Marginal Abatement Cost of Carbon Emissions under Different Shared Socioeconomic Pathways

Future emissions scenarios have served as a primary basis for assessing climate change and formulating climate policies. To explore the impact of uncertainty in future emissions scenarios on major outcomes related to climate change, this study examines the marginal abatement cost (MAC) of carbon emissions under the latest Shared Socioeconomic Pathways (SSPs) subject to the economic optimum and the 1.5 °C temperature increase constraint using the Epstein-Zin (EZ) climate model. Taking the ”Regional Rivalry” (SSP3) scenario narrative under the economic optimum as a representative case, the expected MACs per ton CO2 equivalent (CO2e) emissions in the years 2015, 2030, 2060, 2100, and 2200 are: $102.08, $84.42, $61.19, $10.71, and $0.12, respectively. In parallel, the associated expected average mitigation rates (AMRs) are 0%, 63%, 66%, 81%, and 96%, respectively. In summary, in a world developing towards regional rivalry (SSP3) or fossil-fueled development (SSP5) with high mitigation pressure, the MAC values have approximately doubled, compared with the sustainability (SSP1) and inequality (SSP4) storylines with low mitigation pressure levels. The SSP2 (Middle of the Road) shows a moderate MAC decreasing trend with moderate mitigation pressure. The results provide a carbon price benchmark for policy makers with different attitudes towards the unknown future and can be used to formulate carbon mitigation strategy to respond to specific climate goals.

Understanding the uncertainty cascaded in climate change projections for agricultural decision making

Climate projections have confirmed the need to adapt to a changing climate, but have been less beneficial in guiding how to effectively adapt. The reason is the uncertainty cascade, from assumptions about future emissions of greenhouse gases to what that means for the climate to real decisions on a local scale. Each of the steps in the process contains uncertainty and these uncertainties from various levels of the assessment accumulate. This cascade of uncertainty should be critically analyzed to inform decision makers about the certain range of future changes. Most widely used approaches like Bayesian and Monte Carlo gives specific values of parameters and their confidence, yet for agricultural decision making the range of possible changes itself is required as such to understand impact at every point of these ranges. This paper addresses these issues and examines the uncertainties in climate projections at a local scale. In the study locations (Coimbatore and Thanjavur), irrespective of the models, scenarios and time slices, the maximum and minimum temperatures are projected to increase with seasonal variations. With certainty, the projected increase in maximum and minimum temperature over Coimbatore is 0.2 to 4.1 ºC and 0.3 to 5.3 ºC and over Thanjavur is 0.3 to 4.6 ºC and 0.2 to 5.2 ºC, respectively. Rainfall is projected to vary between a decrease of 15.0 to an increase of 73.1 percent for Coimbatore and a decrease of 15.3 to an increase of 80.7 per cent for Thanjavur during the 21st century. On comparing the monsoon seasons, southwest monsoon (SWM) is projected to have a higher increase in both maximum and minimum temperature than northeast monsoon (NEM) for both the study locations, similar to their current trends. Rainfall is projected to increase more in NEM than in SWM.

The role of concrete in life cycle greenhouse gas emissions of US buildings and pavements

Concrete is a critical component of deep decarbonization efforts because of both the scale of the industry and because of how its use impacts the building, transportation, and industrial sectors. We use a bottom-up model of current and future building and pavement stocks and construction in the United States to contextualize the role of concrete in greenhouse gas (GHG) reductions strategies under projected and ambitious scenarios, including embodied and use phases of the structures’ life cycle. We show that projected improvements in the building sector result in a reduction of 49% of GHG emissions in 2050 relative to 2016 levels, whereas ambitious improvements result in a 57% reduction in 2050, which is 22.5 Gt cumulative saving. The pavements sector shows a larger difference between the two scenarios with a 14% reduction of GHG emissions for projected improvements and a 65% reduction under the ambitious scenario, which is ∼1.35 Gt. This reduction occurs despite the fact that concrete usage in 2050 in the ambitious scenario is over three times that of the projected scenario because of the ways in which concrete lowers use phase emissions. Over 70% of future emissions from new construction are from the use phase.

