Also note:
	The trend of increasing numbers of category 4 and 5 hurricanes for the period 1970–2004 is directly linked to the trend in sea-surface temperature.
	Other aspects of the tropical environment, although they influence shorter-term variations in hurricane intensity, do not contribute substantially to the observed global trend.
	Methodology based on information theory, isolating the trend from the shorter-term natural modes of variability.
	Source: Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity, C. D. Hoyos,* P. A. Agudelo, P. J. Webster, J. A. Curry. http://www.sciencemag.org/cgi/content/abstract/312/5770/94