Changes in global energy balance

• The global energy balance is the balance between income solar (short wave) radiation coming from the sun and outgoing infrared (long wave) radiation from the earth. This helps to regulate the earth's climate.
• The sun emits short wave radiation, some of which is reflected and absorbed by clouds and the atmosphere.
• Most of the incoming solar radiation is absorbed by the earth's surface, with a small portion being reflected by the earth's surface.
• The radiation that has been absorbed by the earth's surface is converted into long wave infrared radiation, which is emitted by the earth's surface.
• The outgoing long wave energy from the earth's surface is mostly reabsorbed by the atmosphere and re-emitted back into space.
• Some of the long wave radiation is absorbed by the greenhouse gases in the atmosphere which re-emit the radiation back to earth.
• The earth's surface temperature increases as it absorbs this radiation.
• A positive feedback loop is a mechanism in which a change in the system will lead to an increase in the change, thus amplifying the system.
• An example of a positive feedback loop is ice and snow albedo feedback.
• Albedo refers to the amount of incoming solar energy that is reflected by the earths surface back to the atmosphere.
• Ice and snow have high albedo, meaning that they reflect a lot of the incoming solar radiation.
• More permafrost melts, which causes more methane to be released into the atmosphere.
• The release of methane may lead to an increase in the amount of long-wave radiation that is trapped and absorbed by greenhouse gases, thus increasing global temperatures.
• As the earth's temperatures increase, due to green house gases trapping heat that is radiated from the earth's surface, the area of snow cover on the earth's surface decreases.
• Permafrost contains large amounts of methane.
• Ocean and land surfaces have a lower albedo, meaning that they reflect less of the incoming solar radiation.
• As global temperatures rise, permafrost is likely to melt.
• As more ocean and land surfaces become exposed, more incoming solar radiation is absorbed by the earth, which contributes to continued and accelerated warming.
• As ice melts, it releases methane, a greenhouse gas, into the atmosphere.
• A negative feedback loop is a mechanism that brings a system back to equilibrium.
• If a change occurs in the system, it may lead to other changes however the system will be brought back to the way it was before the changes have occured.
• Evaporation and clouds are an example of a negative feedback loop.
• As the surface temperature of the earth increases, as a result of greenhouse gases released from human activities, there are increased levels of evaporation from the oceans.
• The increase in evaporation results in more clouds forming in the lower atmosphere.
• These clouds reflect some incoming solar radiation back into space, thus decreasing the earth's surface temperature as less heat is absorbed.
• If a change occurs in the system, it may lead to other changes however the system will be brought back to the way it was before the changes have occured.
• Data collected over the past several years suggest that global temperatures have fluctuated over time.
• The total amount of solar radiation reaching the earth can vary due to changes in the sun's output, the presence of aerosol particles in the atmosphere and changes in the earth's orbit.
• Global dimming refers to a reduction in the amount of incoming solar energy received from the sun, resulting from an increase in the presence of aerosol particles in the atmosphere, which is caused by pollution, dust and volcanic eruptions.
• These particulates act as condensation nuclei for water droplets that form clouds.
• The droplets in clouds formed due to global dimming are more numerous and smaller than droplets in natural clouds, and they reflect more sunlight.
• This prevents some sunlight from reaching the earth's surface and thereby reduces some of the impact of the enhanced greenhouse effect.
• The eruption of Mount Pinatubo, in the Phillipines in 1991 caused a dip in global temperatures in the early 1990s.
• Sunspots are small dark spots on the surface of the sun that emit high amounts of solar output.
• The presence of sunspots can raise global temperatures and their absence may decrease temperatures.
• Variations in the tilt and/or orbit of the Earth around the sun lead to different parts of the earth getting more or less sunlight.
• The angle of tilt on the Earth's axis changes over a 41,000 year cycle.
• This causes more or less sunlight to reach the poles.
• Earth's orbit around the sun varies between a perfect sphere and an ellipse.
• When Earth's orbit is an ellipse, less sunlight reaches the earth at certain points in its orbit, cooling the climate.