Impact of a global warming on biospheric sources of methane and its climatic consequences (original) (raw)

Atmospheric methane and global change

Earth-science Reviews, 2002

Methane (CH 4 ) is the most abundant organic trace gas in the atmosphere. In the distant past, variations in natural sources of methane were responsible for trends in atmospheric methane levels recorded in ice cores. Since the 1700s, rapidly growing human activities, particularly in the areas of agriculture, fossil fuel use, and waste disposal, have more than doubled methane emissions. Atmospheric methane concentrations have increased by a factor of 2 -3 in response to this increase, and continue to rise. These increasing concentrations have raised concern due to their potential effects on atmospheric chemistry and climate. Methane is important to both tropospheric and stratospheric chemistry, significantly affecting levels of ozone, water vapor, the hydroxyl radical, and numerous other compounds. In addition, methane is currently the second most important greenhouse gas emitted from human activities. On a per molecule basis, it is much more effective a greenhouse gas than additional CO 2 . In this review, we examine past trends in the concentration of methane in the atmosphere, the sources and sinks that determine its growth rate, and the factors that will affect its growth rate in the future. We also present current understanding of the effects of methane on atmospheric chemistry, and examine the direct and indirect impacts of atmospheric methane on climate. D

Estimates of changes in the rate of methane sink from the atmosphere under climate warming

Izvestiya, Atmospheric and Oceanic Physics, 2012

The temperature dependence of the methane oxidation rate is estimated. The methane lifetime in the atmosphere is shown to decrease by about 3% from 1900 to 2005. The overwhelming fraction of the total methane content is removed from the atmosphere at intratropical latitudes during the daytime. The methane oxidation rate growth due to the temperature increase in the troposphere generates negative feedback in the methane cycle and, accordingly, climatic feedback with the same sign. According to the estimates performed, the halt in methane concentration growth in the atmosphere observed in recent years can be associated with a decrease in the lifetime of methane in the atmosphere. According to the results of numerical experiments with the climatic model of the Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS), the climatic effect of negative feedback of the tropospheric temperature and the methane lifetime in the atmosphere is not large and is comparable with the climatic forcing of the methane emission growth from bog ecosystems.

Methane and Global Environmental Change

Annual Review of Environment and Resources, 2018

Global atmospheric methane concentrations have continued to rise in recent years, having already more than doubled since the Industrial Revolution. Further environmental change, especially climate change, in the twenty-first century has the potential to radically alter global methane fluxes. Importantly, changes in temperature, precipitation, and net primary production may induce positive climate feedback effects in dominant natural methane sources such as wetlands, soils, and aquatic ecosystems. Anthropogenic methane sources may also be impacted, with a risk of enhanced emissions from the energy, agriculture, and waste sectors. Here, we review the global sources of methane, the trends in fluxes by source and sector, and their possible evolution in response to future environmental change. We discuss ongoing uncertainties in flux estimation and projection, and highlight the great potential for multisector methane mitigation as part of wider global climate change policy.

Sources and sinks of methane: future concentrations and impact on global warming

2005

There has been an average increase in the surface temperature of the earth by 0.6 ± 0.2ºC over the 20 th century (IPCC, 2001). This increase in the surface temperature of the earth is attributed to the increase in the greenhouse gases in the atmosphere, responsible for trapping outgoing heat radiation. Industrialization and the increase in anthropogenic activities are the causes of increase of these gases. Methane (CH 4) is the most important greenhouse gas after carbon dioxide (CO 2).The increase in atmospheric CO2 can be attributed due to increase in the use of fossil fuels over the last 150 years. Methane, whose atmospheric concentrations are now nearly 2.5 times of what they were in pre-industrial times, has a variety of anthropogenic and natural sources. This work is an effort to document the anthropogenic sources of methane since 1960, namely, methane emissions from the use of fossil fuel, rice agriculture, domestic ruminants, biomass burning and waste disposal and handling. A model was created using the sources and sinks of methane and was used to predict the future concentrations of methane up to 2030. considering the atmosphere as a semi-batch reactor. Finally, this predicted concentration of methane was used to determine the surface temperature increase caused due to increase in the atmospheric methane concentrations and was determined to be 0.135 K.

