Trenberth: Global Warming Is Here To Stay, Whichever Way You Look At It

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"Trenberth: Global Warming Is Here To Stay, Whichever Way You Look At It"

While the overall warming is about 0.16°C per decade, there are three ten-year periods where there was a hiatus in warming, as the graph above shows, from 1977 to 1986, from 1987 to 1996, and from 2001 to 2012. But at each end of these periods there were big jumps. We find exactly the same sort of flat periods in climate model projections, lasting easily up to 15 years in length.

by Kevin Trenberth via The Conversation

Has global warming stalled? This question is increasingly being asked because the local weather seems cool and wet, or because the global mean temperature is not increasing at its earlier rate or the long-term rate expected from climate model projections.

The answer depends a lot on what one means by “global warming.” For some it is equated to the “global mean temperature.” That keeps going up but also has ups and downs from year to year. More on that shortly.

Why should it go up? Well, because the planet is warming as a result of human activities. With increasing carbon dioxide and other heat-trapping greenhouse gases in the atmosphere, there is an imbalance in energy flows in and out of the top of the atmosphere: the greenhouse gases increasingly trap more radiation and hence create warming. “Warming” really means heating, and this can exhibit itself in many ways.

Rising surface temperatures are just one manifestation. Melting Arctic sea ice is another. So is melting of glaciers and other land ice that contribute to rising sea levels. Increasing the water cycle and invigorating storms is yet another. But most (more than 90%) of the energy imbalance goes into the ocean, and several analyses have now shown this. But even there, how much warms the upper layers of the ocean, as opposed to how much penetrates deeper into the ocean where it may not have much immediate influence, is a key issue.

The ups and downs of global temperature

My colleagues and I have just published a new analysis showing that in the past decade about 30% of the heat has been dumped at levels below 700m, where most previous analyses stop.

The first point is that this is fairly new; it is not there throughout the record. The cause of the shift is a particular change in winds, especially in the Pacific Ocean where the subtropical trade winds have become noticeably stronger, changing ocean currents and providing a mechanism for heat to be carried down into the ocean. This is associated with weather patterns in the Pacific, which are in turn related to the La Niña phase of the El Niño phenomenon.

The second point is that we have found distinctive variations in global warming with El Niño. A mini global warming, in the sense of a global temperature increase, occurs in the latter stages of an El Niño event, as heat comes out of the ocean and warms the atmosphere. The ocean’s temperature is also affected by volcanic eruptions, which also affect the perceptions of global warming.

Normal weather also interferes by generating clouds that reflect the sunshine, and there are fluctuations in the global energy imbalance from month to month. But these average out over a year or so.

Another prominent source of natural variability in the Earth’s energy imbalance is changes in the sun itself, seen most clearly as the sunspot cycle. From 2005 to 2010 the sun went into a quiet phase and the warming energy imbalance is estimated to have dropped by about 10 to 15%.

Some of the penetration of heat into the depths of the ocean is reversible, as it comes back in the next El Niño. But a lot is not; instead it contributes to the overall warming of the deep ocean. This means less short-term warming at the surface, but at the expense of greater long-term warming, and faster sea level rise. So this has consequences.

Global warming is here to stay

Coming back to the global temperature record, one thing is clear. The past decade is by far the warmest on record. Human induced global warming really kicked in during the 1970s, and warming has been pretty steady since then….

Focusing on the wiggles and ignoring the bigger picture of unabated warming is foolhardy, but an approach promoted by climate change deniers. Global sea level keeps marching up at a rate of more than 30cm per century since 1992 (when global measurements via altimetry on satellites were made possible), and that is perhaps a better indicator that global warming continues unabated. Sea level rise comes from both the melting of land ice, thus adding more water to the ocean, plus the warming and thus expanding ocean itself.

Global warming is manifested in a number of ways, and there is a continuing radiative imbalance at the top of atmosphere. The current hiatus in surface warming is temporary, and global warming has not gone away.

–  Kevin Trenberth is Distinguished Senior Scientist at University Corporation for Atmospheric Research. Reposted with permission from the author.

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38 Responses to Trenberth: Global Warming Is Here To Stay, Whichever Way You Look At It

  1. Joan Savage says:

    Multi-factorate descriptions such as this are very welcome and much needed.
    I hope science journalists read it.

