There is a growing amount of evidence that climate change is occurring during our lifetimes and that human activities, principally the combustion of fossil fuels, is the driving force. The media has disseminated a large amount of information, much of which is unsubstantiated, leading to diverse anecdotal and speculative opinions. Our role as engineers compels us to understand this potentially serious issue, and to respond appropriately. Engineers need to understand the physical realities of the changes we are facing in order to accept their role of assisting communities to adjust and adapt.
The earth is getting warmer. The global mean surface air temperature increased by about 0.6 degrees Celsius (1.1 degrees Fahrenheit) between 1970 and 2010. The last 12 years have been the warmest, on a global average, since 1880, according to data from the Goddard Institute for Space Studies (http://data.giss.nasa.gov/gistemp/graphs_v3/). The concentration of CO2 in Earth’s atmosphere has increased from about 340 parts per million in 1980 to over 390 today, primarily due to the burning of fossil fuels. Other gases produced by human activities, including methane, fluorinated gases, and nitrous oxide — much of which is caused by human activities — are more potent "greenhouse gases" than CO2, according to the National Oceanic and Atmospheric Administration’s Earth Systems Research Laboratory, Global Monitoring Division (www.esrl.noaa.gov/gmd/outreach/index.html). The U.S. emits more anthropogenic CO2 than any other country except China, putting out about three times the CO2 emitted per person as China, according to The World Bank (http://data.worldbank.org/indicator/EN.ATM.CO2E.KT/countries).
The great majority of climate scientists believe that 350 parts per million is what many scientists, climate experts, and progressive national governments are now saying is the safe upper limit for CO2 in our atmosphere. Accelerating Arctic warming and other early climate impacts have led scientists to conclude that we are already above the safe zone at our current 390 ppm, and that unless we are able to rapidly return to below 350 ppm this century, we risk reaching tipping points and irreversible impacts, such as the melting of the Greenland ice sheet and major methane releases from increased permafrost melt.
Warmer air holds more moisture. The atmosphere holds about 4 percent more water vapor than it did 30 to 40 years ago, according to the paper "Atmospheric Humidity" by Dr. Katharine Hayhoe, Texas Tech University. This means there is more water for storms to pick up and deposit, which has likely been the cause of an increase in severe storms and flooding in recent years. This trend, coupled with a significant rise in sea levels, will likely continue and worsen over the next several decades.
What’s a structural engineer to do? Plenty.
If we do not respond, the hell-in-a-handbasket scenario will likely become our reality within a generation or so. Continuing on our current path of energy- and resource-intensive transportation, housing, and commerce without regard for the effect on the atmosphere will lead to a future I don’t think any of us would want to witness. If we face this challenge as engineers have faced challenges in the past, there is a plethora of things we can do to mitigate climate change.
The fabrication and erection of structural elements, especially concrete, steel, and masonry, cause a large amount of CO2 to be emitted into the atmosphere. Plus, the energy used in the buildings and projects we design has a large, extended carbon footprint over time. All engineers, including structural, need to be aware of what tools they can use, and conversely, what impacts they are having within the current status quo. To find out more, sign up for the 2013 Structures Congress Pre-Conference Seminar activities and learn how to grow your "sustainability tool kit" by participating in a series of sessions presented by the SEI Sustainability Committee.
If we do not respond, the hell-in-a-handbasket scenario will likely become our reality within a generation or so.
Additionally, the SEI Sustainability Committee (www.seisustainability.org) has working groups that are developing strategies to assist the practicing structural engineer in the following ways:
- Inform yourself of the carbon footprint of your designs. The Carbon Working Group has produced a paper that’s a good place to start. See Structural Engineer, February 2013.
- Make your structures last. The Design for Durability Working Group is developing information about improving the longevity of structures. The longer our buildings and infrastructure elements are in service, the later they will need to be replaced with carbon-intensive replacement projects.
- Find out how lifecycle assessment (LCA) can benefit design and what lessons the industry has learned from the LCA work that has been done so far. The LCA Working Group will be publishing "Top 10 LCA FAQ’s" on the SEI Sustainability website soon. Stay tuned.
- Do your part to minimize energy use in buildings. The Thermal Bridging Working Group and Task Committee has developed some guidelines for steel details and is working on a more comprehensive document to minimize thermal losses caused by all structural building systems that intersect insulated building envelopes.
- The engineering community also needs to focus on adaptation of designs to sustain larger storm forces, higher water levels in coastal communities, and other loading and exposure changes that the changing climate will bring upon us. Some of these changes are already here. This is the focus of the Disaster Resilience Working Group.
Finally, many people believe that "geo-engineering" — deliberate schemes to reduce solar gain or to capture atmospheric carbon dioxide in order to reverse the effects of global warming — will solve the problem; so, not to worry. However, putting trust in such large-scale, untested experimentation on the fragile balance of our planet is an extremely risky proposition. The ideas are numerous, some with the possibility of making real improvement. A false belief in yet-to-be-proven concepts has led some to the dangerous position that someone else, somehow and somewhere, will solve this problem for us. Look harder at these schemes, including their costs, to see whether they really make sense, before building up false hopes.
The time for disbelief, ignorance, and denial of U.S. citizens is past. The world does not need our pessimism, nihilism, aloofness, or detachment. It needs, and deserves, our engagement, our intelligence, and our creativity. In short, the situation compels us to be engineers.
James A. D’Aloisio, P.E., SECB, LEED AP BD+C is a principal with Klepper, Hahn & Hyatt of East Syracuse, N.Y., and chair of the Structural Engineering Institute’s Sustainability Committee. He can be reached at firstname.lastname@example.org.