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Tuesday, Apr 02, 2019

Climate Change Conversations - Considering climate change at the local scale

In the previous Climate Change Conversations, we described how we know with confidence that human activity is driving ongoing climate change, and how this change will accelerate in the future.  In this edition, we will explore what this change means for climate at the local scale, how it relates to natural weather patterns, and how it can be integrated into engineering design.

Climate Change Conversations

What climate change metrics matter at the local scale? 
Often climate change is described in climate science reports and the media as changes in broad statistics like ‘annual average precipitation’, ‘global average temperature’, or ‘global sea level rise’.  But for engineers, what may matter even more are changes to infrequent or ‘extreme events’ at the local scale.  This is because these types of statistics often relate to project-specific engineering design values or targets.  Examples of such statistics that we often encounter include changes to the return periods of more frequent and higher intensity rainfall events, increases in the magnitude of hot summer days, or maximum run-up heights of ocean storm surge events.  

Climate Change Conversations

What factors need to be considered in assessing local climate change? 
Changes to extreme events combine the signal of natural weather fluctuations with the underlying ‘push’ of climate change.  For example, understanding climate-driven ocean storm surge run-up changes requires consideration of the natural processes that cause storm surges, such as local winds and barometric pressure, and the underlying signal of increasing water levels from human-caused glacier melting and ocean thermal expansion.  Additionally, unique regional natural and built conditions are also factors to consider; for example, vertical land motion due to regional geologic processes will play an important additional role in determining future Canadian coastal storm surge severities. Identifying these unique conditions brings local expertise into play and is critical for translating climate data into engineering design and analysis.

Climate Change Conversations

How can climate-driven changes to extreme events be reflected in engineering design?
It is difficult, although increasingly possible, to claim that aspects of individual extreme events, such as a particular storm surge, directly result from climate change and not simply natural weather fluctuations. Instead, it is more appropriate to identify changes to the average magnitude or frequency of occurrence of such events.  Fortunately, many engineering design thresholds related to environmental conditions are also described in terms of average magnitudes or frequencies of occurrence.  This simplifies the workflow for integrating climate change information into engineering design!  For example, 1:100 year magnitudes of projected future storm surge run-up heights could be used in coastal infrastructure design in lieu of past observed historical 1:100 year storm surge observations.  In this sense, providing an appropriate Standard of Care for clients will, in part, involve integrating the statistics of tomorrow’s extreme events into today’s engineering design.

For more information, contact Dr. Jeremy Fyke.