Order of magnitude wall time improvement of variational methane inversions by physical parallelization: a demonstration using TM5-4DVAR

Atmospheric inversions are used to constrain the emissions of trace gases from atmospheric mole fraction measurements. The variational (4DVAR) inversion approach allows optimization of the emissions at a much higher temporal and spatial resolution than the ensemble or analytical approaches but provides limited opportunities for scalable parallelization as the optimization is performed iteratively. Multidecadal variational inversions are used to optimally extract information from the long measurement records of long-lived atmospheric trace gases like carbon dioxide and methane. However, the wall clock time needed—up to months— complicates these multidecadal inversions. The physical parallelization method introduced by Chevallier (2013) addresses this problem for CO2 inversions by splitting the time period of the chemical transport model into blocks that are run in parallel. Here we present a new implementation of the physical parallelization for variational inversion (PPVI) approach that is suitable for methane inversions as it accounts for methane’s atmospheric lifetime. The performance of PPVI is tested in an 11-year inversion using a TM5-4DVAR inversion setup that assimilates surface observations to optimize methane emissions at grid-scale. We find that the PPVI inversion approach improves the wall clock time performance by a factor of 5 and shows excellent agreement with the posterior emissions of a full serial inversion with identical configuration (global mean emissions difference = 0.06 % with an interannual variation correlation R = 99 %; regional mean emission difference < 5 % and interannual variation R > 0.95). The wall clock time improvement using the PPVI method increases with the size of the inversion period. The PPVI approach is planned to be used in future releases of the CAMS (Copernicus Atmosphere Monitoring Service) multidecadal methane reanalysis.

How necessary and feasible are reductions of methane emissions from livestock to support stringent temperature goals?

Agriculture is the largest single source of global anthropogenic methane (CH 4 ) emissions, with ruminants the dominant contributor. Livestock CH 4 emissions are projected to grow another 30% by 2050 under current policies, yet few countries have set targets or are implementing policies to reduce emissions in absolute terms. The reason for this limited ambition may be linked not only to the underpinning role of livestock for nutrition and livelihoods in many countries but also diverging perspectives on the importance of mitigating these emissions, given the short atmospheric lifetime of CH 4 . Here, we show that in mitigation pathways that limit warming to 1.5°C, which include cost-effective reductions from all emission sources, the contribution of future livestock CH 4 emissions to global warming in 2050 is about one-third of that from future net carbon dioxide emissions. Future livestock CH 4 emissions, therefore, significantly constrain the remaining carbon budget and the ability to meet stringent temperature limits. We review options to address livestock CH 4 emissions through more efficient production, technological advances and demand-side changes, and their interactions with land-based carbon sequestration. We conclude that bringing livestock into mainstream mitigation policies, while recognizing their unique social, cultural and economic roles, would make an important contribution towards reaching the temperature goal of the Paris Agreement and is vital for a limit of 1.5°C. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'.

Recent Development of Two Alternative Gases to SF6 for High Voltage Electrical Power Applications

For many years, SF6 has been the preferred dielectric medium in electrical power applications, particularly in high voltage gas-insulated equipment. However, with the recognition that SF6 has an extremely long atmospheric lifetime and very high global warming potential, governments have pursued emission reductions from gas-filled equipment. The electrical power industry has responded to this environmental challenge applying SF6-free technologies to an expanding range of applications which have traditionally used SF6, including gas-insulated switchgear, gas-insulated circuit breakers and gas-insulated lines or bus bars. Some of these SF6-free solutions include gas mixtures containing fluorinated compounds that have low climate impact, among them, a fluoronitrile and a fluoroketone developed as 3M™ Novec™ 4710 Insulating Gas and 3M™ Novec™ 5110 Insulating Gas, respectively. Both fluoronitrile and fluoroketone mixtures are successfully used in gas-insulated equipment currently operating on the grid where they reduce greenhouse gas emissions by more than 99% versus SF6. This paper reviews these leading components of alternative-gas mixtures with updates on the performance, safety and environmental profiles in electrical power applications.

Reaction of •OH with CHCl=CH-CHF2 and its atmospheric implication for future environmental-friendly refrigerant

