Showing papers on "Carbon dioxide in Earth's atmosphere published in 1983"

The carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years

Abstract: A computer model has been constructed that considers the effects on the CO/sub 2/ level of the atmosphere, and the Ca, Mg, and HCO/sub 3/ levels of the ocean, of the following processes: weathering on the continents of calcite, dolomite, and calcium-and-magnesium-containing silicates; biogenic precipitation and removal of CaCO/sub 3/ from the ocean; removal of Mg from the ocean via volcanic-seawater reaction; and the metamorphic-magmatic decarbonation of calcite and dolomite (and resulting CO/sub 2/ degassing) as a consequence of plate subduction. Assuming steady state, values for fluxes to and from the atmosphere and oceans are first derived for the modern ocean-atmosphere system. Then the consequences of perturbing steady state are examined by deriving rate expressions for all transfer reactions. These rate expressions are constructed so as to reflect changes over the past 100 my. Results indicate that the CO/sub 2/ content of the atmosphere is highly sensitive to changes in seafloor spreading rate and continental land area, and, to a much lesser extent, to changes in the relative masses of calcite and dolomite. Consideration of a number of alternative seafloor spreading rate formulations shows that in all cases a several-fold higher CO/sub 2/ level for the Cretaceous atmosphere (65-100 mymore » BP) is obtained via the model. Assuming that CO/sub 2/ level and surface air temperature are positively correlated via an atmospheric greenhouse model, they authors predict Cretaceous paleotemperatures which are in rough general agreement with independent published data. Consequently, their results point to plate tectonics, as it affects both metamorphic-magmatic decarbonation and changes in continental land area, as a major control of world climate.« less

Global Deforestation: Contribution to Atmospheric Carbon Dioxide

Abstract: A study of effects of terrestrial biota on the amount of carbon dioxide in the atmosphere suggests that the global net release of carbon due to forest clearing between 1860 and 1980 was between 135 x 10(15) and 228 x 10(15) grams. Between 1.8 x 10(15) and 4.7 x 10(15) grams of carbon were released in 1980, of which nearly 80 percent was due to deforestation, principally in the tropics. The annual release of carbon from the biota and soils exceeded the release from fossil fuels until about 1960. Because the biotic release has been and remains much larger than is commonly assumed, the airborne fraction, usually considered to be about 50 percent of the release from fossil fuels, was probably between 22 and 43 percent of the total carbon released in 1980. The increase in carbon dioxide in the atmosphere is thought by some to be increasing the storage of carbon in the earth's remaining forests sufficiently to offset the release from deforestation. The interpretation of the evidence presented here suggests no such effect; deforestation appears to be the dominant biotic effect on atmospheric carbon dioxide. If deforestation increases in proportion to population, the biotic release of carbon will reach 9 x 10(15) grams per year before forests are exhausted early in the next century. The possibilities for limiting the accumulation of carbon dioxide in the atmosphere through reduction in use of fossil fuels and through management of forests may be greater than is commonly assumed.

Seasonal, latitudinal, and secular variations in the abundance and isotopic ratios of atmospheric carbon dioxide: 1. Results from land stations

Abstract: Between March 1977 and February 1982, 517 samples of air were collected in 51 glass flasks at four stations in the northern hemisphere near the Pacific ocean and at the South Pole. First, the CO2concentration of each sample was determined by nondispersive infrared gas analysis, and then the 13C/12C and 18O/16O ratios of the cryogenic extracted CO2 were determined with a triple collector mass spectrometer. For each station the secular trend and seasonal variation in 13C/12C ratio have been established as a function of CO2 concentration. The seasonally adjusted 13C/12C ratio is found to have decreased at a rate of about 0.02‰ per ppm increase in the seasonally adjusted CO2 concentration and to vary with latitude as expected if CO2 is being released by fossil fuel combustion in the northern hemisphere and from ocean water near the equator. At the three northernmost stations (La Jolla, California, at 33°N and two Hawaiian stations near 19°N) the 13C/12C ratio of the CO2 added to and withdrawn from the atmosphere during one annual cycle is circa −29‰ with respect to standard PDB, as expected from the exchange of atmospheric CO2 with the carbon of terrestrial plants. Near the equator at Fanning Island (4°N) the similarly computed 13C/12C ratio is −21‰, while at the South Pole it is about −13‰. This suggests that the seasonal variation in the southern hemisphere and tropics is partially a result of oceanic CO2 exchange.

