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Atmospheric methane grew very rapidly in 2014 (12.7 ± 0.5 ppb/year), 2015 (10.1 ± 0.7 ppb/year), 2016 (7.0 ± 0.7 ppb/year), and 2017 (7.7 ± 0.7 ppb/year), at rates not observed since the 1980s. The increase in the methane burden began in 2007, with the mean global mole fraction in remote surface background air rising from about 1,775 ppb in 2006 to 1,850 ppb in 2017. Simultaneously the 13C/12C isotopic ratio (expressed as δ13CCH4) has shifted, has shifted, now trending negative for more than a decade. The causes of methane's recent mole fraction increase are therefore either a change in the relative proportions (and totals) of emissions from biogenic and thermogenic and pyrogenic sources, especially in the tropics and subtropics, or a decline in the atmospheric sink of methane, or both. Unfortunately, with limited measurement data sets, it is not currently possible to be more definitive. The climate warming impact of the observed methane increase over the past decade, if continued at >5 ppb/year in the coming decades, is sufficient to challenge the Paris Agreement, which requires sharp cuts in the atmospheric methane burden. However, anthropogenic methane emissions are relatively very large and thus offer attractive targets for rapid reduction, which are essential if the Paris Agreement aims are to be attained. The rise in atmospheric methane (CH4), which began in 2007, accelerated in the past 4 years. The growth has been worldwide, especially in the tropics and northern midlatitudes. With the rise has come a shift in the carbon isotope ratio of the methane. The causes of the rise are not fully understood, and may include increased emissions and perhaps a decline in the destruction of methane in the air. Methane's increase since 2007 was not expected in future greenhouse gas scenarios compliant with the targets of the Paris Agreement, and if the increase continues at the same rates it may become very difficult to meet the Paris goals. There is now urgent need to reduce methane emissions, especially from the fossil fuel industry. Atmospheric methane is rising; its carbon isotopic ratio has become more depleted in C‐13The possible causes of the change include an increase in emissions, with changing relative proportions of source inputs, or a decline in methane destruction, or bothIf this rise continues, there are significant consequences for the UN Paris Agreement

We use a Lagrangian chemical transport model with a Monte Carlo approach to determine impacts of kinetic rate uncertainties on simulated concentrations of ozone, NOyand OH in a high‐altitude biomass burning plume and a low‐level industrial pollution plume undergoing long‐range transport. Uncertainties in kinetic rate constants yield 10–12 ppbv (5th to 95th percentile) uncertainty in the ozone concentration, dominated by reactions that cycle NO and NO2, control NOxconversion to NOyreservoir species, and key reactions contributing to O3loss (O(1D) + H2O, HO2+ O3). Our results imply that better understanding of the peroxyacetylnitrate (PAN) thermal decomposition constant is key to predicting large‐scale O3production from fire emissions and uncertainty in the reaction of NO + O3at low temperatures is particularly important for both the anthropogenic and biomass burning plumes. The highlighted reactions serve as a useful template for targeting new laboratory experiments aimed at reducing uncertainties in our understanding of tropospheric O3photochemistry. Computer models used to assess and predict how air pollution changes in response to emissions, and how it affects climate and human health, rely on information from laboratory experiments to prescribe the rates at which different atmospheric chemical species react. This laboratory information has uncertainties associated with experimental limitations or constraints. We show how these uncertainties affect confidence in model predictions of tropospheric ozone in two pollution plumes. Ozone is a key air pollutant, harmful to human health and vegetation, as well as a climate warming agent. We identify key reactions that lead to large uncertainty in simulated ozone and demonstrate the importance of low confidence in some reactions at low temperatures in driving large portion of ozone uncertainty. Our work serves as a key basis from which to motivate future lab experiments aimed at reducing uncertainty in our understanding of tropospheric ozone. Uncertainty in simulated ozone is dominated by a few key reactions in both biomass burning and anthropogenic pollution plumesUncertainty in PAN decomposition is key to controlling model ensemble spread in ozone change in biomass burning air massesIncreased uncertainty at low temperatures results in a large increase in ensemble ozone spread, particularly from the NO + O3reaction

