Conceptualizing Climate Change in the Past and Present PDF

Section I Conceptualizing Climate Change in the Past and the Present SECTION I INTRODUCTION to describe a complex process of changes in the natural change” mean? In Section I of this resource guide, we will establish some key concepts that will serve as the of this guide....

Section I Conceptualizing Climate Change in the Past and the Present SECTION I INTRODUCTION to describe a complex process of changes in the natural change” mean? In Section I of this resource guide, we will establish some key concepts that will serve as the of this guide. Hebron High School - Carrollton, TX Earth System Science (ESS). ESS is a relatively new distinctive approach views the Earth’s land, oceans, and atmosphere as a single system. Rather than Depiction of the four subsystems (clockwise from top left: biosphere, hydrosphere, atmosphere, geosphere) of Earth looks at the interactions between air, water, land, and System Science. living organisms. The concepts that we explore from Source: California State University Northridge, Earth Systems Interactions (csun.edu). ESS will provide a framework for understanding climate change as a natural phenomenon. Once that baseline understanding of climate change is era in planetary history in which humans have become established, we can add additional layers that consider the driving force in planetary change. The term the relationship between climate change and human society. The second set of key concepts describes how 1950, the world has entered a new era of climate history. climates. We will examine the sources that scholars use as clues for reconstructing climate and climate change and its history relate to the ways that scholars have traditionally told the story of global history. The important to pay attention to the methods used in a past and present. ESSENTIAL CONCEPTS FROM EARTH SYSTEM SCIENCE (ESS) of the history of climate change. What keeps the Earth’s climate in equilibrium? Why does the Earth’s climate sometimes change so dramatically that scholars designate a period of 2024–2025 Social Science Resource Guide 5  Hebron High School - Carrollton, TX Earth’s atmospheric layers. altered from external forces. Those forces are called forcings. When forcings alter the climate, it often causes reactions called positive feedbacks or negative feedbacks. These concepts will be explained in more predict or even to understand precisely. The relatively detail shortly. factors that shape climate and climate change into an The Earth’s Subsystems orderly system.1 The Earth’s subsystems interact with each other to for scholars who study climate, the basics of ESS also scales geographically. For instance, on a very large scale, an entire ocean could climate works. warm, causing changes to levels of moisture in the air over a large area. Conversely, on a small scale, a single stream might dry up, changing a local ecosystem. In conceives of the world as a single system. The system both examples, the hydrosphere is interacting with the other subsystems in various ways that impact the future subsystems. On a very basic level, there are four relationship between the subsystems in those places. subsystems. The four subsystems are the geosphere (earth and rock), hydrosphere (water and ice), Geosphere atmosphere (air), and biosphere (living organisms). The geosphere encompasses all the land, earth, and These subsystems interact to shape the weather and rock that make up the planet. Sometimes, scholars use climate. The balance of the subsystems—and the Lithosphere,” a word that incorporates the stability of the weather and climate—are sometimes Greek word for rock or stone, to describe the same 2024–2025 Social Science Resource Guide 6  thermal constitution of the Earth’s subsystems. The geological time scale—encompassing the millions public is probably most familiar with the carbon cycle and billions of years it has taken for the Earth to move in which humans participate as we breathe oxygen that and change form—notable events in climate history trees and other plants produce from their absorption of include the shifting of the Earth’s plates and the carbon dioxide. In the past couple of centuries, human release and recapture of minerals and particles from use of fossil fuels has radically accelerated the Earth’s within the Earth. The Earth’s crust, a relatively thin natural carbon cycle, rapidly increasing the amount of layer of rock at the surface of the Earth, is where most carbon in the atmosphere above natural levels.2 of the interactions between the geosphere and other subsystems occur. Living organisms, which are part Forcings itself. The geosphere also impacts weather and climate, that combine to shape the climate around the globe— as occurs in locations where mountain ranges cause involves interactions between various components of clouds to form. The eruptions of volcanoes that release the four subsystems just described. The Earth’s climate gases and particles from within the Earth also drive system is also an open system. This means that it is climate change. the Sun is the Earth’s vital source of external energy. Hydrosphere That energy and the Earth’s climate system mix to The hydrosphere is all the water on the Earth, in the shape climatic conditions. Despite the variability of ground, and in the atmosphere. It includes oceans weather from day to day, over longer periods, climate and freshwater rivers and lakes as well as clouds and is relatively stable. Climate, however, does change Hebron High School - Carrollton, TX water vapor. The hydrosphere also includes ice, which some scholars count as its own subsystem called the climate change forcings. There are three particularly cryosphere of current climate