6.1: Introduction to Climate Change
- Page ID
- 105344
Introduction to Climate Change
- Please read and watch the following Learning Resources
- Reading the material for understanding, and taking notes during videos, will take approximately 1 hour.
- Optional Activities are embedded.
- To navigate to the next section, use the Contents menu at the top of the page OR the right arrow on the side of the page.
- If on a mobile device, use the Contents menu at the top of the page OR the links at the bottom of the page.
- Define global climate change
- Summarize the effects of the Industrial Revolution on global atmospheric carbon dioxide concentration
- Describe three natural factors affecting long-term global climate
- List two or more greenhouse gases and describe their role in the greenhouse effect
Introduction
All biomes are universally affected by global conditions, such as climate, that ultimately shape each biome’s environment. Scientists who study climate have noted a series of marked changes that have become increasingly evident during the last sixty years. Climate change refers to the complete set of climate characteristics—temperature; precipitation; pressure systems; wind patterns; and oceanic currents—that are changing locally, regionally, and globally due to human influences. It is closely related to global warming, also called global heating, which describes the general trend of increasing global temperatures we see under climate change. However, climate change is more inclusive of the totality of abiotic effects of a warming planet.
Climate and Weather
A common misconception about global climate change is that a specific weather event occurring in a particular region (for example, a very cool week in June in central Saskatchewan) is evidence of global climate change. However, a cold week in June is a weather-related event and not a climate-related one. These misconceptions often arise because of confusion over the terms climate and weather.
Discover the real reason we confuse weather and climate in this 5-minute video from Hot Mess (US PBS).
Question after watching: How does our personal experience of weather have an effect on how we view climate change?
Climate refers to the long-term, predictable atmospheric conditions of a specific area. The climate of a biome is characterized by having consistent temperature and annual rainfall ranges. Climate does not address the amount of rain that fell on one particular day in a biome or the colder-than-average temperatures that occurred one season. In contrast, weather refers to the conditions of the atmosphere during a short period of time. Weather forecasts are usually made for 48-hour cycles. Long-range weather forecasts are available but can be unreliable.
To better understand the difference between climate and weather, imagine that you are planning an outdoor event in Kamloops, BC. You would be thinking about climate when you plan the event in the summer rather than the winter because you have long-term knowledge that any Saturday in May through August would be a better choice for an outdoor event in Kamloops than a Saturday in January. However, you cannot determine the specific day on which that event should be held because it is difficult to accurately predict the weather. Climate can be considered “average” weather.
Which of the following is an example of climate?
- An intense thunderstorm in Houston.
- The average temperature in Chicago over the past 50 years.
- An unusually hot fall in Boston.
- A foggy day in San Francisco.
- Answer
-
B. The average temperature in Chicago over the past 50 years.
Global Climate Change
Climate change can be understood by approaching three areas of study:
- current and past global climate change
- causes of past and present-day global climate change
- ancient and current results of climate change
It is helpful to keep these three different aspects of climate change clearly separated when consuming media reports about global climate change. It is common for reports and discussions about global climate change to confuse the data showing that Earth’s climate is changing with the factors that drive this climate change.
Evidence for Past and Current Global Climate Change
Since scientists cannot go back in time to directly measure climatic variables, such as average temperature and precipitation, they must instead indirectly measure temperature. To do this, scientists rely on historical evidence of Earth’s past climate.
Antarctic ice cores are a key example of such evidence. These ice cores are samples of polar ice obtained by means of drills that reach thousands of meters into ice sheets or high mountain glaciers. Viewing the ice cores is like traveling backwards through time; the deeper the sample, the earlier the time period. Trapped within the ice are bubbles of air and other biological evidence that can reveal temperature and carbon dioxide data. Antarctic ice cores have been collected and analyzed to indirectly estimate the temperature of the Earth over the past 400,000 years (Figure \(\PageIndex{1}\)a). The 0°C on this graph refers to the long-term, modern-day average. Temperatures that are greater than 0°C exceed Earth’s long-term average temperature. Conversely, temperatures that are less than 0°C are less than Earth’s average temperature. This figure shows that there have been periodic cycles of increasing and decreasing temperature.
Before the late 1800s, the Earth was as much as 9°C cooler and as much as 3°C warmer. Most of the past 400,000 years have been colder than today. Most of the past warming and cooling periods happened over long enough time scales that the majority of organisms were able to adapt and evolve with the changing climate.
