Climate change is a natural feature of our planet. Why, then, is there so much talk today about global warming and the dangers that it poses? As part of the Many-Faced Geo lecture series, Aleksey Ekaykin, Senior Lecturer at St Petersburg University, spoke about the differences between climate change in the modern era and in times past.
Over the past hundred years, the average temperature of the air has risen by almost one degree. There have been no such precipitous changes on our planet for at least the past 10,000 years, and while during earlier natural fluctuations there were regions of warming and regions of cooling, today there is a warming trend over the entire earth. All of these presuppositions indicate that something unusual is happening to the climate now, and it can be traced to human activity. Global climate change was first raised as an issue around 60 years ago. One scientist who turned his attention to this problem was the eminent Russian climatologist Mikhail Ivanovich Budyko. In the early 1970s, he wrote, “As a result of human economic activities, by the end of this century the concentration of СО2 in the atmosphere may amount to .038 percent. Estimates suggest that, due to this increase in the amount of carbon dioxide, the temperature of the air will rise around 0.5 degrees Celsius.” Although he used what by today’s standards would be considered the most primitive prediction models, the scientist turned out to be right on the mark: the concentration of СО2 today is .04 percent.
The carbon dioxide content of the atmosphere can change up to almost unrestricted levels. Its natural concentration fluctuated between 180 and 300 ppm (parts per million), but it has now risen up to just shy of 400 ppm, which is the highest level over the past several million years. “Roughly the same amount of carbon dioxide was found in the Earth’s atmosphere during the Pliocene Era, but the climate back then was much warmer and there was much less ice on the Earth,” Mr Ekaykin observed. “In 1972, Mikhail Budyko wrote that with a СО2 concentration of more than 420 ppm, glaciation will not be able to occur on Earth, and contemporary models have borne out that conclusion. We are approaching a critical limit, beyond which there can be no glaciers on the Earth.”
Paleogeography, which offers a wide range of special methods, allows us to find out what the climate was like hundreds and thousands of years ago. One of these methods is familiar to all of us from childhood, and that is dendrochronology, which is based on observation of the annual growth rings of trees. But there are others that, though perhaps not as obvious, are more effective: analysis of the calcite deposits in caves, of the sediment at the bottom of the ocean and lakes, and of ice cores in Greenland and Antarctica. Even at the height of summer, the temperature at Stántsiya Vostók (the Vostok Station, a Russian research station in Antarctica) does not rise above minus 30 degrees Celsius, and, for this reason, snow deposits accumulate year after year. Samples taken from a glacier are unique repositories of climatic information. According to their isotopic, gaseous and mineral composition, we can retrieve data about the air temperature, dust content and chemical impurities in the atmosphere, and also measure the composition of the gas.
Despite the obvious link between human activity and climate change, some still deny not only people’s involvement in the process but the very fact of global warming. One segment of the population is even convinced that, on the contrary, we can look forward to global cooling. Mr Ekaykin explained that in another 5,000 -10,000 years our interglacial period should indeed be succeeded by a colder period, but with the increase in the concentration of carbon dioxide in the atmosphere this mechanism of alternating shifts in the climate might break down, and a new period of glaciation will simply not occur.
But even if all of the industrial production in the world were to cease emitting СО2 today, we can in any case expect continued warming: carbon dioxide is an inert gas, and its atmospheric lifetime is approximately 200 years. This means that glaciers will continue to melt, which will lead to a continued rise in the sea level. It is currently rising at a rate of 3.5 mm a year, and by the end of the 21st century perhaps it will have risen by a full meter, and, given the dynamic instability of Antarctica’s glaciers, this level could turn out to be even higher. There will be other consequences of a rise in the average temperature: a mass extinction of plant and animal species, the disintegration of permafrost and the spread of epidemics. And, as we can see, these processes have already begun.
In a special report that was released in October of this year, the Intergovernmental Panel on Climate Change concluded that a rise of 2 degrees, which was once thought to be acceptable, is no longer considered to be so and might lead to devastating consequences for all ecosystems. It is in fact essential to keep the rise in temperature at the level of 1.5 degrees, and taking into account that since the beginning of the Industrial Age the atmosphere has already “warmed up” by 0.9 degrees, we need to take immediate and extensive measures.
“What can people do to put a halt to global warming? This is a very difficult question. The intergovernmental group recommends that by 2030 we should reduce СО2 emissions by almost half, and by the middle of the century 85 percent of our energy should come from renewable sources. But the efforts of governments are not enough,” Mr Ekaykin said. “Each of us can and must do our part in order to reduce the emissions of carbon dioxide. For this to happen, we need, for example, to do more walking or ride a bicycle instead of using our cars. I have faith in the power of human intelligence and believe that if we want to, we will be able to cope with any problems.”