Antarctic sea ice reached a record high this year, topping 20 million square kilometers (nearly 8 million square miles) in September — a milestone it hadn't touched since 1979.

It's a fact climate change deniers are fond of repeating. If the planet is warming, shouldn't sea ice be melting away rather than growing?

It's true that the phenomenon is a confusing one — but it's no proof that climate change isn't happening. In fact, scientists believe that climate change is actually responsible for the strange events down in the Antarctic. Walt Meier, a scientist from NASA's Goddard Space Flight Center, explains how this is possible in a new video from Science@NASA.

The first thing to note is that sea ice and land ice are two completely different things. Sea ice is simply frozen ocean water, which forms a layer of ice on top of the sea. Land ice originates on land, forming from compacted snow to form glaciers and ice sheets. Land ice melting into the oceans is what causes sea levels to rise.

While sea ice has been steadily growing in the Antarctic, land ice has actually been shrinking. In fact, a new NASA report shows that the melting rate of land ice in West Antarctica, the fastest-melting region on the continent, has tripled during the last 10 years. Researchers found that between 1992 and 2013, the region lost an average of 83 gigatons of ice every year.

Meier believes all this melting land ice might actually be causing the increase in sea ice. As glaciers melt, they pour cold freshwater into the ocean. Freshwater is easier to freeze than salty seawater, so the influx from the melting glaciers could be adding to Antarctica's sea ice.

Snowfall could also be a factor. As snow falls onto the existing sea ice, Meier explains, it weighs the ice down and causes it to sink just beneath the water's surface. Cold ocean water then seeps up and mixes with the falling snow, creating a slushy mixture that eventually freezes, thickening and expanding the sea ice.

It's unclear how much snowfall has fluctuated over the past few decades in Antarctica, but experts believe it will increase as the climate continues to warm. Numerous climate studies, including reports from the Intergovernmental Panel on Climate Change have warned that climate change will lead to increases in heavy precipitation events and more frequent and intense storms.

Even wind could be part of the answer. Climate change is altering weather patterns all over the globe, causing air flow to shift around the planet and storms to become more frequent and intense. This phenomenon is evident is Antarctica, which is becoming increasingly windy.

Meier says these winds can carry cold air from the icy continent out over the ocean, where they aid in the freezing process out in the open ocean.

Differing conditions and weather patterns around the world can lead to different outcomes — an impact of changing climate that we are literally seeing everywhere around us, from droughts in California to extreme November snow storms in Buffalo, NY.

It's not so strange that different part of the world would react differently to global warming. And we have very strong evidence that sea ice is quickly disappearing in the Arctic, wreaking havoc on animals such as seals and polar bears who need it for their hunting and breeding grounds.

So while the Earth's natural processes may sometimes be strange and confusing, there's no reason to doubt that climate change is really happening. In fact, as Meier suggests, science indicates that it may be responsible for some of the most surprising phenomena we're observing on the planet.