Ken MacClune - Academia.edu (original) (raw)
Papers by Ken MacClune
Climate and Development, 2015
International Journal of Disaster Resilience in the Built Environment, 2015
ABSTRACT Purpose – This paper aims to fill a conceptual gap in the understanding of rapidly chang... more ABSTRACT Purpose – This paper aims to fill a conceptual gap in the understanding of rapidly changing characteristics of local risk, addressing how the notion of the local might be reframed, and how opportunities for multi-scale interventions for disaster risk reduction might be identified. Design/methodology/approach – The paper illustrates the significance of the systems and services on which urbanization depends – water, food, energy, transport and communications – to consider the cascading impacts at multiple scales often beyond the administrative boundaries of cities, and how vulnerabilities and risks are distributed unevenly across different groups of people. Findings – The process of rapid urbanization in the Mekong Region represents a fundamental transformation of ecological landscapes, resource flows, livelihoods and demographics. In addition to the location of urbanization, it is these transformative processes and the critical dependence on inter-linked systems that shape the overall picture of urban disaster and climate vulnerability. Research limitations/implications – By drawing on research and practical experience in two of the most rapidly urbanizing countries in the world, Thailand and Vietnam, the approach and findings have implications for understanding global patterns of urbanization. Practical implications – The paper contributes to considering practical actions whether in terms of policy or project implementation for both the assessment of disaster and climate risk, and for actions to reduce vulnerability and promote resilience. Social implications – The paper draws largely from social science perspectives, highlighting the dynamism of social organization in urbanizing contexts, and the implications for risk and vulnerability. Originality/value – The paper draws on original research in Thailand and Vietnam that takes urbanization as the starting point for assessing vulnerability and risk.
Global Biogeochem Cycle, 2006
Disaster Risk Reduction, 2016
1] We describe the development of an automated gas chromatography-isotope ratio mass spectrometry... more 1] We describe the development of an automated gas chromatography-isotope ratio mass spectrometry (GC-IRMS) system capable of measuring the carbon isotopic composition of atmospheric methane (d 13 CH 4 ) with a precision of better than 0.1%. The system requires 200 mL of air and completes a single analysis in 15 min. The combination of small sample size, fast analysis time, and high precision has allowed us to measure background variations in atmospheric d 13 CH 4 through the NOAA Climate Monitoring and Diagnostics Laboratory Cooperative Air Sampling Network. We then present a record of d 13 CH 4 obtained from six surface sites of the network between January 1998 and December 1999. The sites are Barrow, Alaska (71°N); Niwot Ridge, Colorado (40°N); Mauna Loa, Hawaii (20°N); American Samoa (14°S); Cape Grim, Tasmania (41°S); and the South Pole (90°S). For the years 1998 and 1999, the globally averaged surface d 13 C value was À47.1%, and the average difference between Barrow and the South Pole was 0.6%. Consistent seasonal variations were seen only in the Northern Hemisphere, especially at Barrow, where the average amplitude was 0.5%. Seasonal variations in 1998, however, were evident at all sites, the cause of which is unknown. We also use a two-box model to examine the extent to which annual average d 13 C and CH 4 mole fraction measurements can constrain broad categories of source emissions. We find that the biggest sources of error are not the atmospheric d 13 C measurements but instead the radiocarbon-derived fossil fuel emission estimates, rate coefficients for methane destruction, and isotopic ratios of source emissions.
Methane is the second most potent greenhouse gas and is responsible for nearly 20% of the enhance... more Methane is the second most potent greenhouse gas and is responsible for nearly 20% of the enhanced greenhouse effect. The most common means of estimating the source budget are through inverse modeling techniques using variations of the atmospheric concentration in space and time and by extrapolation of localized source flux measurements to a global scale. Yet, due to the wide array of methane sources and a relative paucity of measurements, its budget is not well constrained. Carbon-13 measurements offer a means to help clarify the methane budget because different groups of methane sources have distinct isotopic signatures. For example, the isotopic ratio of microbially produced methane is around -60 per mil, while that originating from biomass burning is around -25 per mil. Since 1998, in co-operation with NOAA/CMDL, delta 13C-CH4 has been measured at the University of Colorado's Stable Isotope Lab from samples drawn on a weekly basis from select sites of the NOAA/CMDL Cooperati...
