scholarly journals Development and testing of scenarios for implementing Holocene LULC in Earth System Model Experiments

2019 ◽  
Author(s):  
Sandy P. Harrison ◽  
Marie-José Gaillard ◽  
Benjamin D. Stocker ◽  
Marc Vander Linden ◽  
Kees Klein Goldewijk ◽  
...  
Keyword(s):  
Land Cover ◽  
Anthropogenic Impacts ◽  
Global Climate ◽  
Ice Core ◽  
System Model ◽  
Global Changes ◽  
Archaeological Data ◽  
The Past ◽  
Climate Simulations ◽  
Intercomparison Project

Abstract. Anthropogenic changes in land use and land cover (LULC) during the pre-industrial Holocene could have affected regional and global climate. Current LULC scenarios are based on relatively simple assumptions and highly uncertain estimates of population changes through time. Archaeological and palaeoenvironmental reconstructions have the potential to refine these assumptions and estimates. The Past Global Changes (PAGES) LandCover6k initiative is working towards improved reconstructions of LULC globally. In this paper, we document the types of archaeological data that are being collated and how they will be used to improve LULC reconstructions. Given the large methodological uncertainties involved, we propose methods to evaluate the revised scenarios by using independent pollen-based reconstructions of land cover and of climate. A further test involves carbon-cycle simulations to determine whether the LULC reconstructions are consistent with constraints provided by ice-core records of CO2 evolution and modern-day LULC. Finally, we outline a protocol for using the improved LULC reconstructions in palaeoclimate simulations within the framework of the Palaeoclimate Modelling Intercomparison Project in order to quantify the magnitude of anthropogenic impacts on climate through time and ultimately to improve the realism of Holocene climate simulations.

scholarly journals Development and testing scenarios for implementing land use and land cover changes during the Holocene in Earth system model experiments

2020 ◽  
Vol 13 (2) ◽  
pp. 805-824 ◽  
Author(s):  
Sandy P. Harrison ◽  
Marie-José Gaillard ◽  
Benjamin D. Stocker ◽  
Marc Vander Linden ◽  
Kees Klein Goldewijk ◽  
...  
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Anthropogenic Impacts ◽  
Global Climate ◽  
Ice Core ◽  
Global Changes ◽  
Carbon Cycle Model ◽  
The Holocene ◽  
Archaeological Data ◽  
Intercomparison Project

Abstract. Anthropogenic changes in land use and land cover (LULC) during the pre-industrial Holocene could have affected regional and global climate. Existing scenarios of LULC changes during the Holocene are based on relatively simple assumptions and highly uncertain estimates of population changes through time. Archaeological and palaeoenvironmental reconstructions have the potential to refine these assumptions and estimates. The Past Global Changes (PAGES) LandCover6k initiative is working towards improved reconstructions of LULC globally. In this paper, we document the types of archaeological data that are being collated and how they will be used to improve LULC reconstructions. Given the large methodological uncertainties involved, both in reconstructing LULC from the archaeological data and in implementing these reconstructions into global scenarios of LULC, we propose a protocol to evaluate the revised scenarios using independent pollen-based reconstructions of land cover and climate. Further evaluation of the revised scenarios involves carbon cycle model simulations to determine whether the LULC reconstructions are consistent with constraints provided by ice core records of CO2 evolution and modern-day LULC. Finally, the protocol outlines how the improved LULC reconstructions will be used in palaeoclimate simulations in the Palaeoclimate Modelling Intercomparison Project to quantify the magnitude of anthropogenic impacts on climate through time and ultimately to improve the realism of Holocene climate simulations.

scholarly journals Introduction to the special issue “Climate of the past 2000 years: regional and trans-regional syntheses”

2019 ◽  
Vol 15 (2) ◽  
pp. 611-615
Author(s):  
Chris S. M. Turney ◽  
Helen V. McGregor ◽  
Pierre Francus ◽  
Nerilie Abram ◽  
Michael N. Evans ◽  
...  
Keyword(s):  
Regional Differences ◽  
Global Climate ◽  
Rate Of Change ◽  
Global Changes ◽  
Special Issue ◽  
The Past ◽  
Global View ◽  
Past 2000 Years ◽  
Recent Climate ◽  
Observational Record

