Climate
8th Grade Science · 6 lessons
Start lesson 1
Lessons
- 1The Greenhouse Effect, Molecule by MoleculeThe Sun delivers mostly visible light, which passes through the atmosphere almost untouched; Earth re-radiates that energy as longer-wavelength infrared. Molecules of three or more atoms — carbon dioxide, water vapour, methane — can bend and stretch at infrared frequencies and so absorb it, while nitrogen and oxygen, which together make up 99% of the air, cannot. That is precisely why a trace gas at 0.04% governs the planet's temperature and the overwhelming bulk of the atmosphere does not.Experiment
- 2The Ocean Conveyor Moves Heat by DensityWind-driven surface currents carry warm water poleward, where it cools and, as sea ice forms and leaves its salt behind, grows saltier and denser until it sinks and returns at depth. This thermohaline circulation transports roughly as much heat as the atmosphere does, which is why north-west Europe sits several degrees warmer than other places at the same latitude. Meltwater dilutes the sinking limb, and that is the mechanism behind concern that the circulation could slow.Experiment
- 3Feedbacks Set the Size of the ResponseCarbon dioxide acting alone would warm Earth by roughly one degree for each doubling of its concentration. The projected range of two to four and a half degrees comes almost entirely from feedbacks: warmer air holds more water vapour, itself a powerful greenhouse gas, and melting ice replaces a surface reflecting about 80% of sunlight with ocean absorbing over 90%. The uncertainty in a climate projection is therefore mostly uncertainty about feedbacks, not about the carbon dioxide itself.Experiment
- 4Weather Is Not Climate, and the Tails Move MostClimate is the statistics of weather over decades, so one cold winter disproves a warming trend no more than one tall pupil disproves an average height. What a warming climate changes is the whole distribution: shift the mean of a bell curve a little to the right and record heat becomes dramatically more common while record cold becomes rarer, because the change at the tails is proportionally far larger than the change at the middle.Lesson
- 5Converging Lines of EvidenceSurface thermometers, ocean heat content, sea level, glacier mass, sea ice extent and the shifting ranges of species are measured by different instruments, by different research groups, with entirely different sources of error. They agree. A fault in the thermometer network would not move the glacier record, and an error in satellite altimetry would not change where the birds nest — which is why convergence across independent records is stronger evidence than any single record, however long it runs.Lesson
- 6Mitigation, Adaptation and the LagCarbon dioxide already emitted remains airborne for centuries, and the oceans take decades to finish warming in response to what is already there, so a degree of further change is committed whatever happens to emissions now. Mitigation acts on the far end of that lag by cutting future emissions; adaptation acts on the near end by reducing harm from change already under way. Treating them as alternatives misreads the timescales — the real question is how to split a budget across two different decades.Lesson
🖨️
View in ShopGet all 6 Climate lessons as PDF
Printable worksheets & answer keys — $4.99