DEFEND FOR THE POOR CARBON
|2.0 Antarctic Ice Core Data|
|5.0 Heat Balance Mechanism||6.0 Further Interpretation of Ice Core Data||7.0 Coming Interglacial Peak Period|
6.0 FURTHER INTERPRETATION OF ICE CORE DATA
Figure 2.1 is the data extracted from the EPICA Dome C Ice Core. Each cycle from peak-to-peak indicates the interglacial warm periods. The interglacial period is circled in figure 6.1.
Many years ago, without human’s activities, global warming has been happening few times, the carbon dioxide level and temperature were fluctuated up and down drastically for few cycles. Without human’s contribution, what actually cause the increase of carbon dioxide level? Why carbon dioxide level decreases? what is the actual causation of the change of climate and the carbon dioxide level? The answer is the Mother Nature.
Figure 6.1 – Deuterium values from 740,000 years ago. The peak value corresponds to the peak temperature occurred during that period. The red colour circles indicate each cycle except circle (0).
From figure 6.1, for the year before 470,000 (represented by circle (0)), the interglacial cycles are not stable and the fluctuation is smaller. This reason will not be discussed here. From circle (1) to (5), the interglacial warm period is increasing. Note that the peak value for the current period (circle 5) has not been reached yet. This will be elaborated later.
From figure 2.2, the climate change data is extracted for the past 420,000 years. The peak of each cycle is the beginning of the ice age and the period between each cycle peak is the inter-glacial period. It is also observed that for each cycle, before the peak occurs, the dust level increases drastically and the period after peak, the dust level is very low as indicated in figure 6.2.
What causes the change in dust level? The major contributor is the volcanic eruption and the minor contributor is the meteor showers from outer space. When the heat accumulation of the Earth achieves certain level and the molten substances in Mantle layer become violent enough, mass volcanic eruption happens. Then, follow by great movement of tectonic plate and earthquakes. The volcanic eruption is the initial symptom of tectonic plate movement.
Figure 6.2 - Graph of CO2 (green), reconstructed temperature (blue) and dust (red) from the Vostok ice core for the past 420,000 years.
(A) For each cycle, it is observed that after the dust level achieves the highest level, the temperature then drops to lowest value. This is because the ashes produced by the volcanic eruption prevents solar energy entering into the earth and causes the earth temperature drops to the lowest value. When the temperature reduces, more ices are formed; the carbon dioxide level drops to the lowest due to absorption by ocean, glaciers and ices.
(B) Once after the volcanic eruption, the temperature climbs very fast. Heat gained to the Earth is more than the heat loss. It is caused by the tectonic plate movements or earthquakes, which release great amount of heat from the core to the surface of the Earth via openings on the crust layer. The released energy then heats up the ocean, producing more water vapour and releasing more carbon dioxide to the atmosphere. High content of water vapours then warms up the atmosphere. The ices and glaciers melts, the dissolved carbon dioxide is released to the atmosphere causes the carbon dioxide level increases.
(C) When the tremendous Earth thermal energy is released to the surface, the Mantle layer cools down and the tectonic plates stabilize. Heat loss to the outer space is more than the heat gained to the Earth. The water vapour concentration in the atmosphere is high and produces high amount of cloud and high precipitation. High precipitation at Artic and Antarctic areas reduces the water vapour content and increases the Earth surface albedo. The amount of reflected solar incident increases and the solar energy that enters into the Earth reduces. Low water vapour content in the atmosphere encourages for high emission of Earth thermal energy to the outer space and reduces the earth temperature. The carbon dioxide level decreases due to absorption into ocean, ices and glaciers.
(D) The Earth thermal energy from the core begins to accumulate again. In between the interglacial cycle, small changes on the climate are caused by the mild volcanic eruption and earthquakes. The carbon dioxide level follows the pattern of the temperature which corresponds to the ocean temperature, forming and melting of ices and glaciers. The minor change on the weather is caused by the solar energy.
(E) One complete interglacial cyclic process and it repeats.
Approximately 30,000 years ago, the increase of dust level in the atmosphere had activated the rise of the next up-peak interglacial warm period and the temperature shoots up. Around 11,000 years ago, a short term ice age, named Younger Dryas occurred. The temperature fluctuates and maintains until today as shown in figure 6.3.
Figure 6.3 – Temperature rises from 18,000 years to 11,000 years BP. Temperature is maintained from 11,000 years (before period) until today.
This relapse was more pronounced in the northern hemisphere, as was another glacial relapse known as the Younger Dryas around 11,000 BP. It seems the northern hemisphere is affected more by global temperature changes than the southern hemisphere. This could be explained by the fact that the North Polar sea ice is much thinner and much less extensive than the South Polar continental ice, and is therefore much more susceptible to melting under warm conditions, thereby precipitating shifts or shutdowns in the thermohaline circulation.
The temperature supposes continue to rise, but the Younger Dryas ice age is a little short term ice age that prevent the rise of temperature. With the high albedo, it helps to reduce the solar energy gain, but unable to reduce the Earth thermal energy gain. The short term ice age stops the rising of temperature, but fails to trigger the low-peak ice age, where the Earth temperature should drop to around -8°C, as indicated by previous glacial phases. This hints that the coming glacial peak for the current interglacial cycle has not been reached yet; the heat from the Earth core has not been exhausted adequately.
Figure 6.4 – Temperature and carbon dioxide concentration for the past 200 years. This time period includes all of the Industrial Revolution which began in the mid-1800s. The start of the Industrial Revolution marked the beginning of the large-scale exploitation of fossil fuels. The small dip in temperature in the early 1800s was caused by volcanic eruptions which reduced the amount of sunlight reaching the Earth's surface. CO2 inflection points are visible at around 1860, 1950 and 1975. After 1958, the data are from annual air measurements, not ice core proxies, and are therefore of higher quality.
For the last 200 years, the carbon dioxide level increases correspond to the increase of temperature. Until the last 40 years, the temperature fluctuates at around 0.5°C while the carbon dioxide level increases higher due to large-scale exploitation of fossil fuels. The increase of carbon dioxide level does not increase the temperature proportionally. Note that the measurement is very depending on the place of locating the sensors. Before the last 40 years, the carbon dioxide level is taken from ice core, it is coherent with the Vostok and EPICA Dome C ice core data and the profile for temperature and carbon dioxide level is the same. For the latest 40 years, it is taken on land, nearer to human’s activities, the base references are different.
Comparing to the interglacial period, the study of 200 years period is too short to conclude or hint that the carbon dioxide is the major contributor to the global warming. By looking at a bigger picture, it is more concern on the activation of the next interglacial period, where the temperature will continue to rise, even without human’s activities.
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updated on 27-April-2010.
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