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Climate change and meteorological fluctuations
2022-07-24
Written by: Eng. Dr. Rasoul Mujbil Khalaf
Department of Water Resources Engineering - College of Engineering - Mustansiriya University
Climate is a term usually given to the average state of the atmospheric system in a place over a long period of time estimated at several decades, usually defined by about 30 years, and not less than five years. The climate status is an average for weather conditions or i.e. their consequences. Taking into account the extreme and anomalies that may occur randomly every few years due to dynamic changes that occur in the atmosphere
The difference between weather and climate is clear; however, many people and the media confuse between them and use them interchangeably in place of each other. In order to make the difference between them clear and simple, we mention the following saying: “If you do not like the weather in the place where you are going or where you are, wait for several hours or days, the weather may change, but if you do not like the climate where you live and do not suit it, All you have to do is leave."
This simply states that weather conditions are temporary, instantaneous states of the atmosphere, showing what is happening in a place of limited space during a certain time, and may change from hour to hour, from day to day, from month to month, and from season to season. While, on the other hand, climatic conditions are a feature of the place in which they occur, they are fixed and established that dominate over large areas and regions, It is expected to occur and always recur in every month, season and year during successive years based on statistical expectations and calculated rates for tens of years, especially the average of the 30-year period that is known as average climate Climatic Normal
In the absence of a sufficient period of time, as is the case in new weather stations, a period of no less than five years can be relied upon as a primary indicator of the nature of the climate. Based on the foregoing, climate states must be dealt with as comprehensive states of the atmosphere that take place on a broad scale in time and space, while weather states represent detailed states of atmospheric states that take place on a small scale in time and space during climatic conditions..
Climate is usually classified into three main categories, namely: the measured climate elements such as atmospheric temperature, atmospheric pressure, and the volume or density of the atmosphere, in addition to what follows or branches from other elements. As for the derived climate elements, they are not directly measured, but are derived or calculated by mathematical climatic equations using the measured weather and climate elements. Derived elements are usually used in applied weather and climate studies and research, and there are several of them, including evapotranspiration, It is an indication of the intensity of latent atmospheric evaporation, and is used to indicate the amounts of water requirements for crops and plants under certain weather and climate conditions. Although there are devices to measure it directly, but it is very expensive and is not available except in some scientific research institutions, and therefore it is calculated from climatic mathematical equations using measurements of weather and climate elements such as insolation, temperature, relative humidity, wind speed and other elements. Including Aridity Indices Which are usually used in climatic classification to determine the dry regions from other climatic regions. The third type of climate element is Alternate weather and climate elements Proxy Elements as they are neither measured nor derived elements, but alternative evidence on behalf of the measured elements, inferred from the climatic conditions that prevailed in the ancient past hundreds and thousands of years ago, through the various human and environmental activities that were taking place, and therefore it can be called indicative elements. Evidence Elements are the alternative elements are the archaeological monuments, including the remains of palaces, buildings and temples, and the inscriptions and drawings on the walls - drawings, writings, ancient poems, pottery, historical figures and fossils (geological fossils). consisting of the fossilized remains of plant and animal organisms preserved through layers of rocks, or their remains preserved through the polar ice layers and the silt of major lakes and rivers, and by changing the levels of seas, rivers and lakes.
There are several factors directly and indirectly affect weather and climate conditions. Among these factors, their impact is on a small, local and temporary scale that affects weather conditions and called as weather rates. Weather Modifications or weather controls Weather Controls some of them have an impact on a vast or global scale and permanently affect and control climate conditions, and they are known as Climate Factors or climate controls. One of them is the incoming solar radiation which arrives to the Earth's surface and is greatly affected by the tilt of the Earth's axis with the level of its orbit around the Sun is at an angle of between′27°23and the′45°23 Where the sun’s rays fall vertically or semi-vertically, the greatest amount of solar radiation reaches it, while it reaches the higher and polar widths, where the solar rays always fall tilted, the least amount of radiation is estimated, and it is estimated that the higher and polar widths reach less than 20% of what reaches to tropical and tropical widths. Because of this variation in the amount of insolation reaching the surface of the Earth, the atmospheric pressure values ??vary, and global and regional winds are generated raging across geographical widths, and from one place to another on the surface of the Earth, and water currents are generated across the seas and oceans. As the nature of surfaces and their colors play an important role in determining the amounts of net insolation reaching the Earth's surface and its variation from one place to another. White and light-colored surfaces, such as snow, white sand, and white limestone, have a high albedo and therefore absorb little insolation. Whereas the albedo has black and darker surfaces such as basalt rocks and a few permanent forests, absorbing more amounts of insolation. That Proximity to water bodies, continental surfaces which is meant the location in the heart of the continents away from the bodies of water, is one of the factors affecting the climate. The more continental the location, the less the effects of the seas and oceans on its climate are, or perhaps non-existent, as the characteristics of the winds and air currents blowing from above it to the land gradually adjust with the increasing distance from it. They completely lose their basic properties and become similar to the local air in the sites they reach. Mountain heights and bare lands play a major role in influencing the climate for the same reasons mentioned above.
