The most visually striking evidence of global warming is:
The correct option is c. Melting of glacial ice on nearly every continent
Declining sea ice is one of the most visible signs of climate change on our planet. Since 1979, Arctic sea ice extent in September (when the annual minimum is reached) has declined by more than 30 percent, according to the National Snow and Ice Data Center. The ice extent has been declining in other seasons too. Despite slightly larger ice extents in 2009, recent observations indicated the ice is thinner and much younger (less multi-year ice) than it used to be. Covering an average of 9.6 million square miles, these areas of ice floating on ocean waters play an important role in regulating our climate, by reflecting some sunlight back to space, and in the life cycles of many polar species