Slide 1 of 17
Over the last 100 years, global temperatures have warmed by about 1.33 degrees Fahrenheit (0.74 degrees Celsius) on average. The change may seem minor, but it's happening very quickly — more than half of it since 1979, according to the Intergovernmental Panel on Climate Change.
Though it can still be difficult to tease out how much climate change plays in any given weather event, changes are occurring.
In the spirit of Earth day, here's a look at our marvelous blue marble and the ways people and other living things are responding to global warming. [50 Amazing Facts About Earth]
Moving the military northwardSlide 2 of 17
Moving the military northward
As the Arctic ice opens up, the world turns its attention to the resources below. According to the U.S. Geological Survey, 30 percent of the world's undiscovered natural gas and 13 percent of its undiscovered oil are under this region. As a result, military action in the Arctic is heating up, with the United States, Russia, Denmark, Finland, Norway, Iceland, Sweden and Canada holding talks about regional security and border issues. Several nations, including the U.S., are also drilling troops in the far north, preparing for increased border patrol and disaster response efforts in a busier Arctic.Slide 3 of 17
Altering breeding seasonsSlide 4 of 17
Altering breeding seasons
As temperatures shift, penguins are shifting their breeding seasons, too. A March 2012 study found that gentoo penguins are adapting more quickly to warmer weather, because they aren't as dependent on sea ice for breeding as other species.
It's not just penguins that seem to be responding to climate change. Animal shelters in the U.S. have reported increasing numbers of stray cats and kittens attributed to a longer breeding season for the felines.Slide 5 of 17
High-country changesSlide 6 of 17
Decreased winter snowfall on mountaintops is allowing elk in northern Arizona to forage at higher elevations all winter, contributing to a decline in seasonal plants. Elk have ravaged trees such as maples and aspens, which in turn has led to a decline in songbirds that rely on these trees for habitat.Slide 7 of 17
Altered Thoreau's stomping groundsSlide 8 of 17