Such feedbacks might involve ice on land and sea, clouds, or water vapor, which also absorb radiant heat.

这种反馈可能涉及陆地和海洋上的冰、云或水蒸气，这些也会吸收辐射热。

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In summer, some of the sea ice becomes water.

夏天里部分海冰会融化成水。

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Now, however, the sea ice is becoming water earlier than it used to.

然而，现在海冰比以前更早地融化。

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Since sea-ice is already in the water, its melting has little effect on sea levels.

ECONOMIST: Getting warmer

And finally, just before you head out to sea, you will pass a series of fascinating ice-making houses where huge blocks of frozen water slide down rollercoaster runners and into the waiting boats.

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And now the Arctic's upper layers are getting less dense, for several reasons: melting Arctic glaciers, rising surface-water temperatures, increased precipitation and an absence of salt concentrations resulting from sea-ice formation.

ECONOMIST: The science