Climate Change

Worst-Case Climate Change Scenarios Are Highly Implausible, Argues New Study

Global temperature to rise to around 2.2°C above the pre-industrial average by 2100.

|

Back in the bad old days of the 2010s, folks like David Wallace-Wells, author of The Uninhabitable Earth: Life After Warming (2019) warned, "The UN says we're on track to get to about 4 degrees or 4.3 degrees of warming by the end of the century if we continue as we are." Or you may remember author Gaia Vince asserting in 2019 in The Guardian that "experts agree that global heating of 4C by 2100 is a real possibility."

Before rushing to kit out your climate prepper bunker, you might want to take a look at the new study by University of Colorado climate change policy researcher Roger Pielke that confirms what the Intergovernmental Panel on Climate Change found in August 2021, namely that the worst-case climate scenario is increasingly unlikely, and that while our future will be warmer, it will not be catastrophically so.

These dire predictions were based on calculations derived from a scenario of the future in which fossil fuel and agricultural emissions over the course of this century would boost atmospheric carbon dioxide to nearly 1,400 parts per million (ppm) by 2100. The current level of atmospheric carbon dioxide is just under 420 ppm, and that is up from the pre-industrial level of about 280 ppm. Largely as a result of this increase in atmospheric concentrations of greenhouse gases, global average temperature has risen to around 1.1°C above the pre-industrial level.

Climate researchers labeled this worst-case scenario "RCP8.5," and it has been somewhat updated in the new Intergovernmental Panel of Climate Change's Sixth Assessment Report (IPCC AR6) on the physical science basis of climate change and given a new moniker of SSP5-8.5.

The IPCC's AR6 report, released in August 2021, now acknowledges that "the likelihood of high emission scenarios such as RCP8.5 or SSP5-8.5 is considered low in light of recent developments in the energy sector."

The recent developments in the energy sector to which the AR6 report refers are that fossil fuel usage is likely to be fairly flat for the next 50 years. One of the main ways that the RCP8.5 scenario goes off the rails of plausibility is that it projects a six-fold rise in global coal consumption per capita by 2100. Since future coal consumption is likely to remain flat or decline, that means that global carbon dioxide emissions will be "approximately in line with the medium RCP4.5, RCP6.0 and SSP2-4.5 scenarios."

For some years now, University of Colorado climate change policy researcher Roger Pielke, Jr., and his colleagues have been pointing out that the development of the global economy is highly unlikely to trace the high emissions pathways that led to the worst projected outcomes. Nevertheless, climate studies based on the RCP8.5 scenario are the ones being relied upon by people making their predictions of dire climate calamity by the end of this century.

Pielke and his colleagues have published a new study in the journal Environmental Research Letters that argues that these intermediate emissions scenarios are much more plausible than the high end scenarios that engendered fears of climate catastrophe. "These scenarios project between 2 and 3 degrees C of warming by 2100, with a median of 2.2 degrees C," they conclude. They do, however, acknowledge that "these scenarios also indicate that the world is still off track from limiting 21st-century warming to 1.5 or below 2 degrees C."

These new calculations are based on the future energy use and energy policy projections found in the International Energy Agency's latest World Energy Outlook report. That report concludes that, instead of rising six-fold, global coal consumption will peak during this decade. On the other hand, the U.S. Energy Information Administration projects that world coal consumption will continue to rise slightly through 2050, but that's still far from the sixfold increase entailed in the RCP8.5 scenario.

To assess plausibility of most of the IPCC scenarios, Pielke and his colleagues ask which of the scenarios have projected carbon dioxide emissions growth errors and divergences of less than 0.1 or 0.3 percent per year over the observed growth rates between 2005 and 2020. That is, which scenarios tracked what actually happened with carbon dioxide emissions over the last fifteen years? Next they further parse how well the scenarios similarly track actual emissions beginning in 2005 through the IEA's projections of future emissions to 2050.

The chart above displays the plausibility of the various IPCC emissions scenarios by tracking how well they match likely cumulative emissions of carbon dioxide over the course of this century. The scenarios that closely track actual and projected IEA emissions are marked with blue dots (0.1 percent) and triangles (0.3 percent). "All of the plausible scenarios," explains Pielke in his Substack newsletter The Honest Broker, "envision less than 3 degrees Celsius total warming by 2100. In fact, the median projection is for 2100 warming of 2.2 degrees Celsius." He adds that that "is within spitting distance of the Paris Agreement goal of holding temperatures to a warming of 2.0 degrees Celsius."

