Is climate change an existential threat to humanity?

Summary: The Climate Emergency assumes that climate change is an existential threat to humanity. Climate scientist Cliff Mass examines the evidence for that theory.

Burning Earth with smoke
ID 50590315 © Strahil Dimitrov | Dreamstime.

Is global warming an existential threat?”

Probably not, but it’s still a serious issue.
By Cliff Mass at Weather and Climate, 12 August 2019.

During the recent presidential debate, a number of candidates suggested that global warming represents an existential threat to mankind, and thus requires dramatic and immediate action. Governor Jay Inslee has been particularly generous in the use of this term {details here}, but he is not alone. Kamala Harris, Cory Booker, Bernie Sanders, and Elizabeth Warren have said similar things, as have several media outlets and environmental interest groups.

Some also claim that the window for action on climate change is closing. Jay Inslee suggests that the next president will be the last able to take effective steps. Others suggest 10 or 12 years.

Are these existential threat claims true?

An existential threat is one that threatens the very existence of mankind. Something that is simply a challenge or an inconvenience is not an existential threat. An existential threat must have the potential to undermine the very viability of human civilization.

As described below, global warming is a serious problem and its impacts will be substantial – but in no way does it seriously threaten our species or human civilization. And with reasonable mitigation and adaptation, mankind will continue to move forward – reducing poverty, living healthier lives, and stabilizing our population.

What do current climate models tell us? These models are run under specific scenarios of emission of CO2 and other greenhouse gases (see figure). In one, RCP8.5, we simply continue doing what we are doing, with escalating use of coal and oil and little use of renewable energy. Many believe this scenario is too pessimistic.

Editor’s note: for more about RCP8.5, see these.

Is our certain fate a coal-burning climate apocalypse? No!
• “Is RCP8.5 an impossible scenario?” by climate scientist Judith Curry.

Much more reasonable is RCP 4.5, which has modestly increased emissions through 2040, declining after 2050. I suspect this one will be closer to reality.

Updated graph of CO2 emissions from Fuss 2014
Updated graph from “Betting on negative emissions” by Sabine Fuss in Nature Climate Change, October 2014.

The implication of these emissions on global temperature is shown below based on a collection of climate models (CMIP-5). Under the extreme scenario, the earth warms by about 4°C (7.2°F), but for the reasonable one (RCP4.5), global warming is about 2°C (3.6°F). This warming will not be uniform, being greater in the polar regions, less over the eastern oceans.

Change in global average temperature by RCP
From Climate Change Canada website.

You will note the temperature rise in RCP 4.5 is relatively steady through around 2045 and then gradually plateaus. No sharp transitions, no falling off of a cliff, no sudden catastrophes.

I have run a large collection of high-resolution climate simulations over the Northwest, driven by the aggressive RCP 8.5 scenario. As shown for Seattle’s mean annual temperature below {click to enlarge}, there is a steady rise, again with no sudden changes that would be hard to adapt to. Most NW folks will want to purchase an air conditioner for summer, but there is no threat to our existence, and winters will be more pleasant.

Seattle Temperatures - Past and Future

Look at economic projections.

First, let’s check the conclusions of the highly respected Intergovernmental Panel on Climate Change (IPCC), which provides a consensus view of scientists and nations. Their analysis (SR15, Chapter 3) quoted a paper by Yohe 2017 (open copy) that found a U.S. GDP loss of 1.2% per degree of warming, So with a 2°C global warming associated with RCP4.5, we are talking about a 2.4% loss of national income in 2100. Not a 2.4% loss from today’s levels, but 2.4% less of the substantially greater income in 2100.

What about the recently released Fourth National Climate Assessment, a document heavily cited by the U.S. environmental community? Their analysis is that the damage to the U.S. economy in 2100 would be about a 1% loss (see below) This is not a 1% loss from the current U.S. gross domestic product (GDP), but a 1% loss of the substantially great GDP in 2100. We will be much richer in 2100, and will lose 1% of our GDP because of global warming. That would not be the end of civilization.

Global CO2 Emissions - Damage to the US Economy
Figure 29-3 from Chapter 29 of the Fourth National Climate Assessment. Click to enlarge.

