NOAA's National Centers for Environmental Information
Use the form below to select from a collection of monthly summaries recapping climate-related occurrences on both a global and national scale.
Global Climate ReportSeptember 2023
Mean Monthly Temperature Records Across the Globe
Overview
The mean monthly temperature records product provides historical perspectives on the occurrences of warm or cold mean monthly temperatures across the globe from the gridded (5° latitude by 5° longitude) NOAAGlobalTemp. On a monthly basis, the percentage area of the globe experiencing record warm or record cold conditions is reported as a time series for the month from 1951 to the present, complementing the percentile maps, but choosing a start date with relatively uniform and broad global coverage. In addition, the ratio of warm-to-cold records is plotted as a time series. For example, a ratio value of 2 indicates that the global area experiencing record warm mean monthly temperatures over the most recent month was 2 times larger than the global area experiencing record cold conditions.
September 2023 Global Land and Ocean
During September 2023, 20% of the world's surface had a record-high September temperature—the highest percentage of any month on record since the start of records in 1951. Across the global land, 35.01% of its surface had a record-high September temperature, the highest percentage of any month since records began. No global land surface had a record-cold temperature this September. Across the global ocean, 13.02% of its surface—the third-highest percentage of any month on record—had a record-high temperature for the month and only 0.11% had a record-cold temperature. Less than 1% (0.08%) of global land and ocean surface experienced a record-cold September temperature.
Methodology
Only grid cells that are completely free of missing values from 1951-present are utilized in the analysis, generally limiting our domain to 45°S to 75°N. For each retained grid cell, the warmest and coldest mean monthly temperatures in the 1951-present period of record are identified for each month. These monthly records are expressed as percent areas aggregated over 3 spatial domains: global land-only areas, global ocean-only areas, and the combined global land and ocean. The spatial aggregation accounts for differences in grid cell size with latitude (i.e., cosine weighting) as well as the fraction of land and ocean areas within coastal grid cells. Monthly ratios are computed by dividing the areal extents experiencing warm records with the areal extents experiencing cold records. For seasonal and annual aggregations, the warm and cold record areal extents are summed separately before dividing the totals.
- Ratio values between 0.8 (five-to-four) and 1.25 (four-to-five) are shown in gray.
- Red circles indicate values above 1.25.
- Blue circles indicate values below 0.8.
- Dark red (dark blue) values represent one of two things:
- A ratio value that is greater than 50 (less than 0.02)
- An observation in which the warm (cold) record area is non-zero and the cold (warm) record area is zero.
- In rare cases, the warm and cold record areas are both zero, in which case the value would be shown as a dark gray circle over unity (i.e., a value of 1).
