Publications

Meteorological and air quality data. Al Shahama. Abu Dhabi Air Quality Management Study. NILU OR

Bøhler, T.; Gamal, K.; Haugsbakk, I.; Wasseng, J.

Meteorological and air quality data. Hamdan/Al Miroor Crossing. Abu Dhabi Air Quality Management Study. NILU OR

Bøhler, T.; Gamal, K.; Haugsbakk, I.; Wasseng, J.

Meteorological and air quality data. Ruwais. Abu Dhabi Air Quality Management Study. NILU OR

Bøhler, T.; Gamal, K.; Haugsbakk, I.; Wasseng, J.

Meteorological data for air pollution assessment. NILU F

Sivertsen, B.

Methane at Svalbard and over the European Arctic Ocean

Methane (CH₄) is a powerful greenhouse gas. Its atmospheric mixing ratios have been increasing since 2005. Therefore, quantification of CH₄ sources is essential for effective climate change mitigation. Here we report observations of the CH₄ mixing ratios measured at the Zeppelin Observatory (Svalbard) in the Arctic and aboard the research vessel (RV) Helmer Hanssen over the Arctic Ocean from June 2014 to December 2016, as well as the long-term CH₄ trend measured at the Zeppelin Observatory from 2001 to 2017. We investigated areas over the European Arctic Ocean to identify possible hotspot regions emitting CH₄ from the ocean to the atmosphere, and used state-of-the-art modelling (FLEXPART) combined with updated emission inventories to identify CH₄ sources. Furthermore, we collected air samples in the region as well as samples of gas hydrates, obtained from the sea floor, which we analysed using a new technique whereby hydrate gases are sampled directly into evacuated canisters. Using this new methodology, we evaluated the suitability of ethane and isotopic signatures (δ¹³C in CH₄) as tracers for ocean-to-atmosphere CH₄ emission. We found that the average methane / light hydrocarbon (ethane and propane) ratio is an order of magnitude higher for the same sediment samples using our new methodology compared to previously reported values, 2379.95 vs. 460.06, respectively. Meanwhile, we show that the mean atmospheric CH₄ mixing ratio in the Arctic increased by 5.9±0.38 parts per billion by volume (ppb) per year (yr⁻¹) from 2001 to 2017 and ∼8 pbb yr⁻¹ since 2008, similar to the global trend of ∼ 7–8 ppb yr⁻¹. Most large excursions from the baseline CH₄ mixing ratio over the European Arctic Ocean are due to long-range transport from land-based sources, lending confidence to the present inventories for high-latitude CH₄ emissions. However, we also identify a potential hotspot region with ocean–atmosphere CH₄ flux north of Svalbard (80.4∘ N, 12.8∘ E) of up to 26 nmol m⁻²s⁻¹ from a large mixing ratio increase at the location of 30 ppb. Since this flux is consistent with previous constraints (both spatially and temporally), there is no evidence that the area of interest north of Svalbard is unique in the context of the wider Arctic. Rather, because the meteorology at the time of the observation was unique in the context of the measurement time series, we obtained over the short course of the episode measurements highly sensitive to emissions over an active seep site, without sensitivity to land-based emissions.

Methane emission estimates for Ireland using a Bayesian Atmospheric Inversion

Arnold, Delia; O'Dowd, Colin; Martin, Damien; Thompson, Rona Louise

Methane emissions from Australia estimated by inverse analysis using in-situ and Satellite (GOSAT) atmospheric observations

Australia has significant sources of atmospheric methane (CH₄), driven by extensive coal and natural gas production, livestock, and large-scale fires. Accurate quantification and characterization of CH₄ emissions are critical for effective climate mitigation strategies in Australia. In this study, we employed an inverse analysis of atmospheric CH₄ observations from the GOSAT satellite and surface measurements from 2016 to 2021 to assess CH₄ emissions in Australia. The inversion process integrates anthropogenic and natural emissions as prior estimates, optimizing them with the NIES-TM-FLEXPART-variational model (NTFVAR) at a resolution of up to 0.1° × 0.1°. We validated the performance of our inverse model using data obtained from the United Nations Environment Program Methane Science (UNEP), Airborne Research Australia 2018 aircraft-based atmospheric CH₄ measurement campaigns. Compared to prior emission estimates, optimized emissions dramatically enhanced the accuracy of modeled concentrations, aligning them much better with observations. Our results indicate that the estimated inland CH4 emissions in Australia amount to 6.84 ± 0.51 Tg CH4 yr−1 and anthropogenic emissions amount to 4.20 ± 0.08 Tg CH4 yr−1, both slightly lower than the values reported in existing inventories. Moreover, our results unveil noteworthy spatiotemporal characteristics, such as upward corrections during the warm season, particularly in Southeastern Australia. During the three most severe months of the 2019–2020 bushfire season, emissions from biomass burning surged by 0.68 Tg, constituting over 71% of the total emission increase. These results highlight the importance of continuous observation and analysis of sectoral emissions, particularly near major sources, to guide targeted emission reduction strategies. The spatiotemporal characteristics identified in this study underscore the need for adaptive and region-specific approaches to CH₄ emission management in Australia.

Methane Emissions from the Arctic OCean to the Atmosphere: Present and future climate effects (MOCA). NILU F

Durant, A.J.; Lund-Myhre, C.; Mienert, J.; Myhre, G.; Stohl, A.; Isaksen, I.S.; Pisso, .I, Greinert, J.; Nisbet, E.G.; Paris, J.; Pyle, J.A.; Belan, B.D.; Ruppel, C.D.; Schlager, H.; Spahni, R.

Methane emissions from the Arctic Ocean.

Myhre, C.L.; Mienert, J.; Myhre, G.; Stohl, A.

Methane emissions in East Asia estimated using atmospheric Bayesian Inversion. NILU F

Thompson, R.L.; Stohl, A.; Zhou, L.X.; Fukuyama, Y.; Tohjima, Y.; Kim, S.-Y.; Lee, H.; Dlugokencky, E. Nisbet, E.; Fisher, R.; Lowry, D.

Methane emissions in the Arctic and sub-Arctic from a Bayesian atmospheric inversion.

Thompson, R, Stohl, A.; Myhre, C.L.; Sasakawa, M.; Machida, T.; Aalto, T.; Dlugokencky, E.; Worthy, D.

Methane fluxes in the high northern latitudes estimated using a Bayesian atmospheric inversion.

Thompson, R. L.; Stohl, A.; Myhre, C. L.; Sasakawa, M.; Machida, T. Aalto, T.; Dlugokencky, E.; Worthy, D.; Skorokhod, A.

Methane from sea to air?

Solbakken, C.F.