scholarly journals Attribution of spatial and temporal variations in terrestrial methane flux over North America

2010 ◽  
Vol 7 (11) ◽  
pp. 3637-3655 ◽  
Author(s):  
X. F. Xu ◽  
H. Q. Tian ◽  
C. Zhang ◽  
M. L. Liu ◽  
W. Ren ◽  
...  
Keyword(s):  
North America ◽  
Global Change ◽  
Climate Variability ◽  
Spatial Data ◽  
Climatic Variability ◽  
Temporal Variations ◽  
Spatial And Temporal Variations ◽  
Ch4 Emission ◽  
Ch4 Flux ◽  
Change Factors

Abstract. The attribution of spatial and temporal variations in terrestrial methane (CH4) flux is essential for assessing and mitigating CH4 emission from terrestrial ecosystems. In this study, we used a process-based model, the Dynamic Land Ecosystem Model (DLEM), in conjunction with spatial data of six major environmental factors to attribute the spatial and temporal variations in the terrestrial methane (CH4) flux over North America from 1979 to 2008 to six individual driving factors and their interaction. Over the past three decades, our simulations indicate that global change factors accumulatively contributed 23.51 ± 9.61 T g CH4-C (1 Tg = 1012 g) emission over North America, among which ozone (O3) pollution led to a reduced CH4 emission by 2.30 ± 0.49 T g CH4-C. All other factors including climate variability, nitrogen (N) deposition, elevated atmospheric carbon dioxide (CO2), N fertilizer application, and land conversion enhanced terrestrial CH4 emissions by 19.80 ± 12.42 T g CH4-C, 0.09 ± 0.02 T g CH4-C, 6.80 ± 0.86 T g CH4-C, 0.01 ± 0.001 T g CH4-C, and 3.95 ± 0.38 T g CH4-C, respectively, and interaction between/among these global change factors led to a decline of CH4 emission by 4.84 ± 7.74 T g CH4-C. Climate variability and O3 pollution suppressed, while other factors stimulated CH4 emission over the USA; climate variability significantly enhanced, while all the other factors exerted minor effects, positive or negative, on CH4 emission in Canada; Mexico functioned as a sink for atmospheric CH4 with a major contribution from climate change. Climatic variability dominated the inter-annual variations in terrestrial CH4 flux at both continental and country levels. Precipitation played an important role in the climate-induced changes in terrestrial CH4 flux at both continental and country-levels. The relative importance of each environmental factor in determining the magnitude of CH4 flux showed substantially spatial variation across North America. This factorial attribution of CH4 flux in North America might benefit policy makers who would like to curb climate warming by reducing CH4 emission.

scholarly journals Attribution of spatial and temporal variations in terrestrial methane flux over North America

2010 ◽  
Vol 7 (4) ◽  
pp. 5383-5428 ◽  
Author(s):  
X. F. Xu ◽  
H. Q. Tian ◽  
C. Zhang ◽  
M. L. Liu ◽  
W. Ren ◽  
...  
Keyword(s):  
North America ◽  
Global Change ◽  
Spatial Data ◽  
Climatic Variability ◽  
Methane Flux ◽  
Temporal Variations ◽  
Spatial And Temporal Variations ◽  
Ch4 Emission ◽  
Ch4 Flux ◽  
Change Factors

Abstract. The attribution of spatial and temporal variations in terrestrial methane (CH4) flux is essential for assessing and mitigating CH4 emission from terrestrial ecosystems. In this study, we used a process-based model, the Dynamic Land Ecosystem Model (DLEM), in conjunction with spatial data of six major environmental factors to attribute the spatial and temporal variations in the terrestrial methane (CH4) flux over North America from 1979 to 2008 to six individual factors and their interaction. Over the past three decades, our simulation indicates that global change factors accumulatively contributed 43.05 Tg CH4-C (1 Tg = 1012 g) emission over North America, among which ozone (O3) pollution led to a reduced CH4 emission by 2.69 Tg CH4-C, all other factors including climate variability, nitrogen (N) deposition, rising atmospheric carbon dioxide (CO2), N fertilization, and land conversion increased terrestrial CH4 emissions by 40.37 Tg CH4-C, 0.42 Tg CH4-C, 6.95 Tg CH4-C, 0.11 Tg CH4-C, and 3.70 Tg CH4-C, respectively, and interaction between/among these global change factors led to a decline of CH4 emission by 5.80 Tg CH4-C. Climatic variability dominated the inter-annual variations in terrestrial CH4 fluxes at both continental and country levels. The relative importance of each environmental factor in determining the magnitude of methane flux shows substantially spatial variation across North America. This factorial attribution of CH4 fluxes over the North America might benefit policy makers who would like to curb climate warming by reducing CH4 emission.

