Lecture 16

Lecture 16 - SIO 40 Life and Climate on Earth Nov. 6th,...

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Unformatted text preview: SIO 40 Life and Climate on Earth Nov. 6th, 2009 Lecture 16 Climate Change Basics, Part I Components of the modern climate system, their processes and interactions Lecture Outline- Human vs. natural influences on climate- Uncertainty in climate science- The greenhouse effect and major greenhouse gases- Surface and atmospheric temperature observations- The Paleoclimate perspective- Recent climate scares- Modern warming is different Relative impacts of humans vs. nature on climate Natural impacts solar output, volcanic eruptions, Earths orbit Human impacts greenhouse gas emissions, aerosol emissions, ozone depletion, land use changes Review: Earths annual and global mean energy balance ver the long term, the amount of incoming solar radiation absorbed by the Earth and atmosphere is balanced by the Earth and atmosphere releasing the same amount of outgoing longwave radiation. About half of the incoming solar radiation is absorbed by the Earths surface. This energy is transferred to the atmosphere by warming the air in contact with the surface (thermals), by evapotranspiration and by longwave radiation that is absorbed by clouds nd greenhouse gases. The atmosphere in turn radiates longwave energy back to Earth as well as out to space. Radiative forcing of climate between 1750 and 2005 Radiative forcing factors change the balance between incoming solar radiation and outgoing infrared (longwave) radiation within the Earths atmosphere, thus affecting climate. Positive forcings lead to warming; negative forcings lead to cooling. It is apparent that forcing factors associated with human activity from the period 1750-2005 outweigh natural forcing factors, and are net positive. LOSU = level of scientific understanding Dealing with uncertainty in climate change science Uncertainty in climate science arises from a variety of sources, such as the unpredictable nature of the physical climate system and the human factors driving climate change, the simplifications necessary in computer models of climate, and incomplete knowledge about some important climate parameters that drive computer models.The IPCC 4 th Assessment Report uses a variety of constructs (eg. above) to try and define the level of uncertainty in scientific understanding of climate parameters, as well as climate projections. The principle of the greenhouse effect is one of the most well-understood parts of the climate system. Feedback loops and the greenhouse effect Increased CO 2 Global warming Increased water vapor...
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Lecture 16 - SIO 40 Life and Climate on Earth Nov. 6th,...

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