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Archive for May, 2010

Papers on peatland greenhouse gas emissions

Posted by Ari Jokimäki on May 27, 2010

This is a list of papers on greenhouse gas emissions from peatlands. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event – Pihlatie et al. (2010) “Fluxes of greenhouse gases (GHG) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC) technique (CO2 and N2O), and automatic and manual chambers (CO2, CH4 and N2O). In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content) in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes during freezing and thawing of the top-soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 and a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat, which were unfrozen throughout the measurement period. During the frost-thaw events of the litter layer distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with a delay after the thawing of the litter layer. CH4 fluxes did not respond to the thawing of the peat soil.” [Full text]

Observations and Status of Peatland Greenhouse Gas Emissions in Europe – Drösler et al. (2008) “A peatland is a type of ecosystem where carbon (C) along with nitrogen and several other elements has been accumulated as peat originating from the plant litter deposited on the site. A logical consequence of the above definition of peatlands is that they are ecosystems, which by way of nature are a sink for atmospheric carbon dioxide (CO2). This is the case because more C is accumulated through photosynthesis than is released through respiration. As a consequence of this, organic matter accumulates as peat. The C accumulated in peatlands is equivalent to almost half the total atmospheric content, and a hypothetical sudden release would result in an instantaneous 50% increase in atmospheric CO2. While this scenario is unrealistic, it nevertheless highlights the central role of peatlands where huge amounts of CO2 have almost entirely been “consumed” since the last glacial maximum, but could respond differently as a result of future changes in climatic conditions. Peatlands have, hence, over the last 10,000 years helped to remove significant amounts of CO2 from the atmosphere. A complicating factor in this respect is that in terms of the major greenhouse gases (GHGs), peatlands are not just acting as a sink for CO2. The wet conditions that lead to the slow decomposition of organic material and enable peat accumulation to occur, also cause significant amounts of the powerful GHG methane (CH4) to be formed. Indeed global wetlands (predominantly peatlands) are considered to be the largest single source of atmospheric CH4 also when considering all anthropogenic emissions. Peatlands are, therefore, also a key player in the atmospheric CH4 budget and as a result also influence the global climate.”

Decadal vegetation changes in a northern peatland, greenhouse gas fluxes and net radiative forcing – Johansson et al. (2006) “This study provides an analysis of how permafrost thawing and subsequent vegetation changes in a sub-Arctic Swedish mire have changed the net exchange of greenhouse gases, carbon dioxide (CO2) and CH4 over the past three decades. Images of the mire (ca. 17 ha) and surroundings taken with film sensitive in the visible and the near infrared portion of the spectrum, [i.e. colour infrared (CIR) aerial photographs from 1970 and 2000] were used. The results show that during this period the area covered by hummock vegetation decreased by more than 11% and became replaced by wet-growing plant communities. The overall net uptake of C in the vegetation and the release of C by heterotrophic respiration might have increased resulting in increases in both the growing season atmospheric CO2 sink function with about 16% and the CH4 emissions with 22%. Calculating the flux as CO2 equivalents show that the mire in 2000 has a 47% greater radiative forcing on the atmosphere using a 100-year time horizon. Northern peatlands in areas with thawing sporadic or discontinuous permafrost are likely to act as larger greenhouse gas sources over the growing season today than a few decades ago because of increased CH4 emissions.” [Full text]

Greenhouse Gas Emissions from Canadian Peat Extraction, 1990–2000: A Life-cycle Analysis – Cleary et al. (2005) “This study uses life-cycle analysis to examine the net greenhouse gas (GHG) emissions from the Canadian peat industry for the period 1990–2000. GHG exchange is estimated for land-use change, peat extraction and processing, transport to market, and the in situ decomposition of extracted peat. The estimates, based on an additive GHG accounting model, show that the peat extraction life cycle emitted 0.54 × 106 t of GHG in 1990, increasing to 0.89 × 106 t in 2000 (expressed as CO2 equivalents using a 100-y time horizon). Peat decomposition associated with end use was the largest source of GHGs, comprising 71% of total emissions during this 11-y period. Land use change resulted in a switch of the peatlands from a GHG sink to a source and contributed an additional 15%. Peat transportation was responsible for 10% of total GHG emissions, and extraction and processing contributed 4%. It would take approximately 2000 y to restore the carbon pool to its original size if peatland restoration is successful and the cutover peatland once again becomes a net carbon sink.” [Full text]

Siberian Peatlands a Net Carbon Sink and Global Methane Source Since the Early Holocene – Smith et al. (2004) “Interpolar methane gradient (IPG) data from ice cores suggest the “switching on” of a major Northern Hemisphere methane source in the early Holocene. Extensive data from Russia’s West Siberian Lowland show (i) explosive, widespread peatland establishment between 11.5 and 9 thousand years ago, predating comparable development in North America and synchronous with increased atmospheric methane concentrations and IPGs, (ii) larger carbon stocks than previously thought (70.2 Petagrams, up to 26% of all terrestrial carbon accumulated since the Last Glacial Maximum), and (iii) little evidence for catastrophic oxidation, suggesting the region represents a long-term carbon dioxide sink and global methane source since the early Holocene.”

Exchange of greenhouse gases between soil and atmosphere: interactions of soil physical factors and biological processes – Smith et al. (2003) A review article. “This review examines the interactions between soil physical factors and the biological processes responsible for the production and consumption in soils of greenhouse gases. The release of CO2 by aerobic respiration is a non-linear function of temperature over a wide range of soil water contents, but becomes a function of water content as a soil dries out. Some of the reported variation in the temperature response may be attributable simply to measurement procedures. Lowering the water table in organic soils by drainage increases the release of soil carbon as CO2 in some but not all environments, and reduces the quantity of CH4 emitted to the atmosphere. Ebullition and diffusion through the aerenchyma of rice and plants in natural wetlands both contribute substantially to the emission of CH4; the proportion of the emissions taking place by each pathway varies seasonally. Aerated soils are a sink for atmospheric CH4, through microbial oxidation. The main control on oxidation rate is gas diffusivity, and the temperature response is small. Nitrous oxide is the third greenhouse gas produced in soils, together with NO, a precursor of tropospheric ozone (a short-lived greenhouse gas). Emission of N2O increases markedly with increasing temperature, and this is attributed to increases in the anaerobic volume fraction, brought about by an increased respiratory sink for O2. Increases in water-filled pore space also result in increased anaerobic volume; again, the outcome is an exponential increase in N2O emission.” [Full text]

Carbon balance and radiative forcing of Finnish peatlands 1900–2100 – the impact of forestry drainage – Minkkinen et al. (2002) “In this paper, changes in peat and tree stand C stores, GHG fluxes and the consequent RF of Finnish undisturbed and forestry-drained peatlands are estimated for 1900–2100. The C store in peat is estimated at 5.5 Pg in 1950. The rate of C sequestration into peat has increased from 2.2 Tg a-1 in 1900, when all peatlands were undrained, to 3.6 Tg a-1 at present, when c. 60% of peatlands have been drained for forestry. The C store in tree stands has increased from 60 to 170 Tg during the 20th century. Methane emissions have decreased from an estimated 1.0–0.5 Tg CH4–C a-1, while those of N2O have increased from 0.0003 to 0.005 Tg N2O–N a-1. The altered exchange rates of GHG gases since 1900 have decreased the RF of peatlands in Finland by about 3 mW m-2 from the predrainage situation. This result contradicts the common hypothesis that drainage results in increased C emissions and therefore increased RF of peatlands. The negative radiative forcing due to drainage is caused by increases in CO2 sequestration in peat (–0.5 mW m-2), tree stands and wood products (–0.8 mW m-2), decreases in CH4 emissions from peat to the atmosphere (–1.6 mW m-2), and only a small increase in N2O emissions (+0.1 mW m-2). Although the calculations presented include many uncertainties, the above results are considered qualitatively reliable and may be expected to be valid also for Scandinavian countries and Russia, where most forestry-drained peatlands occur outside Finland.”

Peatlands, carbon storage, greenhouse gases, and the Kyoto Protocol: Prospects and significance for Canada – Roulet (2000) “Natural peatlands are presently a relatively small sink for CO2 and a large source of CH4: globally, they store between 400 and 500 Gt C. There are large variations among peatlands, but when the “global warming potential” of CH4 is factored in, many peatlands are neither sinks nor sources of GHGs. Some land-use changes may result in peatlands acting as net sinks for GHGs by reducing CH4 emissions and/or increasing CO2 sequestration (e.g., forest drainage), while other land uses may result in large losses of CO2, CH4, and N2O (e.g., agriculture on organic soils, flooding for hydroelectric generation). Other land uses, such as peatland creation and restoration, produce no net change if they are replacing or restoring a previous level of GHG exchange.”

CO2 Fluxes from Peat in Boreal Mires under Varying Temperature and Moisture Conditions – Silvola et al. (1996) “CO2 emissions in boreal peatlands were measured during two seasons on various mire site types representing different nutrient statuses and water tables. In order to examine the long term effects of water table draw-down on the CO2 fluxes, the sites also included 25-50-year-old drainages. On virgin sites the lowest CO2 fluxes were measured at ombrotrophic sites dominated by Sphagnum fuscum (78-127 mg CO2 m super(-2) h super(-1) at 12 degree C, 60-200 g CO sub(2)-C m super(-2) year super(-1)) and the highest CO2 fluxes were at ombrotrophic sites with abundant under-storey vegetation (183-259 mg CO2 m super(-2) h super(-1) at 12 degree C, 290-340 g CO2-C m super(-2) year super(-1)). Lowering of the water table by 1 cm increased CO2 fluxes by an average of 7.1 mg CO2 m super(-2) h super(-1) at 12 degree C and 9.5 g CO2-C m super(-2) year super(-1). In some cases the effect of ditches on the water table, and correspondingly on CO2 fluxes, was small. However, effective draining caused approximately 100% increase in CO2 fluxes. Drainages had higher CO2 fluxes compared with virgin subsites at the same temperature and water table. The effect of temperature on CO2 fluxes depended on the water table, the average Q sub(10) value being 2.9 with water tables of 0-20 cm and 2.0 with water tables below 20 cm. CO2 fluxes are compared with primary production figures, and peat carbon stores and the carbon balance in changing climate are discussed.”

