What is the topic and main idea of the paragraph?

According to National Geographic, global wanning may have catastrophic effects. One of these consequences is the melting of polar caps at an alarming rate-an event which poses a danger to low-lying areas across continents. In fact, the polar caps are melting at a dangerous speed that the Glacier National Park in the United States w1ll be gone by 2070 if this keeps up. Aside from this, global warming also causes severe heat waves in North America. According to reports, at least 225 people had died due 10heat waves. An erratic weather pattern is another undesirable effect of global warming; summers become hotter and winters become colder. Hurricanes typhoons are also becoming more and more intense. If we will not do something today, our children’s children will inevitably face the consequences.