Global Warming: the Relentless Trend

When it comes to global warming, recent years have been so hot that it worries even those who deny the problem exists.

No one more desperately needs global warming to end than those most against doing anything about it. That’s why they cling so tight to the notion of a “pause” in global warming, a “pause” that was never more than a false impression, hoping others would believe the myth that it had all somehow stopped. Its death by thermometer has hit them hard.


Yet they can look forward to new pauses to come. The year 2016 was so hot it shattered the previous record by a country mile, boosted as it was by the temperature spike which always follows a powerful el Niño. That leap upward, the hot flash Earth feels after el Niño strikes, when combined with the steady upward climbing that is global warming, yielded a powerful new peak, a highest high born of the unholy marriage of extreme fluctuation and relentless trend. It may become their new delight, this highest peak, a cherry more ripe and juicy than any before it.

And cherry-pick they will. That’s what happened after the 1998 el Niño. Way back in 2006 Bob Carter announced “There is a problem with global warming… it stopped in 1998.” It was bullshit then, it’s bullshit now, but climate deniers have made the most out of what they do best: bullshit. Bob Carter made the most of the biggest confusion about global warming, because most people don’t fully understand what global warming is. It has nothing to do with the perpetual fluctuations.

Global warming is the relentless trend.


The new cherry is so very cherry, a set-up for a whole new “pause” whether it exists or not. Just be sure to start with the big spike near the beginning; when you put such an outburst so early it’s too easy to get, and to give, the wrong idea about the trend. That’s why James Hansen and others have pointed out in a recent report that upcoming temperature data could give just such a false impression.


Therefore, because of the combination of the strong 2016 El Niño and the phase of the solar cycle, it is plausible, if not likely, that the next 10 years of global temperature change will leave an impression of a ‘global warming hiatus’.

We have been warned.

And it has already begun. The pause is coming! Witness Larry Kummer suggest that a new pause may have started already, a “pause perhaps lasting 10 or 15 years,” complete with funny picture to suggest that the “pause that never was,” was. Contrary to the impression one might get from Kummer’s piece, Hansen et al. didn’t suggest that a “pause” or “hiatus” may be on the way, they say that the impression may be. The distinction is at the very heart of the matter.


Just how likely is it then, that recent hot years can create such a false impression? Let’s suppose — just for the sake of argument, mind you — that global warming didn’t pause and isn’t going to. Rather it has been rising at a steady pace while fluctuating up and down randomly, and will continue to do so. Given that there’s no “pause” past or present, just random fluctuation and relentless trend, what might the future bring, and might it give the “impression of a global warming hiatus”?

It’s easy to simulate what might happen. Start with global temperature data (from NASA), yearly averages since 1970. Estimate the trend mathematically (least squares regression). Extend that trend line into the future, say, until 2050. That’s what the relentless trend will do, just keep on keepin’ on.

The first thing we note is that the trend alone doesn’t surpass the record high of 2016 until the year 2027. If the data from now on follow the same relentless trend with no noise, then from 2016 through 2026 we’ll have 11 years without breaking the 2016 record. How long will it take for climate deniers to declare a “pause”?

But we have no fluctuations to make the simulation realistic. So, use a random number generator to add simulated “noise” to the trend extension. Here’s one (the first one I got):

Could this give the “impression of a global warming hiatus”?

How about the 14-year period from 2016 through 2029?

It hasn’t yet exceeded the 2016 outburst; do you believe, even for a moment, that climate deniers will refrain from shouting “pause” — in spite of the fact that these data are the sum of random noise and that same relentless trend?

If I plot only that time span, even estimate a straight line trend (least squares again), I’d get this:

OMG! A fourteen-year streth with no trend at all! If anything, the globe is cooling!!! That’s what we’ll hear repeated over and over, In spite of the fact that these data are the sum of random noise and that same relentless trend. The impression of a pause is a combination of random chance with the fact that we started off with a big early peak.

