• Energy Research

Enhanced weathering (EW) is one of the most promising negative emissions technologies urgently needed to limit global warming to at least below 2 °C, a goal recently reaffirmed at the UN Global Climate Change conference (i.e., COP26). EW relies on the accelerated dissolution of crushed silicate rocks applied to soils and is considered a sustainable solution requiring limited technology. While EW has a high theoretical potential of sequestering CO2, research is still needed to provide accurate estimates of carbon (C) sequestration when applying different silicate materials across distinct climates and major soil types in combination with a variety of plants. Here we elaborate on fundamental advances that must be addressed before EW can be extensively adopted. These include identifying the most suitable environmental conditions, improving estimates of field dissolution rates and efficacy of CO2 removal, and identifying alternative sources of silicate materials to meet future EW demands. We conclude with considerations on the necessity of integrated modeling-experimental approaches to better coordinate future field experiments and measurements of CO2 removal, as well as on the importance of seamlessly coordinating EW with cropland and forest management.

AbstractThe Mediterranean basin is particularly prone to climate change and vulnerable to its impacts. One of the most relevant consequences of climate change, especially for the southern Mediterranean regions, is certainly water scarcity as result of a reduction of surface runoff and groundwater levels. Despite the progress achieved in recent years in the field of climate change and its impact on water resources, results and outcomes should be treated with due caution since any future climate projection and derived implications are inevitably affected by a certain degree of uncertainty arising from each different stage of the entire modeling chain. This work offers a comprehensive overview of recent works on climate change in the Mediterranean basin, mainly focusing on the last ten years of research. Past and future trends on different components of the hydrological balance are discussed in a companion paper (Noto et al. 2022), while the present paper focuses on the problem of water availability and water scarcity. In addition, the work aims to discuss the most relevant sources of uncertainty related to climate change with the aim to gain awareness of climate change impact studies interpretation and reliability.

Extreme rainfall events have been more frequent in recent decades, potentially as a climate change effect. This has been leading to a higher risk of the failure of existing hydraulic infrastructures, and to a higher awareness regarding the unreliability of design rainfall calculated with reference to historical data recorded in the last century. With this in mind, the present study questions the stationary assumption of the rainfall Depth–Duration–Frequency curves commonly used in Sicily, the biggest island of the Mediterranean Sea. Quantiles derived from the most up-to-date regional method, regarding Sicily, based on observations in the period 1928–2010, have been compared with those extracted from a high-resolution dataset related to the period 2002–2022, provided by the SIAS agency. The results showed a remarkable underestimation of the rainfall quantiles calculated with the regional approach, especially at the shortest durations and low return periods. This means that new hydraulic works should be designed with reference to longer return periods than in the recent past, and those that currently exist may experience a higher risk of failure. Future investigation of this aspect is crucial for enhancing the effectiveness of water management and detecting hydrological risks under a changing climate.

Nowadays, the effects of global warming are becoming increasingly evident and dangerous at every latitude of the planet. In such a context, the Mediterranean basin turns out to be a "hotspot". Reductions in precipitation, especially in the summer season, and increases in the intensity and frequency of extreme events, such as droughts and heat waves, have been observed in regions bordering the Mediterranean Sea in recent decades. In particular, heat waves may have numerous negative impacts on human health, environment, agriculture, and the energy sectors. Indeed, consecutive days with extremely high temperatures, combined with high humidity, poses a high health risk to the population. Moreover, in combination with other extreme events such as drought, they can also promote the occurrence of forest fires causing further damage to ecosystems.The goal of this work is to analyze the characteristics of heat waves that have occurred in Sicily over the last two decades, from 2002 to 2021, to assess the existence of any trend over the period under consideration. For the identification and characterization of the heat waves, hourly data of air temperature and relative humidity have been collected from 101 stations of the Sicilian Agrometeorological Information Service (Servizio Informativo Agrometeorologico Siciliano - SIAS) network. Heat waves have been defined on the base of three variables at the daily scale: maximum air temperature, minimum air temperature, and daily maximum values of the Heat Index, which puts together temperature and relative humidity. A heat wave is detected when the daily maximum/minimum air temperature and the maximum daily Heat Index value exceed for at least two consecutive days the value of a threshold usually calculated as a function of the 90th percentile of the distribution of daily maximum/minimum temperatures and daily Heat Index. For each year, the number of events, number of days of heat waves, duration of the longest event, magnitude of the season (i.e., the number of days between the first day of the first heat wave and the last day of the last heat wave), and intensity (i.e., the average of the differences for each event between the mean temperature value and the threshold to define the occurrence of the heat waves) have been assessed. A trend analysis has been carried out by means of a simple linear regression on all the above-mentioned variables. Results reveal increasing trends for most of the Sicilian gauges, although not for all the above-mentioned variables, showing that in the last 20 years the frequencies of occurrence and magnitude of heat waves have increased, most likely as a climate change effect, and confirming what other studies have found out for other Mediterranean regions in the last years.