The Energy Budget and the Greenhouse Effect

1. National Aeronautics and Space Administration The Energy Budget and the Greenhouse Effect Dr. Lin H. Chambers, NASA Langley Research Center Hampton, Virginia NASA Climate Day Workshop, June 2012 www.nasa.gov

2. The Electromagnetic Spectrum http://mynasadata.larc.nasa.gov/ElectroMag.html

3. The Blackbody Spectrum – The Sun http://phet.colorado.edu/simulations/sims.php?sim=Blackbody_Spectrum

4. The Blackbody Spectrum – Light Bulb http://phet.colorado.edu/simulations/sims.php?sim=Blackbody_Spectrum

5. The Blackbody Spectrum – Light Bulb Note Scale Change! http://phet.colorado.edu/simulations/sims.php?sim=Blackbody_Spectrum

6. The Electromagnetic Spectrum Peak of Earth emission ~10 mm = 104 nm http://radiojove.gsfc.nasa.gov/education/educ/radio/tran-rec/exerc/iono.htm

7. The Earth’s Energy Budget http://mynasadata.larc.nasa.gov/preview_lesson.php?&passid=63

8. Balancing the Budget - I At the top of the atmosphere: + Sunlight In – Sunlight reflected from clouds/atmosphere – Sunlight reflected from surface – IR emission 0 Equilibrium Temperature: -18 °C http://mynasadata.larc.nasa.gov/preview_lesson.php?&passid=44

9. At the Earth’s surface: + Sunlight absorbed – IR emission + IR back radiation (greenhouse effect) – Thermals – Evapotranspiration 0 Balancing the Budget - II Equilibrium Temperature: 15 °C http://mynasadata.larc.nasa.gov/preview_lesson.php?&passid=63 http://mynasadata.larc.nasa.gov/preview_lesson.php?&passid=67

10. The Energy Budget - An Analogy Winter Summer Earth’s Energy Budget

11. Most of the energy on Earth comes to us from the Sun. Did you know?: The amount of sunlight that reaches the Earth is equal to approximately 6 60w light bulbs for every square meter of the surface.

12. We can sense that energy in different ways. We see the things around us because of visible light…

13. … And we feel the heat from a campfire, which is infrared energy.

14. NASA senses the different types of energy too with satellite instruments.

15. If all of these types of energy from the Sun are always shining down on Earth, how does the Earth manage to maintain the perfect balance of energy – or equilibrium – that allows us to live and survive on Earth? The Sun – hot though it is - is a tiny part of Earth’s environment.

16. If all of these types of energy from the Sun are always shining down on Earth, how does the Earth manage to maintain the perfect balance of energy – or equilibrium – that allows us to live and survive on Earth? The planet Mercury – too hot because it’s too very close to the Sun

17. If all of these types of energy from the Sun are always shining down on Earth, how does the Earth manage to maintain the perfect balance of energy – or equilibrium – that allows us to live and survive on Earth? The planet Mars – “too cold” because it is farther from the Sun and has a very thin atmosphere.

18. If all of these types of energy from the Sun are always shining down on Earth, how does the Earth manage to maintain the perfect balance of energy – or equilibrium – that allows us to live and survive on Earth? The planet Earth – just the right balance for life to survive and thrive.

19. Earth and all the planets stay at a stable temperature through their “Energy Budget.”

20. First, energy enters the atmosphere from the Sun.

21. Some of that energy reflects off of clouds, dust, and other particles and never makes it to Earth’s surface. Most of that energy, however, does get to the surface, and once it gets to us, the ground, trees, and everything else around us absorbs that heat.

22. However, there are some parts of Earth's surface that are highly reflective, like water or snow, so in addition to absorbing heat, the energy also bounces off of those surfaces and heads right back out into space.

23. All of that heat energy that is absorbed by the Earth doesn't just stay there and build up forever. The Earth system radiates that energy out towards space. Cold objects emit less energy; warm objects emit more.

24. A portion of the heat emitted from the surface is stopped on its way back out. Clouds and certain gases in the atmosphere absorb the energy, preventing it from leaving the system.

25. Energy emitted from those clouds and gases goes in all directions. Some comes back to further warm the Earth.

26. Together all of these forms of incoming and outgoing energy result in just the right living conditions for us on Earth.

27. Together all of these forms of incoming and outgoing energy result in just the right living conditions for us on Earth.

28. Like your house, anything that increases or decreases the amount of incoming or outgoing energy would disturb Earth’s energy balance and would cause global temperatures to rise or fall.

29. The Enhanced Greenhouse Effect Starting point: Earth at equilibrium with net energy input from the Sun. Average surface temperature 288 K (15 C; ~59 F)

30. The Enhanced Greenhouse Effect The experiment: Instantaneously double CO2 in concentration in atmosphere Average energy emitted by Earth drops 4 W/m2 (236 vs 240)

31. The Enhanced Greenhouse Effect Response: All other things being equal, simple blackbody theory says: Average surface temperature rises 1.2 K (or C; ~2.1 F) Energy back in balance

32. The Enhanced Greenhouse Effect Feedbacks: In Earth system, other processes kick in (water vapor feedback, cloud feedback, ice-albedo feedback, etc). Net effect: Average surface temperature estimated to rise 2-4.5 K (~3.6 to 8 F)

33. Energy Balance analysis • This figure depicts mostly positive and long-lived forcing agents from 1950 through 2004. The positive forcing agents are items that cause the atmosphere to show an overall warming trend because they trap additional energy in the atmosphere (enhanced greenhouse effect). The greenhouse gasses shown in the figure (carbon dioxide - CO2, methane - CH4, halocarbons, nitrous oxide - N2O and stratospheric + tropospheric ozone - O3) have increased in the atmosphere mostly due to human activities. A natural change from variations in the Sun’s output is shown along the bottom of the graph This figure shows the cumulative effect of small changes. The additional heat trapped each year continues to add up to a warmer Earth. http://science-edu.larc.nasa.gov/energy_budget/ Physics of Our Atmosphere

34. Where did the Energy Go? • Knowing how much additional heat is trapped (because we know how much of these gasses were emitted) the question becomes: where did the energy go? This figure partitions the added energy shown above based on observed changes. So far, a small amount of the energy has gone into warming the ocean – the part of the Earth that stores the most energy. Some has escaped Earth in the form of increased IR emission because of warmer temperatures. Some was reflected to space by aerosols (mostly volcanic in origin) in the stratosphere. The remainder (white band) is inferred to have been rejected due to aerosols (mostly pollution) in the troposphere, and other effects such as a changing reflection of the land surface due to deforestation, for example. http://science-edu.larc.nasa.gov/energy_budget/ Physics of Our Atmosphere

35. Interactive Applet http://profhorn.meteor.wisc.edu/wxwise/climate/makeplanet.html

36. SignOffPage MY NASA DATA: A REASoN Project