Global Warming: Causes and Impact

The phenomenon of rising average air temperatures close to the surface of the Earth over the previous one to two centuries is known as global warming. Since the middle of the 20th century, climate scientists have accumulated extensive data on a variety of weather events, including temperatures, precipitation, and storms, as well as on factors that have an impact on climate, such as ocean currents and the chemical makeup of the atmosphere. These findings show that Earth's climate has changed on practically every possible period from the beginning of geologic time and that human activities have increasingly affected the rate and scope of current climate change since the beginning of the Industrial Revolution.

Causes of Global Warming - 

Green House Effect

Several types of solar and terrestrial radiation are kept in balance to keep the Earth's average surface temperature constant. Since the frequencies of the radiation are extremely high and the wavelengths are relatively short—not far from the visible region of the electromagnetic spectrum—solar radiation is sometimes referred to as "shortwave" radiation. Terrestrial radiation, on the other hand, is sometimes referred to as "longwave" radiation due to the comparatively low frequencies and lengthy wavelengths—somewhere in the infrared region of the spectrum. Watts per square metre are commonly used to assess downward-moving solar energy. The "solar constant," or total solar radiation energy, is equal to around 1,366 watts per square metre per year at the top of the Earth's atmosphere. The average yearly surface insolation is 342 watts per square metre after accounting for the fact that only 50% of the planet's surface is exposed to solar radiation.

Just a small portion of the total solar energy that enters the atmosphere gets absorbed by the Earth's surface. Around 30 units of the incoming solar radiation for every 100 are reflected back to space by the atmosphere, the clouds, or reflecting areas of the Earth's surface. The geographical breadth and distribution of reflective structures, such as clouds and ice cover, can fluctuate, which means that Earth's global albedo need not remain constant throughout time.

The atmosphere, clouds, or surface may absorb the 70 solar energy units that are not reflected. The same 70 units must be radiated back into space by the Earth's surface and atmosphere in order to maintain thermodynamic equilibrium in the absence of further problems. According to the Stefan-Boltzmann equation, the amount of this emission of outgoing radiation is correlated with the temperature of the Earth's surface (and that of the lower layer of the atmosphere that is effectively in touch with the surface).

The greenhouse effect adds to the complexity of Earth's energy balance. The so-called greenhouse gases, namely carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), are trace gases with certain chemical characteristics that absorb part of the infrared light emitted by the Earth's surface. A portion of the initial 70 units do not immediately escape to space as a result of this absorption. The net effect of absorption by greenhouse gases is to increase the total amount of radiation emitted downward towards Earth's surface and lower atmosphere because greenhouse gases emit the same amount of radiation that they absorb and because this radiation is emitted equally in all directions (that is, as much downward as upward).

Earth's surface and lower atmosphere must produce more radiation than the initial 70 units in order to maintain equilibrium. Hence, a greater surface temperature is required. The ultimate result is comparable, even if this method is not quite the same as that which controls a real greenhouse. In comparison to what would be anticipated in the absence of greenhouse gases, the presence of greenhouse gases in the atmosphere causes a warming of the surface and lower portion of the atmosphere (and a cooling higher up in the atmosphere).

Green House Gases

Carbon Dioxide

Carbon dioxide (CO2) is the most significant of the greenhouse gases. Outgassing from volcanoes, the burning and organic matter's natural decomposition, and aerobic (oxygen-using) organisms' respiration are all examples of natural sources of atmospheric CO2. These sources are often counterbalanced by a collection of "sinks"—a collection of physical, chemical, or biological processes—that function to remove CO2 from the atmosphere.

Methane

The second-most significant greenhouse gas is methane (CH4). Since CH4 produces more radiative forcing per molecule than CO2, it is more powerful than CO2. In addition, more molecules may fill the space since the infrared window is less saturated in the range of wavelengths that CH4 absorbs light. Nevertheless, CH4 is present in the atmosphere at much lower quantities than CO2, and its volumetric values are often reported in parts per billion (ppb) rather than parts per million (ppm). Moreover, the residence duration of CH4 in the atmosphere is much less than that of CO2 (the residence time for CH4 is roughly 10 years, compared with hundreds of years for CO2).

Nitrous Oxide

Moreover, nitrous oxide (N2O) and fluorinated gases (halocarbons), which include sulphur hexafluoride, hydrofluorocarbons (HFCs), and perfluorocarbons, are trace gases created by industrial activities that have greenhouse-gas qualities (PFCs). Radiative forcing from nitrous oxide is 0.16 watts per square metre, whereas fluorinated gases as a group are responsible for 0.34 watts per square metre. Because of normal biological processes in soil and water, nitrous oxides have low background quantities, while fluorinated gases are mostly dependant on industrial sources.

