Global Warming Forcing Research Articles

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The article takes as its starting point Leo Tolstoy’s character Pierre Bezukhov. His passive presence at the battle of Borodino, in Tolstoy’s War and Peace, is contrasted with today’s climate activism, exemplified by the Swedish human ecologist Andreas Malm. In his book How to Blow up a Pipeline, Malm argues that global warming forces scientists and scholars to become activists, and activists to turn to violence. This analysis, the article argues, is based on a simplistic notion of action (”one acts or one does not”) and a strong conviction of being right. If this certitude is problematic, it is also typical of our time. Where, then, does this tendency to simplify the complicated, and replace all uncertainty with sureness, come from? One answer is that activism requires determination, which in its turn presupposes access to the truth. Another explanation lies in the binary operations of the digital media we all rely upon. At the most basic level, these operations exclude all approximation, all nuances, all doubt: the options are one or zero. Against this background, it becomes crucial to defend a research practice that refrains from simplifications. In Sloterdijk, the article finds an argument for interrupting the affective impulses that reach us constantly. From Popper, it fetches an understanding of research as an event. Via Marx’s well-known formulation that philosophers must change the world, not just interpret it, the text then moves to Adorno’s defense of theoretical thinking. The question is, however, whether critical theory has any edge left. Has it not just become a part of the academic apparatus it once reacted against? The article finds an answer in Lyotard, and his idea of a theoretical apathy. This idea reminds a lot of the starting point of the article: Pierre Bezukhov’s comic but clear-sighted passivity on the battlefield.

Review of Micro- and Nanobubble Technologies: Advancements in Theory and Applications and Perspectives on Adsorption Cooling and Desalination Systems

Adsorption refrigerators are a compelling ecological alternative to compressor refrigerators; global warming forces us to constantly look for alternative sources of energy and cold. Cold production in adsorption chillers is based on the use of heat generated by other processes running in the company. Waste heat from production processes, which has, until now, been irretrievably lost, is a potential source of energy for generating cold via an adsorption unit producing chilled water. Cooling optimizes the use of the heating network in summer and can lead to increased electricity production while reducing heat supply losses. Thus far, attempts to implement adsorption refrigerators for widespread use have not been successful as a result of the low efficiency of these devices; this is directly related to the poor heat and mass transfer conditions in the beds and heat exchangers of adsorption refrigerators. The solutions used so far, such as new working pairs, glued beds or modifications to the structure or cycle length, are still not strong enough for these devices. Therefore, it is necessary to look for new solutions. Using micro- and nanobubbles as media to increase mass and heat transfer in refrigerators is an innovative and pioneering solution. Thus, this document describes the most important features of micro- and nanobubble technology applications in adsorption refrigerators. This article is an introduction and a basis for the implementation of further research, consolidating the existing literature as a review.

Global Warming: Plants and Animals on the Move

Global warming is forcing many species to change where they live. As temperatures rise, some places will become too hot for the plants and animals that live there now. Species will migrate out of these hot areas and into other areas that used to be too cold for them. In some cases, species will not be able to move fast enough to escape rising temperatures, or there will not be enough places with suitable climates left for them to live in—increasing the risk that these species will become extinct. As global warming forces many plant and animal species to move around, or causes them to become extinct from certain areas, the types of species that we find around us will change, which will affect our lives.

Mega-city development impact on hourly extreme rainfall over the South China Greater Bay Area under near-future climate warming

The impacts of near-future urban development and global warming forcing on hourly extreme rainfall over the South China Greater Bay Area (GBA) area have been investigated, by dynamically downscaling General Circulation Model (GCM) outputs using the Weather Research and Forecasting Model (WRF) at convection-permitting resolution, coupled with an Urban Canopy Model (UCM). Three downscaling experiments corresponding to different urban land cover (1999 and projected 2030) and climate (1951-to-2000 and 2001-to-2050 GCM simulations) were designed. Effects of near-future climate change and 1999-to-2030 urban development on GBA extreme precipitation were then examined, using boundary conditions derived from GBA extreme rainfall events in the Geophysical Fluid Dynamics Laboratory Earth System Model (GFDL-ESM2M) historical and RCP8.5 simulations. Results show that climate change and rapid urban development forcing have comparable positive effects on the intensity as well as heavy hourly rainfall probability over the GBA urban area. Global warming tends to increase heavy rainfall probability (from 40 to 60 mm/h) by about 1.3 to 1.8 times, but at the same time suppress the probability of light rainfall (from 1 to 10 mm/h) by about 20%. Urban development increases urban rainfall probability within the whole range of intensity, with frequency for very heavy rainfall (> 90 mm/h) almost doubled. It is worth mentioning that impacts due to rapid urban development can be as important as global warming forcing in the near future in exacerbating hourly extreme rainfall over the GBA coastal megacity.

