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Climate Change to Overpower Future Pauses in Warming

A hiatus in the warming of global average air temperatures over the past decade is not an unusual event in the observational record, even with global warming, according to research published in Geophysical Research Letters. In fact, researchers from the ARC Centre of Excellence for Climate System Science expect that these hiatuses may disappear altogether after 2030 until the Earth’s temperature has stabilised.

“We found that historically the temporary pauses in surface warming over the past 100 years have been caused by one of three factors: volcanic eruptions, the transition of a climate phenomenon known as the Interdecadal Pacific Oscillation (IPO) and, to a lesser extent, the release of human-produced aerosols into the atmosphere,” said the study’s lead author Nicola Maher.

Models of future climate show that these hiatus periods become increasingly unlikely by the second half of the 21st-century if carbon emissions continue to increase at the current rate. “We found that after 2030 the rate of global warming is likely to be so fast that even large volcanic eruptions on the scale of Krakatoa are unlikely to drive a hiatus decade and interrupt the rise in global average temperatures,” Maher said.

Despite some claims about the recent slowdown in the rise of global average temperatures, the historical record clearly shows that these pauses are not unusual.

The IPO is a well-known pattern of climate variability that can remain in a positive or negative state for 20–30 years before transitioning. During a positive state, less heat goes into the ocean and more remains in the atmosphere, leading to accelerations in global average temperatures. During a negative state, more heat goes into the ocean and less remains in the atmosphere, leading to pauses and sometimes even a decline in global average temperatures.

“Given the strong negative IPO phase during the past decade, we should have had cooling in global average temperatures were it not for the greenhouse gas concentrations in the atmosphere,” Maher said.

Prof Matthew England, a co-author of the study, expressed concern about how soon global warming could start to overwhelm decadal variability. “If our current pathway of emissions continues, global warming looks set to overwhelm decadal variability in the climate system. These hiatus decades look set to become highly unlikely in the second half of this century.”