The article presents a study that investigates on the importance of identifying and quantifying planetary boundaries to prevent human activities in affecting environmental condition. The author states the industrial revolution and advancement in human civilization has caused the unstability of the environmental state that is less conducive for humans to live and affect their health condition. The author notes that planetary boundaries served a control variables to secure the safety of its citizen as well as protect the environment from shifting to dangerous levels. It also cites the different planetary boundaries, along with its impact on climate change and Earth system degradation

ABSTRACT. Anthropogenic pressures on the Earth System have reached a scale where abrupt global environmental change can no longer be excluded. We propose a new approach to global sustainability in which we define planetary boundaries within which we expect that humanity can operate safely.Transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental-to planetary-scale systems. We have identified nine planetary boundaries and, drawing upon current scientific understanding, we propose quantifications for seven of them. These seven are climate change (CO 2 concentration in the atmosphere <350 ppm and/or a maximum change of +1 W m -2 in radiative forcing); ocean acidification (mean surface seawater saturation state with respect to aragonite ≥ 80% of pre-industrial levels); stratospheric ozone (<5% reduction in O 3 concentration from pre-industrial level of 290 Dobson Units); biogeochemical nitrogen (N) cycle (limit industrial and agricultural fixation of N 2 to 35 Tg N yr -1 ) and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background weathering of P); global freshwater use (<4000 km 3 yr -1 of consumptive use of runoff resources); land system change (<15% of the ice-free land surface under cropland); and the rate at which biological diversity is lost (annual rate of <10 extinctions per million species). The two additional planetary boundaries for which we have not yet been able to determine a boundary level are chemical pollution and atmospheric aerosol loading. We estimate that humanity has already transgressed three planetary boundaries: for climate change, rate of biodiversity loss, and changes to the global nitrogen cycle. Planetary boundaries are interdependent, because transgressing one may both shift the position of other boundaries or cause them to be transgressed. The social impacts of transgressing boundaries will be a function of the social-ecological resilience of the affected societies. Our proposed boundaries are rough, first estimates only, surrounded by large uncertainties and knowledge gaps. Filling these gaps will require major advancements in Earth System and resilience science. The proposed concept of "planetary boundaries" lays the groundwork for shifting our approach to governance and management, away from the essentially sectoral analyses of limits to growth aimed at minimizing negative externalities, toward the estimation of the safe space for human development. Planetary boundaries define, as it were, the boundaries of the "planetary playing field" for humanity if we want to be sure of avoiding major human-induced environmental change on a global scale.

Abstract. Atmospheric aerosol particles are known to contain organic carbon material in variable amounts, depending on their location. In some parts of the world, organic compounds make up the majority of the total suspended particle mass. This class of particulate matter is important in a wide range of geophysical and environmental problems, ranging from local issues (e.g., pollution toxicity) to the global scale (e.g., climate change). Unfortunately, the richness of organic chemistry and the highly variable physical properties associated with both natural and anthropogenic organic particles lead to great difficulties in sampling and obtaining complete chemical information on these materials. These obstacles result in an incomplete picture of a potentially significant part of atmospheric chemistry and a correspondingly poor understanding of the geophysical and environmental effects of this aerosol. Given the paucity of quantitative molecular data, the purpose of this paper is not to quantitatively describe the importance of organic aerosols in environmental issues, but rather to present a basis for defining what data are needed. With this goal in mind, we begin with an overview of the major environmental issues known to be affected by organic aerosols, followed by a description of the distribution, sources, and chemical and physical properties of organic aerosols as they are currently understood. Methods used to collect and study organic aerosols are provided, followed by a list of outstanding scientific questions and suggestions for future research priorities. mental Protection Agency (U.S. EPA), 1996]. This fraction has been studied extensively, and several models of the geographical distribution and climatic effects of this group of compounds in the aerosol have appeared [IPCC, 1995]. While somewhat less studied, the insoluble inorganic fraction has been analyzed, for example, with nuclear methods, and generally consists of metal oxides, silicates, and clay minerals derived from soil dust. Unlike the salt and soil dust fractions, the organic compounds cover a very wide range of molecular forms, solubilities, reactivities, and physical properties, which makes a complete characterization extremely difficult. The so-called "elemental" carbon (EC) aerosol has been studied extensively, but it is still not clear to what degree it is indeed elemental [graphitic, C(0)] material or high molecular weight refractory organic species or a combination of both. Consequently, there is still no complete inventory of the chemical compounds that compose the fine-particle organic aerosol from any site in the world, and there is only a limited understanding of the sources, sinks, transport, and transformation processes of these particles and their effects. Since organic compounds are usually the second most abundant component of fine aerosol after sulfates [Heintzenberg, 1989; White, 1990; U.S. EPA, 1996], our understanding of the numerous