change focus on the hydrosphere, energy, volcanoes, and greenhouse gases. including the melting of the cryosphere at the planet’s North and South Poles, the warming of oceans and Solar Energy sea level rise, and increasingly severe droughts and Energy from the Sun heats up the Earth. Everyone understands this reality from their own experience of feeling the Sun’s warmth on a clear day. But what Atmosphere we cannot intuitively experience is that the amount The atmosphere consists of various gases. On this of energy transferred from the Sun to the Earth is not completely consistent over time and space. For example, They are, from lowest to highest altitude: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. One important role that the atmosphere 1700s corresponded to a period of fewer sunspots and plays in climate change involves the greenhouse gas low solar activity.3 The movement of the Earth and its in which the concentration of certain gases relation to the Sun has been a driver of climate change released from the Earth’s other subsystems traps for hundreds of thousands of years. The Milankovitch heat in the lower layers of the atmosphere. Certain cycles gases in the atmosphere cause the greenhouse gas allowing them to the reach the surface. When those of the Earth receive more, or less, solar energy. These three cycles have interacted with each other to steer the lose energy and drop to the infrared level. But at that climate of the Earth into and out of periodic ice ages.4 level, the greenhouse gases absorb them, thus trapping the heat. Volcanoes If you were outside on a hot day, you might seek Biosphere shelter from the sun by moving to a shady area. The The biosphere is all living things on, in, and around ground that has not been hit by the sun will be cooler than somewhere nearby that has been absorbing solar 2024–2025 Social Science Resource Guide 7  Hebron High School - Carrollton, TX Volcanic gases in the atmosphere. Source: United States Geological Survey,. energy throughout the day. When large volcanoes erupt, they emit a layer of dust and particles that can carbon dioxide, and methane are some of the gases cooler conditions over vast regions. When multiple large volcanoes erupt one after another, the cooling atmosphere through a variety of practices, contributing to increasing concentrations of greenhouse gases in the of the world and even bring down the average global temperature. Positive and Negative Feedbacks Greenhouse Gases Because there are so many interconnected parts to the Earth’s climate system, when forcings begin to change buildings called greenhouses that capture heat from the Sun and are commonly used for agriculture. The public probably has experienced this heating forcings are called feedbacks. Some feedbacks have dynamic more frequently in automobiles that are very already been mentioned. One is the melting of sheets hot on the inside after being parked in the sun with of ice around the North Pole. Forcings that have caused the windows up. This occurs when solar radiation enters through the glass windows and warms up the resulted in this melting ice. interior surfaces of the car, such as the dashboard. Scientists classify feedbacks as either positive or dashboard and other surfaces within the car, creating 2024–2025 Social Science Resource Guide 8  Hebron High School - Carrollton, TX Source: University of Calgary,. the surface of the ocean. This development alone of positive or negative refers to the relationship has harmful consequences within the biosphere by between the original forcing and the impact of the destroying the habitat of animals such as the polar feedback. If the original forcing and the feedback both push the climate in the same direction, either both feedback because the loss of ice actually warms up the warmer or both colder, then the feedback is positive. climate in addition to the initial warming. When ice So, melting polar ice sheets is a positive feedback because warming caused the ice to melt, and losing back away from the surface of the Earth. The ocean the ice further warms the climate. Positive feedbacks, water that is exposed after the ice melts, conversely, therefore, keep pushing climate change in the absorbs more energy from the Sun, and the warming direction it is headed, either warmer or colder. Positive of the ocean is increased. feedbacks can push climate change to what is called a tipping point, at which time the change reaches a Examples of Negative Feedbacks point of no return. Negative feedbacks, conversely, Sometimes negative feedbacks also occur. If the serve to moderate climate change.5 initial change in climate is moving toward warmer conditions, a negative feedback would be a reaction Examples of Positive Feedbacks scale negative feedback occasionally occurs during example of a positive feedback. Warmer temperatures the winter season in the Great Lakes region in in the region impact aspects of the Earth’s subsystems. temperature of the Great Lakes, increasing water in portion of the hydrosphere, by melting ice that is on the atmosphere. The increased water in the air over 2024–2025 Social Science Resource Guide 9  to reconstruct the actual history of climate. Like any other historical investigation, scholars need to have sources that provide evidence of past events. In standard historical practice, historians examine written sources that are collected and stored in an archive—a physical repository of documents. Scholars who study climate history have adopted the concept they use. Sometimes, scholars who study climate also examine written documents for clues about past climatic conditions. Scholars have called the places But climate scholars also search nature itself for clues Sections II and III of this