The Greater Mekong Subregion (GMS), which has historically been an agricultural centre, is rapidl... more The Greater Mekong Subregion (GMS), which has historically been an agricultural centre, is rapidly urbanizing at a scale never seen before. This process is set to intensify with the ASEAN Economic Community (AEC) coming into place in 2015 linking urban, commercial and industrial centers across the GMS. The GMS has been identified as a region particularly vulnerable to the effects of climate change. Much of the urbanization that is occurring in the GMS is happening in places that are already hazardous, particularly along coasts, rivers, and deltas that are already vulnerable to flooding and extreme weather events. Urbanization can exacerbate climate change risks through land-use changes, alterations to natural hydrology, Urban Heat Island (UHI) effects, with coastal cities face the additional challenge of sea level rise. Urbanization also adds to vulnerability through changes in the impacts of smaller hazard events by altering the behavior of people and increasing their reliance on h...
Perceptions about partners’ abilities to find, interpret, and utilize climate information in the ... more Perceptions about partners’ abilities to find, interpret, and utilize climate information in the various ACCCRN contexts is influenced by an individual’s or organization’s understanding of climate information and conceptions toward how it should be used. All ACCCRN partners were presented with a questionnaire designed to elicit their perceptions on: 1) the process by which climate information was utilized in each country and/or city context; 2) the evolution in their understanding of how climate information should versus could have been used at various points in the project; and 3) their recommendations for what they think should be done differently in accessing, interpreting, translating, communicating and using climate information at various stages of the adaptation process. I have tried to supplement perceptions from the questionnaires with my (and other ISET staff ’s) experiences of working with various partners, notes from the shared learning dialogues/workshops, and correspond...
The broad warming observed over the past decades across South Asia is likely to continue into the... more The broad warming observed over the past decades across South Asia is likely to continue into the future. Multi-model projections indicate that mean temperature increases over the area are expected in the range of 2–3°C by 2050 compared to the late 20th century. Human perceived heat—the combination of temperatures with humidity—as expressed through the heat-index is likely to rise by significantly more, possibly 4–7°C, over the same time span. While heat is already an issue for the large fraction of the poor population that suffers from a lack of appropriate shelter and access to basic water and energy, the rapid rise in heat is likely to become an inescapable challenge. As the average daily heat-index reaches human body temperature, lack of cooling will significantly impact economic productivity and severely heighten health risks. Although South Asian populations have learned to cope with episodes of heat, future heat events will become relentless as the number of days of excessive...
International Journal of Disaster Resilience in the Built Environment, 2015
ABSTRACT Purpose – This paper aims to fill a conceptual gap in the understanding of rapidly chang... more ABSTRACT Purpose – This paper aims to fill a conceptual gap in the understanding of rapidly changing characteristics of local risk, addressing how the notion of the local might be reframed, and how opportunities for multi-scale interventions for disaster risk reduction might be identified. Design/methodology/approach – The paper illustrates the significance of the systems and services on which urbanization depends – water, food, energy, transport and communications – to consider the cascading impacts at multiple scales often beyond the administrative boundaries of cities, and how vulnerabilities and risks are distributed unevenly across different groups of people. Findings – The process of rapid urbanization in the Mekong Region represents a fundamental transformation of ecological landscapes, resource flows, livelihoods and demographics. In addition to the location of urbanization, it is these transformative processes and the critical dependence on inter-linked systems that shape the overall picture of urban disaster and climate vulnerability. Research limitations/implications – By drawing on research and practical experience in two of the most rapidly urbanizing countries in the world, Thailand and Vietnam, the approach and findings have implications for understanding global patterns of urbanization. Practical implications – The paper contributes to considering practical actions whether in terms of policy or project implementation for both the assessment of disaster and climate risk, and for actions to reduce vulnerability and promote resilience. Social implications – The paper draws largely from social science perspectives, highlighting the dynamism of social organization in urbanizing contexts, and the implications for risk and vulnerability. Originality/value – The paper draws on original research in Thailand and Vietnam that takes urbanization as the starting point for assessing vulnerability and risk.
