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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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What has global warming done since 1998?

What the science says...

Select a level... Basic Intermediate

Every part of the Earth's climate system has continued warming since 1998, with 2015 shattering temperature records.

Climate Myth...

It hasn't warmed since 1998

For the years 1998-2005, temperature did not increase. This period coincides with society's continued pumping of more CO2 into the atmosphere. (Bob Carter)

At a glance

This date-specific talking-point is now something of a historical curiosity, but we'll leave it in the database for now because it's such a good illustration of the simplistic yet reckless mindset of the serial climate change misinformer. And indeed, we could (out of sheer mischief) revise this myth by replacing "1998" with "2016" - and in a few years time, by "2023" or "2024". In fact, that's what we are now starting to see in the climate change misinformation stream, © the Usual Suspects. 

Anyway, as first predicted over a century ago, Earth's surface, oceans and atmosphere are all heating up. That's due to our increasing greenhouse gas emissions, but over the years the warming has occurred at varying rates. This should in no way come as a surprise. Other physical phenomena periodically act either to suppress or enhance temperatures.

A prime example of such a phenomenon is the effects of La Nina and El Nino. This natural climatic oscillation features variations in winds and sea surface temperatures over the tropical eastern Pacific Ocean. The cycle can at times strongly influence temperature and rainfall patterns right around the world.

In a La Nina year, temperatures are suppressed, whereas an El Nino year sees them enhanced. This is noise on the long-term upward trend. That's why climatologists work with multiple decades, not just a few years in isolation, in order to get a grasp on what is going on.

The year 1998 featured a massive El Nino. The temperature spike it caused was a huge outlier, like a pinnacle towering over the landscape of the temperature record. In the following years there was a return to more typical conditions, with an erratic but upward warming pattern. That sequence of events gave deniers a brief opportunity to insist that global warming had “paused” or had even stopped.

You only need to remember one thing here. Those who create and spread misinformation about climate change don't care about reality. Public confusion is their aim. In this instance, the misinformation exercise involved deliberately selecting a limited block of years starting with the massive El Nino of 1998 and using that very warm starting-point to insist that global warming had stopped. They knew this would likely work for a few years and that the public would quickly forget why that was the case. Mother Nature had handed them a gift. It was an irresistible bunch of low-hanging fruit to exploit: little wonder the tactic is known as 'cherry-picking'. More recently, given that 2016 was the hottest on record, a similar opportunity has been spotted by some misinformers, although it’s not really caught on yet.

Talking about reality, what actually happened? Well, as of 2023, a couple of decades down the line, the top ten warmest years have all been since 2000, whatever observation-based dataset you choose, with eight of them being in the 2015-2022 period. 1998 is nowhere to be seen any more. By modern standards, it simply wasn't warm enough.

Please use this form to provide feedback about this new "At a glance" section, which was updated on May 27, 2023 to improve its readability. Read a more technical version below or dig deeper via the tabs above!

Further details

Even if we ignore long term trends (something deniers often do in order to make a point) and just look at the record-breakers, as of early 2023 the top ten warmest years have all been since 2000, whatever dataset you choose, with eight of them being in the 2015-2022 period. In this top ten grouping, 1998 is nowhere to be seen any more. It was not warm enough.

The myth of no warming since 1998 was largely based on the satellite record estimates of the temperature of the atmosphere.  However, as discussed in the video below by Peter Sinclair, even that argument is no longer accurate.  The satellites show warming since 1998 too.

There's also a tendency for some people just to concentrate on atmospheric or surface air temperatures when there are other, more useful, indicators that can give us a better idea how rapidly the world is warming. More than 90% of global warming heat goes into warming the oceans, while less than 3% goes into increasing the atmospheric and surface air temperature.  Records show that the Earth has been warming at a steady rate before and since 1998 and there is no sign of it slowing any time soon (Figure 1). 