Is it really just an impression? Set aside for the moment the fact that these are artificial data made of random fluctuations and relentless trend. Let’s try some valid statistical analysis:

The best-fit unbroken trend change only gives a naive p-value of 0.089, not enough to call statistically significant, and that’s without correcting for the multiple testing problem. But the best-fit broken trend, starting with 2015, gives a naive p-value of 0.011. Significant at almost 99% confidence? No. Multiple testing problem.

Monte Carlo simulations can tell us what the real p-value is for that broken trend, 0.18. Not even close. After all, it really is just random noise plus relentless trend.

Of course one simulation isn’t the whole story. So I ran 10,000 simulations.

Only 3% of them showed a below-zero trend for 14 years or more, so it turns out my first simulation was a bit extreme, but only a bit. Fully 14% shows a below-zero trend for 12 years or more, and 40% show a below-zero trend for 10 years or longer. A whopping 73% had a below-zero trend for 8 years or more; that is more than enough for climate deniers not only to claim “pause,” but to declare “proof” that global warming “stopped in 2016.”

As for long stretches since 2016 without a new record high, that too is surprisingly common given the “head start” of cherry-picking the big outburst. Fully 6% of simulations included a 12-year stretch without breaking the 2016 record, 20% had a 10-year stretch, and 43% of simulations included an 8-year stretch with no record-breaker … long enough for Bob Carter to claim that global warming stopped whether it did or not.

Global warming marches on, but as long as fluctuations happen (and they will happen) there will be plenty of room for climate deniers to say it showed a “pause.” Now that they have a new super-cherry to cherry-pick, they will deny reality no matter what the future brings. They will likely base it on exploiting the fluctuations, in spite of the fact they have nothing to do with man-made climate change. Global warming isn’t the fluctuations.

Global warming is the relentless trend.


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26 responses to “Global Warming: the Relentless Trend

  1. But Tamino you should really wait to see their Excel[lent] work before you draw any premature conclusions.

  2. You can now expect the denialati to treat your random data as though it is your prediction of future warming. Things like, “Even alarmists like Tamino are expecting 14 years of cooling. How could the true believers lose faith like that?”.
    Thanks for the analysis – a delight to read as usual.

  3. Not to discount the likelihood that some from the contrarian community will claim a pause, but it’s unlikely to be Bob Carter as he died in January 2016.

  4. I think it’s likely to wobble or pulse as the ocean cycles heat down and up the water column. The wobbles may be perceived as pauses and surges if that appeals to you, but the heat number is like the CO2 and CO2e numbers, they are all upward-sticky for the foreseeable future. I would love to be wrong about that.

  5. What is worrying is that 2017 is the second hottest year in the NASA record, beating 2015, which was partially influenced by El Nino (as 1997 was). There wasn’t the big drop we saw in 1999. So it is more plausible that we’ll have a new record in a shorter time than it took for 1998 to be beaten (nominally 7 years).

  6. Question: is it legitimate to say that the ‘relentless trend’ since 1970, ~0.18C/dec, represents the long term rate of the transient climate response (TCR), or is TCR more complex than that? Thanks.

  7. Isn’t it time that we concentrated on ocean heat content, now that we have relatively good data on that for over a decade? That’s where most of the real global warming is; the short-term fluctuations in surface temperature are mostly just the result of fluctuations in the flows of heat into and out of the oceans. Perhaps show OHC in addition to surface temperature on the same graph to show that even when temperatures are stable for a while the globe is still warming.

    • I think we have a lot more infrastructure in place for measuring surface temps so it is just a lot easier, but I think you are correct that ocean heat content is probably a better measure. As far as concentration goes, I think we need to get serious about making the CO2 and CO2e numbers go down. That is the ballgame for global warming. I want to see a year where the CO2 and CO2e numbers drop instead of rise. I don’t think I will live to see that.

  8. Everett F Sargent

    “Question: is it legitimate to say that the ‘relentless trend’ since 1970, ~0.18C/dec, represents the long term rate of the transient climate response (TCR), or is TCR more complex than that?”

    TCR is defined as a per annum increase of 1%/yr (doubling time ~70 years) with the corresponding delta temperature over that ~70 year doubling time, we are currently nowhere near that rate of increase for just CO2 (GHGe should be closer, but AFAIK GHGe is still significantly below this rate).