Impact on the Greenhouse Effect of Peat Mining and Combustion – Rodhe & Svensson (1995) “Combustion of peat leads to emission of carbon dioxide (CO2) to the atmosphere. In addition, mining of the peat alters the environment such that the natural fluxes of CO2 and other greenhouse gases are modified. Of particular interest is a reduction in the emission of methane (CH4) in the drained parts of the mires. We estimate the total impact on the greenhouse effect of these processes. The results indicate that the decreased emission of methane from the drained mires compensates for about 15% of the CO2 emission during the combustion of the peat. It follows that, in a time perspective of less than several hundred years, peat is comparable to a fossil fuel, as far as the contribution to the greenhouse effect is concerned.”

The influence of temperature and water table position on carbon dioxide and methane emissions from laboratory columns of peatland soils – Moore & Dalva (1993) “Laboratory columns (80 cm long, 10 cm diameter) of peat were constructed from samples collected from a subarctic fen, a temperate bog and a temperate swamp. Temperature and water table position were manipulated to establish their influence on emissions of CO2 and CH4 from the columns. A factorial design experiment revealed significant (P < 0.05) differences in emission of these gases related to peat type, temperature and water table position, as well as an interaction between temperature and water table. Emissions of CO2 and CH4 at 23°C were an average of 2.4 and 6.6 times larger, respectively, than those at 10°C. Compared to emissions when the columns were saturated, water table at a depth of 40 cm increased CO2 fluxes by an average of 4.3 times and decreased CH4 emissions by an average of 5.0 times. There were significant temporal variations in gas emissions during the 6-week experiment, presumably related to variations in microbial populations and substrate availability. Using columns with static water table depths of 0, 10, 20, 40 and 60 cm, CO2 emissions showed a positive, linear relation with depth, whereas CH4 emissions revealed a negative, logarithmic relation with depth. Lowering and then raising the water table from the peat surface to a depth of 50 cm revealed weak evidence of hysteresis in CO2 emissions between the falling and rising water table limbs. Hysteresis (falling > rising limb) was very pronounced for CH4 emissions, attributed to a release of CH4 stored in porewater and a lag in the development of anaerobic conditions and methanogenesis on the rising limb. Decreases in atmospheric pressure were correlated with abnormally large emissions of CO2 and CH4 on the falling limb. Peat slurries incubated in flasks revealed few differences between the three peat types in the rates of CO2 production under aerobic and anaerobic conditions. There were, however, major differences between peat types in the rates of CH4 consumption under aerobic incubation conditions and CH4 production under anaerobic conditions (bog > fen > swamp), which explain the differences in response of the peat types in the column experiment.”

Effect of a lowered water table on nitrous oxide fluxes from northern peatlands – Martikainen et al. (1993) “Here we present a comparison of present-day N2O fluxes from virgin peatlands in Finland with those from sites in the same regions that were drained by ditching 30 and 50 years ago. The lowered water table had no effect on N2O emissions from nutrient-poor peat but enhanced those from nutrient-rich peat. We estimate that equivalent drying caused by climate change would increase the total emissions of N2O from northern peatlands by 0.03–0.1 teragrams of nitrogen per year, which is just 0.3–1% of the present global annual emissions. Thus northern peatlands are unlikely to exert a significant climate feedback from N2O emissions.”

Fluxes of CO2, CH4 and N2O from a Welsh peatland following simulation of water table draw-down: Potential feedback to climatic change – Freeman et al. (1992) “A potential effect of climatic change was simulated by manipulating the water table height within intact peat monoliths. The treatment decreased methane flux (maximum –80%) and increased both carbon dioxide flux (maximum 146%) and nitrous oxide flux maximum 936%). Returning the water table height to its original level caused both nitrous oxide and carbon dioxide flux to rapidly return to control levels. However, methane flux remained at its experimentally induced low levels.”

Northern Peatlands: Role in the Carbon Cycle and Probable Responses to Climatic Warming – Gorham (1991) “Boreal and subarctic peatlands comprise a carbon pool of 455 Pg that has accumulated during the postglacial period at an average net rate of 0.096 Pg/yr (1 Pg = 1015g). Using Clymo’s (1984) model, the current rate is estimated at 0.076 Pg/yr. Longterm drainage of these peatlands is estimated to be causing the oxidation to CO2 of a little more than 0.0085 Pg/yr, with conbustion of fuel peat adding °0.026 Pg/yr. Emissions of CH4 are estimated to release ° 0.046 Pg of carbon annually. Uncertainties beset estimates of both stocks and fluxes, particularly with regard to Soviet peatlands.” [Full text]

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Climate science newslog

Posted by Ari Jokimäki on May 26, 2010

I just noticed a nice resource on climate science news and research – the Tietoukka Monitor. Site seems to be dedicated to giving links to climate related news and research. I’ll check out especially the research links in the right sidebar.

Last but not least – the site is run by a fellow Finn, so that alone is a good reason to give the place a visit. :)

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Papers on temperature of Mars

Posted by Ari Jokimäki on May 24, 2010

This is a list of papers on the temperature of planet Mars. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Mars Climate Sounder limb profile retrieval of atmospheric temperature, pressure, and dust and water ice opacity – Kleinböhl et al. (2009) “The Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter is the latest of a series of investigations devoted to improving the understanding of current Martian climate. MCS is a nine-channel passive midinfrared and far-infrared filter radiometer designed to measure thermal emission in limb and on-planet geometries from which vertical profiles of atmospheric temperature, water vapor, dust, and condensates can be retrieved. Here we describe the algorithm that is used to retrieve atmospheric profiles from MCS limb measurements for delivery to the Planetary Data System. … Temperature profiles are retrieved over a range from 5–10 to 80–90 km altitude with a typical altitude resolution of 4–6 km and a precision between 0.5 and 2 K over most of this altitude range. … Examples of temperature profiles as well as dust and water ice opacity profiles from the first year of the MCS mission are presented, and atmospheric features observed during periods employing different MCS operational modes are described. An intercomparison with historical temperature measurements from the Mars Global Surveyor mission shows good agreement.”

Global warming and climate forcing by recent albedo changes on Mars – Fenton et al. (2007) “Here we present predictions from a Mars general circulation model, indicating that the observed interannual albedo alterations strongly influence the martian environment. … The simulations also predict a net annual global warming of surface air temperatures by 0.65 K, enhancing dust lifting by increasing the likelihood of dust devil generation.” [Full text]

Polar warming in the Mars thermosphere: Seasonal variations owing to changing insolation and dust distributions – Bougher et al. (2006) “Warming of the martian lower thermosphere (100–130 km) at north polar latitudes near the perihelion/winter solstice (Ls = 270) was recently observed. No analogous warming has been observed within the south polar thermosphere during its aphelion/winter season (Ls ∼ 90). … The stronger interhemispheric circulation during northern winter is clearly driven by stronger insolation and dust heating near perihelion, resulting in subsidence and warmer temperatures in the northern polar night.” [Full text]

Interannual variability in TES atmospheric observations of Mars during 1999–2003 – Smith (2004) “We use infrared spectra returned by the Mars Global Surveyor Thermal Emission Spectrometer (TES) to retrieve atmospheric and surface temperature, dust and water ice aerosol optical depth, and water vapor column abundance. The data presented here span more than two martian years (Mars Year 24, Ls=104°, 1 March 1999 to Mars Year 26, Ls=180°, 4 May 2003). … We find that the perihelion season (Ls=180°–360°) is relatively warm, dusty, free of water ice clouds, and shows a relatively high degree of interannual variability in dust optical depth and atmospheric temperature. On the other hand, the aphelion season (Ls=0°–180°) is relatively cool, cloudy, free of dust, and shows a low degree of interannual variability. … These dust storms increase albedo through deposition of bright dust on the surface causing cooler daytime surface and atmospheric temperatures well after dust optical depth returns to prestorm values.” [Full text]

An assessment of the global, seasonal, and interannual spacecraft record of Martian climate in the thermal infrared – Liu et al. (2003) “Intercomparison of thermal infrared data collected by Mariner 9, Viking, and Mars Global Surveyor (MGS) is presented with a specific focus on air temperatures, dust opacities, and water ice opacities. … The annual cycle consistently shows a strong asymmetry about the equinoxes, with northern spring and summer exhibiting relatively low temperatures, very high year-to-year repeatability, and essentially no short-term (tens of days) variability. The globally averaged Martian nighttime air temperatures close annually to within a Kelvin during northern spring and summer. Daytime temperatures show more variability (3–6 K). The difference in repeatability of daytime versus nighttime temperatures is not understood. Viking and MGS air temperatures are essentially indistinguishable for this period, suggesting that the Viking and MGS eras are characterized by essentially the same climatic state.” [Full text]