William Nordhaus, who won a Nobel Prize in economics for his study of the economic impacts of climate change, examined a large number of studies regarding the impacts of global warming on the world’s economy (see below). He and his co-author (A Moffat) found that a 2°C increase in global temperatures would result in 0-1% damage to the world economy in 2100. Doubling the warming would only increase the damage to around 3%. Again, no existential threat.  {See the paper here. Click the graph to enlarge.}

Damage and Temperature Estimates from Major Studies

Reading these numbers and considering the many reports backing them up, there clearly is no existential threat to either the U.S. or mankind from global warming, leaving one to wonder why are so many politicians, environmental activists, and lots of media are spreading this existential threat line.

And the above studies are not considering the potential for major technical breakthroughs in energy generation (e.g., fusion), renewables energy sources, or carbon removal from the atmosphere (sequestration). I believe that such advances are inevitable but underestimated, just as no one in 1950 expected that 2000 would bring personal computers and cell phones.

You also have to wonder whether scientists, politicians, and environmental folks really believe the existential threat warnings they throw around. Many talk the talk, but few walk the walk.

Presidential candidates with little chance of securing the nomination are flying across the country, leaving enormous carbon footprints. Climate scientists fly more for work and pleasure than most. Many environmentalists oppose nuclear power, one of the technologies that could produce massive carbon-free energy. And several local Washington State environmental groups opposed a revenue-neutral, bipartisan carbon tax initiative (I-732).

Global warming is a real issue and we are going to slowly warm our planet, resulting in substantial impacts (e.g., less snowpack in the Cascades, increased river flooding in November, drier conditions in the subtropics, loss of Arctic sea ice). But the world will be a much richer place in 2100 and mankind will find ways to adapt to many of the changes. And there is a good chance we will develop the technologies to reverse the increasing trend in greenhouse gases and eventually bring CO2 concentrations down to previous levels.

Global warming does not offer an existential threat to mankind. Politicians and decision-makers only undermine their credibility and make effective action less likely by their hype and exaggeration. Their unfounded claims of future catastrophe prevent broad national consensus and hurt vulnerable people who are made anxious and fearful. And just as bad, all this end of the world talk results in folks turning away from the issue, both out of fear and from an intuition that a lot of hype is going on.

This is a follow-up to the previous post by Professor Mass:
Another climate scientist speaks out against the hysteria.


Cliff Mass

About Cliff Mass

Cliff Mass is a Professor of Atmospheric Sciences at the U of Washington, and leads their Mesoscale Analytics and Forecasting Group. See his home page at the U Washington websitehis Wikipedia entry. and his website. He is the author of The Weather of the Pacific Northwest.

For More Information

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 about this vital issue see the keys to understanding climate change, and especially these …

  1. Importantclimate scientists can restart the climate change debate – & win.
  2. Focusing on worst-case climate futures doesn’t work. It shouldn’t work.
  3. The IPCC gives us good news about climate change, but we don’t listen.
  4. Roger Pielke Jr.: the politics of unlikely climate scenarios.
  5. A look at the workings of Climate Propaganda Inc.
  6. Scary but fake news about the National Climate Assessment.
  7. Did the IPCC predict a climate apocalypse? No.
  8. Sad but important truths from an eminent climate scientist.

Activists don’t want you to read these books

Some unexpected good news about polar bears: The Polar Bear Catastrophe That Never Happened by Susan Crockford (2019).

To learn more about the state of climate change see The Rightful Place of Science: Disasters & Climate Change by Roger Pielke Jr., professor for the Center for Science and Policy Research at U of CO – Boulder (2018).

The Rightful Place of Science: Disasters and Climate Change
Available at Amazon.


28 thoughts on “Is climate change an existential threat to humanity?”

  1. Excellent article. The biggest problem about climate change cannot be over-emphasized: We simply don’t know with any reasonable certainty whether there is an existential threat or not. A few of specifics:

    William Nordhaus’ models of econiomicmimaoct of climate change have been widely criticized by people who are not “climate activists”.
    If climate change turns out to be an existential threat, by the time we are certain it will be too late to change.
    If climate change is not an existential threat, by the time we know for sure it will be too late to get back any money that it turns out was wasted.

