Lecture note No.1 GEOG, Slides of Geography

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• GEOG

GEOG

Instructor: Dr. Li, Jinbao Office: Room 1029, 10/F, The Jockey Club Tower Phone: 3917- 7101 Email: [email protected] Office hours: Tuesday 3:00-5:00 PM or upon appointment Research interests: Climate Change, Paleoclimate, Tree-rings, El Niño, Drought, Forest Ecology Students: 20 - 30 TA: Mr. Zhang, Xu Phone: 9041 - 3166 Email: [email protected]

Geosphere

• Extends from the surface to the center, with a depth of ~6400 km.
• Divided into three layers: Crust, Mantle and Core.
• Lithosphere: uppermost of geosphere that interacts with atmosphere, biosphere and hydrosphere.

Atmosphere •^ A gaseous envelope surrounding the Earth

• A very shallow layer compared to Geosphere
• Divided into four layers

Estimated residence time of water in different reservoirs

Short Medium Long

All lives on earth: 8.7 million 6.5 million on land, 2.2 million in the oceans Mora et al., 2011 PLOS Biology

Earth as a System

• A system is a group of interacting or interdependent parts that form a complex whole.
• The Earth System involves the intricate and continuous interaction between the lithosphere, hydrosphere, atmosphere, and biosphere.
• There are two primary sources of energy that power the Earth system:
• (1) solar energy that drives the external processes that occur at or above Earth's surface, and
• (2) Earth's interior heat that remains from when the planet formed and heat that is continuously generated by radioactive decay.

Composition of the Atmosphere

• Nitrogen and oxygen : 99%, important to life, but of little or no importance in affecting weather.
• Trace gases : only 1%, but are very important when considering weather, climate, and all sorts of environmental issues.

Aerosols

• Fine solid particles or liquid droplets suspended in the atmosphere.
• Sources: some natural, some anthropogenic

• Direct radiative forcing : Absorbing and/or scattering solar radiation and terrestrial radiation ( warming or cooling effect ).
• Indirect radiative forcing : Acting as surfaces on which water vapor may condense ( cloud condensation nuclei ), affecting cloud properties and climate.
• Cooling effect might be dominant (large uncertainty). Aerosols affect climate in two ways:

Why are aerosols important to climate studies? The agreement between models & obs. could be improved if aerosols are better considered in climate models.