Abstract. This PAGES (Past Global Changes) 2k (climate of the past 2000 years working group) special issue of Climate of the Past brings together the latest understanding of regional change and impacts from PAGES 2k groups across a range of proxies and regions. The special issue has emerged from a need to determine the magnitude and rate of change of regional and global climate beyond the timescales accessible within the observational record. This knowledge also plays an important role in attribution studies and is fundamental to understanding the mechanisms and environmental and societal impacts of recent climate change. The scientific studies in the special issue reflect the urgent need to better understand regional differences from a truly global view around the PAGES themes of “Climate Variability, Modes and Mechanisms”, “Methods and Uncertainties”, and “Proxy and Model Understanding”.

Evolution of the monsoon system over the past 250 million years

2021 ◽  
Author(s):  
Yongyun Hu ◽  
Jiaqi Guo ◽  
Xiang Li ◽  
Jiaenjing Lan ◽  
Qifan Lin ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Land Surface ◽  
System Model ◽  
Earth System ◽  
Global Monsoon ◽  
The Past ◽  
Climate Simulations ◽  
Monsoon System ◽  
Community Earth System Model ◽  
Carbon Dioxide Co2

<p>The evolution of continents over the past 250 million year is remarked by the breakup of the Pangea supercontinent. The changes of continents must have important influences on regional and global monsoon systems because monsoons are primarily a result of land-sea thermal contrast.</p><p>To study how the monsoon system had been evolved with continent changes over the past 250 million years, we carried out a series of climate simulations, using the Community Earth System Model (CESM). Changes in continents, mountain building, solar radiation, and carbon dioxide (CO2) are all considered in the simulations. In the present talk, we will present our preliminary simulation results of how the mega-monsoon associated with the supercontinent Pangea evolved into the six regional monsoons at the present over the past 250 million years. We will also demonstrate ocean circulation changes with different continent distributions, such as ENSO, and its influences on regional monsoons. Monsoon impacts on land-surface processes and the associated carbon-cycle will be also presented.</p>

scholarly journals Transboundary Basins Need More Attention: Anthropogenic Impacts on Land Cover Changes in Aras River Basin, Monitoring and Prediction

2020 ◽  
Vol 12 (20) ◽  
pp. 3329
Author(s):  
Sajad Khoshnoodmotlagh ◽  
Jochem Verrelst ◽  
Alireza Daneshi ◽  
Mohsen Mirzaei ◽  
Hossein Azadi ◽  
...  
Keyword(s):  
Land Cover ◽  
River Basin ◽  
Urban Areas ◽  
Anthropogenic Impacts ◽  
Anthropogenic Activities ◽  
Kappa Index ◽  
The Caspian Sea ◽  
The Past ◽  
Agricultural Areas ◽  
Aras River

Changes in land cover (LC) can alter the basin hydrology by affecting the evaporation, infiltration, and surface and subsurface flow processes, and ultimately affect river water quantity and quality. This study aimed to monitor and predict the LC composition of a major, transboundary basin contributing to the Caspian Sea, the Aras River Basin (ARB). To this end, four LC maps of ARB corresponding to the years 1984, 2000, 2010, and 2017 were generated using Landsat satellite imagery from Armenia and the Nakhchivan Autonomous Republic. The LC gains and losses, net changes, exchanges, and the spatial trend of changes over 33 years (1984–2017) were investigated. The most important drivers of these changes and the most accurate LC transformation scenarios were identified, and a land change modeler (LCM) was applied to predict the LC change for the years 2027 and 2037. Validation results showed that LCM, with a Kappa index higher than 81%, is appropriate for predicting LC changes in the study area. The LC changes observed in the past indicate significant anthropogenic impacts on the basin, mainly by constructing new reservoir dams and expanding agriculture and urban areas, which are the major water-consuming sectors. Results show that over the past 33 years, agricultural areas have grown by more than 57% from 1984 to 2017 in the study area. Results also indicate that the given similar anthropogenic activities will keep on continuing in the ARB, and agricultural areas will increase by 2% from 2017 to 2027, and by another 1% from 2027 to 2037. Results of this study can support transboundary decision-making processes to analyze potential adverse impacts following past policies with neighboring countries that share the same water resources.