    1. Assuming Nordhaus is correct, the correct path is to invest in ourselves. Education, research, gradual change such that we get the economic value of investments, etc. If one looks at the costs of 1% world GDP used now for solutions that will not work well, solar and wind, the loss of income and growth affects the most vulnerable in the world. IMO, that should be added to the large list of hypocritical actions by the social justice warriors of climate change.

    2. Even if Climate Change is a big no show, personally i think its a good idea to stop buying Made in China stuff at Walmart and/or Target. or just plastics in general.

      As far as cars go, I’ve been to a few 3rd world countries, where smog is really bad. Take the bus! or walk or bike. In California , you kinda have to have a car since everythings spread out, but when I was in the East Coast, i took Amtrak and metros, the cities are connected there.

      it’s pushing $5 buck per gallon in California now, so I’d rather be driving a Tesla. i’m hoping Tesla’s get as cheap as Civics. i knew a girl whose Nissan Leaf burned to the ground, battery issues. So i know it’s not totally perfected yet.

      my point is, even if there is no Climate Change, helping out China by buying too much plastics, or smelling inhaling all that smog, life style stuff like that we can totally adjust for right now.

      Scale it up, legislate no buying Chinese plastic. in a way, Trumps tariff war is just that, but i’ve been telling people to stop buying crap at Walmart and Target since early 2000s. its a big welfare workforce anyways, i don’t support that crap.

      As for solar, i know the bulk of the breakthrough that’ s needed is battery tech, once they figure out how to store all that power/electricity solar makes, then we should be good. but me buying a Tesla, and becoming off grid solar only is still far fetch,

      but not buying anymore plastics is totally doable today, i’ve been doing it for awhile now.

      1. LCpl,

        Who told you that “not buying plastics” or “Mad in China” would affect global warming to any meaningful degree? They were lying to you.

        Ditto about smog. It is unrelated to climate change. If all the old cars were replaced with new ones (which produce far less smog), that would have a microscopic effect on global warming. Smog results from chemicals other than CO2. See Wikipedia.

        “once they figure out how to store all that power/electricity solar makes, then we should be good”

        That’s quite unlikely.

        “me buying a Tesla, and becoming off grid solar only is still far fetch”

        Whatever about you. But electric cars have a great future as their price comes down (riding the production volume-price curve). Electricity is much cheaper than gasoline in most places. A large fraction of drivers do not drive long distances (eg, my wife has never driven 300 miles in one day). An electric car for homes with two cars, or for people who don’t need long travel, or for vehicles operating only on short hauls (taxis, trucks, farm vehicles, etc) — all become possible as their price drops. The effect on CO2 emissions will be significant.

      2. Larry, that’s why I prefaced it with even if Climate Change is a no show.

        Geo politics-wise , the USofA buying cheap plastics from China is the reason why China now is powerful. And why in Shark Tank, they always tell people to do their manufacturing in China, or some other 3rd world country, but mainly in China.

        I’m making a National Security argument, you buy in Walmart/Target you are helping China. Period, hence why I ‘m loving Trump’s tariff wars with China. but people don’t seem to appreciate it as much as they should.

        As for smog, I don’t think maybe you’ve been to a 3rd world country and come home with black soot, literally from you nostrils. that’s gross, I don’t know if that’s related to Climate Change, but breathing in all that crap is I’m pretty sure unhealthy. thus avoid it.

        As for electric cars, yup i’m waiting for it to come down to a comfortable price point, until then it’s cheaper to take the bus and/or rail. CO2 is above my pay grade, i’m just saying $5 bucks a gallon is nuts! thus electric is better.

  2. Excellent.

    ”all this end of the world talk results in folks turning away from the issue, both out of fear and from an intuition that a lot of hype is going on.“

    Greta and Extinction Rebellion did greatest disservice to the cause in years.

  3. Thanks, excellent article. Reality and common sense is RCP4.5. The trick is getting that number and it’s meaning out to the public.
    The real existential threat to humanity is doomsters (mostly politicians and the MSM) pushing RCP8.5.

