Scary but fake news about the National Climate Assessment

Summary: Volume II of the Fourth National Climate Assessment (NCA) has dominated the news in the weeks since its release. One of the major findings that journalists headlined was the effect of climate change on the US economy. Ten percent is vivid number to grab the attention of Americans still skeptical after thirty years of dire warnings about climate change. Unfortunately it is a dubious story, as explained in these tweets by Roger Pielke Jr.

CNN: Ten Percent hit to GDP from Climate Damage

Here is an analysis by Roger Pielke Jr. of the new NCA volume and its press coverage, from his tweets. Posted with his permission.

“Here is the NYT front page on 24 November, with Coral Davenport’s NCA story in the top right. It set the subsequent narrative of the NCA around the 10% GDP number, perhaps the least supportable claim in the entire report. The 10% figure should not have been in the report. How did this science communication failure occur?”

NYT front page on 24 November 2018

“Davenport is an excellent journalist and did not invent the 10% GDP number. I suspect it was promoted to her by someone involved in the report, unnamed in NYT article. I see no evidence that the 10% number was part of U.S. Global Change Research Program’s (USGCRP) promotion of the report.

“Where did the number come from? See this from Chapter 29 of NCA (annotated, legend below).”

NCA - climage change effect on GDP

“{The} graph shows projections of direct damage to the current U.S. economy for six impact sectors (agriculture, crime, coasts, energy, heat mortality, and labor) as a function of global average temperature change (represented as average for 2080–2099 compared to 1980–2010). …Dot-whiskers indicate the uncertainty in direct damages in 2090 (average of 2080–2099) derived from multiple combinations of climate models and forcing scenarios (dot, median; thick line, inner 66% credible interval; thin line, inner 90%). The gray shaded area represents the 90% confidence interval in the fit (black line) to the damage estimates.”

“Where does that graphic come from? “Estimating economic damage from climate change in the United States” by Solomon Hsiang et al. in Science, 30 June 2017. Same x-axis as in the NCA, but expressed in degrees C. Click to enlarge.

Hsiang - GDP Damage from Climate change

“But oddly, elsewhere the NCA associates RCP 8.5 with only a 4° C temp change. Even the 95th percentile is less than 5.5° C (10° F). See this graph from Chapter 2 of the NCA.”

NCA chapter 2 - graph of global temperature change per RCP

“So the headline, repeated everywhere 10% GDP number is not consistent with the physical science part of the report and represents a temperature change twice that of the already implausible RCP 8.5 scenario. …Shouldn’t such an outlandish, outlier conclusion been caught in the review process? Not a good look that sole review editor for this chapter is an alum of the Center for American Progress …. Even rudimentary attention to COI {conflict of interest?} would avoided this.”

“Bottom line: If experts are going to demand that they be trusted, their numbers should add up right. They don’t here. One way to ensure robust assessments is to invite in critical voices, rather than exclude them. This error was easily preventable.

“Climate change is real, and aggressive mitigation and adaptation make very good sense. Trump is still wrong. Which makes an error of this magnitude so much the worse.”


“Such a major assessment needs to be water tight, not a vehicle for stealth advocacy. If I were a contributor to this report I’d be POed at how it has been spun.”

Also, “RCP 8.5 is problematic not because some use it as a ‘worst case’ scenario (reasonable people can disagree on that), but when it is used as a ‘business as usual’ (BAU) scenario, to predict future impacts and ground Community Based Adaptation (CBA). That is a misuse of the scenario. RCP 8.5 as a BAU is implausible, as per the IPCC.

“In the NCA, RCP 8.5 is presented both as an extreme scenario and as the business as usual scenario. This is sloppy, but also a “thumb on the scale” for expressing Integrated Assessment Model (IAM) results for future impacts and benefits of mitigation. That is a shame because justifications for climate policy do not need exaggeration.

“If justifications for climate policy depend upon any scenarios of economic impact to 2100, we are doing it wrong. Effective climate policy must be built upon policies that can be justified on political time scales, that add up to long-term progress.”

