With glaciers melting, sea level rising and extreme weather events ravaging the globe, the first thing that comes to a scientist’s mind is to take the Earth’s temperature. Just like your body temperature can reflect your state of health, the Earth’s temperature is a vital sign for the Planet.

 

You don’t need to measure your entire body to get a sense of how sick you are. Scientists are the same. They won’t – they can’t – measure every inch of our planet for temperature. Traditionally, physicians would put a thermometer under your armpit or in your mouth, wait for a few minutes and then get a reading. Taking the Earth’s temperature, however, is a very different story.

 

For starters, scientists do not know where the Earth’s “armpit” or “mouth” is. They first have to  figure out which parts of the Earth are most sensitive to environmental changes so that they can check for anomalies. But lucky for us, they have already found them. 

 

Three places stand out as scientists study Earth’s past climate: the Arctic, the Antarctic, and the Tibetan Plateau-centered Third Pole. All three are warming almost twice as fast as the global average [1-4].

 

Temperature readings from the Arctic and the Antarctic are relatively straightforward. They have fairly even surfaces covered by ice and snow, so the temperature doesn’t change much across the terrain. The Third Pole, on the other hand, is much trickier, due to its high mountains and range of landscapes. The zig-zag roads, steep slopes, glistening glaciers, extensive grasslands and forests, and mountain-top snow all complicate things greatly. Since temperature can vary dramatically from place to place, average temperature can’t always tell us what is actually going on across the Third Pole, especially when we don’t have readings from higher elevations. It is even possible that in some far corner of the Tibetan Plateau the temperature has already gone through the roof and we just don’t know it yet.

 

Since studying the Third Pole is so complicated, why don’t scientists just focus on data from the Arctic and Antarctic to make a “diagnosis”? The problem is that without Third Pole data, a global misdiagnosis is much more likely, thus leading to grave outcomes.

 

With numerous glaciers and lakes, the Third Pole is known as the Asian Water Tower. It has nourished local communities with fresh water for thousands of years. If temperature changes in this region are not properly examined, Asia’s water supplies can be threatened [5]. Just imagine what a dysfunctional water tower would do to local communities? It would be as bad as dehydration for a human body.

 

For this reason, TPE scientists have been working to “take the temperature” of the Third Pole since the 1970s. YAO Tandong, co-chair of Third Pole Environment(TPE) and professor at the Institute of Tibetan Plateau Research (ITP), Chinese Academy of Sciences(CAS), identified a climate pattern based on changes observed so far. He determined that the Third Pole can be divided into three regions: one dominated by the summer monsoon, one dominated by westerly winds, and a third area in between[6]. 

  

 

 

 

Such a climate pattern can be very handy when it comes to measuring temperatures on the Third Pole. As Dr. Dambaru Ballab KATTEL, a Nepalese scientist working at ITP, explained, “Temperature variability depends on local and regional climatic processes. Understanding regional patterns can shed light on why the southern and the northern slopes of the Himalayas might respond so differently to the greenhouse warming effect.”[7] Warming has indeed been felt differently across the Third Pole. Generally, the magnitude of climate warming increases from south to north; the most significant warming has been found in the northern part of the Third Pole [8-10].

 

Warming also acts differently at different elevations. Dr. Nicholas PEPIN, reader at the University of Portsmouth, spent years studying how temperature varies with elevation in high mountain regions around the world, including the Third Pole. He observed that evidence already exists that the rate of warming can be more at high elevations, such that high-altitude environments often experience more rapid changes in temperature than lower ones. This phenomenon, known as Elevation-Dependent Warming (EDW), has been detected at the Third Pole [11] and has been corroborated by ice core studies [12] (see “What Does the Ice Say?”)

 

Dr. Pepin noted that understanding the effects of global warming at high elevations on the plateau is critically important, because most of the region’s snow and ice are there. “Changes in these mountain snow reserves are critical for the supply of water to billions of people in both China and India, and they are threatened by climate change,” said Dr. Pepin.