Under the 2015 Paris Climate Change Agreement, signatories committed to "holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels."

So man-made global warming of 4°C by 2100 above pre-industrial levels is not a real possibility.

"Is the world ready for good news on climate?," asks Pielke. Yes, we are.

NEXT: The CDC Stands Firm on 'Universal Masking' in Schools as Blue States Abandon That Policy

Editor's Note: We invite comments and request that they be civil and on-topic. We do not moderate or assume any responsibility for comments, which are owned by the readers who post them. Comments do not represent the views of Reason.com or Reason Foundation. We reserve the right to delete any comment for any reason at any time. Report abuses.

  1. Enough waffles to drown South Florida in the syrup.

  2. Pre-industrial age we were (and still are) coming out of an ice age. Some thousands of years ago, my property was under hundreds of feet of glacier. Anything to get a rise out of the SLR cult.

  3. Under the 2015 Paris Climate Change Agreement, signatories committed to "holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels."

    And impossible metric.

    1. That's bumper-sticker bullshit, not to be taken seriously.

    2. Cute how he didn't mention that our CO2 emission reduction ACCELERATED under trump AFTER he pulled out of the Paris accord because of the massive increase in nat gas production and correlating decrease in price under trump.

      1. NatGas is the new enemy of the econutz. They now want to ban even gas stoves, no doubt your gas grill will be next.

      2. China and to a lesser degree India will be the primary drivers of global warming due their increased use of coal.

        Here is my experience moving to Los Angeles in 1979:
        Smog was very noticeable and I developed chest discomfort. My boss laughed that when my lungs sufficiently got coated with a layer of smog my discomfort would cease(it did).

        2022: There are twice as many vehicles on L A roads than there were in 1979, when smoking polluting cars were common on the freeways.
        With emission controls modern cars are vastly cleaner and more efficient and extreme smog warnings are rare.

      3. I remember the good old days, I think we were energy independent before the greenies decided that was a bad thing. They will never change. It is their religion. We have to change policies by changing the government and fortunately we will, very soon. Now if the Republicans can just grow a spine.

    3. “ ... holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels.”

      Why do warmenists keep using this metric?

      The baseline that matters is what the global average temp would be *now* in the absence of human added GHG’s. Asserting it would be the same as 400 years ago is climate denial on stilts.

      One almost gets the idea they have no idea what our added warming really is, because they don’t have the means to figure out what it would be otherwise.

  4. Why must Ron turn to axe grinders like Pielke when so any sensible critiques of doomsday scenarios like RCP 8.5 have been published in the climate science literature ?

    Hype and denial have reached Biblical proportions:
    https://vvattsupwiththat.blogspot.com/2022/02/climate-denier-gets-off-on-wrong-foot.html

    1. Ron is reporting on this study because it is new, because it is his job to report on science _news_. He isn’t “turning to” anything.

      1. It's not new though. It's what anyone actually familiar with the science has known for years.

        Anyone with half a brain has known these models far underestimated the role of clouds and the sun in the historic climate models, which made all their future predictions complete garbage. I mean we know the suns activity increases and decreases in cycles, as well as its temperature/energy output. The mounder minimum/maximum is real. Sunspots and solar activity are real. And they have FAR MORE influence on our climate than CO2.

        They're finally coming around to their historic cloud cover errors, maybe in 20 more years they'll finally factor in the sun correctly.

        But you didn't know that because you've got less than half a brain.

        Maybe if you combine the brain power of all your socks you might be able to outhink a dog turd.

        1. Another wannabe Pielke coauthor?

          1. Derp... Still waiting to hear back from media matters on how to refute the new climate data...derp

  5. Oh, the political science reporter is back.

    Bailey, I think Sullum replaced you as the STEM science-y reporter.

    1. Carbon belching Bailey is back! And in pog form.

  6. The only real question is whether less catastrophic climate change predictions should be classified as mis-, dis-, or mal-information.

    1. Just call it MDM and you got it covered.

    2. Classify it herding sheep.

  7. More testing will solve this problem!

    1. Better modeling, to fit the predicted outcome, is the preferred technique of the climate cult. Because, the science is settled.

