Rising Global Temperatures
Global temperatures have been rising since humans began emitting greenhouse gases. Scientists measure temperatures through advanced technology and have used basic physics to determine that more greenhouse gases lead to these warmer temperatures.
Key Takeaways
1.
Global temperatures have risen since 1880
The clearest indicator of climate change is that global temperatures have risen by 1.2ºC since 1880.
2.
Greenhouse gases absorb heat
Scientists have studied for centuries the heat-absorbing properties of greenhouse gases.
3.
Satellite technology is very accurate
Satellite technology ensures that temperature readings are global, accurate, and verified.
What We Know
"Global temperatures are going up." The scientific consensus around this alarming fact is overwhelming. Global temperatures have risen about 2.1ºF (1.2ºC) since 1880 (when the Industrial Revolution kicked off and humans started releasing greenhouse gases), which can be directly attributed to human activities. This amount may not seem like much when considering daily temperatures, but consider this fact with the entire world being 2.1ºF hotter. To put this number in perspective, scientists estimate that the most recent Ice Age only had temperatures about 9ºF cooler than current (pre-industrial) average temperatures. Small temperature changes make an enormous difference.
The interactive graph below (with data from NASA) shows how temperatures have changed based on the 1950–1980 average. As you can see, there has been a shocking increase in global temperatures, particularly in the last forty years.
We also know that greenhouse gases are the cause of this warming. There is a natural greenhouse cycle to keep the earth heated and able to sustain life. However, humans are creating a variation in the natural cycle.
Temperature Anomaly Based on 1950-1980 Average
Can't interact with the graph above? Click here!
How We Know
There are two parts to this question: how scientists know the earth is warming and how they attribute it to humans. First, scientists know the earth is warming through careful measurements since 1880 at thousands of locations across the world. In modern times, readings are incredibly accurate because scientists use stations across the world and satellite technology while employing complex methods to eliminate errors (such as different instruments taking different measurements) from the results. In particular, satellite technology allows scientists to measure air temperature and surface temperature and compare results to ensure accurate readings.
Even before humans started emitting greenhouse gases, scientists discovered how they can absorb heat. Their heat-absorbing properties were first discovered in the 1820s when scientists conducted tests on these gases using just basic physics. In 1956, James Rodger Fleming's article in American Scientist reaffirmed that carbon dioxide has a "greenhouse effect" on the earth. (Click here to read more about the greenhouse effect and how scientists have determined climate change works.)
The IPCC (the leading international body on climate change) and other scientific groups use climate modeling to analyze what drives climate change. In 2013, the IPCC concluded that humans are the “dominant cause of the observed warming.” In particular, “fingerprint” models analyze each specific change within climate change (each fingerprint of climate change) to see what caused it. These models are a key part of proving that climate change is caused by humans.
Sources
Fleming, James, Gavin Schmidt, and Gilbert Plass. “Carbon Dioxide and the Climate.” American Scientist 98, no. 1 (2010): 58. https://doi.org/10.1511/2010.82.58.
Nancy Huddleston. “Climate Change: Evidence, Impacts, and Choices: Answers to Common Questions About the Science of Climate Change.” National Research Council of the National Academies, 2012. https://www.nap.edu/resource/12781/Climate-Change-Lines-of-Evidence.pdf.