<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 causes the greenhouse effect? Context: The greenhouse effect is caused by the accumulation of greenhouse gases in the Earth's atmosphere, such as carbon dioxide and methane, which trap heat and lead to a rise in global temperatures. Answer: [/INST]The greenhouse effect is caused by the accumulation of greenhouse gases in the Earth's atmosphere, such as carbon dioxide and methane, which trap heat and lead to a rise in global temperatures.</s>