Does climate policy uncertainty affect Chinese stock market volatility?

Global warming forces policymakers to change climate policies to achieve global carbon neutrality targets. Although policy changes and developments affect financial asset price volatility, unpredictable climate policy changes make policy decisions less certain. This study investigates the spillover effects of climate policy uncertainty (CPU) on Chinese stock market volatility in the realized GARCH-MIDAS framework. To capture more information on asset price volatility, we further employ 5-min high-frequency data. The empirical results provide strong evidence to support that our strategy can successfully improve volatility forecasting accuracy. First, in-sample results indicate that CPU has a significant effect on stock price volatility. Second, out-of-sample tests confirm that the extended model that considers both CPU and high-frequency data exhibits the best predictive ability. In addition, various robustness tests strongly demonstrate our main findings. Thus, this paper demonstrates that weather effects exist in the stock market and reminds investors that they should pay more attention to climate policies in the current period of the climate crisis.

Global Sensitivity Analysis of Economic Model Predictive Longitudinal Motion Control of a Battery Electric Vehicle

Global warming forces the automotive industry to reduce real driving emissions and thus, its CO2 footprint. Besides maximizing the individual efficiency of powertrain components, there is also energy-saving potential in the choice of driving strategy. Many research works have noted the potential of model predictive control (MPC) methods to reduce energy consumption. However, this results in a complex control system with many parameters that affect the energy efficiency. Thus, an important question remains: how do these partially uncertain (system or controller) parameters influence the energy efficiency? In this article, a global variance-based sensitivity analysis method is used to answer this question. Therefore, a detailed powertrain model controlled by a longitudinal nonlinear MPC (NMPC) is developed and parameterized. Afterwards, a qualitative Morris screening is performed on this model, in order to reduce the parameter set. Subsequently, the remaining parameters are quantified using Generalized Sobol Indices, in order to take the time dependence of physical processes into account. This analysis reveals that the variations in vehicle mass, battery temperature, rolling resistance and auxiliary consumers have the greatest influence on the energy consumption. In contrast, the parameters of the NMPC only account for a maximum of 5% of the output variance.

Comparing the Influence of Global Warming and Urban Anthropogenic Heat on Extreme Precipitation in Urbanized Pearl River Delta Area Based on Dynamical Downscaling

AbstractThis study compares the impacts of global warming and intense urban anthropogenic heat (AH) on extreme hourly precipitation over the Pearl River Delta (PRD) megacity, located in coastal South China. Using the cloud‐resolving Weather Research and Forecasting (WRF) model coupled with the single‐layer urban canopy model (SLUCM), three downscaling experiments were carried out: the first (second) having zero (300 W/m2) as diurnal maximum AH values prescribed over PRD urban grids, under the current climate conditions. The third experiment with diurnal maximum AH of 300 W/m2 under future projected climate representative concentration pathway (RCP) 8.5. Boundary conditions were derived from PRD extreme rainfall episodes, identified from the Geophysical Fluid Dynamics Laboratory Earth System Model (GFDL‐ESM2M) historical and RCP8.5 runs. Global warming forcing leads to ∼20% to more than 100% increase in the probability of hourly precipitation with the magnitude of 20–100 mm/hr over urban locations. The enhancements from intense AH forcing were similar. However, two forcings have distinct signatures in modulating the thermodynamic environment. Warming due to AH is limited to the lowest 1 km above ground, while global warming warms up the whole troposphere. Intense AH results in enhanced convective available potential energy (CAPE) and reduced convective inhibition (CIN) within the megacity, allowing convection to be triggered more easily and with more vigor. On the other hand, global warming enhances CAPE and CIN, over both urban and rural areas. Our results highlight the different mechanisms of AH and global warming in exacerbating extreme urban rainfall, despite the similar impacts on the rainfall intensity.

