Anthropogenic Greenhouse Gas Emissions Research Articles

Impact of Climate Change on the Environment: A Synthesis Study

Climate change has a significant impact on both physical and social components of the environment. Every component of the environment has been suffering the impacts of climate change. All components of the environment are interrelated through the exchanging of energy and matter; hence they actively interact. Major components of the environment like the biosphere, lithosphere, atmosphere, and hydrosphere are open systems to impact climate change. This paper describes the major impacts of climate change on major components of the environment. This study investigated the current state, wide-range global research trends, and different concerns on the impacts of climate change on the sustainable tourism. Global climate change represents a grand challenge for society, one that is increasingly influencing tourism sector investment, planning, operations, and demand. This study synthesized a total of 36 studies on climate change by sourcing published material from the review that was performed in indexed databases namely Dimensions, Web Science, Elsevier Scopus, and Google Scholar. Therefore, the study found that human beings are the major contributors to climate change through anthropogenic greenhouse gas emissions that worsened during the Green Revolution. Climate change outcomes through the loss of valuable ecosystem goods and services, degrading the most of keystone species sites. In other ways, loss of biodiversity, changes in atmospheric composition, changes in chemical reactions in soil, changes in water quality, availability, and hydrologic cycles, and frequent occurrence of extreme weather conditions. Of course! The effects of climate change are wide-ranging and diverse, impacting many areas and facets of daily life. Therefore, this study recommends implementing carbon pricing mechanisms to internalize the costs of greenhouse gas emissions and enforcing stringent environmental regulations and standards to limit emissions and pollution. Support global efforts and agreements to combat climate change, such as the Paris Agreement.

Technological Maturity of Aircraft-Based Methane Sensing for Greenhouse Gas Mitigation.

Methane is a major contributor to anthropogenic greenhouse gas emissions. Identifying large sources of methane, particularly from the oil and gas sectors, will be essential for mitigating climate change. Aircraft-based methane sensing platforms can rapidly detect and quantify methane point-source emissions across large geographic regions, and play an increasingly important role in industrial methane management and greenhouse gas inventory. We independently evaluate the performance of five major methane-sensing aircraft platforms: Carbon Mapper, GHGSat-AV, Insight M, MethaneAIR, and Scientific Aviation. Over a 6 week period, we released metered gas for over 700 single-blind measurements across all five platforms to evaluate their ability to detect and quantify emissions that range from 1 to over 1,500 kg(CH4)/h. Aircraft consistently quantified releases above 10 kg(CH4)/h, and GHGSat-AV and Insight M detected emissions below 5 kg(CH4)/h. Fully blinded quantification estimates for platforms using downward-facing imaging spectrometers have parity slopes ranging from 0.76 to 1.13, with R2 values of 0.61 to 0.93; the platform using continuous air sampling has a parity slope of 0.5 (R2 = 0.93). Results demonstrate that aircraft-based methane sensing has matured since previous studies and is ready for an increasingly important role in environmental policy and regulation.

Opinion: A research roadmap for exploring atmospheric methane removal via iron salt aerosol

Abstract. The escalating climate crisis requires rapid action to reduce the concentrations of atmospheric greenhouse gases and lower global surface temperatures. Methane will play a critical role in near-term warming due to its high radiative forcing and short atmospheric lifetime. Methane emissions have accelerated in recent years, and there is significant risk and uncertainty associated with the future growth in natural emissions. The largest natural sink of methane occurs through oxidation reactions with atmospheric hydroxyl and chlorine radicals. Enhanced atmospheric oxidation could be a potential approach to remove atmospheric methane. One method proposes the addition of iron salt aerosol (ISA) to the atmosphere, mimicking a natural process proposed to occur when mineral dust mixes with chloride from sea spray to form iron chlorides, which are photolyzed by sunlight to produce chlorine radicals. Under the right conditions, lofting ISA into the atmosphere could potentially reduce atmospheric methane concentrations and lower global surface temperatures. Recognizing that potential atmospheric methane removal must only be considered an additive measure – in addition to, not replacing, crucial anthropogenic greenhouse gas emission reductions and carbon dioxide removal – roadmaps can be a valuable tool to organize and streamline interdisciplinary and multifaceted research to efficiently move towards understanding whether an approach may be viable and socially acceptable or if it is nonviable and further research should be deprioritized. Here we present a 5-year research roadmap to explore whether ISA enhancement of the chlorine radical sink could be a viable and socially acceptable atmospheric methane removal approach.

