This past winter was extraordinary for many parts of the United States. New England saw unprecedented amounts of snow, while the Sierra Nevada mountains in California, famed for skiing, saw barely any. Lower-than-average snowfalls in the Sierra Nevada over the past several years have created California’s serious drought situation. In Delaware, where I live, we mostly escaped large snow events but temperatures have been below normal and there have been snow flurries in much of the state at the end of March, which are both unwelcome and unusual.
Severe droughts, floods, frequent tornadoes, polar vortices, strong monsoons, and record snowfalls are all hallmarks of extreme weather. Scientists think that extreme weather is linked to climate change. There’s also strong evidence that human activities are contributing to extreme weather and probably to climate change. It is true that extreme weather events have been a fact of life on Earth for millions of years. But it is also true that extreme weather events appear to be increasing in both severity and frequency. We know this because of the range of paleoclimatology data available to us.
Paleoclimatology is a field that has ancient roots, beginning with Egyptian recorded observations of drought and flood cycles along the Nile River. The Egyptians marked these events because the Nile floods deposited fertile soil on the fields along the river where much of their food was grown. Evidence is now mounting that a severe drought may have been responsible for the collapse of the Old Kingdom, 4000 years ago. Evidence of similar conditions has been found for Mesopotamia, another ancient civilization, where cities were abandoned at approximately the same time and soil deposits indicate a drought that may have lasted 300 years. A thoughtful review of several recent books by historians on climate change, economics, politics, and human geography can be found here. The books describe the rise and fall of numerous civilizations as a result of changing climate.
How does paleoclimatology inform our current understandings of climate events? Current computer models that are used to predict weather and longer-term climate are populated with the results of paleoclimatological studies. Much of the data gathered in such studies comes from the use of climate proxies to infer what conditions were like thousands or even millions of years ago. Some of these proxies include calcareous organisms such as diatoms, foraminifera, and coral; ice cores, tree rings, and sediment cores.
Sediment cores contain pollen and other evidence of climate and weather events over time. Palynology is the study of pollen in the fossil record. Pollen can tell us what kinds of plants lived in the study area at a particular time. Because certain kinds of plants are adapted for certain kinds of climate, scientists can track climate change over long periods of time by inference using plant pollen.
Another important source of paleoclimatology data comes from polar ice cores that preserve atmospheric oxygen isotope ratios. When sea water evaporates as a result of rising air temperatures, it tends to leave a higher percentage of heavier oxygen isotopes in the ocean. When this water freezers, a record of the higher temperatures is left behind in the ice. Ice cores preserve a wealth of other information such as atmospheric dust, pollen, volcanic ash, and pollution. The current ice core record dates back 800,000 years in Antarctica. But scientists think that there might be ice as much as 1.5 million years old on that continent. Some evidence from ice cores is pointing to a global cooling trend that occurred in the late Holocene (up to about 1800 years ago), ending with the Little Ice Age. Temperatures today are still in fact below long-term global averages.
Some scientists are advocating for the designation of a new geologic era, the Anthropocene, to indicate the effect that human activities have had on Earth’s environment. A working group of stratigraphers is currently developing a scientific basis for this new geologic era. There is active debate about the necessity of a new geologic era as well as what event should be chosen as the start of the Anthropocene. Some scientists feel that the first atomic blast is an appropriate starting point, while others suggest the beginning of agriculture or the start of the Industrial Revolution.
Developing a STEM Unit
To develop a STEM unit around paleoclimatology and its possible relation to current extreme weather events, you might like to include a number of elements. Biology teachers or a local botanical garden can help you determine which terrestrial biome applies to your area and help identify which kinds of pollen might show up in the fossil record for your area. You might be able to compare your local pollen with pollen assemblages from other climate zones. Work with a geography teacher to understand what effect historical weather events such as droughts and floods have had in your area.
A physics teacher could help you understand heat transfer and its effect on ocean circulation. Ocean circulation is the engine of climate, so this concept is at the heart of our current understandings. This is part of the reason why changes in polar ice cover are so concerning for many scientists. The uncertainties around the possible outcomes of melting polar ice highlight the importance of further research and illustrate some of the ethical dilemmas wrapped up in this topic. Your chemistry teacher could contribute background on why isotope ratios can be used to infer changes in Earth’s air temperature over time.
If your district has a computer science program, those teachers can provide examples of some of the sophisticated models used to predict weather and associated climate trends. If you don’t have access to a computer science teacher, a calculus teacher should be able to describe how the models are built. If you’ve got access to a technology lab, you could work on designing and building weather instruments. If you have students who are interested in engineering careers, you could have them investigate the emerging fields of climate engineering and terraforming, which may be used on Mars to make that planet more habitable for people in the future.
There are a number of ethical issues involved in geoengineering and terraforming, and involving English teachers or social studies teachers with an interest in ethics would enrich STEM lessons on climate change. Hard choices may need to be made in the future to ensure our sustainability as a species. Addressing the ethical issues up front will help everyone involved make the best possible decisions. The effects that human activities have had or will have on global climate change are open to debate.
Produced by the National Science Teachers Association (NSTA), science writer Becky Stewart contributes monthly to the Science and STEM Classroom e-newsletter, a forum for ideas and resources that middle and high school teachers need to support science, technology, engineering, and math curricula. If you enjoy these blog posts, follow Becky Stewart on Twitter (@ramenbecky). Fans of the old version of The STEM Classroom e-newsletter can find the archives here.