Greenhouse Gas Emissions and Mitigation Measures within the Forestry and Other Land Use Subsector in Malawi

Analysing past trends of greenhouse gas (GHG) emissions remains indispensable to the understanding of current GHG emissions, thereby enabling prediction of future emissions as well as development of their mitigative pathways. This study quantified GHG emissions within the Forest and Other Land Use (FOLU) subsector in Malawi for the period 2011 to 2020. Results indicate that Malawi’s GHG emissions in the FOLU subsector fluctuated but decreased by 0.84 MtCO2e (13%) from 2011 to 2020, averaging to −1.3% annually. The GHG emissions of different categories within the subsector were highly significant ( p < 0.001 ) and contributed the highest (99.72%) of the total variation. Forestland contributed the highest (74%) of the subsector category emissions, followed by biomass burning (19%). The uncertainties for the estimated GHG emissions were low (<15%). This shows that the estimated GHG emissions within the FOLU subsector were significantly minimised. Notable interventions that have abated the emissions include afforestation and natural/assisted regeneration; protection and conservation of protected areas through the REDD+ mechanism; establishment of seed banks for raising drought-tolerant tree species; and breeding of fast-growing and drought-tolerant tree species; as well as screening of disease and pest-resistant species and promotion of biological control.

Development of scenarios for future emissions of chemicals from agricultural, industrial and urban systems

&lt;p&gt;Water is an essential resource for human life and the environment. The widespread use of chemicals in daily life has led to significant water quality concerns. During the production phase, the use phase as well as after use, (residues of) these chemicals can enter the environment and water systems. Furthermore, the use and production of chemicals are increasing rapidly, driven by mainly population growth, urbanisation and economic growth. Increased use leads to further emissions of chemicals to water, posing significant water quality concerns. Henceforth there is an urgent need to understand the linkage between society and production and consumption of chemicals to explore possible changes in water quality.&lt;/p&gt;&lt;p&gt;Socio-economic scenario analysis is a useful tool to investigate the long-term consequences of future change and mitigation options. While scenarios have been broadly applied to understand air pollution, this not yet the case for chemical pollution to surface waters. In this work, we propose a general framework to develop scenarios for the future emissions of chemicals to water by using the Shared Socio-economic Pathways (SSP). The framework follows the basic elements of the scenario development process by defining the current system, describe the changes in emissions with scenario drivers and elaboration to the future. The framework is then tested on a set of selected &amp;#8216;example&amp;#8217; chemicals that represent broader chemical groups of pharmaceuticals (Ibuprofen and Diclofenac), pesticides (Terbuthylazine) and industrial chemicals (Cadmium and Di-ethyl phthalate). Chemical emissions to water over the past years were used to understand their yearly trends and patterns over the European countries. Lastly, the emission scenarios for chemicals for 2050 were developed by using SSP drivers from the IMAGE Integrated assessment model as an input to the empirical emission models. The three SSP scenarios: SSP1 (&quot;Sustainability&quot;), SSP2 (&quot;Middle of the Road&quot;) and SSP3 (&quot;Regional Rivalry&quot;) focusing on Europe were included. Additionally, the developed scenarios also describe mitigation efforts.&lt;/p&gt;&lt;p&gt;The results of emission scenarios displayed an increase in emissions up to 2050 for the exemplary chemicals in Western Europe for all three scenarios SSP1, SSP2 and SSP3. While the emissions of chemicals linearly decreased in Eastern Europe for the same period. SSP3 showed the highest emissions in 2050 except for cadmium emissions from wastewater treatment plants. The results showed that the framework helps in understanding the possible influence of socio-economic changes on use and emissions of chemicals which can be a part of future risk assessments. While the framework can be extended similarly to other pharmaceuticals and pesticides, it requires a detailed understanding of complex emission sources for industrial chemicals.&lt;/p&gt;

A future perspective of historical contributions to climate change

Countries’ historical contributions to climate change have been on the agenda for more than two decades and will most likely continue to be an element in future international discussions and negotiations on climate. Previous studies have quantified the historical contributions to climate change across a range of choices and assumptions. In contrast, we quantify how historical contributions to changes in global mean surface temperature (GMST) may change in the future for a broad set of choices using the quantification of the shared socioeconomic pathways (SSPs). We calculate the contributions for five coarse geographical regions used in the SSPs. Historical emissions of long-lived gases remain important for future contributions to warming, due to their accumulation and the inertia of climate system, and historical emissions are even more important for strong mitigation scenarios. When only accounting for future emissions, from 2015 to 2100, there is surprisingly little variation in the regional contributions to GMST change between the different SSPs and different mitigation targets. The largest variability in the regional future contributions is found across the different integrated assessment models (IAMs). This suggests the characteristics of the IAMs are more important for calculated future historical contributions than variations across SSP or forcing target.

Asia Pacific road transportation emissions, 1900–2050

We present an assessment of the historical and future emissions of on-road transportation and strategies to tackle emission challenges in Asia Pacific.