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Title: Attribution of changes in global wetland methane emissions from pre-industrial to present using CLM4.5-BGC

An understanding of potential factors controlling methane emissions from natural wetlands is important to accurately project future atmospheric methane concentrations. Here, we examine the relative contributions of climatic and environmental factors, such as precipitation, temperature, atmospheric CO 2 concentration, nitrogen deposition, wetland inundation extent, and land-use and land-cover change, on changes in wetland methane emissions from preindustrial to present day (i.e., 1850-2005). We apply a mechanistic methane biogeochemical model integrated in the Community Land Model version 4.5 (CLM4.5), the land component of the Community Earth System Model. The methane model explicitly simulates methane production, oxidation, ebullition, transport through aerenchyma of plants, and aqueous and gaseous diffusion. We conduct a suite of model simulations from 1850 to 2005, with all changes in environmental factors included, and sensitivity studies isolating each factor. Globally, we estimate that preindustrial methane emissions were higher by 10% than present-day emissions from natural wetlands, with emissions changes from preindustrial to the present of +15%, -41%, and -11% for the high latitudes, temperate regions, and tropics, respectively. The most important change is due to the estimated change in wetland extent, due to the conversion of wetland areas to drylands by humans. This effect alone leads to higher preindustrialmore » global methane fluxes by 33% relative to the present, with the largest change in temperate regions (+80%). These increases were partially offset by lower preindustrial emissions due to lower CO 2 levels (10%), shifts in precipitation (7%), lower nitrogen deposition (3%), and changes in land-use and land-cover (2%). Cooler temperatures in the preindustrial regions resulted in our simulations in an increase in global methane emissions of 6% relative to present day. Much of the sensitivity to these perturbations is mediated in the model by changes in methane substrate production and the areal extent of wetlands. The detrended interannual variability of high-latitude methane emissions is explained by the variation in substrate production and wetland inundation extent, whereas the tropical emission variability is explained by both of those variables and precipitation.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [4]
  1. Cornell Univ., Ithaca, NY (United States); Everglades Foundation, Palmetto Bay, FL (United States)
  2. Cornell Univ., Ithaca, NY (United States)
  3. Western Michigan Univ., Kalamazoo MI (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Environmental Research Letters
Additional Journal Information:
Journal Volume: 11; Journal Issue: 3; Journal ID: ISSN 1748-9326
Publisher:
IOP Publishing
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1379146

Paudel, Rajendra, Mahowald, Natalie M., Hess, Peter G. M., Meng, Lei, and Riley, William J.. Attribution of changes in global wetland methane emissions from pre-industrial to present using CLM4.5-BGC. United States: N. p., Web. doi:10.1088/1748-9326/11/3/034020.
Paudel, Rajendra, Mahowald, Natalie M., Hess, Peter G. M., Meng, Lei, & Riley, William J.. Attribution of changes in global wetland methane emissions from pre-industrial to present using CLM4.5-BGC. United States. doi:10.1088/1748-9326/11/3/034020.
Paudel, Rajendra, Mahowald, Natalie M., Hess, Peter G. M., Meng, Lei, and Riley, William J.. 2016. "Attribution of changes in global wetland methane emissions from pre-industrial to present using CLM4.5-BGC". United States. doi:10.1088/1748-9326/11/3/034020. https://www.osti.gov/servlets/purl/1379146.
@article{osti_1379146,
title = {Attribution of changes in global wetland methane emissions from pre-industrial to present using CLM4.5-BGC},
author = {Paudel, Rajendra and Mahowald, Natalie M. and Hess, Peter G. M. and Meng, Lei and Riley, William J.},
abstractNote = {An understanding of potential factors controlling methane emissions from natural wetlands is important to accurately project future atmospheric methane concentrations. Here, we examine the relative contributions of climatic and environmental factors, such as precipitation, temperature, atmospheric CO2 concentration, nitrogen deposition, wetland inundation extent, and land-use and land-cover change, on changes in wetland methane emissions from preindustrial to present day (i.e., 1850-2005). We apply a mechanistic methane biogeochemical model integrated in the Community Land Model version 4.5 (CLM4.5), the land component of the Community Earth System Model. The methane model explicitly simulates methane production, oxidation, ebullition, transport through aerenchyma of plants, and aqueous and gaseous diffusion. We conduct a suite of model simulations from 1850 to 2005, with all changes in environmental factors included, and sensitivity studies isolating each factor. Globally, we estimate that preindustrial methane emissions were higher by 10% than present-day emissions from natural wetlands, with emissions changes from preindustrial to the present of +15%, -41%, and -11% for the high latitudes, temperate regions, and tropics, respectively. The most important change is due to the estimated change in wetland extent, due to the conversion of wetland areas to drylands by humans. This effect alone leads to higher preindustrial global methane fluxes by 33% relative to the present, with the largest change in temperate regions (+80%). These increases were partially offset by lower preindustrial emissions due to lower CO2 levels (10%), shifts in precipitation (7%), lower nitrogen deposition (3%), and changes in land-use and land-cover (2%). Cooler temperatures in the preindustrial regions resulted in our simulations in an increase in global methane emissions of 6% relative to present day. Much of the sensitivity to these perturbations is mediated in the model by changes in methane substrate production and the areal extent of wetlands. The detrended interannual variability of high-latitude methane emissions is explained by the variation in substrate production and wetland inundation extent, whereas the tropical emission variability is explained by both of those variables and precipitation.},
doi = {10.1088/1748-9326/11/3/034020},
journal = {Environmental Research Letters},
number = 3,
volume = 11,
place = {United States},
year = {2016},
month = {3}
}