In the ice-albedo feedback, what happens when sea ice melts away?

• The ocean immediately becomes covered by thicker ice.
• More dark ocean is exposed to sunlight.
• The exposed ocean reflects all sunlight into space.

Which comparison helps scientists track long-term change in late-summer Arctic sea ice?

• September sea ice extent across many years
• January and September sea ice extent in just one year
• Morning and evening air temperatures on just one day

Ice lost from Greenland and Antarctica's land-based ice sheets can enter the ocean and raise sea level.

A made-up practice model starts with 100 ice units. Remove 13 units for one decade and 13 more for another. How many units remain? This model is not satellite data.

Dark ocean absorbs extra sunlight as heat after sea ice melts. How can this affect nearby sea ice?

• It always freezes all nearby ocean water.
• It has no effect on any nearby sea ice.
• It can melt more nearby sea ice.

Microbes in wet, thawed ground can release methane. Why can this add to climate warming?

• Methane slows the escape of some heat to space.
• Methane reflects all incoming sunlight back into space.
• Methane stops all sunlight from reaching ocean water.

Which chain describes a permafrost feedback in which the first warming leads to more warming?

• Warming thaws ground, gases cool the air, and the ground freezes.
• Warming thaws ground, plant matter stays frozen, and gases vanish.
• Warming thaws ground, gases slow heat loss, and more ground thaws.

One September has more Arctic sea ice than the September before it. A student says this proves the long-term decline has ended. Which explanation checks that claim?

• One year's increase proves the Arctic's long-term decline has ended.
• One year's increase can occur during a long-term decline.
• One year's increase shows all earlier satellite measurements were false.