scholarly journals Carbon-nitrogen feedbacks in the UVic ESCM

2012 ◽  
Vol 5 (5) ◽  
pp. 1137-1160 ◽  
Author(s):  
R. Wania ◽  
K. J. Meissner ◽  
M. Eby ◽  
V. K. Arora ◽  
I. Ross ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Gross Primary Production ◽  
N Deposition ◽  
Strong Nonlinearity ◽  
Earth System ◽  
Soil System ◽  
Biological N2 Fixation ◽  
Plant Soil ◽  
Nitrogen Pools

Abstract. A representation of the terrestrial nitrogen cycle is introduced into the UVic Earth System Climate Model (UVic ESCM). The UVic ESCM now contains five terrestrial carbon pools and seven terrestrial nitrogen pools: soil, litter, leaves, stem and roots for both elements and ammonium and nitrate in the soil for nitrogen. Nitrogen cycles through plant tissue, litter, soil and the mineral pools before being taken up again by the plant. Biological N2 fixation and nitrogen deposition represent external inputs to the plant-soil system while losses occur via leaching. Simulated carbon and nitrogen pools and fluxes are in the range of other models and observations. Gross primary production (GPP) for the 1990s in the CN-coupled version is 129.6 Pg C a−1 and net C uptake is 0.83 Pg C a−1, whereas the C-only version results in a GPP of 133.1 Pg C a−1 and a net C uptake of 1.57 Pg C a−1. At the end of a transient experiment for the years 1800–1999, where radiative forcing is held constant but CO2 fertilisation for vegetation is permitted to occur, the CN-coupled version shows an enhanced net C uptake of 1.05 Pg C a−1, whereas in the experiment where CO2 is held constant and temperature is transient the land turns into a C source of 0.60 Pg C a−1 by the 1990s. The arithmetic sum of the temperature and CO2 effects is 0.45 Pg C a−1, 0.38 Pg C a−1 lower than seen in the fully forced model, suggesting a strong nonlinearity in the CN-coupled version. Anthropogenic N deposition has a positive effect on Net Ecosystem Production of 0.35 Pg C a−1. Overall, the UVic CN-coupled version shows similar characteristics to other CN-coupled Earth System Models, as measured by net C balance and sensitivity to changes in climate, CO2 and temperature.

scholarly journals Carbon-nitrogen feedbacks in the UVic ESCM

2012 ◽  
Vol 5 (1) ◽  
pp. 67-118
Author(s):  
R. Wania ◽  
K. J. Meissner ◽  
M. Eby ◽  
V. Arora ◽  
I. Ross ◽  
...  
Keyword(s):  
Climate Model ◽  
Gross Primary Production ◽  
N Deposition ◽  
External Input ◽  
Earth System ◽  
Soil System ◽  
Biological N2 Fixation ◽  
Plant Soil ◽  
Nitrogen Pools ◽  
C And N

Abstract. A representation of the terrestrial nitrogen cycle is introduced into the UVic Earth System Climate Model (UVic ESCM). The UVic ESCM now contains five terrestrial carbon pools and seven terrestrial nitrogen pools: soil, litter, leaves, stem and roots for both elements and ammonium and nitrate in the soil for nitrogen. Nitrogen cycles through plant tissue, litter, soil and the mineral pools before being taken up again by the plant. Biological N2 fixation and nitrogen deposition represent the external input and loss from the plant-soil system can occur via leaching. Simulated carbon and nitrogen pools and fluxes are in the range of other models and data. Gross primary production (GPP) for the 1990s in the CN-coupled version is 129.6 Pg C a−1 and net C uptake is 0.83 Pg C a−1, whereas the C-only version results in a GPP of 133.1 Pg C a−1 and a net C uptake of 1.57 Pg C a−1. At the end of a transient experiment for the years 1800–2000, where temperature is held constant but CO2 fertilisation for vegetation is allowed to happen, the CN-coupled version shows an enhanced net C uptake of 1.05 Pg C a−1, whereas in the experiment where CO2 is held constant and temperature is transient the land turns into a C source of 0.60 Pg C a−1 by the 1990s. The arithmetic sum of the temperature and CO2 effects results in 0.45 Pg C a−1, which is 0.38 Pg C a−1 lower than seen in the fully forced model, suggesting a strong non-linearity in the CN-coupled version. Anthropogenic N deposition has a positive effect on Net Ecosystem Production of 0.35 Pg C a−1. Overall, the UVic CN-coupled version shows similar characteristics in terms of C and N pools and fluxes to other CN-coupled Earth System Models.