In order to understand the atmospheric implication of the chlorinated hydrofluoroolefin (HFO), the geometrical structures and the IR absorption cross sections of the stereoisomers 1-chloro-3,3-difluoropropene were studied using the B3LYP/6-31G(3df) and M06-2X/6-31G(3df) methods in the gas phase. The cis-trans isomerization was assessed using the M06-2X/6-311++G(3df,p)//6-31+G(3df,p) method. The latter method was also employed for thermochemistry and the rate coefficients of the reactions of •OH with the cis- and trans-isomers in the temperature ranging from 200 to 400 K. The computational method CCSD/cc-pVTZ//M06-2X/6-31+G(3df,p) was used to benchmark the rate coefficients. It turns out that, the trans-isomer is more stable than cis-isomer and the trans- to cis-isomerization is thermodynamically unfavorable. The rate coefficient follows the Gaussian law with respect to the inverse of temperature. At the global temperature of stratosphere, the calculated rate coefficients served to estimate the atmospheric lifetime along with the photochemical ozone creation potential (POCP). This yielded lifetimes of 4.31 and 7.31 days and POCPs of 3.80 and 2.23 for the cis- and trans-isomer, respectively. The radiative forcing efficiencies gave 0.0082 and 0.0152 W m−2 ppb−1 for the cis- and trans-isomer, respectively. The global warming potential approached zero for both stereoisomers at 20, 100, and 500 years time horizons.

Combinations of CHCL and СHCL with propane and chladones 125, 227ea as prospective noncombustible refrigerants

В данной работе рассмотрена проблема пожарной опасности применяемых в настоящее время хладагентов, предложено решение - создание негорючих смесевых композиций органических хлоридов с пропаном и хладонами 125, 227еа. Показана возможность увеличения доли короткоживущих компонентов в негорючих смесевых хладагентах, содержащих парниковые газы, с помощью создания тройных смесей. According to existing international agreements production of greenhouse gases must be drastically reduced in all sectors including refrigeration. It is known that refrigerants having short atmospheric lifetime are combustible. One of the methods to solve the problem of combustibility of refrigerants is to create noncombustible mixtures of combustible substance with an inhibitor of combustion. Such mixtures of organic chlorides with propane and CFH or CFH are investigated in this paper both theoretically and experimentally. Experimental equipment was specially adjusted to the combustion properties of the used chlorinated substances. It was obtained that CHCl и CНCl are strong inhibitors of combustion processes including self-inhibition of combustion of these substances themselves. Fluorinated hydrocarbons CFH and CFH are effective in suppression of combustion of dichloromethane and 1, 2-dichloroethane in air. As it follows from the obtained results, it is possible to reduce the content of the greenhouse component in the mixed refrigerant by 93% mass by creating noncombustible mixtures of dichlorides with CFH or CFH which are greenhouse gases. It was also revealed that CFH and CFH are stronger suppressants for combustion of CHCl and CНCl than for combustion of propane. Creation of triple noncombustible mixtures between CH, CHCl and CFH is advisable only when it is necessary to optimize energy efficiency of the refrigerant.

Fire extinguishing efficiency of perfluoro-isohexenes

Показана нехватка современных веществ для газового пожаротушения, вызванная борьбой с глобальным потеплением. Описаны подходы к поиску перспективных газовых огнетушащих веществ (ГОТВ), применявшиеся ранее. Предложен новый подход и найдены с его помощью принципиально новые огнетушащие вещества, полностью удовлетворяющие современным экологическим и токсикологическим требованиям. The paper is devoted to investigation of perfluoro-isohexenes as new gaseous fire suppressants. The current situation in the field of fire protection with chemically active gases is analyzed. The problem of greenhouse gases replacement during fire suppression is discussed. The disadvantage of existing alternative agents is short atmospheric lifetime. It is also shown that the existing approach to development of new gaseous fire extinguishing substances is almost exhausted. New group of gaseous agents for fire suppression - perfluoro-isohexenes - is proposed based on new approach. These substances are non-toxic and have very short atmospheric lifetime. Two types of experimental equipment were used in this work to investigate properties of aforesaid substances as extinguishing agents. It was implemented to determine flammability limits of gaseous mixtures and fire extinguishing concentration of gaseous fire suppressants having high boiling point. It was shown that perfluoro-isohexenes are non-flammable and their extinguishing properties are substantially better than properties of the nearest equivalent - perfuoroethyl-isopropylketone. These results are discussed from the point of view of the features of transformation of considered fire extinguishing substances in a flame.

On the effects of the ocean on atmospheric CFC-11 lifetimes and emissions

The ocean is a reservoir for CFC-11, a major ozone-depleting chemical. Anthropogenic production of CFC-11 dramatically decreased in the 1990s under the Montreal Protocol, which stipulated a global phase out of production by 2010. However, studies raise questions about current overall emission levels and indicate unexpected increases of CFC-11 emissions of about 10 Gg ⋅ yr−1 after 2013 (based upon measured atmospheric concentrations and an assumed atmospheric lifetime). These findings heighten the need to understand processes that could affect the CFC-11 lifetime, including ocean fluxes. We evaluate how ocean uptake and release through 2300 affects CFC-11 lifetimes, emission estimates, and the long-term return of CFC-11 from the ocean reservoir. We show that ocean uptake yields a shorter total lifetime and larger inferred emission of atmospheric CFC-11 from 1930 to 2075 compared to estimates using only atmospheric processes. Ocean flux changes over time result in small but not completely negligible effects on the calculated unexpected emissions change (decreasing it by 0.4 ± 0.3 Gg ⋅ yr−1). Moreover, it is expected that the ocean will eventually become a source of CFC-11, increasing its total lifetime thereafter. Ocean outgassing should produce detectable increases in global atmospheric CFC-11 abundances by the mid-2100s, with emission of around 0.5 Gg ⋅ yr−1; this should not be confused with illicit production at that time. An illustrative model projection suggests that climate change is expected to make the ocean a weaker reservoir for CFC-11, advancing the detectable change in the global atmospheric mixing ratio by about 5 yr.

