Climate Change Facts

Key Facts on Climate Change from the NPS. 1. Climate change is happening now. 2. Human activities are accelerating it. 3. It injures our national parks, people, and planet. 4. The NPS is working to address it. 5. The choices we make today help avoid more catastrophic impacts in the future.

NPS Photos / Graphic by 4C

Greenhouse gases—or gases that trap heat reflected off Earth’s surface that would otherwise be released into space—are a vital component of Earth’s atmosphere. These gases include methane (CH4), water vapor, and carbon dioxide (CO₂). Without naturally existing greenhouse gases, Earth’s average temperature would be around 0ºF! However, human actions like burning fossil fuels and cutting down forests raise the amount of carbon dioxide in the atmosphere. This excess CO₂ acts like an extra-thick blanket, trapping heat and raising temperatures across the globe.

Think of climate change like a blanket. A thinner blanket allows more heat to escape. A thicker blanker made of more CO2 traps more heat, causing warming.

NPS / Graphic by Shannon Stanforth

The term “climate change” refers to how this excess heat has disrupted Earth’s natural climate system. According to the fifth synthesis report from the Intergovernmental Panel on Climate Change, 97% of climate scientists are in agreement that currently observed changes in Earth’s climate are due to human activities that burn fossil fuels, including transportation, electricity generation, and manufacturing.

Climate Change History

This concept of human influence on the climate through CO2 emissions was proposed over 100 years ago by Swedish chemist Svante Arrhenius. Arrhenius predicted that increased atmospheric CO2 in Earth’s atmosphere could significantly change the Earth’s temperature. He also proposed that human activities could lead to an increase in atmospheric CO2 and, thus, could increase planetary temperatures.

Graphic from NOAA

In the 1960s, Charles David Keeling confirmed Arrhenius’s predictions. Working at the Mauna Loa Observatory in Hawaii, he documented two trends in atmospheric CO₂ levels. One: atmospheric CO₂ concentrations vary by season—higher in the winter months, and lower in the spring and summer when plants in the Northern Hemisphere are photosynthesizing. Two: Keeling recorded a consistent rise in atmospheric CO₂ concentrations, aligning with observed rising global temperatures.

The Mauna Loa Observatory is still taking measurements today, making it the longest continuous record of atmospheric carbon dioxide in the world.

Climate Change Impacts

Anthropogenic disruption to Earth’s natural climate has a number of dangerous effects including: warming global temperatures, increased extreme heat waves, more frequent droughts and floods, more frequent wildfires, and more. These climate change impacts can be seen all throughout our national parks.

Increased atmospheric carbon has increased temperatures. The Washington D.C. region has warmed by more than 2ºF in the last century, and all four seasons have become warmer since the 1940s. When temperatures rise, extreme heat days (days above 95°F ) become more frequent, and heat waves last longer. As a result, heat emergencies are projected to increase, as the number of days at 95°F or above will go from 18–20 days out of the current year to 40–75 days by 2080. This is a huge cause for concern for national parks and beyond, as species and people face grave health and safety risks.

The good news is that there are actions you can take to help fight against the effects of climate change. See how the National Park Service is taking actions against climate change and how visitors can help.

Graphic by Shannon Stanforth