Fact brief – Is decreased cosmic ray activity driving global warming?

Posted on 24 August 2024 by Guest Author, John Mason

Skeptical Science is partnering with Gigafact to produce fact briefs — bite-sized fact checks of trending claims. This fact brief was written by Sue Bin Park from the Gigafact team in collaboration with John Mason. You can submit claims you think need checking via the tipline.

Is decreased cosmic ray activity driving global warming?

Over 50 years of data has produced no evidence that cosmic rays are driving global warming.

While some studies attribute some small contribution to decreased cosmic ray activity, there is a scientific consensus that CO₂ is the primary factor driving temperature increases worldwide.

Galactic cosmic rays are high-energy particles released by stars of the Milky Way and other galaxies. These rays hit Earth’s upper atmosphere and produce charged particles called ions.

It is suggested these ions cause an increase in cloud cover, which would shield Earth from radiation and prevent warming; thus, it has been proposed that decreased cosmic ray activity is causing rising temperatures. However, causal links between cosmic rays, clouds, and warming have been debunked by decades of data.

A 2017 paper published in the Journal of Geophysical Research found the effects of cosmic rays on clouds insignificant compared to that of natural emissions like wildfires and volcanoes.

Go to full rebuttal on Skeptical Science or to the fact brief on Gigafact

This fact brief is responsive to conversations such as this one.

Sources

Encyclopedia Britannica Cosmic ray

Scientific American Cosmic Rays Not Causing Climate Change

JGR Atmospheres Causes and importance of new particle formation in the present-day and preindustrial atmospheres

JGR Space Physics Can solar variability explain global warming since 1970?

Environmental Research Letters Testing the proposed causal link between cosmic rays and cloud cover

About fact briefs published on Gigafact

Fact briefs are short, credibly sourced summaries that offer “yes/no” answers in response to claims found online. They rely on publicly available, often primary source data and documents. Fact briefs are created by contributors to Gigafact — a nonprofit project looking to expand participation in fact-checking and protect the democratic process. See all of our published fact briefs here.