The Trillionth Tonne of Carbon and Why It Matters For Climate Change

TL;DR

The trillionth tonne matters because future warming is determined by cumulative carbon dioxide emissions, making Net Zero essential for stabilizing surface temperatures. The concept was introduced in 2009 after the need for Net Zero had become clear to the lecturer around a 2005 climate conference in Exeter. Connecting a climate-response model with a carbon-cycle model shows how concentrations and temperatures respond to changing emissions. Read on to understand why stabilization alone is insufficient.

Transcript

foreign welcome everybody to the fifth of our Frank Jackson Professor lectures on Net Zero um and I'm very excited about this one now you should be too because it's likely to go horribly wrong um this is where we couple together the model we built in lectures two and three of how the temperature of the climate system responds to changing atmospheri... Read More

Key Insights

• 🇧🇶 The amount of carbon dioxide emissions determines future warming, and achieving Net Zero emissions is necessary to stabilize temperatures.
• 🥺 Different emission scenarios and rates of emissions lead to varying peak concentrations of CO2, but they all result in the same final temperature outcome.
• 💱 Proportional emissions reductions, rather than stabilization concentrations, give us a better understanding of necessary actions to mitigate climate change.
• ⚖️ Understanding the balance between emissions, concentrations, and temperature is essential for effective climate policy and decision-making.
• 🪡 The Trillionth Ton concept highlights the urgent need to reduce carbon emissions and move towards Net Zero to avoid dangerous levels of warming.
• 🖐️ Carbon capture and storage technology plays a significant role in reducing emissions, but it is more expensive than other forms of emission reduction.
• 🤨 Achieving Net Zero also raises important moral and justice questions concerning historical emissions and the responsibility of developed countries.

Questions & Answers

Q: Why does the trillionth tonne of carbon matter for climate change?

The trillionth-tonne concept highlights the relationship between cumulative carbon emissions and future warming. It shifts attention from stabilizing atmospheric concentrations to limiting total emissions and ultimately reaching Net Zero.

Q: Why are Net Zero emissions necessary to stabilize temperatures?

At Net Zero, emissions are reduced to zero, leading to no further warming or cooling at the surface. If emissions continue, even under stabilized greenhouse-gas concentrations, temperatures continue to rise.

Q: What happens if atmospheric greenhouse-gas concentrations are stabilized?

Stabilizing concentrations still allows emissions to continue. As a result, temperatures keep rising rather than stabilizing.

Q: How does the rate of carbon emissions affect warming?

Faster emissions produce higher peak carbon dioxide concentrations and more rapid temperature increases. Slower emissions produce lower peak concentrations, but the different scenarios can still reach the same final temperature outcome.

Q: How are emissions, carbon dioxide concentrations, and temperature connected?

The lecture couples a model of how climate temperature responds to changing atmospheric carbon dioxide concentrations with a carbon-cycle model of how concentrations respond to emissions. This combined approach shows how changing emissions affects the climate system in both the past and the future.

Q: When was the trillionth-tonne concept introduced?

The result was christened the “trillionth tonne of carbon” in 2009. The lecturer traces the need for Net Zero back further, including a 2005 conference in Exeter focused on avoiding dangerous climate change.

Q: What did the distributed-computing climate-model experiment find?

Researchers distributed many versions of a climate model to home computers and varied uncertain model parameters. A handful of models projected very high responses, including 10 to 12 degrees of warming when carbon dioxide concentrations doubled, while not performing much worse than the best models when compared with observations.

Q: Did the research predict 11 degrees of warming by mid-century?

No. The claim was that warming could eventually become that high in some model versions, based only on comparisons between climate models and observations. The lecturer says a headline incorrectly presented 11 degrees as a mid-century prediction, while doubled carbon dioxide concentrations were discussed as potentially occurring around 2060 or 2070.

Summary & Key Takeaways

• The Trillionth Ton concept was introduced in 2009, highlighting the connection between cumulative carbon emissions and future warming.

• Stabilizing concentrations of greenhouse gases in the atmosphere allows emissions to continue, resulting in a continuous rise in temperatures.

• Net Zero emissions, where emissions are reduced to zero, leads to no further warming or cooling at the surface.

• Different emission scenarios and rates of emissions result in varying peak concentrations of CO2, but they all lead to the same final temperature outcome.