January 24, 2008

Tibet’s Temperature Story

Hardly a week goes by without some story hitting the news about global warming and retreating glaciers, and for whatever reason, retreating glaciers in the Himalayan region get more than their fair share of coverage. The recent death of Sir Edmund Hillary served to further focus attention on this part of the world.

There are absolutely countless websites on the subject, and one of the first you will encounter for a “Global Warming Himalayan” search shows the map below (Figure1) from www.climatehotmap.org with tabs than can bring you all the news from the region.


Figure 1. Map showing global warming footprint regions from www.climatehotmap.org

Here are a few examples of what you will find behind the numberd tabs:

1. Llasa, Tibet — Warmest June on record, 1998. Temperatures hovered above 77°F for 23 days.
59. Garhwal Himalayas, India — Glacial retreat at record pace. The Dokriani Barnak Glacier retreated 66 ft (20.1 m) in 1998 despite a severe winter. The Gangorti Glacier is retreating 98 ft (30 m) per year. At this rate scientists predict the loss of all central and eastern Himalayan glaciers by 2035.

91. Nepal - High rate of temperature rise. Since the mid-1970s the average air temperature measured at 49 stations has risen by 1.8°F (1°C), with high elevation sites warming the most. This is twice as fast as the 1°F (0.6°C) average warming for the mid-latitudinal Northern Hemisphere (24 to 40°N) over the same time period, and illustrates the high sensitivity of mountain regions to climate change.

95. Tibet - Warmest decade in 1,000 years. Ice core records from the Dasuopu Glacier indicate that the last decade and last 50 years have been the warmest in 1,000 years. Meteorological records for the Tibetan Plateau show that annual temperatures increased 0.4°F (0.16°C) per decade and winter temperatures increased 0.6°F (0.32°C) per decade from 1955 to 1996.

126. Bhutan - Melting glaciers swelling lakes. As Himalayan glaciers melt glacial lakes are swelling and in danger of catastrophic flooding. Average glacial retreat in Bhutan is 100-130 feet (30-40 m) per year. Temperatures in the high Himalayas have risen 1.8°F (1°C) since the mid 1970s.

127. India - Himalayan glaciers retreating. Glaciers in the Himalayas are retreating at an average rate of 50 feet (15 m) per year, consistent with the rapid warming recorded at Himalayan climate stations since the 1970s. Winter stream flow for the Baspa glacier basin has increased 75% since 1966 and local winter temperatures have warmed, suggesting increased glacier melting in winter.

130. Mt. Everest - Retreating glacier. The Khumbu Glacier, popular climbing route to the summit of Mt. Everest, has retreated over 3 miles (5 km) since 1953. The Himalayan region overall has warmed by about 1.8°F (1°C) since the 1970s.

Very interesting and potentially effective to say the least, but an article forthcoming in the peer-reviewed scientific journal Theoretical and Applied Climatology tells a very different story – and a story that will not be featured anywhere but World Climate Report. The research was conducted by scientists from various Chinese institutions, Columbia University, and the University of Delaware; the work was funded by National Natural Science Foundation of China.

The Gou et al. team took 139 tree ring cores from 97 trees located in the valley of Qiemuqu in the Animagin Mountains in the northeastern Tibetan Plateau; you all realize from your geography classes that this valley produces a major headwater tributary of the Yellow River. They found that the tree ring widths were very highly correlated with summer maximum air temperatures in the region (the trees love cool summers), and this allowed for a surprisingly accurate way to reconstruct temperatures back 700 years. A bit of statistical wizardry was then applied to produce Figure 2 below.


Figure 2. Reconstructed maximum air temperature of the headwater area of Yellow River over the past 700 years. The 11-year moving average (imposed solid black line), and average air temperature (straight line) are depicted for reference (from Gou et al., 2008)

In their own words, Gou et al. observe “The ten-year average summer half-year maximum temperature in the 1990s is relatively high, but it is still colder than several other periods, including 1480s–1490s and 1590s–1600s. The 1480s is the warmest period in the past 700 years. The summer half-year maximum temperature can change significantly within decades.”

Even more amazing, with respect to all the material we see on the internet is their finding that “There is no warming trend for the reconstructed summer half-year maximum temperature since the Industrial Revolution in the northeastern Tibetan Plateau.” Further, we learn “The summer half-year maximum temperature in the northeastern Tibetan Plateau has increased since the 1980s, but it is not exceptional on centennial or millennial timescales. The ten-year average summer half-year maximum temperature in the 1990s was relatively high, but was still colder than several other periods.” You undoubtedly see now why this article will be immediately dismissed by the global warming crusade.

We will leave you with this exact quote, because it speaks volumes as they so clearly state

“There is no warming trend since the Industrial Revolution, in fact, the linear trend is negative.”

Reference:

Gou, X; J. Peng, F. Chen, M. Yang, D.F. Levia, and J. Li. 2008. A dendrochronological analysis of maximum summer half-year temperature variations over the past 700 years on the northeastern Tibetan Plateau. Theoretical and Applied Climatology, DOI 10.1007/s00704-007-0336-y.




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