Professional issues issues affecting the structural engineering profession
Figure 1: U.S. Average Temperature Projections (draft NCA 2013).
W
eather, climate and extreme events are key considerations in structural engineering design and practice. Weather is defined as “the state of the atmosphere with respect to wind, temperature, cloudiness, moisture, pressure, etc.” (NWS, 2013). Weather generally refers to short-term variations on the order of minutes to about 15 days (NSIDC, 2012). Climate, on the other hand, “is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years” (IPCC, 2007). An extreme event is a weather event that is rare at a particular place and time of year (IPCC, 2007). For instance, at Washington Reagan National Airport on June 25 (Washington Post June 26, 2013), the normal high temperature is 87°F (climate), the high in 2013 was 93°F (weather) and the record high was 100°F in 1997 (extreme event). Scientists have reached a consensus that weather, climate and extreme events of the past generally will not be representative of those of the future. Moreover, climate science is not able precisely to forecast the climate, weather and extreme events of future decades. This poses a challenge to structural engineers whose design standards are based on the assumptions of stationary climate, weather and extreme events as observed in the past. The Committee on Adaptation to a Changing Climate (CACC) of the American Society of Civil Engineers (ASCE) is addressing this in its white paper, Bridging the Gap between Climate Change Science and Civil Engineering Practice (ASCE 2013). The purpose of this article is to alert structural engineers to this challenge,
inform them of the guidance available from the white paper, and invite their participation in the profession’s response to the challenge.
Bridging the Gap between Climate Change Science and Structural Engineering Practice
Current Climate Science The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for the assessment of climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts. The Table (page 30) shows the recent, qualitative IPCC assessment, based on observations and global climate models, of future weather and extreme events relevant to structural engineering design (IPCC 2012). The U.S. Global Change Research Program (USGCRP) involves thirteen federal agencies and is led in the White House Office of Science and Technology Policy. USGCRP is preparing a National Climate Assessment (NCA), which will be issued in 2014; a draft has been available since January 2013 (NCA 2013). The draft NCA was prepared by the National Climate Assessment and Development Advisory Committee involving over 240 authors, including climate and social scientists and engineers. It has chapters on urban systems, infrastructure and vulnerability, U.S. regions, mitigation and adaptation. Figure 1, U.S. Average Temperature Projections, taken from the draft NCA, illustrates both the
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By Richard N. Wright, Ph.D., P.E., Dist.M.ASCE, NAE, Bilal M. Ayyub, Ph.D., P.E., F. ASCE and Franklin T. Lombardo, Ph.D., M. ASCE
The online version of this article contains detailed references. Please visit www.STRUCTUREmag.org.
