Data Dive · Rung 3 · What's Related · 3.1

The window decides the answer

One series. One hundred and thirty-two honest answers.

Runs in 30 minutes · everything you need is on this page · no network, no accounts, nothing for the students to open

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The record

Global temperature, 1880 to now

Global temperature anomaly, 1880-2025NASA GISTEMP v4, against a 1951-80 baselineanomaly, degrees Cyearglobal temperature anomaly0.641.28-0.491,8801,9201,9602,000

NASA GISTEMP, annual anomaly

+0.083
degrees C per decade, whole record
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Now every window

Each 15-year slice, and what it says

What every 15-year window says about warming132 windows in one record - the full record trend is +0.083 C/decadetrend, degrees C per decadefirst year of the windowtrend of each 15-year window0.1920.384-0.2491,8801,9201,9602,000

The trend of every 15-year window in the record, plotted at its start year

-0.249
the flattest window says cooling
+0.384
the steepest says four times the truth

Every one of those is the same thermometer record, honestly computed. A person choosing the window chooses the answer.

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Make them do it

Cherry-pick, twice, on purpose

Worth knowing: the famous 1998–2012 ‘pause’ runs +0.136 in current data — steeper than the full record. Revisions and thirteen more years overtook the famous example. The lever is real; that illustration is stale.

TaskFind the fifteen years you would quote to argue warming has stopped. Then find the fifteen you would quote to argue it is accelerating. Both are in the file.
The three questions
  1. Where does this series start and end, and who chose that?
  2. What is the biggest and smallest answer you can honestly produce?
  3. What would you need to see in somebody else's chart to catch them doing this?
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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.

library · ladder · dives · the pool · this dive’s worksheet

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