The crystal teal waves crash against the ocean’s rocky shore. Out in the distance huge blooms of emerald algae drift under fluffy white clouds that are sprinkled throughout the royal blue sky. The air smells of salt, that distinctive bracing smell, caused by dimethyl sulfide (DMS). Dimethyl sulfide, given off by the algae as a waste product, is contributing to the cloud formation above the beach.
The cloud formation has a significant impact on the Earth in terms of global warming. Clouds are important regulators of solar radiation by reflecting incoming short-wave radiation from the sun and absorbing and re-emitting long-wave radiation from the Earth’s surface. Clouds, therefore, absorb UV radiation and solar radiation .4 reducing the global temperature. Clouds are made of water vapor, which is more efficient at absorbing solar radiation than carbon dioxide. Cloud cover helps maintain our planet’s delicate balance of gases to sustain life.
Clouds from Algae?
Algae produce dimethylsulphoniopropionate (DMSP) to keep their osmotic balance with seawater. If they did not produce DMSP, they would become dehydrated. DMSP is believed to be released when algae die or are grazed upon by zooplankton. DMSP then breaks down in the sea to form DMS. About a tenth of DMS enters the atmosphere, while the rest is consumed by bacteria or broken down by sunlight to form dimethylsulphoxide. Once in the atmosphere, DMS forms three compounds: sulphur dioxide, sulphates and methane sulphonic acid. Water vapor can condense around the last two and form clouds. "Approximately 60 million tons of biogenic DMS emissions are transferred from the oceans to the atmosphere annually." (Phillips 1992) Robert Charlson (1987) hypothesized that this is how clouds are formed in remote open regions of the ocean. Could the increase of production of algae blooms help cool the planet?
Algae have been researched as a useful, natural possible solution to global warming. Algae blooms reach their peaks during the summer and spring and can be as much as a hundred times greater in production than in the winter depending on their location and concentrations of DMS. There are many different types of algae that produce DMS in different qualities.
Our Atmosphere
To understand the role that algae play in cloud formation, one must first understand how clouds regulate the temperature of Earth and the other important components of our atmosphere. Most of the planetary radiation is absorbed through water vapor, carbon dioxide and ozone. Water vapor has a number of absorption bands near the infra-red part of the solar-radiation spectrum. The amount of water vapor in the atmosphere in any given region over the globe will depend on how much infra-red absorption will occur.
Aerosols are also a part of our atmosphere; they can be naturally produced by wind turbulence or man-made from industries. Natural aerosols are usually more abundant than man-made, except in highly industrialized regions. Aerosols are small-suspended particles that scatter and absorb solar radiation. The scattering of solar radiation increases the path length of a proton through the atmosphere. In response to this, aerosols indirectly increase the probability of absorption.
Sulfite is a vital biochemical element that is found in our atmosphere as well. Its primary sources are from volcanic emissions, sulphur in microorganisms and sea salt returning to the geosphere through sedimentation. "Algae transfer between 20 and 50 million tonnes of sulphur from the oceans to the atmosphere each year, while human activity only accounts for 80 tonnes." (Fell, Liss 1993) "Human activities increase the input of sulphur into the troposphere in the form of sulpher dioxide and ammonium sulphates, and the effect of this input is important both in the formation of acidic rain and its influence on solar radiation. The carbon input from coal- or oil-based industries can also produce significant reductions in the solar radiation." (Wells 1997) Sulfur clouds can block solar radiation naturally, as well, by volcanic explosions.
Clouds are the most significant influence on solar radiation. Cloud droplets are larger than aerosol particles and scatter radiation mostly by diffusion. "The absorption to back-scattering ration for clouds is smaller and therefore the pre-dominant influence on solar radiation is back reflection." (Wells 1997). "The quantitative influence of clouds on solar radiation is dependent on solar elevation, the thickness of the cloud, the size and distribution and amount of liquid water in the cloud." (Wells 1997) Stratocumulus clouds are the most common clouds found over oceans ranging from 200-400 meters thick; when clouds are 400 m thick, they obliterate the sun’s disc.
