Climate change's devastating effect can feel speculative when we talk about rising carbon-dioxide levels and shifting weather patterns. But they're distressingly real when we see what they are doing to starving polar bears.

Scientists are yet to determine that climate change leads to this starvation. However, lots of evidence suggest that starving polar bears face food shortages due to the destruction of their hunting grounds as more ice covers melt.

A 2015 study found that the polar bear population in the southern Beaufort Sea has dropped by 40 percent due to sea ice loss.

Another study conducted by the US Geological Survey and the University of Wyoming confirmed that polar bears are spending more energy walking across drifting sea ice caused by global warming.

Nature photographer and biologist Paul Nicklen recently shared a gut-wrenching video on social media that he captured on Somerset Island, in the Canadian territory of the Arctic Circle.

The clip shows an emaciated polar bear clinging to life while searching for food, its white hair limply covering its thin, bony frame.

One of the bear's back legs drags behind it as it walks, likely due to muscle atrophy. Looking for food, the polar bear slowly rummages through a nearby trashcan used seasonally by Inuit fishers.

Being born and raised in the northern areas of Canada, Nicklen has seen more than 3,000 bears. But he has never witnessed such a heart-wrenching sight in his life.

The photographer, together with his college, Cristina Mittermeier, stood there crying, with tears rolling down their cheeks as they were filming it.

Seeing a dying polar bear struggle to move and desperately dig for food in a trash can is hard to watch on video. For Paul Nicklen and Cristina Mittermeier, it was even harder to witness in person.

Cristina told National Geographic:

"Some have criticized us for not doing more to help the bear, but we were too far from any village to ask for help, and approaching a starving predator, especially when we didn't have a weapon, would have been madness."

Even though the clip is painful to watch, Nicklen and Mittermeier decided to share it to show other people what it looks like when scientists say that polar bears are going extinct and are going to starve to death.

Mittermeier said:

"In the end, I did the only thing I could: I used my camera to make sure we would be able to share this tragedy with the world."