According to the latest IPCC report (2013):
"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased"
Reading this I must ask: What about the 35 year-long temperature rise from 1910 to about 1945? It looks to me to be very similar (about 0.5C rise) to the more recent run-up from the late 1970s to about 2000. You will note that the global temperatures were falling from before 1880 until 1910 and then there were two periods when temperatures were steady or fell somewhat. The first period from the mid 1940s until the late 1970s then starting again from 2000 to today.
This suggests to me that there is more in play here than just CO2, since a similar rise was seen prior to when the majority of CO2 was emitted.
Below you see a similar trend with the ocean temperatures. I suspect that the ocean temperature changes may be a significant factor, if not the main diriver of global warming and not just the rising CO2 levels.
One key ocean indicator is the Pacific Decadal Osculation (PDO). The PDO is a warming and cooling of the Pacific Ocean over a time period of 2-3 decades. If you plot the PDO index you will see that the two periods of strong warming (1910 - 1945) and (1978 - 1998)corresponds well with the positive (warm) PDO while the two periods of no global warming or some cooling corresponds well with the periods of negative PDO.
Given the above, I suspect that although CO2 has some role here, the longer-term ocean cycles may have an even stronger effect. The warm global temperature for 2014, for example, reflects, in part, a brief return to the positive PDO this past year and as we return to a negative PDO in the coming years the warming will cease again.
If this is the case, we might expect little or no global warming for some years to come. A larger question is whether or not some longer-term ocean oculation may also be having an effect. One such suggestion has been offered by Dr. William Gray