2: Global Climate Change
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- Accurately describe which aspects of the environment are changing due to anthropogenic climate change.
- Describe the role of greenhouse gases in climate change.
- Describe the sources of greenhouse gases.
- Describe the causes of recent climate change, particularly the role of humans in the overall climate balance.
- Explain how we know about climates in the geologic past.
- Explain Earth’s energy budget and global temperature changes.
- Explain how positive and negative feedback mechanisms can influence climate.
This chapter describes the systems involved in regulating Earth’s temperature, its climate, geologic evidence of past climate changes, and the role humans have on today’s climate change. It is critically important to be aware of the geologic context of climate change processes if we want to understand anthropogenic (human-caused) climate change. First, this awareness increases the understanding of how and why our activities are causing present-day climate change, and second, it allows us to distinguish between natural and anthropogenic processes in the climate record in the past.
- 2.1: Global Climate Change
- Earth System Science is the study of how earth systems (geosphere, atmosphere, hydrosphere, cryosphere, and biosphere) interact and change in response to natural cycles and new human-driven forces. Changes in one earth system affect other systems. A significant part of this chapter introduces various processes from different earth systems and discusses how they influence each other and impact the global climate.
- 2.2: Earth’s Temperature
- Because the Moon doesn’t have much of an atmosphere, daytime temperatures on the moon are around 224℉ and nighttime temperatures are around -298℉. That is an astonishing 522 degrees of change between the light-side and dark-side of the Moon . This section describes how Earth’s atmosphere is involved in regulating the Earth’s temperature.
- 2.3: Evidence of Recent Climate Change
- While climate has changed many times in the past, the scientific consensus is that human activity is causing the climate to change today more rapidly. While this seems like a new idea, it has been suggested for more than 75 years. This section describes the evidence that scientists agree is most likely a result of anthropogenic climate change, or, human-caused climate change.
- 2.4: Prehistoric Climate Change
- Over Earth history, the climate has changed a lot. For example, during the Mesozoic Era, the Age of Dinosaurs, the climate was much warmer and carbon dioxide was abundant in the atmosphere. However, throughout the Cenozoic Era (65 Million years ago to today), the climate has been gradually cooling. This section summarizes some of these major past climate changes.
- 2.5: Anthropogenic Causes of Climate Change
- As shown in the previous section, prehistoric changes in climate have been very slow. Climate changes typically occur slowly over many millions of years. The climate changes observed today are rapid and largely human-caused. Evidence shows that climate is changing, but what is causing that change? Scientists have suspected since the late 1800s that human-produced (anthropogenic) changes in atmospheric greenhouse gases would likely cause climate change.
Thumbnail: A typhoon as seen from low Earth orbit. (Public domain; Image Science & Analysis Laboratory, of the NASA Johnson Space Center).