The level of carbon dioxide in the planet's atmosphere since the Pliocene epoch (5.3 to 2.6 million years ago), when sea level was 25 meters higher than at present, never exceeded 0.04 per cent. Global climate change began to attract the attention of scientists only last half century, the political activity in this direction started even later — about 25 years ago.
People began to have a noticeable influence on the chemical composition of the atmosphere approximately seven thousand years ago. Since then and until the XVIII century the amount of carbon dioxide in the atmosphere has increased by 0,002-0,0025%, primarily due to slash-and-burn agriculture. Over the last five thousand years has slightly increased content in the atmosphere of methane, which, along with carbon dioxide, the main greenhouse gas.
All this until the last third of the XVIII century, when the level of carbon dioxide in the atmosphere was 0.028 percent, did not lead to an increase in global temperatures. But with the beginning of the industrial revolution the level of carbon dioxide in the planet's atmosphere began to rise sharply, and the situation has changed dramatically. Scientists claim that in the eighteenth century came the anthropocene — a new geological epoch in Earth's history, which has replaced the Holocene — the era marked by the disappearance of Pleistocene ecosystems, particularly the extinction of mammoths.
Over the past 200 years human activities have led to emissions of over 600 billion tons of carbon. The scale of the entire atmosphere that led to increased content of carbon dioxide of about 0.012% and raised average global temperature by one degree Celsius (1.5 degrees on the continents). These numbers may seem small, but this is not the case: the temperature changes by one degree Celsius is enough to trigger natural disasters, which may result in mass starvation.
Perhaps climatic optimum made about seven thousand years ago, contributed to the emergence of cities and the expansion of modern humans in Europe and Asia. Currently, the global annual average temperature on the planet would have to show long-term downward trend. Observations show that this does not happen because of human factor.
The first evidence of anthropogenic influence on the climate of the planet is a graph of the Keeling showing steady growth in the concentration of carbon dioxide in the atmosphere over the past half century. Simple estimates of greenhouse gas emissions produced during combustion of hydrocarbons, a man may call it is the cause of global warming. Over the past two centuries the trend is particularly noticeable in the average global temperatures for several, decades. With this approach, it becomes clear why climatologists troubled fifteen-year pause in global warming observed in 1998-2013 years, when almost did not grow, the average annual temperature. Experts have found an explanation. In their opinion, was heated not the surface of the oceans (to a depth of several hundred meters), and its thickness. Likely, similar processes occur every few decades and felt in the strength and duration of El niño.
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Even worse is the situation with volcanoes. When the eruptions together with the carbon dioxide gets into the stratosphere the sulfur dioxide which reflects sunlight and thereby cool the planet. In fact, volcanism is more conducive to cooling, not warming the planet, but only in the long term up to two years. In the atmosphere sulfur dioxide turns into sulfuric acid, which destroys ozone and creates acid rain, while carbon dioxide is not destroyed for hundreds of years.
As warming volcanic ash more difficult to reach the stratosphere, causing the sulphur dioxide will not be released beyond the troposphere — surface layer (up to 20 kilometers) of the gas envelope of the planet, and within a few days after the eruption, it will fall to the ground as acid rain. This is due to several reasons: a stratification of the troposphere (it is already observed in the tropics), increasing its thickness and, consequently, increase the lower boundary of the stratosphere.
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Empirical data and climate models confirm the reality of global warming. So, in 2016, a record temperature was recorded in Thailand (Mae Hong son, April 18, plus of 44.6 degrees Celsius) and India (Phalodi, may 19, plus 51 degrees). The worst situation in the middle East and North Africa: Kuwait (Marib, July 21, plus 54 degrees, the highest in Asia in the entire history of observations), Iraq (Basrah, July 22, at 53.9 degrees) and Russia (Sochi, July 22, plus 53 degrees). In Europe, the most unfavourable situation for Spain.
