But, as pointed out, the critical thing to see is that average tmperatures have NOT increased the past 8 years (1998 through 2006-2007: they HAVE remained steady, DESPITE the tremendous increase in greenhouses gasses from China and India and Brazil over those 8 years!
There's no expectation of linearity in a chaotic system, and the CO2 concentration is only going up a couple ppm. Over time, that becomes significant. In any given year, that's not much different than the year before. (Remember, you liked my post about the difference between climate and weather - a decade is barely enough to discern climate trends.
But... imagine if there had not been a monstrous El Nino in 1998, and it had been a normal or just slightly warmer year due to a moderate El Nino. Then what would the trend look like? 1998 threw off everything -- it yanked a small positive trend significantly higher, and it's so big that it disturbs perception of the underlying trend.