By Ric Horobin and Xin Qiu
Often, the scientific assessment of climate change scenarios seems to be carried out separately from an assessment of the local impact that will be felt, and in many places is already being felt, as a result of a warming world. This is particularly true in large parts of northern Canada that are warming faster than other parts of the planet.
The question around climate change is most often that of what we need to do to reduce emissions of greenhouse gases. That is an important question to ask. Less often is the question posed as to what we can do to try to solve some of the problems that already exist.
While this may be less of an existential question, it is still a question that needs addressing, because the impacts at a local level are sometimes several stages removed from the direct effect of a warming climate.
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As an example of this, melting permafrost has the potential to release methane, a powerful greenhouse gas, into the atmosphere, further enhancing man-made climate change. However, the impact of melting permafrost is already being seen on ground engineering where foundations are no longer able to support buildings and roads are damaged as a result of the changing ground conditions.
SLR Consulting have been working on this problem for several years now. Dr. Xin Qiu has been modelling the likely impact of a warming climate on a variety of different issues, from mine tailings dam stability to the development of a new building code for Ontario. Dr. Ric Horobin has been developing engineering strategies to deal with the effects of a changing climate on ground stability and groundwater movement.
Climate models are based on well-documented physical processes to simulate the transfer of energy and materials through the atmospheric system. Climate models, also called general circulation models (GCMs), use mathematical equations to describe how energy and matter interact in different parts of the ocean, atmosphere and land. Establishing and running a climate model is a complex process of discovering and quantifying Earth system processes, representing them with mathematical equations, setting variables to represent initial conditions and subsequent changes in climate forcing, and repeatedly solving the equations using powerful supercomputers.
Once a climate model can perform well in hind-casting tests, its results for simulating future climate are also assumed to be valid. To project climate into the future, the climate forcing is set to change according to a possible future scenario. Scenarios are possible stories about how quickly human populations will grow, how land will be used, how economies will evolve, and the atmospheric conditions (and, therefore, climate forcing) that would result for each storyline.
In 2013, climate scientists under the Intergovernmental Panel on Climate Change agreed upon a new set of climate forcing scenarios that focused on the level of greenhouse gases in the atmosphere in 2100. Collectively, these scenarios are known as representative concentration pathways or RCPs. Each RCP indicates the amount of climate forcing, expressed in Watts per square metre that would result from greenhouse gases in the atmosphere in 2100.
Around the world, different groups of scientists have built and run models to project future climate conditions under various scenarios for the next century. The model results demonstrate that global temperatures will continue to increase, but show that human decisions and the behaviour we choose today will determine how dramatically climate will change in the future. The latest, internationally contributed GCMs and their output are organized by CMIP 5 and 6 (Coupled Model Intercomparison Project Phase 5 and 6 (ongoing)), under the World Climate Research Programme.
GCMs are the best tools for computing future temperature, wind and precipitation (or other climatological variables), but their limitations do not let them calculate local details for these quantities. Teams of scientists around the world develop various climate downscaling to address the issues from GCMs. Based on these, downscaling makes use of systematic dependencies between local conditions and large-scale ambient phenomena, in addition to including information about the effect of the local geography on the local climate.
For example, the Pacific Climate Impacts Consortium and the Ontario Climate Data Portal provide practical information on the physical impacts of climate variability and change in Ontario, the Yukon, and the Pacific regions of Canada.
One of the primary effects of climate change is the disruption of the water cycle. Since so much of everyday life and planning is determined by hydrological systems, it is important to understand the impact that climate change is having (and will have) on water supplies, infrastructure, food and energy production.
Increased variability in precipitation and more extreme weather events caused by climate change can lead to longer periods of droughts and floods, which directly affect the availability of, and dependency on, surface and groundwater. In northern regions, climate change impact is much more significant.
Permafrost covers about 24% of the exposed landmass of the Northern Hemisphere – about 9 million square miles. It is found at high latitudes and high altitudes, mainly in Siberia, the Tibetan Plateau, Alaska, Northern Canada, Greenland, and parts of Scandinavia and Russia. The continental shelves below the Arctic Ocean, which were exposed during the last ice age, also contain permafrost.
However, polar and high-altitude regions are some of the most climate-sensitive places on the planet. The Arctic is warming twice as fast as the rest of the planet, at a rate of temperature change that has not been observed in at least the last 2,000 years, according to the National Oceanic and Atmospheric Administration. In 2016, annual average surface temperatures were 3.5°C warmer than they were at the start of the 20th century. Permafrost temperatures in the Arctic were the warmest ever recorded.
A good example of the real-world practicalities of a changing climate is the impact on ground engineering. A reduction in the effectiveness of building foundations has been seen in the northern cities, particularly in Russia. Buildings once considered stable are starting to subside as a result of melting permafrost. This is not a new problem as can be seen from subsidence of historic buildings constructed in Dawson City, Yukon Territory.
Many new engineering projects are required to be designed to withstand the impact of climate change. Without a clear assessment of the link between the GCM outputs at a global level and the impacts observed at a local level, designers often take a precautionary approach and over-design and hence over-engineer, with the resultant increase in cost and use of resources.
Another example that requires additional research is the field of water resources. In many parts of the world, glacial ice provides a slow release of long-term water storage during dry summer months. Without this store of water, river flows are reliant on annual snow melt and rainfall, both of which cannot necessarily be relied upon throughout the year. This results in rivers that are more prone to rapid rises and falls in their flow rate and, therefore, they are less reliable as a source of water for communities, towns and cities downstream.
This has been well documented in the Himalayas in northern India and Nepal, but there is also risk in parts of Canada where groundwater resources, which are used for water supply, are fed partly by river flow, which in turn relies on glacial meltwater for its regular supply throughout the year. Recent research has shown that the depth to the water table can have a significant impact on heat fluxes across the land surface, which in turn suggests a strong linkage between the climate system and groundwater.
Physically-based, fully-integrated surface/subsurface models have only recently emerged and more research is needed in order to be able to adequately address the real and potential impacts.
Our role as scientists and engineers must be to advance not only understanding of the climate system at a global level, but to bring together experts from different areas in order to address the impacts, real and predicted, at a local level.
Dr. Ric Horobin and Dr. Xin Qiu are with SLR Consulting (Canada) Ltd. This article appears in ES&E Magazine’s February 2020 issue.