EGEE 102
Energy Conservation and Environmental Protection

What is Likely but Uncertain: Factors affecting temperature

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Some factors that affect the Earth's temperatures include clouds, fine particles, and oceans.

Clouds

  • Low, thick clouds primarily reflect solar radiation and cool the surface of the Earth.
  • High, thin clouds primarily transmit incoming solar radiation; at the same time, they trap some of the outgoing infrared radiation emitted by the Earth and radiate it back downward, thereby warming the surface of the Earth.
  • Whether a given cloud will heat or cool the surface depends on several factors, including the cloud's height, its size, and the make-up of the particles that form the cloud.
  • The balance between the cooling and warming actions of clouds is very close - although, overall, cooling predominates.

Fine Particles (aerosols) in the atmosphere

The amount of fine particles or aerosols in the air has a direct effect on the amount of solar radiation hitting the Earth's surface. Aerosols may have significant local or regional impact on temperature.

Atmospheric factors shown in the image below include natural factors such as clouds, volcanic eruptions, natural biomass (forest) burning, and dust from storms. In addition, human-induced factors such as biomass burning (forest and agricultural fires) and sulfate aerosols from burning coal add tiny particles that contribute to cooling. Please watch the following 2:41 presentation: "The Cooling Factors."

Fine Particles in the atmosphere
Click Here For Transcript of Cooling Factors

There are several factors that have an influence on the earth's climatic change. Some of these happen to be clouds, fine particles, et cetera. Low, thick clouds primarily reflect solar radiation and cool the surface of the earth. High, thin clouds primarily transmit incoming solar radiation. At the same time, they trap some of the outgoing infrared radiation emitted by the earth's surface and radiate it back downward, thereby warming the surface of the earth. Whether a given cloud will heat or cool the surface depends on several factors, including the cloud's height, size, and the make of the particles that form the cloud. there in the atmosphere also change. As we talked about, the fine particles are coming into the atmosphere from volcanic eruptions, for example, or biomass burning, including natural forest fires, and also dust from the storms, sandstorms, et cetera. And we have very fine sulfate aerosols from burning coal and oil that come into the atmosphere. And these fine particles sometimes contribute to cooling. This is well known. For example, when Mount Pinatubo erupted in Philippines in 1991, there were a lot of fine particles that were spewed into the atmosphere which covered the surface, and it caused, basically, cooling. So again, at this point we do not know exactly how these factors will affect in future. Forest fires release carbon dioxide into the atmosphere, and, as we all know, carbon dioxide traps heat. And volcanic eruptions, these particles can cool sometimes-- oceans, clouds. And prediction of these kinds of things for future is a difficult task, and that is the reason predicting what is likely to happen is not so certain at this point in time.

Source: United Nations Development Program/ GRID – Arendal (reproduced with permission)

When Mount Pinatubo erupted in the Philippines in 1991, an estimated 20 million tons of sulfur dioxide and ash particles blasted more than 12 miles high into the atmosphere. The eruption caused widespread destruction and human causalities. Gases and solids injected into the stratosphere circled the globe for three weeks.

Volcanic eruptions of this magnitude can impact global climate, reducing the amount of solar radiation reaching the Earth's surface, lowering temperatures in the troposphere, and changing atmospheric circulation patterns. The extent to which this occurs is an uncertainty.

Below is a picture of Mount Pinatubo next to a map of its location and how far the ash from its eruption spread.

Image 1. Mount Pinatubo erupting. Image 2. Map of its location and how far the ash from its eruption spread.
Image 1. Mount Pinatubo erupting. Image 2. Map of its location and how far the ash from its eruption spread.
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Water vapor is a greenhouse gas, but at the same time, the upper white surface of clouds reflects solar radiation back into space. Albedo—reflections of solar radiation from surfaces on the Earth—creates difficulties in exact calculations. If, for example, the polar icecap melts, the albedo will be significantly reduced. Open water absorbs heat, while white ice and snow reflect it.

Oceans

Oceans play a vital role in the energy balance of the Earth. It is known that the top 10 feet of the oceans can hold as much of the heat as the entire atmosphere above the surface. However, most of the incoming energy is incident on the equatorial region.

The water in the oceans in the equatorial regions is warmer and needs to be transported to the northern latitudes. This is done due to natural variations in the temperatures of the water and prevailing winds that cause the disturbances in the surface waters.

The Intergovernmental Panel on Climate Change (IPCC) states that even the low end of this warming projection "would probably be greater than any seen in the last 10,000 years, but the actual annual to decadal changes would include considerable natural variability."

Instructions: Click the play button to learn about the Ocean Conveyor Belt in the 2:52 presentation:

Ocean Conveyor Belt
Click Here for Transcript of Ocean Conveyor Belt Video

Oceans play a vital role in the energy balance of the earth. It is established that the top 10 feet of the oceans, which is roughly 3 meters, can hold as much of the heat as the entire atmosphere above the surface. However, most of the incoming energy is incident in the equatorial regions where the water gets warmer. And the water in these regions is much, much warmer compared to the water near the polar regions. And this warm water in the equatorial region needs to be transported to the northern latitudes. And this upper-layer water is not so rich in nutrients, whereas under the ocean it is rich in nutrients. Generally, this transportation is done due to natural variations in the temperature of the water, prevailing winds that cause the disturbances in the surface waters. The cold and dense water, from the polar regions basically, flows into the ocean, sinks to the bottom, and, pushing the warm waters from the surface, move towards the, again, northern latitudes. So this basically establishes a kind of oceanic conveyor belt. Warm, salty water is chilled when it is sinking in the northern Atlantic and it flows southwards towards Antarctica. And this is cooled further at the bottom of the oceans into Atlantic, Indian, and Pacific basins. The water returns to the surface, again primarily in Pacific and Indian Oceans, and again it comes back to the surface and goes to the northern Atlantic. While traveling deep in the ocean, the originally nutrient-depleted water becomes increasingly enriched by organic matter decomposition in the important nutrients, particularly phosphates, nitrates, and silicates. And that's how this is a very, very important process here in transporting the CO2 and the heat that is available to the surface water. So this oceanic conveyor belt plays a very important role in the heat distribution.