Journal of Geophysical Research, 2007
1] In this study, individual precipitation samples, collected over 2 years at stations in differe... more 1] In this study, individual precipitation samples, collected over 2 years at stations in different climatic regions of west China (Tibetan Plateau region, Tianshan region, and Altay) were analyzed for the stable isotopes of precipitation to improve our understanding of how vapor transport impacts the modern stable isotopic distribution. Our results identify regional patterns in both d 18 O and deuterium excess (D excess, defined as dD -8d 18 O), and in particular we have identified the northward maximum extent of the southwest monsoon over the Tibetan Plateau. This demarcation is also the boundary for the fractionation effect of temperature on stable isotopes in precipitation. The patterns we have identified are as follows: In the southern Tibetan Plateau, along the southern slope of the Himalayas, our results show a distinct seasonality for both d 18 O and D excess as a result of the shift of summer monsoon moisture and winter westerly moisture transport. The signals of d 18 O in the western Tibetan Plateau reveal that the region receives southwest monsoonal moisture. In the east of the plateau, stable isotopic variation shows alternation between monsoon intrusion and recycling of northern moisture. (2) In contrast, in Tianshan there is an apparent ''temperature effect'' in d 18 O, with enriched values occurring in summer and depleted values occurring in winter. Seasonal D excess values, opposite to those observed in the southern Tibetan Plateau, are controlled by differing seasonal evaporation conditions. (3) In Altay, the most northern mountain region, the seasonal d 18 O shows the same variation with that in Tianshan region. However, D excess shows no apparent seasonal variation.
Journal of Geophysical Research, 2006
1] Many have made efforts to clarify the climatic significance of stable isotopic variations in i... more 1] Many have made efforts to clarify the climatic significance of stable isotopic variations in ice cores around central Asia through the study of stable isotopes in present-day precipitation. A new shallow ice core from Muztagata, in the eastern Pamirs, allows for a detailed comparison of annual d 18 O variation with local meteorological data as well as with global air temperature variations. On the basis of a comparison of seasonal fluctuations of d 18 O in the local precipitation, the 41.6-m ice core drilled at 7010 m provides a record of about one-half century. The annual fluctuations of d 18 O in this ice core are in good agreement (correlation coefficient of 0.67) with the annual air temperature changes at the nearby meteorological station Taxkorgen, indicating that the isotopic record from this ice core is a reliable temperature trend indicator. The most important discovery from the d 18 O variation of this ice core is a rapid warming trend in the 1990s, which is consistent with a general global warming trend over this time period. This recent rapid warming at higher elevations in this area has led to the quick retreat of alpine glaciers.
Journal of Geophysical Research, 2002
1] We describe the development of an automated gas chromatography-isotope ratio mass spectrometry... more 1] We describe the development of an automated gas chromatography-isotope ratio mass spectrometry (GC-IRMS) system capable of measuring the carbon isotopic composition of atmospheric methane (d 13 CH 4 ) with a precision of better than 0.1%. The system requires 200 mL of air and completes a single analysis in 15 min. The combination of small sample size, fast analysis time, and high precision has allowed us to measure background variations in atmospheric d 13 CH 4 through the NOAA Climate Monitoring and Diagnostics Laboratory Cooperative Air Sampling Network. We then present a record of d 13 CH 4 obtained from six surface sites of the network between January 1998 and December 1999. The sites are Barrow, Alaska (71°N); Niwot Ridge, Colorado (40°N); Mauna Loa, Hawaii (20°N); American Samoa (14°S); Cape Grim, Tasmania (41°S); and the South Pole (90°S). For the years 1998 and 1999, the globally averaged surface d 13 C value was À47.1%, and the average difference between Barrow and the South Pole was 0.6%. Consistent seasonal variations were seen only in the Northern Hemisphere, especially at Barrow, where the average amplitude was 0.5%. Seasonal variations in 1998, however, were evident at all sites, the cause of which is unknown. We also use a two-box model to examine the extent to which annual average d 13 C and CH 4 mole fraction measurements can constrain broad categories of source emissions. We find that the biggest sources of error are not the atmospheric d 13 C measurements but instead the radiocarbon-derived fossil fuel emission estimates, rate coefficients for methane destruction, and isotopic ratios of source emissions.
