Question

1. the picture to the right shows the extent of summer arctic sea ice in 1979 and 2005. which hypothesis is best supported by the changes in sea - ice overage?

a. earth’s climate is gradually warming.
b. sea ice is migrating away from earth’s poles.
c. arctic sea ice is increasing in size.
d. global warming occurs only at earth’s poles during the summer.
key
——1979
······2005

Explanation:

The map shows that the 2005 summer Arctic sea ice extent (dashed line) is smaller than the 1979 extent (solid line), meaning Arctic sea ice has decreased over time. This pattern aligns with the hypothesis of gradual global/planetary warming, as warmer temperatures would reduce sea ice coverage. Option b is unsupported as the ice is shrinking, not migrating away. Option c directly contradicts the observed reduction. Option d is incorrect because global warming is a planet-wide trend, not limited to the poles.

Answer:

a. Earth's climate is gradually warming.