Sensitivity of an Earth system climate model to idealized radiative forcing

2012 ◽  
Vol 39 (10) ◽  
pp. n/a-n/a ◽  
Author(s):  
Timothy Andrews ◽  
Mark A. Ringer ◽  
Marie Doutriaux-Boucher ◽  
Mark J. Webb ◽  
William J. Collins
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Earth System

Physical Climate Response to a Reduction of Anthropogenic Climate Forcing

2010 ◽  
Vol 14 (7) ◽  
pp. 1-11 ◽  
Author(s):  
Arindam Samanta ◽  
Bruce T. Anderson ◽  
Sangram Ganguly ◽  
Yuri Knyazikhin ◽  
Ramakrishna R. Nemani ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Thermohaline Circulation ◽  
Climate Model ◽  
Global Climate ◽  
Ghg Emissions ◽  
Climate System ◽  
Initial Increase ◽  
Earth System ◽  
Human Welfare ◽  
Co2 Concentrations

Abstract Recent research indicates that the warming of the climate system resulting from increased greenhouse gas (GHG) emissions over the next century will persist for many centuries after the cessation of these emissions, principally because of the persistence of elevated atmospheric carbon dioxide (CO2) concentrations and their attendant radiative forcing. However, it is unknown whether the responses of other components of the climate system—including those related to Greenland and Antarctic ice cover, the Atlantic thermohaline circulation, the West African monsoon, and ecosystem and human welfare—would be reversed even if atmospheric CO2 concentrations were to recover to 1990 levels. Here, using a simple set of experiments employing a current-generation numerical climate model, the authors examine the response of the physical climate system to decreasing CO2 concentrations following an initial increase. Results indicate that many characteristics of the climate system, including global temperatures, precipitation, soil moisture, and sea ice, recover as CO2 concentrations decrease. However, other components of the Earth system may still exhibit nonlinear hysteresis. In these experiments, for instance, increases in stratospheric water vapor, which initially result from increased CO2 concentrations, remain present even as CO2 concentrations recover. These results suggest that identification of additional threshold behaviors in response to human-induced global climate change should focus on subcomponents of the full Earth system, including cryosphere, biosphere, and chemistry.

scholarly journals If Anthropogenic CO2 Emissions Cease, Will Atmospheric CO2 Concentration Continue to Increase?

2013 ◽  
Vol 26 (23) ◽  
pp. 9563-9576 ◽  
Author(s):  
Andrew H. MacDougall ◽  
Michael Eby ◽  
Andrew J. Weaver
Keyword(s):  
Greenhouse Gases ◽  
Radiative Forcing ◽  
Climate Model ◽  
Carbon Sources ◽  
Co2 Concentration ◽  
Earth System ◽  
Terrestrial Source ◽  
The University ◽  
Aerosol Emissions ◽  
Over Time

If anthropogenic CO2 emissions were to suddenly cease, the evolution of the atmospheric CO2 concentration would depend on the magnitude and sign of natural carbon sources and sinks. Experiments using Earth system models indicate that the overall carbon sinks dominate, such that upon the cessation of anthropogenic emissions, atmospheric CO2 levels decrease over time. However, these models have typically neglected the permafrost carbon pool, which has the potential to introduce an additional terrestrial source of carbon to the atmosphere. Here, the authors use the University of Victoria Earth System Climate Model (UVic ESCM), which has recently been expanded to include permafrost carbon stocks and exchanges with the atmosphere. In a scenario of zeroed CO2 and sulfate aerosol emissions, whether the warming induced by specified constant concentrations of non-CO2 greenhouse gases could slow the CO2 decline following zero emissions or even reverse this trend and cause CO2 to increase over time is assessed. It is found that a radiative forcing from non-CO2 gases of approximately 0.6 W m−2 results in a near balance of CO2 emissions from the terrestrial biosphere and uptake of CO2 by the oceans, resulting in near-constant atmospheric CO2 concentrations for at least a century after emissions are eliminated. At higher values of non-CO2 radiative forcing, CO2 concentrations increase over time, regardless of when emissions cease during the twenty-first century. Given that the present-day radiative forcing from non-CO2 greenhouse gases is about 0.95 W m−2, the results suggest that if all CO2 and aerosols emissions were eliminated without also decreasing non-CO2 greenhouse gas emissions CO2 levels would increase over time, resulting in a small increase in climate warming associated with this positive permafrost–carbon feedback.

