Climate change 2

Climate on earth

Through the centuries Earth has always had climate variations What must be analyzed is how great they are,  the impact that they have on our lives, and how long they last. In a human being’s life time, one can experience seasonal or annual changes, such as years that are warmer or rainier than others. Throughout the centuries, in fact there have been much greater climate variations than we have nowadays. An increase  in temperatures is always associated with the melting of polar and continental ices, with the consequent rise in sea levels. In the past 500 million years sea levels have varied by as much as a few hundred meters (200-300 meters) from nowadays level but with a much longer duration, roughly 300 million years, which means that they would not have been noticeable in a man’s lifetime.

Sea level oscillation causes

There are several different causes involved in sea level oscillation but they are usually geological, climatic, astronomic or anthropical events.
The main ones are:

• variations in ocean basin capacity, meaning the areas occupied by water
• variations in the amount of ocean water
• minor variations such as: sea water density, sea water desiccation, marine meteorological  parameters (atmospheric pressure and winds)

In the first case, variations in ocean basin capacity are caused by geological processes within the planet. We know that on the ocean floor there are belts called “oceanic ridges” where magma moves upwards, towards the surface swelling the earth’s crust so the mass of water is displaced with the consequent rise in sea level. This is very slow process which causes the level to vary by approximately one centimeter every thousand years so man cannot notice it in a lifetime.
Ocean water quantity variation, instead, is brought about by climatic causes: during colder weather periods, a large part of the water of the oceans is trapped in the Arctic and Antarctic glacial caps as well as in continental glaciers, while during warmer weather, the ices melt causing the sea level to rise quickly, as much as one centimeter per year.
In the past century large quantities of man made greenhouse gasses have been added to the natural causes which are bringing about climate changes at a much faster pace, and all this is having a big effect on us.

Quaternary or glacial era

Major climate variations have taken place during the Quaternary period (the past 2,5 million years), which is when man made his first appearance on Earth, caused by the massive expansion of the polar caps approximately every 100 thousand years, that made the sea level decrease by as much as 120 – 140 meters below what it is today.
We must bear in mind that the last glaciation allowed man to spread all over the world, thanks to the spits of dry land emerging from the lowered sea level.
These periods were followed by other warmer ones with temperatures which were similar to the ones we have today which allowed the ice to melt and consequently increase the sea level.      
Shortly before the beginning of the Quaternary because of the tectonic plates which allows vast areas of dry land to shift, the distance between south America, Africa and the Antarctic continent induced an ocean current similar to a gigantic “river” moving a volume of water 100 times the size of the Amazon River. This river submerged from the north Atlantic, reaching the ocean floor and traveling the whole length of the Atlantic Ocean from north to south going around Africa to then spread into the Indian Ocean while part of it went as far as the Pacific Ocean. This enormous volume of water is still moving today and acts as a huge conveyor belt for heat, as though it were a gigantic air conditioning system  that controls the weather on Earth. When the hot current reaches as far north as Iceland it encounters the cold winds from Canada so it cools off, releasing the heat into the air and mitigating the effect that these winds would have on northern Europe.
With the evaporation water becomes more dense and tends to sink, generating a cold deep current. The amount of heat carried by this enormous “conveyor belt” depends obviously on how much is stored during its formation. At present the “conveyor belt” is near Iceland, but its latitude can vary, oscillating to the point of interruption, thus causing a break down of the heat distribution system.
As time passes, the sun’s heat reaching the surface of Earth and the sea, changes according to the orbital parameters of our Planet.
There are three main causes for latitude variations:

• shift in the axis inclination of Earth’s rotation: the Earth’s axis inclination has a slow oscillation that goes from 21,8° to 24,4° in a stable period spanning approximately 40,000 years. Currently the angle is 23.45° and is decreasing, thus diminishing the contrast between summers and winters.
• changes in the eccentricity of Earth’s orbit: the planet’s orbit changes from an almost perfect circumference to a marked ellipse. When it is an ellipse, the planet is closer to the sun, otherwise, it is more distant. A complete orbital cycle going from an almost round orbit to an ellipse one and vice versa, takes 100,000 years.
• precession of the equinoxes: this is the celestial phenomenon whereby the axis of our planet goes a complete circle around an imaginary cone every 26,000 years. This is the reason why the seasons have a slow tendency to come sooner and be modified. The same thing happens when one spins a spinning top which in fact is very difficult to keep straight with its axis perfectly perpendicular to the ground. It is more likely to have an eccentric spinning motion and its point will gradually design a cone as it goes around. Something similar happens to our planet although the forces that cause this are obviously different.