Charlson’s original idea in 1987 was that ocean waters would be heated by greenhouse gases and would encourage algal production. He and his associates hypothesized that an increase in DMS would increase the sulphate aerosol and would therefore increase cloud formation and albedo, which would reduce global temperature, marine algal productivity and DMS emissions. The more algae, the more DMS produced and hence, more cloud formation (see Chart I for visual explanation of our atmosphere).
Oceans: Carbon Storage
Oceans absorb the largest fraction of solar radiation on Earth because of their great area and low albedo. They are prominent in determining temperature, wind and precipitation patterns over the globe. They do have a low net primary production (NPP) due to lack of nitrogen and iron. Seventy percent of the Earth’s surface is covered with oceans, so because of their large surface area, they have the highest NPP of any ecosystem on the planet. Over 90 percent of the carbon fixed by photosynthesis is consumed by herbivores. Researchers have a good idea about how much carbon dioxide is being released into the atmosphere each year by calculating how much fossil fuels are being consumed. Since 1958, only about half of the C02 known to be produced by fossil fuel consumption has shown up in the atmosphere; the oceans, mostly in the deep layers are absorbing the rest. The ocean is in essence a large storage area for carbon. Most of the carbon is transported to continental slope regions adjacent to the continental shelves. Oceans warm and cool more slowly than land, so no one knows the exact magnitude of global warming. "Scientists are concerned over several potential positive feedback mechanisms. Warmer oceans could be less efficient absorbers Of C02; they could release tons of methane (a greenhouse-effect trace gas) stored in the sea floor mud; or they could, through evaporation, release more water vapor to the air." (Bernard 1993)
The C02 concentration of the atmosphere has been increasing dramatically at about 1.5 parts per million annually. Like Charlson, Phillips, et al. suggested that "if the application of a nutrient subsidy could enhance phytoplankton productivity such that 10 percent of the open ocean NPP is buried in deep sea sediments, then 2 gigatons of carbon per year could be removed to mitigate the greenhouse effect." (Phillips 1992)
The Effects of Increased Temperatures on Algae
Dale and Swartman (1984) conducted studies at Lake Ontario showing that algae are more productive in warmer surface water temperatures. When temperature is increased, phytoplankton growth increases up to a certain point. Species with a higher optimal temperature also tend to have a higher rate of photosynthesis at that temperature. Photosynthesis is a complex process that involves light reactions with chorophyll that splits water into its components. Carbon dioxide is then reduced to carbohydrates. Cellular processes help carbohydrates to build macromolecules.
Evidence from their experiments shows that increased temperature affects grazing by altering the maximum ration available to the zooplankton for consumption. Phytoplankton surviving warming temperatures and periods of heavy grazing are probably able to respond fairly quickly to extreme conditions.
Phytoplankton serve as condensation nuclei for cloud formation. Condensation nuclei means the presence of particles in the atmosphere which provide surfaces for condensation. There are fewer condensation nuclei over the ocean than land. Clouds reflect the solar energy and lower the Earth’s temperature. Increased planetary albedo (the ratio of the reflected (scattered) solar radiation to the incident solar radiation measured above the atmosphere) may also contribute to cooling the planet. The problem with this idea is that ice cores from the Arctic and the Antarctic provide contradictory evidence. In 1991, researchers found the concentrations of sulphate aerosols derived from DMS and methane sulphonic acid (MSA) are lower during warm interglacial phases and higher during the ice ages. Scientists have come up with various explanations for why this experiment does not fit the theory from different ecologies favoring algal species that produce more DMS, changes in atmospheric circulation influencing the amount of aerosol material deposited, to an increase of salinity of the oceans. Algae may have produced more DMSP as a response to salt stress. There is no one answer because of the many variables involved.
"Geritol Solution": Iron Fertilization
One solution to global warming is more commonly known as the "Geritol solution." The plan consisted of dumping hundreds of thousands of tons of iron into the world’s oceans to stimulate the growth of phytoplankton. Phytoplankton consumes carbon dioxide, like most plants that carry out photosynthesis. (Bernard 1993) Is this feasible?
