Climate Change Midterm 1

Climate Change Midterm 1 - Lecture 0 What is climate? o...

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Lecture 0 What is climate? o Weather is the condition of the atmosphere at a particular location and moment. o A region’s climate is the ‘average’ seasonal behavior of a number of weather elements(climate variables) including: Temperature Moisture (snow, rainfall, fog) Wind Distinctive regional weather patterns (monsoons, hurricanes) o There is no agreed-upon list of climate variables that totally define all possible climate conditions around the World. We can estimate important climate variables by comparing seasonal weather patterns in different regions How Do We Define ‘Average’ Climate? o Regional weather and environmental conditions vary slightly from year to year. o So, how many years are needed to define the ‘average’ climate for a region? o We normally pick an arbitrary length of ~50 years over which to define climate ‘average’. Is the Earth’s Climate Constant? o The only thing constant about the Earth’s climate is that it is constantly changing ! o Climate changes occur on timescales of decades to millions of years. o This course seeks to understand what climate changes have occurred before in Earth history and to assess what climate changes we can expect in the next 100 years or so. We will study Climate Change from the perspective of Earth System Science o Cause and Effect in Earth System Science o Earth systems interact with one another. Changes in one will cause effects in the others. We normally think of the causes as ‘forcing ’ and the effects as ‘responses ’. o One question is how long a response will take to occur given some forcing? Some responses to forcing are fast and others are slow. o When the various Earth systems are balanced, we refer to this as equilibrium . Feedbacks in Earth System Science o In some cases forcing will cause a response, which, in turn, will cause another response.
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o Positive feedbacks are processes in Earth Systems, which tend to accentuate or amplify an initial forcing. As climate gets warmer in polar regions it melts the ice and snow, this reduces the albedo, ice and snow reflect more Sunlight that land and water. This causes the Arctic Ice Cover to melt and the climate to get warmer. o Negative feedbacks are process in Earth Systems, which tend to lessen or diminish an initial forcing. Example: As climate gets warmer in the Tropics, there is more water evaporation and cloud formation. Clouds have high albedo and tend to reflect more sunlight back into space without heating the Earth. This causes climate to get cooler. Lecture 1 Why does climate change matter? Climate changes have affected humans throughout history. And before that, they have affected biotic systems from the  time life began, billions of years ago. The problem has been that we didn’t appreciate that such changes were occurring.  Now we know they can occur and significantly affect our lives. But, we do not yet understand climate well enough to 
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Climate Change Midterm 1 - Lecture 0 What is climate? o...

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