But it seems that all the factors and reasons mentioned, are outside the ability and control of man to make a change in them, except for the factor of air pollution in major cities. It is known that there are gases in the atmosphere, such as water vapor H2O and carbon dioxide CO2 and methane CH4 and nitrous oxide N2O and chlorofluorocarbons CFCS or chlorofluoromethane CFMS. In addition to particles Aerosols and fine dust particles absorb some of the earth's rays to return and radiate to the surface of the earth, increasing its temperature. These gases and compounds are known as Greenhouse gases or earth warming gases. When their amounts in the atmosphere increase due to extra normal levels human activities, as is the case in the air of cities, their heating effect increases on the surface of the earth, leading to what is known as global warming or Heat trapping. Therefore, the characteristics of the thermal, humid and precipitation climate in cities are modified and appear relatively different from the regions around them, forming the so-called Heat islands.
Many climate scientists believe that global warming will go beyond the boundaries of cities and will be general and comprehensive for the entire Earth's climate and will lead to a temperature rise of a few degrees Celsius in the near future, causing permanent regional and global climatic changes represented by changes in thermal and precipitation patterns, causing the so-called “Climate fluctuation” or “climate change”.
Climate fluctuation is defined as: Decrease or rise in the values ??of the elements of climatic conditions from their average during time periods of several consecutive years, which may take about a decade (ten years) or more, ends with the return of the climate to its normal state. Accordingly, the cases of climate fluctuations can be divided into two cases, one of which is positive climate fluctuations with values ??higher than the average, and the other is negative climate fluctuations during which the values ??of the elements and climatic conditions are below the average.
An example of these fluctuations is the case of the aridity that occurred in the Sudanese African Plane region during the sixties, seventies and eighties of the last century (the twentieth century), which led to the desertification of the pastoral agricultural lands, but it stopped in the late eighties and some lands were able to restore their productivity again. Examples of them are also the recurrence of storms the destructive storm hurricanes in the Atlantic Ocean during a return period of several decades, the climatic data showed that the Hurricane storms were very frequent 1944-1967 and then decreased during the period 1968-1991 and returned more frequent and active for the period 1995-2000. One of the good examples of these climatic fluctuations Also, the flow of the Colorado River in America, during a period of 20 years, i.e. between 1900-1920, the discharge of the river was huge, but it decreased sharply during the next forty years, between 1920-1960.
The causes of climatic variation and fluctuation occur from internal processes taking place among the components of the globe system that affect and are affected by them, and cause extremisms and anomalies that occur on a wide scale in the general air movement between one year and another or several consecutive years successively, these anomalies disrupt or accelerate thermal transport and humidity through geographical presentations, leading to global climate variations and fluctuations.
Many studies attribute the occurrence of anomalies in the general wind cycle to changes in the composition of the atmosphere, atmospheric pollution and the increase in its load of dust and particles resulting from natural and human activities, or due to desertification, which leads to a change in the nature of the land’s surface due to exhausting agricultural activities, grazing, and unjust wooding, and the increase in urban areas. Nevertheless, contemporary climatologists and meteorologists see climate fluctuations as nothing more than normal variations that occur during climatic conditions and fall within the normal statistical climate predictions.
As for “climate change”, it is known that well-established change in the Earth's climate system taking place on long-term scales, occurring over centuries or even thousands of years, occurred in the past but is likely to occur in the future. An example of these climatic changes is the successive ice ages during the period between 10,000-75,000 before now, which were occurring during periods of time each lasting about 60,000– 100,000 years (interspersed with warm periods, interglacial periods, each of which lasted about 1,400 years).