Entomophagy: A sustainable food alternative to save planet

Climate change not only fringes rising average temperatures but shifting wildlife populations, rising seas, extreme weather events and other impacts. These changes are due to addition of greenhouse gases to the atmosphere due to impact of human activities. One of the important human activities which are a major contributor of greenhouse gas is Animal Agriculture. Meat consumption is responsible for releasing greenhouse gases such as methane, CO, and nitrous oxide. Livestock production accounts for 14.5% of all anthropogenic greenhouse gas emissions, with beef having the highest footprint due to large amounts of methane that an average cow produces. Agriculture accounts for 92% of the freshwater footprint of humanity; almost 35% relates to animal farming. The production of meat is directly and indirectly related to the loss of forests in South America, Amazon Rainforest and other areas of Brazil, Argentina and Paraguay. And many species face extinction or are under threat due to the destruction of natural environments. Sustainable alternative to going meat-free is entomophagy or insect farming which produces about 100 times less greenhouse gases per kg of mass organism gain. Edible insects like grasshoppers, crickets and mealworms are rich in protein and contain significantly higher sources of minerals such as iron, zinc, copper, and magnesium than beef. Regardless of its environmental benefits, entomophagy comes with its unique set of challenges.

Enabling CO2 neutral metallurgy for ferrochromium production using bio-based reducing agents

The metallurgical industry is a major source of anthropogenic greenhouse gas emissions. This study explores the replacement of fossil-reducing agents with potentially CO2-neutral bio-based reducing agents. Since reducing agents remove oxygen bonded with metal oxides present in the ore, they are a necessity for the production of metallic elements. The investigated metal is chromium, a major part of stainless steel, and therefore a highly relevant element for the transition from a fossil-based energy system to a renewable one. The state-of-the-art smelting reduction and pre-reduction process followed by subsequent smelting using various reducing agents are investigated in this article. The obtained products, metallurgical efficiencies, energy consumption and off-gas generation were compared. While the products produced with bio-based reducing agents are comparable with the reference trials using metallurgical coke regarding the major components in the metal, the concentration of detrimental phosphorus is significantly higher using bio-based reducing agents. The metallurgical efficiency of the process is comparable to the usage of bio-based reducing agents and coke. However, the energy consumption and the generation of off-gas is higher, when coke is replaced by bio-based reducing agents.

Indigo as a Low‐Cost Redox‐Active Sorbent for Electrochemically Mediated Carbon Capture

AbstractClimate change has driven the need for carbon capture to mitigate anthropogenic greenhouse gas emissions, yet current thermochemical methods are hampered by high energy intensities. Electrochemically mediated carbon capture (EMCC) utilizing redox‐active carbon dioxide (CO2) carriers is an attractive alternative for carbon capture. Here, an economical vat dye compound, indigo, is presented, which can reversibly capture and release CO2 upon electrochemical reduction and oxidation, respectively. Electrode and electrolyte engineering strategies are utilized to improve the reversibility and stability of indigo for EMCC. A bench‐scale prototypical fixed‐bed carbon capture device is constructed to demonstrate indigo's EMCC performance under various practically relevant conditions, such as simulated flue gas and extremely dilute sources pertinent to direct air capture. A hybrid sorbent electrode‐gas diffusion layer approach is revealed to alleviate CO2 mass transport limitations, achieving ≈80% CO2 capacity utilization under a 15% CO2 feed stream. Furthermore, a reactive‐diffusive mass transport model is developed to illustrate engineering approaches that can be universally applied to optimize fixed‐bed EMCC systems. This work advances the potential for a class of low‐cost sorbents for EMCC while underscoring the importance of molecular, electrolyte, materials, and device engineering strategies to enable high‐performance carbon capture.