Primary marine aerosol (PMA)-cloud interactions off the coast of California were investigated using observations of marine aerosol, cloud condensation nuclei (CCN), and stratocumulus clouds during the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) studies. Based on recently reported measurements of PMA size distributions, a constrained lognormal-mode-fitting procedure was devised to isolate PMA number size distributions from total aerosol size distributions and applied to E-PEACE measurements. During the 12 day E-PEACE cruise on the R/V Point Sur, PMA typically contributed less than 15% of total particle concentrations. PMA number concentrations averaged 12 cm À3 during a relatively calmer period (average wind speed 12 m/s 1 ) lasting 8 days, and 71 cm À3 during a period of higher wind speeds (average 16 m/s 1 ) lasting 5 days. On average, PMA contributed less than 10% of total CCN at supersaturations up to 0.9% during the calmer period; however, during the higher wind speed period, PMA comprised 5-63% of CCN (average 16-28%) at supersaturations less than 0.3%. Sea salt was measured directly in the dried residuals of cloud droplets during the SOLEDAD study. The mass fractions of sea salt in the residuals averaged 12 to 24% during three cloud events. Comparing the marine stratocumulus clouds sampled in the two campaigns, measured peak supersaturations were 0.2 ± 0.04% during E-PEACE and 0.05-0.1% during SOLEDAD. The available measurements show that cloud droplet number concentrations increased with >100 nm particles in E-PEACE but decreased in the three SOLEDAD cloud events.

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We report on results from a World Climate Research Program workshop on representations of scavenging and deposition processes in global transport models of the atmosphere. 15 models were evaluated by comparing simulations of radon, lead, sulfur dioxide, and sulfate against each other, and against observations of these constituents. This paper provides a survey on the simulation differences between models. It identifies circumstances where models are consistent with observations or with each other, and where they differ from observations or with each other. The comparison shows that most models are able to simulate seasonal species concentrations near the surface over continental sites to within a factor of 2 over many regions of the globe. Models tend to agree more closely over source (continental) regions than for remote (polar and oceanic) regions. Model simulations differ most strongly in the upper troposphere for species undergoing wet scavenging processes. There are not a sufficient number of observations to characterize the climatology (long-term average) of species undergoing wet scavenging in the upper troposphere. This highlights the need for either a different strategy for model evaluation (e.g., comparisons on an event by event basis) or many more observations of a few carefully chosen constituents.

An instrument is described that samples cloud droplets by removing them from the surrounding air and small unactivated particles through inertial impaction. The sampled droplets are then evaporated, leaving behind the material dissolved or suspended in the droplets as residue particles or gases. The instrument is capable of sampling droplets as a function of their size; it has an adjustable cut size in the range between about 9 and 30 pm in diameter, rejects droplets and particles smaller than the

In June 1994 the Monterey Area Ship Track (MAST) experiment was conducted off the coast of California to investigate the processes behind anthropogenic modification of cloud albedo. The motivation for the MAST experiment is described here, as well as details of the experimental design. Measurement platforms and strategies are explained, and a summary of experiment operations is presented. The experiment produced the largest dataset to date of direct measurements of the effects of ships on the microphysics and radiative properties of marine stratocumulus clouds as an analog for the indirect effects of anthropogenic pollution on cloud albedo.