KARACHI: The year-wise data covering more than four centuries of temperature in Gilgit and Hunza has been recently traced in a study that also shows the occurrence of ‘Little Ice Age’.

The study is said to be the first of its kind in Pakistan.

Titled Climatic History of Gilgit and Hunza (a dendroclimatic approach), the study was conducted by Mohammad Usama Zafar of Laboratory of Dendrochronolgy and Plant Ecology, Department of Environmental Sciences, Federal Urdu University of Arts, Science and Technology.

Prof Moinuddin Ahmed, the pioneer of dendochronology (study of tree rings) in Pakistan, had supervised the research under which tree ring chronologies of a conifer species, Morinda spruce or west Himalayan spruce (scientifically named Picea smithiana), found at altitudes of 2,400 to 3,600 metres in Gilgit and Hunza were studied to reconstruct mean March-June (spring) temperatures from the year 1523 to 2008.

Earlier, Prof Ahmed along with his team had successfully reconstructed past 500 years flow of the Indus river at Partab bridge with the help of tree ring chronologies. Both projects were funded by the Higher Education Commission.

According to findings of the climatic history study, the warmest periods occurred in the second half of the 18th century (roughly concurrent with the large mega droughts noted for Southeast Asia and beyond) and the very last and early periods of 19th and 20th centuries, respectively. The coldest periods were observed for the 1660s, 1780s and 1910s.

The distinct cold and warm intervals seen from the current investigation, the study says, included the “Little Ice Age”. The 17th century, it says, appeared to be cooling whereas the 19th century recorded a prolonged warm period including the last two decades of 18th century and the first decade of 20th century.

The “Little Ice Age”, the study says, could also be observed from the reconstruction and matched with the reported cooling intervals of National Aeronautics and Space Administration (NASA).

Citing data from NASA, it says the US institution describes the occurrence of “Little Ice Age” in three particularly cold intervals: 1650s, 1770s and 1850s which spread throughout Europe, North America and Asia.

“The above periods were marked for the expansion of mountain glaciers. These periods were also witnessed where we have the coolest period with the highest departures from the mean temperature. The warmest period of the last millennium (medieval warm period) could not be investigated as the reconstructed data was too short. Some studies show that this warm period occurred before the occurrence of Little Ice Age,” it says.

Explaining how the study was done, Mr Zafar said a simple linear regression technique was used to convert the data acquired from the trees in the Gilgit and Hunza valleys into temperature data.

“Similar studies have been conducted in India and China but it’s the first time that such a study has been carried out in our country. I have also taken assistance from US researchers and expecting that my paper would be published in a US journal soon,” he said.

According to him, the consistency observed on decadal scales between the present reconstruction of March-June temperatures, the mean temperatures of April-May reconstruction from the valley of Kashmir (done by a scientist in 1992 and then in 1994) and the mean temperature reconstruction of April-May in the Western Himalaya of India (conducted by another scientist in1997) indicates the potential for reconstructing regional-scale climatic changes using tree rings.

To a question about possibilities of expanding this work to other areas of Pakistan, Mr Zafar said: “Globally, such researches are conducted only in those areas where one could find trees that have a long life spanning thousands of years and, hence, provide strong tree-ring data. Such trees are usually found on high altitudes.”

During his research, he was saddened to find that many old conifer trees were being rapidly cut illegally. “We have limited areas with old conifer trees that are already under stress due to changing climatic conditions. It is unfortunate that we are fast losing not only this precious asset but also the wonderful opportunity to research and explore past climates,” he said.

Highlighting significance of the research, Prof Ahmed said that such researches could provide a basis to predict future climatic conditions that posed grave threat to Pakistan. “But you need to expand the data to up to a millennium. The more you travel into the past, the chances of getting more accurate data increases,” he explained, adding the government needed to provide funds to carry more detailed work.

Tree-ring research (dendochronology), he said, had various applications in fields such as ecology, climatology, hydrology, archaeology, seismology and glaciology. It had also been successfully used for management of water resources and to prepare a better response to natural fluctuations in river flows, most crucial of them were drought conditions, he added.

“The annual growth rings formed in the trunks of some trees recorded the effects that occurred due to climatic, hydrologic and soil conditions. The normal patterns show certain variations. The selection of site and tree species depends on the nature of the study.

“For instance, six conifer species in northern Pakistan are found to have the best prospects for tree-ring research. The species are Cedrus deodara, Pinus gerardiana, Picea smithiana, Pinus wallichiana, Juniperus excelsa and Abies pindrow,” he said, adding that sites for studies relating to climatic reconstruction and river flow variation differed.

Published in Dawn December 11th , 2014