BERLIN (AP) — Worldwide temperatures briefly exceeded a key warming threshold earlier this month, a hint of heat and its harms to come, scientists worry. The mercury has since dipped again, but experts say the short surge marked a new global heat record for June and indicates more extremes ahead as the planet enters an El Niño phase that could last years. 5 C global warming limit, beyond which there are major risks for humanity in terms of climate instability and ecosystem system losses