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Forestation is a major component of future long‐term emissions reduction and CO2removal strategies, but the viability of carbon stored in vegetation under future climates is highly uncertain. We analyze the results from seven CMIP6 models for a combined scenario with high fossil fuel emissions (from SSP5‐8.5) and forest expansion (from SSP1‐2.6) which has ∼4.8% increase in global total forest cover relative to 2015. This scenario aims to demonstrate the ability of forestation strategies to mitigate climate change under continued increasing CO2emissions and includes the potential impacts of increased CO2concentration and a warming climate on vegetation growth. The model intercomparison shows that forestation as a CO2removal strategy has limited impact on global climate under a high global warming scenario, despite generating a substantial cumulative carbon sink of 10–60 Pg C over the period 2015–2100. Using a single model ensemble, we show that there are local increases in warm extremes in response to forestation associated with decreases in the number of cool days. Furthermore, we find evidence of a shift in the global carbon balance, whereby increased carbon storage on land of ∼25 Pg C by 2100 associated with forestation has a concomitant decrease in the carbon uptake by the ocean due to reduced atmospheric CO2concentrations. We use seven model projections to estimate future climates in which forestation occurs under a high fossil fuel emission scenario. While the forestation in this scenario is not enough to substantially mitigate global warming, the new forest cover makes up a stable carbon sink over the next century. Forestation under a high emissions scenario is projected to generate a limited but stable carbon sinkThis sink on its own is not enough to significantly mitigate global warmingForestation has substantial impacts on the global carbon balance and regional impacts on temperature extremes Forestation under a high emissions scenario is projected to generate a limited but stable carbon sink This sink on its own is not enough to significantly mitigate global warming Forestation has substantial impacts on the global carbon balance and regional impacts on temperature extremes

The vast majority of the landslides in Hong Kong are triggered by rainfall. Surface drainage commonly provided on man-made slopes aims to prevent surface erosion and reduce infiltration. It plays an important role to avert slope instability. However, inadequate management of surface drainage could hamper its efficiency and often results in uncontrolled surface water flow contributory to landsliding. This paper provides insights on the importance of slope surface drainage management under the dense urban settings in Hong Kong from the landslide perspective. Selected landslides involving inadequately managed surface drainage are presented to highlight the key lessons learnt and areas deserving attention on various drainage aspects, including the design and detailing. It is noteworthy that inadequate surface drainage maintenance could exacerbate and lead to sizeable landslides even on engineered slopes. A review of landslide records over the years suggests that some landslides could have been averted had there been proper surface drainage maintenance.

ABSTRACTAn intense rainstorm on 21 May 2016 resulted a total of 34 natural terrain landslides in the vicinity of Sai Kung Sai Wan Road in the Sai Kung East Country Park, Hong Kong. One of these landslides was a large-scale failure with a source volume of about 2100 m3. It was almost an order of magnitude larger than all the others. The debris severely eroded a road embankment, undermining the road and resulting in road closure. The nature of the landslide was unusual in that it was a structurally controlled rockslide, with a basal failure surface formed from a persistent, planar sheeting joint within columnar jointed tuff rock with a maximum depth of about 12 m, while the other landslides that occurred in the country park during the same rainstorm involved only shallow failures within the regolith. An investigation of this unusual landslide was undertaken to diagnose the probable mechanism and causes of the failure. As there was concern about further large-scale instability occurring in the adjacent hillside where the sheeting joint was inferred to extend into, the potential for further large-scale instability was assessed as part of the investigation. The key components of the investigation included detailed engineering geological mapping, ground investigation and engineering analyses. This paper presents the findings of the investigation.

International efforts to limit global warming and ocean acidification aim to slow the growth of atmospheric CO2, guided primarily by national and industry estimates of production and consumption of fossil fuels. Atmospheric verification of emissions is vital but present global inversion methods are inadequate for this purpose. We demonstrate a clear response in atmospheric CO2coinciding with a sharp 2010 increase in Asian emissions but show persisting slowing mean CO2growth from 2002/03. Growth and inter-hemispheric concentration difference during the onset and recovery of the Global Financial Crisis support a previous speculation that the reported 2000–2008 emissions surge is an artefact, most simply explained by a cumulative underestimation (∼ 9 Pg C) of 1994–2007 emissions; in this case, post-2000 emissions would track mid-range of Intergovernmental Panel on Climate Change emission scenarios. An alternative explanation requires changes in the northern terrestrial land sink that offset anthropogenic emission changes. We suggest atmospheric methods to help resolve this ambiguity.

