Global Warming, or the warming of the Earth's temperature over a period of time, is, contrary to popular belief, not caused by man, but instead by solar radiation, through the direct heating of the Earth and through the indirect consequence of a change in cloud formation. Data and analysis that has been published in peer-reviewed scientific journals, such as Astronomy and Geophysics and Physics Today, show that solar radiation has a direct link to the warming or cooling of the Earth, and a change in the radiation may directly cause a change in the temperature of the Earth. Examples of solar radiation are present in such examples as the Little Ice Age, where the Earth cooled considerably due to a decrease in radiation. In addition, some scientists believe that the link between carbon dioxide and global temperature increase is not as significant as other scientists claim it to be.
In this paper, there are many terms that need to be defined for comprehension. NASA is the National Aeronautics and Space Administration, an executive agency of the United States government responsible for scientific research involving aeronautics and aerospace. Carbon dioxide is a colorless, odorless chemical that is a gas at room temperature with the chemical formula of CO2. A greenhouse gas is a gas in the atmosphere that contains the radiation that is reflected back towards space from the Earth, an example of which is carbon dioxide. TSI, or total solar irradiance, is the sum of all the radiation that the sun emits at a specific point in time. Correlation used statistically means how one set of data follows another set of data's trends. The correlation of two sets of data can have a range from -1, which means a perfect negative correlation, to 1, which means a perfect positive correlation ("correlation"). Finally, Albedo is the measure of a substance's reflectivity. A high albedo means that the substance is more reflective than a low albedo.
What Global Warming Is Global warming is the increase in the average surface temperature of the Earth. This warming can cause ice cap melting in the polar regions of the Earth, a change in wind and precipitation patterns, as well a change in the growing seasons, which can cause damage to many ecosystems (“Global Warming”). There are many sides to the debate on this topic, including whether the phenomenon is truly occurring or not, and if it is, what it is caused by. The phenomenon, according to data from NASA, is real, based on temperature readings from the past 120 years that show an increase of approximately .6 degrees Celsius from the mean temperature between 1951 and 1980 ("Main"). Some scientists say that the amount of warming is even greater, around 1 degree Celsius (“Global Warming"). However, the debate on what the warming shown by the data is caused by is still ongoing, with many people subscribing to the theory that the increase in manmade carbon dioxide in the atmosphere is to blame.
Why Carbon Dioxide is not to Blame
Many government agencies, such as NASA and the IPCC, the Intergovernmental Panel on Climate Change, believe that the causes of global warming to be the increased amount of greenhouse gases in the atmosphere, mainly carbon dioxide, or CO2, which has been pumped into the atmosphere from sources such as factories and automobiles ("Global Warming"). This theory relies on the fact that because greenhouse gases trap infrared radiation that has been reflected by the Earth. The trapped radiation then would heat Earth, increasing the surface temperature. However, according to Cynthia A. Bily in an article about global warming, carbon dioxide is not the strongest greenhouse gas, and in fact, does not even account for 5% of the effects of greenhouse gases. The strongest greenhouse gas is water vapor, which accounts for 95% of the warming effect. There are also other greenhouse gases, such as methane, which in addition to the carbon dioxide, contribute the remaining 5%. In addition to the fact that carbondioxide is a weak greenhouse gas, she goes on to say that .035% of the atmosphere is composed of carbon dioxide and that 97% of the carbon dioxide on Earth is naturally made, and not from human emissions (“Global Warming Is”). If the percentage of carbon dioxide in the atmosphere is multiplied with the percentage emitted by humans (3%), the result, .105%, is the percentage of carbon dioxide in the atmosphere that was emitted by humans. According to data from the Department of Geology at the University of Georgia, water vapor can make up anywhere from .004% to 4% of the atmosphere (Railsback). As stated above, only .035% of the atmosphere is carbon dioxide. If the105% man made carbon dioxide is factored in, the result of .03675% is the percentage of manmade carbon dioxide that is in the atmosphere. This result is between the range of the percentage of water vapor in the atmosphere, and closer to the lower bound, showing that there is usually more water vapor in the air than carbon dioxide that was produced by humans. In addition, water vapor is a much stronger greenhouse gas, and if the amount of carbon dioxide made by humans is less than the amount of water vapor on average, then manmade carbon dioxide clearly is not the most important factor in the warming of the Earth.
The Role of the Sun in Warming the Earth
The solar constant is a misnomer that scientists have termed the total amount of radiation that is given off by the Sun. The term “solar constant” is a misnomer because the radiation that is given off by the Sun is not actually a constant number, and should therefore be called "solar variability.” This is proven by recent data that shows an average variance in solar radiation of . 2%, or about two watts per meter squared. Using current data, scientists have linked the solar radiation levels to the amount of sunspots there are on the Sun. They have found that the fewer sunspots there are at a specific point in time, the less radiation that is given off by the Sun. Using this knowledge, a trend developed that showed that approximately every eleven years, the Sun goes through a cycle in the number of sunspots (“Solar”). A team led by Ilya Usoskin of the University of Oulu in Finland has discovered that even though there is a cycle of the number of sunspots, the number of total sunspots has been increasing for the past 50 years (Behreandt). Since the amount of sunspots has been increasing, the relationship between sunspots and solar radiation means that the amount of radiation has also been increasing. Eigel Friis-Christiensen and Henrik Svensmark, a pair of scientists, wrote in the peer-reviewed journal Advances in Space Research that the correlation between the total solar irradiance and the surface temperature in North America is .86 (Friis-Christiensen and Svensmark). This value for a correlation is fairly high, which means that the temperature data follows the trend that the TSI data set closely. Since solar radiation has increased over the past 50 years, and the data has shown that an increase in solar radiation leads to higher surface temperatures, the chance that the warming that has been recorded over the past decades is due to the increase in solar radiation is very probable.
