In This Issue
Spring Bridge Issue on Engineering and Climate Change
March 15, 2020 Volume 50 Issue 1
The seven articles in this issue cannot cover all engineering-related aspects of climate change, but they highlight several areas of concern.

Engineering in the Detection of Climate Change

Monday, March 16, 2020

Author: Claire L. Parkinson

Climate change has occurred throughout the estimated 4.5 billion years of Earth’s existence and has been an important factor in the evolution of life on this planet, from its beginning to the extinction of species all along the path of the evolutionary time line. It has affected human societies in major ways, with substantial evidence that it may even have been a major factor in the downfall of entire civilizations (e.g., Diamond 2005; Linden 2006; Mayewski and White 2002). Individuals have probably noticed climate changes since early in human history and responded accordingly, for instance by moving inland as sea level rises. This article presents a small sampling of what has been learned in the past few decades about climate change and the importance of engineering to these advances.

Progression of Climate Change Recognition Methods Since the 19th Century

Knowledge of substantial climate changes over time took a major step forward in the 19th century when Louis Agassiz and others accumulated evidence that large areas of northern Eurasia and North America had at times been overlain by massive ice sheets, during what are now referred to as the Ice Ages (e.g., Agassiz 1837, 1840; Imbrie and Imbrie 1979). This knowledge was obtained largely by observant individuals wandering the landscape, noticing unusual or out-of-place features, recognizing their similarities with visible changes in the regions of then-current glaciers, and putting together coherent narratives of past climate changes. Little or no engineering was involved.

What a difference exists between the lack of engineering used in the initial recognition of past ice ages and the immense amount of engineering required for much of the wealth of climate change information determined since the 19th century! Certainly some important in situ observations can still be made without engineering, such as the number of weeks a year ice occurs on individual lakes, or the dates of first occurrence of springtime blooming of specific flowers in specific locations, or the advance and retreat of mountain glaciers and ice caps. However, these are now the exceptions when considering the quantified information about climate change obtained in the past several decades, a vast amount of which would not have been possible without significant engineering efforts.

It is only relatively recently that the tools have been available to quantify changes in many key climate variables. From the now ubiquitous thermometer, easily held in a hand, to massive drilling equipment for obtaining deep sea cores, all of the tools that have allowed quantification of climate changes beyond those that are simple counts have required engineering.

Assessing Climate over the Past 2 Million Years

The understanding of past climate changes has come quite a ways since the surprising and initially controversial 19th century revelation that northern Europe at some point in the past was covered by ice. It is now recognized that over the past 2 million years the Earth experienced a sequence of ice ages, with ice covering the northern regions of Europe, Asia, and North America, and with corresponding changes in precipitation patterns and vegetation in low, middle, and high latitudes. Earlier still, there were extended periods with far more ice than during the last 2 million years and also extended periods with far less ice than exists today. The further back in time one considers, the greater the uncertainties become, but a coherent picture, approximate as it may be, has emerged of what climate and other changes have occurred through the estimated 4.5 billion years of Earth’s existence (e.g., Hazen 2012; Parkinson 2010).

Information about the past has come through many sources, including deep sea cores, ice cores, tree rings, corals, stalagmites, and lake sediments (along with a substantial amount of theory and speculation). Irrespective of the source, engineering has typically played a crucial role, as illustrated here with information obtained from ice cores.

Information from Ice Cores

Deep ice cores drilled vertically through the Antarctic and Greenland ice sheets provide a record of conditions going back tens of thousands to hundreds of thousands of years, in some cases covering the last eight glacial-interglacial cycles. These cores have revealed details of past climate changes such as the following: Southern Hemisphere atmospheric circulation was likely significantly different during the last interglacial, about 130,000 years ago, than today, based on the composition of dust particles in an Antarctic ice core (Aarons et al. 2019); interannual to decadal climate variability in the Antarctic region at the time of the last glacial maximum was almost double the variability in the past 11,700 years (Jones et al. 2018); average global ocean temperature increased about 2.57°C in the first 10,000 years after the peak of the last ice age about 20,000 years ago (Bereiter et al. 2018).