guide will cover the history of human interactions with climate over roughly the past 10,000 years. Rather than merely recount that out what happened. Hebron High School - Carrollton, TX the lakes, in turn, becomes cloud cover that cools The Archives of Nature the surface of the Earth by blocking the sunlight. subsystems—earth, water, air, and living organisms— layer of snow on the ground that, like ice, serves to or the growth of certain plants, or certain water levels, and so forth. Traces of those impacts are sometimes The weakening of the polar vortex is another discoverable in the natural world. In fact, nature is an possible example of a negative feedback because it archive, or a repository, of clues about how climate has recently caused colder than typical conditions in past. Scientists and scholars have creatively developed temperatures in the oceans and atmosphere of the methods for observing and measuring signs of past parts of the world. warmer air moves upward, the cold air in the polar vortex moves out of its usual course and travels Something observable in nature that gives an farther south into areas of the United States that it indication of past climate conditions is called a proxy. had not previously reached. In those places, winter Proxies are natural features that show evidence of temperatures drop well below regular levels. In this case, the initial warming causes colder conditions in scholars can isolate and date these impacts, they will some areas. Since the initial warming and subsequent have an idea of what the climate was like at a certain cooling do not align, it is a negative feedback. time in the past. Three of the most revealing sources of climate history are ice, trees, and soil.7 SOURCES FOR RECONSTRUCTING Ice Cores THE HISTORY OF CLIMATE Ice core sampling is a technique of drilling long Even if a scientist or a scholar is equipped with an cylinders of ice out of deep glaciers. The ice cores are understanding of how climate operates and how climate change can occur, more information is needed snowfall from each year that became the new top layer 2024–2025 Social Science Resource Guide 10  Sedimentation and Other Sources Scholars also study other parts of the natural world for data that has been collected about past conditions. The layers of sediment or mud on the bottom of lakes and the ocean contain information about the historical composition and content of water such as the amount of pollen. Coral sampling in the ocean reveals similar data as well as past temperatures of the ocean in the location of the coral. Scientists creatively harvest data about the impact of past climate conditions on various parts of the Earth System and its subsystems. Through such discoveries, scholars rediscover the climate of the past. The Archives of Society Ice core sample. There is also evidence of past climate conditions in Source: National Science Foundation, the archives of society. The term archives of society Facility refers to sources produced by humans that contain information about the climate. There are some obvious of the glacier would trap particles from the atmosphere limitations to the information scholars can gain from from an old glacier can reveal what the atmospheric Hebron High School - Carrollton, TX conditions over the past hundreds or thousands of conditions were dating as far back as hundreds of years, not the past millions of years that some sources thousands of years.8 the most precise information from the archives of Trees society, instrumental records such as recordings of temperature, are an even newer development. The climates. One can identify the age of a tree by counting oldest instrumental records date back only to the the rings of a tree that has been cut through. Scientists thermometer’s invention around 1700. about the weather during that year of the tree’s life. The tree can reveal if the year was dry or rainy and can even instruments, they left records that describe the climate. show the weather conditions of individual seasons in a year. The practice of gathering this information from of proxies similar to those used to study the archive of trees is called dendrochronology—a combination of nature. While proxies produce less precise information words that refer to trees and time. Temperature reconstruction and tree ring sample. Source: University of Georgia, 2024–2025 Social Science Resource Guide 11  Hebron High School - Carrollton, TX users to record weather conditions. Source: Bayerische StaatsBibliothek A French thermometer from around 1780. collections. summer of 2023. But temperature records for the 9 So, produce reliable information. For instance, a narrative instrumental records can clearly show trends in the climate, but only for a little more than a century. measurement of how much rain fell, but scholars can reliably know that substantial rainfall did occur. One where and how measurements should be taken to get than the archives of nature is in dating. From tree the clearest possible picture of what the climate is records we may know that there was a good year of rain doing. For instance, scientists record the temperature for plant growth, but human records can give details down to the day or hour of when it rained. precise understanding of climate trends above the Earth.10 Even though data on things like precipitation Instrumental Records Scholars use precise and accurate information that instruments seems straightforward, careful analysis is still required to combine points of data from many trends in the climate. Today, meteorologists measure daily records of high and low temperatures from accurate understanding of climate trends over larger many places around the globe. These records are very areas and longer