John Martin of Moss Landing Marine Laboratories in California explored this possibility. He found that algal growth is limited by lack of iron. Martin’s experiments showed that when iron is added to water samples, biological activity increases by about ten times. The ice core samples supported this idea by showing that an increase in iron is linked with a decrease in carbon dioxide. "You give me half a tanker full of iron; I’ll give you another ice age," John Martin said. (Bernard 1993) Experiments were still being held in October of 1993 to see how ecosystems would be affected. However, the chances of this being used to slow global warming are remote. Sherwood Rowland of the University of California at Irvine said in late 1991, "Nothing proposed yet is even remotely feasible." (Bernard 1993) Kenneth Johnson agrees with Rowland. "I think the chances of using this method to control C02 in the atmosphere are very remote." He adds that the emphasis must remain on C02 production. "To control greenhouse warming we need to reduce C02 production." (Bernard 1993)
Bernard emphasizes that people are the only answer to stop global warming. "No, an Ice Age won’t save us from a greenhouse world. No, technology and science aren’t the answer. People are. You and me. You and me and the actions we take or don’t take are going to determine our environmental future." (Bernard 1993)
Global Warming: Our Future
The Earth is getting warmer. The question is whether it will continue this trend or not and if increased algae blooms don’t help, what will? The last decade had nine out of the eleven hottest years of the century. 1997 was the hottest year since record keeping began, with the global average temperature being 62.45 degrees Fahrenheit. This is three-fourths of a degree higher than normal.
NASA has created a climate model to help with our understanding of global warming in the future. The model is based on all the laws of physics. The NASA model "computes cloud amounts and heights, models evaporation, includes the seasonal and daily distribution of solar heating’, calculates soil moisture and surface albedo (reflectivity) based on local vegetation, computes snow depth and albedo, and models convection. Convection is the vertical movement of heat through the atmosphere; among other things, convection produces rain showers and thunderstorms." (Bernard 1993)
The distinguishing factor that makes the NASA model superior to other models is "its ability to inject C02 and trace gases into the model atmosphere in a realistic, timephased fashion. " (Bernard 1993) The NASA model provides us with maps, pictures and a good idea of what our climate will be like in the 1990s, 2000s and 201 Os. The only downfall with this model is that it is primitive in simulating the interactions between the atmosphere and oceans. It is hard for any model to accurately portray this natural interaction because there is still so much to learn about it.
Scientists developed three greenhouse-effect scenarios for the NASA model. The first one (A) assumes C02 levels and trace gases will continue to grow annually, increasing more each year. The second one (B) assumes growth rates decrease slightly each year, implying a reduction in per capita emissions. However, population still increases. Volcanic eruptions are randomly placed in the years 1995, 2015 and 2025. Researchers were curious to see if these eruptions might affect the overall atmospheric temperature trends, since volcanic smoke absorbs solar radiation and in essence cools the planet. The third one (C) assumes fossil fuels are cut drastically between 1990 and 2000 and CFC’s are terminated in 2000. It has the same volcanic eruptions as scenario B (see attached chart 2 for graph results).
NASA researchers feel scenario B is the most likely to occur, but it might be closer to an in-between stage of A and B. The chart shows that by the beginning of the second decade of the next century, scenario A will reach 2.7 degrees Fahrenheit, while under scenario B it would be 2 degrees Fahrenheit. It may not seem like a lot but just a small change in temperature will drastically affect their climate and ecosystems.
The model is also capable of creating pictures or maps at any time (decade or season) in the future of what our climate may be like. "The model shows a greater degree of warming taking place over continental areas than over oceans and more warming occurring in the high latitudes (polar regions) than in low latitudes (tropical regions)." (Bernard 1993) The model concludes that there will be likely no "cooling" areas left in the world after the 1990s.
Conclusion
The fact remains that no one has come up with a permanent solution to global warming. Many people are still in denial that it even exists. That does not mean we should give up hope and keep filling our atmosphere with harmful fossils fuels, sulfur, aerosols and carbon dioxide. It means we have to start somewhere, and if it is with science and technology, then at least that is a start. We all have to play a part in altering global warming because we all are a part of this planet. Algae to do their part by photosynthesis and absorbing carbon dioxide; we can do ours by limiting our use of CFC’s and fossil fuels.
Our atmosphere with clouds has been our lifeline to all life on this planet. Why are we abusing it? It plays an important role in shielding us from harmful ultra-violet light, solar radiation, modulating precipitation and regulating carbon dioxide, water vapor and aerosols. The more pollution we pump into our atmosphere, the higher we are at risk for destroying our fragile shell of air.
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