    1. Mike,

      Thanks for that link! This is business-as-usual on the Left. Authorities are trustworthy only to the extent that they support the Left’s narratives. Nobel prize notwithstanding, Nordhaus becomes a tyro to a Leftist economist when his work does not support the Climate Doomster Narrative.

      It is a mystery why anyone pays attention to complex econometric models like the IAMs. Economic modeling is in its infancy. Simple predictions three months out are unreliable. The fantastically complex assessments produced by the IAMs are akin to witchcraft – with the computers much like the Witch Doctor’s drums, smoke, and dancing.

      1. Steve Keen is not a ‘mainstream’ economist. He is the author of “Debunking Economics” and an outspoken critic of neoclassical economics. I suggest watching this 15 min video clip of Keen himself to get a flavor of his take on Nordhaus’s work. It’s important I think.

      2. Mike,

        I am familiar with Keen’s work. I’ve critiqued this overblown claims to have predicted the 2008 crash (he was indignant). He is on the fringes of economics, with a following mostly of people who know little about economics.

        I looked at his rebuttal at NC. It’s ridiculous, mostly pearl-clutching that Nordhaus’ work does not support the Left’s narrative.

        “Given the urgency that characterises the Global Warming debate, this is, on the face of it, an extremely benign view of the impact of an increase in the global average temperature on GDP.”

        Much of it is false, ignorance of science (typical Keen).

        “6 degrees is well above the threshold at which all of Greenland and the Antarctic will melt completely (even if it’s the Sun’s fault, rather than AGW).”

        Such melting would take centuries or millennia (depending on the model), far beyond our ability to predict anything – and is irrelevant to calculations of GDP for 2100.

        I could go on, but why bother?

      3. Mike – follow-up note.

        Like a good doomster, Keen focuses on the most extreme scenario. Warming of 6°C is beyond the upper limit if the RCP8.5 scenario – which is itself either wildly improbable or impossible.

        He also frets about life 130 years from now. Whatever life is like then, we can’t imagine it. Any more than the people of 1889 could see our lives and our problems. After 50 years or so in the future, the world will be radically changed. The fossil fuel deposits will be mostly gone (if we’re still using them, as in RCP8.5). Underpopulation will be the problem, as below-replacement level fertility reshapes the world. And new tech will make many of our current concerns meaningless, and introduce new problems.

        That Keen or any economist things that we can foresee such distant times is hubris squared.

  4. Good post by Cliff Mass. he seems like a likable guy, despite his grumpy photo. I remember that he’s been smeared as “trumps meteorologist” before several times. Then again, people have gone batshit crazy, with repetitive charges and excuses.

    I saw that you saw Stollers article. Good article.
    What is up with this bill taylor business? I’m guessing that it probobly is a nothing burger like all the other bombshells over the past two years, due to who is reacting the most to it. Although it could be an example of the wolf finally arriving.
    A typical article
    Some back ground on the author

    1. Isaac,

      I wonder how many people, like me, have “Game over for Trump” fatigue? We had several such moments in the 2016 campaign, and countless since. I read the NYT’s excited article about the State Dept emails about Ukraine – Game Over! – but they were ambiguous, at best.

    1. Ron,

      Wow. I have seldom seen a worse-written article. Not only does it not link to most of the material it quotes, it doesn’t even give a cite to locate it. Gibberish.

      I predicted this pointless debate several years ago, and said that the best way to determine the accuracy of the models was to rerun those used in previous IPCC Assessment Reports – esp the 2 – 4 – using actual forcings (eg, CO2), not guesses as to future forcings. Then compare their forecasts (ie, hindcasts using real inputs, not scenarios) with observed warming. But neither side in this Clownworld debate has any interest in such things.

      Food fights are much more fun.

      1. Larry,

        Yeah, that blog gets low ratings. For the life of me, I fail to understand how ~3mm of sea level rise per year and 200ppm more of CO2 is something to panic about.

        In simple terms, it looks like BS to me. Politics and religion, science not so much.

