S c i e n c e Energy and the Earth Key words: Incoming Solar Radiation, Electromagnetic wave, Greenhouse effect, conduction, convection, radiation.
Energy transfer Heat is energy in transit from warmer systems to colder systems Heat can be transferred from warmed systems by Conduction, Convection or Radiation (electromagnetic radiation). Radiation consists of photons and waves, the same as visible light.
Energy transfer CONDUCTION: It is the flow of heat through solids and liquids by vibration and collision of molecules. The molecules with a higher movement (warmer system) collide with the less energized molecules (colder system) and transfer part of their energy. Metals are the best thermal conductors; while non-metals are poor thermal conductors CONVECTION: Flow of heat through currents within a fluid (liquid or gas). Convection is the displacement of volumes of a substance in a liquid or gaseous phase. When a mass of a fluid is heated up, its molecules are carried away causing that the mass of that fluid becomes less dense. For this reason, the warmed mass will rise, while the colder and denser mass of fluid goes down. RADIATION: It is heat transfer through vacuum by electromagnetic waves (or photons). It does not need a propagating medium. The energy transferred by radiation moves at the speed of light. The heat radiated by the Sun can be exchanged between the solar surface and the Earth's surface without heating the transitional space.
Energy transfer Once the energy has been emitted and reaches a surface, it can be absorbed or reflected by an object. ELECTROMAGNETIC RADIATION REFLECTION ABSORPTION The factors that can affect how an object can absorb or reflect energy are: COLOR - dark objects absorb energy better than white colored ones SURFACE TEXTURE - smooth objects reflect more than rough ones CHEMICAL PROPERTIES - different composition gives different reflectivity
Temperature and Heat Temperature is a measure of the intensity of hotness in a body. The heat held in an object depends not only on its temperature but also its mass. For example, lets compare the heating of two different masses of water (see table below). In this example, one mass has a weight of 5 grams, while the other is 25 grams. To rise the temperature of both masses from 20 to 25 C, the larger mass of water will require five times more heat energy. This larger mass would also contain 5 times more stored heat energy. Heat energy required to raise two different quantities of water 5 Celsius. Mass of the Water Starting Temperature Ending Temperature Heat Required Mass 1 5 grams 20 Celsius 25 Celsius 25 Calories Mass 2 25 grams 20 Celsius 25 Celsius 125 Calories
Temperature Scale A number of measurement scales have been invented to measure temperature. The table beside describes important temperatures for the three dominant scales in use today The Fahrenheit system is used exclusively in the USA and was created by Gabriel Fahrenheit in 1714. He set the lower limit of this scale to the lowest temperature he could find outside and the upper end as his body temperature. The most commonly used scale for measuring temperature is the Celsius system. It was developed in 1742 by the Swedish astronomer Anders Celsius. In this system, the melting point of ice was given a value of 0, the boiling point of water a value of 100, and absolute zero a value of -273. The Kelvin scale was proposed by British physicist Lord Kelvin in 1848. This system is often used by scientists because its temperature readings begin at ABSOLUTE ZERO (at this point all motions of molecules cease). The Kelvin scale assigns a value of 273 for the melting temperature of ice, while the boiling point of water occurs at 373. Temperature of absolute zero, the ice point of water, and the stream point of water using various temperature measurement scales Measurement Steam Point Ice Point Absolute Zero Fahrenheit 212 32-460 Celsius 100 0-273 Kelvin 373 273 0
Energy and the Earth: the Solar Radiation
Energy and the Earth: the Solar Radiation 1 second wavelength λ 4 s 1 (4 Hz) Wavelength (λ) The distance between two points on a wave in the same phase (as peak). Is usually measured in m (or nm) The relationship between frequency (ν, measured in Hz) and wavelength is: c = λ ν Speed of light 3 10 8 m/s [ν] = Hz = s -1 Despite differences in wavelengths, all electromagnetic radiation travels at the same speed in a vacuum. This value, the speed of light, is a constant Exercise: calculate the FM radio waves wavelength of your favorite radio station (e.g.: Lifegate radio: 89,90 MHz)
Energy and the Earth: the Solar Radiation ph 1 second wavelength λ 4 s 1 (4 Hz) We can consider light as composed of particles called photons. Those particles transport energy. Thus, to every photon is associated Energy. This energy depends on the wavelength (so on the frequency) E = h ν Energy of a photon h = Planck constant = 6,63 10-34
Energy and the Earth: the Solar Radiation wavelength (nm) 10 2 10 0 10 2 10 4 10 6 10 8 10 10 10 12 gamma ray x-ray ultraviolet Infrared infrared microwave radio frequency - rays visible 10 20 10 18 14 10 10 10 16 10 14 10 12 10 10 10 12 10 8 10 6 10 4 frequency (s 1 ) 400 500 600 700 750 nm visible light region Humans are able to see some wavelengths of light, the wavelengths known as visible light. These wavelengths appear to us as colors. The longest wavelengths of visible light appear red ( 750nm) and the shortest wavelengths appear violet ( 400nm). Wavelengths that are longer are infrared (IR). Snakes can see infrared energy but we can record this with special equipment.
