Climate change

Article

December 7, 2021

A climate change is defined [1] [2] as the variation in the state of the terrestrial climate system, consisting of the atmosphere, hydrosphere, cryosphere, lithosphere and biosphere, which lasts for sufficiently long periods of time ( decades or longer) [2] until a new equilibrium is reached. It can affect both the meteorological average values ​​and their variability and extremes. Climate changes have existed since the beginning of Earth's history, they have been gradual or abrupt and have been due to various causes, such as those related to changes in orbital parameters, variations in solar radiation, continental drift, periods intense volcanism, biotic processes or meteorite impacts. Current climate change is anthropogenic and is mainly related to the intensification of the greenhouse effect due to industrial emissions from the burning of fossil fuels. [3] [4] Scientists actively work to understand past and future climate through theoretical modeling and observations. To do this, they compile a climatic record of the remote past of the Earth based on geological evidence from geotechnical surveys of thermal profiles, ice cores, records of flora and fauna such as growth of tree rings and corals, glacial and periglacial processes. , isotopic analysis and other analyzes of sediment layers and records of past sea levels. Any long-term variation observed from these indicators (proxies) may indicate climate change. The instrumental record provides the most recent data. Good examples are instrumental recordings of atmospheric temperature and measurements of atmospheric CO2 concentration. We must not forget the enormous flow of climatological data coming from the orbiting satellites belonging mainly to the Earth observation programs of NASA [5] and ESA [6] General circulation models are often used in theoretical approaches to attempt to reconstruct past climates, [7] make future projections [8] [9] and associate the causes and effects of climate change. [10] The external factors that can influence the climate are called climatic forcings. [1] [2] Climatic forcings are factors that affect the energy balance of the climate system, modifying the amount of energy that the system receives from the Sun or the amount of energy that the system loses by emission from Earth to outer space. Climatologists who study current climate change often call them radiative forcings and consider basically four of them: the amount of solar radiation high in the atmosphere (solar constant), the terrestrial albedo, the concentration of greenhouse gases and the concentration of aerosols both of natural origin, such as those from volcanic eruptions, and those of anthropogenic origin that come from human activities, among others. Paleoclimatologists, however, consider as external climatic forcings a much broader range of extraterrestrial phenomenology that includes variations in the Earth's orbital parameters or falling meteorites. [12] Orbital variations, for example, change the distribution geographical and seasonal solar radiation but they hardly modify the planetary energy balance, that is, they do not constitute a relevant radiative forcing. Indeed, one of the objectives of climatologists and paleoclimatologists is to understand what amplifying mechanisms induce these orbital variations to explain the different glacial cycles that have occurred in the history of our planet. [13] Regarding the internal processes, from the climatological point of view the var

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