temperature record over the last 170 years demonstrates with experimental results for the twenty first century evolution the convenience of a multi-scale climate modelling with contrasting lower values compared with the IPCC global temperature scenarios.

scholarly journals Snowfall-albedo feedbacks could have led to deglaciation of snowball Earth starting from mid-latitudes

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Philipp de Vrese ◽  
Tobias Stacke ◽  
Jeremy Caves Rugenstein ◽  
Jason Goodman ◽  
Victor Brovkin
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Carbon Dioxide ◽  
Climate Models ◽  
Hydrological Cycle ◽  
High Surface ◽  
Dust Deposition ◽  
Carbon Dioxide Concentrations ◽  
Maximum Temperatures ◽  
Carbon Dioxide Levels ◽  
Earth’S Climate

AbstractSimple and complex climate models suggest a hard snowball – a completely ice-covered planet – is one of the steady-states of Earth’s climate. However, a seemingly insurmountable challenge to the hard-snowball hypothesis lies in the difficulty in explaining how the planet could have exited the glaciated state within a realistic range of atmospheric carbon dioxide concentrations. Here, we use simulations with the Earth system model MPI-ESM to demonstrate that terminal deglaciation could have been triggered by high dust deposition fluxes. In these simulations, deglaciation is not initiated in the tropics, where a strong hydrological cycle constantly regenerates fresh snow at the surface, which limits the dust accumulation and snow aging, resulting in a high surface albedo. Instead, comparatively low precipitation rates in the mid-latitudes in combination with high maximum temperatures facilitate lower albedos and snow dynamics that – for extreme dust fluxes – trigger deglaciation even at present-day carbon dioxide levels.

scholarly journals Significant recent warming over the northern Tibetan Plateau from ice core <i>δ</i><sup>18</sup>O records

2016 ◽  
Vol 12 (2) ◽  
pp. 201-211 ◽  
Author(s):  
W. An ◽  
S. Hou ◽  
W. Zhang ◽  
Y. Wang ◽  
Y. Liu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Ice Core ◽  
Ice Cores ◽  
Global Temperature ◽  
Temperature History ◽  
Temperature Record ◽  
Northern Tibetan Plateau ◽  
Recent Warming ◽  
Warming Hiatus ◽  
Instrumental Records

Abstract. Stable oxygen isotopic records in ice cores provide valuable information about past temperature, especially for regions with scarce instrumental measurements. This paper presents the δ18O result of an ice core drilled to bedrock from Mt. Zangser Kangri (ZK), a remote area on the northern Tibetan Plateau (TP). We reconstructed the temperature series for 1951–2008 from the δ18O records. In addition, we combined the ZK δ18O records with those from three other ice cores in the northern TP (Muztagata, Puruogangri, and Geladaindong) to reconstruct a regional temperature history for the period 1951–2002 (RTNTP). The RTNTP showed significant warming at 0.51 ± 0.07 °C (10 yr)−1 since 1970, a higher rate than the trend of instrumental records of the northern TP (0.43 ± 0.08 °C (10 yr)−1) and the global temperature trend (0.27 ± 0.03°C (10 yr)−1) at the same time. In addition, the ZK temperature record, with extra length until 2008, seems to suggest that the rapid elevation-dependent warming continued for this region during the last decade, when the mean global temperature showed very little change. This could provide insights into the behavior of the recent warming hiatus at higher elevations, where instrumental climate records are lacking.

scholarly journals Size distribution and coating thickness of black carbon from the Canadian oil sands operations

2017 ◽  
Author(s):  
Yuan Cheng ◽  
Shao-Meng Li ◽  
Mark Gordon ◽  
Peter Liu
Keyword(s):  
Size Distribution ◽  
Black Carbon ◽  
Coating Thickness ◽  
Oil Sands ◽  
Radiative Forcing ◽  
Climate Models ◽  
Source Area ◽  
Size Distributions ◽  
Mixing State ◽  
Earth’S Climate

