WHILE it is generally agreed that there has been an increase in global temperatures over the last 150 years there is much debate as to how continuous or sporadic this warming has been. I have suggested that understanding could be aided by focusing on one or a few reference stations – particularly given trends in global average temperature is potentially an artefact of how data from stations across the world is combined and then adjusted.
A technical paper, Secular temperature changes in Hawai‘i, published just last year in Geophysical Research Letters indicates there has been recent warming on the island of Hawaii and this has been most evident at high elevations. While the text in the paper emphasis this warming and suggests a potential negative impact, the charts in the same paper suggest that despite the increase in temperatures over the last 30 years, Hawaii is no warmer now than it was in the 1930s.
The paper’s summary reads:
WHILE the upward trend in global mean temperature has been intensively studied, some regional temperature trends are less well known. We document secular temperature changes in the Hawaiian Islands for the past 85 years based on an index of 21 stations. Results show a relatively rapid rise in surface temperature in the last 30 years, with stronger warming at the higher elevations.
The bulk of the increase in mean temperature is related to a much larger increase in minimum temperatures compared to the maximum—a net warming about 3 times as large—resulting in a reduction of the diurnal range. For much of the period of record analyzed here, surface temperature in Hawai‘i has varied coherently with changes in the Pacific Decadal Oscillation (PDO). However, in recent decades, the secular warming has begun to predominate, such that despite the recent cooling associated with the PDO, surface temperatures in Hawai‘i have remained elevated. The greater warming trend at the higher elevations may have significant ecological impacts.
Notes and Links
Citation: Giambelluca, T. W., H. F. Diaz, and M. S. A. Luke (2008), Secular temperature changes in Hawai‘i, Geophys. Res. Lett., 35, L12702, doi:10.1029/2008GL034377.
The figure from the paper shows: Average surface temperature anomalies in Hawaii. Time series calculated from monthly station data after removing the calendar month means and averaging into calendar years. Smoothed curve is the annual data filtered with a 7-yr running mean. Linear trends computed for two periods, 1919–2006 and 1975–2006. The latter period emphasizes the enhanced level of global warming documented by IPCC . (top) All stations (N = 21), with area weightings of 0.575 and 0.425 for low- and high-elevation stations, respectively. Middle panel: Time series plot from observing stations located at the lower elevations (<800 meters). (bottom) Time series plot from observing stations located at the higher elevations (> 800 meters). Error bars show +0.5 standard deviation. Thick lines show 7-yr running means. Asterisks indicate slopes significant at p = 0.05.
Paper via Luke Walker. And thanks.