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How Dust helped cool down the earth

How Dust helped cool down the earth

Temperature variations are a common occurring on earth, or anywhere in the universe. Due to uneven heating of the atmosphere some regions get hotter while some remain cooler. Even the presence of gas or cloud cover affects how the sun heats places on earth. Now, this may be the observation over past few decades. If we look at the history of our earth, we can find many such heating and cooling cycles which have made the earth hot at times or even engulfed vast regions with ice!

 

The historical data about the earth’s climatic variations are preserved in icy regions such as Antarctica. We can observe different layers of ice which represent a variety of conditions that were prevalent on earth. The gas bubbles trapped in the ice are also a valuable source of information. Different tests have shown a varying level of concentrations of atmospheric gases such as CO2 throughout the past millions of years.

 

The most visible feature of these ice samples is the layers. Ice core samples show variety of different layers. Some of them are gray, dark brown or white. A dark layer indicates dust accumulation.

 

During 1980s, Oceanographers found less density of planktonic growth in certain parts of the ocean where nutrients were high in supply. The reason for lack of growth was limited supply of iron, an essential element for planktonic growth.

 

Along with that discovery, they also found reduced concentration of CO2 in the adjacent Antarctic and increased levels of dust. Upon analysis they found that the dust contained iron which was flown during from Patagonia in South America. When the glaciations melted, they carried the dust into the ocean and the phytoplankton used it. They also require CO2 for photosynthesis which they take from the atmosphere. Thus a firm relation is established between CO2 and dust flowing in the atmosphere. More dust equates to more absorption of CO2 from the atmosphere. When these creatures die they sink to the bottom taking the carbon with them!

Testing the theory is a complex task. These phytoplankton utilize nitrates for their growth. Notrogen-14 and nitrogen-15 are two isotopes whose ratios would be helpful in measuring the growth activity. When the supply of iron is constrained, they tend of consume some of the nitrates based on nitrogen-14 for survival. By measuring the amount of nitrogen-14 and nitrogen-15, the result can decide whether CO2 levels were directly related to dust.

 

To our surprise, the CO2 levels were on decline during the last glacial meltdown and the amount of iron rich dust in the atmosphere was high in amount. The dust flow was also consistent with the glacial meltdown happening around that time in Patagonian region.

 

By looking at today’s scenario, it comes to our notice that the atmosphere warming effect caused by CO2 is high. Due to high ocean water density CO2 absorption is very less. The climatic swing today could have been less intense as compared to the past records, but we are facing an amplified climate change effect due to excess of CO2. We can take the analogy of spending money. One can spend all his salary at the beginning of the month and survive on payday loans, but when it comes to climate change, you can spend all your resources at once, but recovering from the damage will always take several decades, perhaps even centuries because it is the natural world we are dealing with. There is a growing trend today where many small time research publishers borrow payday loans and try to repay after publications, which they cannot. Once in debt, forever in debt. The same applies for environment. Once in trouble, we are not going to get out of it so soon! 

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Atmospheric Science