1. What was different about Earth 55-50 million years ago, that generated a subt
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Question
1. What was different about Earth 55-50 million years ago, that generated a subtropical climate in the region that would become the Pacific Northwest? Be sure to describe the rate of change that occurred to change from the subtropical climate to the present day climate.
2. How does carbon dioxide (CO2) gas in the atmosphere generate short term (10’s-1000’s of years) climate change, that is, short enough for the change to occur during the present ice age?
3. How does a tropical disturbance, tropical depression, and tropical storm relate the formation of a hurricane in the Atlantic Ocean? Use an Atlantic hurricane that eventually makes landfall along the shores of North Carolina.
Explanation / Answer
1. The climate of Earth was different during the Eocene period that dates back to 55-50 million years ago. Warm, wet conditions prevailed and the temperature gradient between equator and pole was small due to which the Pacific Northwest of today warmed substantially. The present-day climate is relatively cooler and drier as the rate of change in climate was altered rapidly due to highly fluctuating periods of glacials and interglacials throughout the Cenozoic.
2. The input of CO2 to the atmosphere initiates a positive feedback as the temperature on the Earth's surface is amplified with changing orientation of Earth's axis relative to the path of incident solar radiation. The transformation to glacial (ice-age) period to an interglacial (ice-free and warm) period was regulated due to the greenhouse effect induced by CO2 gas. Such a gas is stored and released in quick succession when the surface temperature shifts from cold to warm. With changing cycles of such shifts on orbital timescales (up to 100,000 years), the positive feedback of CO2 gas plays an important role in increasing the temperature of Earth as the gas, once released in the atmosphere, remains there for tens to hundreds of years.
3. Hurricanes originate in the Atlantic Ocean as a tropical disturbance over the vicinity of West Africa at tropical or subtropical latitudes. With increasing input of thermal energy from the ocean and changing atmospheric conditions (mid-tropospheric relative humidity, low vertical wind shear, and surface pressure) in the horizontal and vertical directions, a tropical disturbance evolves into a depression, storm and eventually a hurricane.
North Carolina was a victim of Hurricane Fran as it made a landfall there on 6th September 1996. On 22nd August 1996, a tropical depression in the form of a wave moved from Africa's west coast and intensified into a tropical storm on 26th August. By September 4th, it was a category-3 hurricane and finally made its landfall in North Carolina nearby Cape Fear on September 6th.
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