Data Dive 2.5

Can one machine on one mountain be trusted?

Some data jumps around. Some barely wobbles. The difference tells you something.

You will need paper and a pencil, and a browser for step 3

2.50 / 6Leave

Step 1 of 5 · Your guess

What do you think?

Since 1959, one instrument on a mountain in Hawaii has measured how much carbon dioxide is in the air. Carbon dioxide, or CO2, is a gas that traps heat and warms the planet.

A student says one machine's numbers are always messy: up, down, up, down. So you cannot trust it.

Write it down before you lookSketch what you think 67 years of CO2 measurements look like. Up and down? A slope? Something else?
2.5 · Can one machine on one mountain be trusted?1 / 6Leave

Step 2 of 5 · Look

Carbon dioxide at Mauna Loa, every year

Carbon dioxide in the air at Mauna Loa, Hawaiione point per year - NOAA Global Monitoring LaboratoryCO2, parts per millionyearyearly average CO2213.675427.3501960198020002020

The yearly average, measured on one mountain in Hawaii.

How to read it. Each point on the line is one year's average amount of CO2 in the air, in parts per million (ppm).

Find out
  1. Does it look like your sketch?
  2. Can you find any year where the line goes down?
2.5 · Can one machine on one mountain be trusted?2 / 6Leave

Step 3 of 5 · Try it

Now you try it, on the same data

This opens the pool, the site's chart tool. The words in bold below are buttons and menus you will see on the screen.

Do these five things

Open the pool on this file: data.sfhsbta.com/thepool?file=line_co2_mauna_loa_annual.csv&mark=line

  1. Under across, pick year. Under up, pick co2_ppm. Set view to table. Count the years that are lower than the year before.
  2. Go back to the chart. Set keep to to 350. How many years are left, and which is the last one?
  3. Clear keep to. Set keep from to 400. How many years are left, and which is the first one?
  4. Open line_la_311_by_month.csv as a line. It counts LA 311 requests by month. Count the months where the line goes down.
  5. Which of the two would you trust to predict next year? Write your prediction.
2.5 · Can one machine on one mountain be trusted?3 / 6Leave

Step 4 of 5 · Say it

Your answer, in one sentence

I think the CO2 machine <can or cannot be trusted> because <what the chart shows> and I checked it by <what you did to the chart>.

The last part matters most. It shows you did not just look at the chart, you tested it.

Here is one exampleI think the CO2 machine can be trusted, because in 67 years its line never went down once, while LA 311 went down in 5 months of one year. I checked by viewing it as a table and comparing each year with the one before.
2.5 · Can one machine on one mountain be trusted?4 / 6Leave

Step 5 of 5 · What you found

Check your numbers

0
years when CO2 went down
5 of 11
months when LA 311 requests went down
29, the last in 1987
years under 350 ppm
11, the first in 2015
years at 400 ppm or more
The big idea: where noise comes fromMessy data is not always a messy machine. The mess often comes from what is being measured. Air mixes slowly and steadily, so its line is smooth. 311 counts people deciding whether to call, and people are messy.
One more thing to think aboutWhat would convince you the machine was broken? What would convince you it was right?
2.5 · Can one machine on one mountain be trusted?5 / 6Leave

After the dive

The charts you used today

the line

A line follows one thing over time. Read it left to right and watch which way it leans — that lean is the whole story. A dashed stretch is a guess, not something anyone measured.

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

2.56 / 6Leave