A、Human activities contributed to the climate change. B、Vehicle emissions led to global warming. C、Greenhouse gas emissions woul

A government report says climate change is already affecting American agriculture. The new report is from the Climate Change Science Program, which brings together the research efforts of 13 federal agencies. President George Bush launched the program six years ago. Here are some of the findings by scientists: The growing season has increased by 10 to 14 days in northern parts of the United States over the last 19 years. Much of the East and South now get more rain than a century ago. But the report says there is some evidence of increased drought conditions in the West and Southwest. Western states have less snow and ice on the mountains and earlier melting in the spring. Fewer animals will die during warmer winters, but greater numbers will die during hotter summers. And temperature extremes reduce animal production of meat or milk products. The Department of Agriculture was the lead agency for the new report. Thirty-eight scientists from universities, national laboratories, nongovernmental organizations and federal service wrote it. They considered more than 1 000 scientific publications. The report was the strongest statement yet by the Bush administration that human activities are the main cause of climate change in the last 50 years. Carbon dioxide from the burning of oil, natural gas and coal is the main gas blamed for trapping heat in the atmosphere. The report says warming is very likely to continue in the United States during the next 25 to 50 years. And it says this is so even if future greenhouse gas emissions are reduced.
20. What’s the main idea of this passage?
21. What can we learn from the scientists’ findings?
22. What did the Bush administration declare strongly in the new report?