      2. Ron,

        There is no doubt that large-scale adaption measures would be necessary if we follow the RCP6.0 scenario – and it is worthwhile to spend quite a bit of money to avoid it. This is why Prof Mass says that this is a serious problem. Even under the milder scenarios, some expensive measures will be needed.

        If we find we’re on the path to RCP8.5, extremely drastic measures will have to be taken ASAP.

        There are other variables, too complex for a general discussion. One of the big ones is the sensitivity of weather to rising CO2. This number is estimated today only within a factor of 2x, perhaps 3x. If it is in the high end of the range, then even RCP6.0 will be ugly.

        “In simple terms, it looks like BS to me.”

        I know of no scientists – “skeptic” or otherwise – who agrees with you. That’s pure denialism, a pox on the climate debate resulting from the mad polarization of our politics.

      3. Larry,

        “There is no doubt that large-scale adaption measures would be necessary if we follow the RCP6.0 scenario – and it is worthwhile to spend quite a bit of money to avoid it”

        If and how much is the question. “Green” energy in present form isn’t up to the task. No time to panic at RCP4.5 and certainly not at the Green New Deal level of $16T.


      Whether or not Climate Change happens i’m seriously not worried. If it happens, i’m gonna make sure i’ll be in that “breeding pairs” number,

      “The Toba eruption has been linked to a genetic bottleneck in human evolution about 70,000 years ago, which may have resulted from a severe reduction in the size of the total human population due to the effects of the eruption on the global climate. According to the genetic bottleneck theory, between 50,000 and 100,000 years ago, human populations sharply decreased to 3,000–10,000 surviving individuals. It is supported by some genetic evidence suggesting that today’s humans are descended from a very small population of between 1,000 and 10,000 breeding pairs that existed about 70,000 years ago.”

      I’m assuming most scientists and liberals will be busy being political correct, and being too compassionate, caring about human rights this and rule of law that, well may the best sperm wins! because i plan to partake. the Japanese have opted out, so has Europe and English speaking N. Ameria— i’m sure Australia too. i’ve been to the 3rd world and there are a bunch of “breeding pairs”. seems like that’s all they do there.

      whether 10,000 or 10 billion, who cares about the politics , i’m not gonna let my little tadpoles down, i’m delivering them where they need to go, like Genghis Khan or Niall Noígíallach. Climate Change or Not, these will be “breeding pairs”.

      Too much Climate Change focus, not enough in the related tangent that is DNA/genetics. While the West is debating, the East, and everywhere else, is pounding out their DNA to posterity. IF that Toba eruption theory stands, then whatever side of the debate youre on, Climate Change YES or Climate Change NO, genetically speaking you’re still screwed.

      Assuming not commenting here is from the 3rd world.

      1. An all out nuclear war would do the trick in a hurry. They now call a big Nor’easter a “bomb cyclone”. Whatever.

  5. It is a fascinating article that supports the idea that we do not face an existential threat.

    However, the way it presents the data is misleading. The IPCC defined four regimes, named RCP2.6, RCP4.5, RCP6, and RCP8.5. The article spends little time examining RCP6: it describes RCP8.5 as “extreme”, “pessimistic” and “aggressive”; RCP4.5 is “reasonable”, while RCP2.6 is too optimistic to merit discussion.

    So let’s be “reasonable” and pick the scenario in the middle: RCP4.5.

    The problem is that RCP4.5 is itself too optimistic. It requires CO2 emissions to peak in around 2040, only 21 years in the future. I suggest that RCP6 is more realistic: improvements in agriculture, cement manufacture and iron smelting will take decades to have effect. RCP6 has slower growth in CO2 emissions than RCP8.5, which agrees with the expansion of green energy generation; and its CO2 emissions do not peak until 2080, which matches the fact that the reduction of other anthropogenic CO2 sources has scarcely begun.

    Picking RCP6 instead of RCP4.5 does not alter the conclusion that there is no existential threat to our species; but overstating the case by picking RCP4.5 is not only poor science, but a political trap. As the years progress and we move ever further from RCP4.5 predictions, the climate hysterics will say that they were right and the scientists were wrong. When CO2 emissions have not peaked in 2040, they will say that we are facing a “runaway greenhouse effect” and other alarmist nonsense. If we predict that emissions will start falling in 2040, this will feed the extremist notion that we face a “point of no return”, within a politically comprehensible time scale.