scholarly journals Sensitivity simulations with direct shortwave radiative forcing by aeolian dust during glacial cycles

2014 ◽  
Vol 10 (4) ◽  
pp. 1333-1348 ◽  
Author(s):  
E. Bauer ◽  
A. Ganopolski
Keyword(s):  
Radiative Forcing ◽  
Absorption Efficiency ◽  
Physical Parameters ◽  
Optical Parameters ◽  
Strong Nonlinearity ◽  
Earth System ◽  
Dust Deposition ◽  
Glacial Cycles ◽  
Detailed Model ◽  
Aeolian Dust

Abstract. Possible feedback effects between aeolian dust, climate and ice sheets are studied for the first time with an Earth system model of intermediate complexity over the late Pleistocene period. Correlations between climate and dust deposition records suggest that aeolian dust potentially plays an important role for the evolution of glacial cycles. Here climatic effects from the dust direct radiative forcing (DRF) caused by absorption and scattering of solar radiation are investigated. Key elements controlling the dust DRF are the atmospheric dust distribution and the absorption-scattering efficiency of dust aerosols. Effective physical parameters in the description of these elements are varied within uncertainty ranges known from available data and detailed model studies. Although the parameters can be reasonably constrained, the simulated dust DRF spans a~wide uncertainty range related to the strong nonlinearity of the Earth system. In our simulations, the dust DRF is highly localized. Medium-range parameters result in negative DRF of several watts per square metre in regions close to major dust sources and negligible values elsewhere. In the case of high absorption efficiency, the local dust DRF can reach positive values and the global mean DRF can be insignificantly small. In the case of low absorption efficiency, the dust DRF can produce a significant global cooling in glacial periods, which leads to a doubling of the maximum glacial ice volume relative to the case with small dust DRF. DRF-induced temperature and precipitation changes can either be attenuated or amplified through a feedback loop involving the dust cycle. The sensitivity experiments suggest that depending on dust optical parameters, dust DRF has the potential to either damp or reinforce glacial–interglacial climate changes.

scholarly journals Incorrect Asian aerosols affecting the attribution and projection of regional climate change in CMIP6 models

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Zhili Wang ◽  
Lei Lin ◽  
Yangyang Xu ◽  
Huizheng Che ◽  
Xiaoye Zhang ◽  
...  
Keyword(s):  
Climate Change ◽  
Radiative Forcing ◽  
Impact Analysis ◽  
Climate Model ◽  
Regional Climate ◽  
Eastern China ◽  
Coupled Model ◽  
Regional Climate Change ◽  
Anthropogenic Aerosol ◽  
Wide Range

AbstractAnthropogenic aerosol (AA) forcing has been shown as a critical driver of climate change over Asia since the mid-20th century. Here we show that almost all Coupled Model Intercomparison Project Phase 6 (CMIP6) models fail to capture the observed dipole pattern of aerosol optical depth (AOD) trends over Asia during 2006–2014, last decade of CMIP6 historical simulation, due to an opposite trend over eastern China compared with observations. The incorrect AOD trend over China is attributed to problematic AA emissions adopted by CMIP6. There are obvious differences in simulated regional aerosol radiative forcing and temperature responses over Asia when using two different emissions inventories (one adopted by CMIP6; the other from Peking university, a more trustworthy inventory) to driving a global aerosol-climate model separately. We further show that some widely adopted CMIP6 pathways (after 2015) also significantly underestimate the more recent decline in AA emissions over China. These flaws may bring about errors to the CMIP6-based regional climate attribution over Asia for the last two decades and projection for the next few decades, previously anticipated to inform a wide range of impact analysis.

scholarly journals Anthropogenic forcing and response yield observed positive trend in Earth’s energy imbalance

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shiv Priyam Raghuraman ◽  
David Paynter ◽  
V. Ramaswamy
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Solar Spectrum ◽  
Internal Variability ◽  
Satellite Observations ◽  
Positive Trend ◽  
Energy Imbalance ◽  
Model Simulations ◽  
Heat Uptake ◽  
Climate Model Simulations

