An author's claim or argument is his or her stated opinion or belief. It is what the author will try to prove in the selection. For example, an author may argue that the use of cell-phone cameras violates a person's right to privacy. When you evaluate an author's claim, ask yourself if it is supported by valid, accurate, and appropriate evidence.
In paragraph 2, what evidence does the author give to support her argument that people are to blame?
Circle the letter of each correct answer.
Write the answers to the questions that follow.
According to the author, what proof do scientists have that people are to blame?
Scientists compared the amount of carbon dioxide in air samples today with that in air bubbles in ancient ice cores and found that there is more carbon dioxide now than at any time in the last 650,000 years.
Scientists analyzed the carbon dioxide in air samples from places around the world.
Earth is warming. Its average temperature has risen by 1.4°F over the past century. And it is predicted to rise another 2–11.5°F over the next hundred years. Why is this happening? People are causing global climate changes, mostly by burning fossil fuels! Fossil fuels like coal, oil, and natural gas produce needed energy for electricity. However, fossil fuels release carbon dioxide and other gases as they burn. This forms a kind of blanket or "greenhouse" around Earth, trapping heat inside. On one hand, this is good. It keeps Earth warm enough to sustain life. On the other hand, people use fossil fuels so much that the atmosphere is overloaded with greenhouse gases. This is causing global warming. The warmer it gets, the greater the danger for more severe climate changes. Earth's rising temperature has brought changes in rainfall, leading to more floods, droughts, and relentless heat waves. The 2010 heat wave across Eastern Europe and Russia was unprecedented. And 2012 saw new high temperatures records across America. Earth's oceans are warmer, so ice caps are melting and sea levels rising. The warmer water causes stronger storms. How do we know people are to blame? Scientists analyzed the carbon dioxide in air samples from places around the world. The results were then compared with the amount of carbon dioxide trapped in air bubbles in ancient ice cores from Greenland and Antarctica. The scientists discovered that there is more carbon dioxide in the atmosphere now than at any time in the last 650,000 years! There can be only one explanation: humans have added the extra carbon dioxide to the atmosphere that is warming Earth! Therefore, people must reduce greenhouse gases by using less fossil fuel.