Page 38 - 新思维科学学生用书9 样章

1.4 Climate change

Questions

1 You learnt about asteroids in Stage 8. Describe what an asteroid is, and where asteroids are found.
2 Outline three different ways in which the asteroid collision 67 million years ago would have
made it difficult for plants and animals to survive.

Climate change today and in the future

For the last 2000 years or so, our climate has been fairly stable. People living in different places have

become used to having more rain at some times of year than at other times, or temperatures that
change in a predictable way during one year. Knowing this helps people to choose the best crops to
grow, and to know when they should sow seed and collect the harvest.

Now, however, the mean temperatures on Earth are increasing. This is caused by an increase in carbon
dioxide concentration in the atmosphere. Remember that carbon dioxide is a greenhouse gas, which
traps heat energy close to the Earth’s surface. When carbon dioxide concentration increases, more heat

is trapped.

The graph shows how the Earth’s mean temperature changed between 1880 and 2016. Notice that the
y-axis on the graph does not show the actual temperature – it shows how much it differs from the
temperature in 1880.

+1.5

+1.0

Di erence
from +0.5
temperature
in 1880 in °C

0.0

−0.5
1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
Year

37