Abstract. Black carbon (BC) plays an important role in the Earth’s climate system. However, parameterization of BC size and mixing state have not been well addressed in aerosol-climate models, introducing substantial uncertainties into the estimation of radiative forcing by BC. In this study, we focused on BC emissions from the massive oil sands (OS) industry in northern Alberta, based on an aircraft campaign conducted over the Athabasca OS region in 2013. A total of 14 flights were made over the OS source area, in which the aircraft was typically flown in a 4- or 5-sided polygon pattern along flight tracks encircling an OS facility. Another 3 flights were performed downwind of the OS source area, each of which involved at least three intercepting locations where the well-mixed OS plume was measured along flight tracks perpendicular to the wind direction. Comparable size distributions were observed for refractory black carbon (rBC) over and downwind of the OS facilities, with rBC mass median diameters (MMD) between ~ 135 and 145 nm that were characteristic of fresh urban emissions. This MMD range corresponded to rBC number median diameters (NMD) of ~ 60–70 nm, approximately 100 % higher than the NMD settings in some aerosol-climate models. The typical in- and out-of-plume segments of a flight, which had different rBC concentrations and photochemical ages, showed consistent rBC size distributions. Moreover, rBC size distributions remained unchanged at different downwind distances from the source area, suggesting that atmospheric aging would not necessarily change rBC size distribution. However, aging indeed influenced rBC mixing state. Coating thickness for rBC cores in the diameter range of 130–160 nm was nearly doubled within three hours when the OS plume was transported over a distance of 90 km from the source area.

scholarly journals rpe v5: An emulator for reduced floating-point precision in large numerical simulations

2016 ◽  
Author(s):  
Andrew Dawson ◽  
Peter Düben
Keyword(s):  
Numerical Simulations ◽  
Climate Models ◽  
Numerical Models ◽  
Computational Cost ◽  
Floating Point ◽  
Climate Modelling ◽  
Acceptable Quality ◽  
Weather And Climate ◽  
Code Changes ◽  
Numerical Precision

Abstract. This paper describes the rpe library which has the capability to emulate the use of arbitrary reduced floating-point precision within large numerical models written in Fortran. The rpe software allows model developers to test how reduced floating-point precision affects the result of their simulations without having to make extensive code changes or port the model onto specialised hardware. The software can be used to identify parts of a program that are problematic for numerical precision and to guide changes to the program to allow a stronger reduction in precision. The development of rpe was motivated by the strong demand for more computing power. If numerical precision can be reduced for an application under consideration while still achieving results of acceptable quality, computational cost can be reduced, since a reduction in numerical precision may allow an increase in performance or a reduction in power consumption. For simulations with weather and climate models, savings due to a reduction in precision could be reinvested to allow model simulations at higher spatial resolution or complexity, or to increase the number of ensemble members to improve predictions. rpe was developed with particular focus on the community of weather and climate modelling, but the software could be used with numerical simulations from other domains.

scholarly journals The sensitivity of atmospheric blocking to changes in upstream latent heating – numerical experiments

2020 ◽  
Author(s):  
Daniel Steinfeld ◽  
Maxi Boettcher ◽  
Richard Forbes ◽  
Stephan Pfahl
Keyword(s):  
Causal Relationship ◽  
Climate Models ◽  
Weather Prediction ◽  
Conveyor Belt ◽  
Cloud Formation ◽  
Latent Heating ◽  
Atmospheric Blocking ◽  
Tropospheric Circulation ◽  
Upper Level ◽  
Microphysical Processes

Abstract. Recent climatological studies based on trajectory calculations have pointed to an important role of latent heating during cloud formation for the dynamics of anticyclonic circulation anomalies such as atmospheric blocking. However, the causal relationship between latent heating and blocking formation has not yet been fully elucidated. To explicitly study this causal relationship, we perform sensitivity simulations of five selected blocking events with a global weather prediction model in which we artificially eliminate latent heating in clouds upstream of the blocking anticyclones. This elimination has substantial effects on the upper-tropospheric circulation in all case studies, but there is also significant case-to-case variability: some blocking systems do not develop at all without upstream latent heating, while for others the amplitude of the blocking anticyclones is merely reduced. This strong influence of latent heating on the jet stream is due to the injection of air masses with low potential vorticity (PV) into the upper troposphere in strongly ascending warm conveyor belt airstreams, and the interaction of the associated divergent outflow with the upper-level PV structure. The important influence of diabatic heating demonstrated with these experiments suggests that an accurate parameterization of microphysical processes in weather prediction and climate models is crucial for adequately representing blocking dynamics.

scholarly journals CRI-HOM: A novel chemical mechanism for simulating Highly Oxygenated Organic Molecules (HOMs) in global chemistry-aerosol-climate models