Global Biogeochemical Cycles, 2005
1] This paper describes background characteristics of atmospheric CO 2 and stable isotopic ratios... more 1] This paper describes background characteristics of atmospheric CO 2 and stable isotopic ratios (d 13 C and d 18 O) as well as their possible drivers at Waliguan Baseline Observatory (WLG) (36°17 0 N, 100°54 0 E, 3816 m above sea level) in the inland plateau of western China. The study is based on observational CO 2 data (NOAA Climate Monitoring and Diagnostics Laboratory discrete and WLG continuous measurements) obtained at WLG for the period from May 1991 to December 2002. Over this period the change in monthly means is +16ppmforCO2,+16 ppm for CO 2 , +16ppmforCO2,À0.2% for d 13 C, and Aˋ0.5À0.5% for d 18 O. The overall increase of CO 2 and subsequent decline of d 13 C, with a Dd 13 C/DCO 2 ratio (À0.011 ± 0.105) % ppm À1 at WLG, reflect the persistent worldwide influence of fossil fuel emissions. The negative secular trend of d 18 O at WLG is probably due to vigorous 18 O exchange with soils in the Northern Hemisphere (NH) and conversion from C 3 to C 4 plants via land use change. The CO 2 , d 13 C, and d 18 O mean annual cycles with peak-to-peak annual amplitudes of Aˋ0.510.5 ppm, 0.4990.499 %, and 0.4990.819%, respectively, at WLG show typical middle-to-high NH continental features that correspond to the seasonal cycle of the terrestrial biosphere. The significant CO 2 and d 13 C interannual variability at WLG is very likely caused by worldwide climate anomalies and associated regional fluctuation in biospheric CO 2 uptake in the Asian inland plateau as well as long-range air mass transport. The results of this study help to provide a basic understanding of the individual sources and sinks of carbon in this area and help us to better address the role of the Asian inland terrestrial biosphere in the global carbon cycle.
Climate and Development, 2015
International Journal of Disaster Resilience in the Built Environment, 2015
ABSTRACT Purpose – This paper aims to fill a conceptual gap in the understanding of rapidly chang... more ABSTRACT Purpose – This paper aims to fill a conceptual gap in the understanding of rapidly changing characteristics of local risk, addressing how the notion of the local might be reframed, and how opportunities for multi-scale interventions for disaster risk reduction might be identified. Design/methodology/approach – The paper illustrates the significance of the systems and services on which urbanization depends – water, food, energy, transport and communications – to consider the cascading impacts at multiple scales often beyond the administrative boundaries of cities, and how vulnerabilities and risks are distributed unevenly across different groups of people. Findings – The process of rapid urbanization in the Mekong Region represents a fundamental transformation of ecological landscapes, resource flows, livelihoods and demographics. In addition to the location of urbanization, it is these transformative processes and the critical dependence on inter-linked systems that shape the overall picture of urban disaster and climate vulnerability. Research limitations/implications – By drawing on research and practical experience in two of the most rapidly urbanizing countries in the world, Thailand and Vietnam, the approach and findings have implications for understanding global patterns of urbanization. Practical implications – The paper contributes to considering practical actions whether in terms of policy or project implementation for both the assessment of disaster and climate risk, and for actions to reduce vulnerability and promote resilience. Social implications – The paper draws largely from social science perspectives, highlighting the dynamism of social organization in urbanizing contexts, and the implications for risk and vulnerability. Originality/value – The paper draws on original research in Thailand and Vietnam that takes urbanization as the starting point for assessing vulnerability and risk.
