Is it getting warmer?

Over 3 years ago (September 2016) this graph was published….

Plot shows global climate variability (bumps) and climate change (long-term upward trend). The 12-month running mean is >1.2°C above pre-industrial levels.

For decades we have reported/updated the global temperature record, showing the calendar-year annual-mean temperature, usually with the 5-year running-mean included. I submit that the graph above is not only more beautiful, but more informative and it can be usefully updated every month rather than once a year.

The 12-month running-mean takes out the seasonal cycle just as well as the calendar-year mean and includes the calendar-year mean (black squares). The 11-year running mean does a pretty good job of taking out solar cycle variability and shorter-term variability such as the Southern Oscillation.

Note that the calendar-year means tend to fall a bit below a preceding maximum in the 12-month running mean, so the 2016 mean will probably fall a bit below the current +1.3°C warming relative to 1880-1920. That small drop is usually related to the phasing of the El Nino cycle relative to the calendar year.

BTW, this graph also switches to 1880-1920 as a base period, because of the widespread interest in themagnitude of warming relative to pre-industrial time. Alternatively, one might argue for an earlier base period, say 1700-1800, but the data are much poorer then and the difference in global mean is only about +0.1°C ± 0.1°C (1880-1920 slightly warmer than 1700-1800), so it is of no practical importance.

Source James Hansen and Makiko Sato

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