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The 1C Milestone

Posted on 10 August 2015 by Rob Honeycutt

From Here to There and (Hopefully) Back Again

There’s long been a troubling disconnect in climate science communication where we discuss the temperature charts we see from all the surface station data sets and the importance of keeping global mean surface temperature below 2C. This creates a challenge for anyone who wants to understand where we currently are relative to a 2C rise in temperature over preindustrial times.

For the average person, who might just now becoming interested in the climate change issue, how are they to comprehend this? How can we make the communication of this critical data point more clear and concise? How do we make it more relevant to the issue of climate change?

Baselining and Anomalies

It’s important to understand that all the data sets are estimations of global mean temperature. We have multiple international groups all independently looking at the question of global temperature. Each have their own methods, and each have their strengths and limitations. And we also have hybrid estimates that attempt to combine different methods to improve on coverage and give a more accurate answer.

The surface temperature data sets (GISS, NOAA, HadCRUT4, Berkeley Earth and Cowtan & Way) are presented on different baselines and thus give us different relative temperature anomaly figures which are not specifically related to the 2C limit. For instance, HadCRUT4 baselines to 1961-1990, whereas GISS data baselines to 1951-1980. These baseline periods merely establish a zero axis for the data. Changing the baseline does not change the data, it only changes where the zero axis falls. (Tamino has a great explanation of this here.)

There is no perfect answer to the true global mean temperature of earth, but that’s rather inconsequential since we are primarily interested in understanding the change in global temperature. 

To make things even more confusing for the climate newby we have many tools out there that enable us to adjust the baseline we’re looking at. All the data sets publish their data relative to a set baseline, but for researchers it can be important to test differing baselines to reveal aspects of warming. For a newby it just makes things all the more confusing, and can easily play into the hands of people for whom confusion is a desired outcome.

The 2C Limit

The 2C limit has been established and agreed to as the point beyond which we do not know what consequences may occur in terms of earth systems feedbacks. In the words of the late Dr. Stephen Schneider, “We know that there are probably hundreds of tipping points. We don't know precisely where they are. Therefore you never know which ones you're crossing when. All you know is that as you add warming, you cross more and more of them. (link)" We know that the last interglacial period, the Eemian, peaked at a global mean temperature that was about 2C over the Holocene preindustrial temperature. Warming beyond that holds a great deal of uncertainty.

While the 2C limit is somewhat of an arbitrary figure, it’s still extremely important in terms of creating effective policy responses to the challenge of global warming. Dr. Stefan Rahmstorf explains it very well at Real Climate, where he states, "Climate policy needs a 'long-term global goal' (as the Cancun Agreements call it) against which the efforts can be measured to evaluate their adequacy.

People relate to and respond to simple round figures. If you’re a man trying to watch his weight, the morning you wake up to see the scale tip over 200 lbs is likely quite a shocking thing, regardless of whether it’s only half a pound over the previous morning. Clear round figures can have an enormous effect on us.

Setting goals and understanding where one is relative to those goals is also an important aspect of human motivation. It’s an important tool for achievement most eloquently exemplified in JFK’s words, “I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the earth.” Clear words, a clear goal. Remember, when those words were spoken, only 5 out of 10 US rocket launches had been successful, and the idea of putting a man into one of those must have seemed insane. But a mere 8 years later, in 1969, we watched Neil Armstrong set foot on the moon. Words and goals can be incredibly powerful.

Connecting the Dots

The disconnect is that all of our surface station data sets are expressing their anomalies as a figure off of differing mid-20th-century baselines, yet we’re also discussing a 2C limit that is a baseline over a preindustrial (1800's) average. New Scientist took up this question, with the help of SkS author Dr. Kevin Cowtan, for their article published last week, titled Halfway to Hell (figure below). Using 1850-1899 as a preindustrial baseline, we are this year just cresting the 1C mark over preindustrial temperature. So, in terms of a transient climate response, we are half way toward 2C.

