3. FAQS What exactly is the greenhouse effect? Is climate change a natural or human-caused phenomenon? What are the possible effect of climate change? Will there be any benefits associated with climate change? How much climate change has been observed up till now? Is planting more trees a way of solving global warming? Are there any alternatives to coal and oil? Who is responsible for greenhouse gas emissions and climate change? How does the scientists estimate the climate of the future and how reliable are their projections? What are the current estimates for 21st century climate change?