What is Climate Change?

The terms global warming and climate change are often used interchangeably, but the two phenomena are different.

Global warming is the rise in global mean temperature due to the rampant release of heat trapping gasses like carbon dioxide and methane (see figure below). The atmosphere acts like a blanket that surrounds the earth. When we burn oil, coal, or natural gas for energy, the carbon dioxide released acts like thickening the blanket that envelops our planet. This disrupts the balance of incoming and outgoing solar radiation, and creates a warming system that cannot naturally repair itself in the span of the coming centuries. Based on surface and atmospheric temperatures from thousands of locations, and from satellites worldwide, scientists have determined that the global mean temperature has risen 0.8 degrees C (1.4 degrees F) since 1880. We know the carbon dioxide released from the fossil fuels that humans are burning is responsible for this change because its unique chemical signature matches that found in the carbon dioxide entering our atmosphere right now.

Climate change is a more general term that refers to changes in many climatic factors (such as temperature and precipitation) from the global to the local scale. These changes are happening at different rates and in different ways in response to global warming. As a large scale example, the United States has overall become wetter over the 20th century, while the Sahel region of central Africa has become drier. Locally, the timing and amount of rainfall is changing, which is generally resulting in less frequent but more severe storms. This could lead to increased hillside erosion and flooding, even as overall aridity continues to intensify in some areas. Furthermore, global warming and associated climate change is decreasing the Sierra snow pack and melting it sooner, causing water shortages across the state and increasing wildfire risk. In other words, the climate is becoming more extreme in response to global warming.

Greenhouse effect graphic: comparison between normal and rampant CO2 levels. — Left - Regular levels of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are created by normal life processes, trapping some of the sun's heat and preventing the planet from freezing.

Right - The rampant emission of CO2 from burning fossil fuels traps excess heat and results in an increase in the average temperature of our planet. The solution is to reduce human activities that emit heat-trapping gases.
Will Elder, NPS

Welcome to the Anthropocene

The Anthropocene is the interval of time on Earth in which key environmental processes have become dominated by human influence. There is some debate about when the Anthropocene began. According to some geologists, it began in the mid-20th century, when ice and sediment cores first demonstrated that human activities had altered the geologic record of Earth. Yet some biologists argue that humans significantly impacted biotic life long before that. These biologists view the overhunting of large, prehistoric animals as the origins of the Anthropocene. Others have adopted a more cultural approach, and propose that the first detonation of a nuclear weapon in July, 1945 was the official beginning of the newest geologic era. What do you think? When did the Anthropocene begin? What responsibility do we have, as individuals, to address it? What about as a global community?