Oceanic primary production decline halved in eddy-resolving simulations of global warming

Abstract. The decline in ocean primary production is one of the most alarming consequences of anthropogenic climate change. This decline could indeed lead to a decrease in marine biomass and fish catch, as highlighted by recent policy-relevant reports. Because of computational constraints, current Earth system models used to project ocean primary production under global warming scenarios have to parameterize flows occurring below the resolution of their computational grid (typically 1∘). To overcome these computational constraints, we use an ocean biogeochemical model in an idealized configuration representing a mid-latitude double-gyre circulation and perform global warming simulations under an increasing horizontal resolution (from 1 to 1/27∘) and under a large range of parameter values for the eddy parameterization employed in the coarse-resolution configuration. In line with projections from Earth system models, all our simulations project a marked decline in net primary production in response to the global warming forcing. Whereas this decline is only weakly sensitive to the eddy parameters in the eddy-parameterized coarse 1∘ resolution simulations, the simulated decline in primary production in the subpolar gyre is halved at the finest eddy-resolving resolution (−12 % at 1/27∘ vs. −26 % at 1∘) at the end of the 70-year-long global warming simulations. This difference stems from the high sensitivity of the sub-surface nutrient transport to model resolution. Although being only one piece of a much broader and more complicated response of the ocean to climate change, our results call for improved representation of the role of eddies in nutrient transport below the seasonal mixed layer to better constrain the future evolution of marine biomass and fish catch potential.

The IOD-ENSO precursory teleconnection over the tropical Indo-Pacific Ocean: dynamics and long-term trends under global warming

The dynamics of the teleconnection between the Indian Ocean Dipole (IOD) in the tropical Indian Ocean and El Nino-Southern Oscillation (ENSO) in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations. The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean, which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO. In comparison, lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant, suggesting the short memory of the atmospheric bridge. A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans. The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%–15% depending on the baroclinic modes. The IOD-ENSO teleconnection is found to get stronger in the past century or so. Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century, which is found sensitive to the global warming forcing.

A spurious warming trend in the NMME equatorial Pacific SST hindcasts

Using seasonal hindcasts of six different models participating in the North American Multimodel Ensemble project, the trend of the predicted sea surface temperature (SST) in the tropical Pacific for 1982–2014 at each lead month and its temporal evolution with respect to the lead month are investigated for all individual models. Since the coupled models are initialized with the observed ocean, atmosphere, land states from observation-based reanalysis, some of them using their own data assimilation process, one would expect that the observed SST trend is reasonably well captured in their seasonal predictions. However, although the observed SST features a weak-cooling trend for the 33-year period with La Nina-like spatial pattern in the tropical central-eastern Pacific all year round, it is demonstrated that all models having a time-dependent realistic concentration of greenhouse gases (GHG) display a warming trend in the equatorial Pacific that amplifies as the lead-time increases. In addition, these models’ behaviors are nearly independent of the starting month of the hindcasts although the growth rates of the trend vary with the lead month. This key characteristic of the forecasted SST trend in the equatorial Pacific is also identified in the NCAR CCSM3 hindcasts that have the GHG concentration for a fixed year. This suggests that a global warming forcing may not play a significant role in generating the spurious warming trend of the coupled models’ SST hindcasts in the tropical Pacific. This model SST trend in the tropical central-eastern Pacific, which is opposite to the observed one, causes a developing El Nino-like warming bias in the forecasted SST with its peak in boreal winter. Its implications for seasonal prediction are discussed.

Short- and long-range energy strategies for Japan and the world after the Fukushima nuclear accident

