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Carbon-dioxide (CO2) is the main contributor to anthropogenic global warming, and the timing of its peak concentration in the atmosphere is likely to be the major factor in the timing of maximum radiative forcing. Other forcers such as aerosols and non-CO2 greenhouse gases may also influence the timing of maximum radiative forcing. This paper approximates solutions to a linear model of atmospheric CO2 dynamics with four time-constants to identify factors governing the timing of its concentration peak. The most important emissions-related factor is the ratio between average rates at which emissions increase and decrease, which in turn is related to the rate at which the emissions intensity of CO2 is reduced. Rapid decarbonization of CO2 can not only limit global warming but also achieve an early CO2 concentration peak. The most important carbon cycle parameters are the long multi-century time-constant of atmospheric CO2, and the ratio of contributions to the impulse response function of atmospheric CO2 from the infinitely long lived and the multi-century contributions respectively. Reducing uncertainties in these parameters can reduce uncertainty in forecasts of the radiative forcing peak. A simple approximation for peak CO2 concentration, valid especially if decarbonization is slow, is developed. Peak concentration is approximated as a function of cumulative emissions and emissions at the time of the concentration peak. Furthermore peak concentration is directly proportional to cumulative CO2 emissions for a wide range of emissions scenarios. Therefore, limiting the peak CO2 concentration is equivalent to limiting cumulative emissions. These relationships need to be verified using more complex models of Earth system's carbon cycle.
Environmental Research Letters
The time lag between a carbon dioxide emission and maximum warming increases with the size of the emission2015 •
2014 •
Climate Dynamics
CO2 and non-CO2 radiative forcings in climate projections for twenty-first century mitigation scenarios2009 •
IOP Conference Series: Earth and Environmental Science
Time lag between changes in global temperature and atmospheric CO2 content under anthropogenic emissions of CO2 and CH4 into the atmosphere2019 •
The author has enhanced the original one dimensional semi-empirical atmosphere-ocean-biosphere model 1DAOBM based on the four-box presentation. The improved 1DAOBM-2 contains two major parameters, which have been tuned to adjust the total CO 2 net flux rate and the anthropogenic net flux rate from the surface ocean into the deep ocean based on the observed values. The surface ocean part is based on the known dissolution chemical equations according to Henry's law depending on the atmospheric CO 2 concentration and the surface ocean temperature. Simulations have been used to calculate the dynamic responses to the step changes from the actual fossil fuel rate to zero in 1964. The results show that the anthropogenic CO 2 decay rate follows very accurately the observed decay rate of radiocarbon 14 C having the residence time of 16 years. This is the expected result according to nature of anthropogenic CO 2 in the system of the atmosphere, the ocean and the biosphere. The decay rate of the total CO 2 in this system is much longer having the residence time of 55 years matching the adjustment time of 220 years. The simulations of the atmospheric net CO 2 rate by 1DAOBM-2 from 1960 to 2013 confirms the earlier results that the coefficient of determination r 2 = 0.75 (r 2 = 0.81 eliminating the Pinatubo eruption effects). The simulations also show that the present anthropogenic CO 2 fraction in the atmosphere is 8.0%, and it explains the observed δ 13 C value of-8.4‰ extremely well. The problem of the sink Original Research Article
Atmospheric Chemistry and Physics
Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: a multi-model analysis2013 •
ABSTRACT The responses of carbon dioxide (CO2) and other climate variables to an emission pulse of CO2 into the atmosphere are often used to compute the Global Warming Potential (GWP) and Global Temperature change Potential (GTP), to characterize the response timescales of Earth System models, and to build reduced-form models. In this carbon cycle- climate model intercomparison project, which spans the full model hierarchy, we quantify responses to emission pulses of different magnitudes injected under different conditions. The CO2 response shows the known rapid decline in the first few decades followed by a millennium-scale tail. For a 100 Gt-C emission pulse added to a constant CO2 concentration of 389 ppm, 25 ± 9 % is still found in the atmosphere after Ocean Science 1000 yr; the ocean has absorbed 59 ± 12 % and the land the remainder (16 ± 14 %). The response in global mean surface air temperature is an increase by 0.20 ± 0.12 ◦ C within the first twenty years; thereafter and until year 1000, temperature decreases only slightly, whereas ocean heat content and sea level continue to rise. Our best estimate for the Absolute Global Warming Potential, given by the time-integrated response in CO2 at year 100 multiplied by its radiative ef- ficiency, is 92.5 × 10−15 yr W m−2 per kg-CO2. This value very likely (5 to 95 % confidence) lies within the range of (68 to 117) × 10−15 yr W m−2 per kg-CO2. Estimates for time- integrated response in CO2 published in the IPCC First, Second, and Fourth Assessment and our multi-model best estimate all agree within 15 % during the first 100 yr. The integrated CO2 response, normalized by the pulse size, is lower for pre-industrial conditions, compared to present day, and lower for smaller pulses than larger pulses. In contrast, the response in temperature, sea level and ocean heat content is less sensitive to these choices. Although, choices in pulse size, background concentration, and model lead to uncertainties, the most important and subjective choice to determine AGWP of CO2 and GWP is the time horizon.
The dynamics of a linear two-box energy balance climate model is analyzed as a fast–slow system, where the atmosphere, land, and near-surface ocean taken together respond within few years to external forcing whereas the deep-ocean responds much more slowly. Solutions to this system are approximated by estimating the system’s time-constants using a first-order expansion of the system’s eigenvalue problem in a perturbation parameter, which is the ratio of heat capacities of upper and lower boxes. The solution naturally admits an interpretation in terms of a fast response that depends approximately on radiative forcing and a slow response depending on integrals of radiative forcing with respect to time. The slow response is inversely proportional to the “damping-timescale”, the timescale with which deep-ocean warming influences global warming. Applications of approximate solutions are discussed: conditions for a warming peak, effects of an individual pulse emission of carbon dioxide (CO2), and metrics for estimating and comparing contributions of different climate forcers to maximum global warming.
Environmental Research Letters
Climate and carbon budget implications of linked future changes in CO2 and non-CO2 forcingThe carbon cycle is a complex mechanism, however based on data going back to the 1750s we can safely say GMST is rising due to anthropogenic greenhouse gas emissions caused by industrialization. Forecasts were generated from several possible future CO2 emission trends after formulating a set of differential equations based on experimental data. The current technological and political climates trend towards the RCP 4.5 pathway. RCP 4.5 shows carbon emissions peaking between 2040 and 2072, followed by a steady 100 year decline settling at levels comparable to 2017.
Viața românească
Mircea Eliade și America înainte de America (Viața românească, București, CXVIII, nr. 1, ianuarie 2024, pp. 13-23)2024 •
1997 •
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La Arquitectura en Granada a fines del siglo XVI: La escalera del Convento de Santa Cruz la Real1992 •
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Pradhan Mantri Bharatiya Jan Aushadi Pariyojana – An Evaluation of Jan Aushadhi Kendra in Mumbai Metropolitan Region2024 •