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When did we start global warming? See the surprising answer (it’s not what you’ve been told).

18 October 2012

Summary: the world has been warming for two centuries. Only the past few decades of that trend results primarily from our emissions of CO2. It’s a fact well-established in the climate science literature, but hidden by the news media — since it weakens the narrative.

Contents

  1. Introduction: about the modern-era warming
  2. A few of the many references by climate scientists
  3. Update: predictions and explanations of the pause
  4. Other Posts in this series
  5. For More Information

(1)  Introduction: about the modern-era warming

It is a commonplace belief among laymen that the past two centuries of warming results from anthropogenic CO2 emissions. In fact the early warming constitutes a recovery from the Little Ice Age.

World CO2 emissions went ballistic after WWII, as shown in this DoE graph of estimated carbon emissions, and became a major driver of warming afterwards. That short period of anthropogenic-driven warming is why many scientists (eg, those cited in my post) discuss the statistical significance of the pause. This is clear in the climate literature, as seen in the studies below.

From the Department of Energy’s Carbon Dioxide Information Analysis Center

(2)  A few of the many references by climate scientists

(a) Working Group I: The Physical Science Basis, IPCC Fourth Assessment Report: Climate Change 2007

Executive Summary

.

Palaeoclimate model simulations are broadly consistent with the reconstructed NH temperatures over the past 1 kyr. The rise in surface temperatures since 1950 very likely cannot be reproduced without including anthropogenic greenhouse gases in the model forcings, and it is very unlikely that this warming was merely a recovery from a pre-20th century cold period.

Understanding and Attributing Climate Change

Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns (see Figure SPM.4 and Table SPM.2). {9.4, 9.5}

Update: from the draft of the Summary for Policymakers of the Fifth Assessment Report:

It is extremely likely [">95% probability"] that human activities have caused more than half of the observed increase in global average surface temperature since the 1950s.

(b)  The Australian Meteorological and Oceanographic Society Statement on Climate Change (undated)

It is highly likely that those human activities that have increased the concentration of greenhouse gases in the atmosphere have been largely responsible for the observed warming since 1950.

(c)  An interesting article mention things seldom mentioned by our news media, least they ruin the narrative: “Provoked scientists try to explain lag in global warming“, Paul Voosen, Greenwire (energy & environmental news), 25 October 2011

John Barnes, Principal Investigator at the Mauna Loa Observatory, NOAA:

“If you look at the last decade of global temperature, it’s not increasing,” Barnes said. “There’s a lot of scatter to it. But the [climate] models go up. And that has to be explained. Why didn’t we warm up?”

John Daniel, a researcher at the Earth System Research Lab of the NOAA:

“We make a mistake, anytime the temperature goes up, you imply this is due to global warming. If you make a big deal about every time it goes up, it seems like you should make a big deal about every time it goes down.”

Ben Santer, climate scientists at Lawrence Livermore National Laboratory:

“All of these things contribute to the relative muted warming. The difficultly is figuring out the relative contribution of these things. You can’t do that without systematic modeling and experimentation. I would hope someone will do that.”

(d)  When did Anthropogenic Climate Change Commence and what is its Potential Impact on Atmospheric Extremes?

By Greg Holland (Director, Earth System Laboratory) and Cindy Bruyere,
National Center for Atmospheric Research (NCAR), February 2012

From the Abstract:

A number of studies have assumed that anthropogenic climate change has occurred as a quasi-linear warming trend from around the turn of the 20th century and related this to potential changes in other parameters, such as weather systems and their extremes. However, we shall argue, using a comparison of Global Climate Model (GCM) simulations with and without anthropogenic forcing (following IPCC AR4) that the net anthropogenic forcing was indistinguishable from natural variability until the late 20th century. A sharp change to a marked quasi-linear warming began around 1960 and this warming became distinct from the annual variability by ~1975.

(e)  Climate Change: An Information Statement of the American Meteorological Society, 20 August 2012

There is unequivocal evidence that Earth’s lower atmosphere, ocean, and land surface are warming; sea level is rising; and snow cover, mountain glaciers, and Arctic sea ice are shrinking. The dominant cause of the warming since the 1950s is human activities. This scientific finding is based on a large and persuasive body of research.