But that’s just the transient response. That 1C has some momentum built into it. Based on the CO2 emission we’ve put into the atmosphere to date we are likely to see another 0.3C of warming within the next 30 years. In other words, almost regardless of what we do, we are already committed to 1.3C of warming by ~2050.

It would be impossible to shut down every fossil fuel source of energy in the next few weeks or months. We are going to continue emitting CO2 over the near term. The challenge is, how fast can we make this important transition to a carbon-free global economy in order to avoid the worst consequences? Glen Peters of CICERO does a very good job of explaining the challenge we face (h/t rustneversleeps). In his lecture titled A Journey from 5C to 2C, on the question of whether we can avoid the 2C limit, he says, “Yes, but only in the models.

Get used to it. We are nearly certain to tip the scales past the 2C limit, but that doesn’t mean all is lost. That doesn’t mean give up. It means we need to work hard today to get policies in place that can help drive what's required to aggressively address this critical issue. As Dr. Peters points out, on top of the action and innovation required to transition to zero emissions, within a few short decades we’re also going to require technology that does not exist today that will allow us to remove CO2 from the atmosphere. Gasser et al 2015 (Nature Communications 6; doi:10.1038/ncomms8958), also suggests we will need negative emissions in order to stay under 2C.

It bears noting that only the RCP2.6 emissions scenario gives us a reasonable chance of avoiding 2C, and that by a 66% likelihood. As of now, we are still on the RCP8.5 emissions pathway.

The challenge we face is made even greater by the fact that the solution requires a near complete shut down of an industry that, to borrow from Dylan Thomas, does not want to go gentle into that good night. Rather than Thomas viewing his aging father’s inevitable passing, the “rage” we face is a strapping, powerful industry of whom we must ask (or demand) to lay down and pass on for the good of humanity. We are standing in front of a Goliath of our own creation saying, “Thanks for all the fantastic energy, but you have to die now.”

In spite of the enormity of what we face, I am an eternal optimist. I believe in humanity. I believe in our ingenuity, our resilience, our capacity for creativity, and our abundant motivation to accomplish astoundingly insurmountable tasks.

Passing this 1C milestone is a strong wake up call we need to heed. Baselining the surface station data sets to preindustrial helps everyone understand where we are relative to the all important 2C limit. 

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Comments 1 to 19:

  1. Thanks for this, Rob, people are going to be referring to these clarifications in the future.  

    The other issue of course is that 2C is hardly a safe threshold, as you know. During the Emian sea level rise was enormous, and anything close to that level will flood the world's major cities. When Hansen's paper finishes being peer reviewed, let's hope it stimulates a discussion over working toward a new, safer baseline. Otherwise, if 2C spells disaster and hardship, that information needs to be communicated, and acted upon.

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  2. mike Roddy,

    I agree. It is important to always mention that an increase beyond 1.5 C was, and continues to be, a concern.

    A 2.0 C increase limit only came about recently when global leaders had to admit that success of resistance by those who do not care to reduce the benefit they can get away with had resulted in a lack of reduction of unacceptable activity by already fortunate people which made the 1.5 C limit virtually unachievable.

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  3. Good article and comments. However, I am much more realistic or pessimistic than Rob, unless only 50% of the human population dying due to climate change is optimism. Correct me if I am wrong, but I don't think most models take into account the certain to occur but unknown impact of the melting of the world's permafrost and methane clathrates. Also, I have read that a significant part of the impact of CO2 on warming occurs even after the first 85 years. 

    I follow many of the scientific global warming websites. The one thing that seems missing is personally responsibility for one's own emissions. The idea that one's own emissions don't really count seems pervasive or at least ignored. Sierra Club still extensively advertises Club trecks to Africa, Asia, and beyond. In contrast, Berners-Lee in his carbon footprint book on everything "How Bad Are Bananas?" guesstimates that for every 150 tons of emissions, one more human is likely to die. By that calculation, one pound of CO2 is equal to about one hour of human life. I actually think about that when deciding where to exercise, how often to go shopping, whether I should drive 100 miles to Pittsburgh to protest with, etc.

