Scientists warn that global warming could lead to a "hothouse earth" scenario, with some studies suggesting that deforestation and warming could push the amazon to a tipping point, possibly as early as the 2030s. The exact timing and temperature threshold for this tipping point are uncertain, with estimates ranging from the 2030s to the 2040s and a global warming threshold of 1.9°C. Some researchers believe that the earth has already hit its first climate tipping point, prompting calls for radical action to mitigate the effects of climate change.