(3)  Update: predictions and explanations of the pause

(a)  Advancing decadal-scale climate prediction in the North Atlantic sector“, N. S. Keenlyside et al, Nature, 1 May 2008 — Slides here to their 28 June 2008 presentation.  Abstract:

The climate of the North Atlantic region exhibits fluctuations on decadal timescales that have large societal consequences. Prominent examples include hurricane activity in the Atlantic, and surface-temperature and rainfall variations over North America, Europe and northern Africa. Although these multidecadal variations are potentially predictable if the current state of the ocean is known, the lack of subsurface ocean observations that constrain this state has been a limiting factor for realizing the full skill potential of such predictions.

Here we apply a simple approach — that uses only sea surface temperature (SST) observations — to partly overcome this difficulty and perform retrospective decadal predictions with a climate model. Skill is improved significantly relative to predictions made with incomplete knowledge of the ocean state, particularly in the North Atlantic and tropical Pacific oceans. Thus these results point towards the possibility of routine decadal climate predictions.

Using this method, and by considering both internal natural climate variations and projected future anthropogenic forcing, we make the following forecast: over the next decade, the current Atlantic meridional overturning circulation will weaken to its long-term mean; moreover, North Atlantic SST and European and North American surface temperatures will cool slightly, whereas tropical Pacific SST will remain almost unchanged. Our results suggest that global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming.

(b) Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming“, Susan Solomon et al, Science, 5 March 2010 — Abstract:

Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here we show that this acted to slow the rate of increase in global surface temperature over 2000–2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases.

More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% as compared to estimates neglecting this change. These findings show that stratospheric water vapor is an important driver of decadal global surface climate change.

Truth Will Make You Free

(4)  Some important things to know about global warming

While cheering for their faction of scientists, laypeople often lose sight of the big picture — the key elements for making public policy about this important issue.

(a)  The work of the IPCC and the major science institutes are the best guides for information about these issues.

(b)  The world has been warming during the past two centuries, in a succession of warming, cooling, and pauses. As for our influence:

“It is extremely likely (95 – 100% certain) that human activities caused more than half of the observed increase in global mean surface temperature from 1951 to 2010.”
— conclusion of the IPCC’s AR5 Working Group I

For research about the 1951 date see When did we start global warming? See the surprising answer., 18 October 2012

(c)  There is a debate about the attribution (causes) of past warming — which probably varied over time — between natural drivers (e.g., rebound from the Little Ice Age, solar influences) and anthropogenic drivers (eg, CO2, aerosols, land use changes). Other that that stated in (b), the IPCC’s reports make few claims about attribution of climate activity. This remains actively debated in the literature:  Scientists explore causes of the pause in warming, perhaps the most important research of the decade, 17 January 2014

(d)  Warming of the surface atmosphere paused sometime during 1998-2000:  Still good news: global temperatures remain stable, at least for now., 14 October 2012.

(e)  There is also debate about climate forecasts, both the extent of future CO2 emissions and the net effects of the various natural and anthropogenic drivers.

(f)  For the past five years my recommendations have been the same:

  1. More funding for climate sciences. Many key aspects (e.g., global temperature data collection and analysis) are grossly underfunded.
  2. Wider involvement of relevant experts in this debate. For example, geologists, statisticians and software engineers have been largely excluded — although their fields of knowledge are deeply involved.
  3. Start today a well-funded conversion to non-carbon-based energy sources by the second half of the 21st century; for both environmental and economic reasons (see these posts for details).

(g)  Posts about preparing for climate change:

(5)  For More Information

Posts about scientists discussing climate change:

  1. Richard Feynmann, one of the 20th centuries greatest scientists, talks to us about climate science, 12 February 2009
  2. Big news from NASA about the causes of climate change!, 6 June 2009 — About solar effects
  3. Breaking news: a new analysis blows more holes in the “hockey stick” temperature reconstruction, 15 August 2010
  4. What can climate scientists tell about the drivers of future warming?, 6 February 2012
  5. What can climate scientists tell us about the drivers of future warming? – part two of two, 10 February 2012
  6. The slow solar cycle is getting a lot of attention. What are its effect on us?, 11 February 2012
  7. A famous scientists makes a startling admission about Earth’s climate, 26 April 2012
  8. A look at the debate among climate scientists about global warming, 31 July 2012

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14 Comments leave one →
  1. OldSkeptic permalink
    20 October 2012 8:09 am

    Always got to be a bit careful about the ‘little ice age’. It was severe in the northern hemisphere, particularly north western Europe and North America. But, the evidence for a world wide cooling is mixed and very incomplete. Where is does exist there tends to be lack of correlation in time and severity.

