Felzer Benjamin S.

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Felzer

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Benjamin S.

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Methane fluxes between terrestrial ecosystems and the atmosphere at northern high latitudes during the past century : a retrospective analysis with a process-based biogeochemistry model

(American Geophysical Union, 2008-08-18) Zhuang, Qianlai ; Melillo, Jerry M. ; Kicklighter, David W. ; Prinn, Ronald G. ; McGuire, A. David ; Steudler, Paul A. ; Felzer, Benjamin S. ; Hu, Shaomin

We develop and use a new version of the Terrestrial Ecosystem Model (TEM) to study how rates of methane (CH4) emissions and consumption in high-latitude soils of the Northern Hemisphere have changed over the past century in response to observed changes in the region's climate. We estimate that the net emissions of CH4 (emissions minus consumption) from these soils have increased by an average 0.08 Tg CH4 yr−1 during the twentieth century. Our estimate of the annual net emission rate at the end of the century for the region is 51 Tg CH4 yr−1. Russia, Canada, and Alaska are the major CH4 regional sources to the atmosphere, responsible for 64%, 11%, and 7% of these net emissions, respectively. Our simulations indicate that large interannual variability in net CH4 emissions occurred over the last century. Our analyses of the responses of net CH4 emissions to the past climate change suggest that future global warming will increase net CH4 emissions from the Pan-Arctic region. The higher net CH4 emissions may increase atmospheric CH4 concentrations to provide a major positive feedback to the climate system.
Nitrogen effect on carbon-water coupling in forests, grasslands, and shrublands in the arid western United States

(American Geophysical Union, 2011-08-25) Felzer, Benjamin S. ; Cronin, Timothy W. ; Melillo, Jerry M. ; Kicklighter, David W. ; Schlosser, C. Adam ; Dangal, Shree R. S.

As greenhouse gases, including CO2, accumulate in the atmosphere, the western United States is predicted to undergo large-scale climate warming and reduced summer precipitation in the coming decades. In this study we explore the role of these climate changes with elevated CO2 to determine the plant physiological response on primary productivity and associated feedbacks on evapotranspiration (ET) and runoff using a biogeochemistry model, TEM-Hydro, with downscaled climate data for the western United States from the NCAR CCSM3 A2 scenario. Net primary productivity increases by 32% in forests due to feedbacks between warmer temperatures and enhanced nitrogen mineralization but decreases in shrublands by 24% due to excessive drying and reduced nitrogen mineralization. Warming directly increases nitrogen mineralization rates but indirectly decreases them by reducing soil moisture, so the net effect is highly dependent on climatic conditions within each biome. Increased soil moisture resulting from larger water use efficiency from the elevated CO2 leads to more net nitrogen mineralization in forests, which reduces N-limiting conditions. The effect of CO2 on stomatal conductance is therefore enhanced because of its effect on reducing nitrogen limiting conditions. Runoff decreases over the 21st century by 22% in forests, 58% in grasslands, and 67% in shrublands due to the reduced precipitation in each region but is modulated by the plant-induced changes in ET. The role of moisture limitation is therefore a crucial regulator of nitrogen limitation, which determines the future productivity and water availability in the West.
Consequences of considering carbon–nitrogen interactions on the feedbacks between climate and the terrestrial carbon cycle

(American Meteorological Society, 2008-08-01) Sokolov, Andrei P. ; Kicklighter, David W. ; Melillo, Jerry M. ; Felzer, Benjamin S. ; Schlosser, C. Adam ; Cronin, Timothy W.

The impact of carbon–nitrogen dynamics in terrestrial ecosystems on the interaction between the carbon cycle and climate is studied using an earth system model of intermediate complexity, the MIT Integrated Global Systems Model (IGSM). Numerical simulations were carried out with two versions of the IGSM’s Terrestrial Ecosystems Model, one with and one without carbon–nitrogen dynamics. Simulations show that consideration of carbon–nitrogen interactions not only limits the effect of CO2 fertilization but also changes the sign of the feedback between the climate and terrestrial carbon cycle. In the absence of carbon–nitrogen interactions, surface warming significantly reduces carbon sequestration in both vegetation and soil by increasing respiration and decomposition (a positive feedback). If plant carbon uptake, however, is assumed to be nitrogen limited, an increase in decomposition leads to an increase in nitrogen availability stimulating plant growth. The resulting increase in carbon uptake by vegetation exceeds carbon loss from the soil, leading to enhanced carbon sequestration (a negative feedback). Under very strong surface warming, however, terrestrial ecosystems become a carbon source whether or not carbon–nitrogen interactions are considered. Overall, for small or moderate increases in surface temperatures, consideration of carbon–nitrogen interactions result in a larger increase in atmospheric CO2 concentration in the simulations with prescribed carbon emissions. This suggests that models that ignore terrestrial carbon–nitrogen dynamics will underestimate reductions in carbon emissions required to achieve atmospheric CO2 stabilization at a given level. At the same time, compensation between climate-related changes in the terrestrial and oceanic carbon uptakes significantly reduces uncertainty in projected CO2 concentration.
Probabilistic forecast for twenty-first-century climate based on uncertainties in emissions (without policy) and climate parameters

