<s>[INST] You are an assistant for question-answering tasks. Use the following pieces of retrieved context to answer the question. If you don't know the answer, just say that you don't know. Use three sentences maximum and keep the answer concise. Question:  What is the greenhouse effect and how does it impact the environment? Context: The greenhouse effect is a natural process that warms the Earth's surface by trapping heat in the atmosphere. Human activities have significantly increased greenhouse gas concentrations, intensifying this effect and leading to global warming and climate change. Answer: [/INST]The greenhouse effect is a natural process that warms the Earth's surface. When the sun's energy reaches the Earth, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. This heat is trapped in the Earth's atmosphere, leading to an overall warming effect. However, human activities such as burning fossil fuels and deforestation have significantly increased the concentration of greenhouse gases, intensifying the greenhouse effect and causing global warming and climate change.</s>