The natural greenhouse effect involves greenhouse gases like carbon dioxide and methane absorbing and emitting radiative energy from the sun, maintaining a global temperature around 33°C higher than it would be otherwise. However, human activities like burning fossil fuels and deforestation have increased greenhouse gas levels, enhancing the greenhouse effect and causing global warming. This impacts the climate through more extreme weather, melting ice, droughts, and ocean acidification as CO2 reacts with seawater.