Sea Surface Temperatures (SSTs):
SSTs have been rising fairly quickly in the past 30 years, including a sudden 1F increase in 1976. From 1945-55, the tropical Pacific Ocean was often less than 66.5F, but since 1976, it has been rarely below 77F. The oceans have ~30 year lag vs. the atmosphere in terms of temperature shifts (think about how much longer it takes to heat up water than to heat up air) and so likely has not yet “felt” atmospheric warming that has taken place after the mid-1970s.
Tropopause:
The tropopause, the boundary between the troposphere and the stratosphere, has risen several hundred meters in a few years, as the troposphere below has warmed and the stratosphere above has cooled.

The layers of the atmosphere. We live in the troposphere, and almost all important weather (e.g. thunderstorms) takes place here.
Source: http://www.aerospaceweb.org/question/atmosphere/atmosphere/layers.gif

Species migration:
This is a very strong indicator of recent climate change. A large-scale study on a variety of land and ocean animals and plant species found since 1950 a poleward shift ~4 mi/decade as well as the advance of spring activity ~2.3 days/decade.
Rising Sea Levels?
Sea-levels have risen at an accelerating pace and is currently ~3 mm/yr in the past decade. However, most of this rise (which is still not incredibly fast) is attributed to thermal expansion—warm water takes up more space than cold water. Thus, while sea levels are not rising significantly due to melting ice (recall, though, that melting sea ice--i.e. that is floating on the sea and is not anchored to the ground--does not contribute to sea level rise. Analogy: as ice cubes melt in a glass of water, the water level does not rise!), this is still evidence for the existence of global warming.
Melting glaciers?
Arctic ice is indeed melting rapidly, as are the edges of the Greenland ice sheet and some edges of the Antarctic ice sheet. However, at the same time the Greenland and Antarctic ice domes in the middle of the ice sheets are cooling and growing. Thus, the current net global effect is believed to be slight melting, but not at a substantial rate. Nonetheless, the rapid loss of arctic sea ice is certainly disconcerting.

That concludes the basics of the science behind anthropogenic global warming. The case seems pretty clear, although there are legitimate concerns with the science. But those aside for the moment, what are the future risks that we face?