    I like Pope Francis and others emphasizing the immorality of destroying life through avoidable global warming emissions.  If the above is roughly correct, the average American is killing one person every ten years with his emissions. He is guilty of negligent manslaughter, even reckless manslaughter.

    Carbon dioxide molecules are like little bullets fired into the air. They don't kill anyone at first, but over decades they will kill huge numbers of humans as well as plant and animal life.  I think that we lead in part by example.  I personally hope to be carbon negative within the year by finally buying a low cost Nissan Leaf and installing at least 10,000 watts of solar panels so I can feed into the grid more energy than I use even including the embodied footprints of my vegan food, my home, and possessions, as well as my share of health care, government, and other societal functions.

    I would like to see scientific papers attempting to quantify the impact on human death. I have seen papers on animal extinction, on air pollution on human life, etc., but never on the long-term impact of global warming on global food production and starvation. Hansen once speculated that the Earth will only be able to support 1 billion humans. How many people will die with RCP 4.5? I fear 50%

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  4. TomR... Currently most researchers are saying permafrost and methane clathrates are not likely to be an issue. I'm definitely not on board with the near-term extinction folks like Guy McPherson.

    When this issue comes up I usually point people to a series of videos that Peter Sinclair produced called "The Methane Bomb Squad.

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  5. TomR: Permafrost emissions are not included in current climate models and other terrestrial biosphere feedbacks that are modelled may have optimistic assumptions. I wrote a piece on this recently. There's a link at the end to a more detailed SkS piece on the subject. A rough estimate is that our carbon budgets may be about 25% overestimated. 

    I do not believe, however, that a methane clathrate emergency is upon us. As part of the MOOC we ran a few months ago, I did a short video lecture on this.

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  6. @ One Planet Only Forever, this same logic applies to Bjorn Lomborgs attempt at trying to convince the world that fossil fuels should be allowed to warm our earth by 3C instead of 2C...

     Limits, or more succinctly "The slippery slope" styles of argumentation ,are coming whereby black is white and there is apparently no point doing anything.

     Resource bottlenecks are the first predicted consequence of panic. The trouble is the vested interests will argue this is good for employment yadda yadda yadda...

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  7. It is important to draw a distinction between methane emissions from permafrost and clathrates - they aren't the same thing.

    There are huge swathes of the Arctic where permafrost melt has started and methane emissions are rising. So far the impact of that s small but likely to increase. By how much?

    A study earlier this year looked at thawing permarost in controlled conditions over, if I recall, 12 years and measuring the gases produced. Their results suggest that by the second half of tis century emissions rom permafrost might be the equivalent of current US emssions. So even if we went to zero emssions, concentrations would keep climbing slowly from that source.

    So this is serious in terms of our ability to stabilise CO2 concentrations. But not the methane bomb some fear. More of a slow motion methane fizzer.

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  8. There and Back Again?

    To me, this sounds like you're saying our only hope of avoiding the 2C climate change limit is... Bilbo Baggins. :]

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  9. We know that at 400ppm, equilibrium sea level is 25m (75 ft) above current sea level, due to melting ice sheets.  I read that at 400ppm, in equilibrium the Alpine glaciers would still lose half their mass.  So, its not unreasonable to expect that at 400ppm, in equilibrium, the permafrost would vent half its carbon.  So, as there is a graph that indicates what equilibrium sea level pertains to what CO2 level, it would be useful to have a graph that indicates what equilibrium level of permafrost carbon vented pertains to what CO2 level.  With such information, the rest becomes a question for kinetics: how fast would this carbon be vented?

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  10. Yes, 2C is something of an arbitrary limit and I don't know why it's gained an almost mythical status; that under 2C is safe and over 2C is unsafe. The fact is that we are already seeing impacts from 1C. With more in the pipeline, it looks like we are already in the dangerous zone. James Hansen, et al (2013) suggest that 1C is the dangerous limit. This isn't a milestone, we're actually at the dangerous level now.

