The importance of solar insolation on temperature variations for the past 110 kyr on the Chinese Loess Plateau

The Chinese Loess Plateau is a large source of agriculture and home to the Yellow River, and thus plays an important role in Chinese civilization. Understanding how weather patterns and climate change affect the area is key to being able to prevent any major changes in the future. Since the 1960s data have been compiled on the monsoon patterns in the area, however there are few data on temperature changes. This gap is important to close if models and complete records are to be produced. Gao et al. (2012) collected temperature proxies in the Lanjian region of the Loess Plateau, using tetraether lipids from bacteria. Their findings suggest that insolation is the main driver behind temperature changes for the past 110 thousand years (ky). Their data records match up with other local records, as well as with global forcing records. The data the authors compiled will aid in creating more accurate models for understanding possible affects of climate change on the Loess Plateau. –Mathew Harreld
Gao, L., Nie, J., Clemens, S., Liu W., Sun, J., Zech, R., Huang, Y. 2012. The importance of solar insolation on temperature variations for the past 110 kyr on the Chinese Loess Plateau. Palaeogeography, Palaeoclimatology, Palaeoecology 317–318, 128–133.

            Local and global monsoon patterns are important indicators of climate shifts. On the Chinese Loess Plateau there are some of the best archives of monsoon profiles in the world, allowing scientists to recreate the East Asian Monsoon pattern for the past few million years. This information allows for the recreation and understanding of past local and global climates. Furthermore, the data collected have important implications for predicting future monsoon rainfall variations, especially in global warming scenarios. The Chinese Loess Plateau has a rich archive of surface soil magnetic properties, oxygen–18, and grain sizes, which all contribute to creating rainfall records. Because of the abundance of these proxies the rainfall patterns in the Chinese Loess Plateau are well understood. However, the temperature variations throughout the same periods are not very well documented. Gao et al. attempt to address the issue of missing temperature data by using tetraether lipids from bacteria in conjunction with known climatic forcings. Temperature plays one of the most important roles in understanding a climate, through the use as the primary source to parameterize climate models, through its influence on other proxies, and through its insight on local mountain glacier activities.
            Gao et al. compiled data from the Lantian region of the Chinese Loess Plateau. To optimize their data’s accuracy they compared it to recently published, high-resolution data sources. The differences between their data and the other sources are mostly due to general location, and thus different weather affects, and different modelling techniques.
            Variation in the Lantian region’s temperature matches closely with Northern Hemisphere absolute insolation maximum at 35°N. Thus, it seems likely that the insolation forcing of the sun and earth’s orbit drives temperature changes in this region. Maximum (94, 72, 22.5 ka) and minimum (105, 81, 58, 10.8 ka) insolations match with Lantian temperature maximum and minimum. The authors propose that insolation has such a large impact because of the postive feed back loop of monsoon intensities being increased greatly by high summer insolations, which then trap more heat, resulting in even higher temperatures. However, increased monsoon strength does not always occur along with higher temperatures because changes in insolation strengths don’t match up with monsoons changes.
            Another potential influence on temperature is changes in atmospheric CO2 levels. Increased temperatures coincide with high CO2 levels, and vice versa. This is to be expected on larger time scales, however on the short term it is more difficult to get a accurate understanding. The results found by Gao et al. further suggest the relationship between CO2variation and large scale temperature variations on the Chinese Loess Plateau.
            Glacial records from the nearby Tibetan mountain ranges show maximum local glacial advance earlier than global values. This is fairly common throughout the world, and is most likely due to abundant moisture availability and local cold temperatures. And the data compiled by the authors is consistent with other data compiled in the region. Furthermore, the lowest temperatures in the record are around 30 and 22.5 ka, which designates the local last glacial maximum. Temperatures increased rapidly from 22.5 ka years on, increasing about 9°C. This warming in earlier than global values, but this is also not unusual for local climates.
            Compiling a record of temperatures in the Lanjian region will greatly enhance understanding of monsoon changes in the past, as well as aiding in creating climate models for the region so we can begin to better understand future changes under climate change. It is clear that insolation is the main drive in temperature change in the Chinese Loess Plateau, and therefore any insolation maximum combined with monsoon changes and other climate change effects might vastly change the Chinese Loess Plateau region.

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