Months per year where the GMST is above a Climate Milestone


The graph counts shows how many months had an average-global-monthly-temperature above a given temperature milestone for each year, up to December 2023 (inclusive)
E.g. in 1975 there were 9 individual months averaging above 0.25C and 3 months above 0.5C.
As per section at the bottom of this page, the graph does have some smoothing to clean up the trend lines.

Interesting Observations

  • You can see the time it takes for a global temperature milestone to have it first monthly average value pass a global temperature milestone, until that milestone happens for every month of the year.
    • E.g. A month above 0.75C first appears in 1979, and by 2003 all 12 months of every year are above 0.75C.
  • The graphic appears to show acceleration.
    • Each milestone appears to take less time to go from first appearance, to a permanent part of the climate. The lines for the different milestones get steeper.
    • From 2014 things ramped up with months over 1.25C and over 1.5C happening almost at the same time. That said, it looks like there 1.5C started later than one might expect. Maybe some mix of natural variability, ENSO in La Nina phase, solar cycle minimum, increased aerosols. Who knows. I’ll have a look out for explanations
  • In 2023 we started to get Months above 1.75C
  • What is not on the graphic
    • Months in 2024 are not included.
    • You can’t see the individual 2C days that happened in November 2023 and February 2024.
  • Note that (as per Climate Reporting – Why so many different values), Berkeley Earth tends to report higher than the other key datasets (see GMST Data Sets), E.g. it is runs about 0.08C (3 years) ahead of Copernicus, and runs about 0.17C (7 years) ahead of NOAA / GISSTemp.

How the Graph was Created

This graphic uses the Berkeley Earth Dataset (See GMST Data Sets), which provides monthly average Global Mean Surface Temperatures (GMST) from 1850 until the present.

For each year, between 1850 and 2023 (inclusive), the graphic simply counts the number of months which are greater-or-equal to monthly temperature milestones.

The graph of the raw data is below. This is quite jumpy, so for the graphic at the top of the page (which was shared on twitter / X), I used a 5-year-centred average, with some rounding to get cleaner lines. For 2022 I used a 3-year-centred-average, and for 2023 I took an average of 2022 / 2023 weighted towards 2023.

Raw data Months above temperature milestones