Humans and life in general influence the global climate.
- A range of natural records show that the last 10,000 years have been an unusually stable period in Earth’s climate history. Modern human societies developed during this time. The agricultural, economic, and transportation systems we rely upon are vulnerable if the climate changes significantly.
- Life – including microbes, plants, and animals and humans – is a major driver of the global carbon cycle and can influence global climate by modifying the chemical makeup of the atmosphere. The geologic record shows that life has significantly altered the atmosphere during Earth’s history.
Recent climate change is occurring at an unprecedented rate.
- Natural processes driving Earth’s long-term climate variability do not explain the rapid climate change observed in recent decades. The only explanation that is consistent with all available evidence is that human impacts are playing an increasing role in climate change. Future changes in climate may be rapid compared to historical changes.
- Natural processes that remove carbon dioxide from the atmosphere operate slowly when compared to the processes that are now adding it to the atmosphere. Thus, carbon dioxide introduced into the atmosphere today may remain there for a century or more. Other greenhouse gases, including some created by humans, may remain in the atmosphere for thousands of years.
- The only way to assess whether the recently observed warming fits with a pattern of natural variability is to look at how temperature has varied in the past. This can be done using paleoclimatic evidence from tree rings, glaciers, corals, and other geologic records. It is clear from extensive research and reconstructions of temperature over the past two thousand years that the magnitude and rate of change over the past century far exceeds any natural variability that occurred in the past two millennia. (http://www.climate.org/topics/climate-change/debunking-climate-change-myths.html)
Human activities are having marked impacts on the climate system.
- The overwhelming consensus of scientific studies on climate indicates that most of the observed increase in global average temperatures since the later part of the 20th century is very likely due to human activities, primarily from increases in greenhouse gas concentrations resulting from the burning of fossil fuels.
- Emissions from the widespread burning of fossil fuels since the start of the Industrial Revolution have increased the concentration of greenhouse gasses in the atmosphere. Because these gases can remain in the atmosphere for hundreds of years before being removed by natural processes, their warming influence is projected to persist into the next century.
- Human activities have affected the land, oceans, and atmosphere, and these changes have altered global climate patterns. Burning fossil fuels, releasing chemicals into the atmosphere, reducing the amount of forest cover, and rapid expansion of farming, development, and industrial activities are releasing carbon dioxide into the atmosphere and changing the balance of the climate system.
- Global demands for energy resources are increasing. This is due to human population growth and increasing worldwide consumption. As certain energy resources are depleted and demand increases, competition for these resources also increases. This is especially true of non-renewable resources, such as fossil fuels. (KEEP Conceptual Framework)