In a recent YouTube video, Sabine Hossenfelder delved into the web of evidence that substantiates the claim that human activities are driving climate change. Here’s what she said.
Finding an Answer
The video kicked off with Hossenfelder sharing her initial encounter with the question on Twitter, prompting her to explore the answers available through online search engines.
To her surprise, the immediate results failed to provide a good answer. She said, “The first hit I got on Google is a quote from a NASA website which said, ‘It is undeniable that human activities have produced the atmospheric gasses that have trapped more of the Sun’s energy in the Earth system.’ Alright, but that doesn’t really answer the question, does it?”
Turning to artificial intelligence, Hossenfelder sought an answer from ChatGPT, which, while wordy, did not provide a concise answer either.
The Evidence
Accepting that both Google and ChatGPT explained the observable impacts of climate change, such as rising temperatures, sea level changes, and extreme weather events, Hossenfelder shifted her focus to explain the specific evidence linking these changes to human activities.
Hossenfelder methodically broke down the evidence into five key pieces, offering viewers a guided tour through the scientific reasoning behind attributing climate change to human activities.
The Continuous Rise in Carbon Dioxide Levels
The first piece of evidence revolved around the properties of carbon dioxide molecules. Hossenfelder explained that the laboratory measurement of the type of light absorbed and emitted by carbon dioxide established its role in trapping infrared radiation, essential for keeping the planet warm.
Moving to the second piece, Hossenfelder highlighted the continuous rise in carbon dioxide levels in the Earth’s atmosphere since the inception of measurements. The upward trajectory, coupled with the knowledge of carbon dioxide’s infrared-absorbing properties, formed a plausible link between human activities and global warming.
Impact of Carbon Dioxide
The third piece of evidence focused on the impact of carbon dioxide on oceans. Hossenfelder explained that the absorption of carbon dioxide by oceans leads to a decrease in pH, making them more acidic. This observation aligned with the anticipated effects of increased carbon dioxide levels and further substantiated the human influence on climate change.
The fourth piece involves isotopic analysis, specifically examining carbon isotopes. Hossenfelder explained the differences in carbon isotopes, such as carbon 12, carbon 13, and carbon 14. By studying the ratio of these isotopes, scientists can discern the origin of additional carbon dioxide in the atmosphere. The decline in the carbon 13 to carbon 12 ratios pointed to fossil fuels as the primary source, ruling out alternative explanations.
Stratospheric Cooling
The fifth and final piece introduced the phenomenon of stratospheric cooling. Hossenfelder clarified that while carbon dioxide warms the Earth’s surface, it has a cooling effect in the stratosphere.
This cooling, observed through satellite data, aligns with predictions made decades ago and provides another layer of evidence reinforcing the connection between human-induced carbon dioxide emissions and climate change.
Counter Climate Change Skeptics
Hossenfelder concluded the video by encouraging viewers to use the information as a tool to counter climate change skeptics. She shared the importance of understanding the scientific evidence to engage in informed discussions about the critical issue of our time.
So what are your thoughts? How can the public actively contribute to addressing climate change based on this knowledge?