The accident at the Fukushima Dai-ichi nuclear power station in 2011 has caused profound effects on energy policies in Japan and worldwide. This is particularly because it occurred at the time of the growing awareness of global warming forcing measures towards decarbonised energy production, namely the use of fossil fuels has to be drastically reduced from the present level of more than 80% by 2050. A dilemma has now emerged because nuclear power, a CO2-free technology with proven large-scale energy production capability, lost confidence in many societies, especially in Japan and Germany. As a consequence, there is a world-wide effort now to expand renewable energies (REs), specifically photo-voltaic (PV) and wind power. However, the authors conjecture that PV and wind power can provide only up to a 40% share of the electricity production as long as sufficient storage is not available. Beyond this level, the technological (high grid power) and economic problems (large surplus production) grow. This is the result of the analysis of the growing use of REs in the electricity systems for Germany and Japan. The key element to overcome this situation is to develop suitable energy storage technologies. This is particularly necessary when electricity will become the main energy source because also transportation, process heat and heating, will be supplied by it. Facing the difficulty in replacing all fossil fuels in all countries with different technology standards, a rapid development of carbon capture and storage (CCS) might also be necessary. Therefore, for the short-range strategy up to 2050, all meaningful options have to be developed. For the long-range strategy beyond 2050, new energy sources (such as thermonuclear fusion, solar fuels and nuclear power—if inherently safe concepts will gain credibility of societies again), and large-scale energy storage systems based on novel concepts (such as large-capacity batteries and hydrogen) is required. It is acknowledged that the prediction of the future is difficult; therefore, the only insurance in this situation is by intensified research into all viable options.

Quantifying the Mean Sea Level Change at the Gulf of Finland Coast Caused by the Realistic Portion of the Global Warming Forcing

Quantifying the Mean Sea Level Change at the Gulf of Finland Coast Caused by the Realistic Portion of the Global Warming Forcing

Evidence for strengthening of the tropical Pacific Ocean surface wind speed during 1979–2001

Using multiple surface wind speed (SWS) data sets and trend empirical orthogonal function analysis, we have explored the trend in SWS associated with the large-scale tropical Pacific atmospheric circulation for the period 1979–2001. The present research provides a robust evidence of strengthening of the tropical Pacific Ocean SWS during this period and the magnitude is generally in line with the finding of Wentz et al. The strengthening in SWS is closely associated with the so-called La Nina-like sea surface temperature (SST) trend pattern rather than the changes in the ENSO, ENSO Modoki, or PDO. The present results, together with those from some recent climate model simulations, suggest that global warming forcing may have caused an intensification of SWS in the tropical Pacific Ocean by inducing the La Nina-like SST trend pattern due to ocean dynamics. Meanwhile, the strengthening in the tropical Pacific Ocean surface trade winds may also feedback to enhance the La Nina-like SST trend pattern under the positive wind-upwelling dynamic feedback mechanism.

Revisiting the trend of the tropical and subtropical Pacific surface latent heat flux during 1977–2006

[1] Using the Objectively Analyzed Air-Sea Fluxes data provided by the Woods Hole Oceanographic Institution and the trend empirical orthogonal function analysis method, we have investigated the trend of ocean surface latent heat flux (LHF) over the tropical and subtropical Pacific (100°E–70°W, 35°S–35°N) during the period 1977–2006. The present study suggests that the ocean surface LHF presents a large-scale upward trend pattern, and the identified positive surface LHF trend is closely associated with both the sea surface temperature (SST) warming and the surface wind speed strengthening. The SST increasing is the primary direct/local cause of the surface LHF trend, while the large-scale surface wind speed strengthening, ascribed to its contribution to the observed SST trend pattern, is an important indirect/nonlocal factor of the surface LHF trend. The present work also suggests that the coherent upward trends in surface LHF, surface wind speed, and SST should be in essence closely linked to the global warming forcing. To some extent, these results unify the two seemingly contradictory conclusions proposed previously by other researchers and attempt to help obtain a new insight into the causes of the positive basin-scale surface LHF trend.

What might the environmental policy of Tokyo Metropolitan Government achieve?