Examining elevation and thermoregulatory trait differences of endemic tropical swallowtail butterflies to assess their vulnerability to climate change

Abstract Tropical montane insects are vulnerable to climate change if up‐hill range retractions reduce range sizes and increase extinction risk. Endemic species will be particularly at risk if they disproportionately occur at higher elevations, although threats may be ameliorated if they have morphological traits associated with improved thermoregulatory ability. We examine the vulnerability of endemic swallowtail butterflies on Sulawesi (Indonesia) to climate change by quantifying inter‐specific variation in traits associated with thermoregulation (body size and melanism) and whether species' traits are associated with the elevation of species' ranges. We collected data on size, melanism and elevation of 29 swallowtail butterfly species (Lepidoptera: Papilionidae) from 754 specimens at the Natural History Museum (United Kingdom) and the Zoologische Staatssammlung München (Germany). Endemic butterflies were less melanised (16 endemic species, mean = 83% melanised; 13 non‐endemic species = 89% melanised) but similar to non‐endemics in size (endemic, mean = 56 mm; non‐endemic = 53 mm) and elevation (endemic, mean = 345 m.a.s.l.; non‐endemic: 291 m). There was no evidence that species size or melanism patterns were related to elevation in either group. Few differences in elevation of endemic and non‐endemic species imply that endemic swallowtail butterflies are not disproportionately more threatened by climate‐driven mountaintop extirpation than non‐endemic species. Further work is needed to examine whether paler wings alter the ability of endemic species to thermoregulate and adapt to changing climates. In the absence of reductions in anthropogenic global greenhouse gas emissions, on‐going climate warming will continue to threaten tropical montane species.

Rehabilitating coral reefs in the Anthropocene

Coral reefs provide food and livelihoods for hundreds of millions of coastal people in over 100 countries. Recent global estimates for the total value of goods and services that they can generate indicate around US$ 105,000-350,000 per hectare per year, but local estimates of current total economic value can be one to two orders of magnitude lower. Unfortunately, coral reefs are under threat both from local human stressors (for example, sediment and nutrient run-off from agriculture, sewage discharges, dredging, destructive fishing, land 'reclamation', overfishing) and, increasingly, from stressors related to global climate change (not only El Niño Southern Oscillation-related marine heatwaves, which cause mass bleaching and mortality of corals, but also more frequent and powerful tropical cyclones and ocean acidification). Four successive mass-bleaching events on Australia's iconic Great Barrier Reef between 2016 and 2022 (plus another one currently underway) have focused world attention on the need for urgent action to protect coral reefs. It is clear that coral reef ecosystems will continue to decline unless anthropogenic greenhouse gas emissions are reduced and innovative management strategies are developed to assist adaptation.

Reducing energy and carbon footprint through diversified rainfed cropping systems

Agriculture is the second largest contributor (20%) to total anthropogenic greenhouse gas (GHG) emissions in the world. There is a need to identify energy and carbon efficient cropping systems that reduce GHG emission and improve environmental quality. Using life cycle assessment (LCA), we evaluated the four cropping systems namely fallow – chickpea (F–C); Sesbania – mustard (Ses–M); blackgram – chickpea (B–C); sorghum + cowpea – mustard (S+C–M) cultivated during the 2018-2022 period. The energy use pattern and the input-output relationship were analysed. Three measures were utilized to quantify carbon footprints: CFa, which denotes emissions per unit area; CFb, indicating emissions per kilogram of yield; and CFe, representing emissions per unit of economic output. The result indicates that non-renewable sources of energy (diesel and fertilizer) contributed more than ∼80% of the total energy consumed in the different cropping systems. The total energy requirement was the highest for S+C–M (16972 MJ ha–1), followed by Ses–M (14365 MJ ha–1), B–C (11132 MJ ha–1) and F–C (8679 MJ ha–1) cropping systems. The S+C–M cropping system also had the highest energy use efficiency (9.13) followed by F–C (6.03), B–C (5.41) and Ses–M (5.41). The fallow–chickpea cropping system had the lowest values of CFa, CFb, and CFe however, the highest carbon efficiency (10.7) and the carbon sustainability index (9.7) were computed in S+C–M cropping system. Our findings indicate that thoughtfully structured, varied crop systems that integrate legumes and forage crops have the potential to significantly reduce energy consumption and carbon emissions, while sustaining or potentially improving overall productivity within these systems.