timespans. precise, but they only go back a relatively short period 2024–2025 Social Science Resource Guide 12  Hendrick Avercamp, Winter Landscape with Skaters, c. 1608. An eighteenth-century depiction of the Swiss town of Source: Rijksmuseum Source: Swiss National Library Other Types of Records There are a variety of other types of records that Narrative Records people have left behind that also contain clues about Even before people had the instruments to past weather and climate. Sometimes people made systematically record temperature and precipitation, they still paid attention to the weather and other one can see on a building. Works of art also show Hebron High School - Carrollton, TX depictions of weather conditions. Scholars need to be careful, however, to consider if the proxy they are conditions. These types of sources include weather diaries in which someone might have left short daily not the same as a photograph with a date. The artist entries that document if it was hot, cold, rainy, cloudy, may be depicting a real scene, or the inspiration for the sunny, and so on. Ship logbooks often include such painting may have come from elsewhere. information. Other narrative records might describe whether a glacier is growing or receding, how high Grain prices are another proxy that scholars have the water level is in a river or lake, whether a lake is used as a marker for weather conditions. There is a correlation between certain types of weather and occurrences, such as a long drought or a severe storm. fruitful harvests that would cause prices to decline. Recently, however, some scholars have argued that too Scholars treat the information contained in narrative many other factors, unrelated to weather, might also records as proxies for estimating the information drive grain prices up or down, and that prices do not the narrative records do not contain a temperature recording, if they do contain an account of a cold past climate conditions. scholars can devise systems for taking those records and comparing them with other records to gain an idea FIELDS FOR STUDYING THE of climate trends and conditions over time. To return HISTORY OF CLIMATE to the glacier example, accounts of glacier expansion are not the same as temperature readings that show that contain information about the history of climate, an average temperature decline, but the growth of the glacier works as a proxy to suggest that it is growing because temperatures are declining. trained scientists, social scientists, and historians are 2024–2025 Social Science Resource Guide 13 only have expertise in researching climate history in a sources that contain useful information and develops scholars begin to join the work, and a new scholarly of a group of scholars who share common practices for and lots of research provides many perspectives and the most accurate results. Comparing discoveries that Hebron High School - Carrollton, TX many skills, including, but not limited to: collecting samples from nature (such as ice cores or tree samples), historical climatology, paleoclimatology, climate history, and the history of climate and society (HCS) reconstruct past climate conditions, and communicating they present a reliable picture of past climate and its relationship to human life. Climate History Historical Climatology and Paleoclimatology Climate historians collect and study sources from the according to historians’ methods and conventions. The skills that climate historians bring to the study of of climate that relies primarily on the archives of climate include: the ability to read the language and nature. That is, climatologists are experts at gathering information about climate from the investigation of the the texts, analytical techniques, and the contextual natural world, including the sources described earlier, knowledge to interpret the texts accurately; and the such as layers of ice or lake sediment or tree rings. ability to formulate and communicate historical narratives based on the textual evidence. The Swiss climates of the past, particularly before the 1800s when compiled sources and developed methodological for the purpose of creating widespread and systematic demonstrated that sources in the archives of society can records of climatic conditions. be used to produce trustworthy climate reconstructions. 2024–2025 Social Science Resource Guide 14  Source: Subcommission on Quaternary Stratigraphy, than the historical climatologist for information about geographical scale could be a city, a large region, likely not have the training and expertise to accurately Hebron High School - Carrollton, TX chronological scale could be days, decades, millennia, or millions of years. because they broadly explore the same topic from it comes to scale. If a scholar only has sources from The History of Climate and Society (HCS) one town, that evidence may not support a claim about an entire region. Or if the sources are all from a few decades, that data may not support a claim about entire historian Dagomar Degroot has led the push to form centuries. Geographical scale and chronological scale are very important for the study of climate history and according to scholars within it, has stemmed from the its relationship to human life. recent expansion of studies on climate from a variety of CONCEPTUALIZING CLIMATE CHANGE TODAY between past climate conditions and human societies. consider potential biases from the present that might taint their understanding of the past. The relationship between present climate change and past climate scholars contend that existing research from the various for scholars. On the one hand, there is a lot of continuity between the past and the present in terms of how the Earth’s subsystems interact to create