Therefore, over thousands of years, Earth changes its position with respect to the sun to then start all over again every 26,000, 40,000 and 100,000 years. The combination of these three elements will modify the amount of energy(Watt per m2): when the point of no return is reached, the heat is so intense that the glaciers melt and reach a peak, whereby the climate is similar to what we have nowadays and lasts for a time span ranging from 6,000 to 13,000 years, until Earth’s geometry gradually changes causing glaciers to build back up quite quickly (within just a few hundred years).

Geological traces

In certainly is no easy task to retrace all the sea level variations that have happened in thousands of years. Several different geological techniques which focus on studying specific areas near the coastlines have been used to trace these variations.

• the sea digs a horizontal crevice at water level at the base of a cliff which becomes deeper as time goes by. When the sea level decreases, it makes a new etching. Sea level variations can be discovered by measuring the height difference between these two marks
• speleothem: if near the sea there is a cave with stalactites, one can discover sea level variations by studying these stalactites. When the sea level is below the cave the stalactite grows because the water that seeps into the cave causes calcium carbonate to deposit, whereas its formation stops when the sea invades the cave but some organisms carry on with the stalactite’s concretion. These animals which are called serpulides have a calcium carbonate outer shell which therefore can be given an age with the radiocarbon technique and thus enable us to discover when the sea came into contact with the stalactite
• when the sea level rises and encounters a specific land conformation it will form a very shallow inland lagoon called “paleolagoon”. This lagoon is where sediment and fossil shells will deposit. Then when the sea level diminishes, one will find organic deposits at different heights on the hills. The age of these deposits is analyzed in order to find out when the sea was at that specific level
• when the sea level rises and meets a shelf made of soft rock which is easily eroded, it creates a terrace shaped platform known as “marine terrace” and a sort of slope. At the flex point between the abrasion platform and the beginning of the slope, a place called the “inner edge”, one can measure the sea level of the past.

Climate variations

If we have many geological markers we can draw a eustatic graph which traces the different sea levels over the millennia. For instance, 220,000 years ago the sea was 3 meters below its current level and about 140,000 years ago it was as much as 140 meters below its level nowadays. Right after that, during the Tirrenian period about 125,000 years ago it rose suddenly to 7 meters above today’s level.
That was a very warm period, much warmer than it is today and with a much higher concentration of carbon dioxide. Obviously, if the sea level was 7 meters above what it is today, many of the current coast areas, such as Venice, did not exist.
At a much more recent time, about 22,000 years ago, there was the last glacial acme, which is the coldest moment of the last glacial era which had lowered the sea level by approximately 120 meters. At this time half of the Adriatic was dry land, Corsica and Sardinia were joined together, Elba was part of the peninsula, and Sicily was joined both to Italy and to Africa. Thanks to these dry lands, many African animals were able to migrate and settle in Italy (i.e. rhinoceros and elephants). Once the islands became separated from Italy, these species adjusted to the new environment, spawning new characteristics such as dwarfism. In fact, fossil remains were found in Sicily of a dwarf elephant that was no more than 1 meter tall. It was much smaller than its African relatives because on the island there were no predators that it would have needed to protect itself from but there was also little food available. With this great a decrease in sea levels, man found new fertile lands and hunting territories.
After the glacial acme, the sea level started rising again until the present day.
Therefore, at the end of the Glacial Era, a new warm phase began and the ices have melted making the sea rise very quickly (about 10 meters in 100 years). In fact we find both historical and religious references to this period which became known as the Deluge.
The plains that were inhabited by man were flooded by the sea which forced man to move several times in a lifetime, specially in the areas surrounding the Black Sea which are rather flat. About 10,000 years ago the sea was 50 meters below today’s level, then there was a global warming trend so the sea level rose suddenly about 5,000 years ago. This phase peaked approximately between 7,500 and 4,600 years ago, when Earth reached its highest temperatures in the past 10,000 years. About 6,000 years ago the Sahara had a very humid climate and was covered with grass lands that were inhabited by highly civilized populations.