The first cellulose acetate fiber, commonly referred to as acetate, was produced in Europe in 1918 and on a large scale in the United States of America in 1924 making acetate the second man‐made fiber to be produced.1The usage of acetate worldwide peaked at a consumption of approximately 400 kilotons in the early 1970's.2In the past three decades the use of acetate fiber has declined as fabric manufacturers moved to lower costs manmade fibers such as polyester. Manufacturers of acetate have worked aggressively to reduce their cost while maintaining product quality. These efforts have had some reward, leading to acetate's categorization as a niche fiber. As such, cellulose acetate represents less than one percent of the world's total fiber consumption as compared to cotton at over a third3of the world's consumption and polyester at around a fourth.4

Carbon dioxide sources for 1981–1995 are calculated using a mass-balance inversion method. Options for deriving a suitable surface constraint for the model from the available observed data are assessed. A new method, in which the longitudinal variation in the observations is accounted for, is compared to a more conventional spline fit to the data. This new constraint is applied either to the zonal mean concentration or to the concentration at all grid points. The results indicate relatively large differences between long-term mean regional sources but relatively good agreement of the interannual variations. The global and tropical sources estimated show a surprising relationship to the southern oscillation index; maximum correlation occurs for CO2sources leading the SOI by around 9 months.

Sulfur hexafluoride (SF6) is an excellent tracer of large-scale atmospheric transport, because it has slowly increasing sources mostly confined to northern midlatitudes, and has a lifetime of thousands of years. We have simulated the emissions, transport, and concentration of SF6for a 5-year period, and compared the results with atmospheric observations. In addition, we have performed an intercomparison of interhemispheric transport among 11 models to investigate the reasons for the differences among the simulations. Most of the models are reasonably successful at simulating the observed meridional gradient of SF6in the remote marine boundary layer, though there is less agreement at continental sites. Models that compare well to observations in the remote marine boundary layer tend to systematically overestimate SF6at continental locations in source regions, suggesting that vertical trapping rather than meridional transport may be a dominant control on the simulated meridional gradient. The vertical structure of simulated SF6in the models supports this interpretation. Some of the models perform quite well in terms of the simulated seasonal cycle at remote locations, while others do not. Interhemispheric exchange time varies by a factor of 2 when estimated from 1-dimensional meridional profiles at the surface, as has been done for observations. The agreement among models is better when the global surface mean mole fraction is used, and better still when the full 3-dimensional mean mixing ratio is used. The ranking of the interhemispheric exchange time among the models is not sensitive to the change from station values to surface means, but is very sensitive to the change from surface means to the full 3-dimensional tracer fields. This strengthens the argument that vertical redistribution dominates over interhemispheric transport in determining the meridional gradient at the surface. Vertically integrated meridional transport in the models is divided roughly equally into transport by the mean motion, the standing eddies, and the transient eddies. The vertically integrated mass flux is a good index of the degree to which resolved advection vs. parameterized diffusion accomplishes the meridional transport of SF6. Observational programs could provide a much better constraint on simulated chemical tracer transport if they included regular sampling of vertical profiles of nonreactive trace gases over source regions and meridional profiles in the middle to upper troposphere. Further analysis of the SF6simulations will focus on the subgrid-scale parameterized transports.

Sulfur hexafluoride (SF6) is an excellent tracer of large‐scale atmospheric transport, because it has slowly increasing sources mostly confined to northern midlatitudes, and has a lifetime of thousands of years. We have simulated the emissions, transport, and concentration of SF6for a 5‐year period, and compared the results with atmospheric observations. In addition, we have performed an intercomparison of interhemispheric transport among 11 models to investigate the reasons for the differences among the simulations. Most of the models are reasonably successful at simulating the observed meridional gradient of SF6in the remote marine boundary layer, though there is less agreement at continental sites. Models that compare well to observations in the remote marine boundary layer tend to systematically overestimate SF6at continental locations in source regions, suggesting that vertical trapping rather than meridional transport may be a dominant control on the simulated meridional gradient. The vertical structure of simulated SF6in the models supports this interpretation. Some of the models perform quite well in terms of the simulated seasonal cycle at remote locations, while others do not. Interhemispheric exchange time varies by a factor of 2 when estimated from 1‐dimensional meridional profiles at the surface, as has been done for observations. The agreement among models is better when the global surface mean mole fraction is used, and better still when the full 3‐dimensional mean mixing ratio is used. The ranking of the interhemispheric exchange time among the models is not sensitive to the change from station values to surface means, but is very sensitive to the change from surface means to the full 3‐dimensional tracer fields. This strengthens the argument that vertical redistribution dominates over interhemispheric transport in determining the meridional gradient at the surface. Vertically integrated meridional transport in the models is divided roughly equally into transport by the mean motion, the standing eddies, and the transient eddies. The vertically integrated mass flux is a good index of the degree to which resolved advection vs. parameterized diffusion accomplishes the meridional transport of SF6. Observational programs could provide a much better constraint on simulated chemical tracer transport if they included regular sampling of vertical profiles of nonreactive trace gases over source regions and meridional profiles in the middle to upper troposphere. Further analysis of the SF6simulations will focus on the subgrid‐scale parameterized transports.

Carbon dioxide sources for 1981–1995 are calculated using a mass‐balance inversion method. Options for deriving a suitable surface constraint for the model from the available observed data are assessed. A new method, in which the longitudinal variation in the observations is accounted for, is compared to a more conventional spline fit to the data. This new constraint is applied either to the zonal mean concentration or to the concentration at all grid points. The results indicate relatively large differences between long‐term mean regional sources but relatively good agreement of the interannual variations. The global and tropical sources estimated show a surprising relationship to the southern oscillation index; maximum correlation occurs for CO2sources leading the SOI by around 9 months.