Realclimate.org has a graph that beautifully shows that short-term trends often don’t show the long-term trend.
Gavin Schmidt and Stefan Rahmstorf explain:
The red line is the annual global-mean GISTEMP temperature record (though any other data set would do just as well), while the blue lines are 8-year trend lines — one for each 8-year period of data in the graph. What it shows is exactly what anyone should expect: the trends over such short periods are variable; sometimes small, sometimes large, sometimes negative — depending on which year you start with.
The data clearly shows that short-term comparisons don’t tell us anything. The rest of their article goes on to look at the reaons why this is so.
— Earl K.