The graph in Figure \(\PageIndex{1}\)b shows that the atmospheric concentration of carbon dioxide has also risen and fallen in periodic cycles. Note the relationship between carbon dioxide concentration and temperature. Figure \(\PageIndex{1}\)b shows that carbon dioxide levels in the atmosphere have historically cycled between 180 and 300 parts per million (ppm) by volume.
Figure \(\PageIndex{1}\) does not show the last 2,000 years with enough detail to compare the changes in Earth’s temperature during the last 400,000 years with the temperature change that has occurred in the more recent past. Three significant temperature anomalies, or irregularities, have occurred in the last 2000 years. The first two are the Medieval Climate Anomaly (or the Medieval Warm Period) and the Little Ice Age. A third temperature anomaly aligns with the Industrial Era.
The Medieval Climate Anomaly occurred between 900 and 1300 AD. During this time period, many climate scientists think that slightly warmer weather conditions prevailed in many parts of the world; the higher-than-average temperature changes varied between 0.10 °C and 0.20 °C above the norm. Although 0.10 °C does not seem large enough to produce any noticeable change, it did free seas of ice. Remember, the temperatures stated here are global averages. Some areas became much warmer, especially at higher latitudes, and some areas remained at their same averages. Because of the warming in the higher latitudes, the Vikings were able to colonize Greenland.
The Little Ice Age was a cold period that occurred between 1550 AD and 1850 AD. During this time, a slight cooling of a little less than 1°C was observed in North America, Europe, and possibly other areas of the Earth. This 1°C change in global temperature is a seemingly small deviation in temperature (as was observed during the Medieval Climate Anomaly); however, it also resulted in noticeable changes. Historical accounts reveal a time of exceptionally harsh winters with much snow and frost.
The Industrial Revolution, which began around 1750, was characterized by changes in much of human society. Advances in agriculture increased the food supply, which improved the standard of living for people in Europe and North America. New technologies were invented and provided jobs and cheaper goods. These new technologies were powered using fossil fuels, especially coal. The Industrial Revolution starting in the early nineteenth century ushered in the beginning of the Industrial Era. When a fossil fuel (coal, oil, or natural gas) is burned, carbon dioxide is released. With the beginning of the Industrial Era, atmospheric carbon dioxide began to rise (Figure \(\PageIndex{2}\)).
Causes of Past Climate Change
Since it is not possible to go back in time to directly observe and measure climate, scientists use indirect evidence to determine the drivers, or causes, that may be responsible for climate change. The indirect evidence includes data collected using ice cores, boreholes (a narrow shaft bored into the ground), tree rings, glacier lengths, pollen remains, and ocean sediments. The data shows a correlation between the timing of temperature changes and drivers of climate change: before the Industrial Era (pre-1780), there were three drivers of climate change that were not related to human activity or atmospheric gases.
The first of these is the Milankovitch cycles. The Milankovitch cycles describe the effects of slight changes in the Earth’s orbit on Earth’s climate. The length of the Milankovitch cycles ranges between 19,000 and 100,000 years. In other words, one could expect to see some predictable changes in the Earth’s climate associated with changes in the Earth’s orbit at a minimum of every 19,000 years and maximum every 100,000 years.
The variation in the sun’s intensity is the second natural factor responsible for climate change. Solar intensity is the amount of solar power or energy the sun emits in a given amount of time. There is a direct relationship between solar intensity and temperature. As solar intensity increases (or decreases), the Earth’s temperature correspondingly increases (or decreases). Changes in solar intensity have been proposed as one of several possible explanations for the Little Ice Age.
Finally, volcanic eruptions are a third natural driver of climate change. Volcanic eruptions can last a few days, but the solids and gases released during an eruption can influence the climate over a period of a few years, causing short-term climate changes. The gases and solids released by volcanic eruptions can include carbon dioxide, water vapor, sulfur dioxide, hydrogen sulfide, hydrogen, and carbon monoxide. Generally, volcanic eruptions cool the climate. This occurred in 1783 when volcanoes in Iceland erupted and caused the release of large volumes of sulfuric oxide. This led to haze-effect cooling, a global phenomenon that occurs when dust, ash, or other suspended particles block out sunlight and trigger lower global temperatures as a result; haze-effect cooling usually extends for one or more years. In Europe and North America, haze-effect cooling produced some of the lowest average winter temperatures on record in 1783 and 1784.