See his tweets at @RogerPielkeJr !


Editor’s afterward

(1)  The headline 10% hit to GDP relies on assumption of an 8°C increase from current temperatures. Pielke gives a mild rebuttal to this massive failure in the NCA’s review process. Worse, the NCA authors and mainstream climate scientists remained silent as journalists ran with this number, far beyond anything likely to happen. To mention just one factor, the tech advances required to mine so much fossil fuel (mostly coal) contradicts RCP8.5’s assumption of tech stagnation.

(2)  There is another oddity in the NCA. It says “RCP8.5 is generally associated with higher population growth, less technological innovation, and higher carbon intensity of the global energy mix. ….Current trends in annual greenhouse gas emissions, globally, are consistent with RCP8.5.” But the RCP Database shows that current emissions are also consistent with RCP 2.6, which is the best-case scenario used in the IPCC’s Fifth Assessment Report. The emissions trend (through 2016) lies between lines of the two scenarios.

(3)  In one of the well-managed physical sciences, Pielke’s note would result in a promptly issued correction. Ditto with some of the comments submitted about the NCA. See them with the official replies. Some are amazing. My favorite is 142019 (top of page 4) by Ross McKitrick (professor of economics at the University of Guelph; see Wikipedia). He catches a sophomore-level error. The reply appears to have been written by a bot.

For more about this subject

Climate Change Policy: What Do the Models Tell Us?” by Robert S. Pindyck in Journal of Economic Literature, September 2013.

Also see Roger Pielke Jr.’s “Opening Up the Climate Policy Envelope” in Issues, Summer 2018.

“Using RCP 8.5 to project future climate impacts can help us understand a potential worst-case scenario, but using it as a generic business-as-usual scenario thus contributes to the toxic politics of climate policy.”

Roger Pielke Jr
Roger Pielke Jr.

About the author

Roger Pielke, Jr. is a Professor of Environmental Studies at the U of CO-Boulder. He was Director of the Center for Science and Technology Policy Research. He is now Director of the Sports Governance Center in the Dept of Athletics. Before joining the faculty of the U of CO, from 1993-2001 he was a Scientist at the National Center for Atmospheric Research.

His research focuses on science, innovation and politics. He holds degrees in mathematics, public policy and political science from the University of Colorado. In 2006 he received the Eduard Brückner Prize in Munich for outstanding achievement in interdisciplinary climate research. In 2012 Roger was awarded an honorary doctorate from Linköping University in Sweden and the Public Service Award of the Geological Society of America.

His page at the Center for Science and Technology Policy Research has his bio, CV, and links to some of his publications. His website has links to his works, and essays about the many subjects on which he works.

He is also author, co-author or co-editor of seven books, including The Honest Broker: Making Sense of Science in Policy and Politics (2007), The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming (2010), The Edge: The War against Cheating and Corruption in the Cutthroat World of Elite Sports (2016), and his latest work (a revision of his 2014 book) – The Rightful Place of Science: Disasters & Climate Change (see below).

Some of his recent publications.

For More Information

Ideas! For shopping ideas, see my recommended books and films at Amazon.

If you liked this post, like us on Facebook and follow us on Twitter. For more information see The keys to understanding climate change, all posts about Roger Pielke Jr., and especially these …

  1. About RCP8.5: Is our certain fate a coal-burning climate apocalypse? No!
  2. Manufacturing climate nightmares: misusing science to create horrific predictions.
  3. Good news from America about climate change, leading the way to success.
  4. Stratfor gives us good news, showing when renewables will replace fossil fuels.
  5. Focusing on worst case climate futures doesn’t work. It shouldn’t work.
  6. Updating the RCPs: The IPCC gives us good news about climate change, but we don’t listen.
  7. Roger Pielke Jr.: the politics of unlikely climate scenarios.

