ENVS 101 1st Edition Lecture 23 Outline of Last Lecture I. Evidence of Climatic ChangeII. Why Climates ChangeOutline of Current Lecture II. Why Climates ChangeCurrent LecturePrecession of the equinoxes: The direction Earth’s axis points moves in a circle. This process changes the season when Earth is closest to the sun (right now we are closest during our winter season). This procession has a time period of around 23,000 years.External causes are too small to account for the average global temperature changes. The variations that occur must be amplified by internal feedbacks.- A change that occurs in one of Earth’s subsystems will end up causing another change ina different subsystem as a result. The change may become amplified as it moves through positive feedbacks, or diminished by negative feedbacks by contrast. - Internal causes of climatic change: Greenhouse effect (changes in CO2, methane CH4, and water vapor. Climate trends for the last 100 million years will generally match up with CO2 trends.As oceans warm, carbon dioxide is released from solution and vice versa: This is a positive feedback effect. Ocean warming can also release frozen gas hydrates CH4: This is a positive feedback effect. Ocean warming enhances evaporation: This also leads to a positive feedback effect. As permafrost melts old dead plant material decays, releasing CO2: Another positive feedback.The tectonic cycle largely controls the rate of CO2 buildup in the atmosphere. - Through seafloor spreading, subduction, and volcanism. Through chemical weathering ofsurface rock exposed in mountain ranges(which removes CO2). Carbonate deposition in ocean (shells, corals, etc.) also remove carbon from atmosphere.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Anthropogenic causes of climate change: Within the past two centuries since the Industrial Revolution, atmospheric CO2 has risen at a rate faster than at any time in the past 100,000 years. - Humans pump roughly 8 billion metric tons of carbon, mostly as CO2 into the atmosphere every year from fossil fuel use alone.Internal causes of climatic change: Albedo and dust (from volcanoes, dry winds or human influences) can block incoming solar radiation.Younger Dryas: Melt from glaciers at the end of the last glaciation disrupts ocean currents, sending Europe into a “deep freeze” because the warm water of the Atlantic was blocked of for a period of
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