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The Student News Site of Stony Brook University

The Statesman

The Student News Site of Stony Brook University

The Statesman


    Deconstructing the Theories of Global Warming

    With average global temperatures on the rise, many scientists are still looking for the cause for modern day climate changes, hopefully before any serious effects occur.

    A common idea is that the increase in greenhouse gas emissions due to human activity has caused most of the warming observed since the 1990’s. These greenhouse gases reflect outbound infrared radiation (heat energy) back toward the earth’s surface rather than letting it escape into space, thus causing surface air temperature to rise.

    Since the Industrial Revolution, the amount of carbon dioxide in the air has increased from the approximate 260 parts per million (ppm) evidenced by core samples of glacial ice to the 383 ppm measured in January 2007. According to studies performed by the Intergovernmental Panel on Climate Change, even doubling what seems like a small about of carbon dioxide in our atmosphere can raise the average temperature up to 8.1 degrees Fahrenheit and humidity by 20 percent.

    Carbon dioxide, however, is only one of the many substances considered to be greenhouse gases, such as methane and chlorofluorocarbons, the latter of which never existed naturally. An increased concentration in any of these could have similar effects.

    Another thought is that pollution is depleting the ozone layer, a layer of various configurations of oxygen molecules in the stratosphere that protects us from a specific type of radiation from the sun, known as UVB rays. As the ozone is depleted, the increased radiation can cause rises in surface air temperatures. This radiation is also known to cause skin cancer and damage to plants and plankton, the basis of many ecosystems.

    Despite all of this information, scientists are still far from the answer.

    The presence of the atmospheric pollution could counteract its own warming effect through a phenomenon called “global dimming.” The idea says that the particles in the air can reflect incoming sunlight, preventing it from striking the surface of the earth and making the sun seem dimmer, reducing the amount of light reaching Earth and therefore reducing surface air temperatures.

    Efforts to reduce air pollution could have reduced their countering effect, leading to a faster rise in surface temperatures. A National Aeronautics and Space Administration report on this layer of airborne particles, called aerosols, says that “the thinning of Earth’s ‘sunscreen’ of aerosols since the early 1990’s could have given an extra push to the rise in global surface temperatures.”

    “When more sunlight can get through the atmosphere and warm Earth’s surface, you’re going to have an effect on climate and temperature,” said Michael Mishchenko from NASA’s Goddard Institute for Space Studies, also known as GISS, in a NASA article. “Knowing what aerosols are doing globally gives us an important missing piece of the big picture of the forces at work on climate.”

    Satellite estimates have shown a steady decrease in sun-blocking aerosols since the eruption of Mount Pinatubo in 1991, which caused a 10 percent reduction in the amount of sunlight reaching the earth’s surface, and by consequence a global temperature reduction of 0.7 degrees Fahrenheit.

    The NASA report later says, “The combined results from nine state-of-the-art climate models, including three from GISS, showed that due to increasing greenhouse gases and aerosols, the planet warmed at the same time that direct solar radiation reaching the surface decreased,” which means that although less sunlight is reaching Earth’s surface, our climate is still warming.

    This could be attributed to the idea that, even though the aerosols are reflecting light, they are still absorbing radiation from the sun and releasing it in the stratosphere.

    Because of these two contradictory circumstances, the effects of climate change have not been as apparent as scientists would have predicted. “Less sunlight reaching the surface counteracts the effect of warmer air temperatures, so evaporation does not change very much,” said Gavin Schmidt, also from NASA’s GISS, in the article. “Increased aerosols probably slowed the expected change in the hydrological cycle.”

    Unfortunately, scientists lack quantitative data for the effects of the small but steady decline in aerosols, and presently only have measurements of the spacial thickness of the aerosol layers.

    In addition to global dimming, the cause of climate change is further obscured by the solar cycle of the sun.

    In a NASA study, scientists found that during times of “quiet” sunspot activity, the amount of solar radiation has increased by nearly .05 percent per decade since the 1970’s. Sunspots are regions on the surface of our sun that experience intense electromagnetic activity and therefore lower temperatures, making them appear as dark “spots.”

    “Historical records of solar activity indicate that solar radiation has been increasing since the late 19th century,” said Richard Willson, a scientist affiliated with NASA’s GISS and Columbia University’s Earth Institute, in a separate article by NASA. “If a trend, comparable to the one found in this study, persisted throughout the 20th century, it would have provided a significant component of the global warming the IPCC reports to have occurred over the past 100 years.”

    Still, some claim that records of data have been distorted, and that the earth is still in a cooling phase, or that there is not enough evidence to prove that the changes aren’t natural.

    Any number or combination thereof could be the cause of the climate change we are experiencing today, and will be experiencing tomorrow.

    The IPCC projects that over the course of the 21st century, the average surface air temperature will rise by 3.2 to 7.2 degrees Fahrenheit, but unevenly distributed around the world.

    Stony Brook’s campus hasn’t been affected much by the climate change in terms of temperature and precipitation, having the same average yearly temperature and nearly the same amount of precipitation in 2008 as in 1992, but rises elsewhere have the potential to affect the entire globe.

    According to the IPCC, an increase in the average global temperature is very likely to lead to changes in precipitation and atmospheric moisture because of changes in atmospheric circulation and increases in evaporation and water vapor. Precipitation events, from rain showers to thunderstorms, would be expected to increase in intensity, along with the overall precipitation amount, but during summer seasons there would be limited rain inland due to increased evaporation.

    It would also be expected that tropical storms and hurricanes increase in intensity and wind speed as they would be energized by warmer sea surface temperatures, according to a World Meteorological Organization study from 2006.

    In addition to weather changes, the global average sea level is estimated to rise by 7.2 to 23.6 inches by the end of the century, as reported by the IPCC.

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