    The temp records form elsewhere in the world is very incomplete (hence the work on using tree rings, et al et al to determine past temps). It could just have been a regional phenomena, perhaps Gulf Stream related, or a Jet stream shift (?). That may have then later caused some cooling elsewhere (as does the La Nina/El Nino cycles affect both hemispheres, despite being principally a southern hemisphere phenomena). Again, very uncertain at the moment.

    There is a lot of the old “looking under the light’ issue. That area had the highest tech (for the time), books, writers, newspapers. So it got a lot of press and writings about it. So we take a lot of notice about it. But did anything happen in the pacific regions? or the Equator, etc, etc. Very mixed data about that. And as for the very critical sea temps …. well?

    What we do know is that we have had strong regional climate movements for fair amounts of time. These can (sometimes) impact other regions or even have some global impacts.

    The reasons are poorly understood, mainly because of lack of data from the past. We don’t have direct ocean temp measurements and circulation patterns. Even small changes of those can have massive regional and even slight to moderate global impacts.

    My gut feeling (for what it is worth) is that the causes are not what most might come up with. We know (just from our personal experiences alone) that we can have individual extreme years (high or low). Now, to repeat just my gut feeling, is that the causes can ‘get stuck’. Say (purely as a thought experiment) a jet stream change, normal random variation can cause high or low temp atmosphere to be trapped for a year, so you get a very /hot/cold year.

    But say you can get longer shifts, the ‘trapping’ goes on for several years, even decades. Well then you can get positive feedback mechanisms coming into play that can extend that period and/or severity. Now normally it is regional, but if it goes on for long enough then it can ‘creep’ into other areas, which would never normally happen with just a few years affect.

    The other possibility is a Gulf Stream change. Very quick impact on the Atlantic areas, and if it goes on long enough then secondary impacts elsewhere later (‘creep’).

    That’s the trouble with complex (chaotic) systems … they are well … complex.

    • 20 October 2012 12:45 pm

      It’s always fascinating to see the extent to which believers in antropogenic climate change (or whatever they’re calling it this week) will go to avoid discussion of scientific research which contradict their beliefs. Here’s a clear challenge to a central plank of their belief system, and Oldskeptic attempts to cast dust in the air about a minor detail. And that’s what Oldskeptic does here, mostly by making stuff up.

      There is in fact quite a large body of evidence that the little ice age was global.

      Yes, the climate is complex, which is why we have climate science. It’s no different in this respect from other cutting-edge science. People like Oldskeptic invoke this complexity only when their beliefs are challenged by science.

      “My gut feeling (for what it is worth)”

      That’s one of the silliest things I’ve read in a long time. It would makes sense as a professional opinion from a climate scientist, but from a layman should be greeted only by laughter.

  2. Marc A. Cirigliano permalink
    22 October 2012 3:23 pm

    Some people like to ride horses no matter what. I think you’re on the wrong horse. I’d advise you to get off.

    There is both evidence and interpreting that evidence that contradicts what is asserted here at Fabius Maximus and the evidence used to support it: “Climate change: How do we know?“, NASA website.

    Your selection of evidence as “proof” does not bear scrutiny.

    For example, your use of John Barnes to assert that it has not warmed in the last decade is rebutted here as Skeptical Science, clarifies: “What has global warming done since 1998?“:

    “The planet has continued to accumulate heat since 1998 – global warming is still happening. Nevertheless, surface temperatures show much internal variability due to heat exchange between the ocean and atmosphere. 1998 was an unusually hot year due to a strong El Nino.”

    Moreover, on your main assertion that the science can’t explain what happened prior to WWII is wrong. The scientific correlation of the effect of CO2 on warming goes back at least 150 years. Again, Skeptical Science clarifies: “How do we know more CO2 is causing warming?

    “The amount of warming caused by the anthropogenic increase in atmospheric CO2 may be one of the most misunderstood subjects in climate science. Many people think the anthropogenic warming can’t be quantified, many others think it must be an insignificant amount. However, climate scientists have indeed quantified the anthropogenic contribution to global warming using empirical observations and fundamental physical equations.”