scholarly journals Nitrogen Garners Starring Role in Refined Earth System Model

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Shannon Kelleher
Keyword(s):  
Nitrogen Uptake ◽  
Global Climate ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Plant Nitrogen ◽  
Climate Simulations ◽  
Plant Nitrogen Uptake ◽  
Realistic Representation

Scientists create a more realistic representation of plant nitrogen uptake and usage to improve global climate simulations.

scholarly journals Regional and global climate for the mid-Pliocene using CCSM4 and PlioMIP2 boundary conditions

2017 ◽  
Author(s):  
Deepak Chandan ◽  
W. Richard Peltier
Keyword(s):  
Boundary Conditions ◽  
Climate Models ◽  
Global Climate ◽  
Phase 1 ◽  
System Model ◽  
High Latitudes ◽  
Climate System Model ◽  
Intercomparison Project ◽  
Proxy Reconstructions ◽  
Selection Of

Abstract. The Pliocene Model Intercomparison Project, Phase 2 (PlioMIP2) is an international collaboration to simulate the climate of the mid-Pliocene interglacial, marine isotope stage KM5c (3.205 Mya), using a wide selection of climate models with the objective of understanding the nature of the warming that is known to have occurred during the broader mid-Pliocene warm period. PlioMIP2 builds upon the successes of PlioMIP by shifting focus onto a specific interglacial and by using a revised set of geographic and orbital boundary conditions. In this paper, we present the details of the mid-Pliocene simulations that we have performed with the Community Climate System Model version 4 (CCSM4), and the enhanced variant of the PlioMIP2 boundary conditions, and discuss the simulated climatology through comparisons to our control simulations, and to proxy reconstructions of the climate of the mid-Pliocene. With the new boundary conditions, the CCSM4 model simulates a mid-Pliocene which is more than twice as warm as that with the boundary conditions used for PlioMIP Phase 1. The warming is more enhanced near the high-latitudes which is where most of the changes to the boundary conditions have been made. The elevated warming in the high-latitudes leads to a better match of the simulated climatology to proxy based reconstructions than what was possible with the previous version of the boundary conditions.

scholarly journals The Tropical Pacific ENSO–Mean State Relationship in Climate Models over the Last Millennium

2020 ◽  
Vol 33 (17) ◽  
pp. 7539-7551
Author(s):  
D. Allie Wyman ◽  
Jessica. L. Conroy ◽  
Christina Karamperidou
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
Global Climate ◽  
General Circulation Models ◽  
Tropical Pacific ◽  
Last Millennium ◽  
Climate Simulations ◽  
Intercomparison Project ◽  
The Relationship ◽  
The Tropical Pacific

AbstractENSO and the mean zonal sea surface temperature gradient (dSST) of the tropical Pacific are important drivers of global climate and vary on decadal to centennial time scales. However, the relationship between dSST and ENSO cannot be assessed with the short instrumental record, and is uncertain in proxy data, with intervals of both stronger and weaker ENSO postulated to occur with overall strong dSST in the past. Here we assess the ENSO–dSST relationship during the last millennium using general circulation models (GCMs) participating in phase 3 of the Paleoclimate Modeling Intercomparison Project. Last millennium GCM simulations show diversity in the strength and direction of the ENSO–dSST relationship. Yet, the models that best simulate modern tropical Pacific climate frequently have a more negative ENSO–dSST correlation. Thus, last millennium tropical Pacific climate simulations support the likelihood of enhanced ENSO during decadal to centennial periods of reduced tropical Pacific dSST. However, the alternating directional ENSO–dSST relationship in all model simulations suggests that this relationship is not constant through time and is likely controlled by multiple mechanisms.

scholarly journals Is deoxygenation detectable before warming in the thermocline?