Further evidence that supports this fact comes from findings by a group of Dutch and German researchers that found a certain isotope of carbon that is less prevalent when there is more solar radiation than when there is less radiation. They compared levels of the isotope from ice cores, which contain air bubbles that have kept a small sample of the atmosphere from when the ice solidified, to temperature records and simulations and have determined an inverse relationship between the two sets of data (Behreandt). An inverse relationship means that as the carbon isotope is increasing, and the temperature is decreasing, or vice versa. Since the carbon isotope also has an inverse relationship with solar radiation, the data shows that temperature following the same trend as solar radiation.
The Little Ice Age and Its Implications
Most scientists say that the temperature now is the highest it has been for the past couple centuries (“Solar”). This is true because they do not take into account the time frame before the Little Ice Age, which was a time frame approximately 400-600 years ago in the 1400s-1600s when the temperature dropped between 1 and 1.5 degrees Celsius during a Maunder Minimum, which is a minimum in solar irradiance (Shindell et al). At the end of the Little Ice Age, the temperature was about .4 degrees Celsius colder than the mean temperature between 1951 and 1980, and now it is about .6 degrees Celsius warmer (“Main”). That means that the temperature has a net increase of 1 degree Celsius since the Little Ice Age. Because the temperature decreased between 1 degree and 1.5 degrees Celsius during this time period, the increase of 1 degree since then shows the Earth's temperature is rising back up to what it was before the Little Ice Age began.
The relationship between the Maunder Minimum and the drop in temperature during the Little Ice Age shows that solar radiation can play a large role on the Earth in cooling it down when there is less radiation. Because this statement has been proven true by the data, the opposite of the statement, that more radiation would play a significant role in warming the Earth, is also true.
Solar Radiation, Cloud Cover, and the Role of Clouds
Clouds, depending on the type, can either warm or cool the Earth. Low clouds have a cooling effect on the Earth, because they are larger in volume than high clouds, and have a larger albedo, a measure of reflectivity. On the contrary, high clouds have a lower albedo, so they allow for more radiation to pass through. Clouds can also work in a way that is similar to the greenhouse gases, reflecting infrared radiation back towards Earth (Pallé Bagó and Butler). Satellite data has shown a 3% decrease in cloud cover between the solar minimum in 1987 and the maximum in 1990. This decrease was mainly in the amount of lower clouds, and not higher clouds (Friis-Christiensen and Svensmark). This means that a higher irradiance would cause a higher concentration of high clouds over low clouds. Since there were less low clouds, there was a smaller albedo, and more radiation was able to reach the surface of the Earth during the solar maximum.
The 3% decrease in cloud cover is the equivalent of an increase of 1 to 1.5 watts per meter squared in radiation. During the same time frame, the change in the amount of radiation was .1%, which would be approximately .25 watts per meter squared more in radiation. The change in cloud cover allowed for between four and six times as much radiation change as solar radiation alone (Friis-Christiensen and Svensmark). This shows that cloud cover can impact the temperature of Earth by a substantial amount, because if cloud cover is reduced, like during a solar maximum, the amount of radiation introduced can be amplified, thereby increasing the surface temperature of the Earth.
The Ice Albedo Effect
Current data has shown that the solar radiation has been decreasing recently, but global temperatures seem to still be increasing. Many scientists consider this to be evidence that solar radiation could not be causing global warming (Connor). However, this interpretation of the data may not be true. According to NASA, during the winter of 2008, the polar ice caps only covered 30% of the area in the Arctic, compared to the 50-60% that the caps used to cover (Cole and Renfrow). This decrease from 50-60% to 30% shows that the ice caps covering the Arctic have lost about half of the ice they used to hold. Just like clouds, ice also has albedo. Because it is able to reflect so much radiation, ice's albedo is extremely high. Due to of the drop in ice levels, the albedo of the area has decreased along with the amount of ice. This means that less solar radiation can be reflected back into space by the ice. Due to this process occurring, less solar radiation is then needed to warm the Earth, because more of the solar radiation is kept within the Earth's atmosphere, and less is reflected back out into space. Furthermore, since less radiation is needed to warm the Earth, the decreasing amount of radiation emitted by the Sun may still cause the surface temperature to rise.
This process of the melting of the ice creates a feedback loop, where the higher temperatures caused by a high amount of solar radiation melts the ice. The ice then can reflect back less radiation, making the amount of radiation needed to increase temperatures less. This means that when radiation decreases, the radiation is still able to raise temperatures. As the temperatures keep increasing, the ice will keep melting, making the amount of radiation needed to increase the temperature decrease further. Because of this feedback loop, any data that shows that the solar radiation is decreasing, but the temperatures are still increasing, may not be as valid as scientists suggest it to be.
The data that many scientists use as evidence for the greenhouse gas explanation of global warming do not tell the whole story. The truth is, carbon dioxide is not a very strong greenhouse gas, and the amounts of the gas in context with the entire of the atmosphere are very small. A more likely scenario for the warming of the Earth is through solar radiation. The amount of solar radiation can vary, which has been statistically shown to cause the variance in the surface temperatures on Earth. Scientists have evidence that shows the solar irradiance has increased, which would increase the temperature of Earth. This, in concert with the increase in the concentration of high clouds over low clouds, has been shown using statistics to have a high correlation with the increase in temperature. Also, even though the levels of solar radiation may have dropped, the temperature is still increasing. This is because as the temperatures have increased, the levels of ice have dropped, lowering the albedo of the Earth. This means that less solar radiation is needed to achieve the same amount of warming. Global warming is caused mainly by the consequences, both indirect and direct, of solar radiation, and not by the increase in manmade carbon emissions.