scholarly journals Multifactor controls on terrestrial N<sub>2</sub>O flux over North America from 1979 through 2010

2012 ◽  
Vol 9 (4) ◽  
pp. 1351-1366 ◽  
Author(s):  
X. F. Xu ◽  
H. Q. Tian ◽  
G. S. Chen ◽  
M. L. Liu ◽  
W. Ren ◽  
...  
Keyword(s):  
North America ◽  
Global Change ◽  
Climate Variability ◽  
Fertilizer Application ◽  
N2o Emission ◽  
N Deposition ◽  
N Fertilizer ◽  
Multiple Factors ◽  
Change Factors ◽  
Factor Interaction

Abstract. Nitrous oxide (N2O) is a potent greenhouse gas which also contributes to the depletion of stratospheric ozone (O3). However, the magnitude and underlying mechanisms for the spatiotemporal variations in the terrestrial sources of N2O are still far from certain. Using a process-based ecosystem model (DLEM – the Dynamic Land Ecosystem Model) driven by multiple global change factors, including climate variability, nitrogen (N) deposition, rising atmospheric carbon dioxide (CO2), tropospheric O3 pollution, N fertilizer application, and land conversion, this study examined the spatial and temporal variations in terrestrial N2O flux over North America and further attributed these variations to various driving factors. From 1979 to 2010, the North America cumulatively emitted 53.9 ± 0.9 Tg N2O-N (1 Tg = 1012 g), of which global change factors contributed 2.4 ± 0.9 Tg N2O-N, and baseline emission contributed 51.5 ± 0.6 Tg N2O-N. Climate variability, N deposition, O3 pollution, N fertilizer application, and land conversion increased N2O emission while the elevated atmospheric CO2 posed opposite effect at continental level; the interactive effect among multiple factors enhanced N2O emission over the past 32 yr. N input, including N fertilizer application in cropland and N deposition, and multi-factor interaction dominated the increases in N2O emission at continental level. At country level, N fertilizer application and multi-factor interaction made large contribution to N2O emission increase in the United States of America (USA). The climate variability dominated the increase in N2O emission from Canada. N inputs and multiple factors interaction made large contribution to the increases in N2O emission from Mexico. Central and southeastern parts of the North America – including central Canada, central USA, southeastern USA, and all of Mexico – experienced increases in N2O emission from 1979 to 2010. The fact that climate variability and multi-factor interaction largely controlled the inter-annual variations in terrestrial N2O emission at both continental and country levels indicate that projected changes in the global climate system may substantially alter the regime of N2O emission from terrestrial ecosystems during the 21st century. Our study also showed that the interactive effect among global change factors may significantly affect N2O flux, and more field experiments involving multiple factors are urgently needed.

scholarly journals Multiple-factor controls on terrestrial N<sub>2</sub>O flux over North America from 1979 through 2010

2011 ◽  
Vol 8 (6) ◽  
pp. 10935-10977 ◽  
Author(s):  
X. F. Xu ◽  
H. Q. Tian ◽  
M. L. Liu ◽  
W. Ren ◽  
G. S. Chen ◽  
...  
Keyword(s):  
North America ◽  
Global Change ◽  
Climate Variability ◽  
N2o Emission ◽  
Atmospheric Co2 ◽  
Land Conversion ◽  
Elevated Atmospheric Co2 ◽  
Change Factors ◽  
Factor Interaction ◽  
Multiple Factor

