Ecology: biology of interaction. VI-12. Global climate change

VI-12. Global Climate Change
One of the most striking environmental changes of recent times has been global warming — the gradual increase in the average annual temperature of Earth's atmosphere and hydrosphere. Surprisingly, until recently the very fact of global warming sparked heated debates. Unfortunately, the debate over the direction of climate change now appears to have ended: it is getting warmer.
Warming of the World Ocean by 0.1°C per year has been recorded, along with glacier retreat and sea level rise of 0.7–3 mm per year. In summer 2003, according to WHO data, 20,000 people in Europe died from the heat, and 30% of the harvest perished on the southern continent. The UN forecasts that as a result of global warming over the coming decades, approximately one-third of a billion people will become environmental refugees and nearly 2 billion planet inhabitants will be deprived of access to fresh water.
"How the modern world addresses climate change will directly determine the development prospects for a significant portion of humanity. ... Failure to solve this problem condemns 40% of the poorest population of our planet — approximately 2.6 billion people — to a future with progressively diminishing opportunities" (UN Development Programme Report, 2007).
The planet's average temperature has increased by at least 1°C since the beginning of the 19th century. Temperatures are rising fastest on the Antarctic coast: in some places by 2.5°C over the past sixty years. This leads to accelerated glacial sliding into the ocean and further melting. Another consequence of global warming is an increase in the number of destructive hurricanes, droughts, and floods due to changes in atmospheric circulation. By the way, the rise in Earth's average temperature does not mean it is becoming warmer everywhere: changes in atmospheric and hydrospheric circulation can cause local cooling.
New data on observed warming are presented in Figs. VI-12.1 and VI-12.2 (source).

Fig. VI-12.1. In 2015, it was the warmest year in the entire history of systematic observations. 2016 broke this record. Shown here is the average surface temperature of Earth (left scale) and its change relative to the level characteristic of the beginning of the industrial era

