During 2015, atmospheric carbon dioxide levels rose significantly faster than at any time in 55 million years. During the year, from March 2016 to March of this year, in the area of the Mauna Loa weather observatory, the level of carbon dioxide increased by 0.000235 percent, amounting to 0.040718 percent. As experts note, in reality the situation is much worse, since in April 2016 the level of carbon dioxide in the atmosphere reached 0.040742 percent, and at this point in time this figure may be surpassed. It is likely that this year the situation may worsen even further. Scientists are currently trying to understand the causes and possible consequences of global warming.
In the Earth's atmosphere, the level of carbon dioxide since the Pliocene period (about 5.3-2.6 million years ago) has never exceeded 0.04 percent. At that time, the sea level was 25 meters higher than it is now. Global warming began to attract close attention of scientists only in the last fifty years, and political activity in this direction began much later - about a quarter of a century ago.
Man began to have a tangible effect on the chemical composition of the atmosphere about seven thousand years ago. From this time until about the 18th century, the level of carbon dioxide in the earth's atmosphere increased by 0.002-0.0025 percent. Slash-and-burn agriculture played a major role in this. In addition to carbon dioxide, methane, which is also a greenhouse gas, has slightly increased in the atmosphere over the past five thousand years.
Almost until the end of the 18th century, it did not provoke an increase in global temperature. During this period, the level of carbon dioxide in the atmosphere was only 0.028 percent. However, when the industrial revolution began, along with it began a rapid increase in the level of carbon dioxide in the atmosphere. The situation began to change dramatically. According to scientists, the Holocene in the 18th century was replaced by the Anthropocene era, which was marked by the disappearance of the Pleistocene ecosystem, in particular, by the extinction of mammoths.
Human activities over the past two hundred years have resulted in the release of over 600 billion tons of carbon into the atmosphere. This provoked an increase in the level of carbon dioxide in the atmosphere by about 0.012 percent, and also led to an increase in the average global air temperature by about 1-1.5 degrees. Despite the fact that these indicators may seem insignificant to people far from science, in fact, this is not at all the case, since an increase in temperature indicators by one degree can be enough to cause all sorts of natural disasters that can ultimately lead to mass starvation.
Scientists say that it was precisely those climatic conditions that formed about seven thousand years ago that contributed to the formation of cities, and also expanded the habitat of modern humans in Asia and Europe. At this point, global average temperatures should show declining trends. However, observations indicate that nothing like this is happening - due to the influence of the anthropogenic factor.
The first proof that the anthropogenic factor has an impact on the planet's climate is Killing's graph, which shows that the concentration of carbon dioxide in the atmosphere has steadily increased over the past 50 years. Simple estimates of human greenhouse gas emissions from burning carbon make it possible to identify it as the main culprit in global warming. Over the past 200 years, the warming trend has been especially noticeable when the introduction of average global temperatures is not one, but several decades at once. This approach makes it possible to understand why climatologists are worried about the fifteen-year hiatus that was outlined in global warming in 1998-2013, when the average annual temperature was hardly rising. Scientists have tried to find an explanation for this. So, in particular,they assume that during this time interval there was heating not of the surface of the World Ocean, but of its thickness. It is quite possible that similar processes repeat every few decades and remind of themselves in the duration and strength of El Niño.
The situation with volcanoes is much more serious. During the eruption, sulfur dioxide also enters the stratosphere along with carbon dioxide, reflecting sunlight, thereby cooling the planet. Thus, volcanism no longer contributes to the heating of the planet, but to its cooling, but only for a few years. Sulfur dioxide in the atmosphere converts to sulfuric acid, which depletes the ozone layer and contributes to the formation of acid rain. At the same time, carbon dioxide has not been destroyed for hundreds of years.
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As the air temperature rises, volcanic ash reaches the stratosphere with greater difficulty, so sulfur dioxide will not be able to leave the near-surface layer of the Earth's gas shell - the troposphere, and within a few days after the eruption it will fall out in the form of acid rain on the ground. This process is influenced by several reasons: stratification of the troposphere, an increase in its thickness and an increase in the lower boundary of the stratosphere.
The reality of global warming is supported by climate models and empirical data. In particular, record high temperature indicators were noted in 2016 in Thailand (April 18 +44.6 degrees), India (May 19, +51 degrees). The most serious situation is developing in North Africa and the Middle East: in Iraq (July 22, +53.9 degrees), Kuwait (July 21, + 54 degrees), Iran (July 22, +53 degrees). If we talk about the territory of Europe, then the most unfavorable conditions are in Spain.