    As a primer on global temperature, it is affected by three main things:

    • The earth’s relation to the sun. As for that, we are currently in a cooling phase.
    • Volcanic eruptions, which periodically can cause a drop in global temperature.
    • The makeup of the atmosphere, with so-called greenhouse gases affecting the amount of earth-reflected infrared energy that is absorbed by the atmosphere. This is what we’ve been experiencing over the past 150 years.
    • 22 October 2012 6:23 pm

      Cirigiano,

      Thank you for more evidence of the anti-science “denialist” mindset that’s becoming so common in America. A purer example will be difficult to find.

      This post cites work of seven scientists and scientific institutions (including the IPCC), the latest in a series about this topic (post-WW2 anthropogenic warming) that cite dozens more. And your rebuttal is citing someone’s blog telling us what climate scientists believe (it’s run by John Cook, who explicitly says he is not a climate scientist). It would be funny if it was not so sad.

      “Moreover, on your main assertion that the science can’t explain what happened prior to WWII is wrong.”

      That’s a reading FAIL. It obviously not my “main assertion”, since I never say such a thing. Of course science can explain it.

      There is debate today among scientists about the relative weight of the various factors at work during that period, including natural cycles, volcanic activity, solar cycles, and human influences (eg, co2, aerosols). This is clear in the literature, some of which has been cited here during the past 5 years (see the FM Reference page Science & climate – studies & reports).

    • 23 October 2012 1:33 am

      I’m not the only one who’s noticed this: “Why Are Environmentalists Taking Anti-Science Positions?“, Fred Pearce, opinion article at environment360 (published by the Yale School of Foresty & Environmental Studies), 22 October 2012:

      On issues ranging from genetically modified crops to nuclear power, environmentalists are increasingly refusing to listen to scientific arguments that challenge standard green positions. This approach risks weakening the environmental movement and empowering climate contrarians.

    • 23 October 2012 1:13 pm

      A few more comments about Cirgliano’s comments:

      (1) “There is both evidence and interpreting that evidence that contradicts what is asserted here at Fabius Maximus and the evidence used to support it: “Climate change: How do we know?“, NASA website.”

      He waves at the NASA website, without telling us what specifically that contradicts here. The correct answer: nothing.

      (2) As for his list of the “three main things” affecting global temperature:

      (a) How is this relevant to this post? Also, I’ve mentioned these things hundreds of times. Quite strange that people come here and mention a few basic things about climate — assuming that this somehow disproves the statements of many climate scientists and institutions. Very weird.

      (b) It’s incomplete, because there things are complex. He mentions “greenhouse gases” but not aerosals — our emissions of which are also a large factor in climate change. And not just in the the atmosphere. The deposition of black dust in the arctic might be a significant factor in the accellerating melting of polar ice. And over longer periods of time there other factors (eg, arrangement of continents).

  3. 23 October 2012 4:19 am

    Update: predictions and explanations of the pause

    (a) Advancing decadal-scale climate prediction in the North Atlantic sector“, N. S. Keenlyside et al, Nature, 1 May 2008 — Slides here to their 28 June 2008 presentation. Abstract:

    The climate of the North Atlantic region exhibits fluctuations on decadal timescales that have large societal consequences. Prominent examples include hurricane activity in the Atlantic, and surface-temperature and rainfall variations over North America, Europe and northern Africa. Although these multidecadal variations are potentially predictable if the current state of the ocean is known, the lack of subsurface ocean observations that constrain this state has been a limiting factor for realizing the full skill potential of such predictions.

    Here we apply a simple approach — that uses only sea surface temperature (SST) observations — to partly overcome this difficulty and perform retrospective decadal predictions with a climate model. Skill is improved significantly relative to predictions made with incomplete knowledge of the ocean state, particularly in the North Atlantic and tropical Pacific oceans. Thus these results point towards the possibility of routine decadal climate predictions.

    Using this method, and by considering both internal natural climate variations and projected future anthropogenic forcing, we make the following forecast: over the next decade, the current Atlantic meridional overturning circulation will weaken to its long-term mean; moreover, North Atlantic SST and European and North American surface temperatures will cool slightly, whereas tropical Pacific SST will remain almost unchanged. Our results suggest that global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming.

    (b) Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming“, Susan Solomon et al, Science, 5 March 2010 — Abstract:

    Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here we show that this acted to slow the rate of increase in global surface temperature over 2000–2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases.

    More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% as compared to estimates neglecting this change. These findings show that stratospheric water vapor is an important driver of decadal global surface climate change.

  4. OldSkeptic permalink
    24 October 2012 9:51 am

    Data update , and no comment on what anyone has said here. The EL Nina shift has reversed itself.

