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Tropics to launch into uncharted climate territory by 2038

Departure from historical climate variability projected to reach equatorial areas first

CLIMATE FIRSTS  Tropical areas are projected to reach unprecedented temperature highs sooner than regions farther from the equator. Cities’ years of projected departure from historical climate variability are shown, ranging from 2020 (orange) to 2100 (blue).

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Global temperatures will take a permanent leap above historical bounds by 2047 if greenhouse gas emissions continue unabated, a simulation suggests. In the tropics, the projected liftoff will occur by 2038.

Climate data from 1860 to 2005 served as a reference for ranges of high and low surface temperatures around the planet. Camilo Mora of the University of Hawaii at Manoa and colleagues averaged data from 39 climate simulations to project when temperatures would permanently depart from historical variability in different regions.

The model put the global average year of departure at 2047, but the date moves to 2069 if swift  measures are taken to limit greenhouse gas releases, the researchers report in the Oct. 10 Nature.

Tropical regions will experience unprecedented temperatures nearly a decade earlier than higher latitudes. Temperatures fluctuate more widely near the poles, so these regions take longer and require more of a temperature boost to depart from historical ranges than tropical regions do.

Developing areas will generally hit the records earlier than wealthier ones. The researchers project that Manokwari, Indonesia, for example, will hit unprecedented highs in 2020, whereas New York City will hit them in 2047. Reykjavik, Iceland, won’t cross the threshold until 2066.

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