In a recent video titled “I wasn’t worried about climate change. Now I am.” by Sabine Hossenfelder, the physicist delved into a concerning aspect of climate science that has flown under the radar for many. Despite the removal of the dislike counter on YouTube, Hossenfelder pointed out that climate change-related videos consistently received a high number of dislikes, indicating a significant resistance or reluctance from some viewers to engage with this critical global issue. Here’s what she said.

The Concern With Climate Sensitivity

The video began with Hossenfelder acknowledging the weariness that many feel when confronted with discussions about climate change, attributing it to the repetitive nature of the discourse. However, she shared the urgency of the matter, saying that the lives of hundreds of millions of people are at stake. The reason for her concern revolved around a specific parameter in climate science known as climate sensitivity.

Climate sensitivity is a crucial metric in climate models, representing the temperature change expected when atmospheric carbon dioxide levels double over pre-industrial levels. Hossenfelder highlighted a shift in the scientific community’s understanding of climate sensitivity, a change that could have profound implications for our future.

The Increase in Estimates

Until 2019, climate sensitivity estimated from sophisticated climate models ranged between 2 and 4.5 degrees Celsius. These models, part of the Coupled Model Intercomparison Project (CMIP), formed the basis for climate predictions and policy decisions. However, in the 2019 model assessment, 10 out of 55 models exceeded a climate sensitivity of 5 degrees Celsius, a range well beyond what was previously considered likely.

Hossenfelder shared that this revelation posed a significant challenge, as it suggested that the situation on our planet could deteriorate much faster than anticipated. She added that the potential consequences of high climate sensitivity, such as rapid temperature increases, could lead to severe impacts on global ecosystems, agriculture, and human habitability.

Concerns on the Modeling of Cloud Physics

The scientific community initially dismissed the models with higher climate sensitivity as outliers, sharing the importance of historical data to validate climate models. However, Hossenfelder raised a critical point about the reliability of this approach, particularly concerning the modeling of cloud physics. She shared that clouds, a dynamic component of the Earth’s climate system, play a crucial role in determining the planet’s temperature.

Hossenfelder added that the debate surrounding climate sensitivity took an intriguing turn when a UK Met Office model, considered a “hot” model with higher climate sensitivity, outperformed an older “colder” model in short-term weather forecasts. This challenged the assumption that models with higher sensitivity are unrealistic, as they seem to provide more accurate short-term predictions.

A Complex Debate

To further complicate matters, a 2020 study led by Jim Hansen suggested that the historical paleoclimate data is consistent with a climate sensitivity of 4.8 degrees Celsius, aligning with the “hot” models. This contradicts the notion that historical data supports lower sensitivity and adds weight to the concerns raised by models with higher sensitivity.

Hossenfelder accepted that the debate is complex, with scientists expressing divergent views on the validity of the recent findings. However, she shared that the potential for high climate sensitivity, if proven true, could drastically alter the timeline for taking effective action to mitigate climate change.

A Bleak Picture of the Future

The physicist painted a bleak picture of the future if the climate sensitivity is indeed higher than current policies assume.

Widespread crop failure, increased global migration, political tensions, and public health disasters are among the anticipated consequences. She added that developed countries may struggle to adapt, leading to economic downturns and a scarcity of everyday products.

Things to Do

Hossenfelder concluded with a call to action, and said, “So, here’s my wish list. Put a price on carbon dioxide emissions now. Continue to expand renewables. Build nuclear, build nuclear, build nuclear. Stop criticizing carbon removal, there’s no way around it. And for heaven’s sake, stop gluing yourself to things.

So what do you think? In light of the potential complications of higher climate sensitivity, do you believe that society is prepared to address the challenges posed by climate change? And what role should collective action play in mitigating these risks?