2020 ◽  
Author(s):  
James Weber ◽  
Alexander Archibald ◽  
Paul Griffiths ◽  
Scott Archer-Nicholls ◽  
Torsten Berndt ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Radiative Forcing ◽  
Organic Molecules ◽  
Climate Models ◽  
Global Climate Models ◽  
Chemical Mechanism ◽  
Atmospheric Composition ◽  
Climate Modelling ◽  
Particle Nucleation ◽  
Peroxy Radicals

Abstract. We present here results from a new mechanism, CRI-HOM, which we have developed to simulate the formation of highly oxygenated organic molecules (HOMs) from the gas phase oxidation of α-pinene, one of the most widely emitted BVOCs by mass. This concise scheme adds 12 species and 66 reactions to the Common Representative Intermediates (CRI) mechanism v2.2 Reduction 5 and enables the representation of semi-explicit HOM treatment suitable for long term global chemistry- aerosol-climate modelling, within a comprehensive tropospheric chemical mechanism. The key features of the new mechanism are (i) representation of the autoxidation of peroxy radicals from the hydroxyl radical and ozone initiated reactions of α-pinene, (ii) formation of multiple generations of peroxy radicals, (iii) formation of accretion products (dimers) and (iv) isoprene-driven suppression of accretion product formation, as observed in experiments. The mechanism has been constructed through optimisation against a series of flow tube laboratory experiments. The mechanism predicts a HOM yield of 4–6 % under conditions of low to moderate NOx, in line with experimental observations, and reproduces qualitatively the decline in HOM yield and concentration at higher NOx. The mechanism gives a HOM yield that also increases with temperature, in line with observations, and our mechanism compares favourably to some of the limited observations of [HOM] observed in the boreal forest in Finland and in the south east USA. The reproduction of isoprene-driven suppression of HOMs is a key step forward as it enables global climate models to capture the interaction between the major BVOC species, along with the potential climatic feedbacks. This suppression is demonstrated when the mechanism is used to simulate atmospheric profiles over the boreal forest and rainforest; different isoprene concentrations result in different [HOM] distributions, illustrating the importance of BVOC interactions in atmospheric composition and climate. Finally particle nucleation rates calculated from [HOM] in present day and pre- industrial atmospheres suggest that sulphuric acid free nucleation can compete effectively with other nucleation pathways in the boreal forest, particularly in the pre-industrial, with important implications for the aerosol budget and radiative forcing.

scholarly journals A high-resolution downscaled CMIP6 projections dataset of essential surface climate variables over the globe coherent with the ERA5-Land reanalysis for climate change impact assessments

2021 ◽  
Author(s):  
Thomas Noël ◽  
Harilaos Loukos ◽  
Dimitri Defrance
Keyword(s):  
Climate Change ◽  
High Resolution ◽  
Climate Models ◽  
Mapping Method ◽  
Cumulative Distribution ◽  
Climate Projections ◽  
Climate Modelling ◽  
Temperature And Precipitation ◽  
Surface Climate ◽  
Emissions Scenarios

A high-resolution climate projections dataset is obtained by statistically downscaling climate projections from the CMIP6 experiment using the ERA5-Land reanalysis from the Copernicus Climate Change Service. This global dataset has a spatial resolution of 0.1°x 0.1°, comprises 5 climate models and includes two surface daily variables at monthly resolution: air temperature and precipitation. Two greenhouse gas emissions scenarios are available: one with mitigation policy (SSP126) and one without mitigation (SSP585). The downscaling method is a Quantile Mapping method (QM) called the Cumulative Distribution Function transform (CDF-t) method that was first used for wind values and is now referenced in dozens of peer-reviewed publications. The data processing includes quality control of metadata according to the climate modelling community standards and value checking for outlier detection.

Global and amplified land warming trends over the past 40+ years are entirely human-driven.