Some studies have indicated that the Earth's climate during the past two thousand years or more has remained stable and unchanged. However, some researchers expect a sudden climate change within the next several decades, and some of them confirm that the Earth is currently entering the beginnings of a climate transition. Climate change is caused by external factors and processes that affect the Earth system and are not affected by it. These processes are represented by slow continuous astronomical changes in the Earth's orbit around itself and around the Sun. It is believed according to the Milankovitch theory or mechanism proposed by the scientist Milutin Milankovitch In 1138 AD, there are three regular astronomical cycles that run in sync with each other constantly, and because of them the following takes place:
1- Changing the angle of inclination of the Earth's axis from the vertical position (Obliquity from) 22.1° – 24.5° during a period estimated at about 40,000 years, i.e. 47” every 100 years, and it is currently equal to between 23.27° to 23.45° as shown in Figure (1).
Figure (1) Changing the angle of inclination of the Earth's axis Obliquity from 23.1 to 24.5 degrees over a period of 40,000 years. Source: eoearth.org,
2- The equinox or the advance of the Earth's orbit is 365 degrees due to the rotation of the earth's conical axes (Precession) a complete cycle during 21,000 to 27,000 years, during which it changes its direction, shown in Figure (2).
Figure (2) the change in the angle of tilt and reflection of the Earth's axis during a period of 21,000 years to 27,000 years.
Because of this, the time of the seasons gradually changes, the time of the spring and autumn equinox’s advances, and the position of the Perihelion changes as well as Aphelion site in the Earth's orbit around the sun. Calculations indicate that the time of the seasons is delayed by one day every 70 years, and it is believed that with the passage of time the direction of the Earth's axis will shift from the Polar Star to the Vega star Vega, and the time of perihelion moves from January 5 to July 5 during about 10,500 or 13,500 years, and thus summer will fall in the northern hemisphere in December and winter in June. There is no doubt that such astronomical changes have the potential to cause long-term, long-term climate changes lasting several thousand years.
Some recent studies believe that global warming is due to the increase in human activity, no increase every from carbon dioxide CO2 and methane CH4 and nitrous oxide N2O and chlorofluorocarbons CFCS or chlorofluoromethane CFMS, fine dust particles and particles (Aerosols) in the atmosphere, it will contribute to an increase in the temperature of the atmosphere between 1.5° to 5.8° and a sea level rise between 0.09 m to 0.88 m by the year 2100 AD, leading to the beginning of a profound climate change, (Deep climate change) of no going back. However, this matter remains in doubt and a great controversy among scientists, especially since many of them believe that the Earth’s surface is on the way of a severe drop in temperature, and it is appropriate to include the effects of air pollution within the climatic variations and fluctuations on a very small scale. Some studies show that urbanization has invaded agricultural and forest lands and established major cities in their place as a form of climate change due to the change in the nature of the earth's surface and thus the change in the thermal and moisture balance in urban sites.
It is clear that there is a clear difference between climate change and climate fluctuation and it is really interesting that many people, the media, and even some specialists in other fields related to climate, confuse the concept of climate change with the concept of climate fluctuation (variability). We must realize that when talking about climate change, what is meant is a total change in the climate system that occurred in the distant past during vast time scales, nearly tens of centuries or several thousand years, and it takes such a time to occur again, and that is why some call this change as the deep climate change. Thus, it is impossible for human generations to witness during their short life any climate change, but its occurrence is inferred by alternative climate elements such as (fossils) preserved in sedimentary rock layers that formed through ancient geological ages, in silt deposits in lakes, and tree growth rings, and through the study of the ice layers accumulated in the polar regions and their preservation of animal and organic remains, and what archaeological excavations reveal in the sites and caves inhabited by prehistoric humans in the age It is certainty believed, as it was shown above, that its occurrence is related to astronomical changes affecting the axis of the Earth's orbit around itself and its orbit around the sun. On the other hand, climate variability occurs repeatedly during short periods of time, approximately tens of years, during the life of any human generation, and thus a person can witness during his life several climatic fluctuations. It is believed with certainty that its occurrence is related to anomalies or extremes affecting the general atmospheric cycle (wind cycle), and the locations of atmospheric work centers from high atmospheric pressures, and stress low air.