2020 ◽  
Vol 17 (7) ◽  
pp. 1877-1895
Author(s):  
Angélique Hameau ◽  
Thomas L. Frölicher ◽  
Juliette Mignot ◽  
Fortunat Joos
Keyword(s):  
Anthropogenic Impacts ◽  
Coupled Model ◽  
Internal Variability ◽  
Oxygen Depletion ◽  
System Model ◽  
Model Assessment ◽  
Anthropogenic Change ◽  
Adverse Impacts ◽  
Delayed Emergence ◽  
Intercomparison Project

Abstract. Anthropogenic greenhouse gas emissions cause ocean warming and oxygen depletion, with adverse impacts on marine organisms and ecosystems. Warming is one of the main indicators of anthropogenic climate change, but, in the thermocline, changes in oxygen and other biogeochemical tracers may emerge from the bounds of natural variability prior to warming. Here, we assess the time of emergence (ToE) of anthropogenic change in thermocline temperature and thermocline oxygen within an ensemble of Earth system model simulations from the fifth phase of the Coupled Model Intercomparison Project. Changes in temperature typically emerge from internal variability prior to changes in oxygen. However, in about a third (35±11 %) of the global thermocline deoxygenation emerges prior to warming. In these regions, both reduced ventilation and reduced solubility add to the oxygen decline. In addition, reduced ventilation slows the propagation of anthropogenic warming from the surface into the ocean interior, further contributing to the delayed emergence of warming compared to deoxygenation. Magnitudes of internal variability and of anthropogenic change, which determine ToE, vary considerably among models leading to model–model differences in ToE. We introduce a new metric, relative ToE, to facilitate the multi-model assessment of ToE. This reduces the inter-model spread compared to the traditionally evaluated absolute ToE. Our results underline the importance of an ocean biogeochemical observing system and that the detection of anthropogenic impacts becomes more likely when using multi-tracer observations.

Summary

2007 ◽  
Author(s):  
Robert May
Keyword(s):  
Fossil Fuels ◽  
Industrial Revolution ◽  
Global Climate ◽  
Ice Core ◽  
Sea Levels ◽  
The Past ◽  
Energy Demands ◽  
Co2 Levels ◽  
The Usa ◽  
History Of

Energy . . . Beyond Oil is important and timely and should be understood within the wider context of global climate change and future energy demands. In the 1780s John Watts developed his steam engine and so began the Industrial Revolution. At this time, ice-core records show that levels of CO2 in the atmosphere were around 288 parts per million (ppm). Give or take 10 ppm, this had been their level for the past 6,000 years, since the dawn of the first cities. As industrialization drove up the burning of fossil fuels in the developed world, CO2 levels rose. At first the rise was slow. It took about a century and a half to reach 315 ppm. The rise accelerated during the twentieth century: 330 ppm by the mid-1970s; 360 ppm by the 1990s; 380 ppm today. This change of 20 ppm over the past decade is equal to that last seen when the most recent ice age ended, ushering in the dawn of the Holocene epoch, 10,000 years ago. If current trends continue, then by about 2050 atmospheric CO2 levels will have reachedaround500 ppm, nearly double pre-industrial levels. The last time our planet experienced such high levels was some 50 million years ago, during the Eocene epoch, when sea levels were around100 m higher than today. The Dutch Nobelist, Paul Crutzen, has, indeed, suggested that we should recognize that we are now living in a new geological epoch, the Anthropocene. He sees this epoch as beginning around 1780, when industrialization began to change the geochemical history of our planet. Even today, there continues to exist a ‘denial lobby’, funded to the tune of tens of millions of dollars by sectors of the petrochemical industry, and highly influential in some countries. This lobby has understandable similarities, in tactics and attitudes, to the tobacco lobby that continues to deny smoking causes lung cancer, or the curious lobby denying that HIV causes AIDS. This denial lobby is currently very influential in the USA.

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