  2. Dave S. Nottear says:

    I know this is a gross over simplification, but if you stack that graph on top of these graphs :
    http://commons.wikimedia.org/wiki/File:Arctic_Sea_Ice_area_thickness_and_volume_trends.png

    It reminds me of what you see during the Phase Change on a plot of Temperature vs Heat/Energy: The Temperature increase “STALLS” as solid goes to liquid, or liquid to gas.

    If you show a good Time Lapse video of the Arctic over the past few decades, and line it up with the stack of graphs… The temperature stall might reflect the melting ice cube we call the Arctic?

    more poetic than scientific maybe, but what the hell

    • NotFunnyMitt says:

      This could be a very important point, I hope someone has some more input on it.

    • Jay Dee Are says:

      The cited Wikimedia graphs show sharp declines in Arctic sea-ice thickness, area, and volume after about 1997, the period for which denialists claim there has been no rise in average annual global surface temperature. However, Foster and Ramstorf have shown that, if one removes natural variability from the surface temperature record, the rise in surface temperature appears to be unabated. As shown by Trenberth and Church, among others, solar energy absorption by the planet, a better indicator of warming, has been unabated over the same period.

    • 99Problems says:

      Yeah I agree with Notfunny, the stall may reflect the phase transition, since matter in a certain state can only remain at certain temperatures, for example Ice < 0C, though once it melts the range widens again.

  3. I Hope the science community can help this situation.

    • Jay Dee Are says:

      I think more of the science community outside climatology needs to do its homework about climate and add its voice to the 97%. Some of the climate-related letters that I’ve seen in Physics Today and The Bent of Tau Beta Pi are disheartening because of the authors’ obvious lack of understanding of how climate works.

      • Mulga Mumblebrain says:

        They would just be typical Rightwingers, putting their ideology and indoctrination first, as ever. The climate destabilisation industry’s decision to paint this as a ‘Right versus Left’ ideological fight, rather than a problem of science, was a malignant master-stroke. The utter, vehement and vicious hatred of environmentalism on the Right these days has surpassed even their innumerable hatreds of other days in fury and intensity, and can be seen in the virulence of attacks by Rightist regimes, like that of Cameron in the UK and Harper in Canada, on not just environmentalism, but a truly morally insane assault on the web of life itself. Environmental destruction is reaching new fever pitches, driven on with a truly suicidal fervour, and the meagre gains of the last few decades are being ruthlessly annulled.

  4. Jim Baird says:

    Joe, the third element of sea level rise is the aquifers pumped dry trying to compensate for “Dust Bowlification”.

  5. Ken Barrows says:

    It would be interesting if both climate hawk and denier could agree on what data to examine.

    Would a denier say, if confronted, that only surface land temperature matters? What increase in surface temperature would be needed to change his mind?

    For the climate hawk (note: I am in full agreement), would s/he say that if Arctic ice starts to rebound magically then s/he would have to reevaluate conditions? How about if surface temperatures are stagnant at current levels through 2040?

    I know that it’s more complex and scientific conclusions are not subject to easy analysis. However, climate change is a political issue, and it seems useful to have an agreed upon basis for argument.

    • caroza says:

      It would be great, wouldn’t it? Unfortunately the only thing consistent about deniers and their arguments is that they have turbo-diesel goalposts.

    • Mulga Mumblebrain says:

      You cannot have arguments, discussions or exchanges of view with ideological fanatics. The denialists are not in any way interested in ‘truth’, ‘logic’, ‘consistency’ etc. They are only concerned with winning, by any means necessary.

      • Spot on, Mulga. It is important for people to remember this, to keep it right at the front of their consciousness when they try to deal with this issue.

        The true deniers are in denial — it’s a psychological state that has nothing to to with reason, fact or persuasion.

        However, there are some people who have open minds still, and it’s worth putting the information out there in various ways for them to take a look at it.

      • Camburn says:

        Mulga:
        That is why sanity must be part of the discussion. The folks who write about “potential” extremes without understanding the present normals have created a “Chicken Little” normal.

        Prof Trenbeth paper on OHC has to be taken in the context of what is known. His baseline is modeled under current conditions, not measurements. The error bars are large enough to state with 95% confidence that nothing has happened in regards to OHC.

        The hype has to stop, as it has become lies.

