Atlantic hurricanes and natural variability in 2005

TLDR

The 2005 North Atlantic hurricane season was the most active on record, causing unprecedented damage, and its intensity was linked to changes in tropical North Atlantic sea surface temperatures associated with the Atlantic Multi‑decadal Oscillation. Record‑high tropical North Atlantic sea surface temperatures in 2005 were 0.9 °C above the 1901–70 mean, largely driving the record hurricane season, but a revised AMO index explains only 0–0.1 °C of the anomaly, with about 0.45 °C attributable to global warming and 0.2 °C to post‑El Niño effects.

Abstract

The 2005 North Atlantic hurricane season (1 June to 30 November) was the most active on record by several measures, surpassing the very active season of 2004 and causing an unprecedented level of damage. Sea surface temperatures (SSTs) in the tropical North Atlantic (TNA) region critical for hurricanes (10° to 20°N) were at record high levels in the extended summer (June to October) of 2005 at 0.9°C above the 1901–70 normal and were a major reason for the record hurricane season. Changes in TNA SSTs are associated with a pattern of natural variation known as the Atlantic Multi‐decadal Oscillation (AMO). However, previous AMO indices are conflated with linear trends and a revised AMO index accounts for between 0 and 0.1°C of the 2005 SST anomaly. About 0.45°C of the SST anomaly is common to global SST and is thus linked to global warming and, based on regression, about 0.2°C stemmed from after‐effects of the 2004–05 El Niño.