One thing that causes a lot of confusion is the differences in various temperature trends, particularly satellite versus ground-based measurements. Using different instruments measuring temperatures at different places may give different short-term measures, but the trend should be the same. A recent paper (by Foster and Rahmstorf) illustrates that much of the difference is in the extent to which short-term variations like El Niño are picked up by these very different forms of measurement. You’ll find more discussion on Tamino’s blog and on RealClimate. These short-term variations do not change the trend, but cause more ripples in shorter time-scales. Once these short-term effects are eliminated, the trends line up very nicely:
|MEI is multivariate el Niño index, AOD is aerosol optical thickness data, representing mainly the cooling influence of volcanoes and TSI is total solar irradiance, representing variations in the sun.|
Here, the 2010 data point is no longer unequivocally a maximum. But it’s still one of the highest points on the chart despite the fact that the solar cycle is clearly a lot lower in 2010 than in 1998.