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Talking points comparing Drawdown and En-ROADS

I expect to find many people in civic group workshops will be familiar with Drawdown, and will want to know how it relates to En-ROADS.  What do we think are the key talking points on that?

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Here's a few of my ideas so far.

Points of alignment

1) Generally consistent in overall data and model, as they should be - drawing from the scientific consensus. Both give a sense of how all solutions are not equal, some are relatively much higher leverage 

2) In order to get well below 2C warming, we need cumulative emissions reduction in 2050 of about 1000 GT CO2e vs Business As Usual (BAU).  

  • Drawdown’s top 80 solutions together contribute about 1000 GT in their “Plausible” scenario – with all solutions deployed at moderately aggressive pace. 
  • In En-ROADS, look at Cumulative CO2 Emissions graph (a Cumulative GHG Emissions graph would be better, but can’t find). En-ROADS BAU projection of 3900 GT CO2 in 2050, while a 1.7C En-ROADS scenario brings cumulative CO2 down to 3036 GT (an 870 GT reduction). Adding estimated additional 10-15% CO2e reduction for Methane & Other, that’s also about 1000 GT CO2e reduction.


3- Need a big basket of many solutions deploying all together. Food system and land use, buildings and transportation efficiency are key. Simply rolling FF to renewables because renewables are awesome won’t be enough




1) Main difference: En-ROADS exposes the dynamics of various policies' timing and strength, giving us easy control over variable policy levers, whereas Drawdown uses three static scenario models and generally avoids bringing the policy dimension into the open.

2) En-ROADS lets us model particular policy incentives (e.g. Keep it in the Ground, carbon pricing) are necessary, whereas Drawdown doesnt address policy as a variable.

3) Drawdown excels in unpacking different specific solutions within a category - e.g. wind power —> offshore vs onshore wind, solar —> rooftop vs utility-scale solar, silvopasture vs classic no-till/cover-cropping regenerative agriculture. En-ROADS groups solutions into broader categories, i.e. Renewables

4) En-ROADS doesn’t show much effect from population, whereas Drawdown models this as the single most powerful lever. Not clear why this is so different.

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On the population question:  I believe the decision was made to limit the population parameter range to the IPCC minimum and maximum forecasts (with the setting at the expected level).  So it is treated in En-ROADs more as a scenario lever rather than a policy lever.  This should be confirmed by Climate Interactive.  My suspicion is that Drawdown (an application I am not familiar with) allows the population to be changed much more significantly than in En-ROADs.  So it is not as useful for someone who wants to test radical population policy.

Facilitators should be cautious in making full lever pulls and comparing impact across different levers.  Judgement was used to establish the minimum and maximums, but they are not really the same effort or difficulty across all of them.

Again, I am not familiar with Drawdown, but from your response, Curt Newton, it seems like it might be a very good followup tp En-ROADS once it is used to identify a strategy.  To help identify particular tactics.  There are similar models in health (ReThink Health's Dynamic Model is at the strategy level and the CDC's PRISM Model is for particular tactics for some of the levers in the strategy model.

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I'm getting a lot of questions on this. These are really useful responses, and I'd love to see more. 

I have had trouble trying to wrap my head around Project Drawdown. I cannot find any good presentation of how they developed their categories or how they came up with their estimates.

Their #1 solution is refrigerant management. I don't see how En-ROADS can come close to replicating that result. If anyone has some insight on Project Drawdown I would be interested to hear it.

As it is, it is extremely difficult to contrast the two effort.

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In general, Drawdown assembled teams of grad student and post-doc fellows to research individual solutions, with some degree of coordination to pull everything together in an integrated model. The book has a lot more detail about their models and methods than they've posted on their website.