Aerosols

An key anthropogenic radiative forcing of climate is the creation of aerosols. Aerosols collectively reflect and absorb some of the incoming solar energy, which results in a negative radiative forcing. When it comes to their relative relevance in influencing near-surface air temperatures, aerosols are only second to greenhouse gases. Aerosols are easily flushed out of the atmosphere within days, either by rain or snow (wet deposition) or by settling out of the air, in contrast to the decade-long residence durations of the "well-mixed" greenhouse gases, such as CO2 and CH4 (dry deposition). Thus, they must be continuously produced in order to have a consistent impact on radiative forcing. Aerosols can have a direct impact on climate by absorbing or reflecting solar energy, but they can also have an indirect impact by altering cloud formation or cloud characteristics. Darker-colored aerosols may prevent the formation of clouds by absorbing sunlight and warming the surrounding air, in contrast to the majority of aerosols that act as condensation nuclei (surfaces onto which water vapour may condense to create clouds). Winds and upper-level atmospheric circulation can carry aerosols thousands of kilometres from their places of origin.

Effects of Global Warming

The actions that civilization takes, particularly the release of greenhouse gases from the combustion of fossil fuels, will determine the route of future climate change. Since the Fifth Assessment Report (AR5) was released in 2014, the IPCC has put out a variety of alternate emission scenarios to explore potential future climate changes. Many assumptions about projected rates of population increase, economic expansion, energy demand, technology improvement, climate mitigation, and other aspects are used to create the scenarios.

Ice Melt and Sea Level Rise 

The repercussions of a rising climate extend to various facets of the global ecosystem. The world's seas will probably continue to warm for several millennia as a result of the increases in greenhouse gas concentrations that have already occurred due to the sluggish process of heat diffusion in water. By 2100, it is anticipated that the thermal expansion of saltwater brought on by this warming plus the melting of mountain glaciers would result in an increase in the global sea level of 0.28 to 1.01 metres (11-39.8 inches). The real rise in sea level, however, might be far more than this. It seems likely that Greenland's ice sheet will melt faster as a result of the country's ongoing warming. Moreover, the West Antarctica ice sheet may melt as a result of this amount of surface warming. According to paleoclimatic data, a further 2 °C (3.6 °F) of warming might result in the final melting of the Greenland Ice Sheet, which would raise sea levels by an additional 5 to 6 metres (16 to 20 feet). Several islands and lowland areas would be submerged by such an increase. Large portions of the U.S. Gulf Coast and Eastern Seaboard, including roughly the lower third of Florida, the majority of the Netherlands and Belgium (two of the European Low Countries), and densely populated tropical areas like Bangladesh are among the coastal lowland regions that are vulnerable to sea level rise. Furthermore, a lot of the world's biggest cities, like Tokyo, New York, Bombay, Shanghai, and Dhaka, are situated on lowland areas that are vulnerable to sea level rise. Further sea level rise due to the melting of the West Antarctic ice sheet would be close to 10.5 metres (34 feet).

Change in Ocean Circulation

A decline in the "thermohaline circulation," sometimes referred to as the "great ocean conveyor belt," is another potential effect of global warming. In this system, cold, salty waters sink in the subpolar portions of the seas, which aids in pushing warmer surface waters from the subtropics poleward. This mechanism causes a warming impact to be transported to Iceland and the coastal areas of Europe, which modifies the climate in those areas.

Impact on Tropical Cyclone

The effect of global warming on tropical cyclone activity is one of the more contentious issues in the study of climate change. It looks probable that increasing tropical ocean temperatures brought on by global warming will enhance tropical storm strength and its related potential for destruction. Rising ocean temperatures and an increase in storm strength have been found to be closely related in the Atlantic. Because to a lack of trustworthy long-term observations, trends in the intensity of tropical cyclones in other locations, such as the tropical Pacific and Indian seas, are less definite. While increasing tropical storm intensities are favoured by warming waters, it is unknown how much warming temperatures influence the frequency of tropical cyclones. Additional elements, including wind shear, could be important. Warmer temperatures may be somewhat offset if climate change causes more wind shear, which inhibits the development of tropical cyclones in places where such storms often originate. The uncertainty around how ENSO will be impacted by climate change, for instance, makes changes in atmospheric winds themselves unpredictable.

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