Why Is the Earth Warming? The Greenhouse Effect Explained

If you remember one thing: Earth warms until energy in = energy out — greenhouse gases slow the “heat out”.

When the Sun warms Earth by day, where does that heat go at night — and why doesn’t it all escape to space? Today: the greenhouse effect, explained calmly and simply.

🐾 Belle’s Question

“Why doesn’t all the Sun’s heat just bounce back into space?”

🌍 The big idea (explained simply)

Sunlight mostly comes in as visible light. Earth mostly sends energy back out as infrared heat. Greenhouse gases (CO₂, methane, water vapour) absorb and re-emit some of that outgoing infrared, which slows heat escaping to space — so the surface warms until it reaches a new balance. Adding more greenhouse gas thickens the “blanket.”

🌱 One Bright Thing (with links)

• Stockholm Wood City: https://www.al.se/en/sickla/

• White Arkitekter overview: https://whitearkitekter.com/news/kvarter-7-the-starting-point-for-the-unique-stockholm-wood-city/

• Wonderwoods, Utrecht: https://wonderwoods.com/en/2025/02/14/wonderwoods-officially-opened-a-green-icon-for-utrecht/

• Rodney Cook Sr. Park: https://www.tpl.org/our-work/cook-park

• “Sponge city” explainer: https://www.preventionweb.net/news/sponge-city-how-san-salvador-using-nature-fight-floods

🏫 Quick quiz (for families & classrooms)

• Sun’s energy comes in mostly as what — and Earth sends energy out mostly as what?

• Why is “CO₂ is only 0.04%” not a good argument that it can’t matter?

🔔 Follow & Ask Belle

If this helped, follow The Climate Classroom on Spotify or Apple — it means the next school-run episode arrives automatically. And if you’ve got a question for Belle, send it on Spotify, or at www.theclimateclassroom.org — with “the” at the start.

————— READ MORE / FULL NOTES —————

🎧 In this episode

• Earth’s temperature is an “in and out” energy balance (like a bath: tap + plug)

• Sunlight warms the surface; the warm surface gives off infrared (heat radiation)

• Greenhouse gases absorb and re-emit some infrared, including back down — like a blanket

• Why “a tiny amount” of CO₂ can still matter, and where water vapour fits in

• How we know this isn’t guesswork: lab physics, air measurements, and satellite “fingerprints”

📚 Sources & further reading (grouped)

Greenhouse effect basics

• NASA — “What is the greenhouse effect?”: https://science.nasa.gov/climate-change/faq/what-is-the-greenhouse-effect/

• UK Met Office — “Greenhouse gases” (shortwave/longwave explained): https://weather.metoffice.gov.uk/climate-change/greenhouse-gases

• The Royal Society — “Basics of climate change” (energy in/out, IR): https://royalsociety.org/news-resources/projects/climate-change-evidence-causes/basics-of-climate-change/

Shortwave vs longwave (“nerd note”)

• Penn State (EARTH 103) — Blackbody radiation + Wien’s Law: https://courses.ems.psu.edu/earth103/node/1001

• OpenStax — Blackbody radiation + Wien’s displacement law (clear explainer): https://openstax.org/books/university-physics-volume-3/pages/6-1-blackbody-radiation

Extra anchors (for grown-ups)

• NOAA (Keeling Curve): https://gml.noaa.gov/ccgg/trends/

• IPCC reports: https://www.ipcc.ch/reports/

• WMO climate updates: https://wmo.int/topics/climate