Of relevance to current concerns about increasing greenhouse gases in today’s atmosphere, deep ice core records have revealed that (i) changes in the greenhouse gas carbon dioxide (CO2) have been highly correlated with temperature changes over the past 800,000 years, as atmospheric CO2 and temperature rose and fell together through several ice age/interglacial cycles (Luthi et al. 2008; Petit et al. 1999; Siegenthaler et al. 2005); and (ii) the greenhouse gases methane and nitrous oxide are similarly strongly correlated with temperature (e.g., Schilt et al. 2010; Spahni et al. 2005). Furthermore, they have revealed that climate can change overwhelmingly faster than had been imagined prior to the collection of ice core records (e.g., Mayewski and White 2002). In the words of Penn State geoscientist Richard Alley (2000, p. 111), regarding a major climate change in Greenland near the end of the Younger Dryas cold period about 11,500 years ago: “I cannot insist that the climate changed in one year, but it certainly looks that way.”

Shallower ice cores from around the world have also revealed considerable climate change information. For examples: Analyses of an ice core from the Siberian Altai Mountains reveal that the modern Altai glaciers were formed during the Younger Dryas and provide a record of air temperature fluctuations in the Altai region since then (Aizen et al. 2016); ice cores from the Peruvian Andes include evidence of the Younger Dryas in the tropics and warming of perhaps 8–12°C since the last glacial stage (Thompson et al. 1995); an ice core from the Swiss-Italian Alps provides a record of mineral dust that suggests which periods in the past 800 years likely had drier winters in North Africa and increased spring/summer precipitation in west-central Europe (Thevenon et al. 2009); and ice cores from the Tibetan Plateau have revealed that this plateau has become warmer and wetter since the mid-19th century (Thompson et al. 2018).

Arriving at climate change conclusions from ice core records requires significant interpretation and analysis by scientists. This includes establishing a correct timeline through the depth of the core and making appropriate conversions from the information directly calculated from the ice, such as the ratio of oxygen isotopes, to the information desired, such as past temperatures. The latter conversions are neither trivial nor uniform across all sites, requiring considerable scientific insight and expertise (e.g., Jouzel 2013; Thompson et al. 2000).

The Role of Engineering

In addition to the considerable science involved in determining past climate conditions, there is a need for considerable engineering. None of the information revealed about past climates through ice cores comes without engineering, as engineering is essential for constructing the drill itself.

A basic ice core drill consists of a metal pipe with teeth cut into the end that leads into the ice. The pipe is spun and forced downward. For deep ice cores, the core must be brought up in numerous sections, necessitating a means of preventing the ice surrounding the hole from filling the hole before the full core has been collected. Other complications include how to handle the ice chips that form as the drilling proceeds. Solutions vary, but the case of the ice core from the Greenland Ice Sheet Project 2 (GISP2) provides an informative example (figure 1).

Figure 1 

The GISP2 ice core was drilled to bedrock in central Greenland, obtaining a core of 3.05 kilometers (1.90 miles), brought up sequentially in sections up to 5.5 meters in length using a drill approximately 18 meters long, raised and lowered on a 3.7 km Kevlar cable (Mayewski and White 2002). Coring began in 1989 and finished in mid-1993. To prevent the ice from filling the hole during this extended period of drilling, the hole was filled with liquid butyl acetate, chosen for its environmental friendliness, nontoxic nature, and sufficiently low viscosity for the drill to drop rapidly through it; the ice chips were pumped up along the outside of the drill barrel to a holding chamber (Alley 2000).

