Final answer:
Increased levels of greenhouse gases like carbon dioxide trap heat in the Earth's atmosphere, leading to global warming.
Step-by-step explanation:
The greenhouse effect is a natural process that helps to regulate the Earth's temperature. However, the increased levels of greenhouse gases such as carbon dioxide in the atmosphere, mainly due to human activities like burning fossil fuels and deforestation, are enhancing the greenhouse effect and causing global warming.
When sunlight enters the Earth's atmosphere, it warms the surface, and heat is radiated back as infrared or heat radiation. Greenhouse gases trap some of this heat, preventing it from escaping into space and causing the Earth's temperature to rise.