A new book about the science of natural disasters</h4>

Disasters and Climate Change
Available at Amazon.

See Pielke’s new book, the revised second edition of The Rightful Place of Science: Disasters & Climate Change. See my review of the first edition. Here is the publisher’s summary …

“After nearly every hurricane, heatwave, drought, or other extreme weather event, commentators rush to link the disaster with climate change. But what does the science say?

“In this fully revised and updated edition of Disasters & Climate Change, renowned political scientist Roger Pielke Jr. takes a close look at the work of the Intergovernmental Panel on Climate Change, the underlying scientific research, and the climate data to give you the latest science on how climate change is related to extreme weather. What he finds may surprise you and raise questions about the role of science in political debates.”

20 thoughts on “Scary but fake news about the National Climate Assessment

  1. I am glad to see Dr Pielke is back blogging on climate issues. His is one of the few voices of reason inbetween the polarising extremes that the issue has now become.
    As you regularly remind readers, this is just another example of factoids and scare tactics that has turned counterproductive for the proponents. It isn’t science, it is advocacy and as such, will just discredit the authors.
    Like Roger easily does, it has become almost a trivial exercise to show that the predictions do not match the science. What is the purpose? I can’t believe it will convert any waverers. Is it just to try to shore up their diminishing support?

    1. Chris,

      “What is the purpose?”

      That’s the big question, imo. As they say in AA: “Insanity is repeating the same mistakes and expecting different results.” Thirty years of this has accomplished little. Why do they continue to misrepresent and exaggerate? Why not try science?

    2. There is an unfortunate, and in my opinion half-mad, idea among progressive and left-leaning types that if they just get the same argument they made before EXACTLY RIGHT, if they just have a slightly higher stack of proof, if they just make things that little bit more accurate, they will convince people of their perspective.

      And I cannot say that that is never a factor. But a stack of facts is not an argument.

  2. It was a good soundbite, a good headline and click bait. Facts should never spoil a good story and if it is a club to beat Trump and the dumb deplorable with so much the better.

  3. What random, normal, every-day person gives a crap about GDP? How many people do they really think, honestly, make any day-to-day decisions on the basis of helping or hurting GDP?

    1. Javier,

      GDP is, as you note, of zero interest to regular people. Per capita GDP is a good indicator — not a total measure (there is no such thing) — of people’s economic well-fare. There is no one God number, just specific numbers telling us specific things. Pieces to a puzzle which we have to assemble.

      But without such data we are blind.

  4. It is interesting to me that the same politicos that are obsessed with Global Warming and Climate change, advocate unlimited open borders with massive immigration into the United States ( Such a group as the Sierra Club). This is truly an “oxymoron” as the influx of massive immigration severely damages our natural environment and would seriously increase carbon use in the US. Let me know what you make of this.

    1. I’ve also wondered about that.

      It’s much like Republicans preaching about the evils of deficits, then cutting taxes and sending the deficit skyrocketing – as Reagan, Bush Jr, and now Trump have done.

      Perhaps the reasons they give are just excuses for what they really want to do. Fortunately for our rulers, we are gullible and don’t learn from experience.

    2. As typical of incomplete human knowledge of our effect on complex relationships, consider that it could be argued that as the undeveloped world increases per capita energy use and the West is forced to go green per the most aggressive IPCC projections, this would actually decrease total world carbon emissions, since most projections assume that the carbon increases will be from the undeveloped nations who comprise most of the world’s population.

      I don’t agree with that this is a real possibility, but that a reasonable argument could be made with the loopholes In the Paris Agreement. Essentially, it means a world where the undeveloped use the fossil fuel, and the developed nations go green. It is again back to the point of when and where does the crossover from adaptation versus mitigation occur, and what is the total energy change and where it occurs.

    3. John,

      “undeveloped world increases per capita energy use and the West is forced to go green”

      This is already happening on a non-global scale. The US and some other developed nations are reducing CO2 emissions while less developed nations (like China) increase theirs.

