Read the passage carefully and answer the following questions:

The rise of air temperature near Earth’s surface over the past two centuries is known as global warming. Earth has experienced periods of gradual warming and cooling throughout its existence as a result of natural causes. Such natural causes have included volcanic eruptions and variations in the Sun’s output. However, scientists have attributed the recent increase in global temperatures to human causes- primarily the release of certain gases into the atmosphere as a result of industrial activity. These gases are known as greenhouse gases. They absorb and trap heat emitted from Earth’s surface through a process called greenhouse effect. The greenhouse effect is a natural process that helps to maintain the temperature suitable for life. Earth would be a frozen and likely uninhabitable planet. However, scientists who study climate have determined that increased concentrations of greenhouse gases resulting from human activity have amplified the natural greenhouse effect, causing global warming. The main greenhouse gases with human sources are carbon dioxide, methane, nitrous oxide, and halocarbons.  

Global warming is part of the more general phenomenon of climate change. The terms global warming and climate change are often used interchangeably, but they have distinct meanings. In addition to the rise in air temperatures, climate change encompasses changes in other elements of climate. These include variations in precipitation patterns, winds, and ocean currents. Another distinction between the terms is the time frame that they describe. Climate change includes changes that have taken place throughout Earth’s history. Some of these changes have occurred very slowly over a long period of time, such as hundreds of millions of years. Others, such as global warming, have occurred over much shorter time periods. The warming trend of recent times is a rapid and ongoing phase of climate change.

Question-4

Global warming has occurred

over the last two decades.

Ans-2