Global Biogeochem Cycle, 2006
Disaster Risk Reduction, 2016
1] We describe the development of an automated gas chromatography-isotope ratio mass spectrometry... more 1] We describe the development of an automated gas chromatography-isotope ratio mass spectrometry (GC-IRMS) system capable of measuring the carbon isotopic composition of atmospheric methane (d 13 CH 4 ) with a precision of better than 0.1%. The system requires 200 mL of air and completes a single analysis in 15 min. The combination of small sample size, fast analysis time, and high precision has allowed us to measure background variations in atmospheric d 13 CH 4 through the NOAA Climate Monitoring and Diagnostics Laboratory Cooperative Air Sampling Network. We then present a record of d 13 CH 4 obtained from six surface sites of the network between January 1998 and December 1999. The sites are Barrow, Alaska (71°N); Niwot Ridge, Colorado (40°N); Mauna Loa, Hawaii (20°N); American Samoa (14°S); Cape Grim, Tasmania (41°S); and the South Pole (90°S). For the years 1998 and 1999, the globally averaged surface d 13 C value was À47.1%, and the average difference between Barrow and the South Pole was 0.6%. Consistent seasonal variations were seen only in the Northern Hemisphere, especially at Barrow, where the average amplitude was 0.5%. Seasonal variations in 1998, however, were evident at all sites, the cause of which is unknown. We also use a two-box model to examine the extent to which annual average d 13 C and CH 4 mole fraction measurements can constrain broad categories of source emissions. We find that the biggest sources of error are not the atmospheric d 13 C measurements but instead the radiocarbon-derived fossil fuel emission estimates, rate coefficients for methane destruction, and isotopic ratios of source emissions.
Methane is the second most potent greenhouse gas and is responsible for nearly 20% of the enhance... more Methane is the second most potent greenhouse gas and is responsible for nearly 20% of the enhanced greenhouse effect. The most common means of estimating the source budget are through inverse modeling techniques using variations of the atmospheric concentration in space and time and by extrapolation of localized source flux measurements to a global scale. Yet, due to the wide array of methane sources and a relative paucity of measurements, its budget is not well constrained. Carbon-13 measurements offer a means to help clarify the methane budget because different groups of methane sources have distinct isotopic signatures. For example, the isotopic ratio of microbially produced methane is around -60 per mil, while that originating from biomass burning is around -25 per mil. Since 1998, in co-operation with NOAA/CMDL, delta 13C-CH4 has been measured at the University of Colorado's Stable Isotope Lab from samples drawn on a weekly basis from select sites of the NOAA/CMDL Cooperati...
The Greater Mekong Subregion (GMS), which has historically been an agricultural centre, is rapidl... more The Greater Mekong Subregion (GMS), which has historically been an agricultural centre, is rapidly urbanizing at a scale never seen before. This process is set to intensify with the ASEAN Economic Community (AEC) coming into place in 2015 linking urban, commercial and industrial centers across the GMS. The GMS has been identified as a region particularly vulnerable to the effects of climate change. Much of the urbanization that is occurring in the GMS is happening in places that are already hazardous, particularly along coasts, rivers, and deltas that are already vulnerable to flooding and extreme weather events. Urbanization can exacerbate climate change risks through land-use changes, alterations to natural hydrology, Urban Heat Island (UHI) effects, with coastal cities face the additional challenge of sea level rise. Urbanization also adds to vulnerability through changes in the impacts of smaller hazard events by altering the behavior of people and increasing their reliance on h...
Perceptions about partners’ abilities to find, interpret, and utilize climate information in the ... more Perceptions about partners’ abilities to find, interpret, and utilize climate information in the various ACCCRN contexts is influenced by an individual’s or organization’s understanding of climate information and conceptions toward how it should be used. All ACCCRN partners were presented with a questionnaire designed to elicit their perceptions on: 1) the process by which climate information was utilized in each country and/or city context; 2) the evolution in their understanding of how climate information should versus could have been used at various points in the project; and 3) their recommendations for what they think should be done differently in accessing, interpreting, translating, communicating and using climate information at various stages of the adaptation process. I have tried to supplement perceptions from the questionnaires with my (and other ISET staff ’s) experiences of working with various partners, notes from the shared learning dialogues/workshops, and correspond...