An intercomparison of ground-based millimeter, MGS TES, and Viking atmospheric temperature measurements: Seasonal and interannual variability of temperatures and dust loading in the global Mars atmosphere – Clancy et al. (2000) “Much colder (10–20 K) global atmospheric temperatures were observed during the 1997 versus 1977 perihelion periods (Ls =200°–330°), consistent with the much (2 to 8 times) lower global dust loading of the atmosphere during the 1997 perihelion dust storm season versus the Viking period of the 1977a,b storms.” [Full text]

The Martian Atmosphere During the Viking Mission, I: Infrared Measurements of Atmospheric Temperatures Revisited – Wilson & Richardson (2000) “The Viking Infrared Thermal Mapper 15-μm channel brightness temperature observations (IRTM T15) provide extensive spatial and temporal coverage of martian atmospheric temperatures on diurnal to seasonal time scales. … Our re-examination of the IRTM data indicates that the 15-μm channel was additionally sensitive to surface radiance so that air temperature determinations (nominal T15) are significantly biased when the thermal contrast between the surface and atmosphere is large. … A major consequence of this work is the improved definition of the diurnal, latitudinal, and seasonal variation of martian atmosphere temperatures during the Viking mission. An accounting for the surface temperature bias resolves much of the discrepancy between IRTM and corresponding microwave observations, indicating that there is relatively little interannual variability in global temperatures during the aphelion season.” [Full text]

Global changes in the 0–70 km thermal structure of the Mars atmosphere derived from 1975 to 1989 microwave CO spectra – Clancy et al. (1990) “Assuming a constant CO mixing ratio, we derive atmospheric temperature profiles from the May 1988 and January 1989 12CO spectra which are quite similar to the temperature profile found for the November 1988 period. … The March-April 1980 and January 1982 profiles, in particular, are 20–40 K cooler than the Viking profile for altitudes above 10 km.”

Mars South Polar Spring and Summer Temperatures: A Residual CO2 Frost – Kieffer (1979) “The Viking infrared thermal mapper (IRTM) has measured reflected and emitted energy over Mars south polar cap throughout the martian spring and summer. During these 1976–1977 observations the polar cap displayed complex spatial, spectral, and temporal variations.”

Martian Surface Temperatures – Morrison (1968) “The 8- to 13-μ thermal scans made of Mars in 1954 by Sinton and Strong are the best source of information available on the distribution of temperature over the disk. I have analyzed all these scans, normalizing to the center-of-disk temperature in the light areas of 290° K found by Sinton and Strong. The observed equatorial temperature distribution between sunrise and midafternoon can be reproduced by a solution of the standard heat-conduction equation for a homogeneous subsurface when current values for the planetary albedo and emissivity are employed. The temperature range in the bright areas is from 303 to 180° K with a thermal inertia of 0.004 to 0.005 cal cm-2 sec deg-1 the thermal inertia of the dark areas is slightly larger. Mean particle sizes for the two areas are estimated from the thermal conductivities to be 20 to 40 μ and 100 to 300 μ, respectively. The latitudinal temperature gradient is in accord with the above model for northern latitudes, but in the south the temperatures are depressed, consistent with the presence of a polar cap of frozen carbon dioxide. At all latitudes, a major fraction of the atmospheric water vapor is expected to condense at night. The radio brightness temperatures observed at centimeter wavelengths are also consistent with these thermal properties.” [Full text is freely available in the abstract page]

Disk Temperatures of Mercury and Mars at 3.4 MM – Epstein (1966) “Observations of Mercury and Mars were made in April, 1965, at 3.4 mm (88 GHz) with the 15-foot antenna of Aerospace Corporation’s Space Radio Systems Facility. … Mars was observed on the nights of April 25, 26, and 28. …the corresponding black-body disk-temperature and estimated total standard error were 190° ± 40° K.” [Full text is freely available in the abstract page]

Observed millimeter wavelength brightness temperatures of Mars, Jupiter, and Saturn – Tolbert (1966) “Analyses of observations of 35, 70, and 94 Gc radiation from Mars, Jupiter, and Saturn made with a 16-ft antenna yield brightness temperatures for Mars of 230(+42, -42) °K and 240(+72, -48) °K at 35 and 94 Gc, respectively;…” [Full text is freely available in the abstract page]

Theoretical Estimates of the Average Surface Temperature on Mars – Ohring et al. (1962) “Estimates of the average surface temperature on Mars are derived from radiative equilibrium considerations. A minimum possible surface temperature is estimated by computing the radiative equilibrium temperature that the Martian surface would have if the planet had no atmosphere. An estimate of the maximum possible value of the average surface temperature is obtained by computing the surface temperature that would result from a maximum greenhouse model. The computations indicate that the average surface temperature is in the range 219K to 233K. Comparisons of the theoretical computations with indications of surface temperature obtained from thermal emission observations are found to be in reasonable agreement.” [Full text]

The Surface-Temperature Climate of Mars – Gifford (1956) “The Lowell Observatory radiometric measurements of Martian surface temperatures are analyzed, and surface-temperature climatological properties of Mars are obtained. Annual and diurnal temperature variations and seasonal isotherm maps are displayed and discussed.” [Full text is freely available in the abstract page]

Temperature measurements on the planet Mars, 1926 – Coblentz (1927) Introduces new measurements from 1926. “…the following tentative estimates of planetary surface temperatures are given: as viewed on the central meridian, the south polar region -10° to +10° C; south temperate zone 20° to 25° C (clouds -10° C); center of disc 20° to 30° C; north temperate zone 0° to 20° C; north polar region -25° to -40° C;…” [Full text is freely available in the abstract page] [Another paper on the 1926 observations: Temperatures of Mars, 1926, as derived from the Water-Cell Transmissions - Coblentz et al. (1927)]

The Diurnal Maximum of Temperature on Mars – Pettit & Nicholson (1925) A clarification of their measurements published originally in 1924. [Full text is freely available in the abstract page]

Temperature estimates of the planet Mars – Coblentz (1925) “The temperature which the surface of Mars attains when exposed to solar radiation is a much debated question. Some of the older calculations, for example Poynting’s, indicated a temperature much below o° C. More recently Lowell introduced factors previously neglected, and calculated temperatures considerably above o° C. (up to 9° C). … The object of the present paper is to summarize the radiometric observations obtained on Mars in 1924; and to estimate the surface temperature as deduced by various methods of calculating the data. … The temperatures of the bright areasrange from -10° C. to +5° C. The temperatures of the dark areas, range from 10° C. to 20° C. or even higher. The average temperature of the apparent center of the disk, including the bright and the dark areas, was 14° C.” [Full text is freely available in the abstract page]

The Temperature of Mars – Chase (1924) “IN a recent paper (Pub. Ast. Soc. of the Pacific), Nicholson and Pettit calculate the temperature of the planet Mars, based on their radiation measures made at Mount Wilson. Most confidence is placed on measures made in the region 8 to 14µ, by the use of filter screens, and an emissivity of unity is assumed for all wave-lengths. However, Mars, being probably composed of material not unlike the earth, would radiate more like sand or quartz than like a black body, and it can be calculated from curves given by Wood (“Physical Optics”) and data given by Rosenthal (Wied. Ann. 68, p. 783), that the average ratio of the emissivity of quartz to that of a black body in the region 8 to 14µ, is 0.819. The values of the emissivity of quartz given are far below that of a black body between 8 and 10 µ they are nearly the same from 10 to 14µ the average ratio is taken.”

The Temperature of Mars – Coblentz (1924)

Measurements of the radiation from the planet Mars – Pettit & Nicholson (1924) “We may estimate the temperature of a point on Mars by two methods. First we may attempt to make the data in Table I fit ablack body radiation curve after applying the atmospheric transmission to it, or we may employ the principle of the total radiation formula (fourth power law). … From these results we may conclude that the radiation temperature of a point in the tropics at noon-day on Mars is a little above freezing and that the mean temperature of the pole cap is about -70° C.” [Full text is freely available in the abstract page] [same article in journal PASP]

Present Surface Temperatures of Mars, Venus and Mercury – Corrigan (1908) “Therefore, the surface temperatures are: for Mars 5640°/6800° x 512° = 424°; or -36° Fahrenheit; for Venus 7120°/6800° x 512° = 536°; or +76° Fahrenheit, and for Mercury 7934°/6800° x 512° = 597°; or 137° Fahrenheit. … These are the temperatures due to the internal planetary heat alone, the augmentation caused by thermal radiation from the Sun being an independent quantity the maximum value whereof may be taken at about 70° F for the Earth, which would give, as the greatest temperature on the surface exposed to direct solar heat, the maximum intrinsic temperature 52° + the solar augmentation 70°, or 122° F, which is about greatest temperature (in the shade) recorded in the hottest regions of our globe. The augmentation in the case of each of the other three planets is, obviously, inversely proportional to the square of its relative distance from the Sun, so that for Mars the value to be added to the intrinsic temperature (-36°) aforesaid is + 76° F, making the actual surface temperature 0° Fahrenheit, from which determination it may be inferred that the climate of Mars, at best, is one of Arctic severity or that of an elevated plateau at an altitude of four, or five miles above sea-level, with respect to temperature compared with terrestrial conditions in this regard, and that the types of life thereon (if any there be) must correspond to those existing upon the Earth in similar situations.” [Full text is freely available in the abstract page]

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Papers on the deglaciation of snowball Earth

Posted by Ari Jokimäki on May 17, 2010

This is a list of papers on the deglaciation of snowball Earth, i.e. papers studying how Earth came back from the “snowball” state. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (August 8, 2011): Font et al. (2010) added. Thanks to Eric Font for pointing out (see the comment section below).
UPDATE (July 25, 2011): Hu et al. (2011) added. Thanks to Jun Yang for pointing it out (see the comment section below).