However, today, greenhouse gases are probably the most significant drivers of the climate. When heat energy from the sun strikes the Earth, gases known as greenhouse gases trap the heat in the atmosphere, just as the glass panes of a greenhouse keep heat from escaping. The greenhouse gases that affect Earth include carbon dioxide, methane, water vapor, nitrous oxide, and chlorofluorocarbons (CFCs). Approximately half of the radiation from the sun passes through these gases in the atmosphere and strikes the Earth. This radiation is converted into thermal radiation on the Earth’s surface, and then a portion of that energy is re-radiated back into the atmosphere. Greenhouse gases, however, reflect much of the thermal energy back to the Earth’s surface. The more greenhouse gases there are in the atmosphere, the more thermal energy is reflected back to the Earth’s surface. Greenhouse gases absorb and emit radiation and are an important factor in the greenhouse effect: the warming of Earth due to carbon dioxide and other greenhouse gases in the atmosphere.
Discover the intricacies of Earth's greenhouse effect in this 3-minute video.
Question after watching: How do the so-called greenhouse gases act to insulate the Earth? Why do more greenhouse gases lead to a warmer planet?
What is the greenhouse effect?
- Certain gases in the atmosphere trap heat and warm the Earth
- Life on Earth 'exhales' gas that warms up the atmosphere
- The tilt of the Earth changes the amount of solar energy the Earth receives
- The Sun is putting out more radiant energy over time
- Answer
-
A. Certain gases in the atmosphere trap heat and warm the Earth.
Results of Past Climate Change
Climate change is not a new phenomenon. Scientists have geological evidence of the consequences of long-ago climate change. Increased global temperatures and greenhouse gases have been associated with at least one planet-wide extinction event during the geological past. The Permian extinction event occurred about 251 million years ago toward the end of the roughly 50-million-year-long geological time span known as the Permian period. This geologic time period was one of the three warmest periods in Earth’s geologic history. Scientists estimate that more than 90 percent of all life became extinct near the end of the Permian period. Organisms that had adapted to wet and warm climatic conditions, such as annual rainfall of 300–400 cm and 20 °C–30 °C in the tropical wet forest, may not have been able to survive the Permian climate change.
During the past 2 million years, there have been at least 10 cycles of natural warming and cooling on a planetary scale. When the polar ice caps melted during warming periods, sea levels rose to well above their earlier levels, and a larger portion of Earth experienced tropical climates. During cooling periods, the polar ice caps expanded, sea levels dropped, and tropical species’ ranges contracted. Sometimes these changes occurred gradually, which enabled the affected species to adapt. But the onset of some climate change periods was abrupt, causing major ecosystem disruptions and global mass extinction events. Yet, nature recovered every time; many of the species we see today are survivors of previous climate change events. It is thus fair to ask why today’s climate change is of such concern to us.
A look at the history of climate change on Earth can give us some much-needed perspective on our current climate dilemma because, the surprising truth is, what we are experiencing now is different than anything this planet has encountered before. This 11-minute video gives an overview of Earth's prior climates.
Question after watching: In what way is the current climate change different than historical climate changes?
Climate Change’s Impact on Humans (Past and Present)
History provides us with many lessons to illustrate the impact of climate change on human societies. These lessons start with the earliest well-documented example of a societal collapse—that of the Middle East’s Natufian communities roughly 10,000 years ago—which has been attributed to climatic changes. Since then, climate change has regularly contributed to the collapse of complex human societies across the world. Notable examples of such collapses include the Akkadian Empire (the world’s first empire) of the Middle East, Egypt’s Old Kingdom (the builders of the pyramids), Central America’s Classic Mayan civilization, the first English colony in America, several Chinese dynasties, and the Late Bronze Age societies along the Mediterranean Sea. Also, in Southern Africa, the fall of the Mapungubwe Kingdom has been attributed to crop failures and declining grazing lands due to regional droughts and warming cycles.
Similar patterns hold true today, only on a global scale. Because of humans' collective lack of response in addressing the drivers of climate change, more people will suffer the consequences than will not. Prominently, many parts of the world are already seeing higher temperatures and longer droughts. These conditions are compromising our quality of life by leading to more intense wildfires, increased incidences of vector-borne disease, increased crop failures, and increased competition for water. Many coastal areas are also seeing storms increasing in intensity and frequency, exposing people living near large rivers, deltas, and estuaries to more frequent flooding and storm surges. For example, the impacts from Cyclone Idai, one of the worst storms on record to have hit Africa, led to the deaths of more than 1,000 people (Figure \(\PageIndex{3}\)). While no single flooding event can be attributed to climate change, it is undeniable that warmer oceans create conditions for hurricanes and cyclones to be stronger, bigger, and more frequent. Sea level rise is expected to leave many low-lying oceanic islands uninhabitable within a few decades. With all these impacts expected to increase the competition for space under an increasing human population, it would be wise for the world’s governments to start preparing for millions of climate refugees that need to be relocated soon.