And re: refrigerants - It seems our capacity to collect real data about refrigerant emissions (under the Methane and Other Gases slider) is spotty - i.e. this recent paper covered in Tech Review


Thank you for the comparison.  I have read Project Drawdown and participated in a Drawdown workshop.  I found it to be effective in that it sparked actual real world concepts that support its goal of reducing GHG emissions.  The 80 solutions and the 20 hypothetical additions really planted a lot of seeds with the attendees of the workshop.  I also concur that there are a lot of interrelated concepts and both concepts/ schools of thought that support each other.  The En-ROAD simulator is an interactive program that is more conducive to workshops and broader group settings.  It also is a higher policy tool, as they suggest.  I like both very much on their specific merits. I would like to see better collaboration within each silo.  If we agree that we need all hands on deck, then we should be able to mold a unified approach that uses Drawdown and En-ROADS effectively..  Thanks, again, for the feedback

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David Mahood stated: "I also concur that there are a lot of interrelated concepts and both concepts/ schools of thought that support each other.  [...]  I would like to see better collaboration within each silo.  If we agree that we need all hands on deck, then we should be able to mold a unified approach that uses Drawdown and En-ROADS effectively." 

I couldn't agree more! 

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I've facilitated the Pachamama Alliance Introduction to Drawdown workshop a few times, and I'd love to find a way to merge that approach and work with the En-ROADS simulator. 

Note that Drawdown is NOT a simulator - it presents a (static) estimate of how much we could reduce GHGs by 2050 (in CO2Gt equivalent) if we were "fully" implementing each of the 80 researched solutions. They also provide an estimate of the cost of implementation and the savings resulting from implementation. They've made the data from their solutions research available on the Project Drawdown website

What would be incredibly helpful would be a way to see total (accumulated) GHG reduction by 2050 as a result of each lever in En-ROADS, so we could compare the results  more directly to the data available from Drawdown.  Then some of us could attempt to produce tables showing the aggregated savings reported in Drawdown to match the aggregated solutions related to each lever in En-ROADS (and look at just how far we would need to push certain policies to match Drawdown estimates).

It would also be good to be able to adjust population to more extreme policy possibilities, to show why Drawdown's combination of Family Planning + Educating Girls = biggest reduction in GHGs by 2050.


Thanks for the post.  It helps me understand PD a bit more, particularly the way you highlight PD numbers are "a (static) estimate of how much we could reduce GHGs by 2050 (in CO2Gt equivalent) if we were "fully" implementing each" option.

We don't track cumulative reductions by 2050 for each slider. Someone could move a slider and look at the cumulative results, if they want to start helping connect PD with En-ROADS. There is a problem though, because PD has 80 solutions and En-ROADS has fewer sliders.  That means that a single En-ROADS slider likely incorporates the impacts of several PD solutions.

Your comment about that PD is a  "static estimate [...] by 2050" is important when thinking about how PD and En-ROADS interact:

En-ROADS is a dynamic systems model that includes important things like delays and time to implement policy choices. For instance, building a nuclear plant could take a long time and might not have as much carbon impact as someone might assume it would.  Same with other zero-carbon technologies.  

These delays also apply, importantly, for some of the nature based solutions, like the recent Trillion Trees news.  Planting a tree today doesn't really reduce carbon today.  It reduces a little bit of carbon over decades.  In fact, some of the latest science says that mature trees, those 30+ years old, are the ones that draw down the most carbon.  This means that trees are doing lots of good work, but it could be a long time for now -- even after 2050.  

Cumulatively, the total carbon a tree might draw down could be big, but it might not have prevent warming in 2030 and 2040.  The ice caps might still have melted.  Timing of reductions does matter to the warming of the planet, not just the magnitude of the carbon reduction.

We need many different policies and approaches.  We need zero-carbon energy, nature based solutions, energy efficiency, etc.  We also need to be understand how the timing of those policies are complimentary, with some making reductions in the near-term, and other important actions playing out over the longer-term.

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This conversation is SUPER helpful. I'm meeting later today with faculty of an MIT climate change course with substantial activities built around Drawdown and En-ROADS, will be leading workshop later this spring. [Last year's version of course just published on OpenCourseWare]

This is a question I got at my first ever presentation of the En-ROADS workshop.  Here is an excerpt of how I answered it in an email:

En-ROADS and Drawdown approach climate change from different angles.  En-ROADS is looking at policy solutions - a high leverage point in a system - to enact change.  En-ROADS asks the question, "If we did this particular action all over the world, how would it impact global temperature, taking into account all the interacting system conditions?" When we say "all over the world," we mean that all 195 countries would make this level of change.  Think of policy leverage such as the Montreal Protocol which banned CFC's and was effective at closing the ozone hole.  

