False: The Medieval Warm Period was hotter than today's temperatures, and carbon dioxide is the lowest it's been in millions of years.

Context

A clip of geomythologist Randall Carlson has been shared multiple times on Twitter, Facebook, and especially TikTok, where it has gained 45 thousand likes. In the clip, Randall claims that the Medieval Warm Period was warmer than the current climate, which he says is no warmer than it's ever been. To reinforce this point, he claims that carbon dioxide in the atmosphere is the lowest that it has been in 600 million years.

In fact

These claims are mainstays of climate skepticism and misinformation. There is overwhelming scientific data and evidence to show that global temperatures are increasing. The World Meteorological Society's data shows that the temperature in the last decade has been the hottest ever recorded, and temperatures globally have increased by about 1.1 degrees Celcius. This increase is already having a significant and noticeable impact on the planet's environment through an increase in ocean temperatures and glacial melting. This change in temperature globally has happened at a significantly rapid pace over the past few decades and is higher than any global temperature change in the pre-industrial period of human civilization.

While it is true that the Earth has had increases and hotter periods in global temperature historically, such as many million years ago, humans did not exist in this period, and such temperature changes significantly shaped the planet and would have been too hot to be habitable for humans. Similarly, there have been periods throughout human civilization where temperatures increased, such as the Medieval Warm Period. However, a fact check by Science Feedback and a study published in the scientific journal Nature state that the Medieval Warm Period wasn't globally warmer than current global temperatures. While there was an increase in temperature in some regions, other regions were cooler, and the temperature increases didn't occur globally across all regions simultaneously. Scientific evidence shows that modern global temperatures are higher than the Medieval Warm Period and that this period didn't cause global temperatures. Instead, temperature changes were regional events.

Similarly, the claim that carbon dioxide is the lowest in 600 million years is false. There is overwhelming evidence that the level of carbon dioxide in the atmosphere today is higher; for example, a report by NASA states it's the highest it has been in 400,000 years. The use of fossil fuels has caused increases in greenhouse gases and carbon dioxide in the atmosphere, leading to an increase in global temperature.

The verdict

A significant amount of evidence shows the global temperature has increased and is at the highest it has ever been in human civilization. The claim that the Medieval Warm Period had higher temperatures than today is misleading due to temperatures in this period being regional, with some regions being significantly cooler than others. Increases in temperatures were not a global phenomenon as they are today. Similarly, scientific evidence shows that the amount of carbon dioxide in the atmosphere is the highest in 400,000 years. Therefore, we have marked this claim as false.