Earth Science at IgMin Research | Science Group

The astronomical theory of ice ages is widely accepted. Yet, it is not abundantly clear just exactly what the astronomical theory of ice ages is, other than the vague statement that variations in the Earth's orbit produce changes in solar irradiance at northern latitudes which is somehow related to the formation and termination of ice ages. Periodic variations in the Earth’s orbit produce variations in the insolation at high latitudes and ice ages begin on down lobes of insolation and terminate on up lobes of insolation. However, not all ...down lobes create ice ages and not all up lobes produce terminations. The ice ages changed character at the so-called mid-Pleistocene transition, about a million years ago. There is no current physical explanation for these difficulties with the astronomical theory. A reasonable explanation has been developed, that solidifies the astronomical theory by explaining the rise and fall of ice ages in both eras. The solar power absorbed at high northern latitudes depends on the insolation and absorptivity of the surface. The absorptivity is particularly affected by the obliquity in the pre-MPT era, and by dust deposits late in the post-MPT era. When these are included, it can be explained why some down lobes produce ice ages, and some up lobes produce terminations in both eras. In the pre-MPT era, ice ages originate when the insolation enters a down lobe and the obliquity is minimal (higher reflectivity) and ice ages terminate at a coincidence of high insolation and high obliquity (lower reflectivity). These links between SIHL and obliquity tend to be repetitive with approximately 41,000-year spacing. In the post-MPT era, ice ages also originate at a down lobe of SIHL. However, once an ice age is started, each successive up lobe in SIHL might cause a slight decrease in ice volume but doesn’t bring about a termination. After several precession cycles, high dust levels increase absorptivity, and the next-up lobe produces a termination.Read more

Potential Evapotranspiration (PET) is an important variable for monitoring daily agricultural activity as well as meteorological drought. Therefore, it is necessary to investigate the influence of different options of the physical dynamical downscaling and boundary layer schemes on the simulated PET. Using the RegCM4 regional climate model, four simulations were conducted (two for each case) in the period 1997 to 2017. In all simulations, the RegCM4 was configured with 25 km resolution and downscaled by the ERA-Interim reanalysis dataset. To en...sure a reliable estimation of the PET, a calibrated version of the Hargreaves-Samani equation was adopted. A high-resolution product of the ERA5 was used as the observational dataset. Results showed that the simulated PET is insensitive either to the dynamical downscaling or the boundary layer options. Concerning the annual climatological cycle, the RegCM4’s performance varies with month and location. Quantitatively, a root mean square error lies between 1 mm and 1.6 mm day-1, the Nash-Sutcliffe efficiency between 0.2 and 0.6, and the coefficient of determination between 0.5 and 0.75. Additionally, the Linear Scaling (LS) method showed its added value in the evaluation/validation periods. In conclusion, the RegCM4 can be used to develop a regional PET map of Egypt using the LS either in the present climate or under different future scenarios.Read more

The International Panel on Climate Change (IPCC) published a lengthy report on climate change in early 2023. This report hypothesizes five potential scenarios of greenhouse gas emissions from 2015 to the end of the century (2100) and estimates the global average temperature gain in the year 2100 from the mid-1800s for each scenario. The method of calculation in the IPCC report is obscure. The results are merely stated.The present paper provides a clear method for estimating the temperature gain each year from 2015 until 2100, along with yearly ...estimates of ppm of CO2. To facilitate the calculations, a set of scenarios of future emissions was chosen that is analogous to the scenarios used by the IPCC but is more amenable to computation.The basic assumption in this paper is that most of the temperature gain from the mid-1800s to 2015 (1.15 C – as reported by the IPCC) was due to rising CO2 concentration in the atmosphere and a relationship is thereby derived between warming and gigatons of CO2 emitted for the period: 1800s to 2015. If it is assumed that the amount of warming per gigaton CO2 from the past persists into the 21st century, then future warming in the 21st century can be estimated for any assumed future scenario of CO2 emissions.This paper provides a simple and clear estimate of yearly CO2 ppm and temperature rise from 2015 to 2100 since the 1800s for a set of scenarios that cover the likely range of future emissions.Read more

The proper geometry of belt splices influences their subsequent performance and durability during operation. Despite being such a critical aspect, evaluating the geometry of splices can be challenging, especially after their fabrication and vulcanization. This article presents an approach to diagnosing the geometry of belt splices based on the examination of belts using the DiagBelt+ magnetic system. Through the analysis of practical applications and the benefits derived from monitoring splice geometry, the article emphasizes the importance of ...diagnosing the geometry of belt splices to improve their quality and performance.Read more