The AR4 WG1 SPM claims that there has been an increase in intense tropical cyclone activity "in some regions since 1970" (Table SPM2) and "in the North Atlantic since about 1970" (page 9). 

This is a misleading cherry-picked distortion of the data in the main report, which shows the following figure of the "ACE index", a measure of wind strength, on page 304:

Here we can see that there is really no meaningful trend.  For the North Atlantic, the SPM misleads its readers by pointing out the increase since 1970 but neglecting to mention the decrease prior to 1970.

See point 35 for more information on this, plus references.