The model is intended to challenge assumptions about the impact of any given strategy or group of strategies, educate about how solutions interact within a system, and to stimulate people to dialogue and engage to see what options might have be most impactful and effective to reach the 2 degrees Celsius target.  It is intended to inspire a deeper commitment to action. It includes the largest drivers of climate change and is not based on a 2050 stopping point.  En-ROADS does not currently include cost estimates, but there is research being conducted to potentially add that in the future. 

The systems dynamics of the model crunch the numbers and show the results on things such as:

positive reinforcing loops wherein once a technology begins to be deployed, the price comes down and we get better at it, so more of it is installed and the price comes down further, etc.; diminishing returns on investment; lag times for new energy technologies to be approved, capitalized, built and brought online; electric cars, wind, solar, nuclear, etc. not lowering temperature unless we are also actually keeping fossil fuels in the ground, the importance of starting early on initiatives is because of the lag times of actual installed capacity and the lag times of carbon entering and then leaving the atmosphere, etc., etc.

Drawdown presents a ranked list of 80 off the shelf, ready to go climate solutions.  It is designed to give people a sense of the magnitude of GHG emissions and costs avoided by implementing an individual strategy "modeled over a 30 year period using a reasonable yet optimistic forecast for their global rate of growth."  It doesn't equate the total savings to a degree of change in global temperature anywhere that I could find, but I may have missed that. 

I have not done a detailed study to compare the assumptions in En-ROADS to those in Drawdown, nor do I know the details of how they model their system dynamics.  That would be a bit of a research project.  However, with a brief look, I saw two differences:

1) Drawdown assumes no carbon price and

2) it's not clear to me if Drawdown accounts for infrastructure construction lag time.

To learn more about Drawdown's assumptions, see the Methodology section starting on page 218 of the book, or visit  To learn more about En-ROADS, go to

The two approaches are complementary; the teams have spoken to each other and support one another's work.  While En-ROADS can help policymakers and investors decide where to put action and how quickly it needs to happen, Drawdown gives them the granularity on the individual solutions within each of the sliders, a window into on-the-ground potential, and details on some of the dynamics, downsides and other considerations.

As for the nitty gritty of whether their numbers agree, no one has taken up that analysis so far.  Suffice it to say that we want to err on the side of agreeing and "let's get after it" rather than arguing over the ranking of solutions.  So many of the assumptions will be changing over time anyway as climate change effects begin to emerge.  That is why both En-ROADS and Drawdown keep updating their models and make them available as open source so that you can actually play with the assumptions yourself.  The key here is to agree that action needs to be taken quickly and to get started. 

Everything we do, every day matters tremendously.  


Also regarding Population, I got a question about why moving the slider didn't change the temp much and this was my reply:


Moving the slider all the way to the left represents the low growth scenario of the U.N. where there is 95% confidence that it could actually be feasible.  So this is conservative, and yet the U.N. doesn't feel it is likely to be any less than this.  Even in that scenario, our population is pretty much the same until the 2050’s, and then grows a little more slowly, then peaks in 2060 then falls to about 9.6 billion instead of 11.1 billion.  Because it doesn’t affect anything until 2050 and it doesn’t keep coal, oil, gas in the ground any sooner, it has a relatively modest impact on the overall temperature.  If there had been a policy or cultural movement back in the 70’s, then we could have seen more impact, but being that it is already 2019, there is a relatively small margin how much we can affect emissions and temperature through population.

I would love to see a clear side by side of En-ROADS and Drawdown.  I imagine this question will come up over and over because people really want to know how data and solutions compare and combine to make for scientifically-grounded, effective action.

Hope this helps.

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Drawdown just released a 100-page review and update of its work. Get the PDF here

I haven't read it yet, myself.

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