Changing concentration, lifetime and climate forcing of atmospheric methane

2002

Previous studies on ice core analyses and recent in situ measurements have shown that CH 4 has increased from about 0.75 to 1.73 mmol/mol during the past 150 years. Here, we review sources and sink estimates and we present global 3D model calculations, showing that the main features of the global CH 4 distribution are well represented.

An emissions-based view of climate forcing by methane and tropospheric ozone

Geophysical Research Letters, 2005

1] We simulate atmospheric composition changes in response to increased methane and tropospheric ozone precursor emissions from the preindustrial to present-day in a coupled chemistry-aerosol-climate model. The global annual average composition response to all emission changes is within 10% of the sum of the responses to individual emissions types, a more policy-relevant quantity. This small non-linearity between emission types permits attribution of past global mean methane and ozone radiative forcings to specific emissions despite the well-known nonlinear response to emissions of a single type. The emissionsbased view indicates that methane emissions have contributed a forcing of 0.8−0.9WmAˋ2,nearlydoubletheabundance−basedvalue,whiletheforcingfromotherozoneprecursorshasbeenquitesmall(0.8-0.9 W m À2 , nearly double the abundance-based value, while the forcing from other ozone precursors has been quite small (0.8−0.9WmAˋ2,nearlydoubletheabundance−basedvalue,whiletheforcingfromotherozoneprecursorshasbeenquitesmall(À0.

Climate effects of atmospheric methane

Chemosphere, 1993

We discuss the role of the concentration increase of atmospheric CH4 (currently ~ 0.8% yr -1) in climate change, including effects through chemical feedbacks, notably through formation of 03 and stratospheric H2 0, and reduction of OH levels, which increases the lifetime of CH4. We present results of simulations with a coupled 1-D radiative-convective model, which includes chemical and radiative processes in the troposphere and stratosphere, and which treats both hemispheres separately. Our results deviate appreciably from those reported in earlier studies; the reason for this is discussed in detail. The current climate forcing by CH4 (excluding indirect chemical effects) is 26 times that of CO2 (calculated on a mole C02/mole CH4 basis). A recently introduced quantity to express the time integrated effect of CH4 relative to that of CO2 over a given time interval is the global warming potential (GWP). We assess that the GWP of CH4, including chemical feedbacks, over a 10 year integration period is 26.9 (mole CO2/mole CH4), decreasing to 7.5 for a time horizon of 100 years. Considering that the use of fossil fuels is associated with emissions of both CO2 and CH4, we evaluated the climatic consequences of switching from coal or oil to natural gas. We conclude that, if the fractional gas leakage from production and distribution of natural gas is below 4.3 -5.7%, a switch from coal to natural gas as energy source would reduce the rate of climate warming. The use of gas would be preferable over the use of oil (from a climate point of view), if the fractional gas leakage is less than 2.4 -2.9%. The ranges express uncertainties in CH4 releases from coal and oil production.

Global Methane Emissions from Terrestrial Plants

Environmental Science & Technology, 2007

Contribution to the greenhouse effect Importance of methane in Earth's atmosphere  OH -The most important oxidizing species is the hydroxyl radical (OH). It is extremely reactive and able to oxidize most of the chemicals found in the troposphere. The hydroxyl radical is therefore known as the 'detergent of the atmosphere'.

Atmospheric Ozone and Methane in a Changing Climate

Atmosphere, 2014

Ozone and methane are chemically active climate-forcing agents affected by climate-chemistry interactions in the atmosphere. Key chemical reactions and processes affecting ozone and methane are presented. It is shown that climate-chemistry interactions have a significant impact on the two compounds. Ozone, which is a secondary compound in the atmosphere, produced and broken down mainly in the troposphere and stratosphre through chemical reactions involving atomic oxygen (O), NOx compounds (NO, NO 2 ), CO, hydrogen radicals (OH, HO 2 ), volatile organic compounds (VOC) and chlorine (Cl, ClO) and bromine (Br, BrO). Ozone is broken down through changes in the atmospheric distribution of the afore mentioned compounds. Methane is a primary compound emitted from different sources (wetlands, rice production, livestock, mining, oil and gas production and landfills).Methane is broken down by the hydroxyl radical (OH). OH is significantly affected by methane emissions, defined by the feedback factor,