Discrepancy in Temperature Trends Explained
A new study appearing in Geophysical Research Letters (June 26, 2002) by Richard Lindzen and Constantine Giannitsis at MIT proposes an explanation for the discrepancy between surface and satellite temperature data. It also argues for lower climate sensitivity than is generally assumed.
Scientists have been puzzling over the difference in temperature trends between the surface layer of the atmosphere up to about 5,000 feet and the layer above that known as the troposphere. Since 1979, when scientists began using satellites to take the temperature of the troposphere, it appears that even while the surface has apparently warmed, tropospheric temperatures have remained steady. This is puzzling because greenhouse theory says that the troposphere should warm first, followed by the surface layer.
This scientific controversy even merited special attention from the National Research Council, which assembled a panel to assess the situation. It concluded that both the surface data and the satellite data are correct, but only speculated about the possible causes.
According to the study, “The surface data suggests a warming of about 0.25 degrees C, while the satellite data shows no significant increase.” Because the satellite data began in 1979, however, it has been noted that it is too short to “infer trends from any of the series since the trends estimated depend greatly on the subintervals chosen.” Fortunately, the close agreement between the satellite and weather balloon data, which also measures tropospheric temperatures, allows for a longer time period to be considered.
Looking at the balloon data the study notes that there was a pronounced jump in the atmospheric temperature of about 0.25 degrees C in 1976. The surface followed suit but at a slower pace, taking about ten years to catch up. The delay in the surface data is probably due to the heat capacity of the oceans, which is related to overall climate sensitivity. The delayed response also accounts for the discrepancy between the surface-based temperature data and that taken from satellites. Since the satellite data began in 1979 it missed the jump in 1976, which was documented in the slower surface warming.
More importantly, the rate at which the surface temperature caught up with the tropospheric temperature can be used to calculate climate sensitivity. The study finds that the surface temperature will rise about one degree C for a doubling of carbon dioxide levels. This is significantly lower than predictions made by the United Nations Intergovernmental Panel on Climate Change, and provides empirical support to climate skeptics who argue that climate sensitivity has been significantly overstated.
The study concludes, “The longer series suggests that the increase in tropospheric temperature occurred rather abruptly around 1976, three years before microwave observations began. The suddenness of the tropospheric temperature change seems distinctly unlike what one expects from greenhouse warming, while the relative rapidity with which the surface temperature caught up with the troposphere, less than about 10 years, suggests low climate sensitivity for a wide range of choices for thermocline diffusion.”
New York Times Halfway Corrects Alaska Story
On June 16, the New York Times ran a story on the front page that claimed that average temperatures in Alaska had risen 7 degrees over the last thirty years. The figure was later repeated in a June 24 Times column written by Bob Herbert.
The article was criticized by scientists who keep track of Alaskas temperatures, prompting the paper to correct the story on July 11. The Times wrote, “A front-page article on June 16 about climate change in Alaska misstated the rise in temperatures there in the last 30 years According to an assessment by the University of Alaskas Center for Global Change and Arctic System Research, the annual mean temperature has risen 5.4 degrees Fahrenheit over 30 years, not 7 degrees.”
But according to the Alaska Climate Research Center, this figure is still too high. Using data from temperature stations in Barrow, Fairbanks, Anchorage and Nome, which represent a cross section of Alaska from north to south, the researchers found that, “the value of 5.4 degrees F too great by a factor of two for the 1971 to 2000 period, the last 30 years.” These stations were chosen because they are professionally maintained and yield high quality, long term data.
Australias CSIRO Plays Games with Sea-Level Numbers
The Commonwealth Scientific & Industrial Research Organization (CSIR) in Australia has published a brochure on sea-level rise in support the Intergovernmental Panel on Climate Change. The brochure does make some good points, but it also presents a phony picture on sea level changes in Australia.
It notes, for instance, “No acceleration [in sea-level rise] has been detected during the 20th Century.” It also points out that, “If greenhouse gases are stabilized today, sea-level rise will continue for hundreds of years.”
When it comes to describing sea-level change in Australia, however, CSIRO only presents a small amount of the available data, which gives an erroneous picture of the true changes. The brochure states, “In Australia the rise in sea-level relative to the land (June 2001) at Fremantle is 1.38 mm/year with more than 90 years of data, and at Sydney 0.86 mm/year from 82 years of data. (Corrected for land motion, the rate of sea-level rise at these two locations is estimated to be about 1.6 to 1.2 mm/year respectively.)”
John Daly, who runs the Still Waiting for Greenhouse (www.john-daly.com) website, has pointed out that there are 23 long term tide gauges in Australia, not just two. Using all of the data, the National Tidal Facility of Australia has determined that there has been a sea-level rise of only 0.3 mm/year. Moreover, the two tide gauges cited by CSIRO are outliers due to land subsidence caused by ground water withdrawal.
CSIRO may have also erred in its calculation of land motion at the Fremantle site, says Daly. According to data from Perth, which is 20 miles away, the land has been subsiding at a rate of 2.08 mm/year since 1996. If that rate of land subsidence has been going on for some time, that would mean that there has actually been a lowering of sea-level at Fremantle of about -0.7 mm/year. Further support for this can be found by examining tide gauges on either side of Fremantle, Bunbury to the north and Geraldton to the south. These show a sea-level change of +0.4 mm/year and -0.95 mm/year, respectively.
In a presentation to the Cooler Heads Coalition in May, Daly noted the importance of Australia in determining rates of sea-level change since it is fronted by three oceans. The data from Australia suggest that there is little to no sea-level change. The CSIRO brochure is available at www.marine.csiro.au.
Etc.
Thursday, July 25, is the fifth anniversary of Senate passage of the Byrd-Hagel Resolution by a 95 to 0 vote. Exercising its constitutional role of advising the president on international treaties, the Senate warned then-President Clinton not to negotiate a protocol to the U. N. Framework Convention on Climate Change that would significantly harm the U. S. economy and that did not include significant participation by developing nations. The U. S. negotiating team took this position to Kyoto in late November 1997, but then-Vice President Al Gore flew to Kyoto in early December and successfully demanded that these two conditions be abandoned. Negotiations on the Kyoto Protocol were concluded on December 11, 1997.