--- marp: true theme: default html: true --- # What keeps Earth's temperature steady? Year 10 Earth and space · Earth's energy balance --- ## Today **We are learning to** earth is in energy balance when the energy it absorbs from the sun equals the energy it gives off to space as infrared. Energy moves between the spheres by radiation, conduction and convection, and the oceans store heat. Upset the balance and Earth warms or cools until it is restored. - I can explain what energy balance means. - I can explain how a temperature change restores the balance. - I can describe energy flows between spheres and the ocean's role as a store. --- ## Why it matters > In about an hour, the sun pours as much energy onto Earth as humanity uses in a year. Yet, year to year, Earth's average temperature barely changes. Where does it all go? --- 💬 Discussion ## Engage: predict **Earth absorbs sunlight all the time. Why doesn't it keep getting hotter and hotter?** - The energy is destroyed - The sun switches off at night everywhere - It does keep getting hotter, by the same amount each year - It gives off just as much energy to space, as infrared --- ✍️ Activity ## Explore it {{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-10%2Fenergy-balance%2Fstep-2&code=widget%3A+climate%0Amode%3A+balance%0A&fresh=1}} [Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-10/energy-balance/?full=step-2#step-2) --- ✅ Check ## What happened? * It gives off energy to space as infrared radiation. When the energy out equals the energy in, the temperature stays steady: energy balance. --- ✅ Check ## Balance **What does energy balance mean?** - Energy absorbed from the sun equals energy given off to space, over time - No energy is moving - Earth stores all the energy it receives - The sun and Earth are the same temperature * Answer: Energy absorbed from the sun equals energy given off to space, over time --- ✅ Check ## Restored **After you increased the sunlight, why did the temperature stop rising?** - The sunlight ran out - The ocean got full - A warmer surface gives off more infrared, until energy out matched energy in again - The warmer Earth reflected more of the sunlight * Answer: A warmer surface gives off more infrared, until energy out matched energy in again --- ✅ Check ## How energy moves **Match each energy flow to how it moves.** | | | |---|---| | `Sunlight reaching the surface` | A. Radiation (infrared) | | `Infrared leaving Earth for space` | B. Radiation (visible light) | | `Warm air rising from hot ground` | C. Convection | | `Heat passing from warm ground into the air touching it` | D. Conduction | * Answer: Sunlight reaching the surface → B. Radiation (visible light); Infrared leaving Earth for space → A. Radiation (infrared); Warm air rising from hot ground → C. Convection; Heat passing from warm ground into the air touching it → D. Conduction --- ✅ Check ## Elaborate: the ocean as a store **Why does Earth take decades, not days, to reach a new balance after a change?** - Infrared is slow - Sunlight takes years to arrive - Nothing changes for 50 years - The oceans can store a huge amount of heat, so they warm slowly * Answer: The oceans can store a huge amount of heat, so they warm slowly --- ✅ Check ## Elaborate: moving heat around **Western Europe is much milder than parts of Canada at the same latitude. What helps explain it?** - Europe has more greenhouse gases - Europe is closer to the sun - Canada has no sunlight in winter - Warm ocean currents carry heat from the tropics across the Atlantic * Answer: Warm ocean currents carry heat from the tropics across the Atlantic --- ## Evaluate: look back Write one sentence: "At first I thought… Now I think… because…" **Revision summary** - **Energy balance:** energy absorbed from the sun = energy given off to space as infrared, over time. Then temperature is steady. - Upset it (more in or less out) and Earth warms or cools until **out = in** again. - Energy moves between the spheres by **radiation, conduction and convection**; the **oceans store** heat and carry it around the world. --- ✅ Check ## Exit ticket **What is energy balance, and what happens if more energy comes in than goes out?** * Energy in equals energy out over time. If more comes in, Earth warms until it gives off enough extra infrared to balance again.