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The planet experienced a positive IPO, or El Tio, in the periods 1925-1946 and 1977-1998, both of which were periods that saw "rapid" increases in global average temperatures, according to the study. The reverse — a prolonged negative phase, or La Tia — occurred from 1947-1976, when global temperature rise “stalled.” A Tia formation has been present since 1999, and Henley and King suggest that this may have been responsible for temperatures rising less than some scientists had expected.
A recent study in the journal Nature points to evidence of a return of El Tio, which Henley and King say could lead to a return of significant, average temperature increase around the world.
Using computer models, Henley and King ran a range of scenarios. But under no model variation was the outlook comforting.
"Even if the IPO remains in a negative phase, our research shows we will still likely see global temperatures break through the 1.5°C guardrail by 2031," Henley said in a statement. "If the world is to have any hope of meeting the Paris target, governments will need to pursue policies that not only reduce emissions but remove carbon from the atmosphere."