        • Mulga Mumblebrain says:

          Thanks-for proving my point.

          • Camburn says:

            Yep. It is really sad that so many writers of articles have no scientific education it seems. To not understand the topic at hand in a scientific perspective has created a large amount of doom and gloom forecasts that have not happened. So now, the public ignores it.

        • kermit says:

          What “present normals”? We have seen over 350 months in a row warmer than the twentieth century average. Every year since 2000 has been warmer than the 1990s average.

          Michigan has seen three 1000-year floods in eight years. The northwest passage has opened up. Tropical fish are moving north. And so, ad infinitum.

          Are you incapable of embarrassment? This is not a USA Today comment section; most of us are acquainted with the pertinent science. You cannot make the data go away by claiming this is not happening.

  6. Keith Oliver says:

    Maybe we haven’t seen the worse is yet to come or maybe because of the economic downturn that companies are resorting to natural gas instead of oil to run their factories.

    Winters are lasting a little longer in some places and summer is start earlier in others. Summers are lasting well into the time that winter should be setting in.

    Snow and rain is either coming down too much in some places where as too little or none at all in others.

    This cycle is repeating like a broken record and it is getting longer. While the skeptics that get paid by big corporations to deny that this is a natural cycle continue to lobby in congress and say that “Its okay, its not our fault”. All the while the population is getting bigger and there is not enough supply to meet the demand.

    But hey, go ahead and mess up the world some more because in the end, its the generations after we go that is going to suffer the most.

    “All this has happened before, it will happen again!”

    • BillD says:

      What the science says is that global warming will get worse for the next 5,000 to 10,000 years or more. Reducing greenhouse gases will slow the rate of climate change, but only extreme actions that are not likely with current technology can actually reverse climate change. So, economic downturns or shifts to natural gas only slow the rate of damage.

    • A good quote by Marx (Groucho)

      Why should I care about future generations? What have they ever done for me?

  7. Calamity Jean says:

    If this pause in warming ends with a big jump in temperature like 1998, it’s gonna get HOT! Like livestock dying of heat exhaustion hot. I’m hoping that will frighten the deniers into shutting up. The death toll among humans will be terrible, but that may be what it takes.

    • Merrelyn Emery says:

      We can cope with heat better than we can cope with starvation, thirst, wind speeds of 300kmp + and fire tornados, ME

    • Joan Savage says:

      Many a person has gone to his or her death either unrepentant or simply unconvinced. My favorite example of such a ditz is Lot’s wife.

      There’s nothing to gain in hoping for an El Niño of epic proportions.

      Anyway, El Niños require several conditions including a steady Pacific jet stream instead of one that flops around.

      To watch the Pacific jet stream flop over the past seven days, go to http://squall.sfsu.edu/crws/jetstream.html

      Select animated loop under Eastern Pacific & Western North America, and have it build a 7-day history.

      It’s fun, sort of.

      • BBHY says:

        “There’s nothing to gain in hoping for an El Niño of epic proportions.”

        Well, unless that is what it takes to pass a carbon tax. I think Washington DC hitting 110 degrees might make a difference in the political climate. But then I’m an optimist.

      • Merrelyn Emery says:

        Yep, stability is gone and with it have gone linear projections from historical records. All bets are off except you can put your shirt on more unpredictability, ME

  8. prokaryotes says:

    Find this very interesting

    James Hansen explains Climate Change and Free Market Solution
    http://climatestate.com/2013/05/23/james-hansen-explains-climate-change-and-solution/

    Though among a carbon fee he elaborates how Global Warming includes episodes especially in the northern hemisphere when “it gets colder, because of the ice melt”.

    • prokaryotes says:

      This phenomenon is estimated to kick in with 0.5-1 meter SLR – implications are grave because of the changed temperature gradient, which basically means more intense storms. Hansen done the studies on this actually before he wrote his famous book “Storms of my Grandchildren”.

    • Mulga Mumblebrain says:

      Once the ‘Free Market’ is involved the prime obsession will be profit, and all other conditions will become mere ‘externalities’.

  9. rollin says:

    “Has global warming stalled?” No, what has stalled is the ability to interpret data in a meaningful manner. I can choose ten year periods that show highly increased GW. The method shown in the graph is meaningless.
    What has also stalled is governmental support for studying global dimming factors.