Airborne measurements of a methane (CH4) plume over the North Sea from August 2013 are analyzed. The plume was only observed downwind of circumnavigated gas fields, and three methods are used to determine its source. First, a mass balance calculation assuming a gas field source gives a CH4emission rate between 2.5 ± 0.8×104and 4.6 ± 1.5×104kg h−1. This would be greater than the industry's reported 0.5% leak rate if it were emitting for more than half the time. Second, annual average UK CH4emissions are combined with an atmospheric dispersion model to create pseudo‐observations. Clean air from the North Atlantic passed over mainland UK, picking up anthropogenic emissions. To best explain the observed plume using pseudo‐observations, an additional North Sea source from the gas rigs area is added. Third, the δ13C‐CH4from the plume is shown to be −53‰, which is lighter than fossil gas but heavier than the UK average emission. We conclude that either an additional small‐area mainland source is needed, combined with temporal variability in emission or transport in small‐scale meteorological features. Alternatively, a combination of additional sources that are at least 75% from the mainland (−58‰) and up to 25% from the North Sea gas rigs area (−32‰) would explain the measurements. Had the isotopic analysis not been performed, the likely conclusion would have been of a gas field source of CH4. This demonstrates the limitation of analyzing mole fractions alone, as the simplest explanation is rejected based on analysis of isotopic data. In the study, we have analyzed aircraft data to try and identify the source of a plume of methane observed over the North Sea. The flight circuited North Sea gas fields with the aim of intercepting any fugitive methane. Initial analysis of the amount of methane present and its location suggested that the methane was being emitted from the gas field area, and this was supported by dispersion modeling of the case. However, analysis of carbon isotopes in methane revealed that fugitive gas could not have been the primary component of the plume. As methane is often measured without analysis of its carbon isotopes, the authors feel that this is an important cautionary tale. We present our analysis of this case study with recommendations for how best to conduct such analyses in the future to try and avoid potential misdiagnosis of methane plume sources. Three methods are used to analyze a methane plume observed over the North SeaOnly with use of all three methods can the source of the plume be understoodMeasurement of carbon isotopes is essential for source identification, given limitations to the model and the extent of the measurements

A reprint of the article "On the Topic: Michfest Memories--Part 2," which appeared in the 2015 Fall/Winter issue of "Forward Pass" magazine of the International Women's Flag Football Association (IWFFA), is presented.

From 2007 to 2013, the globally averaged mole fraction of methane in the atmosphere increased by 5.7?±?1.2?ppb?yr-1. Simultaneously, d13CCH4(a measure of the 13C/12C isotope ratio in methane) has shifted to significantly more negative values since 2007. Growth was extreme in 2014, at 12.5?±?0.4?ppb, with a further shift to more negative values being observed at most latitudes. The isotopic evidence presented here suggests that the methane rise was dominated by significant increases in biogenic methane emissions, particularly in the tropics, for example, from expansion of tropical wetlands in years with strongly positive rainfall anomalies or emissions from increased agricultural sources such as ruminants and rice paddies. Changes in the removal rate of methane by the OH radical have not been seen in other tracers of atmospheric chemistry and do not appear to explain short-term variations in methane. Fossil fuel emissions may also have grown, but the sustained shift to more 13C-depleted values and its significant interannual variability, and the tropical and Southern Hemisphere loci of post-2007 growth, both indicate that fossil fuel emissions have not been the dominant factor driving the increase. A major cause of increased tropical wetland and tropical agricultural methane emissions, the likely major contributors to growth, may be their responses to meteorological change. Atmospheric methane, which is a powerful greenhouse gas, is increasing rapidly. In the 20th century, methane growth was primarily driven by emissions from fossil fuel sources, such as the natural gas industry and coal mining. Then, in the early years of the 21st century, came a period of stability in methane. However, since 2007, growth has resumed, with especially strong growth in 2014. Evidence from carbon isotopes implies that the primary cause of the new growth is an increase in biogenic emissions, probably from wetlands and also agricultural sources, such as rice fields and cattle. The evidence presented in this research study, from a wide range of measurement sites both in the northern and southern hemispheres, suggests increased tropical emissions, for example from tropical wetlands, may be a principal cause of the global rise in methane. Contributions to the growth may also come from agricultural sources and perhaps some fossil fuel emissions also. Atmospheric methane is growing rapidlyIsotopic evidence implies that the growth is driven by biogenic sourcesGrowth is dominated by tropical sources

The complex permittivity of bulk ceramic ferroelectric of nominal composition PbZr0.4Ti0.6O3was measured in the range 0.2–2 THz using transmission time-domain spectroscopy. The results indicate strong absorption and dispersion in this frequency range as often seen in highly disordered and polar materials. The results are compared to equivalent thin film data in the literature, and significant differences in the real and imaginary permittivity suggest that substrate clamping and degree of polarisation of the ferroelectric thin film materials affect dielectric properties even at these high frequencies.

We find that summer methane (CH4) release from seabed sediments west of Svalbard substantially increases CH4concentrations in the ocean but has limited influence on the atmospheric CH4levels. Our conclusion stems from complementary measurements at the seafloor, in the ocean, and in the atmosphere from land‐based, ship and aircraft platforms during a summer campaign in 2014. We detected high concentrations of dissolved CH4in the ocean above the seafloor with a sharp decrease above the pycnocline. Model approaches taking potential CH4emissions from both dissolved and bubble‐released CH4from a larger region into account reveal a maximum flux compatible with the observed atmospheric CH4mixing ratios of 2.4–3.8 nmol m−2s−1. This is too low to have an impact on the atmospheric summer CH4budget in the year 2014. Long‐term ocean observatories may shed light on the complex variations of Arctic CH4cycles throughout the year. Summer CH4release from seabed sediments west of Svalbard substantially increases concentrations in the ocean, but not in the atmosphereThe modeled flux is constrained to a maximum of 2.4 to 3.8 nmol m−2s−1, compatible with the observed atmospheric CH4from 20 June to 1 August 2014Any ocean‐atmosphere flux of the CH4accumulated beneath the pycnocline may only occur if physical processes remove this dynamic barrier