Nature Climate Change | Climate Feedback

The global warming signal minus the El Niño noise

Andrew Revkin of the New York Times has been wondering whether climatologists could help turn down the “rhetorical noise” on recent temperature trends:

Given how much yelling takes place on the Internet, talk radio, and elsewhere over short-term cool and hot spells in relation to global warming, I wanted to find out whether anyone had generated a decent decades-long graph of global temperature trends accounting for, and erasing, the short-term up-and-down flickers from the cyclical shift in the tropical Pacific Ocean known as the El Niño – Southern Oscillation, or ENSO, cycle.

He queried Gavin Schmidt at RealClimate, who’s pondered how to reduce the noise (and beat the rhetoric) on climate trends before. Schmidt thought of the recent Nature paper in which David Thompson et al. removed ENSO fluctuations from the sea surface temperature record (and uncovered an abrupt 1945 temperature drop that they traced to buckets used to collect seawater after World War II).


On request, Thompson applied a similar cleanup to the global temperature record from the UK’s Hadley Centre (HadCRUT3v), and Schmidt followed suit using data from the Goddard Institute for Space Studies at NASA (GISTEMP):

enso_corr.jpg

The trends smooth slightly, apart from noticeable dips tied to volcanoes in 1963, 1982 and 1991. (If anyone knows what’s going on in 1976, please tell us in the comments.) And although the El Nino-driven scorcher in 1998 is abated, the last decade is still the hottest on record. But Revkin notes:

Frankly, there is probably enough of a short-term plateau and dip since around 2000 — particularly in the curves derived from the Hadley Center temperature data — to keep those opposed to restrictions on greenhouse gases fired up about the limited power of such substances to heat up the Earth. Again, the noise (both statistical and rhetorical) may persist long enough to paralyze policy debates, particularly as high energy prices push priorities in other directions.

If an ENSO explanation can’t dissipate the hot air over this short-term plateau, what about another source of ‘noise’? Next, Revkin is asking for an analysis that removes the effects of the Pacific Decadal Oscillation.

Smells like productive dialogue – thanks to Revkin’s extraction of worthwhile questions from the yelling.

Anna Barnett

Comments

  1. Report this comment

    Bishop Hill said:

    This posting adds to the stream of hot air which you so correctly observe is confusing all and sundry.

    Fortunately, light is being shed on the issue at Lucia’s blog where she and Gavin are getting into the nitty-gritty of the issue.