Anthropogenic influence on seasonal extreme temperatures in eastern China at century scale

Due to the scarcity of observational data in the early 20th century, very limited research has explored the impact of human activities on temperature extremes at the regional scale. Here we used a newly developed homogenized near-surface air temperature dataset from the beginning of the 20th century to estimate the frequency and intensity of extreme temperatures in eastern China and evaluate their anthropogenic influence based on models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). We found clear increases in warm extremes and decreases in cold extremes since 1901 for both annual and seasonal mean temperatures, with more pronounced changes in recent decades. The most significant warming occurred in spring and winter, approximately double the smallest warming observed in autumn. The CMIP6 models generally replicated the century-scale warming in annual and seasonal temperature extremes, showing increases in the frequency and intensity of warm extremes and corresponding decreases in cold extremes. The optimal fingerprinting detections suggest that the century-scale warming can be clearly attributed to anthropogenic forcing, including changes in seasonal extreme temperatures. Most observed changes in extreme temperatures were attributable to anthropogenic greenhouse gas emissions, partially offset by a smaller negative impact from anthropogenic aerosol forcing, whereas natural forcing has played a minor role. These results provide important information for accurately projecting future changes in temperature extremes.

Forecasting the Mitigation Potential of Greenhouse Gas Emissions in Shenzhen through Municipal Solid Waste Treatment: A Combined Weight Forecasting Model

As a significant source of anthropogenic greenhouse gas emissions, the municipal solid waste sector’s greenhouse gas emission mode remains unknown, hampering effective decision-making on possible greenhouse gas emission reductions. Rapid urbanization and economic growth have resulted in massive volumes of municipal solid trash. As a result, identifying emission reduction routes for municipal solid waste treatment is critical. In this research, we investigate the potential of municipal solid waste treatment methods in lowering greenhouse gas (GHG) emissions in Shenzhen, a typical Chinese major city. The results showed that the combined treatment of 58% incineration, 2% landfill, and 40% anaerobic digestion (AD) had the lowest greenhouse gas emissions of about 5.91 million tons under all scenarios. The implementation of waste sorting and anaerobic digestion treatment of organic municipal solid waste after separate collection can reduce greenhouse gas emissions by simply increasing the incineration ratio.

Carbon dioxide enrichment affected flower numbers transiently and increased successful post-pollination development stably but without altering final acorn production in mature pedunculate oak (Quercus robur L.)

Acorn production in oak (Quercus spp.) shows considerable inter-annual variation, known as masting, which provides a natural defence against seed predators but a highly-variable supply of acorns for uses such as in commercial tree planting each year. Anthropogenic emissions of greenhouse gases have been very widely reported to influence plant growth and seed or fruit size and quantity via the ‘fertilisation effect’ that leads to enhanced photosynthesis. To examine if acorn production in mature woodland communities will be affected by further increase in CO2, the contents of litter traps from a Free Air Carbon Enrichment (FACE) experiment in deciduous woodland in central England were analysed for numbers of flowers and acorns of pedunculate oak (Quercus robur L.) at different stages of development and their predation levels under ambient and elevated CO2 concentrations. Inter-annual variation in acorn numbers was considerable and cyclical between 2015 and 2021, with the greatest numbers of mature acorns in 2015, 2017 and 2020 but almost none in 2018. The numbers of flowers, enlarged cups, immature acorns, empty acorn cups, and galls in the litter traps also varied amongst years; comparatively high numbers of enlarged cups were recorded in 2018, suggesting Q. robur at this site is a fruit maturation masting species (i.e., the extent of abortion of pollinated flowers during acorn development affects mature acorn numbers greatly). Raising the atmospheric CO2 concentration by 150 μL L−1, from early 2017, increased the numbers of immature acorns, and all acorn evidence (empty cups + immature acorns + mature acorns) detected in the litter traps compared to ambient controls by 2021, but did not consistently affect the numbers of flowers, enlarged cups, empty cups, or mature acorns. The number of flowers in the elevated CO2 plots’ litter traps was greater in 2018 than 2017, one year after CO2 enrichment began, whereas numbers declined in ambient plots. Enrichment with CO2 also increased the number of oak knopper galls (Andricus quercuscalicis Burgsdorf). We conclude that elevated CO2 increased the occurrence of acorns developing from flowers, but the putative benefit to mature acorn numbers may have been hidden by excessive pre- and/or post-dispersal predation. There was no evidence that elevated CO2 altered masting behaviour.