The seasonal response of a general circulation model to changes in CO2 and sea temperatures

Abstract: The seasonal response of an atmospheric general circulation model to changes in atmospheric carbon dioxide concentrations and sea surface temperatures is discussed. The model has five layers and a quasi-uniform 330km horizontal grid. Sea surface temperatures, sea ice extents, and zonally mean cloud amounts are prescribed from climatology, so that feedbacks between these variables and the rest of the model are ignored. Soil moisture, snow depth and boundary layer height are modelled explicitly, and both diurnal and seasonal variations of solar zenith angle are included. Two experiments are carried out, and compared with a three-year control integration. In each case, the model's response varies with season and location. In the first experiment the effect of increasing atmospheric carbon dioxide concentrations with prescribed present day sea surface temperatures is examined. The model's troposphere becomes warmer, thereby increasing the low level static stability over the ocean and reducing evaporation and precipitation. The warming is larger over land than over the oceans. In summer, this results in an increase in precipitation along the eastern coasts of continents. In the second experiment, the sea surface temperatures are increased by 2 K and the carbon dioxide concentration is doubled. The land surface temperature rises by 3 K. Evaporation increases markedly over the oceans. Precipitation increases in the main regions of atmospheric convergence and decreases in some regions of the subtropics. The magnitude of the model's response is shown to be reasonably consistent with that found in other three-dimensional climate models.

Response of agronomic and forest species to elevated atmospheric carbon dioxide

Abstract: The effects of atmospheric carbon dioxide on corn, soybeans, loblolly pine, and sweetgum were studied in the field during a growing season. The plants were exposed to a range of concentrations of carbon dioxide day and night in open-topped, flow-through chambers. At a mean daytime carbon dioxide concentration of 910 parts per million, increases in total biomass ranged from 157 to 186 percent of the control values. Seed yield and wood volume increased and there were changes in plant anatomy and form. Net photosynthesis increased with increasing carbon dioxide concentration in soybeans and sweetgum, but was unaffected in corn. Water use efficiency also increased in corn, soybeans, and sweetgum.

General circulation model experiments on the climatic effects due to a doubling and quadrupling of carbon dioxide concentration

Abstract: A global, spectral atmospheric general circulation model (GCM) with an energy balance ocean formulation, sometimes referred to as a swamp ocean, and realistic geography is run for doubled and quadrupled the present amount of atmospheric carbon dioxide, CO2, with fixed and computed clouds. All experiments are compared to control runs with the present amount of CO2. The experiments use annually averaged solar forcing; thus, there is not a seasonal cycle. It is found that globally averaged surface air temperature in the doubled CO2 experiments increases 1.3°C for the fixed cloud formulation and 1.3°C for the computed cloud case. In the quadrupled CO2 experiment with fixed clouds the surface air temperature increase is 2.7°C, and, in the computed cloud it increases 3.4°C. Warming throughout the troposphere is of the order of 1°–2°C for the doubled CO2 cases, and the stratosphere at 30 km cools up to 6°C. In the quadrupled experiment the maximum tropospheric warming is 4°C, and the model stratospheric cooling is 11°C. An analysis of geographic areas of persistent change in snow cover and soil moisture due to a doubling of CO2 for the fixed cloud case shows a general retreat of the snow line and drying of the soil in tropics and mid-latitudes with increases of snow depth in the polar regions. These results indicate warming due to increased CO2 is smaller than that found in other studies with swamp-ocean models coupled to atmospheric GCMs. One possible explanation may be attributed to large differences in the various models used, especially with regard to snow-sea ice albedo parameterizations.

