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	2^nd difficulty: Large uncertainty in observed changes.
	Top: annual total rainfall from 1 5x5o Gridbox, 50ish stations: sample only 3 (as available over large parts of world only): => variability and trend quite uncertain.

	Bottom: coverage of daily extreme rainfall, here for trend in wettest 5-day period in year. Data collected by Alexander et al. => very varying data density, many regions without coverage
	High density: US and ZA.
	Also look at spatial inhomogeneity in trends: very patchy!

	All these things make it difficult to convince ourselves which observed changes are due to greenhouse gas increases.