These tumbling temperature records are often accompanied in media reports by the caveat that we are experiencing a particularly strong El Niño - perhaps the largest in history. But should El Niño and climate change be given equal billing?
No, according to Professor Michael Mann, the director of Penn State Earth System Science Centre. He said it was possible to look back over the temperature records and assess the impact of an El Niño on global temperatures.
“A number of folks have done this,” he said, “and come to the conclusion it was responsible for less than 0.1C of the anomalous warmth. In other words, we would have set an all-time global temperature record [in 2015] even without any help from El Niño.”
Global surface temperature is the major yardstick used to track how we are changing the climate. It is the average the UN Paris agreement refers to.
But the atmosphere doesn’t stop at the surface. In fact 93% of the extra energy trapped by the greenhouse gases humans have emitted gets sunk into the oceans – just 1% ends up in the atmosphere where temperature is most often and most thoroughly measured. During El Niño, which occurs every three to six years, currents in the Pacific Ocean bring warm water to the surface and heat up the air.
Jeff Knight from the Met Office’s Hadley Centre, said their modelling set the additional heat from a big El Niño, like the current one, at about 0.2C. He said wind patterns in the northern hemisphere had added another 0.1C to recent monthly readings.