Increasing atmospheric carbon dioxide: possible effects on arctic tundra

Abstract: Cores of wet coastal tundra collected in frozen condition in winter were used as microcosms in a phytotron experiment that assessed the effects of doubling the present atmospheric CO2 concentration, increasing temperature, and depressed water table on net ecosystem CO2 exchange. Doubling atmospheric CO2 had less significance in regard to net carbon capture or loss in this ecosystem as compared to the significant effects of increased temperature and lowered water table level. Both of the latter are to be expected as atmospheric CO2 increases in the Arctic.

Distribution of and changes in industrial carbon dioxide production

Abstract: The burning of fossils fuels is believed to be the major source responsible for an observed increase in the concentration of carbon dioxide in the atmosphere now measured at many locations around the world. This paper revises earlier published data on the annual amounts of carbon released to the atmosphere during the period 1950--1978 and updates the record through 1980. A latitudinal distribution of the fossil fuel source is presented as an aid in explaining the differences in the observed CO/sub 2/ concentrations at several stations. Data from Mauna Loa Observatory, the South Pole, and elsewhere around the world (Keeling et al., 1978a, b; Bolin and Bischof, 1970; Herbert, 1980) show an increase in the concentration of carbon dioxide in the atmosphere. Attempts to deduce from these records information about the global carbon cycle depend upon data pertaining to the sources of CO/sub 2/ introduced by man: burning of fossil fuels and conversion of the world's forests. The latitudinal distribution of the fossil fuel production of CO/sub 2/ should be an important aid in carbon-cycle analysis. Observations in the atmosphere show that the Northern Hemisphere CO/sub 2/ concentration is increasing more rapidly than the Southern Hemisphere concentration and that themore » most rapid increase is at 50/sup 0/--60/sup 0/N latitude. The greatest seasonal variation also occurs in this latitude band. This paper updates and documents the fossil fuel sources of CO/sub 2/. It revises global CO/sub 2/ emission values for 1950--1978 published earlier; it demonstrates that a change in the rate of increase of annual CO/sub 2/ emissions occurred in 1973; and it attempts to delineate the regional distribution of this source of CO/sub 2/.« less

The global distribution of atmospheric carbon dioxide: 1. Aspects of observations and modeling

Abstract: A two-dimensional global atmospheric transport model is used to relate estimated air to surface exchanges of CO2 to spatial and temporal variations of atmospheric concentration of CO2. This serves to illustrate the gross features of the carbon cycle and the measurement precision required of the burgeoning global observational network if the latter is to contribute useful information to the quantitative description of the cycle. Calculations are based on the atmospheric model coupled to a fixed, or variable depth, oceanic mixed layer. Zonally averaged air-sea fluxes of CO2 are estimated from a relationship between flux, partial pressure, temperature, and wind stress. The result is a time-dependent (pre-industrial to 1980) estimate of the meridional rates of net exchange of CO2 with the oceans. For example, it is estimated that, at present, the equatorial oceans release a net total of 1.3 Gt (Gt = 1012 kg) of carbon into the atmosphere annually, while high latitude oceans take up a net total of 4.4 Gt. Associated with the increasing release of fossil-fuel derived CO2 into the northern hemisphere atmosphere, the model suggests that the interhemispheric difference in concentration of CO2 (high latitude north-high latitude south) has changed from ∼-1 ppmv preindustrially to ∼+1 ppmv in 1960 and to 4–5 ppmv at present. The 1960 distribution agrees with the limited observational data available for that time. Present day observations, although provisional, are in good agreement with model estimates of the annual mean global distribution of CO2. The influence of this changing interhemispheric distribution on the concept of the airborne fraction of CO2 is discussed. The sensitivity of the mean global distribution of CO2 to additional surface exchanges is demonstrated by modeling the hypothetical cases of a 1, 2, or 5 Gt yr−1 equatorial source (such as tropical deforestation) with a similar uptake by the temperate northern hemisphere forests. Such changes bring about a 20%, 40%, or 100% reduction, respectively, in the simulated interhemispheric concentration difference. Alternatively, the 1, 2, or 5 Gt yr−1 equatorial release is taken up by the global oceans. In this case, the south pole to equatorial concentration difference increases from 3 ppmv on average to 3.5, 4.0, and 5.5 ppmv, respectively. Taken in conjunction with presently available observations, which must be regarded as provisional, these results place constraints on the magnitude of any actual equatorial deforestation source. It is unlikely that such a source, combined with the sink, could amount to more than about 2 Gt yr−1. The difficulty of establishing more precisely the magnitude of such regional exchanges is discussed in light of the model limitations and required precision of the observational network.