Engineering needs continue far beyond the collection of the ice core:

  • Fine-tuned engineering is needed to cut the ice into slices for analysis and to release the ancient air trapped in bubbles in the ice without contaminating it with modern air.
  • Electrodes are used to measure electric conductivity and obtain both a measure of the acidity of the ice and a record of volcanic eruptions (Alley 2000).
  • Accelerator mass spectrometers are used to determine carbon isotope ratios and in turn to help date the ice cores (Jenk et al. 2007).
  • Mass spectrometers are also used to determine isotope ratios used in the estimation of past temperature changes (Aizen et al. 2016; Sigl et al. 2009), and inductively coupled mass spectrometry is used for trace element analysis (Beaudon et al. 2017).
  • Scanning electron microscopes, transmission electron microscopes, and energy-dispersive X-ray spectrometers are all used in analysis of the ice core particulate matter (Ellis et al. 2015).

These highlight just a few of the many carefully engineered instruments used in the analysis of ice core records (e.g., Thevenon et al. 2009).

Monitoring Recent Climate

Once the measurement tools—all engineered in one way or another—are available, changes in climate variables can be monitored as they happen. Among the variables most important for climate change that are now being monitored at individual locations on a routine basis are atmospheric temperature and atmospheric CO2. Some atmospheric temperature measurements exist for the 18th century, but attempts at global temperature records from in situ measurements rarely start earlier than the second half of the 19th century. These records reveal an uneven but also unmistakable warming since that time (Hansen et al. 2010; Jones et al. 1999; Lenssen et al. 2019).

In Situ Measurements

The most famous CO2 record is the multidecadal Mauna Loa record initiated by Charles David Keeling in 1958, when he began CO2 measurements at a new US Weather Bureau meteorological observatory on the mountain of Mauna Loa in Hawaii. This record shows a prominent annual cycle, but also a consistent increase in CO2 year after year, in marked contrast to the uneven temperature record (Keeling 1998, 2008). The CO2 increase is largely attributed to human activities, particularly combustion of fossil fuels, production of cement, and deforestation.

Keeling’s initial Mauna Loa measurements were made with a commercially available continuous infrared gas analyzer composed of a thermostated cell, an optical system, and an electronic amplifier. The analyzer was augmented by a gas handling system, calibrated reference gases, and an electric power supply; further engineered improvements came later (Keeling 1998).

In situ CO2 measurements are now made at numerous locations, and in situ temperature measurements are made at vastly more locations, with buoys and automated measuring devices significantly improving the spatial coverage over what it had been prior to the second half of the 20th century, before which measurement sites were predominantly in populated land areas. Still, the spatial coverage of in situ measurements remains very incomplete and uneven.

Satellite Measurements

The relative newness of the technology tremendously limits the length of satellite records, but satellites allow data collection for the entire Earth surface and for the full depth of the atmosphere, and they make measurements as easily for remote locations as for populous ones. In the case of CO2 measurements, they show the two major features of the Mauna Loa record—the annual cycle and the rise in CO2 over time—on a near-global basis rather than just at selected locations (see animation at

Figure 2

Some satellite records are now long enough to indicate important information about climate change. For instance, they show cooling in the stratosphere (in the upper atmosphere), with prominent warm peaks following the eruptions of El Chichon in 1982 and Mount Pinatubo in 1991 (figure 2a; also, Maycock et al. 2018), and warming in the troposphere (the lower atmosphere), with prominent peaks highlighting the strong El Niños in 1998 and 2016 (figure 2b; also, Mears and Wentz 2017). They show increases in annual snowmelt duration in high northern latitudes (Kim et al. 2015), decreases in the masses of both the Greenland ice sheet (figure 2c; also, Bevis et al. 2019) and Antarctic ice sheet (figure 2d; also, Shepherd et al. 2018; Velicogna et al. 2014), and a rise in sea level (figure 2e; also, Nerem et al. 2018) due to both the input of water into the oceans through the reduction of land-based ice and thermal expansion of the warming waters. Each of these particular changes, qualitatively, is in line with expectations based on increases in greenhouse gases.

