Is There Any Chance to Stabilize the Climate Looking Back on the Recent Geological History of the Earth

In science, there are only a few questions that can be answered without any doubt or explicitness. A professional or scientist should always be skeptical to a certain extent and should also tolerate some degree of uncertainty or disbelief. However, one of the few statements that a geologist can stand for quite flatly is the fact that climate on the Earth has never been stable and will never be. Let us have a look at what dramatic changes in climate the Earth had been through in a relatively recent history (Fig. 5.1).

In the Eocene, i.e. roughly 50 million years ago, the mean temperature on the Earth was about 12°C higher than nowadays [6, 7] and the content of CO2 reached values fluctuating around 1,000 ppm.

It is obvious that this content of carbon dioxide was three times higher than the value, which we presently consider alarming. In the period between the Eocene and Oligocene the climate began to gradually cool down so that the Antarctic was covered with ice for ten million years. This period was then followed by a warming up interval when the Antarctic glacier melted completely away. Another wave or spell of cooling down arrived as late as in middle of the Miocene, which is characterized by fierce, short-term climate oscillations, by alternating the so- called glacial and interglacial ages. For today's human beings, the following can be deduced from these facts:

i. We are now living in the coolest period of the Earth during the last 65 million years. Possible warming up even by 2-3°C stays within the common natural variations. Similar dramatic changes in temperature occurred without any contribution of human beings so that they can be unambiguously attributed to natural processes,

X,

Paleocene

Eocene

Oligocene

Miocene

4C 30

Millions of Years Age

Present

4C 30

Millions of Years Age

Fig 5.1 Changes in temperature on the Earth during the last 65 million years [7]

ii. The recent warming up of the climate is a fact, but the trend in the global temperature rise has already began before ca 300 years, after the termination of the so-called Little Ice Age. The rate of temperature rise corresponds to ca 0.6°C per century even in a period without any carbon dioxide emissions. The glaciers were also thawing, and as supported by data published by glaciologists, this process of thawing goes back to 1790 [8, 9].

iii. It is notable that the present content of CO2 is the lowest during the whole history of the Earth because the concentrations of this gas have tended to become lower for millions of years [7]. During the Earth's evolution the concentrations of CO2 decreased because carbon was deposited during the formation of coal, crude oil and, in particular, of limestone, while oxygen escaped to the atmosphere.

iv. The climate is such a complex phenomenon and process that its evolution cannot be restricted to a simple and direct relationship between CO2 content in the atmosphere and the temperature. Isotope investigations of drill cores from the Antarctic glacier at the Vostok research station showed a close relationship between the two factors but in inverse relation than expected [10]. Temperature rise preceded the increase of CO2 contents by ca 600 years. So, a classical question arises- what was the first: the egg or the chicken? If the theory of blaming CO2 for being responsible for global warming would be unambiguously valid, then the above-mentioned time shift would have been reverse. As a consequence, this gas evidently is not the only and decisive factor governing or influencing the climate on the Earth.

To point a finger at a sole perpetrator that is responsible for large climate variability is an intuitive but wrong suggestion because the climate is such a complex phenomenon that it is difficult, or even impossible, to determine a single decisive factor governing climate change. Nevertheless, only one reason stands out.

Greenhouse gases, sea currents, air circulation, volcanic eruptions, etc., are secondary phenomena only to the primary source of energy which enables life on our planet - the Sun. The power of the solar radiation impacts on the surface of our atmosphere corresponds to 1,373 W per m2. However, solar activity is not steady but fluctuates in more or less regular 11-year cycles. It rises for 4 years to reach its peak and then gradually decreases during the next 7 years. Only a few exceptions have been recorded in these 11-year cycle in the history of observations, but whenever the cycle was shorter, then the peak of the next cycle was more intense. On the other hand, when the cycle was longer the solar activity decreased. Since 1600, the above 11-year cycle was longer only twice always followed by an anomalous interval with lower solar activity. In 1790, the cycle took 12 years and 7 months followed by a quiet Sun lasting until 1830. This anomaly is called "Dalton Minimum". An even more significant event was represented by the so-called "Maunder Minimum" in the years 1638-1715 when sunspots disappeared for 77 years. Is it just a coincidence that this interval exactly corresponds to the decrease of temperatures during the Little Ice Age? Is it another coincidence when the subsequent 300 years of warming up of the planet falls in the period when the regular and moreover intense cycle of solar activity returns and culminates in the twentieth century? Astronomers predicted that the subsequent 24th cycle will be extremely intensive and will even surpass the record of the period of observations. According to all computations and simulations the new 24th cycle was supposed to begin in 2006 but actually started at the beginning of 2010. It is notable that 13 years elapsed since the beginning of the 23rd cycle.

It is almost certain that the 24th solar cycle will enter the modern history of astronomy [11]. We can only speculate on what effect on climate evolution this phenomenon will have; however a variant of the cooling down period cannot be excluded. Because of highly variable set of factors that influence the climate, including mankind, we are not able to answer a question: what is going to happen with temperatures and atmospheric precipitation within a few 100 or 1,000 years?

The global warming has stopped for a few years. Discussion about the effect of solar cycles or concentrations of greenhouse gases or other phenomena on the climate could be an interesting and useful scientific dispute that is a driving force of progress. We have to confess that the question of how important a role mankind plays in global change is still difficult to answer seriously. Apart from this uncertainty, we spend enormous financial means on activities related to stabilization of the climate. But, as mentioned above, the geological excursion into the past of the Earth clearly shows that the climate cannot be stabilized. We tend to reduce energy consumption, insulating and warming up buildings, but we are wasting huge expenditures on elimination of CO2 emissions that could be better spend on reasonable adjustments to global change. As will be demonstrated by the next example, the major reason of water scarcity on the Earth is not unfavorable distribution natural resources but poverty and lack of education.

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