The summer was infernally hot this year in Japan. Many observation sites recorded highest temperatures since 1875. Official weather terms like ‘‘Nettaiya’’ (a sultry night when temperature does not drop below 25 C) and ‘‘Moushobi’’ (a day when temperature goes over 35 C) were reported on television and newspapers every day. Japan seems to have become a tropical country. If this is the harbinger of global warming, which needs to be prevented per Kyoto Protocol, adaptation seems to be of higher priority now than mitigation. The Kyoto Protocol, which set the numerical targets for greenhouse gas (GHG) emissions of developed countries, established the target period from 2008 to 2012. The GHG reduction target for Japan was 6% in 2010 compared to the benchmark year of 1990. However, the total GHG emission in 2008 was 1.282 billion ton according to the Ministry of the Environment. This total emission was higher by 1.6% than that in the benchmark year due to increased consumption of fossil fuels in the commercial/business and household sectors. Comparing this total emission with the counterpart in 2007, the amount in 2008 was reduced by 6.4% due to decreased fossil fuel use in the industrial sector. This decrease was congruent with the worldwide recession due to the financial crisis of 2008 leading to a decrease in energy demand in various sectors, especially industry. Various actions toward GHG emission reduction have been taken at the national level in Japan. In accordance with the Kyoto Protocol of the 1998 Conference of the Parties Third Framework Convention on Climate Change (COP3), Japan adopted, as the first step, promotion of measures through various public and private entities to cope with global warming. In 2008, the law was revised to achieve a numerical reduction target of 6% by the Kyoto Protocol. The main point of the revision was to achieve accurate estimation, reporting, and publicity of GHG reduction. The revision ordered companies (units of business and franchise) to estimate and report GHG emission. Given this revision, the law concerning the rational use of energy constituted after the second oil crisis was revised and has been enacted since April 2010. A company per se (including headquarter, branches, plants with annual energy usage of more than 1500 m of crude oil equivalent) needs to report the amount of energy usage to the Government and to be permitted as a designated energy management company. This regulation also targets companies with franchise chain system like Seven–Eleven. The designated company is required to employ a general manager on energy and a project practitioner on energy management. Besides, the revision of the law concerning the promotion of the measures to cope with global warming forces the local authorities, i.e., prefectural and city governments to enact an action plan for suppression of greenhouse gas emission according to natural and local conditions. In contrast to other local municipalities, the Tokyo Metropolitan Government (TMG) with a population of 130 million and gross regional product of 815 billion USD in 2006 has been independently working on the strategy of ‘‘Environmental Revolution’’ —action toward an environmentally advanced city for a sustainable society. One exemplary action is regulating diesel cars, directly led by Shintaro Ishihara, the governor of TMG. On Aug 27 1999, the governor Ishihara commenced an active discussion to change the minds of citizens on the use M. Hosomi (&) Department of Chemical Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan e-mail: hosomi@cc.tuat.ac.jp

Net air–sea surface heat flux during 1984–2004 over the North Pacific and North Atlantic oceans (10°N–50°N): annual mean climatology and trend

Using the Objectively Analyzed air–sea Fluxes dataset (and also the National Oceanography Centre Southampton Flux Dataset v2.0), we examined both the annual mean climatology and trend of net air–sea surface heat flux (Qnet) for 1984–2004 over the North Pacific and North Atlantic oceans (10°N–50°N). The annual mean Qnet climatology shows that oceans obtain the positive Qnet over much of the North Pacific and North Atlantic oceans. Exceptions are the regions of western boundary currents (WBCs) including the Kuroshio and its extension off Japan and the Gulf Stream off the USA and its extension, where oceans release lots of heat into the atmosphere, mainly ascribed to the large surface turbulent heat loss. The statistically significant negative Qnet trends occurred in the WBCs, while the statistically significant positive Qnet trends appeared in the central basins of Northern Subtropical Oceans (CNSOs) including the central basin of Northern Subtropical Pacific and the central basin of Northern Subtropical Atlantic. These indentified Qnet trends, which are independent of both El Nino-Southern Oscillation (ENSO) and ENSO Modoki but closely related to global warming forcing, are predominately due to the statistically significant surface latent heat (LH) trends. Over the WBCs, the positive LH trends are mainly induced by the sea surface temperature increasing, indicating the ocean forcing upon overlying atmosphere. In contrast, over the CNSOs, the negative LH trends are mainly caused by the near-surface air specific humidity increasing, indicative of an oceanic response to overlying atmospheric forcing.