 

Using a customized model based on satellite data, Dr. Pepin and his team found a marked spike in warming rates around 5000-5500 m in the Nyenchen Tanglha Mountains, one of the major ranges in the centre of the plateau. This warming is particularly strong during the day. The disappearance of snow cover is the most obvious reason for this increased warming.

 

“Snow reflects sunlight during the day,” said Dr. Pepin. “So when it is reduced it causes even more warming, especially at the height where it is disappearing fastest.” Increased warming also happens at night, but more broadly at higher altitudes (up to 6500 m). Scientists attribute this warming to changes in both cloud patterns and moisture. [13].

 

Understanding warming trends at the Third Pole requires a larger surface climate observation network, especially in data-poor areas like the western Tibetan Plateau, said Dr. Pepin. He also noted that data besides temperature should be collected. He suggested that additional data, including rainfall, snowfall and measurements of sunlight and cloud patterns, would help explain how the Third Pole’s climate is changing. This proposal is echoed by Yao, who spearheads Pan-TPE and the Second Tibetan Plateau Scientific Expedition and Research (STEP), both major TPE-related science projects that are planning to expand observation networks in order to increase scientific understanding [5]. 

 

The ambition of TPE scientists does not stop here, however. Connections are being drawn between the North Pole (the Arctic), the South Pole (the Antarctic) and the Third Pole. “The Three Poles have a lot in common. Located in a densely populated region, the Third Pole serves as a natural laboratory for examining interactions between air, water, land, ecology and human activities, as well as their socioeconomic impacts. Findings based on the Third Pole can benefit research on the other two Poles as much as the other way around,” said Yao.

 

As knowledge about the Three Poles comes together, scientists are better able to take the Earth’s “temperature.” In doing so, we are another step closer to a full diagnosis of the planet’s ills and therefore the day when we can take appropriate action to help heal our planet.

 

 

References

 

1. Bromwich, D.H., et al., Central West Antarctica among the most rapidly warming regions on Earth. Nature Geoscience, 2013. 6(2): p. 139-145.

2. Steig, E.J., et al., Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year. Nature, 2009. 457(7228): p. 459-462.

3. Jones, P., et al., Hemispheric and large‐scale land‐surface air temperature variations: An extensive revision and an update to 2010. Journal of Geophysical Research: Atmospheres, 2012. 117(D5).

4. Yao, T., et al., Recent Third Pole’s rapid warming accompanies cryospheric melt and water cycle intensification and interactions between monsoon and environment: Multidisciplinary approach with observations, modeling, and analysis. Bulletin of the American Meteorological society, 2019. 100(3): p. 423-444.

5. Gao, J., et al., Collapsing glaciers threaten Asia’s water supplies. 2019, Nature Publishing Group.

6. Yao, T., et al., A review of climatic controls on δ18O in precipitation over the Tibetan Plateau: Observations and simulations. Reviews of Geophysics, 2013. 51(4): p. 525-548.

7. Kattel, D.B., et al., Comparison of temperature lapse rates from the northern to the southern slopes of the Himalayas. International Journal of Climatology, 2015. 35(15): p. 4431-4443.

8. Yang, K., et al., Response of hydrological cycle to recent climate changes in the Tibetan Plateau. Climatic change, 2011. 109(3-4): p. 517-534.

9. Chen, H., et al., The impacts of climate change and human activities on biogeochemical cycles on the Q inghai‐T ibetan P lateau. Global change biology, 2013. 19(10): p. 2940-2955.

10. You, Q., et al., Observed trend of diurnal temperature range in the Tibetan Plateau in recent decades. International Journal of Climatology, 2016. 36(6): p. 2633-2643.

11. Pepin, N., et al., Elevation-dependent warming in mountain regions of the world. Nature climate change, 2015. 5(5): p. 424-430.

12. Thompson, L.G., et al., Ice core records of climate variability on the Third Pole with emphasis on the Guliya ice cap, western Kunlun Mountains. Quaternary Science Reviews, 2018. 188: p. 1-14.

13. Pepin, N., et al., An examination of temperature trends at high elevations across the Tibetan Plateau: The use of MODIS LST to understand patterns of elevation‐dependent warming. Journal of Geophysical Research: Atmospheres, 2019. 124(11): p. 5738-5756.