Which global effect primarily results when the Hadley cell circulation weakens in the tropics?

💡 Explanation

When the Hadley cell circulation weakens, the subsidence of dry air shifts poleward because the rising air mass near the equator is diminished, leading to reduced rainfall and expansion of arid zones beyond the traditional tropics. Therefore equatorial arid zone expansion results, rather than the other options which require fundamentally shifted forcing mechanisms in the polar regions or ocean systems.

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