Keep negative temperature anomalies visible on a line chart

The direct answer

Use a linear value scale that includes the full negative and positive range. Anomalies below zero describe temperatures below the reference average. Removing those values or forcing a positive-only axis changes the historical comparison.

Prepare the observation table

Plot annual anomaly_c against year and include a zero_c column as a reference series if a reference-line control is unavailable. The example retains 1880–2023. Distinguish the reference line from observations and label the anomaly baseline separately from the numeric zero.

Public dataset and a reproducible example

The download is a prepared extract, not a live data connection. The source links below include the original query, observation period and reuse policy. Keep an original copy when you update the data; revised source values can change the result.

NASA GISTEMP v4 Land–Ocean Temperature Index, complete annual J-D values through 2023, in °C relative to 1951–1980. The CSV description row was removed; no baseline conversion was applied. Cite GISTEMP Team and the source link.

Snapshot retrieved: 2026-10-26. Prepared rows: 144.

Download the prepared CSVDownload the reference SVG

Build it in Datamon

Sign in with Google to create an editable visualization. Public articles and examples can be read without an account. The prepared CSV already contains the joins, filters or aggregations described above; do those steps in a spreadsheet first when using your own data.

1. Open Data and choose a file, or paste the table with its header row. Check the detected numeric columns, decimal separator and dates. The current importer accepts files below 20 MB; these examples are smaller. Keep blanks distinct from recorded zeros.
2. In Visualize, select Line chart. Connect the roles exactly as listed below. Review the preview against at least two rows in the example table rather than relying only on automatic mapping.
3. In Refine, add a title that states the question, the unit, observation period and source. Check labels and contrast at the size your reader will see. Keep a table when exact values matter.
4. Use the export controls for SVG, PNG, PDF or PowerPoint, then inspect the actual file. Save an editable project backup. Publish only after checking the underlying values: a public link makes the published data available to anyone possessing the URL.

Calculation and column mapping

The rule below is pseudocode. The downloadable CSV already contains the prepared values; spreadsheet functions and cell references depend on your sheet layout.

zero_c = 0 reference; retain all positive and negative annual anomalies

X

year

Y

anomaly_c, zero_c

Read the result

In this extract, anomaly_c ranges from -0.48 (1909) to 1.17 (2023).

Use the preview to check the structure and the CSV to check exact values. Its styling is a reference; your Datamon rendering can look different. Follow the mapping and preparation above to reproduce the analytical meaning.

Mistakes that change the meaning

A line chart can use a focused range when the full range is disclosed, but bars encode length from a baseline. Do not copy a tightly cropped line-chart scale into bars or imply that zero anomaly is zero physical temperature.

Questions before sharing

What is free and what needs an account?

Reading this guide and downloading its CSV and chart images are free. Datamon currently has no paid checkout or subscription plans in this deployment. Creating and saving an editable visualization requires Google sign-in. Provider-backed AI, cloud analysis, publishing and video depend on configured services; this guide does not promise unlimited free connected services.

Sources and further reading

• NASA GISTEMP v4
• NASA GISTEMP v4 · API / CSV
• NASA GISTEMP v4 · License / policy
• Data sources, queries and reuse notes
• Datamon · Blog
• Visualize line chart: easy guide, free example