Effects of global warming
The effects of global warming are already visible in many areas of the world. For example, in Montana's Glacier National Park, where about 150 glaciers were once located, only 25 glaciers larger than 25 acres remain, according to the U.S. Geological Survey (USGS). A commonly accepted guideline for identifying a glacier — a body of snow and ice that moves — is that the object must be about 101,000 square meters or about 25 acres in size. Below this size, the ice is generally stagnant and does not move, unless it is on a steep slope.
Scientists have expressed confidence that climate change will make hurricanes more intense, as well; the unusually strong hurricanes that have formed over the past few years give evidence for this. "We are confident not just because models predict hurricane intensification, but because we understand the reasons why they do and can explain those reasons in terms of what we know about how hurricanes work today," said atmospheric scientist Adam Sobel, author of "Storm Surge: Hurricane Sandy, Our Changing Climate, and Extreme Weather of the Past and Future" (HarperWave, 2014).
Sobel, a Columbia University professor in the departments of Earth and Environmental Sciences, and Applied Physics and Applied Mathematics, explained that hurricanes get their energy from the temperature difference between the warm tropical ocean and the cold upper atmosphere. Global warming increases that temperature difference.
Temperatures are getting more intense, as well. North America reached record highs in 2012, making it the hottest year since record keeping began in 1895. Scientists also recorded the second greatest number of temperature extremes (unusual highs and lows) in 2012. According to NOAA, 2013 tied with 2003 as the fourth warmest year globally since 1880, which is when the first year of global-temperature recording began.