Limits and Timelines

To-Do Date: May 10 at 9:30am

 

1.5 o C?  2 o C?   More? 

You hear discussion of different temperature limits that we should keep within, or warnings about how much warming could occur if emissions continue to rise unabated.  Watch the 6 minute video below from atmospheric scientist Katharine Hayhoe on why these numbers are important.

The 2 C (3.6 F) limit was agreed upon by scientists and world leaders in Copenhagen in 2005 as the upper limit that avoids the worst impacts.  However, since then, impacts experienced with the 1 C increase we've experienced have been worse than those predicted in models.  1 C might not seem like much, but this is half as much as the difference between the maximum extant and end of the last ice age.  For this reason, a new target was agreed upon by the 196 nations participating in the 2015 Paris Climate Agreement.

This will still cause an enormous amount of suffering and hardship world wide, but letting the planet warm more than that will be devastating. 

https://twitter.com/unfccc/status/1413147508566495236

UN Climate Change on Twitter: "The difference between 1.5°C, 2°C or 3-4°C average global warming can sound marginal. In fact, they represent vastly different scenarios for the future of humanity. (Thread 1/5) #

UN Climate Change on Twitter: "The difference between 1.5°C, 2°C or 3-4°C average global warming can sound marginal. In fact, they represent vastly different scenarios for the future of humanity. (Thread 1/5) #

UN Climate Change on Twitter: "The difference between 1.5°C, 2°C or 3-4°C average global warming can sound marginal. In fact, they represent vastly different scenarios for the future of humanity. (Thread 1/5) #

 

Accessible text effects of different temperatures 1.5 to 2 degrees.docx Download Accessible text effects of different temperatures 1.5 to 2 degrees.docx 

Optional Resource:  This is a super informative article with some useful animations from the NY Times on why the difference between 1.5 and 2 C is important.  It might not sound like much, but as the authors write in the article,

"Half a degree may not sound like much. But as the report details, even that much warming could expose tens of millions more people worldwide to life-threatening heat waves, water shortages and coastal flooding. Half a degree may mean the difference between a world with coral reefs and Arctic summer sea ice and a world without them."

Link to Why Half a Degree of Global Warming Is a Big Deal Links to an external site.

Limiting Warming to 1.5 C, Why is 2030 Important?

In order to limit warming to only 1.5 C, we need to lower CO2 emissions by 45%  by 2030.  And in order to do that we need to start reducing emissions NOW.   As UC Santa Barbara Politics Professor and climate expert puts it, "the best time to cut carbon emissions was decades ago, but the second-best time is today."  (Link to Leah Stokes homepage Links to an external site. and Twitter Links to an external site.)


This graphic shows the different scenarios and amount  of time left for each of them.  For example, to keep within a 50% chance of remaining below 1.5 C, we could emit carbon at the current rate for only 10 more years.  To have a 50% chance of remaining below 2 C, we could emit carbon at the current rate for 28 years.  

carbon countdown

Accessible text Carbon Countdown.docx Download Accessible text Carbon Countdown.docx 

Carbon Budget

Another way to think about this that works better for some brains is in terms of a carbon budget.   In order to limit warming, there is only so  much more carbon we can put into the atmosphere. One analogy is that if I only want to go 1.5 o in debt, I can only spend so much money.  Another analogy is that a bathtub will only hold so much water before it overflows.  How much carbon can we emit and stay within the amount the atmosphere can hold and warm only 1.5 C?  Here is the carbon  budget visualized as a clock (5/10/21 screenshot below).  On the left the clock is set to 2 degrees Celsius and on the left to 1.5 degrees Celsius.  

 

1 vs 2 degreees

Click on the link below to go to a live version.  This shows how much time we can emit at current rate and exceed the budget.  You can toggle between 2 C and 1.5 C.  Link to That’s how fast the carbon clock is ticking Links to an external site.  

 

The conclusion of the 2018 IPCC Report was that, to stay within 1.5°C, we need to reduce global emissions  45% by 2030, and reach net zero emissions by 2050. 

The short video below from the IPCC summarizes their major findings.

 

Optional Resources