Model-dependence of the CO2 threshold for melting the hard Snowball Earth – Hu et al. (2011) “One of the critical issues of the Snowball Earth hypothesis is the CO2 threshold for triggering the deglaciation. Using Community Atmospheric Model version 3.0 (CAM3), we study the problem for the CO2 threshold. Our simulations show large differences from previous results (e.g. Pierrehumbert, 2004, 2005; Le Hir et al., 2007). At 0.2 bars of CO2, the January maximum near-surface temperature is about 268 K, about 13 K higher than that in Pierrehumbert (2004, 2005), but lower than the value of 270 K for 0.1 bar of CO2 in Le Hir et al. (2007). It is found that the difference of simulation results is mainly due to model sensitivity of greenhouse effect and longwave cloud forcing to increasing CO2. At 0.2 bars of CO2, CAM3 yields 117 Wm−2 of clear-sky greenhouse effect and 32 Wm−2 of longwave cloud forcing, versus only about 77 Wm−2 and 10.5 Wm−2 in Pierrehumbert (2004, 2005), respectively. CAM3 has comparable clear-sky greenhouse effect to that in Le Hir et al. (2007), but lower longwave cloud forcing. CAM3 also produces much stronger Hadley cells than that in Pierrehumbert (2005). Effects of pressure broadening and collision-induced absorption are also studied using a radiative-convective model and CAM3. Both effects substantially increase surface temperature and thus lower the CO2 threshold. The radiative-convective model yields a CO2 threshold of about 0.21 bars with surface albedo of 0.663. Without considering the effects of pressure broadening and collision-induced absorption, CAM3 yields an approximate CO2 threshold of about 1.0 bar for surface albedo of about 0.6. However, the threshold is lowered to 0.38 bars as both effects are considered.” Hu, Y., Yang, J., Ding, F., and Peltier, W. R., Clim. Past, 7, 17-25, doi:10.5194/cp-7-17-2011, 2011. [Full text]

Fast or slow melting of the Marinoan snowball Earth? The cap dolostone record – Font et al. (2010) “The end of the Neoproterozoic era is punctuated by two global glacial events marked by the presence of glacial deposits overlaid by cap carbonates. Duration of glacial intervals is now consistently constrained to 3–12 million years but the duration of the post-glacial transition is more controversial due to the uncertainty in cap dolostone sedimentation rates. Indeed, the presence of several stratabound magnetic reversals in Brazilian cap dolostones recently questioned the short sedimentation duration (a few thousand years at most) that was initially suggested for these rocks. Here, we present new detailed magnetostratigraphic data of the Mirassol d’Oeste cap dolostones (Mato Grosso, Brazil) and “bomb-spike” calibrated AMS 14C data of microbial mats from the Lagoa Vermelha (Rio de Janeiro, Brazil). We also compile sedimentary, isotopic and microbiological data from post-Marinoan outcrops and/or recent depositional analogues in order to discuss the deposition rate of Marinoan cap dolostones and to infer an estimation of the deglaciation duration in the snowball Earth aftermath. Taken together, the various data point to a sedimentation duration in the range of a few 105 years.” E. Font, A. Nédélec, R.I.F. Trindade and C. Moreau, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 295, Issues 1-2, 1 September 2010, Pages 215-225, doi:10.1016/j.palaeo.2010.05.039.

Mudball: Surface dust and Snowball Earth deglaciation – Abbot & Pierrehumbert (2010) “Here we argue that over the lifetime of a Snowball event, ice dynamics should lead to the development of a layer of continental and volcanic dust at the ice surface in the tropics that would significantly lower the tropical surface albedo and encourage deglaciation. This idea leads to the prediction that clay drapes found on top of Neoproterozoic glaciations should be thicker in tropical than extratropical regions. We test this idea by running the FOAM general circulation model (GCM) with an added tropical dust layer of different sizes and albedos and find that the tropical dust layer causes Snowball deglaciation at pCO2 = 0.01–0.1 bar in a reasonable regime of these parameters.” [Full text]

Toward the snowball earth deglaciation… – Le Hir et al. (2010) “The current state of knowledge suggests that the Neoproterozoic snowball Earth is far from deglaciation even at 0.2 bars of CO2. Since understanding the termination of the fully ice-covered state is essential to sustain, or not, the snowball Earth theory, we used an Atmospheric General Climate Model (AGCM) to explore some key factors which could induce deglaciation. After testing the models’ sensitivity to their parameterizations of clouds, CO2 and snow, we investigated the warming effect caused by a dusty surface, associated with ash release during a mega-volcanic eruption. We found that the snow aging process, its dirtiness and the ash deposition on the snow-free ice are key factors for deglaciation. Our modelling study suggests that, under a CO2 enriched atmosphere, a dusty snowball Earth could reach the deglaciation threshold.” [Full text]

Scenario for the evolution of atmospheric pCO2 during a snowball Earth – Le Hir et al. (2008) “In this contribution, we question this assumed linear accumulation of CO2 into the atmosphere. Using a numerical model of the carbon-alkalinity cycles, we suggest that during global glaciations, even a limited area of open waters (103 km2) allows an efficient atmospheric CO2 diffusion into the ocean. This exchange implies that the CO2 consumption through the low-temperature alteration of the oceanic crust persists throughout the glaciation. Furthermore, our model shows that rising CO2 during the glaciation increases the efficiency of this sink through the seawater acidification. As a result, the atmospheric CO2 evolution is asymptotic, limiting the growth rate of the atmospheric carbon reservoir. Even after the maximum estimated duration of the glaciation (30 m.y.), the atmospheric CO2 is far from reaching the minimum deglaciation threshold (0.29 bar).”

Sedimentary challenge to Snowball Earth – Allen & Etienne (2008) “However, sedimentary rocks deposited during these cold intervals indicate that dynamic glaciers and ice streams continued to deliver large amounts of sediment to open oceans throughout the glacial cycle. The sedimentary evidence therefore indicates that despite the severity of glaciation, some oceans must have remained ice-free. Significant areas of open ocean have important implications for the survival and diversification of life and for the workings of the global carbon cycle.”

Investigating plausible mechanisms to trigger a deglaciation from a hard snowball Earth – Le Hir et al. (2007) “Those results show that the cause of deglaciation is unresolved and the discussion about a plausible escape scenario remains open. For this reason, to test and to determine the sensitivity and efficiency of the greenhouse effect during a ‘hard’ snowball–Earth, we compare the FOAM results with those of LMDz (AGCM of the ‘Laboratoire de météorologie dynamique’). The preliminary results show that LMDz is much more sensitive to a CO2 increase than FOAM. This article shows that among processes that could explain this difference, the key factor is the cloud parameterization and its interaction with the convective scheme. These simulations suggest that the CO2 threshold is dependent on the GCM parameterization used, and could be lower than the one suggested by FOAM. Moreover, to investigate other plausible mechanisms able to melt the equatorial ice, we have tested the CH4 impact with a simple 0D model, INCA-ZD. Results show that the balance between the residence times of CH4 in a ‘hard’ snowball–Earth scenario is largely overcome by the extinction of the organic source, which means that CO2 remains the only greenhouse gas warming the snowball Earth.” [Full text]

Deglaciating the snowball Earth: Sensitivity to surface albedo – Lewis et al. (2006) “Here we attempt to quantify the relative sensitivity of different surface albedos, using the University of Victoria’s Earth System Climate Model, to deglaciating the snowball Earth. We investigate the sensitivity of ice, snow, and land albedo on the minimum CO2 greenhouse forcing required for deglaciating the Neoproterozoic snowball Earth. We find that the amount of CO2 forcing required for deglaciation can vary by nearly an order of magnitude within accepted albedo ranges.” [Full text]

Climate dynamics of a hard snowball Earth – Pierrehumbert (2005) “The problem of deglaciating a globally ice-covered (“hard snowball”) Earth is examined using a series of general circulation model simulations. The aim is to determine the amount of CO2 that must be accumulated in the atmosphere in order to trigger deglaciation. … In contrast to prevailing expectations, the hard snowball Earth is found to be nearly 30 K short of deglaciation, even at .2 bars. The very cold climates arise from a combination of the extreme seasonal and diurnal cycle, lapse rate effects, snow cover, and weak cloud effects. Several aspects of the atmospheric dynamics are examined in detail. The simulations indicate that the standard scenario, wherein snowball termination occurs after a few tenths of a bar of CO 2 has built up following cessation of weathering, is problematic. However, the climate was found to be sensitive to details of a number of parameterized physical processes, notably clouds and heat transfer through the stable boundary layer. It is not out of the question that other parameterization suites might permit deglaciation. The results should not be construed as meaning that the hard snowball state could not have occurred, but only that deglaciation requires the operation of as-yet undiscovered processes that would enhance the climate sensitivity.” [Full text]

High levels of atmospheric carbon dioxide necessary for the termination of global glaciation – Pierrehumbert (2004) “Termination of such ‘hard snowball Earth’ climate states has been proposed to proceed from accumulation of carbon dioxide in the atmosphere4. Many salient aspects of the snowball scenario depend critically on the threshold of atmospheric carbon dioxide concentrations needed to trigger deglaciation2, 5. Here I present simulations with a general circulation model, using elevated carbon dioxide levels to estimate this deglaciation threshold. The model simulates several phenomena that are expected to be significant in a ‘snowball Earth’ scenario, but which have not been considered in previous studies with less sophisticated models, such as a reduction of vertical temperature gradients in winter, a reduction in summer tropopause height, the effect of snow cover and a reduction in cloud greenhouse effects. In my simulations, the system remains far short of deglaciation even at atmospheric carbon dioxide concentrations of 550 times the present levels (0.2 bar of CO2). I find that at much higher carbon dioxide levels, deglaciation is unlikely unless unknown feedback cycles that are not captured in the model come into effect.”

