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HCFC‐22 is an ozone‐depleting substance with a greenhouse effect. The atmospheric mole fractions of HCFC‐22 have been increasing since the 1950s. Within the NDACC‐IRWG network, HCFC‐22 mol fractions can be retrieved from solar absorption spectra measured by ground‐based FTIR. However, only a few sites have provided HCFC‐22 data sets. Here, we demonstrate a harmonized FTIR HCFC‐22 retrieval strategy and generate a new global NDACC‐IRWG HCFC‐22 data set at 16 FTIR sites. The systematic and random uncertainties are 5.3%–8.7% and 3.2%–8.0%, respectively. A maximum HCFC‐22 column annual growth rate was observed in 2009 with a mean of 7.65 ± 1.39 ppt/year, and the HCFC‐22 annual growth rate decreased to 3.57 ± 1.39 ppt/year (2016–2020) and 2.15 ± 2.09 ppt/year (2021–2023). The annual growth rates derived from the FTIR measurements are compared to the ones derived from NOAA surface flask samplings and ACE‐FTS satellite measurements, and the three independent data sets show a good agreement. Plain Language Summary: Monitoring the atmospheric HCFC‐22 mol fraction and its long‐term trend is important to the stratospheric ozone layer and climate change. Ground‐based FTIR measurements within the NDACC‐IWRG community provide a powerful technique for observing atmospheric trace gases. However, due to different retrieval software and procedures among the sites, the record was too heterogeneous for monitoring the global evolution of HCFC‐22 over time. In this study, we propose a harmonized FTIR HCFC‐22 retrieval strategy and generate a global NDACC‐IRWG HCFC‐22 data set at 16 FTIR sites. The retrieval uncertainty of the FTIR HCFC‐22 is well presented and discussed. Based on the new FTIR HCFC‐22 measurements, the HCFC‐22 annual growth rates between 1990 and 2023 are evaluated. The results are compared with two independent data sets: NOAA flask samplings and ACE‐FTS satellite measurements. Good agreement among the three data sets is found, with a clear decrease in the growth rate of atmospheric HCFC‐22 in recent years. According to the latest Montreal Protocol, HCFC‐22 should be phased out within the next 5–6 years. The global FTIR observations will assure continuity into the next years and decades when HCFC‐22 mol fractions should start decreasing after the official phase‐out. Key Points: Implemented a harmonized NDACC‐IRWG FTIR HCFC‐22 retrieval strategy and provided a new global long‐term HCFC‐22 data setA decrease in the growth rate of the atmospheric HCFC‐22 column has been observed by FTIR measurements since 2009The FTIR, NOAA flask samplings, and ACE‐FTS satellite observations show a good agreement in the HCFC‐22 trend [ABSTRACT FROM AUTHOR]

This Editorial introduces the Virtual Issue 'Marine macrophytes in a changing world: mechanisms underpinning responses and resilience to environmental stress' that includes the following papers: Campbell et al. (2018), Collier et al. (2018), Ferreira et al. (2014), Jung et al. (2023), Konotchick et al. (2013), Litsi‐Mizan et al. (2023), McIntire & Fajardo (2014), Murúa et al. (2020), Pedersen et al. (2016), Saha et al. (2024), Schmidt & Saha (2021), Smale (2020), Viana et al. (2019). Access the Virtual Issue at www.newphytologist.com/virtualissues. [ABSTRACT FROM AUTHOR]

This study presents an updated and homogenised ozone time series covering 34 years (1987–2020) of ozonesonde measurements at Lauder, New Zealand, and attributes vertically resolved ozone trends using a multiple linear regression (MLR) analysis and a chemistry–climate model (CCM). Homogenisation of the time series leads to a marked difference in ozone values before 1997, in which the ozone trends are predominantly negative from the surface to ∼ 30 km, ranging from ∼ - 2 % per decade to - 13 % per decade, maximising at around 12–13 km, in contrast to the uncorrected time series which shows no clear trends for this period. For the post-2000 period, ozone at Lauder shows negative trends in the stratosphere, maximising just below 20 km (∼ - 5 % per decade) despite the fact that stratospheric chlorine and bromine from ozone-depleting substances (ODSs) have both been declining since 1997. However, the ozone trends change from negative for 1987–1999 to positive in the post-2000 period in the free troposphere. The post-2000 ozone trends calculated from the ozonesonde measurements compare well with those derived from the co-located low-vertical-resolution Fourier-transform infrared spectroscopy (FTIR) ozone time series. The MLR analysis identifies that the increasing tropopause height, associated with CO2 -driven dynamical changes, is the leading factor driving the continuous negative trend in lower-stratospheric ozone at Lauder over the whole observational period, whilst the ozone-depleting substances (ODSs) only contribute to the negative ozone trend in the lower stratosphere over the pre-1999 period. Meanwhile, stratospheric temperature changes contribute significantly to the negative ozone trend above 20 km over the post-2000 period. Furthermore, the chemistry–climate model (CCM) simulations that separate the effects of individual forcings show that the predominantly negative modelled trend in ozone for the 1987–1999 period is driven not only by ODSs but also by increases in greenhouse gases (GHGs), with large but opposing impacts from methane (positive) and CO2 (negative), respectively. Over the 2000–2020 period, the model results show that the CO2 increase is the dominant driver for the negative trend in the lower stratosphere, in agreement with the MLR analysis. Although the model underestimates the observed negative ozone trend in the lower stratosphere for both periods, it clearly shows that CO2 -driven dynamical changes have played an increasingly important role in driving the lower-stratospheric ozone trends in the vicinity of Lauder. [ABSTRACT FROM AUTHOR]