Recent ages

During the Roman era the climate was rather warm, and we have proof of this from the pools that Ancient Romans used to breed eel. In fact these pools had two holes, one at high tide level and the other at low tide level. At high tide fresh sea water would come in through the first hole while stagnant water left the pool through the second one at low tide, so that the pools had a constant fresh water turnover which worked the same way as modern day aquarium filtering systems. Tides in the Mediterranean sea range approximately 20 cm. so we can know exactly where the sea level was at in those times and consequently we also know what the climate was like.
In history we are told that in 218 b.c. Hannibal crossed the Alps with elephants, which gives us a reason to believe that at that altitude there was no snow, or better yet, perennial snow was easily accessible as opposed to nowadays. Photo 15
In the Middle Ages they had a long warm period that spanned more or less from the 9th to the 12th century. At the time grapes were grown in England, 500 km further north compared to today.
From about 1200 to about 1850, Earth went through a long cold phase which affected particularly Europe. The Vikings left Greenland where the ports were blocked by ice. The glaciers crept forward and many alpine valleys were abandoned. This is the coldest time in the past 8,000 years, and is in fact called the “Small Glacial Era” and 1816 will go down in history as the year without a summer: In paintings from the 1700s Venice is portrayed as being completely frozen and Bethlehem is covered with snow. Apparently, even during the famous Waterloo Battle, heavy rains had blocked Napoleon and left his cavalry troops stranded in the mud.
After that the temperature rose until it reached its peak in 1950. Photo 4
Between the Small Glacial Era and today average temperatures have risen by 0.5 – 1.0 degrees. World glaciers are shrinking while sea levels are rising by about 2 mm. per year. This is the global warming which apparently has been caused by man. According to some scientists such as those from ICRAM (Istituto Centrale per la Ricerca Scientifica e Tecnologica Applicata al Mare), the current phase might indicate a part of the hot/cold cycle with a normal rise in temperatures following a cold phase which peaked, as we mentioned, during the first half of the 19th century, one of the most obvious in the middle and recent Holocene age.

Future IPCC scenarios

In the past 20 years scientists have researched calculation models which try to foresee climate variations. These models are known as GCM (General Circulation Models). Some IPCC studies have been able to foresee four possible future scenarios (A1, A2, B1, B2), by taking into consideration population growth, economic development, available resources (meaning primary energy sources) and technology. These hypothetical evolutions are called “scenario families”.

A1: this scenario family foresees a rapid economic growth, the population will continue to increase until 2050 to begin decreasing after that and there will be a rapid introduction of new more efficient technologies. This family develops three groups that describe alternative directions for technological development in the energetic system: A1FI a future with fossil fuels, A1T non fossil resources, A1B a balance between fossil fuels and other sources.

A2: This scenario foresees a very heterogeneous world. There will be a constant demographic increase with very slow and irregular pro capita economic growth and technological development.

B1: This scenario as well foresees that the demographic growth will continue until the middle of the century to then start decreasing, but there will be a fast change in the economic structure towards an economy based on information and services, with a reduction in material use and the introduction of clean and efficient resource technologies, in other words there will be a sustainable kind of development with limited use of resources.

B2: The population will continue to grow but at a slower rate compared to the A2 family, the economic development will be average and technological changes slow and differentiated but always aware of  sustainable development.
Each scenario is supposed to have different levels of carbon dioxide emissions for the period ranging from 1990 to 2100.
The main changes pointed out be the models besides the increase of greenhouse gas concentration in the atmosphere are the following three:

• Global warming of the lower atmosphere and the planet’s surface.
• Acceleration of the water cycle in the atmosphere and the ground.
• Sea level increase.