    Now, being an Australian this dominates our Eastern climate. This also affects western South America. It also affects Mexico and the Southern central US climate. Basically when we have a drought, you have lots of rain. When we have floods you have droughts. Now we had 12 years of El Nina, droughts like you could not believe. Then La Nina, here floods like you could not believe .. you had droughts that you could not believe.

    Now we supposed that, based on all evidence that, we were going into an El Nina phase. And now we are not. As the Australian meteorologiists said this is ‘ unprecedented’ in all our history..

    Good for us, bad for the US. Heck we are the ‘lucky country’ after all. Maybe this is a a ‘reward’ for our carbon tax.

    • 24 October 2012 1:19 pm

      (1) “As the Australian meteorologiists said this is ‘unprecedented’ in all our history.”

      I would like to see the citation for that. It’s not my field, but I follow the ENSO cycle for business reasons — and have not seen such a description of recent activity. Certainly a simple look at the history shows nothing unusual in the magnitude or duration of recent ENSO cycles. As for Australia, the long-term proxy record shows it has had massive swings in weather — almost its defining characteristic. Much like the American southwest, but probably more so.

      From the weekly report ENSO Cycle: Recent Evolution, Current Status and Predictions.
      .

      NOAA, 22 October 2012

      .
      .
      (2) “The EL Nina shift has reversed itself.”

      That’s the current view, but NOAA expresses it as a tentative estimate.

      Here is the current forecast of model used by the US National Weather Service — their National Centers for Environmental Prediction (NCEP): the Coupled Forecast System model (the one in use now is version 2), as of 15 October 2012. It’s from their weekly report: ENSO Cycle: Recent Evolution, Current Status and Predictions.
      .

      As of 15 October 2012

    • 21 November 2012 4:00 am

      “Now we supposed that, based on all evidence that, we were going into an El Nina phase. And now we are not. As the Australian meteorologiists said this is ‘ unprecedented’ in all our history..”

      I would like to see a citation for that statement by “Australian meteorologists”. Looking at the long-term data at the NOAA website shows nothing unusual about activity during the past few years.

      Sidenote: they forecast the current ENSO-neutral conditions continuing for the next 6 – 9 months.

  5. OldSkeptic permalink
    24 October 2012 10:11 am

    “My gut feeling (for what it is worth)”.That’s one of the silliest things I’ve read in a long time. It would makes sense as a professional opinion from a climate scientist, but from a layman should be greeted only by laughter.

    Not fair, I have tried to separate data and my personal analysis and thoughts.

    That is uncalled for. And I expect an an apology.

    And in our long relationship, and it has been a very long time … I am trying to think where I ever said FM’s opinion should be treated by ‘laughter’. I might disagree or agree with you, but always with some dignity and respect (and I do respect you).

    That is so beneath you .. and cruel .. and unnecessary and …..

    • 24 October 2012 1:35 pm

      (1) It’s always interesting — and often surprising — what people find offensive. I’ve often surprised myself in that respect. This remark looks to me like a straightforward methodological point — one of epistemology. It’s directly relevant to yesterday’s post “Today’s debate: a passionate defense of credentialism.

      I sincereley believe we’d be better off as a society if we realized that democracy has its limits in fields other than government, and we’d be better off realizing our “guy feelings” have limits in technical matters. In the USA we’re having a small whooping cough epidemic, because parents refuse to have their children vaccinated — their gut feelings, you know. This belief that we can choose sides in scientific debates on “gut feel” has, IMO, turned the vital public policy process in climate sciences into a cacophony. We’ve had this debate before.

      Having got all that explanation out of the way, I apologize to OldSkeptic. I didn’t mean for that to be regarded as a hurful comment, let alone cruel. He’s made many extremely valuable contributions to the discussions here (among the best among the 25,000+ comments), over a long time, and his opinions deserve to be regarded with respect.

      (2) “I am trying to think where I ever said FM’s opinion should be treated by ‘laughter’.”

      That’s true. Unfortunately the evidence on the Smackdowns page shows that there were several episodes when you could have have done so — accurately. Next time you’re welcome to do so (sad to say, there will be a next time). I owe you one.

Trackbacks

  1. Climate scientists speak to us. What is their consensus opinion? | OMSJ
  2. How much did we warm in February? How much has the world warmed since 1979? | Fabius Maximus

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