COMPREHENSION
Read the comprehension passage below and answer the questions on it.
Global warming is the rise in the average temperature of the earth's atmosphere and oceans. Since the early 20th century, the Earth's main surface temperature has increased about 0.8%C(1.4F) and scientists are worried about this development.
Scientists believe that global warming is primarily caused by an increased concentrations of greenhouse gases produced by human activities such as the burning of firewood and deforestation.
Global warming causes a rise in the sea levels, a change in the amount and pattern of precipitation, expansion of subtropical deserts and heavy rainfall.
QUESTIONS
What the passage about?