      Like you, I’m skeptical that the former could become a larger factor than the former – until new tech arrives (eg, fusion) or existing tech matures (eg, electric cars). But go out several decades and the unexpected rules!

  5. Larry
    I remain unconvinced that electric cars will reduce the world’s carbon footprint unless the energy for them is supplied by nukes. They offer a lot of promise for niche situations (like urban taxis), but not for population at large. If it wasn’t for the scare tactic of catastrophic global warming, there would be little support.
    There are a lot of environmental issues involved supplying the materials needed for the vehicles manufacture. Because the rare earth metal refining pollution and cobalt mining doesn’t occur in the West, the sanctimonious EC proponents pretend it doesn’t exist. The energy needs for manufacture are large. The life cycle of batteries is short and recycling options aren’t that good. The renewables are unreliable so cannot be used to run the charging network. Most of the electricity to charge them will need to come from fossil fueled stations.
    I believe about half of transport fuel goes on the heavy truck fleet. Despite some staged promos, there is no viable alternative to those trucks. Recharging a 1MWh battery with an extension cord isn’t realistic!
    I may be proved wrong but probably not in my lifetime..

    1. Chris,

      “I remain unconvinced that electric cars will reduce the world’s carbon footprint unless the energy for them is supplied by nukes.”

      There is a massive body of research about this. Individual vehicles are much less efficient than central power plants (even after transmission losses). Cleaner and cheaper, also. But little will happen until the capital costs for electric vehicles come down. That’s already happening. Only the speed of the change is unknown.

      “I believe about half of transport fuel goes on the heavy truck fleet.”

      Not even close. Heavy trucks use almost exclusively diesel. Distillates (mostly diesel) for all uses, from cars to heavy trucks, is 22% (energy content) of US transportation energy – as of 2017 per EIA.

  6. Larry
    The US has quite a different fuel split to what Europe or NZ (where I live) have. Here, diesel rules and half the total fuel used is in heavy trucks.I don’t have data available on what the urban/ open road split for driving or fuel consumption is for various countries.

    My work (I am a power station engineer) has a number of electric cars from different manufacturers that we drive near daily. There are significant subsidies here for electric vehicle use. On the open road, their range is very limited, especially when loaded up. We still need to use diesel utes to move weighty components around. The recharging times are also very inconvenient, even with 35kW recharging cables. The pool cars have to spend significant periods in the carpark. We needed to get extra vehicles to cover that dead time.

    The problem that hasn’t been looked at by EV proponents is the uprating of the electricity distribution networks needed to cope with the heavier energy drain. Steady heavy loads for charging on every house will need massive infrastructure changes. That charging will change the load profile and subsequent generation significantly, especially as most will want to recharge after dark. The US may be different to Australasia, but here it will be a big problem. In much of Europe and Australasia, there is no garage or even off-street parking for private vehicles. Recharging those means lots of extension cords out on the streets.
    But that is getting way off-topic so I won’t add more to this sub-thread

    1. Chris,

      The default here is speaking about the US (“a discussion about geopolitics from an American perspective”). A parochial attitude, to be sure.

      But even globally, heavy trucks are not even close to half of transport energy consumption. They’re roughly one-fifth. Per EIA International Energy Outlook 2016, page 129:

      • Passenger transport was 61% of global transportation energy consumption (2012): 44% light vehicle, 11% aircraft, 6% other vehicles and rail.
      • Freight transport was 39% of global energy consumption: 23% trucks, 12% ships, 9% other (ships, pipelines, etc).

      Also, look at transport energy consumption by type (also per EIA 2017 Global Transportation Energy Consumption, p7): diesel and gasoline are each about 40% of global transportation energy consumption (i.e., 40 quadrillion Btu of 100 QBtu global consumption, as of 2015).

    1. Ron,

      Not a surprise. It’s politically dead in the US on a national level. Probably a lot of european politicians are reconsidering it, after the events in France. China never cared about it.

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