Sensitivity of arctic summer sea ice coverage to global warming forcing: towards reducing uncertainty in arctic climate change projections

Sensitivity of arctic summer sea ice coverage to global warming forcing: towards reducing uncertainty in arctic climate change projections

Sensitivity of arctic summer sea ice coverage to global warming forcing: towards reducing uncertainty in arctic climate change projections

Substantial uncertainties have emerged in Arctic climate change projections by the fourth Intergovernmental Panel on Climate Change assessment report climate models. In particular, the models as a group considerably underestimate the recent accelerating sea ice reduction. To better understand the uncertainties, we evaluated sensitivities of summer sea ice coverage to global warming forcing in models and observations. The result suggests that the uncertainties result from the large range of sensitivities involved in the computation of sea ice mass balance by the climate models, specifically with the changes in sea ice area (SIA) ranging from 0.09 × 10 6 to −1.23 × 10 6 km 2 in response to 1.0 K increase of air temperature. The sensitivities also vary largely across ensemble members in the same model, indicating impacts of initial condition on evolution of feedback strength with model integrations. Through observationally constraining, the selected model runs by the sensitivity analysis well captured the observed changes in SIA and surface air temperatures and greatly reduced their future projection uncertainties to a certain range from the currently announced one. The projected ice-free summer Arctic Ocean may occur as early as in the late 2030s using a criterion of 80% SIA loss and the Arctic regional mean surface air temperature will be likely increased by 8.5 ± 2.5 °C in winter and 3.7 ± 0.9 °C in summer by the end of this century.

Sensitivity of arctic summer sea ice coverage to global warming forcing: towards reducing uncertainty in arctic climate change projections

Substantial uncertainties have emerged in Arctic climate change projections by the fourth Intergovernmental Panel on Climate Change assessment report climate models. In particular, the models as a group considerably underestimate the recent accelerating sea ice reduction. To better understand the uncertainties, we evaluated sensitivities of summer sea ice coverage to global warming forcing in models and observations. The result suggests that the uncertainties result from the large range of sensitivities involved in the computation of sea ice mass balance by the climate models, specifically with the changes in sea ice area (SIA) ranging from 0.09 × 106 to −1.23 × 106 km2 in response to 1.0 K increase of air temperature. The sensitivities also vary largely across ensemble members in the same model, indicating impacts of initial condition on evolution of feedback strength with model integrations. Through observationally constraining, the selected model runs by the sensitivity analysis well captured the observed changes in SIA and surface air temperatures and greatly reduced their future projection uncertainties to a certain range from the currently announced one. The projected ice-free summer Arctic Ocean may occur as early as in the late 2030s using a criterion of 80% SIA loss and the Arctic regional mean surface air temperature will be likely increased by 8.5 ± 2.5 ◦C in winter and 3.7 ± 0.9 ◦C in summer by the end of this century.

Greenhouse gas flux from cropland and restored wetlands in the Prairie Pothole Region

It has been well documented that restored wetlands in the Prairie Pothole Region of North America do store carbon. However, the net benefit of carbon sequestration in wetlands in terms of a reduction in global warming forcing has often been questioned because of potentially greater emissions of greenhouse gases (GHGs) such as nitrous oxide (N 2O) and methane (CH 4). We compared gas emissions (N 2O, CH 4, carbon dioxide [CO 2]) and soil moisture and temperature from eight cropland and eight restored grassland wetlands in the Prairie Pothole Region from May to October, 2003, to better understand the atmospheric carbon mitigation potential of restored wetlands. Results show that carbon dioxide contributed the most (90%) to net-GHG flux, followed by CH 4 (9%) and N 2O (1%). Fluxes of N 2O, CH 4, CO 2, and their combined global warming potential (CO 2 equivalents) did not significantly differ between cropland and grassland wetlands. The seasonal pattern in flux was similar in cropland and grassland wetlands with peak emissions of N 2O and CH 4 occurring when soil water-filled pore space (WFPS) was 40–60% and >60%, respectively; negative CH 4 fluxes were observed when WFPS approached 40%. Negative CH 4 fluxes from grassland wetlands occurred earlier in the season and were more pronounced than those from cropland sites because WFPS declined more rapidly in grassland wetlands; this decline was likely due to higher infiltration and evapotranspiration rates associated with grasslands. Our results suggest that restoring cropland wetlands does not result in greater emissions of N 2O and CH 4, and therefore would not offset potential soil carbon sequestration. These findings, however, are limited to a small sample of seasonal wetlands with relatively short hydroperiods. A more comprehensive assessment of the GHG mitigation potential of restored wetlands should include a diversity of wetland types and land-use practices and consider the impact of variable climatic cycles that affect wetland hydrology.