Projections of atmospheric methane concentrations (ppb) for the four Representative Concentration Pathway (RCP) scenarios and observed globally averaged atmospheric abundance at marine boundary layer sites from the NOAA network (black, Dlugockenky 2016). Tropospheric concentrations from RCP models have been scaled to fit surface observations. Graphic: Saunois, et al., 2016 / Environmental Research Letters

By Stephanie Smail
12 December 2016

(ABC) – Global methane gas emissions are growing at the fastest rate in decades and food production could be to blame, new analysis has revealed.

Nearly 100 scientists from around the world have compiled data for the Global Methane Budget, which shows the biggest spike in methane concentrations in the atmosphere in 20 years.

CSIRO researcher Dr Pep Canadell said it was the most comprehensive modelling to date and revealed a potentially dangerous climate wildcard.

"And what we've found in the past three years the emissions are growing even faster."

Dr Canadell said the figures showed efforts to feed the world's growing population were contributing to the spike.

"We think the increase in food production globally has led to the increase in emissions, which has contributed to the higher concentration of methane in the atmosphere," he said.

"We found the most dominant driver of emissions growth was agriculture, with livestock." […]

Dr Canadell said research showed carbon dioxide was responsible for 80 per cent of all increased warming from human activity. [more]

Methane emissions spiking, global research finds


By Rob Jordan
11 December 2016

(Stanford Woods Institute) – A major opportunity for avoiding climate change’s worst impacts lies in reducing methane emissions, particularly from food production, according to a pair of new studies.

The parallel papers, published Dec. 12 in the journals Earth System Science Data and Environmental Research Letters, report that emissions of methane have jumped dramatically in recent years and are approaching an internationally recognized worst-case scenario for greenhouse gas emissions. Unchecked, this increase could see temperatures rise as much as 6 degrees Fahrenheit (4 degrees Celsius), speeding sea level rise and more extreme weather.

The papers also lay out recommendations for curbing methane emissions in the future, with a focus on food production, which makes up about one third of total man-made emissions. The papers were co-authored by Rob Jackson, chair of Stanford’s Earth System Science Department and head of the Global Carbon Project, which organized the work.

The alarming increase in methane draws attention to managing those emissions for climate change mitigation. While most mitigation efforts have focused on carbon dioxide, the more common greenhouse gas, methane’s warming potential is about 28 times greater on a 100-year horizon, and its lifespan in the atmosphere is much shorter. In other words, it can do major damage, but getting it under control could tip the climate change equation relatively rapidly.

“Methane presents the best opportunity to slow climate change quickly,” said Jackson. “Carbon dioxide has a longer reach, but methane strikes faster.”

The study comes in the wake of congressional Republicans’ stated intentions to rescind methane-limiting standards for the natural gas industry.

Surprising findings

The paper’s findings are particularly surprising because methane concentrations were stagnant for years up until a decade ago. And unlike carbon dioxide, the bulk of methane emissions are human-driven. Chief among those, according to the analysis, are agricultural sources such as livestock, which emit methane through bodily functions and manure, and rice fields, which emit methane when flooded. People are responsible for 60 percent of all methane emissions globally.

Despite a boom in U.S. oil and gas production, the study’s authors see rising fossil fuel emissions playing a secondary role compared to agriculture for the global methane increase. There is a lesson to learn, Jackson said. “The fossil fuel industry has received most of the attention in recent years. Agricultural emissions need similar scrutiny.”

Reducing uncertainties

Natural sources of methane, which account for 40 percent of all methane emissions, are more uncertain than human-driven ones. Examples include methane leaking out of natural faults and seeping on the ocean floor, and the potential for increased emissions as permafrost warms. Another research area includes studying the short-lived radicals that destroy methane in the atmosphere.

Because of the evolving nature of this knowledge, the international group of scientists behind the study plans to update the methane budget every two years. The effort is under the umbrella of the Global Carbon Project, an initiative headed by Jackson that releases an annual global carbon budget. The group’s most recent carbon budget shows concentrations of carbon dioxide have been largely flat for the past three years – a finding that reinforces the importance of methane management.

Working toward solutions

To resolve discrepancies on the magnitude of emissions and regional trends, Jackson and his co-authors recommend more accurate partitioning of methane emissions and sinks by region and process and more interactions among scientific groups developing emissions inventories.

Possible solutions for agriculture include breeding rice to require less flooding, altering feed for livestock to lessen intestinal processes that create methane, promoting less meat-intensive diets and deploying more farm bio-digesters. Opportunities in other areas include venting and flaring of methane in coal mines, detecting and removing natural gas leaks from oil and gas drilling operations and covering landfills to capture methane emissions.