The many origins of natural gas

Abstract: Thermodynamic calculations for the C-O-S-H system indicate that at a fixed oxygen fugacity methane is in a stable phase relative to carbon dioxide at high pressures and low temperatures. At a constant temperature and pressure, methane is favored at low oxygen fugacities. Volcanic gases and near-surface igneous rocks exhibit high values of oxygen fugacity. However, direct measurement of the oxygen fugacity of spinels from peridotites of deep origin indicate that the oxygen fugacity of these rocks is low, corresponding to an iron - wustite buffer. The relative abundance of the carbon isotopes C12 and C13 varies widely in natural gases. Methane formed by bacterial fermentation is highly enriched in the lighter isotope, while methane from deep deposits is much less so as is the methane flowing from hydrothermal vents on the East Pacific Rise. Except In extreme cases, the carbon isotope ratio cannot be used alone to assess whether methane is biogenic or abiogenic. The carbon isotope ratio in coexisting methane and carbon dioxide can be used to estimate the temperature at which the two gases came into isotopic equilibrium. This ratio indicates a high temperature of equilibration for a number of gas deposits. The carbon and helium isotope ratios together with their geologic settings are strongly suggestive that the large quantities of methane in Lake Kivu and the gases venting along the East Pacific Rise are abiogenic. Methane associated with the Red Sea brines and various geothermal areas may also be in part abiogenic. The high abundance of carbon in the Sun, the atmosphere of the outer planets, carbonaceous chondrites and comets, suggests that carbon may be more abundant in the Earth than it is in near-surface igneous rocks. Such a high abundance could lead to a progressive outgassing of methane at depth, which then is oxidized near the surface or in the atmosphere. Methane hydrates are stable at low temperatures and high pressures. Today, methane hydrates are found in areas of permafrost and in ocean sediments. Methane hydrates in ocean sediments were first formed about 20 mya (million years ago) when the Antarctic ice sheet reached sea level. Terrestrial methane hydrates formed more recently during the glaciations beginning 1.6 mya. Methane hydrates and trapped gas are probably abundant under the Antarctic ice sheet. The formation of methane hydrates may be related to the low values of carbon dioxide in the atmosphere some 20,000 years ago.

Feedback mechanisms in the climate system affecting future levels of carbon dioxide

Abstract: The rate of increase of concentration of atmospheric carbon dioxide depends on the consumption of fossil fuels (the major source of ‘new’ carbon dioxide) and the natural sinks for this trace constituent, primarily the oceans and the biosphere. (It is now fairly well established that the biosphere cannot be a major source, as has been claimed.) The rate of operation of these sinks depends on several factors determined by the state of the climate system, and they will therefore presumably change as the greenhouse effect of increasing carbon dioxide warms the earth. Five specific feedback loops are discussed, two of which are positive (amplifying the rate of increase), two are weakly negative (damping the rate of increase), and one is indeterminate but probably positive. It is concluded that it would be well to be prepared for the possibility that carbon dioxide may increase faster than predicted by models based on the current or past state of the climate system.

The global distribution of atmospheric carbon dioxide: 2. A review of provisional background observations, 1978–1980

Abstract: An attempt is made to bring together provisional data collected throughout the world to construct a global picture of the background atmospheric carbon dioxide concentration distribution. The uncertainties, calibration and sampling difficulties, and measurement needs are discussed, and it is concluded that in general the accuracy of the provisional data at each sampling location is approx. +- 1 ppmv. Ongoing studies at the main laboratories are likely to significantly improve this accuracy in the near future. The most recent data available (for 1980) indicate annual average northern hemisphere high latitude CO/sub 2/ concentrations 4 to 5 ppmv above those at high latitudes of the southern hemisphere (approx.336 ppmv). The greatest uncertainty in the zonal average concentration exists in the latitude band 10--30 /sup 0/N where surface observations are 2--3 ppmv higher than those measured by continuous analysis at the Mauna Loa Observatory. There is generally good agreement between a model-generated and the observed annual mean global distributions. The seasonality of concentration is small in the southern hemisphere (approx.1--2 ppmv peak to peak) rising to approx.6 ppmv at 20 /sup 0/N and approx.15 ppmv at high latitudes of the northern hemisphere. The total global atmospheric CO/sub 2/ content, averaged through 1980,more » is estimated to have been 7.15 x 10/sup 14/ kg of carbon with a probable uncertainty of 0.5 to 1.0%.« less