    So, if we currently have ~410 ppmv CO2, then a 1% per annum increase would be 4.1 ppnv/yr, but we are currently at ~2.5 ppmv/yr.

    This paper (1st one I found just now) suggests a best estimate of TCR = 1.66C/70 years (~2.37C/century) …
    Reconciled climate response estimates from climate models and the energy budget of Earth
    https://www.nature.com/articles/nclimate3066

    • Thanks for that useful discussion.

    • Thanks Everret. I wasn’t aware of that paper.

      The central figure of 1.66 C/70 years (~0.24 C/dec) is slightly higher than observed over most of the recent period, according to GISS (rather than HadCRUT4), but certainly within the error range. GISS probably resolves the spatial issue somewhat; but as the paper states, there’s also the issue of SSTs versus air-above-ocean temperatures, which may explain some of the difference. Also, there’s the possibility of TCR acceleration as ECS approaches.

  9. With all due respect (and that is a lot, and includes gratitude) to you and James Hansen, I see less risk of even the impression of a prolonged post-2016 pause.

    1. Extending the post-1970 straight-line trend probably underestimates the long-term trend going forward. The IPCC 2013 (Appendix II, WG1 report, Page 1444, RCP8.5), estimates NASA GISS values of 1.08 and 1.36C by 2020 and 2030, respectively (after adjusting from the IPCC 1986-2005 baseline to the GISS 1951-1980 baseline). The 1970-2030 straight-line regression you show has GISS at only about 1.0 by 2030. While RCP8.5 is the worst-case scenario, emission trends have been tracking closer to that than RCP6.0 or RCP4.5 (and RCP2.6 is a fantasy). Moreover, RCP8.5 does not fully represent some important amplifying feedbacks. Even the IPCC RCP6.0 projection for 2030 is above the 1970 straight-line long-term trend extension. And as noted in a recent Open Mind post, the CO2 ppm trend may be bending upward.
    The point being that a steeper upward trajectory between 2017 and 2030 reduces the chance for another “faux-pause.”

    2. While it is certainly true that a strong La Nina could depress annual GISS global average surface air temperatures for a couple of years, I would think that we have moved past some of that in 2017, the year most likely to show a post-El Nino in 2015-2016 response with a subsequent La Nina. As many including you have noted, while not a new high record, 2017 was remarkably warm given the lack of any ENSO push. As you have noted, when you take ENSO and solar out, 2017 shows up as the warmest year yet.
    Moreover, the 2017 0-2000 meter depth ocean temperature chart (Cheng, L. J., and J. Zhu, 2018, https://doi.org/10.1007/s00376-018-8011-z) shows increased ocean heat in 2017. That suggests that the ocean water is already storing up energy for another blast to push air temperature higher in the next few years vs. taking a post-El Nino break.

    3. There is reason to believe that IPO/PDO switched from the negative to the positive phase in 2014, which if true would create a 15+ year tendency for an accelerated rise in global average surface air temperature as measured by GISS.

    4. With the solar cycle peaking in 2015, and with the impact on GISS temperature showing a two-year lag (according to Hansen message 1-18-2018), we are on the downward phase of the solar cycle influence for about the next 5-6 years. Using values from Stefan Rahmstorf (http://www.pik-potsdam.de/~stefan/) and Hansen, the complete range from top to bottom of a solar cycle only drives temperature by about 0.1C. Starting around 2024 the solar cycle will be on the upswing again.

    My layperson calculations for annual average GISS in the coming years show 2018-2020 being below 2017. But 2021 could replace 2017 as the second warmest GISS year, and by 2024, 2016 could lose its top spot. While those estimates include solar but not ENSO or any volcanic cooling, the odds seem to be against any faux pause lasting beyond 2023-2024, which would provide only a 6-7 year low-slope period that deniers could use to build another delusional hiatus.

    Of course, facts do not matter to deniers and they will make up some nonsense regardless of what actually happens. However, for the reasons above I think they may have less fodder to work with than you and Hansen are worried about.