CO2 levels required for deglaciation of a “near‐snowball” Earth – Crowley et al. (2001) “Although 0.1 to 0.3 of an atmosphere of CO2 (∼300 to 1000 X) is required for deglaciation of a “Snowball Earth,” the “exit” CO2 levels for an open water solution could be significantly less. In this paper we utilize a coupled climate/ice sheet model to demonstrate four points: (1) the open water solution can be simulated in the coupled model if the sea ice parameter is adjusted slightly; (2) a major reduction in ice volume from the open water/equatorial ice solution occurs at a CO2 level of about 4X present values—about two orders of magnitude less than required for exit from the “hard” snowball initial state; (3) additional CO2 increases are required to get fuller meltback of the ice; and (4) the open water solution exhibits hysteresis properties, such that climates with the same level of CO2 may evolve into either the snowball, open water, or a warmer world solution, with the trajectory depending on initial conditions.” [Full text]

Susceptibility of the early Earth to irreversible glaciation caused by carbon dioxide clouds – Caldeira & Kasting (1992) “Had such a transient global glaciation occurred in the distant past when solar luminosity was low, it might have been irreversible because of the formation of highly reflective CO2 clouds, similar to those encountered in climate simulations of early Mars. … In the ice-covered state little or no silicate rock would be exposed to weathering, so CO2 from metamorphic and mantle sources could accumulate in the atmosphere at a rate of ~8 x 1012 mol yr-1 (ref. 16). In less than 30 Myr, atmospheric pCO2 would build up to nearly 0.12 bar, and equatorial ice would become unstable (Fig. 2).” [Full text]

Posted in AGW evidence | 4 Comments »

Papers on stratospheric water vapor

Posted by Ari Jokimäki on May 15, 2010

This is a list of papers on stratospheric water vapor. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming – Solomon et al. (2010) “Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here we show that this acted to slow the rate of increase in global surface temperature over 2000–2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases. More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% as compared to estimates neglecting this change. These findings show that stratospheric water vapor is an important driver of decadal global surface climate change.” [Full text]

Simulation of secular trends in the middle atmosphere, 1950–2003 – Garcia et al. (2007) “We have used the Whole Atmosphere Community Climate Model to produce a small (three-member) ensemble of simulations of the period 1950–2003. … Calculated trends in water vapor, on the other hand, are not at all consistent with observations from either the HALOE satellite instrument or the Boulder, Colorado, hygrosonde data set. We show that such lack of agreement is actually to be expected because water vapor has various sources of low-frequency variability (heating due to volcanic eruptions, the quasi-biennial oscillation and El Niño–Southern Oscillation) that can confound the determination of secular trends.” [Full text]

Decreases in stratospheric water vapor after 2001: Links to changes in the tropical tropopause and the Brewer-Dobson circulation – Randel et al. (2006) “Time series of stratospheric water vapor measurements by satellites and balloons show persistent low values beginning in 2001. … The results paint a consistent picture of enhanced tropical upwelling after 2001, resulting in colder temperatures, lower water vapor and lower ozone near the tropical tropopause.” [Full text]

Control of interannual and longer-term variability of stratospheric water vapor – Fueglistaler & Haynes (2005) “We use trajectory calculations based on 40-year European Reanalysis (ERA-40) data to predict the water mixing ratio of air entering the stratosphere in the tropics ([H2O]e) and thereby to examine interannual and longer-term changes. [H2O]e is determined from the saturation mixing ratio of the coldest point during ascent from the troposphere to the stratosphere (the Lagrangian cold point). These model predictions for the time variation of [H2O]e agree very well with a broad range of measurements (Stratospheric Aerosol and Gas Experiment (SAGE) II, Halogen Occultation Experiment (HALOE), Microwave Limb Sounder (MLS), and Atmospheric Trace Molecule Spectroscopy (ATMOS)). … The combination of measurement uncertainties and relatively strong interannual variability with periods of several months to years, on the one hand, limits our ability to detect, attribute, and verify long-term trends and, on the other hand, raises the question as to whether the previously published estimates of long-term trends are too large.”

Interannual Changes of Stratospheric Water Vapor and Correlations with Tropical Tropopause Temperatures – Randel et al. (2004) “Interannual variations of stratospheric water vapor over 1992–2003 are studied using Halogen Occultation Experiment (HALOE) satellite measurements. Interannual anomalies in water vapor with an approximate 2-yr periodicity are evident near the tropical tropopause, and these propagate vertically and latitudinally with the mean stratospheric transport circulation (in a manner analogous to the seasonal “tape recorder”). Unusually low water vapor anomalies are observed in the lower stratosphere for 2001–03. These interannual anomalies are also observed in Arctic lower-stratospheric water vapor measurements by the Polar Ozone and Aerosol Measurement (POAM) satellite instrument during 1998–2003. Comparisons of the HALOE data with balloon measurements of lower-stratospheric water vapor at Boulder, Colorado (40°N), show partial agreement for seasonal and interannual changes during 1992–2002, but decadal increases observed in the balloon measurements for this period are not observed in HALOE data. Interannual changes in HALOE water vapor are well correlated with anomalies in tropical tropopause temperatures. The approximate 2-yr periodicity is attributable to tropopause temperature changes associated with the quasi-biennial oscillation and El Niño–Southern Oscillation.” [Full text]

Assessing the climate impact of trends in stratospheric water vapor – Forster & Shine (2002) “It is now apparent that observed increases in stratospheric water vapor may have contributed significantly to both stratospheric cooling and tropospheric warming over the last few decades. However, a recent study has suggested that our initial estimate of the climate impact may have overestimated both the radiative forcing and stratospheric cooling from these changes. We show that differences between the various estimates are not due to inherent problems with broadband and narrow-band radiation schemes but rather due to the different experimental setups, particularly the altitude of the water vapor change relative to the tropopause used in the radiative calculations. Furthermore, we show that if recent estimates for the observed water vapor trends are valid globally they could have contributed a radiative forcing of up to 0.29 Wm−2 and a lower-stratospheric cooling of more than 0.8 K over the past 20 years, with these values more than doubling if, as has been suggested, the trend has persisted for the last 40 years. This 40 year radiative forcing is roughly 75% of that due to carbon dioxide alone but, despite its high value, we find that the addition of this forcing into a simple model of climate change still gives global mean surface temperature trends which are consistent with observations.” [Full text]

Stratospheric water vapor increases over the past half‐century – Rosenlof et al. (2001) “Ten data sets covering the period 1954–2000 are analyzed to show a 1%/yr increase in stratospheric water vapor. The trend has persisted for at least 45 years, hence is unlikely the result of a single event, but rather indicative of long‐term climate change. A long‐term change in the transport of water vapor into the stratosphere is the most probable cause.”

Radiative forcing due to trends in stratospheric water vapour – Smith et al. (2001) “Trends derived from the latest version of Halogen Occultation Experiment (HALOE) data are used in a two‐dimensional atmospheric model to estimate their radiative effects over the last decade. The results show a stratospheric cooling in regions of H2O increase, of magnitude similar to that due to stratospheric ozone loss indicating a significant additional cause of observed stratospheric temperature decreases. Radiative forcings are derived and it is found that global average radiative forcing due to stratospheric water vapour changes probably lies in the range 0.12 to 0.20 Wm−2 decade−1. This could have more than compensated for the negative radiative forcing due to decadal ozone loss.” [Full text]

Climate and ozone response to increased stratospheric water vapor – Shindell (2001) “Stratospheric water vapor abundance affects ozone, surface climate, and stratospheric temperatures. From 30–50 km altitude, temperatures show global decreases of 3–6 K over recent decades. These may be a proxy for water vapor increases, as the GISS climate model reproduces these trends only when stratospheric water vapor is allowed to increase. Observations suggest that stratospheric water vapor is indeed increasing, though measurements are extremely limited in either spatial coverage or duration. Model results suggest that the observed changes may be part of a global, long‐term trend. Furthermore, the required water vapor change cannot be accounted for by increased stratospheric production, suggesting that climate change may be altering tropospheric input. The calculated water vapor increase contributes an additional ≈ 24% (≈ 0.2 W/m²) to the global warming from well‐mixed greenhouse gases over the past two decades. Observed ozone depletion is also better reproduced when destruction due to increased water vapor is included. If the trend continues, it could increase future global warming and impede stratospheric ozone recovery.”