In the meantime, the authors call for urgent attention to quantify and reduce methane emissions, stressing mitigation’s rapid climate benefits and economic, health and agricultural co-benefits. Jackson says, “We still need to cut carbon dioxide emissions, but cutting methane provides complementary benefits for climate, economies and human health.”

Jackson and colleagues received a recent grant from the Gordon and Betty Moore Foundation to further analyze global methane emissions and sinks.

Jackson is a senior fellow at the Stanford Woods Institute for the Environment and the Precourt Institute for Energy.

Methane from food production could be wildcard in combating climate change, Stanford scientist says


ABSTRACT: Unlike CO2, atmospheric methane concentrations are rising faster than at any time in the past two decades and, since 2014, are now approaching the most greenhouse-gas-intensive scenarios. The reasons for this renewed growth are still unclear, primarily because of uncertainties in the global methane budget. New analysis suggests that the recent rapid rise in global methane concentrations is predominantly biogenic-most likely from agriculture-with smaller contributions from fossil fuel use and possibly wetlands. Additional attention is urgently needed to quantify and reduce methane emissions. Methane mitigation offers rapid climate benefits and economic, health and agricultural co-benefits that are highly complementary to CO2 mitigation.

The growing role of methane in anthropogenic climate change


ABSTRACT: The global methane (CH4) budget is becoming an increasingly important component for managing realistic pathways to mitigate climate change. This relevance, due to a shorter atmospheric lifetime and a stronger warming potential than carbon dioxide, is challenged by the still unexplained changes of atmospheric CH4 over the past decade. Emissions and concentrations of CH4 are continuing to increase, making CH4 the second most important human-induced greenhouse gas after carbon dioxide. Two major difficulties in reducing uncertainties come from the large variety of diffusive CH4 sources that overlap geographically, and from the destruction of CH4 by the very short-lived hydroxyl radical (OH). To address these difficulties, we have established a consortium of multi-disciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate research on the methane cycle, and producing regular (∼ biennial) updates of the global methane budget. This consortium includes atmospheric physicists and chemists, biogeochemists of surface and marine emissions, and socio-economists who study anthropogenic emissions. Following Kirschke et al. (2013), we propose here the first version of a living review paper that integrates results of top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models, inventories and data-driven approaches (including process-based models for estimating land surface emissions and atmospheric chemistry, and inventories for anthropogenic emissions, data-driven extrapolations).
For the 2003–2012 decade, global methane emissions are estimated by top-down inversions at 558 Tg CH4 yr−1, range 540–568. About 60 % of global emissions are anthropogenic (range 50–65 %). Since 2010, the bottom-up global emission inventories have been closer to methane emissions in the most carbon-intensive Representative Concentrations Pathway (RCP8.5) and higher than all other RCP scenarios. Bottom-up approaches suggest larger global emissions (736 Tg CH4 yr−1, range 596–884) mostly because of larger natural emissions from individual sources such as inland waters, natural wetlands and geological sources. Considering the atmospheric constraints on the top-down budget, it is likely that some of the individual emissions reported by the bottom-up approaches are overestimated, leading to too large global emissions. Latitudinal data from top-down emissions indicate a predominance of tropical emissions (∼ 64 % of the global budget, < 30° N) as compared to mid (∼ 32 %, 30–60° N) and high northern latitudes (∼ 4 %, 60–90° N). Top-down inversions consistently infer lower emissions in China (∼ 58 Tg CH4 yr−1, range 51–72, −14 %) and higher emissions in Africa (86 Tg CH4 yr−1, range 73–108, +19 %) than bottom-up values used as prior estimates. Overall, uncertainties for anthropogenic emissions appear smaller than those from natural sources, and the uncertainties on source categories appear larger for top-down inversions than for bottom-up inventories and models.
The most important source of uncertainty on the methane budget is attributable to emissions from wetland and other inland waters. We show that the wetland extent could contribute 30–40 % on the estimated range for wetland emissions. Other priorities for improving the methane budget include the following: (i) the development of process-based models for inland-water emissions, (ii) the intensification of methane observations at local scale (flux measurements) to constrain bottom-up land surface models, and at regional scale (surface networks and satellites) to constrain top-down inversions, (iii) improvements in the estimation of atmospheric loss by OH, and (iv) improvements of the transport models integrated in top-down inversions. The data presented here can be downloaded from the Carbon Dioxide Information Analysis Center (http://doi.org/10.3334/CDIAC/GLOBAL_METHANE_BUDGET_2016_V1.1) and the Global Carbon Project.

The global methane budget 2000–2012

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