Carbon dioxide exchange between air and seawater: no evidence for rate catalysis.

Abstract: It has been suggested that enzymatic catalysis plays a major role in regulating the mass transport of carbon dioxide from the atmosphere into the oceans. Evidence for this mechanism was not found in a series of gas exchange experiments in which the gas transfer rate coefficients for samples obtained from various natural seawaters, with and without the addition of carbonic anhydrase, were compared with those from artificial seawater. Wind-induced turbulence appears to be the major factor controlling the ocean's response to anthropogenic increases in atmospheric carbon dioxide.

Satellite detection of effects due to increased atmospheric carbon dioxide.

Abstract: The use of satellites to detect climatic changes due to increased carbon dioxide was investigated. This method has several advantages over ground-based methods of monitoring climatic change. Calculations indicate that, by monitoring the outgoing longwave flux for small intervals in the 15-micrometer spectral region, changes in stratospheric temperatures due to doubled atmospheric carbon dioxide are large enough to be detected above the various sources of noise. This method can be extended to other spectral regions so that causal links between changes in outgoing longwave radiation due to other trace gases and the thermal structure of the atmosphere could be established.

Recent temperature changes in the Arctic and Antarctic

Abstract: The possibility of a global warming induced by increasing levels of atmospheric carbon dioxide has led to increased interest in monitoring global temperatures. Polar regions are of particular interest because temperature changes may be amplified in these regions by the complex feedback mechanisms which operate in the atmosphere–ice–ocean system1. Monthly mean station surface air-temperature data have been objectively analysed to produce time series of temperature anomalies for the Northern Hemisphere (1881–1980)2,3, the Arctic (1881–1980)4 and the Antarctic (1957–82)5. A comparison of recent changes in these three regions is made here. Previously published series have been updated to 1982. Changes in Arctic temperatures since about 1966 and in Antarctic temperatures since 1960 show significant warming trends. For the period from 1975 to 1982 there is a high positive correlation between temperature variations in the Arctic and Antarctic.

Climatic effects of atmospheric carbon dioxide

Abstract: This response to a letter re-emphasizes the purpose of the Workshop on the First Detection of Carbon Dioxide Effects which, was to outline a research and analysis program that would provide the information needed to address more completely the issue of CO/sub 2/ warming of the environment and to determine ... whether or not (the climate models) may be grossly in error. The approach proposed by the Workshop participants indicated that definitive conclusions about climatic change should be based on correlated changes in an array of variables, rather than on selected changes in any single variable. A three-pronged effort was outlined to accomplish this objective.

Ecophysiological Effects of Changing Atmospheric CO2 Concentration

Abstract: The earth’s atmosphere and biosphere evolved together over time, the one affecting the other, such that the composition of the atmosphere was strongly influenced by the exchange of gases among them, lithosphere, and hydrosphere. Green plants, through photosynthesis and respiration, have had significant influence on the carbon dioxide, oxygen, and water budgets of the atmosphere.

Carbon dioxide concentrations in some tropical karst soils, west malaysia

Abstract: Summary Regular measurements of carbon dioxide at depths of 15, 30 and 60 cm were made over a period of one year in six karst soils of the Malay peninsula. The data exhibit wide spatial, depth and temporal variations. Mean carbon dioxide concentrations increase with depth and differences in soil properties, especially in air porosity, account for much of the inter-site variability, with the highest carbon dioxide levels occurring in the denser soils formed on impure limestones and on colluvial or alluvial footslope deposits, and the lowest being in the more porous hillslope soils formed on pure limestones. Carbon dioxide concentrations at individual sites vary directly with the amount of antecedent rainfall in periods of 1–32, 1–64 or 1–128 days before sampling. These findings indicate the difficulties of obtaining a reliable mean figure for carbon dioxide in tropical soils, but do suggest that mean concentrations recorded in tropical karst soils probably underestimate the true solutional potential of percolation waters, whereas over-estimation is likely in temperate regions.