The increase in stratospheric water vapor from balloonborne, frostpoint hygrometer measurements at Washington, D.C., and Boulder, Colorado – Oltmans et al. (2000) “Stratospheric water vapor concentrations measured at two midlatitude locations in the northern hemisphere show water vapor amounts have increased at a rate of 1–1.5% yr−1 (0.05–0.07 ppmv yr−1) for the past 35 years. At Washington, D.C., measurements were made from 1964–1976, and at Boulder, Colorado, observations began in 1980 and continue to the present. While these two data sets do not comprise a single time series, they individually show increases over their respective measurement periods. At Boulder the trends do not show strong seasonal differences; significant increases are found throughout the year in the altitude range 16–28 km. In winter these trends are significant down to about 13 km.” [Full text]

SPARC Assessment of Upper Tropospheric and Stratospheric Water Vapour – Kley et al. (2000) A report on the subject. [Full text available in the abstract page]

Stratospheric water vapour changes as a possible contributor to observed stratospheric cooling – Forster & Shine (1999) “The observed cooling of the lower stratosphere over the last two decades has been attributed, in previous studies, largely to a combination of stratospheric ozone loss and carbon dioxide increase, and as such it is meant to provide one of the best pieces of evidence for an anthropogenic cause to climate change. This study shows how increases in stratospheric water vapour, inferred from available observations, may be capable of causing as much of the observed cooling as ozone loss does; as the reasons for the stratospheric water vapour increase are neither fully understood nor well characterized, it shows that it remains uncertain whether the cooling of the lower stratosphere can yet be fully attributable to human influences. In addition, the changes in stratospheric water vapour may have contributed, since 1980, a radiative forcing which enhances that due to carbon dioxide alone by 40%.”

Mechanisms controlling water vapor in the lower stratosphere: “A tale of two stratospheres” – Dessler et al. (1995) “We present an analysis of the mechanisms controlling stratospheric water vapor based on in situ profiles made at 37.4°N and at altitudes up to 20 km. The stratosphere can be conveniently divided into two air masses: the overworld (potential temperature θ > 380 K) and the lowermost stratosphere (θ < 380). Our data support the canonical theory that air primarily enters the overworld by passing through the tropical tropopause. The low water vapor mixing ratios in the overworld, a few parts per million by volume (ppmv), are determined by the low temperatures encountered at the tropical tropopause, as well as oxidation of methane and molecular hydrogen. Air enters the lowermost stratosphere both by diabatically descending from the overworld across the 380-K potential temperature surface and by passing through the extratropical tropopause. Air parcels crossing the extratropical tropopause experience higher temperatures than air crossing the tropical tropopause, allowing higher water vapor in the lowermost stratosphere (tens of ppmv) than in the overworld. Our data are consistent with the pathway for air crossing the extratropical tropopause being isentropic advection from lower latitudes, although we cannot exclude contributions from other paths.” [Full text]

Overview of the Stratospheric Aerosol and Gas Experiment II Water Vapor Observations: Method, Validation, and Data Characteristics – Rind et al. (1993) “Water vapor observations obtained from the Stratospheric Aerosol and Gas Experiment II (SAGE II) solar occultation instrument for the troposphere and stratosphere are presented and compared with correlative in situ measurement techniques and other satellite data. … …minimum water vapor values of 2.5–3 ppmv in the tropical lower stratosphere, with lower values during northern hemisphere winter and spring; slowly increasing water vapor values with altitude in the stratosphere, reaching 5–6 ppmv or greater near the stratopause; extratropical values with minimum profile amounts occurring above the conventionally defined tropopause; and higher extratropical than tropical water vapor values throughout the stratosphere except in locations of possible polar stratospheric clouds.”

Stratospheric Water Vapor – Ellsaesser (1983) “We present a tutorial review of our understanding of stratospheric H2O and the processes controlling it. We attempt to synthesize a consistent global picture that requires rejection of a minimum of the conflicting observational data. As such, this synthesis is determined somewhat by the personal opinions and beliefs of the author. We note the paradoxes posed by currently available observational data and suggest ways they might be resolved.”

The distribution of water vapor in the stratosphere – Harries (1976) “This paper seeks to collect together and to assess the many measurements of stratospheric humidity which have been reported over the last 25 years, with a view to determining the average distribution of water vapor in the stratosphere and its variations in time and space. Variations with height, latitude, time, and season are considered. In addition, some consideration is given to the proper use of experimental values of humidity in discussions of the water budget and circulation of the stratosphere; it is emphasized that the considerable uncertainties which often exist in measured data often can preclude the drawing of quantitative conclusions.”

Water Vapor Distribution in the Stratosphere and High Troposphere – Mastenbrook (1968) “Fifty-one soundings with balloon-borne frost-point hygrometers provided measurements to a height of 94,000 ft of the vertical distribution of water vapor over Trinidad, West Indies, Washington, D.C., and Thule, Greenland, during 1964 and 1965, the International Years of the Quiet Sun. … The observed mixing ratios of the lower stratosphere to a height of 73,000 ft are for nearly all cases within the range of 1.2 × 10−6 – 3.3 × 10−6.” [Full text]

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Climate Physics Forums

Posted by Ari Jokimäki on May 12, 2010

This should be good: Climate Physics Forums. Owner of the site has done excellent work at physics forums on climate science issues. For discussing things, I prefer goold old forums over blogs, so I think I’ll be registering there myself.

Posted in General | 3 Comments »

Papers on AGW denialism

Posted by Ari Jokimäki on May 11, 2010

This is a list of papers on the AGW denialism. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Denialism: what is it and how should scientists respond? – Diethelm & McKee (2009) “HIV does not cause AIDS. The world was created in 4004 BCE. Smoking does not cause cancer. And if climate change is happening, it is nothing to do with man-made CO2 emissions. Few, if any, of the readers of this journal will believe any of these statements. Yet each can be found easily in the mass media. … Denialism is a process that employs some or all of five characteristic elements in a concerted way. The first is the identification of conspiracies. … The second is the use of fake experts. … The third characteristic is selectivity, drawing on isolated papers that challenge the dominant consensus or highlighting the flaws in the weakest papers among those that support it as a means of discrediting the entire field. … The fourth is the creation of impossible expectations of what research can deliver. … The fifth is the use of misrepresentation and logical fallacies.” [Full text]

How Climate Science Became a Victim of the Cold War – Oreskes & Conway (2008) The history of AGW denialism. “On first glance, it seems just plain weird that several of the same individuals—all retired physicists—were involved in denying that cancer causes smoking, that pollution causes acid rain, that CFCs destroy ozone, and that greenhouse gas emissions are causing global warming. But when you put these things together—tobacco regulation, the banning of CFCs, the delay of controls on CO2 emissions—then they do add up, summing to a radical free market ideology that opposes any action restricting the pursuit of market capitalism, no matter the justification.” [Full text]

From Chicken Little to Dr. Pangloss: William Nierenberg, Global Warming, and the Social Deconstruction of Scientific Knowledge – Oreskes et al. (2008) “This consensus was challenged, however, by a committee of the U.S. National Academy of Sciences, chaired by physicist William A. (Bill) Nierenberg, whose 1983 report arguably launched the climate change “debate.” Drawing on perspectives provided by two economists on his committee, Nierenberg reframed the question not as a matter of climate change per se, but as a matter of the human capacity to adapt to change when it came, a capacity, his report asserted, that was very great. Thus, while accepting the scientific conclusion that warming would occur, Nierenberg rejected the interpretation that it would be a problem. In later years, he would play a major role in political challenges to the scientific conclusions themselves. Reframing was Nierenberg’s first step on the road to the deconstruction of scientific knowledge of climate change.”

The organisation of denial: Conservative think tanks and environmental scepticism – Jacques et al. (2008) “Environmental scepticism denies the seriousness of environmental problems, and self-professed ‘sceptics’ claim to be unbiased analysts combating ‘junk science’. This study quantitatively analyses 141 English-language environmentally sceptical books published between 1972 and 2005. We find that over 92 per cent of these books, most published in the US since 1992, are linked to conservative think tanks (CTTs). Further, we analyse CTTs involved with environmental issues and find that 90 per cent of them espouse environmental scepticism. We conclude that scepticism is a tactic of an elite-driven counter-movement designed to combat environmentalism, and that the successful use of this tactic has contributed to the weakening of US commitment to environmental protection.” [Full text]

Scientific Certainty Argumentation Methods (SCAMs): Science and the Politics of Doubt – Freudenburg et al. (2008) “As noted by Trumbo (1996; see also Gelbspan 1997; Shanahan and Trumbo 1998), a strikingly high fraction of all media reports about “scientific” disputes over global warming, particularly during the 1990s, actually quoted only a small handful of skeptics—many of whom had been funded by affected industries and/or by politically conservative “Think Tanks” that proved to be especially adroit at publicizing the results of their studies (see McCright and Dunlap 2000, 2003; see also Fiore 1997; Krehely, House, and Kernan 2004). A number of the best-known skeptics were not even climate scientists. Even so, the ability to demand Scientific “Certainty” provided so much leverage that the critics received a disproportionate share of mass media attention, especially while the United States was debating the ratification of the Kyoto Accords for slowing global warming (see Fisher 2004).” [Full text]

The Rearguard of Modernity: Environmental Skepticism as a Struggle of Citizenship – Jacques (2006) “The article explains how political values determine what skeptics count as a problem. One such value described is “deep anthropocentrism,” or the attempt to split human society from non-human nature and reject ecology as a legitimate field of ethical concern. This bias frames what skeptics consider legitimate knowledge. The paper then argues that the contemporary conservative countermovement has marshaled environmental skepticism to function as a rearguard for a maladaptive set of core values that resist public efforts to address global environmental sustainability. As such, the paper normatively argues that environmental skepticism is a significant threat to efforts to achieve sustainability faced by human societies in a globalizing world.” [Full text]