The broad warming observed over the past decades across South Asia is likely to continue into the... more The broad warming observed over the past decades across South Asia is likely to continue into the future. Multi-model projections indicate that mean temperature increases over the area are expected in the range of 2–3°C by 2050 compared to the late 20th century. Human perceived heat—the combination of temperatures with humidity—as expressed through the heat-index is likely to rise by significantly more, possibly 4–7°C, over the same time span. While heat is already an issue for the large fraction of the poor population that suffers from a lack of appropriate shelter and access to basic water and energy, the rapid rise in heat is likely to become an inescapable challenge. As the average daily heat-index reaches human body temperature, lack of cooling will significantly impact economic productivity and severely heighten health risks. Although South Asian populations have learned to cope with episodes of heat, future heat events will become relentless as the number of days of excessive...
International Journal of Disaster Resilience in the Built Environment, 2015
ABSTRACT Purpose – This paper aims to fill a conceptual gap in the understanding of rapidly chang... more ABSTRACT Purpose – This paper aims to fill a conceptual gap in the understanding of rapidly changing characteristics of local risk, addressing how the notion of the local might be reframed, and how opportunities for multi-scale interventions for disaster risk reduction might be identified. Design/methodology/approach – The paper illustrates the significance of the systems and services on which urbanization depends – water, food, energy, transport and communications – to consider the cascading impacts at multiple scales often beyond the administrative boundaries of cities, and how vulnerabilities and risks are distributed unevenly across different groups of people. Findings – The process of rapid urbanization in the Mekong Region represents a fundamental transformation of ecological landscapes, resource flows, livelihoods and demographics. In addition to the location of urbanization, it is these transformative processes and the critical dependence on inter-linked systems that shape the overall picture of urban disaster and climate vulnerability. Research limitations/implications – By drawing on research and practical experience in two of the most rapidly urbanizing countries in the world, Thailand and Vietnam, the approach and findings have implications for understanding global patterns of urbanization. Practical implications – The paper contributes to considering practical actions whether in terms of policy or project implementation for both the assessment of disaster and climate risk, and for actions to reduce vulnerability and promote resilience. Social implications – The paper draws largely from social science perspectives, highlighting the dynamism of social organization in urbanizing contexts, and the implications for risk and vulnerability. Originality/value – The paper draws on original research in Thailand and Vietnam that takes urbanization as the starting point for assessing vulnerability and risk.
Journal of Geophysical Research, 2007
1] In this study, individual precipitation samples, collected over 2 years at stations in differe... more 1] In this study, individual precipitation samples, collected over 2 years at stations in different climatic regions of west China (Tibetan Plateau region, Tianshan region, and Altay) were analyzed for the stable isotopes of precipitation to improve our understanding of how vapor transport impacts the modern stable isotopic distribution. Our results identify regional patterns in both d 18 O and deuterium excess (D excess, defined as dD -8d 18 O), and in particular we have identified the northward maximum extent of the southwest monsoon over the Tibetan Plateau. This demarcation is also the boundary for the fractionation effect of temperature on stable isotopes in precipitation. The patterns we have identified are as follows: In the southern Tibetan Plateau, along the southern slope of the Himalayas, our results show a distinct seasonality for both d 18 O and D excess as a result of the shift of summer monsoon moisture and winter westerly moisture transport. The signals of d 18 O in the western Tibetan Plateau reveal that the region receives southwest monsoonal moisture. In the east of the plateau, stable isotopic variation shows alternation between monsoon intrusion and recycling of northern moisture. (2) In contrast, in Tianshan there is an apparent ''temperature effect'' in d 18 O, with enriched values occurring in summer and depleted values occurring in winter. Seasonal D excess values, opposite to those observed in the southern Tibetan Plateau, are controlled by differing seasonal evaporation conditions. (3) In Altay, the most northern mountain region, the seasonal d 18 O shows the same variation with that in Tianshan region. However, D excess shows no apparent seasonal variation.
