One-third of Man’s entire influence on climate since the Industrial Revolution has occurred since January 1997. Yet for 224 months since then there has been no global warming at all (Fig. 1). With this month’s RSS (Remote Sensing Systems) temperature record, the Pause sets a new record at 18 years 8 months.
Figure 1. The least-squares linear-regression trend on the RSS satellite monthly global mean surface temperature anomaly dataset shows no global warming for 18 years 8 months since January 1997, though one-third of all anthropogenic forcings occurred during the period of the Pause.
As ever, a warning about the current el Niño. It is becoming ever more likely that the temperature increase that usually accompanies an el Niño will begin to shorten the Pause somewhat, just in time for the Paris climate summit, though a subsequent La Niña would be likely to bring about a resumption and perhaps even a lengthening of the Pause.
The spike in global temperatures caused by the thermohaline circulation carrying the warmer waters from the tropical Pacific all around the world usually occurs in the northern-hemisphere winter during an el Niño year.
However, the year or two after an el Niño usually – but not always – brings an offsetting la Niña, cooling first the ocean surface and then the air temperature and restoring global temperature to normal.
