Technical Bulletins on Climate Adaptation in Civil and Environmental Engineering
ASCE Committee on Adaptation to a Changing Climate
Climate Adaptation Engineering Bulletin No.3 Documented Historic Indicators of Climate Change
Weather and climate, along with their extremes, are critical considerations in civil engineering design and practice. Much of the discussion of climate change in the broader media focuses on increases in global average temperature and its implications for energy policy. Conversely, civil engineers whose work focuses on project design and operations need to understand the broader changes observed in the geophysical systems associated with project risks. The purpose of this note is to provide practicing civil engineers with credible information about the complex response observed in the Earth’s many geophysical systems that may be relevant to their work.
Increases in the global mean surface air temperature (global warming) are measures of the change in total heat content of the Earth system. Associated changes in circulation in the ocean and atmosphere are driven by the need to redistribute heat from regions experiencing high levels of solar insolation (e.g., equatorial latitudes) to areas where solar insolation is lower (i.e., polar regions). Thus, increases in global mean temperature drive complex responses in ocean and atmospheric circulation which bring about changes in weather patterns (on short time scales) and other geophysical systems sensitive to temperature change (on longer time scales).
For engineering practice, understanding the drivers of climate variability and change is essential for assessing the persistence of trends and making projections.
In 2012, the International Panel on Climate Change (IPCC) released the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX)( https://www.ipcc.ch/report/srex/) . This report summarized observed and projected changes to physical impacts that could affect infrastructure globally. The findings of SREX were updated and largely confirmed by the IPCC in 2013 (AR5 Climate Change 2013: The Physical Science Basis — IPCC and again in 2022; AR6 Climate Change 2021: The Physical Science Basis — IPCC). The clear historical evidence of climate change is unarguable.
These reports document and assess findings from thousands of journal articles published over the last few decades, covering multiple aspects of Earth's climate. Thus, the IPCC concluded more than a decade ago that Earth's climate is changing in observable ways. They reported that global average temperature has increased since the late 19th century, with each of the previous three decades being successively warmer than all previous decades in the instrumental record.
The graphic on the following page presents plots of data sets from different locations (various colors), measured in a similar manner and normalized on the Y axis to show variations of the data with time as indicated on the x axis.
The graphs on the left side of the figure show data from locations for which similar data exists going back in time earlier than 1900. From top to bottom, these graphs show the following:
“AR6 (2023) documents that, since AR5 (2013), changes to the state of the physical and biogeochemical climate have continued.” For additional information on the data utilized above, see IPCC AR5 Supplementary Material 2.5M.5.
Land surface air temperature has increased since the late 1800s;
Sea surface temperature has increased steadily since the 1920s;
Marine air temperature has increased steadily since the 1920s;
Sea level rise has continued to steadily increase since data sets were first available in the late 1800s;
Summer arctic sea-ice extent has steadily decreased since about the 1960s.
The graphs on the right side of the figure are plots of data sets for which measurements are only available over the past 60-80 years. From top to bottom, these graphs show the following:
Tropospheric temperature (4-12 miles above the earth’s surface) has increased steadily since about the 1970s;
Ocean heat content estimates have increased steadily since about the 1970s.
Northern hemisphere snow cover has been steadily decreasing, and;
Glacial mass balance has steadily declined since the 1940s.
The variation over time from these data sets from different locations throughout the world is remarkably similar. In the past, in engineering, climate has been assumed to be an unchanging constant, or “stationary. The figure above from IPCC demonstrates that observed “non-stationary” changes in multiple earth systems are both significant for civil engineering design and operations and are as expected for a warming world. Going forward, as part of an effort to reduce losses due to weather- and climate-related conditions, engineering design will need to account for changes in multiple natural systems, especially in the statistics of weather and climate events.
Technical Bulletins on Climate Change in Civil and Environmental Engineering are prepared by the American Society of Civil Engineers Committee on Adaptation to Climate Change, Dan Walker, Ph.D., and Craig Musselman, P.E., editors. NOTE: These Engineering Bulletins are intended to alert the reader to emerging topics related to climate change and civil engineering practice and are NOT intended to act as a substitute for any sources cited herein.