    Even to push the world from the “business as usual” RCP8.5 to RCP6 is an ambitious target that will require substantial effort and spending over a period of several decades. I fear that RCP4.5 is simply unachievable.

  6. Some also claim that the window for action on climate change is closing. Jay Inslee suggests that the next president will be the last able to take effective steps. Others suggest 10 or 12 years.

    Neither this nor the next nor any future president can take effective steps, and you can see this clearly from the charts. The US emits around 5 billion tons a year, and is not going to rise much over the coming years and decades. Whereas the world is emitting 37 billion now, probably rising to 40+ billion, mainly driven in the immediate future by China and India.

    US Presidents can only reduce this 5 billion, and politically it is going to be impossible to reduce it by much more than a couple of billion. This will have pretty much zero material direct effect on global emissions. And it will have zero indirect effects since no-one is looking to the US as a model and example for anything nowadays.

    The continual fallacy that is found in US writing and agitation on this subject is the false assumption that once you have shown there is a global emergency you have justified or mandated US local emission reduction action.

    That is dangerously false. Its like Tuvalu reducing its local emissions in the effort to avert sea level rise.

    You also have to wonder whether scientists, politicians, and environmental folks really believe the existential threat warnings they throw around.

    Yes, this an entirely correct observation. There are undoubtedly a few fanatics who probably really believe the apocalyptic predictions of doom, but there is precious little evidence any policy makers do. Certainly not outside the US and UK.

    If policy makers really believed the emergency predictions, they would not be seeking to lower local emissions. They would be embarking on massive defensive preparations to safeguard the population, and they would be agitating like crazy to get global reductions, and specifically persuading China and India to stop increasing and reduce.

    Whereas in fact, the objective everyone seems to be working towards in practice is that global emissions shall remain at current levels or rise, while the US reduces and does nothing to safeguard the population and facilities.

    This is not the stance of people who genuinely believe in the coming apocalypse.

    But even supposing that for some unaccountable reason they decided that the priority was to seriously reduce or eliminate local emissions, they would still not be doing what they are now, because nothing they advocate will do that. Its not just their personal footprints. They would be advocating large scale movements of population into dense energy efficient housing, the abolition of the auto industry, the demolition of the suburb+mall culture. This is what it would take to drop local emissions by several billion tons a year. No-one is seriously advocating doing any of this. Its just modest amounts of wind and solar and business as usual.

    They just don’t believe it, judging by their actions. And as for the Chinese and Indians, its even more obvious they do not believe it. The Chinese are installing coal fired power stations like there was no tomorrow, not just locally but around the world. This is a regime that simply does not believe in CAGW at all.

    Finally, Larry believes electric cars will make a dent in emissions.

    But electric cars have a great future as their price comes down (riding the production volume-price curve). Electricity is much cheaper than gasoline in most places. A large fraction of drivers do not drive long distances (eg, my wife has never driven 300 miles in one day). An electric car for homes with two cars, or for people who don’t need long travel, or for vehicles operating only on short hauls (taxis, trucks, farm vehicles, etc) — all become possible as their price drops. The effect on CO2 emissions will be significant.

    Yes, absolutely, to the first part. No to the concluding line. They will make a huge dent in city particulate pollution and city air quality. And noise reduction is a big plus, too. And lower maintenance costs. But I don’t believe that over their lifetime they will make much difference to CO2 emissions. Recent studies I have come across suggest they will even raise net CO2 emissions. But whether they make modest reductions or increases, they are still a good thing, agreed with that.

    1. Well, that’s my point above…

      take out CO2 emissions from the equation. and just ask…

      can you do w/out plastic especially from China? the answer should be YES.
      can you do w/out smog, no matter its connection to CO2 levels? the answer should be YES.
      can you do w/out gasoline cars? sure, the tech needs to catch up and price point lowered, but the answer again should be YES, electric cars are superior.

  7. Pingback: Klimawissen­schaft ist gestorben. Die Auswir­kungen werden erheblich sein. - BAYERN online

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