Fig 1

Figure 1:  Global Energy Inventory: observed changes in the global energy inventory for 1971–2018 (shaded time series) with component contributions as indicated in the figure legend. Cross-Chapter Box 9.1 Figure 1 (part a) - From IPCC AR6 WGI Chapter 9.

Even if we focus exclusively on global surface temperatures, Cowtan & Way (2013) shows that when we account for temperatures across the entire globe (including the Arctic, which is the part of the planet warming fastest), the global surface warming trend for 1997–2015 is approximately 0.14°C per decade.

Ultimately, every part of the Earth's climate system is warming, and has continued warming since 1998.

Last updated on 27 May 2023 by John Mason. View Archives

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Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

Further reading

Tamino further explores the warming trend since 1998 in Garbage is Forever and Wiggles.

I've kept my original treatment of the subject as other websites hotlink to the images. My original treatment uses similar arguments to Fawcett and Jones 2008 although their analysis is much more rigorous (as you'd expect in a peer-reviewed paper).

Further viewing

Comments

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Comments 226 to 250 out of 414:

  1. Punksta @221: 1) NASA's Gistemp shows a warming trend of 0.087 C per decade over the last sixteen years; or 0.139 C per sixteen years. Deniers may want to call that "no warming" or a "halt in warming"; but that tells us only about their honesty. "The warming is not statistically significant" does not mean "there is no warming", anymore than "the pregnancy test was inconclusive" means "you are certainly not pregnant". 2) Contrary to your claim, the physics of the greenhouse effect do not predict that the atmosphere will be warmed first. Rather, they predict that the accumulation of energy at the Earth's surface (warming) will not stop until surface temperatures have risen sufficiently to restore radiative balance at the top of the atmosphere. Your silly claim that:
    "But since the basic mechanism of greenhouse warming is that the atmosphere warms due to CO2 trapping longwave radiation (leading to overall warming), this suggests the warming of the oceans *cannot* be a consequence of greenhouse warming (since the atmosphere is not warming)."
    only shows that you, like most so-called "skeptics", have not bothered to learn the theory before you declare it refuted. This urgency to declare a theory refuted despite not even understanding it shows that it is not scientific understanding that motivates the rejection of climate science.
  2. Tom, 1) Warming is not at all like pregnancy - statistical significance matters. At least to those whose agenda is true science. 2) The physics of greenhouse warming says that the CO2 traps heat. This necessarily means that the without heating of CO2, and hence of the atmosphere, there can be no knock-on warming elsewhere. Nothing you have said gainsays this. Indeed you yourself speak of a continuing warming of the surface.
  3. Punksta @ 227, you say "The physics of greenhouse warming says that the CO2 traps heat". Does it? I thought the theory said a molecule of CO2 captures an IR photon and either re-radiates the IR in a random direction, or excites an air molecule by collision. Nothing about 'trapping heat', per se, in that, is there? Of course, I don't have the advantage of your grasp of physics. I would be truly grateful if you could prove AGW theory wrong, as I am currently mildly alarmed by the evidence.
  4. Punksta @227: 1) Prattling on about your "agenda is true science" does not turn an indeterminate test ("the warming is not statistically significant") into a determinate falsification ("there has been a 16 year halt in warming"). Misinterpreting tests of statistical significance is not a mark of true science, but of propaganda, pure and simple. If you wanted to interpret the test accurately you would note that, not only does the test over 16 years of data not exclude zero warming; but it also does not exclude warming at greater than the IPCC predicted rate. The key question then is, if you expand the period under consideration until the trend is statistically significant, does it show warming or not. Want to take a bet on what it shows? Or will you chicken out and show that propaganda is your aim with your misrepresentations of science and scientific method? 2) I have written an introduction to the physics of greenhouse here. In a nutshell, the greenhouse effect works because atmospheric CO2 is cooler than the surface. As a result, when it absorbs surface radiation it is more likely to loose the energy gained through collision than remision, resulting in less power being emitted. This reduction in emitted radiation requires compensating increases elsewhere, which can only be achieved by the surface warming. So, contrary to your understanding, increased air temperature reduces the outgoing radiation at the Top of Atmosphere, thereby resulting in an imbalance. If an imbalance already exists, and the atmosphere does not warm, then the imbalance will not be reduced, with the consequence that more energy will be absorbed at the surface than if the atmosphere had warmed. Bizarrely, with your clear misunderstanding of the physics, you have got it exactly backwards.
  5. Doug H @ 228 ...Nothing about 'trapping heat', per se, in that, is there? Well, it is implied, and quite in agreement with what you said. The randomly directed re-radiated IR will only reach earth or space if there is a free path for it. Otherwise it will be absorbed by another CO2 molecule. And so on ... It's all about the 'mean free path' as I understand it.