Technocracy, Democracy, and U.S. Climate Politics: The Need for Demarcations – Lahsen (2005) “However, this study of U.S. climate politics reveals complexities and obstacles to the sort of democratized decision making envisioned by such theorists. Since the early 1990s, the U.S. public has been subjected to numerous media-driven campaigns to shape understandings of this widely perceived threat. Political interests have instigated an important part of these campaigns, frequently resorting to ethically problematic tactics to undermine attempts at policy action designed to avert or reduce the threat. The disproportionate in fluence of such interests suggests the need for a more level political playing field characterized by more equalized access to power and influence.” [Full text]

Defeating Kyoto: The Conservative Movement’s Impact on U.S. Climate Change Policy – McCright & Dunlap (2003) “In this article, we argue that a major reason the United States failed to ratify the Kyoto Protocol to ameliorate global warming is the opposition of the American conservative movement, a key segment of the anti-environmental counter-movement. We examine how the conservative movement mobilized between 1990 and 1997 to construct the “non-problematicity” of global warming. After we describe how conservative think tanks mobilized to challenge the global warming claims of mainstream climate science, we examine how these countermovement organizations aligned themselves with prominent American climate change skeptics known for their staunch criticism of mainstream climate research and their affiliations with the fossil fuels industry. We then examine how the efforts of these conservative think tanks were enhanced by the shift in the political opportunity structure created by the 1994 Republican takeover of Congress. This study demonstrates how a powerful countermovement effectively challenged the environmental community’s definition of global warming as a social problem and blocked the passage of any significant climate change policy.” [Full text]

Challenging Global Warming as a Social Problem: An Analysis of the Conservative Movement’s Counter-Claims – McCright & Dunlap (2000) “Utilizing recent work on framing processes in the social movements literature and claims-making from the social problems literature, this paper analyzes the counter-claims promoted by the conservative movement between 1990 and 1997 as it mobilized to challenge the legitimacy of global warming as a social problem. A thematic content analysis of publications circulated on the web sites of prominent conservative think tanks reveals three major counter-claims. First, the movement criticized the evidentiary basis of global warming as weak, if not entirely wrong. Second, the movement argued that global warming will have substantial benefits if it occurs. Third, the movement warned that proposed action to ameliorate global warming would do more harm than good. In short, the conservative movement asserted that, while the science of global warming appears to be growing more and more uncertain, the harmful effects of global warming policy are becoming increasingly certain. In order to better understand the controversy over global warming, future research should pay attention to the influence of the conservative movement by identifying the crucial roles of conservative foundations, conservative think tanks, and sympathetic “skeptic” scientists in undermining the growing scientific consensus over the reality of global warming.” [Full text]

Posted in Climate claims | 3 Comments »

Papers on halocarbon concentrations in the atmosphere

Posted by Ari Jokimäki on May 8, 2010

This is a list of papers on the atmospheric concentration of halocarbons. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (July 2, 2010): Laube et al. (2010) added.
UPDATE (August 15, 2010): Artuso et al. (2010) added.

Tropospheric halocompounds and nitrous oxide monitored at a remote site in the Mediterranean – Artuso et al. (2010) “Analysis of time series and trends of nitrous oxide (N2O) and halocompounds weekly monitored at the Mediterranean island of Lampedusa are discussed. … CFC-11 and CFC-12 time series displayed a decline consistent with their phase-out. Chlorofluorocarbons (CFCs) replacing compounds and SF6 exhibited an increasing temporal behaviour. The most rapid growth rate was recorded for HFC-134a with a value of 9.6 % yr−1. The industrial solvents CCl4 and CH3CCl3, banned by the Montreal Protocol, showed opposite trends. While CH3CCl3 reported an expected decay of -1.8 ppt yr−1, an increasing rate of 5.7 ppt yr−1 was recorded for CCl4 and it is probably related to its relatively long lifetime and persisting emissions. Chlorinated halomethanes showed seasonality with a maximum in early April and a minimum at the end of September. Halon-1301 and Halon-1211 displayed a decreasing trend consistent with industry emission estimates. An interspecies correlation analysis gave positive high correlations between HCFC-22 and HFC-134a (+0.84) highlighting the common extensive employment as refrigerants. Sharing sources inferred the high coupling between CH3Cl and CH3Br (+0.73) and between CHCl3 and CH2Cl2 (+0.77). A singular strong relationship (+0.55) between HFC-134a and CH3I suggested the influence of an unknown anthropogenic source of CH3I. Constraining of source and sink distribution was carried out by transport studies. Results were compared with the European Environment Agency (EEA) emission database. In contrast with the emission database results, our back trajectory analysis highlighted the release of large amounts of HFC-134a and SF6 from Eastern Europe. Observations also showed that African SF6 emissions may be considerable. Leakages from SF6 insulated electrical equipments located in the industrialized Northern African areas justify our observations.”

Accelerating growth of HFC-227ea (1,1,1,2,3,3,3-heptafluoropropane) in the atmosphere – Laube et al. (2010) “We report the first measurements of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), a substitute for ozone depleting compounds, in air samples originating from remote regions of the atmosphere and present evidence for its accelerating growth. Observed mixing ratios ranged from below 0.01 ppt in deep firn air to 0.59 ppt in the current northern mid-latitudinal upper troposphere. Firn air samples collected in Greenland were used to reconstruct a history of atmospheric abundance. Year-on-year increases were deduced, with acceleration in the growth rate from 0.029 ppt per year in 2000 to 0.056 ppt per year in 2007. Upper tropospheric air samples provide evidence for a continuing growth until late 2009. Furthermore we calculated a stratospheric lifetime of 370 years from measurements of air samples collected on board high altitude aircraft and balloons. Emission estimates were determined from the reconstructed atmospheric trend and suggest that current “bottom-up” estimates of global emissions for 2005 are too high by a factor of three.” [Full text]

Global carbon tetrachloride distributions obtained from the Atmospheric Chemistry Experiment (ACE) – Allen et al. (2009) “The first study of the global atmospheric distribution of carbon tetrachloride (CCl4), as a function of altitude and latitude, was performed using solar occultation measurements obtained by the Atmospheric Chemistry Experiment (ACE) mission using Fourier transform spectroscopy. A total of 8703 profile measurements were taken in the upper troposphere and lower stratosphere between February 2004 and August 2007. The zonal distribution of carbon tetrachloride displays a slight hemispheric asymmetry and decreasing concentration with increasing altitude at all latitudes. Maximum carbon tetrachloride concentrations are situated below 10 km in altitude with VMR (Volume Mixing Ratio) values of 100–130 ppt (parts per trillion). The highest concentrations are located about the Equator and at mid-latitudes, particularly for latitudes in heavily industrialised regions (20–45° N), with values declining towards the poles. Global distributions obtained from ACE were compared with predictions from three chemistry transport models showing good agreement in terms of the vertical gradient despite an overall offset. The ACE dataset gives unique global and temporal coverage of carbon tetrachloride and its transport through the atmosphere. An estimated lifetime for carbon tetrachloride of 34±5 years was determined through correlation with CFC-11.” [Full text]

A 2000 year atmospheric history of methyl chloride from a South Pole ice core: Evidence for climate-controlled variability – Williams et al. (2007) ” This study presents CH3Cl measurements in air extracted from a 300 m ice core from South Pole, Antarctica, covering the time period from 160 BC to 1860 AD. The data exhibit an increasing trend of 3 ppt (parts per trillion) over 100 years and higher frequency variations that appear to be climate-related. CH3Cl levels were elevated from 900–1300 AD by about 50 ppt relative to the previous 1000 years, coincident with the warm Medieval Climate Anomaly (MCA). CH3Cl levels decreased to a minimum during the Little Ice Age cooling (1650–1800 AD), before rising again to the modern atmospheric level of 550 ppt. These variations most likely reflect changes in tropical and subtropical conditions, and raise the possibility that a warmer future climate may result in higher tropospheric CH3Cl levels.” [Full text]

Ambient halocarbon mixing ratios in 45 Chinese cities – Barletta et al. (2006) “During this study 158 whole air samples were collected in 45 Chinese cities in January and February 2001. The spatial distribution of different classes of halocarbons in the Chinese urban atmosphere, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), Halon-1211, and other chlorinated compounds is presented and discussed. Most of these compounds were enhanced compared to background levels. However, the mean enhancement of CFCs was relatively small, with CFC-12 and CFC-11 increases of 6% (range 1–31%) and 10% (range 2–89%), respectively, with respect to the global background. On the contrary, strongly enhanced levels of CFC replacement compounds and halogenated compounds used as solvents were measured. The average Halon-1211 concentration exceeded the background of 4.3 pptv by 75% and was higher than 10 pptv in several cities. Methyl chloride mixing ratios were also strongly elevated (78% higher than background levels), which is likely related to the widespread use of coal and biofuel in China.” [Full text]

Trends of halon gases in polar firn air: implications for their emission distributions – Reeves et al. (2005) “Four halons (H-1301, H-1211, H-2402 and H-1202) have been measured in air samples collected from polar firn from Dome Concordia (Dome C), Antarctica, from Devon Island, Canada and the North Greenland Ice Core Project (NGRIP) site, Greenland. H-2402 and H-1202 are reported for the first time in firn air. The depth profiles show the concentrations of all four halons to be close to zero (i.e. below the detection limit of 0.001 ppt) at the base of the firn thus demonstrating their entirely anthropogenic origin. This is the first evidence of this for H-2402 and H-1202.” [Full text]

Rapid growth of hydrofluorocarbon 134a and hydrochlorofluorocarbons 141b, 142b, and 22 from Advanced Global Atmospheric Gases Experiment (AGAGE) observations at Cape Grim, Tasmania, and Mace Head, Ireland – O’Doherty et al. (2004) “An update of in situ Advanced Global Atmospheric Gases Experiment (AGAGE) hydrofluorocarbon (HFC)/hydrochlorofluorocarbon (HCFC) measurements made at Mace Head, Ireland, and Cape Grim, Tasmania, from 1998 to 2002 are reported. HCFC-142b, HCFC-141b, HCFC-22 and HFC-134a show continued rapid growth in the atmosphere at mean rates of 1.1, 1.6, 6.0, and 3.4 ppt/year, respectively.”

