Quarterly Global Warming Report

Each blue, yellow, and red circle represents the average global air temperature in a prior month between 1960 and 2022, black circles represent data for 2023, and black squares represent data for 2024. From June 2023 through June 2024, global air temperature has been at record-high levels.

It is worthwhile to briefly explain the seasonal cycle of global average temperature that is apparent in this graph. The seasonality may seem counterintuitive given that, on a global level, the earth receives about the same total amount of solar energy per day throughout the year. When the northern hemisphere experiences fall and winter, the southern hemisphere experiences spring and summer, and vice versa. Less daylight in one hemisphere is counterbalanced by more daylight in the opposing hemisphere. This suggests that the global average temperature should remain roughly constant from one month to the next. However, the northern hemisphere contains over two-thirds of the earth’s land mass, and, in general, land heats up more quickly than does water in response to a given influx of solar energy. Consequently, global average temperature carries a strong signature of the northern hemisphere’s seasonal temperature changes.

Across the most recent 12 months of data -- from July 2023 through June of 2024 -- the average global air temperature was 59.24F, which is a record-high measurement across a 12-month period, and is 1.87F greater than the 1960-to-2019 average of 57.37F.

In the parlance of climate scientists, temperatures defined relative to their corresponding long-term averages are termed “temperature anomalies”. This graph presents both air temperature and sea-surface temperature anomalies. Each anomaly is defined as temperature averaged across a 12-month period minus the long-run average temperature computed across 1960 to 2019. Like the preceding graphs, this graph plots data through June 2024. The anomalies on the far-right of the graph are computed across the 12-month period from July 2023 to June 2024, and are at record-high levels.

This graph resembles the preceding graph, but the anomalies are averaged across the trailing 60 months rather than 12 months. The longer averaging period provides a better view of long-term trends. In addition to global temperature computed across the entire surface of the earth, the graph shows air temperature averaged across all land areas and air temperature averaged across all oceans and other bodies of water. The results reveal that air temperature over land has risen at a significantly faster rate than air temperature over oceans, which, in turn, has risen at a faster rate than sea-surface temperature.

To estimate the trend for global average air temperature, and to assess whether it is changing across time, linear regressions were run across the following overlapping 30-year periods: 1960 to 1989, 1965 to 1994, 1970 to 1999, 1975 to 2004, 1980 to 2009, 1985 to 2014, 1990 to 2019, and July 1994 to June 2024. Because the data for 2024 is partial, extending only through June, and because the use of a partial year of data could introduce seasonal bias into the regression, the final 30-year period runs from July 1994 through June 2024, providing 30 complete 12-month cycles. The other 30-year periods begin in January of the first year and end in December of the final year (e.g., January 1960 to December 1989).

The slope of each regression line provides an estimate of the rate-of-warming across the associated 30-year period. A period of 30 years is long enough cancel-out short-term climate cycles such as El Nino and La Nina which can influence global temperatures, but short enough to provide insight into potential changes in the rate of global warming.

The graph shows the estimated 30-year trends and their 95% confidence intervals. The estimated warming trend for the most recent 30-year period is 0.45F per decade, which is greater than the rate for any prior 30-year period.

Figure 6 focuses on the most recent 30-year period, from July 1994 to June 2024, presenting trends for global average air temperature and global average sea surface temperature. In addition, warming trends are displayed for air temperature across land areas (“Air, Land”), air temperature across oceans and other bodies of water (“Air, Ocean”), air temperature across land areas in the northern hemisphere (“Air, Land N”), and air temperature across land areas in the southern hemisphere (“Air, Land S”). As in Figure 5, “best” estimates as displayed as blue dots, and 95% confidence intervals are represented by vertical bars.

The results indicate that average air temperature is increasing at a significantly faster rate than average sea surface temperature, and that air temperature over land is increasing at a faster rate than air temperature over water. Lastly, with respect to air temperature over land, the northern hemisphere is warming at a faster rate than the southern hemisphere.