climate conditions. Studying past climate change can help scientists and scholars understand what causes change and how the about climate causing certain social conditions. To put it 11 Earth reacts to forcings that cause climate change. On the other hand, the primary cause of current global warming—humans releasing greenhouse gases into scale. In this context, scale refers to the scope of the atmosphere—is unprecedented in human and 2024–2025 Social Science Resource Guide 15  Hebron High School - Carrollton, TX global history. Starting about two hundred years ago and increasingly since then, people have extracted and around 2.58 million years ago. The use of the term released fossil fuels at unprecedented levels. So, there are also strong discontinuities between climate change suggests that the climate change we are experiencing distant, past. epochs of very substantial climate change in the past. What concepts should scholars use to describe the relationship between today’s climate change and primarily contributed to the current trajectory of the climate change in a broader chronological context? climate. One answer to this question has come in the form of a term used to describe climate change today: the Concerns about Using the Term 12 “Anthropocene” climate conditions into the broader context of climate history while also placing a strong emphasis on the and some scholars have reservations about doing so. In uniqueness of today’s climate. to climatic conditions of the Earth over millions of seriously. Do scientists really know enough about years through to the present. The current era, or epoch, climate change today to decide that it is on the same level as the transitions into and out of the Pleistocene years ago, at the end of the last global ice age. The 2024–2025 Social Science Resource Guide 16 debated by scientists in the geological community. In have been telling stories about global history since of experts on the Earth’s geological epochs, proposed in Europe in the 1800s. But with a few exceptions, such as the French historians E. Le Roy Ladurie as a new geological time interval. They advocated that and Fernand Braudel, modern historians did not starting in the mid twentieth century, around 1950, include climate in their narratives of global history until around the year 2000. Because climate was not included in traditional histories of the world before Sciences rejected a proposal to formally name the the past two and a half decades, many things have converged—or crashed together at once—since historians have started trying to incorporate climate environmental scientists but also by social scientists, politicians and economists as well as by the public at are still sorting out the combined story of climate history and human history. human impact on the Earth system.”13 formal geological time scale accepted by the geological 14 their conclusions and make them more precise and accurate when new information becomes available, Arguments for Using the Term historians also revise the stories they tell when new information becomes available. This process has “Anthropocene” been very evident as scholars have tried a variety of Hebron High School - Carrollton, TX Is it useful and appropriate to use the term approaches to integrating climate history and human history. The dynamic, and ongoing, process in which historians are trying to understand the role that climate not done so? It is, for several reasons. Putting the relates to the present is both fascinating and important. a very high bar to reach. The fact that geologists are Mapping Climate onto Existing Narratives One, perhaps obvious, approach to bringing together is not discredited because it has not received that existing historical narratives and new information about climate history is to simply place the two is that other scholars and the public often refer to the established narratives about most parts of the world. Often, these narratives divide history into a series of suggests that 1950 is an appropriate marker for the stages that are marked by political developments. The start of current warming trends in the climate. While history of China over the past several thousand years, scholars are debating the nuances of whether or not for instance, can be portrayed neatly as a timeline of drastic is taking place in today’s climate. The term narrative moves from the Greek Empire to the Roman happening, making it easier for scholars, journalists, One option for combining climate history with these and members of the public to have vitally important types of existing historical narratives is to look at conversations about our changing climate.15 notable junctures, such as the transition from one dynasty to another, and then see if any climatic CLIMATE CHANGE AND events—such as a period of climate change—occurred NARRATIVES OF GLOBAL HISTORY around the same period. Often, scholars who employ this technique are able to show striking correlations global history for millennia. Professional historians 2024–2025 Social Science Resource Guide 17  Hebron High School - Carrollton, TX Correlations between climatic conditions and human history. Evolution of the Earth, 8th to causation. In other words, it is hard to determine if extended period of drought. The climate events and one event in history caused a second event, or if they the social events often line up to such a degree that it just coincidentally happened. Often, there is not enough seems to be more than a mere coincidence. or with certainty. So, historians need to use careful that it is not the best practice in history or science for evidence that suggests why and how something might have caused something else. they begin to study their sources. This is because such an