6.3A - Atmospheric Carbon
The concentration of atmospheric carbon (carbon dioxide and methane) strongly influences the natural greenhouse effect, which in turn determines the distribution of temperature and precipitation.
A fully functioning and balanced carbon cycle is vital to the health of the Earth in sustaining its other systems. It plays a key role in regulating the Earth's temperature by controlling the amount of carbon dioxide in the atmosphere. This, in turn, affects the hydrological cycle. Ecosystems, terrestrial and oceanic , also depend upon the carbon cycle. All this is a consequence of the fact that the carbon cycle provides the all-important link between the atmosphere, hydrosphere, lithosphere and biosphere. But the carbon balance is being increasingly altered by human actions.
The greenhouse effect
It is the increasingly concentration of carbon in the atmosphere that is causing great concern. Carbon dioxide and methane are perhaps the most important of all the greenhouse gases (GHGs). Their increasing presence in the atmosphere in the atmosphere is upsetting the Earth's natural temperature-control system, resulting in the greenhouse effect.
The greenhouse effect:
The Earth's climate is driven by incoming short-wave solar radiation:
It is this trapped, re-radiated, long-wave energy that constitutes the natural greenhouse effect and controls the mean global temperature. It also determines the distributions of both heat and precipitation. (HOW??? WHY???)
The greenhouse effect:
- Incoming solar radiation 343 Watt per m²
- Solar radiation passes through the clear atmosphere. Net incoming solar radiation: 240 Watt per m²
- Solar energy is absorbed by the Earth's surface and warms it. 168 Watt per m²
- Some solar radiation is reflected by the atmosphere and Earth's surface. Outgoing solar radiation: 103 Watt per m²
- Some of the infrared radiation passes through the atmosphere and is lost in space. Net outgoing infrared radiation 240 Watt per m²
- Some of the infrared radiation is absorbed and re-emitted by the greenhouse had molecules. The direct effect is the warming of the Earth's surface and the troposphere.
- Surface gains more heat and infrared radiation is emitted again.
- and is converted into heat causing the emissions of longwave (infrared) radiation back to the atmosphere.
- Surface gains more heat and infrared radiation is emitted again.
- Solar energy is absorbed by the Earth's surface and warms it. 168 Watt per m²
The Earth's climate is driven by incoming short-wave solar radiation:
- 31% is reflected back into space by clouds, GHGs and by the land surface
- the remaining 69% is absorbed at the Earth's surface, especially by the oceans
- much of this radiation absorbed at the surface is re-radiated as long wave radiation
- large amounts of this long-wave radiation are, however, prevented from returning into space by clouds and GHGs
- the trapped long-wave radiation is then re-radiated back to the Earth's surface
It is this trapped, re-radiated, long-wave energy that constitutes the natural greenhouse effect and controls the mean global temperature. It also determines the distributions of both heat and precipitation. (HOW??? WHY???)