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  11. 2c is an agreed target: how else do you propose to get an agreed target for the whole world? Ever heard of groupthink?

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  12. New York needs moving within the next 100 years if Hansen is right abotu sea level rise, is anyone actually planning for it?

    300ppm, means ~1-1.5C above pre-industrial, the range we are going to be in once this 2015 large EL-Nino returns the heat, remember 2015 is the 1997 equivalent, 2016 will the 1998 one. And that means eventual sea level rise of 6-9m, as we aren't getting down to 300ppm anytime in the next several 1000's of years.

    Also note that these models claiming to give us a carbon budget, not only don't include permafrost CO2 and methane releases (the ones that do, keep CO2 above 400ppm even if all CO2 emissions stopped in 2010), also don't include forest fires, or the CO2 releases when the earth warms and several aspects that reduce the CO2 fertilization effect.

    And if you take 1.5C as safe, the budget is already blown.

    Remember that ~1W of forcing is being masked by SO2 and if fossil fuel use cease that also comes back into play, and studies looking just at that, with total CO2 emission stopping find temperature rises ~1.5-2C by 2050 anyway.

    RCP 2.6 = 420-450ppm CO2 by 2100 and then on-going.

    Not sure what the CO2e is, but at present that is ~460-470ppm.

    420-450ppm is Miocene warm period levels last seen 15 million years, ago, world 4-6C hotter, sea levels 30-40m higher.

    You tend to get ~60-80% of that warming in 100 years.

    Remember 300ppm means 6-9m sea level rise!

    It seems the arguments about a carbon budegt are more about pretendign we carry on emitting carbon until they invent techologies to take it out the air, rather than rationalising the sitaution.

    Wonder what all these hat waves this year are doing for the carbon emissions from the biopshere in these areas?

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    Moderator Response:

    [JH] Excessive white space removed.

  13. Most people who are knowledgeable about climate change I think are very aware that 2C in not a fixed point relative to where bad things start happening. It merely provides a point by which we can measure our progress. Think of it like a speed limit on the highway. You don't instantly crash and kill people if you go over the speed limit, nor if you drive just under the speed limit are you guaranteed to be completely safe.

    I specifically chose that Stephen Schneider quote because it demonstrates that tipping points are more of a continuum of accumulating problems. But I do think that the Eemian provides some relative measure. If we can hold temperature rise to 2C, then that is essentially the planet we are bequeathing to future generations.

    We will have made this transition from Holocene to Eemian-like Anthropocene as an incredibly abrupt shift relative to natural system, and that is going to impose a large shock on the natural systems that sustain us. There will be a lot of adaptation that has to take place just for 2C.

    When we start talking 3C, 4C or even 5C down the road... that's an entirely different ballgame. That's tantamount to getting out on the highway and trying to drive double the speed limit. 

    I would put it this way: "Safe" ≠ "benign."

    Below 2C is not benign. Below 1.5C is not benign. We have already imposed serious challenges on future generations with emissions to date. To me, the question is, how much human suffering of future generations can we avoid? 

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  14. @ 12 , 440 ppm is locked in and acknowledged by the solar thermal scientists of the world as impossible to not surpass... and that was years ago ! The reference actually questions whether it is possible to go over and then come back under the 440 ppm level and seems to say the science hasn't quite been worked out on that specific question... therefore making your specific question a more known , um, .... answerable entity?

     Specifically I refer to a statement by [edit] DR DAVID MILLS [edit] Dr. David Mills but cannot find the reference on the youtube at the moment which I (rewatched many times I can assure you) will post for your reference when I find it.

    A well defined problem is half answered: nice, specific question!!

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    Moderator Response:

    [RH] Please avoid use of all caps. Thx.

