Climate Change and Global Warming

Since the mid-twentieth century, human-caused greenhouse gases have been the most dominant driver of observed climate change.  The greenhouse effect describes how "greenhouse gases" trap heat at the Earth's surface. Greenhouse gases come from both natural and man-made sources.  Carbon dioxide, methane, nitrous oxides, and water vapor are examples of greenhouse gases. The greenhouse effect allows life to exist on Earth. Without it, the average temperature on Earth's surface would be roughly -19°C, rather than the current 14°C. However, increasing greenhouse gas levels, on the other hand, causes significant climate changes such as floods, droughts, and heat. As greenhouse gas emissions from human activities increase, they build up in the atmosphere and warm the climate, leading to many other changes around the world—in the atmosphere, on land, and in the oceans.