Think about what drives the climate system A) Identify the three ‘knobs, for lon

Question

Think about what drives the climate system A) Identify the three ‘knobs, for long-term climate-ie, what are the three things that when their values change will cause the long-term climate change. For each, provide a physical/chemical process within the Earth System (or Solar System) that can change the value. (3 points) B) Identify which of the three knobs from A) could be altered by anthropogenic factors. For each, provide an example for how human activities can alter the value of this knob. If any of the three knobs from A) cannot be altered by humans, briefly discuss why. (3 points) C) Chose two of the climate changes listed below. For each climate change event, briefly describe the event and some of its defining characteristics. Additionally, identify the driving mechanism(s) of the change. In many cases, the climate change is increased by associated feedbacks. Make sure to identify any of the key feedbacks for that event. (9 points total - 4.5 points for each event) List of Climate Change Events Cenozoic Cooling Paleocene-Eocene Thermal Maximum Quaternary Glacial-Interglacial Cycles Younger Drays Event Little Ice Age

Explanation / Answer

C) (i) Little Ice Age: A period between AD 1300 and 1850 with regionally cold conditions. There was no single, well-defined period of prolonged cold, so this term, Little Ice Age is somewhat doubtful. There were two phases of the Little Ice Age, the first beginning around 1290 and continuing until the late 1400s. There was a slightly warmer period in the 1500s, after which the climate deteriorated substantially, with the coldest period between 1645 and 1715. During this phase, there are indications that average winter temperatures in Europe and North America were as much as 2°C lower than at present. The exact cause of the Little Ice Age is unknown, but it is said that the cause of Little Ice Age was that the earth does not have some magical average natural temperature to which it always returns. If it warms, the earth must be receiving more heat or retaining more heat. If it cools, then it must be receiving less heat from the Sun or radiating more into space, or both. There is a striking coincidence in the sunspot cycle and the timing of the Little Ice Age. During this event, there is a minimum in sunspots, indicating an inactive and possibly cooler sun. This absence of sunspots is called the Maunder Minimum, which was occurred during the coldest period of the Little Ice Age between 1645 and 1715 AD.

(ii) Younger dryas event: A climatic event occured from c. 12,900 to c. 11,700 years ago. It was the most recent and longest of several interruptions to the gradual warming of the Earth's climate since the severe Last Glacial Maximum, c. 27,000 to 24,000 calendar years BP. Its effects were complex and variable. The change was relatively sudden, taking place in decades, and it resulted in a decline of 2 to 6 degrees Celsius and advances of glaciers and drier conditions, over much of the temperate northern hemisphere. It is thought to have been caused by a decline in the strength of the Atlantic meridional overturning circulation, which transports warm water from the Equator towards the North Pole, in turn thought to have been caused by an influx of fresh cold water from North America to the Atlantic.The Younger Dryas is the youngest and longest of three stadials, which resulted from typically abrupt climatic changes that took place over the last 16,000 calendar years.

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