Abstract. Nitrous oxide (N2O) is a potent greenhouse gas which also contributes to the depletion of stratospheric ozone (O3). However, the magnitude and underlying mechanisms for the spatiotemporal variations in the terrestrial sources of N2O are still far from certain. Using a process-based ecosystem model (DLEM – the Dynamic Land Ecosystem Model) driven by multiple global change factors, including climate variability, nitrogen (N) deposition, rising atmospheric CO2, trophospheric O3 pollution, N fertilizer application, and land conversion, the spatial and temporal variations in terrestrial N2O flux over North America were examined and attributed to various driving factors. From 1979 to 2010, the North America accumulatively emitted 55.1 ± 0.8 Tg N2O-N (1 Tg = 1012 g), of which global change factors contributed 2.8 ± 1.0 Tg N2O-N, and baseline emission contributed 52.3 ± 0.6 Tg N2O-N. Climate variability, N deposition, O3 pollution, N fertilizer application, and land conversion increased N2O emission by 0.3 ± 0.7 Tg N2O-N, 0.5 ± 0.1 Tg N2O-N, 0.11 ± 0.02 Tg N2O-N, 1.2 ± 0.1 Tg N2O-N, and 0.2 ± 0.02 Tg N2O-N, respectively. The elevated atmospheric CO2 led to a decrease in terrestrial N2O emission by 0.5 ± 0.07 Tg N2O-N. The interactive effect among multiple factors enhanced N2O emission by 0.9 ± 0.3 Tg N2O-N over the 32 years. At country level, climate variability and elevated atmospheric CO2 decreased, while all other single factors and multiple-factor interaction enhanced N2O emission in the United States of America (USA) over the study period. During the same time period, elevated atmospheric CO2 and multiple-factor interaction decreased, while other factors enhanced N2O emission from Canada. Elevated atmospheric CO2 and land conversion decreased while other factors enhanced N2O emission from Mexico. The interactive effects among climate variables play a predominant role in controlling climate -induced changes in N2O emission at both continental and country levels. Central and southeastern parts of the North America – including central Canada, central USA, southeastern USA, and all of Mexico – experienced increases in N2O emission from 1979 to 2010. The effects of climate variability and multiple-factor interaction dominating the inter-annual variations in terrestrial N2O emission at both continental and country levels indicate that projected changes in the global climate system during this century may substantially alter the regime of N2O emission from terrestrial ecosystems. They also imply that the interactive effect among global change factors may significantly affect N2O flux, needing more investigations through field experiments.

scholarly journals Increasing Frequency in Off-Season Tropical Cyclones and its relation to Climate Variability and Change

2020 ◽  
Author(s):  
José J. Hernandez Ayala ◽  
Rafael Méndez-Tejeda
Keyword(s):  
Climate Change ◽  
Climate Variability ◽  
Surface Temperature ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Linear Regression Models ◽  
Climate Variability And Change ◽  
West Pacific ◽  
Change Factors ◽  
Increasing Trends

Abstract. This article analyzes the relationship between off-season tropical cyclone (TC) frequency and climate variability and change for the Pacific and Atlantic Ocean basins. TC track data was used to extract the off-season storms for the 1900–2019 period. TC counts were aggregated by decade and the number of storms for the first six decades (pre-satellite era) was adjusted. Mann-Kendall non-parametric tests were used to identify trends in decadal TC counts and multiple linear regression models (MRL) were used to test if climatic variability or climate change factors explained the trends in off-season storms. MRL stepwise procedures were implemented to identify the climate variability and change factors that explained most of the variability in off-season TC frequency. A total of 713 TCs were identified as occurring earlier or later than their peak seasons, most during the month of May and in the West Pacific and South Pacific basins. The East Pacific (EP), North Atlantic (NA) and West Pacific (WP) basins exhibit significant increasing trends in decadal off-season TC frequency. MRL results show that trends in sea surface temperature, global mean surface temperature, and cloud cover explain most of the increasing trend in decadal off-season TC counts in the EP, NA, and WP basins. Stepwise MLR results also identified climate change variables as the dominant forces behind increasing trends in off-season TC decadal counts, yet they also showed that climate variability factors like El Niño-Southern Oscillation, the Atlantic Multidecadal Oscillation, and the Interdecadal Pacific Oscillation also account for a portion of the variability.