  15. Informative article Rob. Thanks.

     As climate scientists continue to focus their studies on rising carbon dioxide emissions, rising temperatures and the climate impacts that are and will result in from these increases, there appears to be very little discussion on the future energy needs of the planet. According to Seth B Darling and Douglas L Sisterson in their book "How to Change Minds About Our Changing Climate" the energy history of the planet in the last half-century is that in 1950 around 3 TW (terawatts) of energy was consumed globally. In 1990, this had increased to around 12 TW of energy that was consumed globally. Today we consume around 18 TW of energy globally. By 2050, the projected energy needs will increase to about 30 TW, nearly double todays. Considering that 83% of our energy currently comes from burning fossil fuels, just closing coal fired power stations and reducing forest clearing is not going to reduce emissions to the level that needs to happen to restrict temperature to a 2 degree rise. It's fairly clear that a complete technological change and a huge infrastructure building program in alternative sustainable power generation is required. It also indicates that fossil fuels will need to still be a part of the energy mix well into the future. This will need to happen unless the developed world wishes to condemn the developing world to a permanent state of poverty. The planet will need all forms of energy generation to meet that 30 TW figure. It will also need nuclear as well as solar, wind, thermal, and hydrogen. It does not need deniers and skeptics getting in the way of what needs to be done. This change in the energy mix needs to happen in a little over 35 years as the world's population rises to over 10 billion people.

    Aspirational aims, like those articulated for the Apollo program, are essential, but that aspiration needs to be translated into developing more efficient technology (power, transport, industrial and consumer) if we are realistically going to restrict the temperature rise to under 2 degrees. Unfortunately, I don't see that required technological transformation occurring at the rates that are needed. We have already wasted 25 years arguing wiith deniers since the whole global warming issue came to the forefront in the 1990s. We cannot afford to waste another 25 years if we are to have any chance. Not only do projected temperature rises and rising emissions need to be part of the limit to a 2 degree rise discussion, future energy requirements also need to be a part.

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  16. mancan18,

    An obvious answer to the challenge is the admission that what has currently been developed is a way of living that requires too much energy.

    Energy desires, particularly by the already highest energy users, clearly need to be denied no matter how profitable or popular meeting such desires may be.

    The simple truth is that many people who are perceived to be the most prosperous are also the biggest problem. Their perceived wealth is not sustainable. Their desires to increase their perceived prosperity in more consumptive ways clearly need to be discouraged, hence the lack of success in reducing global impacts.

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    Moderator Response:

    [JH] Excessive white space eliminated.

  17. OPOF @16... Actually, I believe that overconsumption is a different problem. Our core problem is that our main source of energy puts massive amounts of CO2 into the air. While the over exploitation of other resources is an important challenge, it pales in comparison.

    I would submit that the solution to both of these issues is to get the externalities of energy generation priced into the marketplace. If we can do that for energy, then doing the same later for resource depletion should be a piece of cake.

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  18. Rob Honeycutt@17, Changing what has to monetarily be evaluated in the marketplace will only partially address the problem. It is more important that the only actions allowed to be prioritized by profitability and popularity are actions that are almost certain to be truly sustainable. That also means curtailing any actions that are potentially harmful no matter how popular they may be among some people, leading that group to try to ensure the activity remains chap and profitable rather than admit the unacceptability of ways of living they got away with developing.

    Another thing that trying to price the impacts would fail to value or assign cosy to is the price that should be paid for any consumption of nonrenewable resources. How much it costs to extract and consume these limited resources should include a massive price no matter how abundant the resource appears to be.

    Even putting a price on consuming a nonrenewable may not properly limit pursuits of profit. The failure of the marketplace to properly value helium has led to the nonrenewable source being wasted on party balloons rather than be reserved for life saving medical use. And adding to the cost does not ensure that only the most deserving consumption would occur.

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  19. I would put it this way: "Safe" ≠ "benign."

    Yes, indeed, Rob. It also appears to be true that 2C is not necessarily safe; there is no science which says it is. Kevin Anderson has said this and James Hansen has said this.

    We may already be in unsafe territory at 1C (maybe 2C) with more already built in and, as ranyl pointed out, aerosols are masking some of the rise, so any decrease in burning fossil fuels (or maybe even a slowing of the increas), though necessary long term, could make matters worse over the medium term. To my mind, we're already in the non-benign range.

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