Global warming
All mathematical models that have been studied so far foresee an overall warming of the lower layers of the atmosphere and of the planet’s surface of 1.5 to 5.8 °C and a cooling of the upper layers of the atmosphere. There will be different changes at different latitudes.
High latitudes (polar and subpolar areas):
During the winter temperature increase will be greater than the global average increase and will affect the dry lands more than marine surfaces. At the poles there will be a decrease in marine ices and because ice plays a role in heat exchanges among the oceans, warming of the arctic areas and high latitudes will be greater. During the summer instead, the temperature increase will be lower than the average global one because of the strong thermal influence of the ocean.
Intermediate latitudes (mild areas):
During the summer temperature increase in the northern hemisphere will be greater than the global average, whereas during the winter it will be very similar to the global average.
Low latitudes (subtropical and equatorial areas):
Temperature increase in these areas will be minimal and lower than the average global heating. As opposed to other latitudes, it will be even throughout the seasons. This area is occupied mostly by the sea so surface temperature increases will only increase water evaporation rather than making the air temperature warmer.
The water cycle in the atmosphere and the ground
Precipitations will increase globally because of the rising temperature, and because there will be more evaporation which will mean more water vapor in the atmosphere, this will increase the amount and speed up the water cycle in the climate system.
Precipitations will increase particularly at high latitudes and the intra-tropical area both during the winter as well as during the summer. At intermediate latitudes instead, precipitation will increase only during the winter months. Locally some areas will have more dry spells and/or floods while others will have less. Rains will become more frequent and more intense so there will be an increased risk of floods. Photo 29
At present we do not dispose of sufficient data to know if floods, hurricanes or tropical cyclones will increase or simply change the areas where they occur.
Sea levels
The average sea level will rise because of the ice melting and, according to the more pessimistic forecasts, it could rise as much as a meter higher than it is today; whereas according to the more optimistic forecasts it will rise by only 10 to 20 cm. Intermediate scenarios expect the sea level to rise  50 cm. by 2100.

Future forecasts

And if an extraterrestrial creature should land on Earth…
In the 1700s James Hutton, geology’s and modern scientific reasoning’s forefather, invented the “Principle of knowledge”, according to which it is necessary to study the past in order to have the key to understanding the present and attempt to foresee the future. Only through intensive scientific research it appears possible to separate the influence of human actions and activities from the long term trend which is determined by natural events. Hence the great importance of science both in terms of prevention which can cut the huge costs of intervention following natural disasters, and as a means to help plan future population developments, in other words, sustainable development. One must bear in mind that climate cycles have always occurred on planet Earth, therefore one must study and observe very carefully what happened in the past. In fact, as scientists working for ICRAM say, a hypothetical visitor from outer space, could consider Earth’s climate evolution in a completely different way based on the observation’s time span. Let’s imagine that our extraterrestrial visitor’s spaceship has broken down and he has landed on a beach in the early hours of the morning. This creature, who knows nothing at all about astronomy, will notice that the temperature will increase drastically between 8 o’clock in the morning and midday. What is going to happen in the next few hours? The extraterrestrial may think that he is destined to fry under the sun but in the following hours, as dusk and night arrive followed by a new day, will help him to understand that there is a daily cycle.
In the same way, by observing the climatic evolution of the past century, we can notice a global warming trend of the climate. This trend however is a natural part of secular variations that have been happening since the beginning of history. In the same way, if we could record climate variations for a period of time spanning hundreds of thousands of years, we would notice the alternation between glacial and interglacial cycles.
The catastrophic forecasts on sea level increases issued during the ‘80s by the United States Environmental Protection Agency, that foresaw an increase between 0.56 and 3.45 meters within the year 2100 have been disavowed and estimates have lowered considerably. In 1986 it was still a common belief that the seal level could rise by as much as 2 meters during the next century, while more recent forecasts expect a more likely half a meter increase in the sea level by the year 2100. Obviously even if “only” a half meter rise occurs, it would have some very negative consequences on the environment such as erosions, floods, saline intrusions, etc. As one can imagine, problems would be greater for coastal areas and flat lands.
The degree of uncertainty of the different forecast mathematical models studied so far is still too high, while local effects, which are normally not taken into consideration in global estimates, could very likely be predominant. On the other hand it is very difficult to foresee what will happen to the climate in 50 years time when we are not even certain of what the weather will be like tomorrow!
We still have many doubts even from a scientific point of view so we must do more research in order to understand better the complex climatic patterns, and take advantage of the so-called “precaution principle”, that is to foresee the worst case scenario in order to “prevent” before the “cure” may become useless. Worst case scenario forecasts, even though uncertain, must always be taken into consideration when facing environmental planning and managing activities.
And what can each one of us citizens do in this climate of uncertainty? Obviously each and everyone one of us can help. One just needs to think that 25% of North American carbon dioxide emissions are produced by private citizens, which is the equivalent of 9 tons of CO2 pro capita per year.
How much CO2 do you think you produce in a year? If you care about saving the environment, you can work it out by going to http://www.ealp.it/iclei/italco2calc.htm and that will help you to understand how much you yourself can really do to help the whole planet!