scholarly journals Pacific Decadal Oscillation Climate Variability and Temporal Pattern of Winter Flows in Northwestern North America

2010 ◽  
Vol 11 (4) ◽  
pp. 917-933 ◽  
Author(s):  
M. N. Khaliq ◽  
P. Gachon
Keyword(s):  
Time Series ◽  
Water Resources ◽  
North America ◽  
Climate Variability ◽  
Pacific Decadal Oscillation ◽  
Large Scale ◽  
Temporal Variations ◽  
Average Percentage ◽  
Daily Streamflow ◽  
Northwestern North America

Abstract There is growing concern about the effects of large-scale oceanic atmospheric climate variability, such as the Pacific decadal oscillation (PDO), on regional hydrology and water resources. In this paper, the effects of PDO on temporal patterns of winter (January–March) flow in northwestern North America (NWNA), which is believed to be a PDO-sensitive region, is studied for the period 1943–2007 using daily streamflow data from a much larger set of 179 stations, compared to previous studies in which only smaller subsets of these stations were analyzed. Time series of winter flows were divided into two nonoverlapping blocks corresponding to change points detected in time series of December–March mean monthly PDO indices. Both parametric and nonparametric measures of correlation and average percentage differences and average standardized differences from the period-of-record mean were explored. Like some of the previous studies, it is found that, on average, winter flows tend to be higher (lower) during the warm (cold) phase of the PDO and that establishes the physical link between large-scale climate variability and basin response. It is shown that the serial structure of time series of PDO indices conforms to that of a stochastic process with long-term persistence (LTP). Based on this finding and the climate–streamflow physical link, it is plausible to investigate temporal variations in winter flows with the LTP hypothesis, in addition to assuming merely independence (IND) or short-term persistence (STP). The results of the analysis demonstrate that the LTP mechanism, in combination with the STP, is able to explain more than half of the significant trends noted, with the IND assumption suggesting that the significance of trends reported in previous studies in NWNA may have been overstated. This result has important implications for future planning of regional water resources.

scholarly journals Increasing frequency in off-season tropical cyclones and its relation to climate variability and change

2020 ◽  
Vol 1 (2) ◽  
pp. 745-757
Author(s):  
José J. Hernández Ayala ◽  
Rafael Méndez-Tejeda
Keyword(s):  
Climate Change ◽  
Climate Variability ◽  
Surface Temperature ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Nonparametric Tests ◽  
Climate Variability And Change ◽  
West Pacific ◽  
Change Factors ◽  
Increasing Trends

Abstract. This article analyzes the relationship between off-season tropical cyclone (TC) frequency and climate variability and change for the Pacific Ocean and Atlantic Ocean basins. TC track data were used to extract the off-season storms for the 1900–2019 period. TC counts were aggregated by decade, and the number of storms for the first 6 decades (presatellite era) was adjusted. Mann–Kendall nonparametric tests were used to identify trends in decadal TC counts and multiple linear regression (MLR) models were used to test if climatic variability or climate change factors explained the trends in off-season storms. MLR stepwise procedures were implemented to identify the climate variability and change factors that explained most of the variability in off-season TC frequency. A total of 713 TCs were identified as occurring earlier or later than their peak seasons, most during the month of May and in the West Pacific and South Pacific basins. The East Pacific (EP), North Atlantic (NA) and West Pacific (WP) basins exhibit significant increasing trends in decadal off-season TC frequency. MLR results show that trends in sea surface temperature, global mean surface temperature and cloud cover explain most of the increasing trend in decadal off-season TC counts in the EP, NA and WP basins. Stepwise MLR results also identified climate change variables as the dominant forces behind increasing trends in off-season TC decadal counts, yet they also showed that climate variability factors like El Niño–Southern Oscillation, the Atlantic Multidecadal Oscillation and the Interdecadal Pacific Oscillation also account for a portion of the variability.

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