Increasing the temperature of the Earth’s surface caused by increasing concentrations of greenhouse gases in the atmosphere. Although carbon dioxide (CO2) is only the fourth most abundant gas in the atmosphere, it is essential to maintain the temperature of the Earth’s surface. With water vapor, CO2 absorbs the infrared radiation (long wave) emitted by the Earth and returns this energy to the surface of the Earth, keeping our planet much warmer [average surface temperature of 15 ° C (59 ° F)] that it would not be otherwise. This capture of incoming solar radiation is called the greenhouse effect.
The Greenhouse Effect:
The greenhouse effect occurs when short wave solar radiation (which is not hindered by greenhouse gases) heats the Earth’s surface and energy radiates through the atmosphere as heat from the Earth’s atmosphere. The longest wave In the wavelengths of 5-30 μm, much of this heat radiation is absorbed by water vapor and carbon dioxide, which radiate in turn , so as to heat the atmosphere and the land and sea surface. It is natural and what keeps the land habitable. Without the greenhouse effect, nighttime temperatures would collapse and the average surface temperature would be about minus 18 ° C, about the same as the moon, which is missing the mantle of our atmosphere. If the difference of about 33 ° C substantially the natural levels of water vapor (60% or more, including clouds) and carbon dioxide in the atmosphere of the earth. With regard to the greenhouse improvement or probability AGW, the particular problem is centered on the 8-18 micron band, where water vapor is a weak radiation absorber and where the heat radiation from the earth is bigger. Increasing concentrations of CO2 and other radioactive gases mean less heat is being lost in the space of the Earth’s lower atmosphere and, as a result, are likely to increase the temperature on the surface of the Earth. Atmosphere and oceans are at the center of attention.
Global Warming and Climate Change
There is clear evidence of changes in the composition of greenhouse gases in the lower atmosphere, and CO2, in particular, is steadily increasing to its current level of about 400 ppm. In May 2013, the average daily concentration of carbon dioxide in the Mauna Loa atmosphere in Hawaii, the world’s first reference site, exceeded 400 ppm for the first time since measurement began in 1958. It increased in the last 200 years and a half in the last 30 years. In 2016, it increased by 3.3 ppm (0.8%), the largest annual increase so far. Ice core samples show that levels of carbon dioxide and methane are higher than in the last 650,000 years. CO2 has 170-270 ppm.
The February 2014 joint report of the Royal Society of the United Kingdom and the National Academy of Sciences of EE. UU It presents a large amount of information, including that of the IPCC Fifth Assessment Report, as indicated above. said too. “The results of the best climate models available do not predict the abrupt changes in these systems (often referred to as turning points) in the near future, however, as increasing global warming cannot rule out the possibility of a sudden change, However, “the climate system involves many competitive processes that could change the climate to a different state once the threshold is exceeded.” A well-known example is the south-north oceanic thermohaline circulation, which is maintained by water cold salt plunge into the North Atlantic and involves additional heat transport in the North Atlantic via the Gulf Stream. In the last ice age, impulses from the freshwater ice cover in North America resulted in the slowdown in this volatile circulation and the widespread climate change throughout the Northern Hemisphere. the cooling of the North Atlantic due to the melting of the Greenland icecap is much less intense and, therefore, should not cause abrupt changes. As another example, the warming of the Arctic could destabilize methane (a greenhouse gas) trapped in ocean sediments and permafrost, which could lead to a rapid release of a large amount of methane. If such rapid rejection occurs, significant and rapid climate change will occur.
These high-risk changes are considered improbable in this century, but by definition, they are difficult to predict.