Some comments on the exchange of CO2 across the air‐sea interface

Abstract: Boundary values are estimated for the long-term rate of exchange of carbon dioxide between the atmosphere and the ocean, based on the analyses of the experimentally determined shapes of ‘wiggles’ in the atmospheric 14C/12C ratios, for which accurate tree ring data are available for the past 8 millenia. It is shown that the high frequency wiggles (characteristic period of about 200 years) can be explained as entirely due to temporal variations in the global production rate of 14C (estimated maximum range: ±25%) arising from solar modulation of galactic cosmic ray flux provided the mean residence time of carbon dioxide in the atmosphere lies in the range (3–25) years. These calculations are based on a four-box model for the carbon cycle, with a wide range of parameters for the mixed layer of the ocean to simulate the carbon dioxide exchange.

Man’s Influence on Ecosystem Structure, Operation, and Ecophysiological Processes

Abstract: Until the mid-Pleistocene the earth’s biota evolved and formed communities and ecosystems without man as a constituent or as an influent Today no part of the biosphere is free of man’s effects, great or small Even on the high, icy plateau of the South Pole, there is the same rate of increase in atmospheric carbon dioxide as on Mauna Loa in Hawaii This new carbon dioxide is derived mainly from the burning of fossil fuels by industrial peoples

The Role of the Oceans in the Carbon Cycle

Abstract: Of the pools in the terrestrial carbon cycle sharing appreciable flows of carbon, the ocean pool is by far the largest (Fig.1). It contains an amount of dissolved carbon more than fifty times that present in the atmosphere as CO2. The next largest pool is that of economically available fossil carbon, which is probably five times and perhaps as much as ten times the present atmospheric content (Rotty and Narland, 1980). Next in order of decreasing size is the carbon stored on land in live and dead plants and as soil humus, totalling an amount roughly three times the present atmospheric content (Emanuel et al., 1981).

Modelling the Oceanic CO2 Uptake and Future CO2 Levels

Abstract: In 1978, Siegenthaler and Oeschger summarized several predictions about future atmospheric carbon dioxide levels. The authors concluded that of the cumulative inputs one hundred years ahead, between 46 % and 80 % would remain in the atmosphere. One of the causes for the wide range was the uncertainty about which was the most realistic model used in the calculations.

Major Climatic Events Expected during a CO2-Induced Warming

Abstract: During the last 100 years, the atmospheric carbon dioxide content has increased from about 292 ppm to 340 ppm, with an annual growth rate of up to 0.4 %. Because of its role in the atmospheric radiation balance, specialists became increasingly concerned about possible climatic consequences of a continuing rise of the CO2-level (WMO, 1979; Bach 1982; Clark, 1982). The possible climatic consequences have been investigated by means of climate models (e.g. Manabe and Stouffer, 1980; Manabe and Wetherald, 1980; Manabe et al., 1981; Hansen et al., 1981; Gilchrist, this volume), which are as yet unable to describe adequately all feedbacks between atmosphere, ocean and drifting sea ice, and also by paleoclimatic analogs, which are hampered by different boundary conditions then from now (Flohn, 1980). Here I shall discuss two possible major climatic events, both related to a CO2-induced climatic warming prolonged over 100–200 years, and paleoclimatic analogs which have occurred in the past at quite different times. These are: (a) a disintegration of the marine-based part of the West Antarctic ice sheet, causing a 5–7 m rise of the world’s sea-level, as in the last interglacial, about 120,000 yBP; (b) a disappearance of the shallow perennial drifting sea-ice in the Arctic Ocean, associated with a substantial increase of its surface temperature and a major displacement of climatic belts, as in the Late Tertiary, about 14–3.5 MyBP*.