Potential environmental impact of bromoform from Asparagopsis farming in Australia

To mitigate the rumen enteric methane (CH4) produced by ruminant livestock, Asparagopsis taxiformis is proposed as an additive to ruminant feed. During the cultivation of Asparagopsis taxiformis in the sea or in terrestrial based systems, this macroalgae, like most seaweeds and phytoplankton, produces a large amount of bromoform (CHBr3), which may contribute to ozone depletion once released into the atmosphere. In this study, the impact of CHBr3 on the stratospheric ozone layer resulting from potential emissions from proposed Asparagopsis cultivation in Australia is assessed by weighting the emissions of CHBr3 with the ozone depletion potential (ODP), which is traditionally defined for long-lived halogens but has been also applied to very short lived substances (VSLSs). An annual yield of ~3.5 × 104 Mg dry weight (DW) is required to meet the needs of 50 % of the beef feedlot and dairy cattle in Australia. Our study shows that the intensity and impact of CHBr3 emissions varies dependent on location and cultivation scenarios. Of the proposed locations, tropical farms near the Darwin region are associated with largest CHBr3 ODP values. However, farming of Asparagopsis using either ocean or terrestrial cultivation systems at any of the proposed locations does not have potential to impact the ozone layer. Even if all Asparagopsis farming was performed in Darwin, the emitted CHBr3 would amount to less than 0.016 % of the global ODP-weighted emissions. The remains are relatively small even if the intended annual yield in Darwin is scaled by a factor 30 to meet the global requirements, which will increase the global ODP-weighted emissions by 0.48 %

Technical note: LIMS observations of lower stratospheric ozone in the southern polar springtime of 1978

The Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) instrument operated from 25 October 1978 through 28 May 1979. This note focuses on its Version 6 (V6) data and indications of ozone loss in the lower stratosphere of the Southern Hemisphere subpolar region during the last week of October 1978. We provide profiles and maps that show V6 ozone values of only 2 to 3 ppmv at 46 hPa within the edge of the polar vortex near 60∘ S from late October through mid-November 1978. There are also low values of V6 nitric acid (∼3 to 6 ppbv) and nitrogen dioxide (< 1 ppbv) at the same locations, indicating that conditions were suitable for a chemical loss of Antarctic ozone some weeks earlier. These “first light” LIMS observations provide the earliest space-based view of conditions within the lower stratospheric ozone layer of the southern polar region in springtime.

The influence of transport model resolution on the inverse modelling of synthetic greenhouse gas emissions in Switzerland

&lt;p&gt;Climate change is one of the biggest challenges of the modern era. Halocarbons contribute already about 14% to current anthropogenic radiative forcing, and their future impact may become significantly larger due to their long atmospheric lifetimes and continued and increasing usage. In addition to their influence on climate change, chlorine and bromine-containing halocarbons are the main drivers of the destruction of the stratospheric ozone layer. Therefore, observing their atmospheric abundance and quantifying their sources is critical for predicting the related future impact on climate change and on the recovery of the stratospheric ozone layer.&lt;/p&gt;&lt;p&gt;Regional scale atmospheric inverse modelling can provide observation-based estimates of greenhouse gas emissions at a country scale and, hence, makes valuable information available to policy makers when reviewing emission mitigation strategies and confirming the countries' pledges for emission reduction. Considering that inverse modelling relies on accurate atmospheric transport modelling any advances to the latter are of key importance. The main objective of this work is to characterize and improve the Lagrangian particle dispersion model (LPDM) FLEXPART-COSMO at kilometer-scale resolution and to provide estimates of Swiss halocarbon emissions by integrating newly available halocarbon observations from the Swiss Plateau at the Berom&amp;#252;nster tall tower. The transport model is offline coupled with the regional numerical weather prediction model (NWP) COSMO. Previous inverse modelling results for Swiss greenhouse gases are based on a model resolution of 7 km x 7 km. Here, we utilize higher resolution (1 km x 1 km) operational COSMO analysis fields to drive FLEXPART and compare these to the previous results.&lt;/p&gt;&lt;p&gt;The higher resolution simulations exhibit increased three-dimensional dispersion, leading to a general underestimation of observed tracer concentration at the receptor location and when compared to the coarse model results. The concentration discrepancies due to dispersion between the two model versions cannot be explained by the parameters utilized in FLEPXART&amp;#8217;s turbulence parameterization, (Obhukov length, surface momentum and heat fluxes, atmospheric boundary layer heights, and horizontal and vertical wind speeds), since a direct comparison of these parameters between the different model versions showed no significant differences. The latter suggests that the dispersion differences may originate from a duplication of turbulent transport, on the one hand, covered by the high resolution grid of the Eulerian model and, on the other hand, diagnosed by FLEXPART's turbulence scheme. In an attempt to reconcile FLEXPART-COSMO&amp;#8217;s turbulence scheme at high resolution, we introduced additional scaling parameters based on analysis of simulated mole fraction deviations depending on stability regime. In addition, we used FLEXPART-COSMO source sensitivities in a Bayesian inversion to obtain optimized emission estimates. Inversions for both the high and low resolution models were carried out in order&amp;#160;to quantify the impact of model resolution on posterior emissions and estimate about the uncertainties of these emissions.&amp;#160;&amp;#160;&lt;/p&gt;