  6. General comment It’s quite obvious that Punksta is talking in circular riddles, an art perfected by climate denier bloggers. He/she is jumping from one thread to another using the same silly red herrings. We can only hope this denier tires and goes away or the moderator enforces SkS’s site policy on this well recognised technique. I would like some questions answered properly though.
  7. Tom Curtis @ 229 1) Denying the 16-year warming hiatus is pure propaganda. the greenhouse effect works because atmospheric CO2 is cooler than the surface ... No, it works because of the absorption spectra of GHGs. However, you do correctly conclude (albeit for the wrong reasons), that the surface warms as a result. Which means that if the surface is *not* warming, then the greenhouse effect is *not* in evidence. increased air temperature reduces the outgoing radiation at the Top of Atmosphere Yes, a warmer atmosphere slows the cooling of the oceans into the atmosphere. But, again, if the atmosphere is not warming, it cannot be slowing the cooling of the oceans into itself. So if the oceans are indeed cooling, it must be something other than increased GHGs at work.
  8. Punksta wrote: "1) Warming is not at all like pregnancy - statistical significance matters." In that case, can you tell me exactly what it means for the observed trend to be not statistically significant? For example, does that mean that there has been a pause in global warming?
  9. In a rational conversation, the conversation progresses by people responding to the points that others have made. They do not simply yell more and more loudly the same slogan again and again. Punksta clearly is incapable of the former, and relies slowly on the frantic repetition of his slogan. Nothing is gained by conversation with a person that committed to irrationality. Consequently, I will simply note that: 1) Puncksta continues to insist that 0.14 C of trend warming over the last 16 years (gistemp) is no warming at all because it fails a test for statistical significance. He also no insists that noting that there has in fact been a warming trend over the last 16 years (even though all five major temperature indices show warming over the last 16 years) is propaganda. his world is so inverted that simply describing the situation accurately becomes, to his mind, propaganda. 2) He has clearly not bothered to read the introduction to the greenhouse effect that I linked to. Had he done so he would have seen that his objection to my description was in fact part of my description. Anybody confused by Punksta's bluster about absorption should think about what the effect of CO2 would be if the atmosphere was the same temperature as the surface, or warmer than it. In the later case, for example, adding greenhouse gases will cool the surface . I discuss this situation in a comment here (as does Chris Colose in the following comment).
  10. Punksta @232: (1) Trends 1996.92 to 2012.83 (ie, the most recent 16 years of data): Gistemp: 0.087 C per decade (0.139 trend increase in temperature over the 16 years). NCDC (NOAA): 0.047 C per decade (0.075 trend increase over the 16 years) HadCRUT4: 0.053 C per decade (0.085 trend increase over 16 years) UAH: 0.093 C per decade (0.149 C trend increase over 16 years) RSS: 0.003 C per decade (0.005 C trend increase over the 16 years). Of these, Gistemp is the most accurate in that it: a) Alone of the three surface temperature indices, has global coverage; b) Has more stations than NCDC, and significantly more stations than HadCRUT4; and c) It is a surface record, and is not contaminated by data from the stratosphere (which is cooling) as is the case with RSS and UAH. I note that a 0.03 C decadal trend taken over 16 years is a trend increase of 0.048 C, so even Punksta's cherry picked data set with its cherry picked period does not give a result of no warming, contrary to Puncksta's claims. It also leave grave doubts as to his maths, as he apparently thinks 16 years equals 10 years (to expect only a decades warming over the full 16 years); and that 0.048 = 0. Once again, there has been a warming trend on all data sets over the last 16 years. That trend has not been statistically significant on any data set. That just means that on all data sets, the error bars are wide enough so that they do not exclude underlying trends equal to zero, or indeed, equal to or greater than the IPCC predicted warming. Dressed up in its best form, Punksta's argument comes down to the inference: If we restrict our data to just the last 16 years, there is insufficient data to conclusively determine that the trend is not zero, or to determine that the trend does not equal the IPCC predicted trend. Therefore, the IPCC predicted trend has been falsified.
  11. (-sloganeering snipped-).
    Response: [DB] Please respond to Dikran's question above:
    "In that case, can you tell me exactly what it means for the observed trend to be not statistically significant?"
  12. Punksta, suppose that air temperatures went up for 30 days in the Spring, but then for the next 16 days there was no statistically significant warming. Meanwhile the oceans continued to warm slightly. Would you argue that this was conclusive proof that the cycle of the seasons was not causing the warming of the oceans or the previous warming air temperatures? This is a direct parallel to your argument 'against' global warming and ought to make clear why it is wrong. There was a study about a year ago that found the minimum period needed to establish a statistically significant trend in global temperatures was about 17 years. They could have saved the effort and noted that 'skeptics' so frequently use 'no warming for 15 / 16 years' to surmise that the boundary must be a year higher. Put another way... there hasn't been a statistically significant 'cooling' or 'flat' global temp anomaly trend since the 70s.
