The Amazon, Earth's largest tropical rainforest, could be on the brink of an irreversible change as the ongoing El Niño strengthens its grip on our climate.El Niño is the warm phase of a multiyear natural climate cycle that is often marked by rising global temperatures and disruptive weather. This time, scientists monitoring the event are warning that climate change has helped supercharge it to likely the strongest ever recorded.As temperature records are breached and the risk of a humanitarian crisis looms, already stressed natural systems are coming under unprecedented strain. The Amazon is one such system. Having suffered severe degradation in recent decades, some fear that a historic El ...