Background and Aims Large brown macroalgae serve as foundation organisms along temperate and polar coastlines, providing a range of ecosystem services. Saccorhiza polyschides is a warm-temperate kelp-like species found in the northeast Atlantic, which is suggested to have proliferated in recent decades across the southern UK, possibly in response to increasing temperatures, physical disturbance and reduced competition. However, little is known about S. polyschides with regard to ecological functioning and population dynamics across its geographical range. Here we examined the population demography of S. polyschides populations in southwest UK, located within the species' range centre, to address a regional knowledge gap and to provide a baseline against which to detect future changes. Methods Intertidal surveys were conducted during spring low tides at three sites along a gradient of wave exposure in Plymouth Sound (Western English Channel) over a period of 15 months. Density, cover, age, biomass and morphology of S. polyschides were quantified. Additionally, less frequent sampling of shallow subtidal reefs was conducted to compare intertidal and subtidal populations. Key Results We recorded pronounced seasonality, with fairly consistent demographic patterns across sites and depths. By late summer, S. polyschides was a dominant habitat-former on both intertidal and subtidal reefs, with maximum standing stock exceeding 13 000 g wet weight m−2. Conclusions Saccorhiza polyschides is a conspicuous and abundant member of rocky reef assemblages in the region, providing complex and abundant biogenic habitat for associated organisms and high rates of primary productivity. However, its short-lived pseudo-annual life strategy is in stark contrast to dominant long-lived perennial laminarian kelps. As such, any replacement or reconfiguration of habitat-forming macroalgae due to ocean warming will probably have implications for local biodiversity and community composition. More broadly, our study demonstrates the importance of high-resolution cross-habitat surveys to generate robust baselines of kelp population demography, against which the ecological impacts of climate change and other stressors can be reliably detected. [ABSTRACT FROM AUTHOR]

Background and Aims Marine heatwaves (MHWs) are widely recognized as pervasive drivers of ecosystem change, yet our understanding of how different MHW properties mediate ecological responses remains largely unexplored. Understanding MHW impacts on foundation species is particularly important, given their structural role in communities and ecosystems. Methods We simulated a series of realistic MHWs with different levels of intensity (Control: 14 °C, Moderate: 18 °C, Extreme: 22 °C) and duration (14 or 28 d) and examined responses of two habitat-forming kelp species in the southwest UK. Here, Laminaria digitata reaches its trailing edge and is undergoing a range contraction, whereas Laminaria ochroleuca reaches its leading edge and is undergoing a range expansion. Key Results For both species, sub-lethal stress responses induced by moderate-intensity MHWs were exacerbated by longer duration. Extreme-intensity MHWs caused dramatic declines in growth and photosynthetic performance, and elevated bleaching, which were again exacerbated by longer MHW duration. Stress responses were most pronounced in L. ochroleuca , where almost complete tissue necrosis was observed by the end of the long-duration MHW. This was unexpected given the greater thermal safety margins assumed with leading edge populations. It is likely that prolonged exposure to sub-lethal thermal stress exceeded a physiological tipping point for L. ochroleuca , presumably due to depletion of internal reserves. Conclusions Overall, our study showed that exposure to MHW profiles projected to occur in the region in the coming decades can have significant deleterious effects on foundation kelp species, regardless of their thermal affinities and location within respective latitudinal ranges, which would probably have consequences for entire communities and ecosystems. [ABSTRACT FROM AUTHOR]