🌍 The Science of Climate Change

What you’ll learn

1. The Greenhouse EffectUnderstand how greenhouse gases trap outgoing infrared radiation and why the natural greenhouse effect is essential for life.Sunlight warms Earth's surface, which radiates heat back as infrared. Certain gases, carbon dioxide, methane, water vapor, absorb that infrared and re-radiate part of it downward. Without this effect Earth would average about minus 18 degrees Celsius; the concern is that humans are strengthening it.
2. The Carbon CycleTrace how carbon moves between the atmosphere, oceans, land, and rocks, and why burning fossil fuels disrupts a long-balanced system.Carbon constantly cycles among reservoirs and stayed near 280 ppm for millennia. Burning fossil fuels releases ancient carbon far faster than oceans and forests can reabsorb it. Those sinks soak up about half our emissions, but at the cost of ocean acidification, and CO2 lingers for centuries.
3. Reading the EvidenceExamine the main lines of physical evidence, ice cores, the Keeling Curve, and the temperature record, that document rising CO2 and warming.Ice cores reveal CO2 stayed between 180 and 280 ppm for 800,000 years; today's 420-plus ppm is unprecedented. The Keeling Curve shows a steady rise since 1958, and independent temperature datasets agree on about 1.1 to 1.2 degrees of warming. Many independent fingerprints point to greenhouse warming.
4. Attribution: It's UsExplain how scientists establish that recent warming is human-caused and rule out natural drivers.Fossil carbon carries a distinct isotopic fingerprint, and emission accounting matches the observed CO2 rise. The sun, volcanoes, and natural cycles cannot reproduce the warming, but models including human emissions do. The IPCC calls human influence on warming unequivocal.
5. Feedbacks and Tipping PointsUnderstand how feedbacks like water vapor and ice-albedo amplify warming, and what tipping points are and are not.Warming from CO2 is amplified by feedbacks: more water vapor traps more heat, and melting bright ice exposes dark surfaces that absorb more sunlight. Most feedbacks amplify warming. Tipping points are real thresholds, but their exact locations and timing remain genuinely uncertain.
6. Climate, Weather, and ImpactsDistinguish weather from climate and survey the observed, measurable impacts of warming.Weather is day-to-day; climate is decades of statistics, and warming loads the dice toward extremes. Sea level rose about 20 cm since 1900 with an accelerating rate, Arctic ice has shrunk to a thousand-year low, and heatwaves are clearly more frequent, with confidence varying by event type.
7. Projections and ResponsesInterpret climate projections as scenario-based and outline the basics of mitigation and adaptation while separating well-established science from uncertainty.Future warming depends mainly on emissions, so scientists run scenarios spanning roughly 1.5 to over 4 degrees by 2100. Because warming tracks cumulative emissions, reaching net-zero is expected to roughly stabilize temperatures. The greenhouse effect and human cause are firm; sensitivity, timing, and human choices are less certain.

Questions this course answers

Grounded in trusted sources

• IPCC Sixth Assessment Report (AR6), Working Group I: The Physical Science Basis (2021) and Synthesis Report (2023), ipcc.ch
• NOAA Global Monitoring Laboratory and Scripps Institution of Oceanography, Mauna Loa CO2 record (the Keeling Curve), gml.noaa.gov/ccgg/trends and keelingcurve.ucsd.edu
• NASA Goddard Institute for Space Studies and NOAA National Centers for Environmental Information, global surface temperature record, climate.nasa.gov and ncei.noaa.gov

Every Wunder lesson is built from real, reputable sources — never invented.

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