Interrogating Past Climate Variations to Understand the Future Impacts of Climate Change

With the rapid development of modern society over the course of the past century, increased attention has been paid to the causes and impacts of climate change.  To increase our understanding of the range of potential variations of the climate system, researchers at St. Francis Xavier (StFX) University, are looking to the past to see how the system has responded to previous climatic variations. Such past climate information can then be used to ascertain the reliability of projections of future climate change from climate models.  The research program of Dr. Hugo Beltrami, Tier 1 Canada Research Chair in Climate Dynamics at StFX, examines the thermodynamics of land-surface models to identify better climate modeling practices based on accounting of measured continental heat.

Dr. Beltrami and his students use advanced computer modeling tools requiring significant computational capabilities to undertake this work.  Their research has been supported by the Canada Foundation for Innovation (CFI), as well as the Nova Scotia Research and Innovation Trust (NSRIT) to establish a dedicated competing cluster as part of the Atlantic Computational Excellence Network (ACENET).  This infrastructure is valued at almost $600,000 and includes a $216,000 contribution from both CFI and NSRIT.  The modeling tools employed in their research helps to study heat transfer phenomena near the ground that are feedbacks in the global climate system.

n the words of Dr. Beltrami, “Since we cannot travel back in time to make these observations ourselves and the global meteorological record extends back, at best, 150 years, climate scientists must rely on indirect measures of past climate”.  These indirect measures, which are commonly called paleoclimatic indicators are drawn from proxy data, such as tree-ring widths, pollen accumulation, and ice-cores.  Sources of information about past climatic changes also include the vertical variation of underground temperatures measured in mining exploration boreholes in continental areas.

It has long been known that temperatures in the first few kilometres of the Earth’s crust are significantly affected by the past surface conditions.  Changes in the long-term ground surface energy balance are recorded as underground climatic fingerprints.  These climate signals were originally found in temperature-depth profiles carried out by geophysicists studying the Earth’s internal thermal regime. While they were originally considered as noise, in the last few decades these subsurface climate signals have been isolated from the full profile and processed to infer ground surface temperature histories.

In a 2016 paper published in the PAGES Special Issue of the European Geophysical Union journal Climate of the Past, Dr. Beltrami and his collaborators performed a regional analysis of ground surface temperature histories for the past 500 years. Their results indicate that the average North American ground surface temperature increased about 1.8 °C over the past 200 years. However, although the warming is widespread and persistent, these temperature increases exhibit a wide range of spatial variability throughout North America. Reconstructed regional ground surface temperature mean trends for seven different climatic regions suggest a warming range variation of 0.5 to 2.0°C. Furthermore, geographical representations of regional variations revealed a warming range of 1 to 2 degrees Kelvin between 1780 and 1980, with all regions experiencing an increase in ground surface temperature, with warming more marked in Arctic regions.  Their work showed conclusively that the warming experienced by the planet globally is also well documented in the North American continental subsurface.  Furthermore, such warming shows no ambiguity in the last two centuries; the warming is persistent and widespread in North America, and is more significant in the Arctic.

These research results, along with other available long-term paleoclimatic records of climate change, have helped contribute to improving climate model simulations of present day climate dynamics and provide insights into the potential consequences of future climate change on society.

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