    I’d like to be wrong, but the post-El Nino temperature in 2017 suggests that we may have entered into a new phase of accelerated warming. My amateur projections suggest than using centered 11-year average GISS, every year after 2004 has been, and will continue to be, warmer than all other previous years. Using a centered 5-year average, every year starting in 2010 is warmer than all other previous years, though 2019 could replace 2010.

    The variability of single year values makes it impossible to predict the last single year not to be warmer than all preceding years, but for what it’s worth my best guess is 2028, Mora et al 2013, (doi:10.1038/nature12540) estimated 2047 as the year of “temperature departure” which = every year being warmer than the record warmest year in 1860-2005. The highest GISS for their reference baseline was 0.68 in 2005. The annual average GISS values for 2014-2017 were 0.73, 0.87, 0.99, and 0.90.

    I think Zeke Hausfather is right and that we will never see 0.73 or lower again. If so, then the year of global temperature departure would be 2014, not 2047, and yet another case of climate change arriving faster, sooner, and stronger than predicted. Meanwhile, Trump says it’s been too cold all over to use the term Global Warming.

    As Rod Serling said, we are in “…the middle ground between light and shadow, between science and superstition, and it lies between the pit of man’s fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone.” Unfortunately, this time it is for real.

    • “Meanwhile, Trump says it’s been too cold all over to use the term Global Warming.”

      On past form, anything preceded by the phrase “Trump says” has about a 2/3 chance of being mostly or entirely false. If that extended to the stock market, you could clean up by shorting whatever he bought.

      Alas, it seems he rarely pontificates on something so prosaic.

  10. The simple follow-up question is “We used to say 1998 was the peak, why have we not gone below that peak yet?”

    [Response: Hmmm… could it be random fluctuation plus relentless trend?]

  11. I encountered an interesting application of this recently. I decided to diet a few years ago, and figured that the right way to start was to regularly measure my weight. So I did, daily, first thing every morning. Early on I had a period of about 4 months where I lost 1 kg per month.
    Recently my ex was bemoaning the fact that she’d been watching her eating for 2 weeks, yet her weight had gone up by 0.5 kg. So I pulled out a graph of my weight and showed her that during the period where my rate of weight loss was a pretty steady 1 kg/month, it was easy to find intervals of 2 weeks where my weight had increased by 0.5 kg.
    And surprisingly she understood exactly the point of it (and instantly regretted the 2 days overeating that she had allowed herself because her diet had “failed”).

  12. Cassidy Scott

    This is a super interesting post to me because while your verbiage broaches on hyperbolic, you back up your claims with solid numbers, facts and your own findings. I’m wondering if you think Global Warming/Climate Change is a done deal, that nothing can really help it now? Or if there is really any hope?

    [Response: We are certainly headed for trouble, that cannot be avoided. The crucial question is: how much trouble?

    What we do over the next 5 or 10 years is key. Within a decade or two it will be so obvious that curtailing emissions is essential, that both people and governments will insist on it. The problem is, that if we wait until then to get started, de-carbonizing the economy could also be disastrous. If we get serious about it now, we’re still at the point where we can de-carbonize the economy without terrible consequences, there’s even good reason to expect net benefit from the transition to renewable technology.

    So yes, there is great hope. If we wait too long, then hope fades. My advice to private citizens: make climate change your #1 issue in the voting booth.]

    • Cassidy,
      In some ways you question misses the point. Climate change has already occurred, so in that sense it is a done deal. The question you care about is what are the consequences of the change–and these get exponentially worse the more temperature rises. Climate change is not like a video game where you reach some threshold of defeat and it’s “Game Over”. At least up to the point of human extinction, we have the possibility of making it better or worse–perhaps much worse.

      Everything we do matters, even if it seems too insignificant to worry about, because even the smallest actions can buy time to come up with better solutions. That said, individual actions by themselves cannot win this war. We have to literally change the way people live on this planet–and that means everybody. The old wisdom said, “Think Globally. Act Locally.” Good advice, but we need to get good leaders into decision-making roles that can take responsible action on a global scale. Politically, we need sweeping change. Make waves and then ride the wave.