Representing natural climate variability in an event attribution context: Indo-Pakistani heatwave of 2022

Attribution of extreme climate events to global climate change as a result of anthropogenic greenhouse gas emissions has become increasingly important. Extreme climate events arise at the intersection of natural climate variability and a forced response of the Earth system to anthropogenic greenhouse gas emissions, which may alter the frequency and severity of such events. Accounting for the effects of both natural climate variability and the forced response to anthropogenic climate change is thus central for the attribution. Here, we investigate the reproducibility of probabilistic extreme event attribution results under more explicit representations of natural climate variability. We employ well-established methodologies deployed in statistical Earth System Model emulators to represent natural climate variability as informed from its spatio-temporal covariance structures. Two approaches towards representing natural climate variability are investigated: (1) where natural climate variability is treated as a single component; and (2) where natural climate variability is disentangled into its annual and seasonal components. We showcase our approaches by attributing the 2022 Indo-Pakistani heatwave to human-induced climate change. We find that explicit representation of annual and seasonal natural climate variability increases the overall uncertainty in attribution results considerably compared to established approaches such as the World Weather Attribution Initiative. The increase in likelihood of such an event occurring as a result of global warming differs slightly between the approaches, mainly due to different assessments of the pre-industrial return periods. Our approach that explicitly resolves annual and seasonal natural climate variability indicates a median increase in likelihood by a factor of 41 (95% range: 6-603). We find a robust signal of increased likelihood and intensification of the event with increasing global warming levels across all approaches. Compared to its present likelihood, under 1.5 °C (2 °C) of global near-surface air temperature increase relative to pre-industrial temperatures, the likelihood of the event would be between 2.2 to 2.5 times (8 to 9 times) higher. We note that regardless of the different statistical approaches to represent natural variability, the outcomes on the conducted event attribution are similar, with minor differences mainly in the uncertainty ranges. Possible reasons for differences are evaluated, including limitations of the proposed approach for this type of application, as well as the specific aspects in which it can provide complementary information to established approaches.

The Need for an Alternative Health Claim Process for Foods Based on Both Nutrient and Contaminant Profiles

Most authorized health claims on foods have been established on the basis of single dietary components, mainly micronutrients, such as vitamins, minerals, and possibly bioactives. Failure to sufficiently define and characterize the nutritional profile of a food product is 1 of the main reasons for rejection or incomplete status for thousands of health claim applications, whereas the food’s contaminant profile is simply not accounted for. The objective of this work was to highlight the accumulating scientific evidence supporting a reform of the health claim evaluation process for foods toward more holistic approaches. This would entail the characterization of multiple nutrient-contaminant pairs and contaminant mixture profiles at contaminant levels currently considered “safe,” including their interactions that would impact human health outcome(s) in a net positive or negative direction. The notion of a stable nutritional profile in food commodities has been challenged by studies reporting a variable food contaminant content and a declining content of proteins/micronutrients in crops due to anthropogenic greenhouse gas emissions. A holistic approach in the health claim process for foods would entail the incorporation of cumulative risk assessment and/or risk-benefit protocols that effectively combine health risks and benefits associated with multiple nutritional and contaminant attributes of the food/diet under evaluation.

