An observed trend is what the measurements show over time. Attribution is the claim about what caused it. Exam questions reward the first and ask for evidence before the second, so keep them in separate sentences.
This skill opens climate change evidence and responses and supports every later lesson.
How do you tell the two apart?
An observation can be checked directly against the data. You can point to a number, a year and a unit. An attribution cannot be read off the table, because a cause is not a column in the data.
A useful test: could someone confirm this sentence using only the table? If yes, it is an observation. If no, it needs other evidence and should be written with care.
How do you describe a trend step by step?
- Name the variable and unit, for example mean annual temperature in °C.
- Give the period, with the first and last year.
- State the direction and the size of the change using values from the data.
- Note any exceptions, such as a dip in one decade.
- Only then add a cause, and signal that it is an explanation rather than a reading.
Worked example
The decade means below are invented for practice. They come from a single imaginary weather station.
| Decade | Mean annual temperature (°C) |
|---|---|
| 1981 to 1990 | 26.9 |
| 1991 to 2000 | 27.1 |
| 2001 to 2010 | 27.3 |
| 2011 to 2020 | 27.6 |
Step 1, total change: 27.6 − 26.9 = 0.7 °C.
Step 2, average change per decade: there are three gaps between four decades, so 0.7 ÷ 3 = 0.23 °C per decade (to two decimal places).
Step 3, observation: “The station’s decade mean rose from 26.9 °C to 27.6 °C, an increase of 0.7 °C, with each decade warmer than the one before.”
Step 4, attribution, if asked: “This pattern is consistent with an enhanced greenhouse effect, but one station cannot show the cause on its own. Evidence from many stations and from measured greenhouse gas concentrations would be needed.”
The mistake to watch for
Mistaken answer: “The table proves that burning fossil fuels caused the 0.7 °C rise.”
The table contains no information about fuels. The sentence moves from a reading to a cause without evidence, and “proves” is too strong for one record.
The correction is to split it in two: report the rise, then offer the cause as an explanation supported by other evidence. A short phrase such as “this is consistent with” shows you know the difference.
Check yourself
1. Label each sentence as observation (O) or attribution (A). (a) “Rainfall in the town fell from 1,900 mm to 1,700 mm over ten years.” (b) “The fall in rainfall was caused by deforestation.”
Show answer
(a) is O, because it can be checked against the data. (b) is A, because a cause needs evidence the table does not contain.
2. A station records 12.1 °C in the first year of a twenty-year period and 12.9 °C in the last. Find the average rise per year.
Show answer
12.9 − 12.1 = 0.8 °C. Then 0.8 ÷ 20 = 0.04 °C per year. Check: 0.04 × 20 = 0.8.
3. Why is it risky to call one very hot year a trend?
Show answer
One year may be an extreme value caused by short-term variability. A trend needs a pattern across enough years that a single unusual year does not decide it.
Where this leads next
Next, practise reading full tables in interpreting a supplied emissions or temperature dataset. The statistics and distribution explorer is useful for seeing how an outlier changes an average.
If your written answers keep sliding from “shows” to “proves”, that is a habit worth fixing early, and it is the kind of pattern our teachers look for in online one-to-one Geography tuition.