Global Climate Change The Earth's climate has changed throughout history. In the last 650.000 years there have been seven glacial cycles, with the end of the last ice age about 7.000 years ago marking the beginning of the modern climate era.
Global Climate Change Most of these climate changes are attributed to very small variations in Earth s orbit that change the amount of solar energy our planet receives. Those cycles are named Milankovitch Cycles, named after Serbian geophysicist and astronomer Milutin Milanković. Milanković mathematically theorized that variations in axial tilt and precession of the Earth's orbit determined climatic patterns on Earth. ε = obliquity (axial tilt) Q day = calculated daily-averaged insolation on summer solstice at 65 N latitude Benthic forams and Vostok ice core show two distinct paths for sea level and temperature, from ocean sediment and Antarctic ice respectively. Vertical gray line is current conditions, at 2 ky A.D.
Global Climate Change Most of these climate changes are attributed to very small variations in Earth s orbit that change the amount of solar energy our planet receives.
Global Climate Change The current warming trend is of particular significance because most of it is very likely human-induced and proceeding at a rate that is unprecedented in the past 1,300 years. Certain facts about Earth's climate are not in dispute: The heat-trapping nature of carbon dioxide and other gases was demonstrated in the 19 th century. Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many researches. Increased levels of greenhouse gases must cause the Earth to warm in response.
Energy and the Earth: the Solar Radiation Radiation About 30% of the incoming solar radiation is reflected (by clouds, air and dust) back to the space. H2O CO 2 CH4 CFC The energy absorbed by the Earth surface is then reradiated back as a long wavelength, such as IR Convection Roughly 70% of the ISR reaches the Earth. A portion of this (the IR component) is absorbed by clouds, greenhouse gases and lands. Half of the total ISR is absorbed by the crust. Conduction
Energy and the Earth: the Greenhouse effect Some gases in the atmosphere (such as H2O and CO2) absorb most of the Earth's emitted long-wave IR radiation These IR radiations heat the lower atmosphere. The warmed atmosphere then emits back longwave radiations, keeping the temperature of our planet stable as in a greenhouse. These process is know as Greenhouse effect and is natural effect A greenhouse gas (sometimes abbreviated GHG) is a gas that absorbs and emits radiation within the thermal infrared range
Energy and the Earth: the Greenhouse effect Increasing concentrations of greenhouse gases such as carbon dioxide (CO2) and methane (CH4) increase the temperature of the lower atmosphere, resulting in "global warming," or, more broadly, global climate change Gas Formula Concentration ppb Contribution (%) Water Vapor H2O 10 000 000 36-72 % Carbon Dioxide CO2 360 000 9-26 % Methane CH4 1750 4-9 % Principal source Sea water evaporation, Volcanic emission, Fossil fuel combustion Fossil fuel combustion, Municipal waste combustion, Cement manufacture, Volcanic emissions, Deforestation Fossil fuel combustion, Cattle digestion, paddy fields, Volcanic emissions Nitrous oxide NO2 285 3-7 % Agriculture, Transports, Volcanoes, Industry In order, the most abundant greenhouse gases in Earth's atmosphere are: water vapor, carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons The contribution to the greenhouse effect by a gas is affected by both the characteristics of the gas and its abundance.
Global Climate Change CO2 is released through natural processes such as respiration and volcano eruptions and through human activities such as deforestation, land use changes, and burning fossil fuels. Humans have increased atmospheric CO2 concentration by a third since the Industrial Revolution began. This is the most important long-lived "forcing" of climate change.
10000 km Composition of the Atmosphere 700 km InfraRed Visible light UV-rays X-rays 80 km 50 km 8-18 km Ozone layer T The lowest level, the Troposphere, starts from the Earth s surface. Is about 8 km at poles and 18 km at the equator. The temperature gradually decreases to about -55 C, where the Stratosphere starts. Here the temperature rises to about 0 C 50 km above the Earth s surface. The temperature then falls to -90 C in the Mesosphere at around 80 km. The Thermosphere is the uppermost layer of the atmosphere and the temperature rises. Because the air is dry, the temperature can rise until 100 C. -90 C 0 C 20 C 50 C 100 C
Composition of the Atmosphere Most of the Atmosphere (more or less 78%) is composed of nitrogen (N2). In addition 21% is oxygen (O2). The remaining 1% is composed of Argon (Ar), Carbon Dioxide (CO2) and other gases. 99% of the atmosphere is found within the Earth surface and 32 km above. O2 21% Other particles found in the Atmosphere include Water Vapor (H2O), Ozone (O3) and dust. N2 78% Ozone is found at 10 to 50 km above the Earth s surface and is very important to life. It absorbs UV radiation (short-wave radiation). The dust found in the atmosphere is made from rock and mineral particles (aerosol), pollen, sea salt (marine spry), pollutants and bacteria. These dust particles can provide a surface for condensation of water vapor.
CO2 in the Atmosphere
CH4 in the Atmosphere
The Carbon Cycle
Climate changes