The Earth is already 1.1 degrees Celsius hotter than it was 150 years ago. Though a half-degree Celsius difference in temperature increase might seem unimportant, the difference for life on Earth could be huge.

Off the coast of Australia, the Great Barrier Reef is known for being large enough to be seen from space. It’s the size of Germany—a biodiversity hot spot that was once thought to be too big to fail. But over the last few decades, marine（海洋的）biologists like Hoegh-Guldberg have watched its rapid decline.

Oceans are warming along with the atmosphere, since they absorb much of the excess heat from climate change. Repeated marine heat waves over the last five years have turned much of the Great Barrier Reef a terribly white color. When temperatures rise, corals（珊瑚）remove the microscopic algae（海藻）inside them, losing their food source in the process. Sometimes the corals can recover, but increasingly, they’re dying off.

“Something around 50% of the shallow water corals were killed literally over a couple of months, in some cases over a couple of weeks,” Hoegh-Guldberg says. “If you extend that out into the future, we’ll get to a point where the damage overwhelms the ability of corals to bounce back. ”

Marine heat waves have already doubled in number since 1980 and are expected to become more intense as temperatures rise. At 1.5 degrees Celsius, it’s likely that 70% to 90% of coral reefs will die off worldwide. At 2 degrees Celsius of warming, 99% are lost. “If we delay even a year or two more, we really are going down a pathway where there will be no return. We need to act and we need to act decisively, without question and solve this problem. ” Hoegh-Guldberg adds.

【小题1】What do we know about the Great Barrier Reef?

A．It is supposed to never disappear.

B．It used to be indescribably massive.

C．It is too large to be seen from space.

D．It is growing over the last few decades.

【小题2】What are the effects of rising temperatures?

A．Changes in the shape of coral.

B．Increasing risk of coral death.

C．Growing coral recovery capacity.

D．Abundant food sources of corals.

【小题3】What does the underlined word “decisively” in the last paragraph refer to?

A．Decidedly.	B．Gradually.
C．Constantly.	D．Regularly.

【小题4】What is the text mainly about?

A．The temperature affects the life.

B．Climate change causes warming oceans.

C．Coral reefs face almost complete die-off.

D．Extreme heat waves double greatly in number.