These observations are confirmed in computer simulations, according to which part of the Middle East and North Africa by 2050 will become uninhabitable, leading to mass migrations of the population from these territories (some of these phenomena have already been observed). By 2050 in these areas summer daytime temperatures will reach 46 degrees Celsius, the average summer night temperature is below 30 degrees (in the optimistic forecast). Extremely hot days are expected in the region of five times more than today (80 instead of 16). By the end of this century temperatures the hottest summer days can reach 50 degrees, and their number grow to 118-200 days (depending on the climate model).
In another study it is noted that in the period between 2071 and 2100 the years, the wet bulb temperature in some regions of the Persian Gulf, such as Qatar, UAE and Iran will reach 35 degrees Celsius. In the fall risk area, in particular, Dubai, Doha and Abu Dhabi. Today the average annual temperature in these and other locations close to critical values. The human body is able to adapt to changes when the wet bulb temperature not exceeding 35 degrees Celsius. This value defines the threshold of survivability of the human body. Most people stay at a higher temperature for several hours can lead to overheating and death.
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Cultural, social and economic consequences of global warming are obvious. Probably in the future will be impossible Hajj to Mecca — this cult for Muslims the object is visited annually by over two million people. Most of the time, the pilgrims are under the open sky. Because of the water shortage countries ' GDP could by 2050 be reduced by 14 percent. Scientists forecast just in that case, if the countries of the Middle East will not achieve higher levels of precipitation in the region, such as the creation of clouds or the construction of the mountain.
No less urgent problem of global warming to Black Africa. State located in the Sahara and below the belt of the Sahel, the lack of fresh water could lead to a 2050 GDP by 11 percent. It is possible that these global changes will lead to the fact that in these regions the winter is to recall the summer, which will come extremely adverse to human life season.
Current climate models take into account many parameters, interrelated and changing over time. The influence of volcanism, the pause in global warming, mammoth ecosystems — representative examples of interrelated phenomena. It is almost impossible to establish the exact dependence of one parameter from another, in connection with which scientists have neglected some connections or settings than others. This leads to assumptions that may work in one case but actually be an error in another.
In addition, some climate models are sensitive to changes in initial conditions: a small change in input parameters results after simulation (performed, usually on a supercomputer) to a fundamental change output parameters. From a mathematical point of view, this means that a climate model is a typical chaotic system. From a physical point of view, the description of the system in this way leads to the impossibility of reliable quantitative predictions, a phenomenon you can explore only on a qualitative level. In this approach, a scientist has no choice but to rely on observation and attempts to build linear, but limited in their applicability to climate models.
Fortunately, Russia is among the countries that will probably benefit from global warming. A large part of the population lives in the European part, where global warming should lead to a lengthening of the summer season and the shifting boundaries of arable lands to the North. Increase navigation on the Northern sea route. On the other hand, more than 60 percent of Russia is in permafrost zone — these areas will become more frequent floods, they may suffer from global warming.
No doubt the fact that the landscape of Siberia has changed dramatically: the soil will thaw, subside, and filled with water. Eventually, perhaps, the decisive role in these processes will shift from growth in average annual temperatures, increased rainfall. In the negative scenario, the huge territory of present-day permafrost may turn into a deep swamp. Degradation of these territories can be already observed.
Widely known for the Yamal crater is one of the examples of negative landforms due to global warming. There are more than ten such grooves diameter and depth of several tens of meters. This so-called funnel gas emissions resulting from the destruction of gas hydrates release contained in the upper layers of the permafrost gas.
However, not all by far. The permafrost in most areas of Siberia did not prodavala hundreds of thousands of years. Moreover, in Siberia for two million years has successfully existed Pleistocene ecosystem. On a relatively small area at a time could get on one mammoth, five buffaloes, six horses and ten deer. Such a high density of large animals suggests that tundra was mostly covered need for an active grazing herbs, not swamps.
It is unlikely that mammoths, bison, horses and deer were the inhabitants of the marshes, as it happens in climate modeling. This contradiction is one of the drawbacks inherent in climate simulations.
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