    • Mulga Mumblebrain says:

      What never stalls is elite greed, and Rightwing ideological fanaticism. Indeed both are reaching real crescendos of extremity, as if maniacally pursuing their own destruction (and ours) with some sort of insatiable Death Wish.

  10. Merrelyn Emery says:

    It is the amount of energy going into the deepest oceans that seems the most ominous. The potential for disruption there is enormous and we don’t even appear to have adequate monitoring, ME

    • Rob Painting says:

      ME-just imagine what will happen when those easterly trade winds weaken as the climate moves back into a decadal period, or more, of El Nino-dominance. Suddenly much of that heat won’t be getting transported into the deep, it will remain in the surface ocean. Mass coral mortality, through bleaching, could rise dramatically.

      • Merrelyn Emery says:

        Yes IF we get any sort of stability back into the cycle but the future of the GBR looks grim in any case, ME

  11. Nice to see that our Kiwi Kevin is helping you guys out. He certainly knows his stuff.
    I keep coming across bit of his research in current New Zealand research.
    http://www.climateoutcome.kiwi.nz/precipitation.html

  12. Kevin and Joe,

    Thank you so much for this post. I’m hardly a climate scientist, but I’ve grasped everything this post says intuitively for several months now — since that bumpy period in 2012 when we had the western/midwest drought, Rocky Mountain forest fires, derecho, big Arctic ice meltdown, pan-Greenland surface melt and Hurricane Sandy in the span of a few months. Meanwhile the deniers were pointing to the slight slowdown in overall global surface temperatures as some kind of proof that the energy imbalance wasn’t an energy imbalance.

    By last December I was posting comments here, on Dot Earth and my own site to the effect that the energy imbalance was causing all kinds of stuff to happen — phase changes of ice to water and water to vapor; ocean warming (deep ocean warming wasn’t quite as well known yet); bigger storms; muscled-up high and low pressure systems; hot spells; droughts in the continental interiors; piles of snow; seasonal change-time anomalies and so on. Also, as ME says, (reply to Calamity Jane, #7), “…stability is gone and with it have gone linear projections from historical records.” In short, Global Weirding.

    However, I don’t have the background to make this argument scientifically. My version is based on a reading about conditions on the ground (and in the air and water) and my own Fourth Law of Thermodynamics, viz., A POSITIVE ENERGY IMBALANCE IN A COMPLEX SYSTEM INDUCES THAT SYSTEM TO BECOME IMBALANCED IN COMPLEX WAYS.

    Now I can make that argument, quote the good Dr. Trenberth, and link to this article. Thanks for the validation, guys. It’s critical to the ongoing fight to bring the truth to the public.

  13. Gingerbaker says:

    Heat is not temperature.

    Heat is what is accumulating on Earth due to the Greenhouse effect, and the imbalance of incoming vs outgoing radiation.

    Temperature is a reading on a thermometer due to the energetic vibrations of molecules.

    The idea that heat is not accumulating on Earth, because a particular set of thermometers is not registering a rise in local temperature is moronic. The laws of physics tell us heat MUST be accumulating, satellite energy readings tell us it IS accumulating.

    A claim that global warming has stopped is a claim that global heat accumulation has stopped. Such a claim requires an explanation for how the Laws of physics have been suspended.

    The proper reply to someone who has made the assertion that global warming has stalled or stopped is not to provide information. The proper reply is to ask them which supernatural entity do they credit with such an amazing display of magic.

    Helius, the God of the Sun? Hera, the Goddess of the air? Ra? Shu?

  14. James says:

    The sun is responsible for a lot — like sustaining life. But carbon pollution is the reason the planet is warming today. http://clmtr.lt/cb/sF20AU

  15. Cheng Chin Hsien says:

    I was wondering why the period of each cycle seems quite close to solar cycle (~11 yrs) and went to check the recent few round of solar cycles irradiance.
    Surprisingly, the year that the surface temperature shoots up coincidently occur together with the year of solar “minimum” (~1976, ~1987, ~1997). However, the most recent solar minimum ~ 2009, does not show significant increase in surface temperature.

    Will it be relevant to the weakening solar activity in last solar cycles (1997-2009)?

    I agree with the science of anthropogenic global warming. But I will still pray for suitably weakening solar irradiance to help us mitigate global warming…