AbstractThe observed trend in Earth’s energy imbalance (TEEI), a measure of the acceleration of heat uptake by the planet, is a fundamental indicator of perturbations to climate. Satellite observations (2001–2020) reveal a significant positive globally-averaged TEEI of 0.38 ± 0.24 Wm−2decade−1, but the contributing drivers have yet to be understood. Using climate model simulations, we show that it is exceptionally unlikely (<1% probability) that this trend can be explained by internal variability. Instead, TEEI is achieved only upon accounting for the increase in anthropogenic radiative forcing and the associated climate response. TEEI is driven by a large decrease in reflected solar radiation and a small increase in emitted infrared radiation. This is because recent changes in forcing and feedbacks are additive in the solar spectrum, while being nearly offset by each other in the infrared. We conclude that the satellite record provides clear evidence of a human-influenced climate system.

scholarly journals Nitrogen Pools in Tropical Plantations of N2-Fixing and Non-N2-Fixing Legume Trees under Different Tree Stand Densities

Nitrogen ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 86-98
Author(s):  
Kelly Nery Bighi ◽  
Ranieri Ribeiro Paula ◽  
Marcos Vinícius Winckler Caldeira ◽  
Diego Lang Burak ◽  
Eduardo de Sá Mendonça ◽  
...  
Keyword(s):  
N2 Fixation ◽  
Stand Density ◽  
N Accumulation ◽  
Biological N2 Fixation ◽  
Nitrogen Acquisition ◽  
Nitrogen Pools ◽  
Acquisition Strategies ◽  
Tropical Plantations ◽  
Schizolobium Parahyba ◽  
Slow Growing

We investigated the nitrogen pools in monocultures of legume species widely used in reforestation in Brazil that have contrasting growth and nitrogen acquisition strategies. The plantations were established with the slow-growing and N2-fixing tree Anadenanthera peregrina var. peregrina, and the fast-growing and non-fixing tree Schizolobium parahyba var. amazonicum. The measurements of N pools in the tree biomass and the soil followed standard methods and were carried out on 54 experimental plots. The N2 fixation pools were evaluated by abundance natural of 15N and the N accretion methods. The soil N content was of similar magnitude between species and stand densities. The species showed similar amounts of N in the biomass, but divergent patterns of N accumulation, as well as the 15N signature on the leaves. S. parahyba accumulated most N in the stem, while A. peregrina accumulated N in the roots and leaves. However, the N accumulation in biomass of A. peregrina stand was less constrained by environment than in S. parahyba stands. The percentage of N derived from N2 fixation in A. peregrina stands decreased with the increase of stand density. The biological N2 fixation estimates depended on the method and the response of tree species to environment.

scholarly journals Projected Changes in Extreme Temperature and Precipitation Indices Over CORDEX-MENA Domain

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 622
Author(s):  
Tugba Ozturk ◽  
F. Sibel Saygili-Araci ◽  
M. Levent Kurnaz
Keyword(s):  
Regional Climate Model ◽  
Radiative Forcing ◽  
Climate Model ◽  
Global Climate Model ◽  
Regional Climate ◽  
Climate Extreme ◽  
Pronounced Increase ◽  
Temperature And Precipitation ◽  
Projected Changes ◽  
Extreme Indices

In this study, projected changes in climate extreme indices defined by the Expert Team on Climate Change Detection and Indices were investigated over Middle East and North Africa. Changes in the daily maximum and minimum temperature- and precipitation- based extreme indices were analyzed for the end of the 21st century compared to the reference period 1971–2000 using regional climate model simulations. Regional climate model, RegCM4.4 was used to downscale two different global climate model outputs to 50 km resolution under RCP4.5 and RCP8.5 scenarios. Results generally indicate an intensification of temperature- and precipitation- based extreme indices with increasing radiative forcing. In particular, an increase in annual minimum of daily minimum temperatures is more pronounced over the northern part of Mediterranean Basin and tropics. High increase in warm nights and warm spell duration all over the region with a pronounced increase in tropics are projected for the period of 2071–2100 together with decrease or no change in cold extremes. According to the results, a decrease in total wet-day precipitation and increase in dry spells are expected for the end of the century.

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