Analyses of firn gas samples from Dronning Maud Land, Antarctica: Study of nonmethane hydrocarbons and methyl chloride – Kaspers et al. (2004) “Firn air was sampled on the Antarctic plateau in Dronning Maud Land (DML), during the Norwegian Antarctic Research Expedition (NARE) 2000/2001. In this paper, we describe the analyses for methyl chloride and nonmethane hydrocarbons (NMHCs) in these firn air samples. For the first time, the NMHCs ethane, propane, and acetylene have been measured in Antarctic firn air, and concentration profiles for these gases have been derived. A one-dimensional numerical firn air diffusion model was used to interpret the measured profiles and to derive atmospheric concentrations as a function of time. The atmospheric trends we derived for the NMHC and methyl chloride at DML cover the period from 1975 to 2000. Methyl chloride shows a decreasing trend of 1.2 ± 0.6 ppt per year (annual mean concentration 548 ± 32 ppt). For ethane we found an increasing trend of 1.6 ± 0.6 ppt per year (annual mean concentration 241 ± 12 ppt). The concentrations of propane and acetylene appear to be constant over the period 1975–2000, with annual mean concentrations of 30 ± 4 ppt for propane and 24 ± 2 ppt for acetylene.” [Full text]

Atmospheric variability of methyl chloride during the last 300 years from an Antarctic ice core and firn air – Aydin et al. (2004) “Measurements of methyl chloride (CH3Cl) in Antarctic polar ice and firn air are used to describe the variability of atmospheric CH3Cl during the past 300 years. Firn air results from South Pole and Siple Dome suggest that the atmospheric abundance of CH3Cl increased by about 10% in the 50 years prior to 1990. Ice core measurements from Siple Dome provide evidence for a cyclic natural variability on the order of 10%, with a period of about 110 years in phase with the 20th century rise inferred from firn air. Thus, the CH3Cl increase measured in firn air may largely be a result of natural processes, which may continue to affect the atmospheric CH3Cl burden during the 21st century.” [Full text]

Halocarbons and other Atmospheric Trace Species – Thompson et al. (2004) “Sustained measurement programs within HATS are based upon in situ and flask measurements of the atmosphere from the five CMDL baseline observatories and ten cooperative stations… … Most major CFCs and CCl4 are decreasing at a slow rate, while CH3CCl3 has decreased in the troposphere to mixing ratio levels below 25 parts per trillion (ppt, 10-12).” [Full text]

Methyl bromide in preindustrial air: Measurements from an Antarctic ice core – Saltzman et al. (2004) “This paper presents the first ice core measurements of methyl bromide (CH3Br). Samples from a shallow Antarctic ice core (Siple Dome, West Antarctica), ranging in mean gas dates from 1671 to 1942, had a mean CH3Br mixing ratio of 5.8 ppt. These results extend the existing historical record derived from air and Antarctic firn air to about 350 years before present. Model simulations illustrate that the ice core results are consistent with estimates of the impact of anthropogenic activity (fumigation, combustion, and biomass burning) on the atmospheric CH3Br burden, given the large current uncertainties in the modern atmospheric CH3Br budget. A preindustrial scenario assuming no fumigation, no combustion, and a 75% reduction in biomass-burning sources yields a Southern Hemisphere mean mixing ratio of 5.8 ppt, in good agreement with the ice core results. There is a significant imbalance between the known CH3Br sources and sinks in the modern atmospheric CH3Br budget. The ice core data do not sufficiently constrain the model to determine how much of the “unknown source” was present in the preindustrial budget. The results do indicate that most of the southern hemispheric component of this “unknown source” is not anthropogenic.” [Full text]

Regional Sources of Methyl Chloride, Chloroform and Dichloromethane Identified from AGAGE Observations at Cape Grim, Tasmania, 1998–2000 – Cox et al. (2003) “We report two years of in situ observations of these species from the AGAGE (Advanced Global Atmospheric Gas Experiment) program at Cape Grim, Tasmania (41° S, 145° E). The average background levels of CH3Cl, CHCl3 and CH2Cl2 during 1998–2000 were 551± 8, 6.3± 0.2 and 8.9± 0.2 ppt (dry air mole fractions expressed in parts per 1012) respectively, with a two-year average amplitude of the seasonal cycles in background air of 25, 1.1 and 1.5 ppt respectively.”

Large-scale latitudinal and vertical distributions of NMHCs and selected halocarbons in the troposphere over the Pacific Ocean during the March-April 1999 Pacific Exploratory Mission (PEM-Tropics B) – Blake et al. (2001) “Nonmethane hydrocarbons (NMHCs) and selected halocarbons were measured in whole air samples collected over the remote Pacific Ocean during NASA’s Global Tropospheric Experiment (GTE) Pacific Exploratory Mission-Tropics B (PEM-Tropics B) in March and early April 1999.” [Full text]

A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE – Prinn et al. (2000) “We describe in detail the instrumentation and calibrations used in the Atmospheric Lifetime Experiment (ALE), the Global Atmospheric Gases Experiment (GAGE), and the Advanced Global Atmospheric Gases Experiment (AGAGE) and present a history of the majority of the anthropogenic ozone-depleting and climate-forcing gases in air based on these experiments. … Some specific conclusions are as follows: (1) International compliance with the Montreal Protocol is so far resulting in chlorofluorocarbon and chlorocarbon mole fractions comparable to target levels; (2) mole fractions of total chlorine contained in long-lived halocarbons (CCl2F2, CCl3F, CH3CCl3, CCl4, CHClF2, CCl2FCClF2, CH3Cl, CH2Cl2, CHCl3, CCl2=CCl2) in the lower troposphere reached maximum values of about 3.6 ppb in 1993 and are beginning to slowly decrease in the global lower atmosphere; (3) the chlorofluorocarbons have atmospheric lifetimes consistent with destruction in the stratosphere being their principal removal mechanism; (4) multiannual variations in chlorofluorocarbon and chlorocarbon emissions deduced from ALE/GAGE/AGAGE data are consistent approximately with variations estimated independently from industrial production and sales data where available (CCl2F2 (CFC-12) and CCl2FCClF2 (CFC-113) show the greatest discrepancies);” [Full text]

A record of atmospheric halocarbons during the twentieth century from polar firn air – Butler et al. (1999) “Measurements of trace gases in air trapped in polar firn (unconsolidated snow) demonstrate that natural sources of chlorofluorocarbons, halons, persistent chlorocarbon solvents and sulphur hexafluoride to the atmosphere are minimal or non-existent. Atmospheric concentrations of these gases, reconstructed back to the late nineteenth century, are consistent with atmospheric histories derived from anthropogenic emission rates and known atmospheric lifetimes. The measurements confirm the predominance of human activity in the atmospheric budget of organic chlorine, and allow the estimation of atmospheric histories of halogenated gases of combined anthropogenic and natural origin. The pre-twentieth-century burden of methyl chloride was close to that at present, while the burden of methyl bromide was probably over half of today’s value.” [Full text]

Present and future trends in the atmospheric burden of ozone-depleting halogens – Montzka et al. (1999) “Our measurements of atmospheric concentrations of the persistent, anthropogenic chemicals that account for most ozone-depleting halogens in today’s stratosphere show that the decline stems predominantly from the decrease in the atmospheric load of trichloroethane (CH3CCl3), a previously common cleaning solvent.”

Growth of fluoroform (CHF3, HFC‐23) in the background atmosphere – Oram et al. (1998) “We have found that present‐day HFC‐23 concentrations (c. 11 pptv in late 1995) exceed those of SF6 by a factor of three. Concentrations have steadily increased in the atmosphere since at least 1978, and are continuing to do so at a present rate of 5% per year. Furthermore, HFC‐23 appears to be long‐lived in the atmosphere, with a stratospheric lifetime of at least 1000 years, and a modelled tropospheric lifetime of 230 years.”

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General notes on this site

Posted by Ari Jokimäki on May 7, 2010

Things have been a bit slow here recently. I have been putting some effort to the Finnish blog we have – writing some brief news pieces on new research and things like that. But I think I also have to pay attention to this site little more now.

Paperlists will continue, but I will explore some new issues with them, while also continuing with the observation oriented climate science lists. The new issues will/might be:

- Global warming effects. Gail Zawacki suggested this some time ago. I have already added this section to the paperlist index, but I’ll have to see which lists should be moved to the new section from the temperature indicators section.

- Future climate predictions. Barry suggested this and I already added this also. There’s even one list already (the 1970′s predictions -list).

- Energy issues (and perhaps adaptation issues). There has been some discussion on the integral fast reactors (IFR) recently in Finland, so I thought that it would be good to see the research on the issues like that.

I also need to look at the division of the papers I have there now. Recently I added the “atmospheric composition” section but I need to see if there’s some better ways to divide these things to subsections.

You can use this thread to suggest some other subject areas and paperlist subjects for the areas I have mentioned above.

So nothing major, just some minor adjustments here and there.

By the way, recently John Cook started a new argument link resource. I have been adding some links there, especially to the peer-review part. I hope you will too participate to building this fine resource.

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