      1. Hey now. They will continue changing historical records to match models if you keep complaining.

        1. I'm glad you know that too. Too bad Bailey n reason don't.

          3 years ago I remember reading an article about how the climate reference in core samples from 20,000 years ago they were using to compare to current day actually existed in a climate with far more cloud cover than previously thought.

          That means that the 4. 5 degree Celsius or whatever change theyre saying happened and is so terrible is actually being measured from a time period that was colder than average (due to more clouds/shade) and thus makes the "global warming" look like a bigger change than it actually is.

          They've basically been saying "the temp went up 4 degrees above average OMG" when in reality it went from -3 to +1 above average.

  8. This was always the case for anyone with a modicum of intelligence who thought about it for about two minutes...

  9. Of course they're highly improbable, they're literally the worst thing that could possibly happen.

    /Malcolm Tunney

  10. They started out lying, and are lying still.
    Ignore anything about global-climate-warming-change.
    No matter the question, the answer is fascism.

  11. Masking is fading, bring back climate stuff!

  12. Weird how often the "anti science" folks seem to understand science better than the people who FUCKING LOVE SCIENCE!

  13. Oh great, more fucking experts.

  14. Is there any way to make the whole planet freezing cold all year long?

    1. CW-7

  15. According to a recent WSJ article the modeling of the effects of clouds in all the computer models is known to be erroneous in the sense that the simple models are more consistent with reality than the allegedly more refined models:

    https://www.wsj.com/articles/climate-change-global-warming-computer-model-11642191155?st=3irn1ksrzv2p2yp&reflink=desktopwebshare_permalink

    1. So is the modeling of air pollution. Both merely act as knobs to try to fit historical data into a given model.

  16. CO2 can only raise the temperature by 1.2dC per doubling of CO2. Any projected warming beyond that is a result of positive feedbacks, IE warming because of warming. I find this very difficult to believe, as do several published climate scientists. Remember, today's science is just that, today's science and climate science isn't like Newtonian physics where you can run a controlled experiment and prove your theory. So it is certain that some, if not most of what we are told by "science" today regarding the climate will be shown to be wrong in the future. There is absolutely no way with our current understanding that we can predict with accuracy what the global temps are going to be at the end of the century. Science isn't religion...keep an open mind.

    1. And the heating is logarithmic. The 1.2 is based on perfect absorption of heat from carbon as well.

    2. Agreed. Models should not be sold as if they are hard science.

    3. "CO2 can only raise the temperature by 1.2dC per doubling of CO2."

      For Zimbabwe to get to the level of the US in terms of per capita emissions, doubling is not enough. They will have to increase their emissions twenty fold.

  17. Sorry, the word "implausible" is not permitted in Science®.

  18. Thanks for another edition of "Ronald Bailey cherry picks the minority scientific view most favorable to conservative politics."

    1. You mean to tell me that the IPCC is a minority scientific view?:

      The IPCC's AR6 report, released in August 2021, now acknowledges that "the likelihood of high emission scenarios such as RCP8.5 or SSP5-8.5 is considered low in light of recent developments in the energy sector."

      So pray tell, who represents the majority scientific view?

      1. The 35,800 Goddamn science journals serious libraries subscribe to, not the vanity press productions ex-Enron PR flacks subsidize.

        How many have you read this year ?

  19. None of the AGW crowd ever stops to consider that "past results to not indicate future performance" in the parley of a stock broker.

    We are entering a period of decreased solar activity, which is cyclical and has happened repeatedly. Even as the early 1800's, when we were coming out of a solar minimum, the Thames River froze over for the last time in recent history. The year 1814 was the last "Frost Fair" in London where a fair was held ON THE ICE. The year 1816 was the "year without a summer" with famine in many areas of the Northern Hemisphere.

    Cold is always the problem...NEVER WARMING. Empires rise during warming periods and fall during cooling periods.

    What is the "correct" temperature of the earth? Here's a hint...NO ONE KNOWS. On a daily basis temps rise and fall more than 20F. What difference would 1 or 2 degrees really make?

    Again...cold is the issue, not warming.