approach could lead to biases in the results. In the context of the history of climate and society, a major question is whether or how climate conditions for, but miss other important observations. Using cause events in human societies. Do favorable climate existing narratives to guide the study of climate history conditions cause an empire to thrive? Do unfavorable may put too many constraints on climate history and conditions cause revolts and revolutions? Older turn it into little more than the retelling of narratives that scholarship—including some of the pioneering works are still based on the old frameworks they were always based on, such as dynasties or empires. as a factor in human history—made the case that climate determined or dictated the course of human Climate Determinism and the Question of Causal Relationships a strong link between climate and the development of human culture and society. Recently, the argument have also raised challenging interpretive issues related that climate sets the course for human history has been 2024–2025 Social Science Resource Guide 18 labeled climate determinism climate and society today say that they are rejecting climate determinism, but some scholars still argue that climate played a major role in shaping human history. Scholars may be able to show a correlation between a certain climatic condition and a human event, but that society, scholars place emphasis on the careful study and analysis of causal mechanisms. This approach then became the exact thing that triggered a human response. Those gears that turn and then make the next human behavior and societies.17 Multiple Scales climate history and human history relates to the Hebron High School - Carrollton, TX matter of scale. Typically, the chronological scale robust traces of buildings, artifacts, and even written documents that allow historians to reconstruct their histories. Sometimes, scholars use archeological evidence to create historical accounts of what human Source: https://www.rachelcarson.org/ life was like as far back as around 40,000 years ago. in the much more recent past, such as the twentieth Because humans before the twentieth century did not have the capability to impact climate on the scale history amount to little more than a blink of an eye that humans do today, humans arguably lacked an when compared to the millions of years over which the awareness that their actions even had the potential to Earth’s climate has evolved to become what it is today. shape the world in such a forceful and lasting way. In what meaningful way can scholars compare these Carson (1907 Silent Spring, is often credited with helping humans develop an awareness of how much potential we now have to alter histories did not overlap. The current state of climate commercial pesticides destroyed living organisms change caused by human behavior—known as the and radically transformed ecosystems in mere years, whereas natural changes in an ecosystem could only together at the moment in time in which we currently evolve over the course of decades or generations. to tell the story of the Earth’s history and the story of Today, scholars such as Dipesh Chakrabarty argue that human history in a way that illuminates both histories. climate systems in a timespan that is exponentially Incongruent Chronological Scales shorter than natural processes.18 Today’s climate 2024–2025 Social Science Resource Guide 19 change, therefore, is an event that takes place on the variations in solar energy reaching the Earth, small scale of human history because humans are a and rising concentrations of greenhouse leading cause of the climate change. But the changes gases in the atmosphere—can tip the balance are also so substantial that they have become part of between subsystems and cause climate change. the story of the Earth’s climate that has developed over Sometimes, climate change causes reactions a much greater scale (millions of years). Thus, while in nature that drive the change even more these two chronological scales are incongruent, they (positive feedbacks), while other times nevertheless have now intersected in our lifetime. reactions in nature act against the initial drivers of climate change (negative feedbacks). The Novelty of the Anthropocene Scholars and scientists learn about climate the social science scholar and the social science student history by investigating evidence in the natural with unprecedented challenges. Old methods and old world (archives of nature) and in records left by humans (archives of society). Scholars and the public wonder if anything from paleoclimatologists study the archives of nature. Climate historians study the archives any lessons from the past that can guide us through the challenges of the multiple natural crises that humanity now faces. These are real challenges, but relationship between climate history and Hebron High School - Carrollton, TX human history. of uncovering and sharing the combined history of climate and humanity is already allowing us to see and the public have begun using to describe ourselves and our world in new ways. the idea that current climate change might mark the beginning of a new climatic and SECTION I SUMMARY geological epoch in the Earth’s history. The provides key concepts for understanding the nature of the Earth’s climate and climate by human actions. change. It is a challenge to combine climate history The Earth’s four subsystems—earth, water, air, and human history into a single story, but by and living organisms—interact on local and attempting to do so, historians help us better global levels to shape climatic conditions. understand our changing climate. Forcings—events such as volcanic eruptions, 2024–2025 Social Science Resource Guide 20