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- Geology & Atmospheric Science
The Wrong Name: Global Warming
Proceedings of the National Academy of Sciences of the United States of America looked at the publication and citation data of climate researchers who were most actively publishing in the field. They found that 97-98% of these climate researchers support the tenet of anthropogenic climate change. 1 With most topics there are usually people found on opposite sides of an issue and climate change is no stranger to debate. Even though a majority of climate scientists agree that man has impacted the climate one must first understand how the weather works before taking a definitive stand.
Many people think the Earth is heated directly by the sun but it's a little more complicated than that. Clouds, water, ice, trees, and asphalt all have different reflective properties. When you're standing in a field of snow on a sunny day you're most likely digging for sunglasses if you don't already have them on. If you happen to be in the the woods or in the desert the longing for sunglasses isn't as great. There is a term called albedo which assigns a number to the reflective properties of things found on earth. Objects with a high degree of reflectivity (ice, snow, and water) are assigned higher numbers. Dark objects such as rocks and asphalt are given lower numbers because they absorb most of the incoming short wave radiation from the sun. Direct sunlight that is absorbed by darker objects, short wave radiation, is converted to long wave radiation and emitted into the atmosphere as heat. To put it simply would you rather walk barefoot across the grass or the asphalt during the summer?
Have you ever noticed that mornings are warmer when the night sky was full of clouds? Atmospheric gases such as carbon dioxide (CO2), water vapor (H2O), methane (CH4), and Nitrous Oxides (NOx) form the protective blanket that keeps our planet warm. Without these gasses the heat reflected from the ground would return to space leaving our planet extremely cold. Yes, we need greenhouse gases, but too many of them prevent radiant heat from escaping our planet.
How Many Greenhouse Gas Emissions did the U.S. Release in 2010?
Focusing on Carbon Dioxide:
The Keeling curve on the right shows the measured levels of CO2 at Mauna Loa. Looking at the blue box in the top corner may not seem like a big deal. However, when it is added to historical data of carbon dioxide levels in the atmosphere you will see it is actually a vertical line. Those who oppose global warming typically argue that the Earth has always had warming and cooling trends. That is correct, but if you look at the graph of past temperatures you will see the planet would warm and then immediately begin to cool. Looking at the most recent data our current temperature spike is a vertical line; it isn't falling like it has in the past.
When it comes to understanding the weather most people know that warm air rises and cool air sinks. The Earth's rotation causes low pressure systems to spin clockwise and high pressure systems to spin counterclockwise in the northern hemisphere. In the southern hemisphere they spin in the opposite direction. This phenomenon is called the Coriolis effect. Whenever air rises or sinks wind is created by the adjacent system moving in to fill the void. The figure below shows the alternating high and low pressure belts that surround the earth. Sub-polar lows are found near the north and south pole, moving towards the equator there are subtropical highs, and the low pressure band at the equator is called the inter-tropical convergence zone. As the seasons change due to an increase or decrease in solar radiation these pressure bands shift. The inter-tropical convergence zone moves toward whichever pole is experiencing summer.
What will happen when the shifts are no longer predictable constants? As glaciers and polar ice caps begin to melt the amount of incoming solar radiation reflected will decrease. When forests are replaced with asphalt and concrete the albedo will drop and the area will radiate more heat. The monsoon and drought seasons in Africa and India are the result of these shifting pressure bands.
Our current agricultural system was developed over the past 11,000 years, however that climate is changing. A study conducted by University of Wisconsin-Madison and the University of Wyoming predicts that many current climate zones will disappear by 2100.2 Food inflation is expected to average 9% through 2012.3 Looking at the graph on the right the number of undernourished people worldwide was beginning to decline, however it is beginning to rise again due to droughts and floods in agricultural areas.
With so much evidence that the planet is warmer and the impact it is having on our ecosystem, why is global warming a debated issue? The Earth is 75% water. What happens when water, a greenhouse gas, is heated? It evaporates. Some scientists still argue global warming is not an issue because an increase in global evaporation will produce more cloud cover. Clouds reflect incoming solar radiation and therefore should reduce the amount of heat generated by the Earth's surface. On the flip side, clouds insulate the heat radiated and prevent it from returning to space. The weatherman's best guess rarely extends beyond 10 days and no one is absolutely certain what the future climate on Earth will be. However, there is quite a bit of data out there showing the planet is warmer and it's not cooling off. So far global warming, which should be called, global climate change, has produced unusual weather patterns. In 2011 thousands of acres of farm land in Missouri were flooded by record rainfall and melting snow. The mid-western US was devastated by a string of catastrophic tornadoes, and Texas experienced a severe drought which later prompted wildfires.
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- Monsoons and Local Winds
The monsoon is a system of winds in which the direction of the winds is reversed between the summer and the winter season. Local winds owe their characteristics to the local topography or the local temperature conditions.