Greenhouse gases emissions from aquaculture ponds: Different emission patterns and key microbial processes affected by increased nitrogen loading

Global aquaculture production is expected to rise to meet the growing demand for food worldwide, potentially leading to increased anthropogenic greenhouse gases (GHG) emissions. As the demand for fish protein increases, so will stocking density, feeding amounts, and nitrogen loading in aquaculture ponds. However, the impact of GHG emissions and the underlying microbial processes remain poorly understood. This study investigated the GHG emission characteristics, key microbial processes, and environmental drivers underlying GHG emissions in low and high nitrogen loading aquaculture ponds (LNP and HNP). The N2O flux in HNP (43.1 ± 11.3 μmol m−2 d−1) was significantly higher than in LNP (−11.3 ± 25.1 μmol m−2 d−1), while the dissolved N2O concentration in HNP (52.8 ± 7.1 nmol L−1) was 150 % higher than in LNP (p < 0.01). However, the methane (CH4) and carbon dioxide (CO2) fluxes and concentrations showed no significant differences (p > 0.05). N2O replaced CH4 as the main source of Global Warming Potential in HNP. Pond sediments acted as a sink for N2O but a source for CH4 and CO2. The △N2O/(△N2O + △N2) in HNP (0.015 ± 0.007 %) was 7.7-fold higher than in LNP (0.002 ± 0.001 %) (p < 0.05). The chemical oxygen demand to NO2-N ratio was the most important environmental factor explaining the variability of N2O fluxes. Ammonia-oxidizing bacteria driven nitrification in water was the predominant N2O source, while comammox-driven nitrification and nosZII-driven N2O reduction in water were key processes for reducing N2O emission in LNP but decreased in HNP. The strong CH4 oxidization by Methylocystis and CO2 assimilation by algae resulted in low CH4 emissions and CO2 sink in the aquaculture pond. The Mantel test indicated that HNP increased N2O fluxes mainly through altering functional genes composition in water and sediment. Our findings suggest that there is a significant underestimation of N2O emissions without considering the significantly increased △N2O/(△N2O + △N2) caused by increased nitrogen loading.

Measurement of Road Transport Emissions. Case Study: Centinela-La Rumorosa Road, Baja California, México

Air pollution is a global issue, and the transportation sector is recognized as the third-largest contributor to anthropogenic greenhouse gas emissions. Vehicles emit a range of chemical compounds because of the combustion process. The nature and quantity of these emissions depend on the vehicle’s characteristics, the road, and weather conditions. These emissions require special attention due to the adverse effects contributing to global warming and human health. In this regard, diagnosing and monitoring air quality is crucial for understanding the number of emissions generated by various sources. However, in developing countries, the necessary data for conducting such analyses are not always available. The purpose of this study is to estimate emissions specifically generated from road operations. To achieve this, the HDM-4 calculation tool is utilized to estimate emissions. This tool was applied in Baja California, Mexico, on the Centinela-La Rumorosa highway. The results obtained show that annually, 372.5 tons of pollutant emissions are generated, composed of HC, CO, CO2, NOx, PM, SO2, and PB, covering a mere 128 km of length within a state road network spanning 11,429 km. This highlights the necessity of implementing strategies to reduce the environmental impact generated by vehicular operations on roads in developing countries.

Complete elimination of methane formation in stored livestock manure using plasma technology

Plasma-based nitrogen fixation has recently been shown to be applicable in the domain of manure management, as it has the ability to reduce ammoniacal nitrogen losses and increase the nitrogen content of organic wastes, with air and electricity as the only input. In addition, the plasma treatment confers antimicrobial properties, which we hypothesize to be transferable to methanogenic archaea and hence prevent methane formation during manure storage – a major contributor to global anthropogenic greenhouse gas emissions. In this work we compared the methane formation from cow manure to the methane formation in nitrogen enriched cow manure, kept in two outdoor storage tanks for 70–80 summer days over three consecutive years. In all instances, the methane formation was eliminated completely. To investigate the cause of inhibition, a controlled incubation experiment was conducted to show that neither the acidification nor the addition of nitrate or nitrite, alone or in combination, could explain the inhibition of methanogenesis and denitrification that occurred in plasma treated cow manure at moderate pH.