Journal of Geophysical Research, 2006
1] Many have made efforts to clarify the climatic significance of stable isotopic variations in i... more 1] Many have made efforts to clarify the climatic significance of stable isotopic variations in ice cores around central Asia through the study of stable isotopes in present-day precipitation. A new shallow ice core from Muztagata, in the eastern Pamirs, allows for a detailed comparison of annual d 18 O variation with local meteorological data as well as with global air temperature variations. On the basis of a comparison of seasonal fluctuations of d 18 O in the local precipitation, the 41.6-m ice core drilled at 7010 m provides a record of about one-half century. The annual fluctuations of d 18 O in this ice core are in good agreement (correlation coefficient of 0.67) with the annual air temperature changes at the nearby meteorological station Taxkorgen, indicating that the isotopic record from this ice core is a reliable temperature trend indicator. The most important discovery from the d 18 O variation of this ice core is a rapid warming trend in the 1990s, which is consistent with a general global warming trend over this time period. This recent rapid warming at higher elevations in this area has led to the quick retreat of alpine glaciers.
Journal of Geophysical Research, 2002
1] We describe the development of an automated gas chromatography-isotope ratio mass spectrometry... more 1] We describe the development of an automated gas chromatography-isotope ratio mass spectrometry (GC-IRMS) system capable of measuring the carbon isotopic composition of atmospheric methane (d 13 CH 4 ) with a precision of better than 0.1%. The system requires 200 mL of air and completes a single analysis in 15 min. The combination of small sample size, fast analysis time, and high precision has allowed us to measure background variations in atmospheric d 13 CH 4 through the NOAA Climate Monitoring and Diagnostics Laboratory Cooperative Air Sampling Network. We then present a record of d 13 CH 4 obtained from six surface sites of the network between January 1998 and December 1999. The sites are Barrow, Alaska (71°N); Niwot Ridge, Colorado (40°N); Mauna Loa, Hawaii (20°N); American Samoa (14°S); Cape Grim, Tasmania (41°S); and the South Pole (90°S). For the years 1998 and 1999, the globally averaged surface d 13 C value was À47.1%, and the average difference between Barrow and the South Pole was 0.6%. Consistent seasonal variations were seen only in the Northern Hemisphere, especially at Barrow, where the average amplitude was 0.5%. Seasonal variations in 1998, however, were evident at all sites, the cause of which is unknown. We also use a two-box model to examine the extent to which annual average d 13 C and CH 4 mole fraction measurements can constrain broad categories of source emissions. We find that the biggest sources of error are not the atmospheric d 13 C measurements but instead the radiocarbon-derived fossil fuel emission estimates, rate coefficients for methane destruction, and isotopic ratios of source emissions.
Global Biogeochemical Cycles, 2005
1] This paper describes background characteristics of atmospheric CO 2 and stable isotopic ratios... more 1] This paper describes background characteristics of atmospheric CO 2 and stable isotopic ratios (d 13 C and d 18 O) as well as their possible drivers at Waliguan Baseline Observatory (WLG) (36°17 0 N, 100°54 0 E, 3816 m above sea level) in the inland plateau of western China. The study is based on observational CO 2 data (NOAA Climate Monitoring and Diagnostics Laboratory discrete and WLG continuous measurements) obtained at WLG for the period from May 1991 to December 2002. Over this period the change in monthly means is +16ppmforCO2,+16 ppm for CO 2 , +16ppmforCO2,À0.2% for d 13 C, and Aˋ0.5À0.5% for d 18 O. The overall increase of CO 2 and subsequent decline of d 13 C, with a Dd 13 C/DCO 2 ratio (À0.011 ± 0.105) % ppm À1 at WLG, reflect the persistent worldwide influence of fossil fuel emissions. The negative secular trend of d 18 O at WLG is probably due to vigorous 18 O exchange with soils in the Northern Hemisphere (NH) and conversion from C 3 to C 4 plants via land use change. The CO 2 , d 13 C, and d 18 O mean annual cycles with peak-to-peak annual amplitudes of Aˋ0.510.5 ppm, 0.4990.499 %, and 0.4990.819%, respectively, at WLG show typical middle-to-high NH continental features that correspond to the seasonal cycle of the terrestrial biosphere. The significant CO 2 and d 13 C interannual variability at WLG is very likely caused by worldwide climate anomalies and associated regional fluctuation in biospheric CO 2 uptake in the Asian inland plateau as well as long-range air mass transport. The results of this study help to provide a basic understanding of the individual sources and sinks of carbon in this area and help us to better address the role of the Asian inland terrestrial biosphere in the global carbon cycle.