Colombia’s GHG Emissions Reduction Scenario: Complete Representation of the Energy and Non-Energy Sectors in LEAP

The signatory countries of the Paris Agreement must submit their updated Intended National Determined Contributions (INDCs) to the UNFCCC secretariat every five years. In Colombia, this activity was historically carried out with a wide set of diverse non-interconnected sector-specific models. Given the complexity of GHG emissions reporting and the evaluation of mitigation actions on a national scale, the need for a centralized platform was evident. Such approach would allow the integration and analysis of potential interactions among sectors, as well as to guarantee the homogeneity of assumptions and input parameters. In this paper, we describe the construction of an integrated bottom-up LEAP model tailored to the Colombian case, which covers all IPCC sectors. An integrated model facilitates capturing synergies and intersectoral interactions within the national GHG emissions system. Hence, policies addressing one sector and influencing others are identified and correctly assessed. Thus, 44 mitigation policies and mitigation actions were included in the model, in this way, identifying the sectors directly and being indirectly affected by them. The mitigation scenario developed in this paper reaches a reduction of 28% of GHG emissions compared with the reference scenario. The importance of including non-energy sectors is evident in the Colombian case, as GHG emission reductions are mainly driven by AFOLU. The first section describes the GHG emissions context in Colombia. Next, we describe the model structure, main input parameters, assumptions, considerations, and used LEAP functionalities. Results are presented from a GHG emissions accounting and energy demand perspective. The model allows for the correct estimate of the scope and potential of mitigation actions by considering indirect, unintended emissions reductions in all IPCC categories, as well as synergies with all mitigation actions included in the mitigation scenario. Moreover, the structure of the model is suitable for testing potential emission trajectories, facilitating its adoption by official entities and its application in climate policymaking.

Climate Change and Thermal Comfort in Top Tourist Destinations—The Case of Santorini (Greece)

The Mediterranean area is one of the most visited tourist destinations of the world, but it has also been recognized as one of the most vulnerable to climate change areas worldwide with respect to increased thermal risk. The study focuses on a top worldwide tourist destination of the Mediterranean, Santorini Island in Greece, and aims to assess the past, present and future thermal environment in the island based on the advanced Universal Thermal Climate Index (UTCI). The study utilizes historical observations capturing past (late 19th to early 20th century) and more recent (1982–2019) time periods, while future projections are realized based on four regional climate models (RCMs) under the weak mitigation scenario (RCP4.5) and the non-mitigation scenario with high emissions (RCP8.5). The frequency of cold stress conditions at midday decreases during winter and early spring months by up to 19.8% (January) in the recent period compared to the historical one, while heat stress conditions increase in summer by up to 22.4% (August). Future projections suggest progressive shifts of the UTCI towards higher values in the future and an increase in the exposure time under heat stress depending on the RCM and adopted scenario. The increase in moderate and strong heat stress conditions is mainly expected during the summer months (June, July, August); nevertheless, a noticeable increase is also foreseen in September and May. The highest occurrences of favorable (no thermal stress) conditions are also projected to shift by one month, from June to May and from September to October, in the future.

Reducing future air pollution-related premature mortality over Europe by mitigating emissions: assessing an 80 % renewable energies scenario