    1. Two words: Mount Tambora.

      1. Don't forget:
        Telluric Currents
        The Iron Sun
        Underwater Volcanoes
        and
        Galactic Cosmic Rays

  20. "So man-made global warming of 4°C by 2100 above pre-industrial levels is not a real possibility."

    Maybe it's true that global AVERAGE warming won't hit 4 C, the problem is the right end of the bell curve. Like the heat wave that hit the town in BC last summer, 121 F if I recall, a record for Canada. The town was evacuated and a fire broke out and obliterated the town, not to mention killing lots of people.

    1. Record heat wave in Canada is evidence of global warming.
      Meanwhile, record 6 month cold spell in Antarctica is fact-checked as not being evidence that global warming is wrong:
      https://www.reuters.com/article/factcheck-antarctica-cold-idUSL1N2RZ1X4

      Bonus points for naming the fallacy(s) being employed in both cases.

      1. If you shift a normal distribution to the right, the right hand end is going to get more extreme. Longer, hotter heatwaves in the summer will kill the crops humans depend upon for survival. And, no, air conditioners are not going to save them.

        1. Unless you grow the crops in a cooler climate. Kansas may be too hot, but you can grow it a few hundred miles north. People may choose to move away from places that are too hot too, and have fewer babies, so not as much food will be needed.

          1. The town in BC that was wiped off the map was more than a few hundred miles north of Kansas.

        2. This is false. Warming climate will increase available crop land. As the climate warms we don't become a desert. It would introduce billions of gallons of water into the ecosystem that would lead to increased precipitation in areas that currently do not get it.

          As recently as 10, 000 years ago the Sahara had lush plains and water. The hanging gardens of Babylon were built when Babylon, present day iraq-area, had lush tropical forests.

          Warming temperatures would increase farm able land drastically across the globe

          1. Don't argue with the fanatics. They're immune to facts.

  21. LOL the UOC can study all they want. The last time the planet had 420 ppm co2 in the atmosphere, there were no polar ice caps. A 20 ppm swing normally takes 200,000 years or so. It might take a while but Mother Earth will catch up to what we did in a couple of centuries. Unless we start scrubbing co2, we are already fucked.

    1. Well, then you'd best nip off and eliminate your entire genetic line to save them the suffering in the future. I recommend arsenic!

  22. The current level of atmospheric carbon dioxide is just under 420 ppm, and that is up from the pre-industrial level of about 280 ppm.

    This is only true if you severely limit the 'pre-industrial era'.

    If you include, say, all of human history then CO2 levels were often higher than 420 PPM.

    And if you include the entirety of hominid history, the average PPM of CO2 is around 1000.

    Because humans evolved in a warmer wetter world.

    It's looking as if ALL of The Science(TM) is turning out to be bullshit, Ron. From climate to gender to covid.

    Why not give up the pursuit of progressive fame and come back to the real world?

    1. "If you include, say, all of human history then CO2 levels were often higher than 420 PPM."

      Human history goes back only some 5000 years when the art of writing was invented. I doubt CO2 levels were ever as high as 420 PPM are recorded. 'Pre-history' is the word you are looking for. Civilized human life has never been sustained with CO2 at 1000 PPM.

      "It's looking as if ALL of The Science(TM) is turning out to be bullshit"
      You doubt the heat trapping characteristics of green house gases?

  23. making northern canada and siberia more hospitable would be the worst thing that could ever happen to earth. The two largest land masses on earth only being suitable for about 8 endangered animals is perfect and we should do everything in our power to make sure it never ever ever changes.

    1. Change is inevitable. Concentrate your efforts in areas where you can make a difference.

      And, by the way, Africa is larger than Canada and Siberia combined.

      Also, Tamora.

  24. 60-yrs of one dier prediction after another..., that never happened. Yet..., this nonsense still gets hyped EVERY F-ING DAY!!! The folks that buy into this nonsense r the true human hating morons of society. These r the same idiots moving to the coast and wearing a face diaper. I guess rising oceans and co2 r only "problems" in group speak. As these individuals seem to love breathing in EXTRA co2 in thier face diapers and living large in a "temporary" home. Stupid is as stupid does.
    The Phucko Knows

  25. "Global Warming" "Climate change" "Climate disruption" whatever stink label you want to put on it. It isn't about change it is about control. Just be honest and move on to your next fascist step.

Please to post comments

Comments are closed.