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December 2020 C-Road Update

I have used C-Roads over the last years regularly for a University Climate Change class and always found it a very powerful tool to teach the students the urgency, scale and social injustice problematic of the UN Climate Change negotiations. Yesterday (the day the new version was released) I unfortunately noticed the December 2020 update just before class which was bad timing, since the new baseline temperature is far below the old BAU temperature, which not only messed up a exercise I had set up for my students but also made the simulation much less powerful. Basically it makes the 'game' much easier and therefore the learning effect much less. I am not sure why the baseline temperature was brought down by more than a degree. It would make sense if it would reflect the current Paris agreement pledges, but the design of C-roads does not really allow for this, since the default setting is 'all regions do business as usual'. This is then reflected in making it for the participants much easier to get to 2C or below. Bearing in mind that the old versions of C-Roads probably underestimated the temperature rise before (by not including the effects of various biogeochemical feedback processes such as the positive feedback due to the albedo effect or the release of methane from permafrost or the rapid ice sheet response), it seems to me that the December 2020 update went completely in the wrong direction. It  would be interesting to know how Climate Interactive scientifically justify this move, and I would appreciate clarification on this. I understand that they wanted to make it the same base temperature than En-Roads, but En-Roads is obviously very different and what works for En-Roads should not mess up C-Roads. I appreciate that Climate Interactive is moving away from C-Roads and is focusing on EN-Roads, however, I find this a shame since C-Roads (depending of what you want to teach) is far simpler and therefore sometimes much easier and more powerful for certain class settings and learning goals. Can someone please shed light on this move for me, since I would like to continue to use C-Roads in the future but not sure I can as it is set at the moment. 

Thank you.

Pardon the delay, Lisa.

Here's a blog post about the recent C-ROADS baseline change: It is similar to the En-ROADS blog post if you already saw that, but I'm providing it here in case others are reading along. 

You are absolutely correct that a plateauing of emissions or the modest reductions in some areas, does not result in reductions in global atmospheric greenhouse gas concentrations. In our Baseline scenario global atmospheric greenhouse gas concentrations and greenhouse gas emissions are still very much rising. Indeed, the world has more work to do, and we hope that no one concludes that we have taken sufficient action. 

When it comes to baselines we like the definition from one of the foundational papers on the SSP scenarios, Riahi et al., 2017, which explains the baseline scenario as "a description of future developments in absence of new climate policies beyond those in place today.” This isn't about factoring in a national target that a country aspires to reach, but more about looking at the historical data and following the trends we have seen over time.  

Also, years ago we aligned our baseline with RCP8.5. That scenario has fallen out of favor as an unrealistically high trajectory for future warming. Read more here: Since then we have aligned our baseline scenario with the SSP2 baseline scenarios from the integrated assessment models. SSP2 is a narrative of global socioeconomic outcomes know as "middle of the road", it is neither the worst case scenario nor the best. 

At some point we would like to add a feature where users can change to a different baseline scenario if they don't like the assumptions we have used (while you are suggesting that the baseline should be higher, there are many others who said our baseline was far too high). For now, you could adjust some of the "Assumptions & Sensitivities" (found under "Simulation" in C-ROADS) to create a starting scenario that better suits your needs. Our aim is not to convince people that our baseline is correct, after all it is not intended as our forecast of what is going to happen, but is there as a scenario that we can compare against in creating scenarios of successful climate action.

Thanks for weighing in! It's so helpful to hear perspectives of you and others that are using our tools! 


Thank you Ellie for your reply. Much appreciated. The link with the reasons why the result of our latest integration of new science and data resulted in a lower temperature outcome is very helpful. I am still not sure I agree with the new baseline temperature but I can see better now where it is coming from. I will definitely try to join the webinar on Jan 7 and will look forward to see the new facilitator material.  

Just to comment on your comment that 'the new baseline does incorporate the progress the world has already made in getting the ball rolling'. However, as far as I can tell 3.6C warming at the end of the century would be probably more in the region of 'if all countries stick to their Paris agreement pledges', which only future will tell us if that will happen. Most global climate models I know predict something above 4 degrees or more warming if we stay on the trajectory we are on (see the rise of actual greenhouse gas emissions and atmospheric concentrations up to this year. You can not say there is any relief in that to be seen yet, despite countries have started to 'get the ball rolling'). I understand that the baseline temperature in En-Roads is not based on GCMs but C-Road should be in my opinion since otherwise you say in the simulation country blocks don't need to put in any pledges to get to 3.6C while in reality, countries need to put in at least their Paris agreement to get to this lower temperature increase. This is, I think, the reason, why the 'game got much easier'. Basically this update has given the simulation participants a reduction of about 1degree Celsius in advance, without them having to put in any pledges at all, not even Paris agreement equivalents. In reality, with global greenhouse gas emissions and atmospheric concentration still rising, the game should get more and more difficult rather than easier, since the longer the concentration in the atmosphere rise the harder it will be to get to below 2 degrees warming. Just because some countries have started reducing emissions does unfortunately not mean the the global atmospheric greenhouse gas concentration have started to decrease. 

Thanks again for your reply and I am looking forward to learn more about this update in January.

Best wishes


Hi Lisa, 

Thanks for writing in and sorry to hear that the updates disrupted your plans for your class last week. We are always working to make sure C-ROADS and En-ROADS reflect the best available science. You can read about the reasons why the result of our latest integration of new science and data resulted in a lower temperature outcome: We will be posting more about how this pertains to C-ROADS and updating all the materials for the World Climate Simulation in the coming days. The two tools have the same climate model foundations although they enable different approaches to focusing on emission reductions. As a result, we keep the two tools synced up in terms of their baseline scenarios. 

It is an interesting point that you make that the World Climate Simulation is now "easier" with the new baseline. In some ways the new baseline does incorporate the progress the world has already made in getting the ball rolling on addressing climate, and at the same time there are significant challenges ahead to reducing global greenhouse gas emissions significantly enough to stay within the temperature limits of the Paris agreement. The challenges of urgency, scale, and injustice are still there. As a facilitator of the World Climate  Simulation, I'd encourage participants to make proposals that specifically grapple with the realities we see in the world (e.g. financial constraints particularly in light of the pandemic) and the widespread climate impacts we are seeing at 1.1degC temperature change.  We will be working on guidance for facilitators and will discuss some of this during the monthly World Climate Simulation webinar on Jan 7, 2021 ( 

Let us know if you have more questions about the update. 



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