MacDonald, G.M. and Tingstad, A.H. 2007. Recent and multicentennial precipitation variability and drought occurrence in the Uinta Mountains region, Utah. Arctic, Antarctic, and Alpine Research 39: 549-555.
Droughts are becoming longer and more intense. Thus spake Al Gore, who made the unequivocal and all-encompassing declaration in his 21 March 2007 testimony before the United States Senate's Environment & Public Works Committee. And for this and other such declarations, which he associates with an impending planetary emergency and climate crisis, he received the 2007 Nobel Peace Prize.
What was done
In a study that actually cites some real-world data to back up its conclusions, MacDonald and Tingstad examined instrumental climate records to outline historical spatiotemporal patterns of precipitation variability in the Uinta Mountains of Utah (USA), after which they "used tree-ring width chronologies from Pinus edulis Engelm. (two-needle pinyon pine) trees growing near the northern and southern flanks of the Uinta Mountains to produce an ~600-year reconstruction (AD 1405-2001) of Palmer Drought Severity Index [PDSI] for Utah Climate Division 5," which they say "allows for the placement of 20th century droughts within the longer context of natural drought variability and also allows for the detection of long-term trends in drought."
What was learned
The two researchers report that "in the context of prolonged severe droughts," the 20th century "has been relatively moist compared to preceding centuries," and they say that their PDSI reconstruction and the Uinta Basin precipitation reconstruction indicate that "the early to mid 17th century in particular, and portions of the 18th and 19th centuries, experienced prolonged (>10 years) dry conditions that would be unusually severe by 20th century standards," noting that "the most striking example of widespread extended drought occurred during a ~45-year period between 1625 and 1670 when PDSI only rarely rose above negative values."
What it means
Not only in this particular part of the world, but all around the planet -- see the many geographical sub-headings under Drought in our Subject Index -- it can be demonstrated that Al Gore's claim that Droughts are becoming longer and more intense is either not supported by real-world data or actually shown to be 180 degrees out of phase with reality.