Investigating fire NOx emissions with TROPOMI

&lt;p&gt;Most of the anthropogenic emissions of nitrogen oxides (NOx = NO&lt;sub&gt;2&lt;/sub&gt; + NO) are linked to burning of fossil fuels for energy production, transportation or industrial processes. However, biomass burning and in particular large wild fires in tropical and sub-tropical regions can also be large sources of nitrogen oxides at least locally. Depending on the size of the fires, particles and gases can be lifted into the free troposphere and even higher, increasing the atmospheric lifetime of NOx and enabling long range transport.&lt;/p&gt;&lt;p&gt;The TROPOMI instrument on board of Sentinel 5 precursor (S5p) is a nadir viewing UV/vis imaging spectrometer launched in October 2017 and operationally providing data since July 2018. One of the main products that can be retrieved from TROPOMI spectra is tropospheric and total column NO&lt;sub&gt;2&lt;/sub&gt;. Compared to previous UV/vis satellite instruments such as GOME, SCIAMACHY, GOME2 and OMI, TROPOMI has a higher spatial resolution of 3.5 x 5.5 km&lt;sup&gt;2&lt;/sup&gt;. This reduced foot print size enables detection and evaluation of more localised sources such as individual fires and their plumes, and better separation of different contributions to the overall NO&lt;sub&gt;2&lt;/sub&gt; loading.&lt;/p&gt;&lt;p&gt;In this presentation, IUP-Bremen TROPOMI NO&lt;sub&gt;2&lt;/sub&gt; retrievals are evaluated for biomass burning signatures during the years 2018 to 2020, three years with very different burning seasons. The amounts and spatial distributions of NO&lt;sub&gt;2&lt;/sub&gt; from fires are compared between the years and between different fire regions, and their impact on regions downwind of the sources is investigated.&lt;/p&gt;

Atmosphere-based US emission estimates of SF6 for 2007 - 2018

&lt;p&gt;Sulfur hexafluoride (SF&lt;sub&gt;6&lt;/sub&gt;) is a potent greenhouse gas (GHG) that is primarily emitted from electrical circuit breakers and heavy-duty gas-insulated switchgears in electric transmission and distribution equipment, magnesium production and processing, and electronics production. It has a 100-year global warming potential of 23500 and an atmospheric lifetime of 850 (580 - 1400) years. Because of its extremely large global warming potential and long atmospheric lifetime, its emissions, while currently small, have an outsized influence on changing climate over the long term.&amp;#160; However, current US emissions of SF&lt;sub&gt;6&lt;/sub&gt; are uncertain. The US SF&lt;sub&gt;6&lt;/sub&gt; consumption that was used to estimate SF&lt;sub&gt;6&lt;/sub&gt; emissions in the US EPA national GHG reporting to the UNFCCC has an uncertainty of 30 &amp;#8211; 60%, depending on whether to use the US SF&lt;sub&gt;6&lt;/sub&gt; supplier reports or user reports. With different inventory methodologies, the national emissions estimates of SF&lt;sub&gt;6&lt;/sub&gt; from the EDGAR and US EPA&amp;#8217;s GHG inventories differ by more than a factor of 4. Here, we will present the first detailed U.S. national and regional emissions of SF&lt;sub&gt;6&lt;/sub&gt; that were derived from an inverse analysis of an extensive flask-air sampling network from the US NOAA&amp;#8217;s Global Greenhouse Gas Reference Network and high-resolution atmospheric transport simulations for 2007 - 2018. We will discuss our atmosphere-based top-down emission estimates in comparison with the existing bottom-up emission inventories, our derived seasonal variation of SF&lt;sub&gt;6&lt;/sub&gt; emissions, and associated implications regarding each industry&amp;#8217;s contribution to emissions and optimal emissions mitigation strategies. Because atmospheric SF&lt;sub&gt;6&lt;/sub&gt; measurements are also used to assess atmospheric transport errors assuming no biases in SF&lt;sub&gt;6&lt;/sub&gt; emissions reported by the EDGAR inventory, our analysis also has important implications on limitations in such applications.&lt;/p&gt;