Changes to polar climates pose a double threat. They directly affect polar life, but they also have important knock-on effects for climate systems all around the globe.
The Arctic: rapid warming, shrinking sea ice
In the Arctic, where ocean is surrounded by land, air temperatures have warmed very rapidly — twice the global average rate in some areas.
Sea ice cools the Arctic and moderates the planet's climate. But the thickness and extent of summer sea ice have shrunk dramatically over the past three decades.
Arctic warming is driving a vicious cycle. As white sea ice with its reflective surface melts away, the exposed darker ocean surface absorbs more heat. This speeds up warming, so Arctic temperatures rise further. This dangerous positive feedback cycle could further accelerate global warming.
Warming in Antarctica
In Antarctica, where land is surrounded by ocean, the picture is somewhat different. So far, wind and ocean currents help isolate this continent from global weather, keeping it cooler than it would be otherwise.
But climate change is still having negative effects. The West Antarctic Peninsula is actually one of the fastest-warming marine areas of the planet. Massive ice shelves there have already broken up and fallen into the ocean.
Melting ice sheets
Earth's two vast glacial ice sheets, in Greenland and Antarctica, lock up colossal quantities of water. They hold more than 99 percent of Earth's freshwater ice. They also influence the planet's climate and weather.
Scientists are still working to answer the crucial question, "how much will ice sheet melt add to sea level rise?" But they expect melting of these two massive ice sheets to have a huge effect on future sea levels.
Like a waking giant, the Greenland ice sheet is already melting. Each year its melt water adds almost a millimeter (0.7mm) to sea level. This amount is likely to increase this century. In the more distant future, if it were to melt completely, the Greenland ice sheet would add about 6m to sea level.
The even more vast Antarctic ice sheet is also losing ice, especially in the West Antarctic. So far this ice loss is less rapid and widespread than in Greenland. Yet complete meltdown of the Antarctic ice sheet would raise sea levels by a colossal 60m or more.
Tipping point for ice sheet melt
We may be fast approaching a tipping point, where the process of total ice sheet melt down cannot be halted even if we stop adding greenhouse gases to the atmosphere. Scientists fear we may already be at a tipping point for the ice sheet in the West Antarctic.
The planet's 190,000 glaciers are crucial frozen water reservoirs. They store up snowfalls and release this water gradually in warmer seasons. This provides billions of people with freshwater, a supply especially important in regions with dry seasons.
But glaciers are very sensitive to climate warming. They have been melting for the past three decades, their vital fresh water running downstream into oceans, adding to sea level rise. Glacier melt is speeding up, and if warming goes unchecked, some will melt completely.
What is Greenpeace doing?
Deep cuts to greenhouse gas emissions are needed to preserve glaciers and prevent tipping points for ice sheet melt. This is why Greenpeace is driving the urgent shift to 100 percent clean energy from the sun, wind, and other renewable sources.
From tiny algae and krill, to hefty walruses and polar bears, our polar life needs special protection. Because healthy oceans can better fight many impacts of climate change, Greenpeace is pushing for a global sanctuary in the uninhabited area around the North Pole. We're also fighting to ban oil drilling and destructive fishing in Arctic waters.
What can you do?
Find out what Greenpeace is doing where you live.
Choose your own climate change solutions to suit your life and your home.
Join our Save the Arctic movement and help Greenpeace make a stand for Arctic protection.