(American Meteorological Society, 2009-10-01) Sokolov, Andrei P. ; Stone, P. H. ; Forest, C. E. ; Prinn, Ronald G. ; Sarofim, Marcus C. ; Webster, M. ; Paltsev, Sergey ; Schlosser, C. Adam ; Kicklighter, David W. ; Dutkiewicz, Stephanie ; Reilly, John M. ; Wang, C. ; Felzer, Benjamin S. ; Melillo, Jerry M. ; Jacoby, Henry D.

The Massachusetts Institute of Technology (MIT) Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100. Since the model’s first projections were published in 2003, substantial improvements have been made to the model, and improved estimates of the probability distributions of uncertain input parameters have become available. The new projections are considerably warmer than the 2003 projections; for example, the median surface warming in 2091–2100 is 5.1°C compared to 2.4°C in the earlier study. Many changes contribute to the stronger warming; among the more important ones are taking into account the cooling in the second half of the twentieth century due to volcanic eruptions for input parameter estimation and a more sophisticated method for projecting gross domestic product (GDP) growth, which eliminated many low-emission scenarios. However, if recently published data, suggesting stronger twentieth-century ocean warming, are used to determine the input climate parameters, the median projected warming at the end of the twenty-first century is only 4.1°C. Nevertheless, all ensembles of the simulations discussed here produce a much smaller probability of warming less than 2.4°C than implied by the lower bound of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) projected likely range for the A1FI scenario, which has forcing very similar to the median projection in this study. The probability distribution for the surface warming produced by this analysis is more symmetric than the distribution assumed by the IPCC because of a different feedback between the climate and the carbon cycle, resulting from the inclusion in this model of the carbon–nitrogen interaction in the terrestrial ecosystem.
Corrigendum

(American Meteorological Society, 2010-04-15) Sokolov, Andrei P. ; Stone, P. H. ; Forest, C. E. ; Prinn, Ronald G. ; Sarofim, Marcus C. ; Webster, M. ; Paltsev, Sergey ; Schlosser, C. Adam ; Kicklighter, David W. ; Dutkiewicz, Stephanie ; Reilly, John M. ; Wang, C. ; Felzer, Benjamin S. ; Melillo, Jerry M. ; Jacoby, Henry D.

Corrigendum: Sokolov, A., and Coauthors, 2009: Probabilistic forecast for twenty-first-century climate based on uncertainties in emissions (without policy) and climate parameters. J. Climate, 22, 5175–5204.
Effects of ozone on net primary production and carbon sequestration in the conterminous United States using a biogeochemistry model

( 2003-11-25) Felzer, Benjamin S. ; Kicklighter, David W. ; Melillo, Jerry M. ; Wang, C. ; Zhuang, Qianlai ; Prinn, Ronald G.

The effects of air pollution on vegetation may provide an important control on the carbon cycle that has not yet been widely considered. Prolonged exposure to high levels of ozone, in particular, has been observed to inhibit photosynthesis by direct cellular damage within the leaves and through possible changes in stomatal conductance. We have incorporated empirical equations derived for trees (hardwoods and pines) and crops into the Terrestrial Ecosystem Model to explore the effects of ozone on net primary production and carbon sequestration across the conterminous United States. Our results show a 2.6 – 6.8% mean reduction for the U.S. in annual Net Primary Production (NPP) in response to modeled historical ozone levels during the late 1980s-early 1990s. The largest decreases (over 13% in some locations) occur in the Midwest agricultural lands, during the mid-summer when ozone levels are highest. Carbon sequestration since the 1950s has been reduced by 18 - 38 Tg C yr-1 with the presence of ozone. Thus the effects of ozone on NPP and carbon sequestration should be factored into future calculations of the US carbon budget.
Net emissions of CH4 and CO2 in Alaska : implications for the region's greenhouse gas budget

(Ecological Society of America, 2007-01) Zhuang, Qianlai ; Melillo, Jerry M. ; McGuire, A. David ; Kicklighter, David W. ; Prinn, Ronald G. ; Steudler, Paul A. ; Felzer, Benjamin S. ; Hu, Shaomin

