Net Radiation Budget <ul><li>Not all incoming solar radiation is absorbed on Earth. </li></ul><ul><li>The difference between the amount of incoming radiation and the amount of outgoing radiation is called the net radiation budget </li></ul>
<ul><li>Of the incoming solar radiation, 31% is immediately reflected back into space by clouds, the atmosphere and Earth’s land surface. </li></ul>
<ul><li>Approximately 30% of the remaining solar radiation is absorbed by the atmosphere . </li></ul>
<ul><li>The remaining solar radiation warms Earth’s surface . This heat is returned to the atmosphere as infrared radiation. </li></ul>
<ul><li>Less than 1% of incoming solar radiation is transformed by photosynthesis into chemical energy. </li></ul>
<ul><li>Almost all of the energy absorbed by Earth’s atmosphere, lithosphere and hydrosphere is eventually radiated back into space as infrared radiation. </li></ul>
Net Radiation Budget On average, the amount of incoming radiation is equal to the amount of outgoing radiation for all of planet Earth. Word equation : net radiation budget = (incoming radiation) - (outgoing radiation) = 0
Net Radiation Budget If this balance were to change , the average global temperature would either increase or decrease until the net radiation budget was balanced again.
Thermal Energy Transfer Radiation = the emission of energy as waves When radiant energy encounters particles of matter, it may be reflected or absorbed . Absorbed energy can increase the temperature of the matter.
Thermal Energy Transfer Conduction = the transfer of thermal energy through direct contact. Usually takes place in solids . Particles with high kinetic energy transfer some of this energy to particles with lower kinetic energy, causing an increase in temperature .
Thermal Energy Transfer Convection = the transfer of thermal energy through the movement of particles from one location to another. Usually occurs in fluids (liquids and gases). Movement of particles forms a current .
Greenhouse Gases Recall that the natural greenhouse effect keeps our planet warm by absorbing some of the infrared radiation from Earth’s surface
Greenhouse Gases The natural greenhouse effect is due mainly to the presence of water vapour , carbon dioxide , methane and other naturally occurring greenhouse gases in our atmosphere.
However, these gases are also produced by human activities, such as industry , electricity generation, transportation and agriculture.
Greenhouse Gases <ul><li>The four main greenhouse gases are: </li></ul><ul><li>Water vapour </li></ul><ul><li>Carbon dioxide </li></ul><ul><li>Methane </li></ul><ul><li>Nitrous oxide </li></ul>
Greenhouse Gases Global warming potential is a measure of the ability of a gas to trap thermal energy in the atmosphere over a specified period of time .
Greenhouse Gases Climatologists have given carbon dioxide a global warming potential rating of 1 , and other greenhouse gases are rated relative to carbon dioxide.
Greenhouse Gases Water vapour is not included in the global warming potential classification because its concentration varies with temperature .
Greenhouse Gases Persistence is the length of time the gas remains in the atmosphere. Gases that persist longer can absorb thermal energy over a longer period of time.
Greenhouse Gases Persistence of carbon dioxide is not defined because it depends on the amount emitted and the capacity of carbon sinks .
Measuring Greenhouse Gases Some of the best data on atmospheric greenhouse gas concentrations comes from the Greenland Ice Core Project (GRIP)
Measuring Greenhouse Gases Glaciers are made of snow that turned to ice under the pressure of later snowfalls.
Each year’s snowfall is recorded as a distinct layer . While the ice layer at the surface was formed the previous winter, at its deepest the ice core is though to be 200,000 years old.
Measuring Greenhouse Gases Ancient ice can be read like a history book. It contains tiny bubbles , which have preserved the atmosphere’s gases at the time that particular ice was formed .
Scientists can slice out a layer of the core , melt it, and analyze the gas concentrations in the bubbles .
The ice core data show that the concentration of CO 2 in the atmosphere fluctuated between 180 ppm and 300 ppm during the glacial and interglacial periods (10,000 years ago).
Then, for the last 10,000 years CO 2 concentrations remained stable around 280 ppm .
Around the time when the Industrial Revolution started, CO 2 concentrations began to increase rapidly from 280 ppm to the present level of 385 ppm .
Measuring Using this ice core data, climatologists have concluded that the concentrations of other greenhouse gases in the atmosphere have also increased since the 1700s . Greenhouse Gases
Scientists have shown that the increase in greenhouse gas concentrations is a direct result of changes in human activity.
Before the Industrial Revolution, humans depended on manual labour , animal energy, wind power and water power to do work and produce goods .
During the Industrial Revolution, the focus shifted rapidly to coal-fired steam engines and the mass-production of goods.
Human society became more and more dependent on the consumption of fossil fuels . As a result, more and more greenhouse gases were emitted.
Since greenhouse gases absorb heat, changes in their atmospheric concentrations can unbalance the net radiation budget of Earth.
Measuring Greenhouse Gases Increased greenhouse gas concentrations mean that less thermal energy is released back into space .
Measuring Greenhouse Gases As a result, the average temperature at the Earth’s surface increases .
Measuring Greenhouse Gases Recall that the natural greenhouse effect keeps Earth at a livable average temperature.
However, the additional greenhouse gas emissions are causing the anthropogenic greenhouse effect. anthropogenic greenhouse effect = an enhancement of the natural greenhouse effect due to human activities
Tree Rings Recording growth is one way to document change. The growth of a tree is documented in the widths of its rings .
Tree Rings One tree ring is formed every year , during the summer when the tree grows.
Tree Rings Thicker rings mean that the tree grew closer to its optimal range of conditions - i.e. enough precipitation and appropriate temperatures .
Tree Rings Thin rings mean that the tree grew near the boundaries of its tolerance range - i.e. low precipitation/ drought or temperatures that are too high/too low.
Tree Rings By comparing the rings , scientists can determine the weather conditions over the life of the tree.
Tree Rings Since some trees live for hundreds of years, the rings provide long-term climate data.