  13. Punksta seems to come from a long, long, long line of denialists who are ignorant (often deliberately so...) of the fact that a minimum amount of time is always required to be able to identify a signal emerging from inherently noisy data. I have two points, in addition to the many others made above, to put to this person. The first is an exercise in thinking (yes, I am being optimistic...): 1) If there had been no "statistically significant" warming for twelve years, does this disprove a relationship between CO2 and warming? If there had been no "statistically significant" warming for ten years, would this disprove a relationship between CO2 and warming? Five years? Two? What is the basis for claiming that there is no relationship between CO2 and planetary warming? 2) using the trend calculator to which many people have directed Punksta, I constructed a graph showing how many years prior to a particular year are required to identify a statistically significant warming trend at the 2 %sigma; (~95%) level. It's quick and dirty - I didn't muck around with the autocorrelation period and I only used GISTemp - but it's enough to demonstrate for any year in the last three decades how many years of prior data was required to observe a "statistically significant" warming trend. The graph itself shows two further things: 1) there is nothing unusual about the current period required to identify statistically significant warming - indeed, over all there is a trend to the period becomng shorter. 2) prior to 1981, the post-World War II hiatus (significantly attributable to aerosols) triples the period required to identify warming. However, there was warming occurring then too, but it was being compensated for by other factors. This did not alter the physics of greenhouse gases though, and the same is the case today - CO2 is still warming the planet. [I apologise for thumb-nailing the image. Try as I might, my efforts to use the width tag would not produce a visible graph.]
    Response: [DB] Improved image width. Bernard, I tried to email you the proper image width code but the message proved undeliverable.
  14. I should probably explain the approach that I used to determine the intervals I derived for the post above. All I did was enter various start years until I obtained for each of the end years a minimum-sized interval where there was no way to describe a negatively-sloped line through the whole range. It's not the best way to derive the info, but it was quick and it's a good approximation and I didn't want to waste time with something that has been debunked countless times in the past.
  15. Neat image Bernard!
  16. Punksta, even based purely (and therefore inappropriately) on statistics, the +0.14 C trend of the last 16 years is the most likely "true" value--the expected value. 0 is not the most likely value. Nor is +0.13, nor is +0.15. But trend values close to +0.14 are more likely to be the "true" value than trends far from it are. Statistical significance merely provides one estimate of the probabilities of those different trend values. Nor is there anything magical about the 95% confidence level; it is merely a traditional value. The 94% confidence level encompasses only values closer to the 0.14 most likely value. Statistics does not dictate what the confidence level should be. The situation outside of statistics dictates that. If you must make a decision based on your best estimate of the true value, you must weigh the costs and benefits of acting based on the several incorrect and correct decisions you might make based on that best estimate. You leaven those costs and benefits with the probabilities of the various errors and correct decisions. But even if you do make such a sophisticatedly thorough judgment, you are a fool if the statistics are the only knowledge you use to make your decision. Knowledge of physical processes such as causality, and a plethora of other factors, should be even more important in your decision. Statistics is merely one tool in a very large scientific toolbox. This failure of pure statistics to provide clear answers is not at all unique to climatology. I used to do massively complex ANOVAs in a completely different field, and usually had difficulty dissecting the complex relationships because the component, less complex statistical tests rarely were significant at the same probability level for them to logically support the overall, complex test. In other words, a naive perspective on the entire set of tests would be that they were internally inconsistent and therefore nonsensical and impossible. That's a similar phenomenon to what folks here have pointed out to you: Often all the short time intervals fail to reach significance at the same probability level as the longer time interval. That's why real scientists do not base their judgments solely on statistics, and even to the extent that they do rely on statistics, they do not rely on a naive, high school level of statistics.
  17. DB at #238. Thanks for the tweak. I'm not sure what the issue is with my addie - I tried mailing it from my institutional address, and there was no problem. I shall have to remain intrigued, and wondering... ;-)
  18. The link to Bob Carter's Telegraph article no longer works. It has moved to: There IS a problem with global warming... it stopped in 1998
  19. Simon @ 243, Bob Carter's Gish Gallop is still worth reading, as an example of faulty reasoning by someone who should know better. His opposition to AGW seems rooted in his politics, rather than in his superior understanding of the evidence. No doubt, this polarised view is being passed on to his students. Sad to see.

