Global warming, what comes to your mind when you hear those words? Perhaps many will express his opinion! Increasing the average temperature of the earth's surface, of course! In the last hundred years, the average temperature on Earth has increased significantly due to various human activities, the explosion of the industrial revolution one of them and its relation to other phenomena. Well, I will continue, hopefully useful!
When the total lunar eclipse may be many of us who think, the sun rays that fall to the surface of the Moon will be completely obstructed Earth. So the Moon will be really dark due to not receive a glimmer of sunlight at all. It is not. When the Earth's position lies between the Moon and the Sun in a total Moon eclipse configuration, which is completely blocked is the direct sunlight. While indirect sunlight, the first beam of light through the Earth's atmosphere, can still reach the Moon's surface after being refracted by layers of the atmosphere. But the Earth's atmosphere makes these sunbeams scattered and absorbed by air molecules, moisture and ozone, especially in light with shorter wavelengths (bluish color). So the intensity of sunlight that the atmosphere passes towards the Moon at the peak of the eclipse is much lower than the original and dominated by light with a longer wavelength (reddish).
The Moon does not completely darken as it passes through the umbra because Earth's atmosphere refractssunlight into the shadow cone.wikipedia
This phenomenon has been understood by Johannes Kepler since the dawn of modern astronomy sprouted more than four centuries ago as it appears in "Astronomiae Pars Optica" (1604). This is the reason why in the peak of the eclipse, the Moon still looks even though much dimmer than the full moon in general and reddish as blood. Although dim seems to us, for the size of the celestial bodies then the Moon at the peak of the eclipse classified with a pseudo-magnitude could be close to -3 or more brilliant than Jupiter. At the same time, if we were on the Moon at the same time and looking toward the Earth, then the Earth was not really completely black but visible surrounded by a reddish-colored circle like the scene of the peak of the solar eclipse of the ring. Photographic evidence first appeared in 1967 based on the image of NASA's (3rd) Surveyor 3 landed craft, followed by the image of the Kaguya orchid spacecraft (Japan) in 2009.
The problem is, the Earth's atmosphere does not always behave so in every total Moon eclipse event. If the atmosphere is "dirty," ie, filled with sulfate aerosols, the transmission of sunlight through Earth's atmosphere will be greatly disrupted. Then the sunbeam that was passed on to the Moon at the peak of the eclipse would have a much lower intensity than in "clean" atmospheric conditions. Because sulfate aerosol is a very effective sun-absorbing sun so dubbed as a sunscreen. There are only three events that can make the atmosphere overwhelmed by aerosol sulfate in large numbers, namely all-out nuclear war, large volcanic eruptions and collisions of celestial bodies (comets/asteroids) of large diameter.
The last two are natural events. And in between, the frequency of big volcanic eruptions is much higher than the collisions of large-diameter celestial bodies. Therefore, the abundance of aerosol sulfate in the atmosphere is often associated with volcanic activity. Where the eruption dissipates sulfur gas (SO2), as one component of volcanic gas, in large quantities to the atmosphere. Next comes the reaction with water vapor and oxygen gases so that the colloidal sulfuric acid droplets are formed so that the form of the aerosol. Aerosol sulfate not only scattered within the troposphere course but also soar and evenly in the stratosphere layer. Sulfate aerosols entering the stratosphere cannot be reached the weather processes so that did not participate in the rain. It will last for several years before Earth's gravity gradually forces it to descend into the troposphere layer and then falls back into the surface of the Earth along with rainwater.
The absorption of sunlight that is transmitted from Earth's atmosphere to the Moon has implications on the darker / dimmer Moon at the peak of the eclipse. The characteristic red color of his blood can even disappear, replaced by more pale colors. Generally speaking, the larger the quantity of aerosol sulfate in the atmosphere, the Moon becomes dimmer at the height of the eclipse so the brilliance is smaller. By measuring the brightness of the Moon at the peak of the eclipse by using a photometer instrument or the like and comparing it to the brightness of the Moon calculated in "clean" atmosphere conditions (cloud cover is assumed to be 50%), the quantity of aerosol sulfate in the atmosphere termed AOD (aerosol optical depth) and expressed in tau parameter can be known. In general, the value of AOD is equivalent to a decrease in the apparent magnitude of the Moon at the top of the ellipse relative to similar conditions when the "clean" atmosphere is divided by 40.