Utilisation of carbon dioxide in the synthesis of multifunctional AB-type carbonated hydroxyapatite compositions

Carbon dioxide utilisation is a rapidly growing field that aims to reduce the magnitude of anthropogenic greenhouse gas emissions by using CO2 captured from point sources in the production of useful materials. AB-type carbonated hydroxyapatites containing 2.28–10.35 wt% of carbonate were synthesised in this work via aqueous precipitation reaction, with carbonate ions introduced by bubbling CO2 gas into water used in the reaction. Analysis of FTIR spectra demonstrated that carbonate ions had substituted onto both hydroxyl and phosphate sites. An AB-type carbonated hydroxyapatite with a carbonate content of 14.68 wt% was obtained after an hourlong heat treatment in dry CO2 at 600 °C, a very large degree of carbonation for such a material. Poor thermal stability of this material however meant that a full structural determination from refinement of XRD data could not be carried out. Additionally, further work is required to test the prepared materials in fields including carbon capture and wastewater treatment before this can truly be considered a viable route for carbon dioxide utilisation.

The potential of urban irrigation for counteracting carbon-climate feedback

Global climate changes, especially the rise of global mean temperature due to the increased carbon dioxide (CO2) concentration, can, in turn, result in higher anthropogenic and biogenic greenhouse gas emissions. This potentially leads to a positive loop of climate–carbon feedback in the Earth’s climate system, which calls for sustainable environmental strategies that can mitigate both heat and carbon emissions, such as urban greening. In this study, we investigate the impact of urban irrigation over green spaces on ambient temperatures and CO2 exchange across major cities in the contiguous United States. Our modeling results indicate that the carbon release from urban ecosystem respiration is reduced by evaporative cooling in humid climate, but promoted in arid/semi-arid regions due to increased soil moisture. The irrigation-induced environmental co-benefit in heat and carbon mitigation is, in general, positively correlated with urban greening fraction and has the potential to help counteract climate–carbon feedback in the built environment.

Pioneering historical LCA - A perspective on the development of personal carbon footprint 1860–2020 in Denmark

Mitigating climate change by reducing anthropogenic greenhouse gas emissions is considered an urgent challenge for society. In this context, different philosophies exist. A classic debate, referred to as “boomsters vs. doomsters”, asks whether humanity's drive for technological innovations will mitigate climate change, or whether it is justifiable to compromise our living standards, affluence, and consumption patterns. A Danish research project has elucidated this topic through cross-collaboration between historians and engineers by quantifying the personal consumption-based carbon footprint (CF) of Danish citizens, taking into account the consumption segments of food, transport, housing, and furniture. Quantification is conducted through life-cycle assessments (LCA) of five decadal timesteps during the period 1860–2020. As only one other study conducting historical (retrospective) LCA with an extensive time horizon was identified in the scientific literature, our own study provides novel insights by exploring possible approaches in this field. Historical LCA has many similarities with prospective (future) LCA, providing inspiration to the approach. The main challenge of the study is to adjust both foreground and background systems in the inventory modelling phase. Data is largely based on national statistics, books, museum case studies, expert testimonials, and proxies such as using the steam turbine as an indicator of improvements to technological efficiency over time. The results show a slightly declining carbon footprint in the period 1860–1930, from 7.7 to 6.6 t CO2-eq per capita annually. Unsurprisingly the footprint peak is not found until the 1970s, at 11 t, reducing to 5.4 t in the 2010s. The residential energy consumption segment contributes half of this CF, followed by transportation by road and rail. Discussion of the results shows that whether technology can mitigate the impact from the increase in affluence depends on the specific consumption segment. For housing combined with residential energy, the results show that technology can mitigate increases in CF, despite the comforts of home having only increased over time. For the transportation segment, however, the past century has seen an eightfold increase in CF due to the pronounced evolution of personal modes of transportation. The findings suggests that the “boomsters vs. doomsters” debate is not so black and white after all. We further suggest that historical LCA, in tandem with prospective LCA, can provide valuable insights for decision support to facilitate a green transition and hence a green future.