Worldwide air quality has worsened in the last decades as a consequence of increased anthropogenic emissions, in particular from the sector of power generation. The evidence of the effects of atmospheric pollution (and particularly fine particulate matter, PM2.5) on human health is unquestionable nowadays, producing mainly cardiovascular and respiratory diseases, morbidity and even mortality. These effects can even enhance in the future as a consequence of climate penalties and future changes in the population projected. Because of all these reasons, the main objective of this contribution is the estimation of annual excess premature deaths (PD) associated to PM2.5 on present (1991–2010) and future (2031–2050) European population by using non-linear exposure-response functions. The endpoints included are Lung Cancer (LC), Chronic Obstructive Pulmonary Disease (COPD), Low Respiratory Infections (LRI), Ischemic Heart Disease (IHD), cerebrovascular disease (CEV) and other Non-Communicable Diseases (other NCD). PM2.5 concentrations come from coupled chemistry-climate regional simulations under present and RCP8.5 future scenarios. The cases assessed include the estimation of the present incidence of PD (PRE-P2010), the quantification of the role of a changing climate on PD (FUT-P2010) and the importance of changes in the population projected for the year 2050 on the incidence of excess PD (FUT-P2050). Two additional cases (REN80-P2010 and REN80-P2050) evaluate the impact on premature mortality rates of a mitigation scenario in which the 80 % of European energy production comes from renewables sources. The results indicate that PM2.5 accounts for nearly 895,000 [95 % confidence interval (95 % CI) 725,000-1,056,000] annual excess PD over Europe, with IHD being the largest contributor to premature mortality associated to fine particles in both present and future scenarios. The case isolating the effects of climate penalty (FUT-P2010) estimates a variation +0.2 % on mortality rates over the whole domain. However, under this scenario the incidence of PD over central Europe will benefit from a decrease of PM2.5 (−2.2 PD/100,000 h.) while in eastern (+1.3 PD/100,000 h.) and western (+0.4 PD/100,000 h.) Europe PD will increase due to increased PM2.5 levels. The changes in the projected population (FUT-P2050) will lead to a large increase of annual excess PD (1,540,000, 95 % CI 1,247,000-1,818,000), +71.96 % with respect to PRE-P2010 and +71.67 % to FUT-P2010) due to the aging of the European population. Last, the mitigation scenario (REN80-P2050) demonstrates that the effects of a mitigation policy increasing the ratio of renewable sources in the energy mix energy could lead to a decrease of over 60,000 (95 % CI 48,500-70,900) annual PD for the year 2050 (a decrease of −4 % in comparison with the no-mitigation scenario, FUT-P2050). In spite of the uncertainties inherent to future estimations, this contribution reveals the need of the governments and public entities to take action and bet for air pollution mitigation policies.

Equitable mitigation to achieve the 1.5 °C goal in the Mediterranean basin

The mitigation required to achieve the 1.5 °C goal of the Paris Agreement entails drastic emission reductions. The mentioned goal is of special interest for regions like the Mediterranean where the average temperature is rising above the world average with the consequential risk for the future viability of its different ecosystems. The objective of this work is to analyze if the commitments of the Mediterranean basin countries submitted under the Paris Agreement framework are in line with the 1.5 °C goal. For this analysis, the cumulative emissions of the current Nationally Determined Contributions of these countries until 2030, are compared with the result obtained from distributing the cumulative greenhouse gas emissions compatible with the 1.5 °C global mitigation scenario between 2018 and 2100. This distribution is obtained using the Model of Climate Justice that allocates the global emissions by using equity criteria (equality and responsibility) that take into consideration the historical responsibility for each country, in the period from 1994 to 2017. There are two main conclusions from the analysis of the NDCs. Firstly, it is concluded that the Mediterranean basin countries as a whole, are not in line with the 1.5 °C goal, because by 2030, 77% of the emissions budget that will be available until 2100, based on the equity criteria aforementioned, will already have been emitted. And, secondly, when the NDCs for each one of the countries are compared some significant differences in the degree of ambition can be seen.

Boosting Energy Efficiency and Solar Energy inside the Residential, Commercial, and Public Services Sectors in Mexico

The residential, commercial, and public sectors consume between 20% and 30% of final energy demand worldwide. Due to the intensive use of fossil fuels and conventional electricity, they also have an important participation in the emission of greenhouse gases (GHG). Taking Mexico as a case study, this article develops an alternative scenario that considers that in these sectors, buildings can generate energy for self-consumption or to supply it to the power network—for which four solar energy options are analyzed. In addition, to manage and rationalize the energy demand of these buildings, eight energy efficiency measures are studied. These options were selected on the basis that they are technically and economically feasible to implement in buildings in Mexico. The results reveal that by 2030, in relation to the GHG trend scenario, this mitigation scenario reduces 23.5 million tons of carbon dioxide equivalent (MtCO2e) in the residential (19 MtCO2e), commercial (2.6 MtCO2e), and public services sectors (1.9 MtCO2e), while by 2035 it reaches 45 MtCO2e; which far exceed the avoided emissions goals established in Mexico’s nationally determined contributions (NDC) for 2030 (5 MtCO2e) for the residential and commercial sectors. Therefore, it is possible to increase the ambition for mitigation in these sectors, as well as including the public sector, in a renewed Mexico’s NDC. This mitigation scenario generates a total economic benefit of $7.7 billion, which means that it does not generate an overall incremental cost, but requires an incremental investment of over $9 billion USD, which is a financing challenge to achieve this scenario.