  13. So what are YOU doing about it? you keep driving that car, heating your home, using electricity (coal), flying on jets, you leftists are such hypocrites. You just want the gummint to do something, but you just pay it lip service.

    [Response: A challenge to all readers: identify the logical fallacies (and other flaws) in this statement.]

    • I don’t usually bother to think about a response like JB’s because it is so ignorant, offensive and provocative. I usually just skip over that BS because I don’t think these folks can be reached from the kind of discussion/argument that can be mustered from a scientific and/or leftist perspective. That said, if I bothered, I would simply respond to JB that:

      “What am I doing about the problem? I am supporting carbon tax that could actually scale up to address the problem. The tax revenue would create funding to facilitate the systemic change and buffer the huge economic challenge that will accompany a meaningful global response to climate change. This is a problem created by large scale systems that rely on fossil fuels and can not be addressed by individuals changing light bulbs or turning down the thermostat. I am also committed to treating individuals respectfully and I choose to avoid provocation and name-calling as our species seeks a response.”

      I guess the primary logical fallacy with JB’s comment is tu quoque, the appeal to hypocrisy, and ad hominem, personal attack. These are some effective strategies to avoid engaging honestly.

      Mike

      • Robert McLachlan

        True, but there is more to it than that. First, the hypocrisy argument is extremely attractive to many people. Most of us really hate hypocrisy and it can sometimes defeat any rational argument. John Baez has discussed some research on this at https://johncarlosbaez.wordpress.com/2017/07/26/liars-and-hypocrites/. Second, climate change is a collective issue that (in my view) has to be attacked at all levels simultaneously, and one of those is by individuals. If there were a huge groundswell of people drastically cutting their emissions and also calling for rapid action by local and central governments, that could have an effect greater than “negotiations as usual” which is what we have now, too much of the time.

      • Hey RM,

        There is no question that the hypocrisy charge sways folks, but it is a logical fallacy, so just an answer to the question that Tamino posed: to identify the logical fallacies.

        Second: many folks have made lots and lots of changes in their lives to reduce their carbon footprint and the cumulative impact of these changes is absorbed and overwhelmed by large system fossil fuel infrastructure. Just look at the acceleration in the rate of accumulation over the past two decades and recognize that the acceleration has happened at the same time that many, many people have taken every step they can think of to address the problem. I think it’s apparent that individual action is graceful and wonderful, and ineffective at addressing the problem of global warming.

        Think of fossil fuels like the institution of slavery or chattel labor. Lots and lots of us can say, no more, we won’t own slaves, then look back and find examples that suggest that individual actions, even in large groundswells, created the kind of societal changes that we are talking about when we talk about moving away from an economic pillar like slavery or fossil fuel use.

        Plus, you do everything you can think of, you are really serious about it and a person like JB comes along and slings mud with the effective, but fallacious, hypocrisy canard. That’s a conversation/progress stopper.

        Yes, we have to do everything we can think of and more to address the problem of global warming, but we cannot scale up a global solution based on individual action. We have to make it too expensive to burn fossil fuels. That is not something that we can address through individual action.

        Cheers

        Mike

  14. Ending the world’s fossil fuel subsidies would reduce global CO2 emissions by 0.5 to 2.2 gigatonnes (Gt) per year by 2030, a new study says.

    The research, published by Nature, concludes that the removal of subsidies would lead to bigger emissions reductions in oil and gas exporting regions, such as Russia, Latin America and the Middle East, than promised by their Paris Agreement pledges.
    https://www.carbonbrief.org/new-study-questions-impact-ending-fossil-fuel-subsidies
    https://www.nature.com/articles/nature25467

    Hey, T! is there decent data out there for determining the efficacy and impact of individual action versus systemic changes like carbon taxes or ending fossil fuel subsidies? It would help blunt the hypocrisy attack to show that the solution largely exists in big system changes, not in buying more twist bulbs.

    Thanks

    Mike

    [Response: I wish I knew … but I don’t.]