  20. Hi dikran

    where is  the global warming :)

  21. what is wrong with this graph

  22. Warren Hindmarsh, two questions:

    Did temperature rise or stand still over the course of the twentieth century?

    If the warming rate over a given period is greater than in a period over which temperatures are known to rise, is it correct to say that temperatures are not rising?

  23. sorry Dipal have to go right now

    The graph is from

    The Hadley Centre/CRU records show no warming for 18 years (v.3) or 19 years (v.4), and the RSS satellite dataset shows no warming for 23 years (h/t to Werner Brozek for determining these values). 

  24. A third question:

    Isn't it misleading to say that a period with a positive tempertature trend (ie, temperatures are rising) shows no warming?

     

    Please note that "no warming"  does not mean the same thing as "the warming is not statistically significant".

  25. Warren Hindmarsh wrote: "what is wrong with this graph"

    Read up on 'cherry picking'... that is, deliberately choosing a time period which shows the result you want despite the fact that longer and/or shorter time periods show results contradicting your claim.

    Also: "temps have been rising slowly since the middle ages"

    Not according to any historical temperature study I am aware of. Indeed, temperatures were slowly falling for thousands of years, including both before and after the 'middle ages', until the modern greenhouse warming surge.

    Finally: "but for the last 17yrs or so [temps] have stablized"

    Again, 'cherry picking'... not only of the time period, but also which temps. Ocean temps have certainly not 'stabilized' over the past 17 years.

    You obviously didn't even bother to read the post above. Maybe try that before making arguments which it has already disproved.

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