Fig. VI-12.2. Change in average temperature in 2016 across different regions of Earth's surface relative to the average temperature recorded for the thirty-year period from 1981 to 2010
Thus, the fact of warming has been recorded. One might think its causes should be clear. The UN Intergovernmental Panel on Climate Change presented a report in 2007 in which it concluded that with 90% probability, the main cause of global warming is human activity, particularly greenhouse gas emissions (carbon dioxide and methane). However, some scientists (especially characteristic of scientists and propagandists of the Russian Federation) dispute this conclusion, considering human activity to be a secondary factor in climate change.
What is there to argue about? One should build a model of climate change, reflect all known relationships in it, and make a scientifically grounded forecast. Unfortunately, Earth's atmosphere is so complex that constructing a detailed model of it is impossible. A small change in initial parameters can lead to cardinal changes in the expected future of the climate system. And we still do not know all the cause-and-effect relationships that affect the climate. Here are just a few points.
— Obviously, solar activity has been increasing in recent years, leading to Earth's warming.
— Rising carbon dioxide concentration stimulates photosynthesis and increases planetary productivity.
— Warming leads to increased water evaporation, growth of cloud cover, and reflection of more sunlight from clouds — that is, to self-cooling.
— Sea level rise will flood the most fertile land areas and reduce carbon dioxide sequestration.
— Acid rain stimulates the activity of sulfur bacteria, which suppress methane bacteria — producers of another greenhouse gas.
— In response to excessive ultraviolet radiation, phytoplankton releases substances that promote cloud formation.
— Human activity leads not only to CO2 emissions but also to atmospheric pollution by dust and soot. Global "darkening" could cause cooling.
And finally, some specialists convincingly insist that increasing carbon dioxide concentration cools, rather than heats, the planet! Heating of the lower atmospheric layers can intensify its vertical circulation and energy dissipation into space. Proponents of this point of view argue that the results of Antarctic drilling show that in Earth's recent history, carbon dioxide concentration increase was a consequence, not a cause, of warming.
Thus, the global community is trying to combat global warming without certainty about its cause. As the main accepted version, that warming is caused by emissions of carbon dioxide and methane into the atmosphere, which enhance the greenhouse effect. As the main countermeasure, it has been decided to use CO2 emission reduction. Is this the right decision?
It is difficult to say. Obviously, reducing fossil fuel consumption — which is a necessary condition for emission reduction — is a beneficial change, regardless of whether it is related to global warming or not. Besides, something must be done!
As noted earlier, the biosphere is characterized by a positive ecological balance throughout almost the entire history of its existence. Thanks to this, living organisms not only accumulated reserves of fossil fuels, on which modern humanity exists, but also simply created their own environment. Photosynthesis prevails over respiration, and it is no coincidence that oxygen in the atmosphere is about 21% and carbon dioxide about 0.038%.
But humanity is increasingly shifting the balance toward carbon dioxide, since at the beginning of the 20th century its concentration was only 0.029%. We use organic matter not only for the needs of our bodies but also "feed" our machinery with fossil organic matter. Combustion is similar to respiration, but proceeds faster and is accompanied by dissipation of released energy. We lack organic matter produced by autotrophs in real time, and we use reserves from other epochs — fossil fuels. As a result, we emit CO2 and shift the global ecological balance. But burning fossil fuels is not everything. Our method of agriculture leads to rapid soil degradation and destruction of organic matter accumulated in them. Detritus — organic matter at various stages of decomposition — plays an important role in soil fertility. By increasingly exploiting arable land, we promote the destruction of detritus and CO2 release into the atmosphere! It is more difficult to measure emissions related to this than industrial emissions, but they can probably be compared in intensity.
Today, carbon dioxide concentration in the atmosphere attracts special attention due to the assumption that it contributes to greenhouse effect enhancement. The greenhouse properties of the atmosphere are responsible for maintaining habitable conditions on Earth, and therefore even a small change in them may prove to be very significant for the biosphere. Obviously, our activity leads to increased carbon dioxide input into the atmosphere. Therefore, it must be reduced. The Kyoto Protocol to the United Nations Framework Convention on Climate Change was called upon to solve this task.
How to reduce carbon dioxide content? The usual answer is by planting trees. Unfortunately, a climax ecosystem absorbs as much CO2 as it emits. Otherwise, the amount of organic matter in the ecosystem would change and would transfer it to another quality. When wood is burned and organic matter in forest soil degrades, carbon dioxide bound by the forest returns to the atmosphere. However, as long as forests grow, they bind CO2.
What can help? Changing technologies. The well-trodden path: improve fuel combustion, increase the efficiency of heat engines, conserve energy. It is precisely such measures that the Kyoto Protocol pushes the economies of signatory countries to undertake. However, it is obvious that the measures being taken are still insufficient.
The Kyoto Protocol to the United Nations Framework Convention on Climate Change was signed by the leaders of developed countries at the end of 1997. Its task was to significantly reduce (for example, for Western Europe by 8%) industrial carbon dioxide emissions by 2010 compared to 1990. This limitation may slow the growth rate of the world economy by approximately 1% per year. Furthermore, in the second phase of the protocol's operation, which will begin after 2012, carbon dioxide emission reduction of approximately half should be achieved.
According to this document, highly developed countries can purchase emission quotas from other countries. Moreover, advanced states can earn the right to excess carbon dioxide production by financing the transition to modern technologies in other countries.
Are there more effective measures for reducing carbon dioxide emissions than those provided for by the Kyoto Protocol? The transition to other energy sources can be accelerated: nuclear, thermonuclear (if it works), solar, geothermal, wind, etc. All real alternatives to energy extracted from fossil fuels have their drawbacks, but they must still be developed.
Stop soil erosion. This requires rebuilding the thinking of every land user, switching their egoism from near-term goals (get now) to far-term (sustainably obtain in the future).
Can the ecological balance be shifted in the other direction? Yes, by ensuring accumulation of undecomposed organic matter: for example, growing forests, cutting them down, and filling abandoned mines with timber. But our activity is directed in the opposite direction: we extract organic matter from Earth's crust rather than burying it there! In the USA, the idea of pumping liquefied carbon dioxide into mines is being developed. But again, to obtain the energy needed for CO2 liquefaction, one must burn 30% more fuel. A vicious circle...
Accelerate carbon dioxide binding in limestone, calcium carbonate... This function is tirelessly performed by mollusks, reef-forming corals, foraminifera, and other marine organisms with calcareous shells and skeletons. Unfortunately, increased acidity of the World Ocean hinders their activity. They could use help here! But where, without significant energy expenditure (which increased carbon dioxide emissions require), to get sufficient quantities of calcium salts?
So is there no way out? At least we don't know one yet. Therefore, making the efforts we are capable of today, we should continue studying the relationships in Earth's climate system.
Humans arose when our planet was seized by chills. This is not coincidence — climate changes pushed animal evolution. Cold times occurred in Earth's history (for example, at the end of the Paleozoic, 250–300 million years ago), but the relatively recent period was warm. It began to get colder about 36 million years ago. As a result of lithospheric plate movement, Antarctica separated from South America and Australia and became located in the Southern Pole region. A circular current formed around it, reducing heat exchange with the rest of the planet. Antarctica became covered with an ice sheet, which reduced the planet's absorption of solar light and "cooled" the climate. But glaciation begins only when more precipitation falls on glaciers each year than evaporation and melting remove. And in Antarctica, isolated by currents, there was little precipitation.
Three to four million years ago, South and North America connected at the Isthmus of Panama. Warm Atlantic water, which had previously flowed into the Pacific, was directed north by the Gulf Stream and North Atlantic Current, thereby providing abundant precipitation. The glaciers of Greenland, North America, and northern Eurasia began to grow and moved southward in multi-kilometer-thick layers. They bound giant water masses; climate cooling changed atmospheric and oceanic circulation. But cold and dry air established over the glaciers, as a result of which glaciation "choked" and rolled back — a warm interglacial period began. The restored warm currents ensured glacier growth — glaciation began again.
Since then, Earth has experienced two dozen glaciations and interglacial periods (Fig. VI-12.3). Fluctuations in average temperatures during the cycle are measured in several degrees (up to 10°C), and sea level changes in tens and hundreds of meters. As a result of the last warming (over 20 thousand years), the ocean rose by 120 meters; melting of the Antarctic and Greenland ice caps could add another 65–70.

Fig. VI-12.3. Dynamics of average temperature at Earth's surface over the last 400,000 years
Besides the "great" glaciations and interglacial periods, there were also minor ones. Thus, from the end of the 9th to the end of the 12th centuries, the climate was particularly mild. During this time, Norwegian Vikings settled Greenland (the Green Country) and founded settlements in North America. With cooling, contacts with the colonies were interrupted and the colonists died out; the remains of the last of them bear the stamp of chronic malnutrition. And in 1450–1850, the "Little Ice Age" covered the canals in Holland and even the Thames with ice.