We used a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to study the net methane (CH4) fluxes between Alaskan ecosystems and the atmosphere. We estimated that the current net emissions of CH4 (emissions minus consumption) from Alaskan soils are 3 Tg CH4/yr. Wet tundra ecosystems are responsible for 75% of the region's net emissions, while dry tundra and upland boreal forests are responsible for 50% and 45% of total consumption over the region, respectively. In response to climate change over the 21st century, our simulations indicated that CH4 emissions from wet soils would be enhanced more than consumption by dry soils of tundra and boreal forests. As a consequence, we projected that net CH4 emissions will almost double by the end of the century in response to high-latitude warming and associated climate changes. When we placed these CH4 emissions in the context of the projected carbon budget (carbon dioxide [CO2] and CH4) for Alaska at the end of the 21st century, we estimated that Alaska will be a net source of greenhouse gases to the atmosphere of 69 Tg CO2 equivalents/yr, that is, a balance between net methane emissions of 131 Tg CO2 equivalents/yr and carbon sequestration of 17 Tg C/yr (62 Tg CO2 equivalents/yr).
Correction to “Importance of carbon-nitrogen interactions and ozone on ecosystem hydrology during the 21st century”

(American Geophysical Union, 2009-08-22) Felzer, Benjamin S. ; Cronin, Timothy W. ; Melillo, Jerry M. ; Kicklighter, David W. ; Schlosser, C. Adam
CO2 and CH4 exchanges between land ecosystems and the atmosphere in northern high latitudes over the 21st century

(American Geophysical Union, 2006-09-15) Zhuang, Qianlai ; Melillo, Jerry M. ; Sarofim, Marcus C. ; Kicklighter, David W. ; McGuire, A. David ; Felzer, Benjamin S. ; Sokolov, Andrei P. ; Prinn, Ronald G. ; Steudler, Paul A. ; Hu, Shaomin

Terrestrial ecosystems of the northern high latitudes (above 50oN) exchange large amounts of CO2 and CH4 with the atmosphere each year. Here we use a process-based model to estimate the budget of CO2 and CH4 of the region for current climate conditions and for future scenarios by considering effects of permafrost dynamics, CO2 fertilization of photosynthesis and fire. We find that currently the region is a net source of carbon to the atmosphere at 276 Tg C yr-1. We project that throughout the 21st century, the region will most likely continue as a net source of carbon and the source will increase by up to 473 Tg C yr-1 by the end of the century compared to the current emissions. However our coupled carbon and climate model simulations show that these emissions will exert relatively small radiative forcing on global climate system compared to large amounts of anthropogenic emissions.
Impacts of ozone on trees and crops

( 2007-07-05) Felzer, Benjamin S. ; Cronin, Timothy W. ; Reilly, John M. ; Melillo, Jerry M. ; Wang, Xiaodong

In this review article, we explore how surface-level ozone affects trees and crops with special emphasis on consequences for productivity and carbon sequestration. Vegetation exposure to ozone reduces photosynthesis, growth, and other plant functions. Ozone formation in the atmosphere is a product of NOx that are also a source of nitrogen deposition. Reduced carbon sequestration of temperate forests resulting from ozone is likely offset by increased carbon sequestration from nitrogen fertilization. However, since fertilized croplands are generally not nitrogen-limited, capping ozone-polluting substances in the U.S., Europe, and China can reduce future crop yield loss substantially.
Future effects of ozone on carbon sequestration and climate change policy using a global biogeochemical model

( 2004-10-29) Felzer, Benjamin S. ; Reilly, John M. ; Melillo, Jerry M. ; Kicklighter, David W. ; Sarofim, Marcus C. ; Wang, C. ; Prinn, Ronald G. ; Zhuang, Qianlai

Exposure of plants to ozone inhibits photosynthesis and therefore reduces vegetation production and carbon sequestration. The reduced carbon storage would then require further reductions in fossil fuel emissions to meet a given CO2 concentration target, thereby increasing the cost of meeting the target. Simulations with the Terrestrial Ecosystem Model (TEM) for the historical period (1860-1995) show the largest damages occur in the Southeast and Midwestern regions of the United States, eastern Europe, and eastern China. The largest reductions in carbon storage for the period 1950-1995, 41%, occur in eastern Europe. Scenarios for the 21st century developed with the MIT Integrated Global Systems Model (IGSM) lead to even greater negative effects on carbon storage in the future. In some regions, current land carbon sinks become carbon sources, and this change leads to carbon sequestration decreases of up to 0.4 Pg C yr-1 due to damage in some regional ozone hot spots. With a climate policy, failing to consider the effects of ozone damage on carbon sequestration would raise the global costs over the next century of stabilizing atmospheric concentrations of CO2 equivalents at 550 ppm by 6 to 21%. Because stabilization at 550 ppm will reduce emission of other gases that cause ozone, these additional benefits are estimated to be between 5 and 25% of the cost of the climate policy. Tropospheric ozone effects on terrestrial ecosystems thus produce a surprisingly large feedback in estimating climate policy costs that, heretofore, has not been included in cost estimates.
Importance of carbon-nitrogen interactions and ozone on ecosystem hydrology during the 21st century

