“The bottom line is that the contributions of the current El Niño and wind patterns to the very warm conditions globally over the last couple of months are relatively small compared to the anthropogenically driven increase in global temperature since pre-industrial times,” he added.
Steffen said the definitive assessment of this El Niño and its effect on the world’s temperature would only be possible once the event had run its course (it has now peaked and is expected to end in the second quarter of this year). But he agreed that past El Niño cycles could be an appropriate guide for the order of magnitude of the effect.
The picture becomes less clear cut when we talk about monthly records. Even weather trends can have small effects on the monthly average temperature, said Knight. The effect of El Niño traditionally increases as it dies, so Mann believes it may have added more than the “nominal” o.1C during the past three months.
In the Arctic, the effect of El Niño is poorly understood but likely to be weak, said Knight. “Given that the Arctic has been very warm for a number of years, with record low sea ice, it is more likely that the warmth there currently is part of a long-term trend rather than the response to a episodic event like El Niño.”