Answer:
Global warming is the warming of our planet since the 1800's. Some people believe that the warming we have seen since man started becoming more industrialized is causing some of that warming. The slight warming that we have seen is not yet able to have caused any serious issues, that we can prove. What is predicted is what we must start to focus on, in case we start seeing warming.
It is believed, that in the future, it could cause polar bears to start dying off. It could someday start causing the Antarctic to melt. Other predicted issues are sea levels starting to rise at an accelerated rate, even though they have slowed the past few decades.
Just because there are no real issues now, does not mean that we will not have some in the future.