(American Geophysical Union, 2009-03-18) Felzer, Benjamin S. ; Cronin, Timothy W. ; Melillo, Jerry M. ; Kicklighter, David W. ; Schlosser, C. Adam

There is evidence that increasing CO2 concentrations have reduced evapotranspiration and increased runoff through reductions in stomatal conductance during the twentieth century. While this process will continue to counteract increased evapotranspiration associated with future warming, it is highly dependent upon concurrent changes in photosynthesis, especially due to CO2 fertilization, nitrogen limitation, and ozone exposure. A new version of the Terrestrial Ecosystem Model (TEM-Hydro) was developed to examine the effects of carbon and nitrogen on the water cycle. We used two climate models (NCAR CCSM3 and DOE PCM) and two emissions scenarios (SRES B1 and A2) to examine the effects of climate, elevated CO2, nitrogen limitation, and ozone exposure on the hydrological cycle in the eastern United States. While the direction of future runoff changes is largely dependent upon predicted precipitation changes, the effects of elevated CO2 on ecosystem function (stomatal closure and CO2 fertilization) increase runoff by 3–7%, as compared to the effects of climate alone. Consideration of nitrogen limitation and ozone damage on photosynthesis increases runoff by a further 6–11%. Failure to consider the effects of the interactions among nitrogen, ozone, and elevated CO2 may lead to significant regional underestimates of future runoff.
Global economic effects of changes in crops, pasture, and forests due to changing climate, carbon dioxide, and ozone

( 2006-01) Reilly, John M. ; Paltsev, Sergey ; Felzer, Benjamin S. ; Wang, X. ; Kicklighter, David W. ; Melillo, Jerry M. ; Prinn, Ronald G. ; Sarofim, Marcus C. ; Sokolov, Andrei P. ; Wang, C.

Multiple environmental changes will have consequences for global vegetation. To the extent that crop yields and pasture and forest productivity are affected there can be important economic consequences. We examine the combined effects of changes in climate, increases in carbon dioxide, and changes in tropospheric ozone on crop, pasture, and forest lands and the consequences for the global and regional economies. We examine scenarios where there is limited or little effort to control these substances, and policy scenarios that limit emissions of CO2 and ozone precursors. We find the effects of climate and CO2 to be generally positive, and the effects of ozone to be very detrimental. Unless ozone is strongly controlled damage could offset CO2 and climate benefits. We find that resource allocation among sectors in the economy, and trade among countries, can strongly affect the estimate of economic effect in a country.
Effects of tropospheric ozone pollution on net primary productivity and carbon storage in terrestrial ecosystems of China

(American Geophysical Union, 2007-11-17) Ren, Wei ; Tian, Hanqin ; Liu, Mingliang ; Zhang, Chi ; Chen, Guangsheng ; Pan, Shufen ; Felzer, Benjamin S. ; Xu, Xiaofeng

We investigated the potential effects of elevated ozone (O3) along with climate variability, increasing CO2, and land use change on net primary productivity (NPP) and carbon storage in China's terrestrial ecosystems for the period 1961–2000 with a process-based Dynamic Land Ecosystem Model (DLEM) forced by the gridded data of historical tropospheric O3 and other environmental factors. The simulated results showed that elevated O3 could result in a mean 4.5% reduction in NPP and 0.9% reduction in total carbon storage nationwide from 1961 to 2000. The reduction of carbon storage varied from 0.1 Tg C to 312 Tg C (a decreased rate ranging from 0.2% to 6.9%) among plant functional types. The effects of tropospheric O3 on NPP were strongest in east-central China. Significant reductions in NPP occurred in northeastern and central China where a large proportion of cropland is distributed. The O3 effects on carbon fluxes and storage are dependent upon other environmental factors. Therefore direct and indirect effects of O3, as well as interactive effects with other environmental factors, should be taken into account in order to accurately assess the regional carbon budget in China. The results showed that the adverse influences of increasing O3 concentration across China on NPP could be an important disturbance factor on carbon storage in the near future, and the improvement of air quality in China could enhance the capability of China's terrestrial ecosystems to sequester more atmospheric CO2. Our estimation of O3 impacts on NPP and carbon storage in China, however, must be used with caution because of the limitation of historical tropospheric O3 data and other uncertainties associated with model parameters and field experiments.

Felzer Benjamin S.

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