Climate projections in Lake Maggiore watershed using statistical downscaling model

Precipitation and temperature over the Lake Maggiore watershed greatly influence its water balance. Local communities from both Italy and Switzerland rely on the watershed for agriculture, tourism and hydropower production. Accurate climate projections in this area are vital in dealing with their impacts and yet are still lacking. Future climate was assessed by applying the Statistical DownScaling Model (SDSM) and using CanESM2 predictors. Three scenarios defined by RCP2.6, RCP4.5 and RCP8.5 were adopted. Based on our results, SDSM is to a certain degree applicable for simulating precipitation and temperature in an Alpine area. Results indicate that warming from now until the end of the century will be about 2 to 3 times greater without global mitigation. Temperature is estimated to increase throughout the 21st century, with a stronger warming trend in the northeastern part of the region than in the southwestern part. The strength of the warming at the end of the century highly depends on the scenario considered, with an increase up to 1.7°C for the mitigation scenario RCP2.6 compared to 4.2°C for the unmitigated scenario RCP8.5. Seasonal precipitation is expected to change depending on the future scenarios. Most of the region is expected to display a seasonally positive precipitation change during the cold season and vice versa, resulting in a shift in the peak rainy season from autumn to winter. These findings suggest that the area might be vulnerable to global change and will provide useful insight to develop a better strategy for the management of water resources and to study the adoptive measures to manage flood disasters.

Inherent Uncertainty Disguises Attribution of Reduced Atmospheric CO2 Growth to Mitigation for up to a Decade

<p>On inter-annual time scales the growth rate of atmospheric CO<sub>2</sub> is largely driven by the response of the land and ocean carbon sinks to climate variability. Therefore, climate mitigation in terms of emission reductions can be disguised by internal variability.<br>However, the probability that emission reductions induced by a policy change caused reductions in atmospheric CO<sub>2</sub> growth trend is unclear. <br>We use 100 historical MPI-ESM simulations and interpret mitigation in 2020 as a policy shift from Representative Concentration Pathway 4.5 to 2.5 in a comprehensive causation attribution framework.<br>Here we show that five-year CO<sub>2</sub> trends are higher in 2021-2025 than over 2016-2020 in 30% of all realizations in the mitigation scenario, compared to 52% in the non-mitigation scenario. Therefore, mitigation is sufficient or necessary to cause these trends by 42% or 31%, respectively and therefore far from certain. <br>A stronger increase in atmospheric CO<sub>2</sub> trends despite emission reductions is possible when the global carbon cycle triggered by internal climate variability releases more CO<sub>2</sub> than mitigation saves. Such trends might occur for of up to ten years. Certainty that mitigation causes trend reductions is only reached after ten or fifteen years, respectively of the type of causation.<br>Our analysis showcases the inherent uncertainty of near-term CO<sub>2</sub> projections. Assessments of the efficacy of mitigation in the near term are incomplete without quantitatively considering internal variability.</p>

Past warming trend constrains future warming in CMIP6 models

<div>Future global warming estimates have been similar across past assessments, but several climate models of the latest Sixth Coupled Model Intercomparison Project (CMIP6) simulate much stronger warming, apparently inconsistent with past assessments. Here we show that projected future warming is correlated with the simulated warming trend during recent decades across CMIP5 and CMIP6 models, enabling us to constrain future warming based on consistency with the observed warming. These findings carry important policy-relevant implications: the observationally-constrained CMIP6 median warming in high emissions and ambitious mitigation scenarios is over 16% and 14% lower by 2050 compared to the raw CMIP6 median, respectively, and over 14% and 8% lower by 2090, relative to 1995-2014. Observationally-constrained CMIP6 warming is consistent with previous assessments based on CMIP5 models, and in an ambitious mitigation scenario, the likely range is consistent with reaching the Paris Agreement target.</div><div> </div><div>Reference: </div><div>Tokarska, K.B.<sup>†</sup>, Stolpe, M.B.<sup>†</sup>, Sippel, S., Fischer, E.M., Smith, C.J., Lehner, F., and Knutti, R. (2020). Past warming trend constrains future warming in CMIP6 models. <em>Science Advances</em>  (accepted).</div><div><sup>†</sup>equal first authors</div>