Satellites also provide a decades-long record (since the 1970s) of both Arctic sea ice, showing a prominent downward trend overriding considerable inter-annual variability (e.g., Meier et al. 2014; Parkinson and DiGirolamo 2016), and Antarctic sea ice, showing an overall upward trend through 2014 followed by a rapid decrease (Parkinson 2019). The decreasing Arctic sea ice coverage was expected, in light of Arctic warming, and fits well in a coherent pattern of changes in the Arctic, many also recorded in satellite observations (e.g., Boisvert and Stroeve 2015; Jeffries et al. 2013; Walsh 2013). The sea ice changes in the Antarctic are more puzzling, and scientists have sought explanations both for the sea ice expansion from the late 1970s through 2014 (e.g., Meehl et al. 2016; Stammerjohn et al. 2008; Turner et al. 2009) and for the rapidity of the sea ice retreat since then (e.g., Meehl et al. 2019; Schlosser et al. 2018; Stuecker et al. 2017), with neither so far having a consensus explanation.

The Role of Engineering in Satellite Measurements

Engineering is required to build the satellites and the Earth-observing instruments, to launch the satellites into space, to maneuver the satellites into and retain them in their desired orbits, to transmit the data from the satellites to the users, and to analyze the data with the help of computers. The Earth-observing instruments need to be finely tuned to make the measurements and to continue making them for years, with limited possibility for repairs or upgrades, and constructed to withstand the considerable rigors of a launch (figure 3) and the harsh environment of outer space, thermal and other-wise (e.g., Hengeveld et al. 2010; Wise 1986).

Figure 3 

By now, a large variety of satellite instruments have been engineered to obtain data about the Earth’s climate, including passive instruments measuring radiation from each of the wavelength regions of the electro-magnetic spectrum most important for Earth observations—-ultraviolet, visible, infrared, and microwave—and active instruments sending radar and laser beams downward and measuring the timing and strength of the returned signal. Passive instruments that measure visible radiation produce images showing the Earth and its features as they might be seen from above with human eyes, while instruments that measure ultraviolet, infrared, and microwave data make it possible to monitor and quantify changes in variables that cannot be seen directly with the human eye (as well as those that can), among them gaseous constituents of the atmosphere (each of which presents its own unique radiative signature) and temperatures of land, ocean, and ice surfaces. A particular strength of active instruments is the information they provide on surface topography, relevant, for instance, to the thinning and thickening of ice sheets.

Among the major climate measurements enabled by finely engineered Earth-observing satellite instruments are

  • atmospheric temperatures from infrared (e.g., Tian et al. 2019) and microwave (e.g., Maycock et al. 2018; Mears and Wentz 2017) data,
  • sea surface temperatures from infrared data and microwave data (e.g., Minnett et al. 2019),
  • surface temperatures from infrared data (e.g., Susskind et al. 2019),
  • ozone from ultraviolet and visible data (e.g., Levelt et al. 2018),
  • atmospheric carbon dioxide and methane from infrared data (e.g., Chahine et al. 2008 for CO2; Zou et al. 2019 for methane),
  • sea ice coverage from microwave data (e.g., Parkinson 2019),
  • snow cover from visible data (e.g., Kunkel et al. 2016),
  • sea level from radar altimeters (e.g., Nerem et al. 2018),
  • ice sheet topography from laser and radar altimeters (e.g., Zwally et al. 2011), and
  • ice sheet mass changes and drought from gravity measurements (e.g., Bevis et al. 2019; Velicogna et al. 2014) and altimetry (e.g., Zwally et al. 2011).


In recent decades, major advances in the recognition and understanding of climate change are due in no small part to the engineering that is vital to the collection and analysis of climate data records. This article focuses largely on ice cores and satellites, although other comparably strong examples could have been highlighted, such as deep-sea coring.

Ice core records yield climate information for specific locations going back many thousands of years, to times when the Earth’s climate was quite different from today’s, and satellite records provide information about recent changes in numerous climate variables, from all latitudes and longitudes. Both types of records provide a tremendous wealth of information about climate change, based on a combination of engineering to construct the instrumentation and science to analyze and interpret the collected data.


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About the Author:Claire Parkinson (NAE/NAS) is climate change senior scientist at NASA Goddard Space Flight Center.