These observations are confirmed by computer modeling, according to which part of North Africa and the Middle East will become completely unsuitable for human life by 2050, which will provoke mass migrations from these territories of the population. It must be said that partly migration phenomena are already being observed at the moment. In these territories, until 2050, daytime temperature indicators in summer will increase to +46 degrees Celsius, at night the average temperature will not drop below +30 degrees. And this is the most optimistic forecast. It is expected that in the region there will be five times more abnormally hot days than at present, that is, instead of 16 - 80. By the end of the century, temperature indicators on the hottest summer days can rise to plus 50 degrees, and the number of such hot days,depending on the climate model, it will reach 118-200 per year.
Another scientific study suggests that the temperature of the wet bulb in the period from 2071 to 2100 in certain regions of the Persian Gulf, in particular in Iran, the UAE and Qatar, will reach plus 35 degrees. Doha, Dubai, Abu Dhabi are at risk. At present, the average annual temperatures are approaching critical values here. The human body can adapt to temperature extremes of a wet thermometer, not exceeding 35 degrees. This level determines the threshold of the vitality of the human body. In the event that a person spends several hours in higher temperatures, in most cases this leads to overheating and death.
Global warming has clear social, cultural and economic implications. It is possible that the Hajj to Mecca - a place of worship for Muslims - will become impossible in the future. Now it is visited by over two million people a year. Pilgrims spend most of their time in the open air. By 2050, GDP in the Middle East will shrink by 14 percent due to water shortages. However, it should be said that such a forecast of scientists will be true if the countries of the region fail to increase the level of precipitation, in particular, by building a mountain or creating clouds.
The problem of global warming is very acute for the African continent. Countries below the Sahel and in the Sahara can expect an 11 percent drop in GDP as a result of a shortage of fresh water. Scientists do not exclude that such global changes will entail climate changes, as a result of which winter will resemble summer, which will be replaced by a season that is extremely unfavorable for humans.
In modern climate models, a large number of parameters are taken into account, which are interconnected and change over time. Pauses in global warming, volcanism, and mammoth ecosystems are typical examples of interconnected phenomena. It is practically impossible to establish the type of dependence of one parameter on others; for this reason, scientists are forced to neglect individual relationships and parameters. As a result, assumptions arise that will work in one case and will be wrong in the other.
In addition, some computer climate models are very sensitive to changes in the initial parameters: with a small change in the input parameters, a fundamental change in the output parameters occurs after a simulation performed on a supercomputer. Mathematically, this means that the climate model is a typical chaotic system. From the point of view of physics, a description of a system in this way ultimately leads to the fact that it is impossible to make reliable quantitative predictions, and the phenomenon can only be investigated at a qualitative level. Specialists with this approach have no choice but to rely on attempts to build limited in applicability climate models and observations.
Russia is among those countries that are likely to benefit from global warming. The majority of the population lives in the European part, and there global warming may lead to a shift in the boundaries of land suitable for agriculture to the north and a lengthening of the summer period. In addition, navigation on the Northern Sea Route may increase. At the same time, approximately 60 percent of Russia's territory is located in the permafrost zone - floods may become more frequent here, as a result of which these territories will be severely affected by global warming.
Global warming will undoubtedly lead to a radical change in Siberian landscapes, the soil will thaw, fill with water and sag. It is quite possible that over time, the leading role in these processes will shift from an increase in average annual temperature indicators to an increase in precipitation. If the situation develops negatively, vast territories currently covered by permafrost will turn into deep swamps. Some degradation of these territories is already being observed.
The well-known Yamal sinkholes are one of the striking examples of negative landforms caused by global warming. Currently, there are already more than a dozen such depressions, the depth and diameter of which reaches several tens of meters. These are gas funnels that result from the release of gas contained in the upper layers of the permafrost.
However, everything is rather ambiguous. In most Siberian territories, permafrost has not thawed for hundreds of thousands of years. In addition, the Pleistocene ecosystem existed on the territory of Siberia for two million years. In a relatively small area, five bison, one mammoth, ten deer and six horses could live simultaneously. Such a high density of large animals may indicate that the tundra-steppe was mostly covered with grasses necessary for active grazing, but not swamps.
Scientists question whether bison, mammoths, deer, and horses were swamp dwellers, as evidenced by climate computer simulations. This contradiction is one of the shortcomings that characterize climate simulations.
