Guest post by Marc Hendrickx
The case for dangerous man made global warming hangs on the wall like a frayed medieval tapestry. By pulling just one loose thread the whole thing starts to unravel. We pulled one of those threads recently…
The Australian Broadcasting Corporation (ABC) was recently caught making a mistake in a report on melting ice on Mount Everest. The ABC claimed that “Studies show temperatures are rising faster at Mount Everest than in the rest of South Asia.” When ABC were requested to provide details of the “Studies” they cited Table 10.2 from IPCC’s AR4 Working Group 2 report. However, contrary to ABC’s claims this table showed that the area of fastest rising temperature in South Asia was Sri Lanka, not the Himalaya (and hence not Mt Everest). ABC’s gaffe however served to highlight a few errors made by the IPCC. It turns out the IPCC incorrectly cited references that backed up the Himalayan temperature trends in Table 10.2, citing two conference papers and one peer reviewed paper that related to precipitation, not temperature (also covered in Table 10.2). Additionally references to support the high Sri Lankan temperatures appear to be from conference papers not from peer reviewed journal articles-(Follow references in Table 10.2).
After some digging the original work on the Himalayan temperature trends was found to be:
Shrestha, Arun B.; Wake, Cameron P.; Mayewski, Paul A.; Dibb, Jack E., 1999. Maximum Temperature Trends in the Himalaya and Its Vicinity: An Analysis Based on Temperature Records from Nepal for the Period 1971–94. Journal of Climate, 9/1/99, Vol. 12 Issue 9 pp:2775-2786.
It’s odd that the IPCC could not find more recent to back up its claims of rapid warming in the Himalaya in AR4. Readers may re-call the IPCC has a tainted record in reporting climate change in the Himalaya having been caught out using “grey literature” to back claims that Himalayan glaciers would disappear by 2035. These have now been shown to be false and the IPCC has issued a correction.
IPCC’s trend of 0.09º C.yr-1 for the Himalaya cited in Table 10.2 comes from Table 2 of Shrestha et al., 1999. This presents the regional mean temperature trends for the period 1977-1994 (just 17 years) based on a Kriging analysis. This is a geostatistical method of filling data gaps, great when you are calculating the extent of an ore body with loads of drill hole information but not so good when the data are limited, as is the case here. For the Himalaya, the IPCC also cherry pick the highest seasonal value, the figure for winter (0.09º C.yr-1). The annual figure given by Shrestha et al., 1999 is less: 0.057º C.yr-1.
But that’s not the end of the story; let’s look at the paper by Shrestha et al, 1999 in more detail. It provides an analysis of maximum temperature data from 49 stations in Nepal.
The abstract states:
Analyses of maximum temperature data from 49 stations in Nepal for the period 1971–94 reveal warming trends after 1977 ranging from 0.06 to 0.12C yr-1 in most of the Middle Mountain and Himalayan regions, while the Siwalik and Terai (southern plains) regions show warming trends less than 0.03C yr-1. The subset of records (14 stations) extending back to the early 1960s suggests that the recent warming trends were preceded by similar widespread cooling trends. Distributions of seasonal and annual temperature trends show high rates of warming in the high-elevation regions of the country (Middle Mountains and Himalaya), while low warming or even cooling trends were found in the southern regions. This is attributed to the sensitivity of mountainous regions to climate changes. The seasonal temperature trends and spatial distribution of temperature trends also highlight the influence of monsoon circulation.
The Kathmandu record, the longest in Nepal (1921–94), shows features similar to temperature trends in the Northern Hemisphere, suggesting links between regional trends and global scale phenomena. However, the magnitudes of trends are much enhanced in the Kathmandu as well as in the all-Nepal records. The authors’ analyses suggest that contributions of urbanization and local land use/cover changes to the all-Nepal record are minimal and that the all-Nepal record provides an accurate record of temperature variations across the entire region.
The time covered for the bulk of stations does not cover a single climate cycle so it’s hard to get excited about the results and we assume someone, somewhere will provide an update to extend the analysis to the present. Of the stations selected for the analysis only 5 stations with records dating from or before the mid 1960s were located in the Himalayan Region: Jiri (elevation-2003m), Okhaldunga (elevation-1720m), Chialsa (elevation-2770m), Chainpur (elevation-1329m), and Taplejung (elevation-1732m). Shrestha et al., 1999 define the Himalaya region in their figure 1 reproduced below.
The location of the stations is shown in the following image from Google Earth, note they are all concentrated in the very eastern part of Nepal (click to enlarge), with none in the western Himalaya, none west of Long 86.23. The vast bulk of the Himalaya is empty of real data.
The temperature trends (Max/Min) for weather stations with records extending back to the early 1960s are shown in Figure 2 of the paper (reproduced below with a red H next to the 5 Himalayan stations-click to enlarge).
We extracted figures for the Himalayan stations and reproduce them in the chart below. It also shows the trend cited by the IPCC of 0.09º C.yr-1 in red.
It’s quite clear the trends of the actual data across the entire record do not support the figures produced in Shrestha’s Kriging analysis, which is limited to 1977-1994. The temperature trends for the Himalayan stations are as follows:
|Station||Max ºC.yr-1||Min ºC.yr-1|
These trends, based on the reported station data, are much lower than the trends reported by Shrestha et al., 1999 and do not appear in any way unprecedented or alarming. The absence of data in the Western Himalaya invalidates the Kriging Analysis (you can’t interpolate into a data void), combine this with the crime of cherry picking recent trends to confuse weather with climate and a big part of the IPCC’s fragile tapestry of dangerous man made global warming suddenly falls through your fingers. All thanks to a loose thread revealed by the ABC.