March 2, 2009
DO AS AL GORE DOES, NOT AS HE SAYS:
Global Warming: On Hold? (Michael Reilly, 3/02/09, Discovery News)
Earth's climate continues to confound scientists. Following a 30-year trend of warming, global temperatures have flatlined since 2001 despite rising greenhouse gas concentrations, and a heat surplus that should have cranked up the planetary thermostat.Posted by Orrin Judd at March 2, 2009 2:23 PM
"This is nothing like anything we've seen since 1950," Kyle Swanson of the University of Wisconsin-Milwaukee said. "Cooling events since then had firm causes, like eruptions or large-magnitude La Ninas. This current cooling doesn't have one."
Instead, Swanson and colleague Anastasios Tsonis think a series of climate processes have aligned, conspiring to chill the climate. In 1997 and 1998, the tropical Pacific Ocean warmed rapidly in what Swanson called a "super El Nino event." It sent a shock wave through the oceans and atmosphere, jarring their circulation patterns into unison.
How does this square with temperature records from 2005-2007, by some measurements among the warmest years on record? When added up with the other four years since 2001, Swanson said the overall trend is flat, even though temperatures should have gone up by 0.2 degrees Centigrade (0.36 degrees Fahrenheit) during that time.
The discrepancy gets to the heart of one of the toughest problems in climate science -- identifying the difference between natural variability (like the occasional March snow storm) from human-induced change.