2021 ◽  
Author(s):  
Karsten Haustein
Keyword(s):  
Radiative Forcing ◽  
Volcanic Eruptions ◽  
Internal Variability ◽  
Forced Response ◽  
Global Temperature ◽  
Extreme Weather Events ◽  
Temperature Record ◽  
Model Framework ◽  
Anthropogenic Aerosol ◽  
The Past

&lt;p class=&quot;p1&quot;&gt;The role of external (radiative) forcing factors and internal unforced (ocean) low-frequency variations in the instrumental global temperature record are still hotly debated. More recent findings point towards a larger contribution from changes in external forcing, but the jury is still out. While the estimation of the human-induced total global warming fraction since pre-industrial times is fairly robust and mostly independent of multidecadal internal variability, this is not necessarily the case for key regional features such as Arctic amplification or enhanced warming over continental land areas. Accounting for the slow global temperature adjustment after strong volcanic eruptions, the spatially heterogeneous nature of anthropogenic aerosol forcing and known biases in the sea surface temperature record, almost all of the multidecadal fluctuations observed over at least the last 160+ years can be explained without a relevant role for internal variability. Using a two-box response model framework, I will demonstrate that not only multidecadal variability is very likely a forced response, but warming trends over the past 40+ years are entirely attributable to human factors. Repercussions for amplifed European (or D-A-CH for that matter) warming and associated implications for extreme weather events are discussed. Further consideration is given to the communications aspect of such critical results as well as the question of wider societal impacts.&lt;/p&gt;

A regime perspective on jet and blocking dynamics in CMIP6

2021 ◽  
Author(s):  
Joshua Dorrington
Keyword(s):  
Potential Vorticity ◽  
Climate Models ◽  
Rossby Waves ◽  
Climate Model ◽  
Atmospheric Dynamics ◽  
Interdecadal Variability ◽  
Model Ensemble ◽  
Atlantic Region ◽  
Non Linear ◽  
Jet Structure

&lt;p&gt;Weather over the Euro-Atlantic region during winter is highly variable, with rich and chaotic internal atmospheric dynamics. In particular, the non-linear breaking of Rossby waves irreversibly mixes potential vorticity contours and so triggers shifts in the latitude of the eddy driven jet and establishes persistent anticyclonic blocking events. The concept of atmospheric regimes captures the tendency for blocks &amp;#8211; and for the jet &amp;#8211; to persist in a small number of preferred locations. Regimes then provide a non-linear basis through which model deficiencies, interdecadal variability and forced trends in the Euro-Atlantic circulation can be studied.&lt;/p&gt;&lt;p&gt;A drawback of past regime approaches is that they were unable to easily capture both the dynamics of the jet and of blocking anticyclones simultaneously. In this work we apply a recently developed regime framework, which is able to capture both these important aspects while reducing sampling variability, to the CMIP6 climate model ensemble. We analyse both the historical variability and biases of blocking and jet structure in this latest generation of climate models, and make new estimates of the anthropogenic forced trend over the coming century.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Multi-Scale Insights on the Threshold Pressure Gradient in Low-Permeability Porous Media

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 364 ◽  
Author(s):  
Huimin Wang ◽  
Jianguo Wang ◽  
Xiaolin Wang ◽  
Andrew Chan
Keyword(s):  
Porous Media ◽  
Pressure Gradient ◽  
Water Saturation ◽  
Flow Behavior ◽  
Low Permeability ◽  
Threshold Pressure ◽  
Threshold Pressure Gradient ◽  
Linear Flow ◽  
Multi Scale ◽  
Non Linear

Low-permeability porous medium usually has asymmetric distributions of pore sizes and pore-throat tortuosity, thus has a non-linear flow behavior with an initial pressure gradient observed in experiments. A threshold pressure gradient (TPG) has been proposed as a crucial parameter to describe this non-linear flow behavior. However, the determination of this TPG is still unclear. This study provides multi-scale insights on the TPG in low-permeability porous media. First, a semi-empirical formula of TPG was proposed based on a macroscopic relationship with permeability, water saturation, and pore pressure, and verified by three sets of experimental data. Second, a fractal model of capillary tubes was developed to link this TPG formula with structural parameters of porous media (pore-size distribution fractal dimension and tortuosity fractal dimension), residual water saturation, and capillary pressure. The effect of pore structure complexity on the TPG is explicitly derived. It is found that the effects of water saturation and pore pressure on the TPG follow an exponential function and the TPG is a linear function of yield stress. These effects are also spatially asymmetric. Complex pore structures significantly affect the TPG only in the range of low porosity, but water saturation and yield stress have effects on a wider range of porosity. These results are meaningful to the understanding of non-linear flow mechanism in low-permeability reservoirs.

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