Global Warming and mountain eruptions
Moon is very dim at the peak of the eclipse has been realized after the eruption of Tambora 1815 sourced from Mount Tambora, Sumbawa island (Indonesia). The eruption of Tambora 1815 releases 150 cubic kilometers of volcanic material (scale 7 VEI) and has global impacts in the chaotic shape of the weather in all directions with all the impacts of human civilization at that time. However, photographic evidence emerged only after the eruption of Krakatau 1883, which originated from Mount Krakatoa in the Sunda Strait (also in Indonesia). Although smaller with volcanic material volumes spewing 'only' 20 cubic kilometers (scale of 6 VEI), the development of photographic technology allowed the Total Moon Eclipse post-eruption to be enshrined, on October 4, 1884, and January 28, 1888. But AOD's measurements constantly utilized the events of a total new Moon eclipse begin to take place since 1963.
What is the importance of knowing the value of AOD?
The abundant sulfate aerosol entrenched in the stratosphere as a sunscreen not only absorbs the sun's rays that should be transmitted to the Moon at the top of the eclipse but also absorbs the sun's rays toward the Earth's surface. This absorption makes the intensity of solar radiation on the surface of the Earth to be decreased than normal. Consequently, the average temperature of the Earth's surface also decreases, a phenomenon known as global cooling. The magnitude of the temperature decrease is directly proportional to the value of AOD, where each increase in AOD value of 0.1 will have implications for a decrease in temperature (global cooling) of 0.4 degrees Celsius. With this formula, it can be seen that the eruption of Krakatau 1883 impact on a temperature drop of 0.5 degrees Celsius.
The global cooling due to large volcanic eruptions can cause widespread disasters, as seen in the 1815 Tambora Eruption. But for Earth that has been heating up since the industrial revolution as massive exploitation of fossil fuels along with the emission of greenhouse gases in quantities great, that global cooling is the long-awaited hidden grace. Because global cooling can reduce the quantity of global warming even for a moment. In other words, the volcanic eruption was a factor that helped break the rate of rising in the Earth's surface temperature due to human activity, without any intervention.
This fact can be seen in the continuous measurement since 1979 until now. In the period 1979 to 1995, Earth was struck by a series of major volcanic eruptions, such as the St Helena Eruption 1980, the 1982 El Chichon Eruption and its peak was the Pinatubo Eruption 1991. The eruption of St. Helena 1980 sourced from Mount St. Helena in Washington state, which releases 1 kilometer cubic of volcanic material (scale 5 VEI). While the 1985 el-Chichon Eruption is sourced from Mount El-Chichon (Mexico) which releases 2 cubic kilometers of volcanic material (scale 5 VEI). And the 1991 Pinatubo eruption came from Mount Pinatubo (Philippines) which released 10 cubic kilometers of volcanic material (scale of 6 VEI).
These eruptions cause the Earth's atmosphere to be relatively "dirty" as seen in the average AOD value of 0.035. Post-Pinatubo, no major eruption/volcano of the volcano until now except a number of 4 VEI-scale eruptions such as Eyjafjallajokull eruption 2010. So in the period 1996 to 2012, the Earth's atmosphere is relatively clean as seen in the average AOD value of 0.002. Thus a change in the value of minus 0.033 correlated with an increase in temperature of 0.13 degrees Celsius. At the same time, there is also an increase in the number of greenhouse gases that contribute to an increase in temperature of 0.11 degrees Celsius. Of these greenhouse gases, carbon dioxide (CO2) gas alone contributes to an increase in temperature of 0.08 degrees Celsius. So calculated in 2012 there has been a total temperature increase of 0.27 degrees Celsius than the situation in 1995. Half of them due to the increasingly clean atmosphere in the absence of a large eruption / terrible volcano.
With a maximum AOD of 0.009 then the apparent magnitude of the Moon changes at the peak of the theoretical point of 0.4. Except for using a photometer, this apparent magnitude change is very difficult to identify visually. Therefore the Moon images at the peak of the eclipse presented at this time always show the Moon reddish and relatively bright. And if the maximum AOD value is compared with the average AOD value for the period 1996-2012, it is obvious that on paper there is a change of 0.007. Theoretically, these changes will correlate with a temperature drop of 0.03 degrees Celsius. This temperature drop is small enough that it may be insignificant in the face of global warming. But it still needs to be investigated further.
Regardless of the outcome, it's pretty amazing that the Total Moon Month event is not just an impressive sky event. But he is also full of benefits. Now the benefits are increased by one, where the Total Moon Eclipse allows us to measure the Earth's atmospheric quality in relation to climate change in the form of global warming and cooling. thanks!
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