Posted on 29 June 2024 by 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 John Mason in collaboration with members from the Gigafact team. You can submit claims you think need checking via the tipline.

Does temperature have to rise before CO2 does?

While historically Earth's temperatures have risen or fallen after its position in space slowly changed, the dominant cause of today's rapid warming is carbon dioxide emissions from human activities.

Cyclical variations in Earth’s orbit along with its axial tilt and orientation gradually affect the amount of solar energy that reaches Earth. These “Milankovitch Cycles” occur over tens of thousands of years. During a warming phase, they trigger feedback mechanisms that add additional warming.

One example is raising the temperature of the oceans, which releases carbon dioxide from the water. Thus, while CO2 increased in response to an initial warming, it also caused additional warming.

Today’s global warming is not due to Milankovitch Cycles, which are in their slow cooling phase. This time, it’s us. When we burn fossil fuels, we emit CO2 and other greenhouse gasses, which make it more difficult for heat to escape the atmosphere.

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

Science Synchronous Change of Atmospheric CO2 and Antarctic Temperature During the Last Deglacial Warming

American Institute of Physics The Carbon Dioxide Greenhouse Effect

NASA Milankovitch (Orbital) Cycles and Their Role in Earth’s Climate

NASA Why Milankovitch (Orbital) Cycles Can’t Explain Earth’s Current Warming

NASA Vital Signs – Climate Change: Vital Signs of the Planet

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.