Healing the Ozone Layer

The Montreal Protocol—the regime designed to protect the stratospheric ozone layer—has widely been hailed as the gold standard of global environmental governance and is one of few examples of international institutional cooperative arrangements successfully solving complex transnational problems. Although the stratospheric ozone layer still bears the impacts of ozone depleting substances (ODSs), the problem of ozone depletion is well on its way to being solved due to the protocol. This chapter examines how the protocol was designed and implemented in a way that has allowed it to successfully overcome a number of thorny challenges that most international environmental regimes must face: how to attract sufficient participation, how to promote compliance and manage non-compliance, how to strengthen commitments over time, how to neutralize or co-opt potential ‘veto players’, how to make the costs of implementation affordable, how to leverage public opinion in support of the regime’s goals, and, ultimately, how to promote the behavioural and policy changes needed to solve the problems and achieve the goals the regime was designed to solve. The chapter concludes that while some of the reasons for the Montreal Protocol’s success, such as fairly affordable, available substitutes for ODSs, are not easy to replicate, there are many other elements of this story that can be utilized when thinking about how to design solutions to other transnational environmental problems.

4. Atmospheric composition

Nitrogen, oxygen, and argon represent more than 99.9% of the air we breathe. But Earth’s atmosphere hasn’t always had that composition—it is on at least its third distinctive atmosphere. ‘Atmospheric composition’ provides a brief history of Earth’s atmosphere, before considering the two most important regions of the atmosphere for human survival—the stratosphere and troposphere. The stratospheric ozone layer shields harmful ultraviolet-B light penetrating to the surface, thereby protecting humans and ecosystems from harmful ultraviolet radiation. The troposphere is where billions of people live and breathe. It is also where air pollutants are emitted, wildfires burn, vegetation grows, and where the oceans exchange gases. The impact of atmospheric aerosols and greenhouse gases is also discussed.

Determinants of Effective Problem-Solving

Adopting a problem-solving perspective on governance leads to a focus on the determinants of success or failure in efforts to solve specific problems like the thinning of the stratospheric ozone layer or the onset of climate change. In this regard, it is helpful to begin by distinguishing among outputs, outcomes, and impacts. Outputs are the administrative apparatus and compliance mechanisms created to move governance systems from paper to practice. Outcomes are the behavioral changes brought about by the operation of governance systems. Impacts are the effects of such systems on the alleviation of the problems that motivate their creation. While it is easier to establish causal connections in analyzing the outputs of governance systems, interest in the operation of governance systems arises ultimately from the effectiveness of such systems in solving problems. Qualitative and quantitative research on international regimes has led to the conclusion that these arrangements do make a difference with regard to problem solving. But this is a realm of complex causality in which numerous other factors play a role, and there is significant variation in the effectiveness of governance systems both across regimes and across time with regard to specific regimes.