Data Dive · Rung 2 · What's Reported · 2.5

The smoothest line in science

What a measurement looks like when almost nothing is wrong with it.

Runs in 15 minutes · everything you need is on this page · no network, no accounts, nothing for the students to open

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Look

Carbon dioxide at Mauna Loa

Atmospheric carbon dioxide, 1959-2025NOAA Global Monitoring Laboratory - 67 years, 67 of them higher than the lastCO2, parts per millionyearannual mean CO2 at Mauna Loa213.675427.3501,9601,9802,0002,020

Annual mean, 1959-2025, NOAA Global Monitoring Laboratory

67
years
67
of them higher than the year before
0
exceptions
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The contrast

Put it beside the 311 chart

Los Angeles 311 moves 8.8% from month to month. This moves 0.47% from year to year — about nineteen times smoother.

One is a city full of people deciding whether to call. The other is one instrument on one mountain, sampling air.

AskWhy is one of these so much noisier than the other? What is being measured, in each case?
The three questions
  1. What was actually measured, and by whom?
  2. How many years rise? Check it.
  3. Which of these two would you trust to tell you about next year, and why?
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After the dive

The shapes on this page, in the library’s own words

the line

Follow it left to right. A dashed part is a guess about the future, not something anyone saw.

What it leaves outThe line implies every point between the dots, and nobody measured those. Where you start and stop it decides what the trend looks like.

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