ResearchBlogging.orgSee that black box over on the left-hand side of this blog? The one with the numbers counting down? That’s a little widget I assembled by rejigging one from trillionthtonne.org. The basic idea is that, if our climate can be expected to suffer severe disruption at a certain amount of global warming due to a certain amount of carbon emissions (since the beginning of the fossil-fuel era around 1850), then our best strategy should be to limit the cumulative carbon emissions to somewhere below that level, in this case 1 trillion tonnes of carbon.

But there’s plenty of uncertainty surrounding the estimate that a trillion tonnes of fossil-fuel emissions will lead to 2 °C of warming. What if the threshold is actually a lot lower? That, unfortunately, is the conclusion of a new paper in Geophysical Review Letters. Carbon emission limits required to satisfy future representative concentration pathways of greenhouse gases, by a team of Canadian climatologists led by Y.K. Arora of Environment Canada and the University of Victoria does not make for optimistic reading.

The results of this study suggest that limiting warming to roughly 2°C by the end of this century is unlikely since it requires an immediate ramp down of emissions followed by ongoing carbon sequestration in the second half of this century.

This is just one paper, but it’s an important one because it used an approach that will be incorporated in the next IPCC reports due out in a few years. The previous IPCC outlooks used 10-year-old simulation scenarios that were in bad need of an update. The author’s new computer runs are going to be hard to dismiss, because they do a good job of backcasting historical temperature increase. Their formulas say the Earth should have warmed by about 0.9 °C between 1850 and 2005, which is within the observed range of 0.76 ± 0.19.

The team looked at three scenarios involving low-, mid- and high-emissions. The latter two are too depressing to think about, so let’s just look at the low end, which calls for CO2 levels peaking at around 440 ppm (50 ppm above today’s levels) and then settling down at 420 ppm by the end of this century. They found that even such an ambitious target produces a warming of not 1.5 °C , not 2 °C, but 2.3 °C.

In terms of cumulative emissions, Arora et al. write that the trillionth tonne idea assumes that the cooling effects of aerosols and the warming effect of greenhouse gases other than CO2 cancel each other out, which they pretty much appear to do now. This makes the calculation easier, but it may not hold for much longer. The new paper’s simulations imply that the effects of the non-CO2 gases will overwhelm that of the aerosols in the coming decades, and so there will be much more warming for every tonne of emissions. Instead of having about half a trillion tonnes (500 Pg) left to emit before we kick in 2 °C of warming, we may have much less:

…our results suggest there is little room (∼160 ±80 Pg C) to limit the warming in 2100 to the 2.3°C associated with the RCP 2.6 concentration scenario.

Note that we’re emitting about 10 billion tonnes (10 Pg) of carbon annually now, meaning we have about 16 years left at the current rate, which assumes no one, not even China, builds any new coal plants at all. As for the old 2 °C target:

This implies that we have already surpassed the cumulative emission limit and so emissions must ramp down to zero immediately. The unprecedented reduction in fossil‐fuel emissions implied by either of these scenarios suggests that it is unlikely that
warming can be limited to the 2°C target agreed to in the 2009 Copenhagen Accord.

Curiously, soon after the advent of this paper was brought to my attention, I came across this missive from Mark Lynas, who has been following international climate negotiations underway in Bangkok. In it he bemoans the lack of interest in pursuing policies to keep global average warming to 1.5 °C. With the news that keeping things to even 2.3 may be unrealistic, let alone 2 degrees, I expect Lynas will be having a hard time elevating his chin.

Arora, V., Scinocca, J., Boer, G., Christian, J., Denman, K., Flato, G., Kharin, V., Lee, W., & Merryfield, W. (2011). Carbon emission limits required to satisfy future representative concentration pathways of greenhouse gases Geophysical Research Letters, 38 (5) DOI: 10.1029/2010GL046270

Comments

  1. Nice little toy. Everyone knows by now that oil is a naturally produced substance, we will never run out, and that global warming is a ploy. A manufactured emergecy designed to destroy capitalism. We all know how marxist fascim works – without your toys. Nice try though. Problem Solv

  2. Everyone knows by now that trees are a naturally produced commodity, we will never run out, and that deforestation is a ploy. A manufactured emergency designed to destroy the Giant Stone Head industry. Nice try, though.

  3. #3 Clam
    April 6, 2011

    #2 LOL
    #1 What’s marxist fascim (sic)? Are you so uneducated as not to know that Marxism was practised in the Communist Soviet Union and that Fascism is a right wing belief practised by Hitler, Mussolini and the GOP?

  4. #4 Chris O'Neill
    April 6, 2011

    The new paper’s simulations imply that the effects of the non-CO2 gases will overwhelm that of the aerosols in the coming decades, and so there will be much more warming for every tonne of emissions.

    This is the sting in the tail of carbon emissions – when they’re reduced, the short-term cooling effect of their associated aerosols is also reduced. So initially, reducing emissions all at once will increase the rate of warming.

  5. #5 Raskolnikov
    April 6, 2011

    In a way, I think global warming should be viewed as a welcome thing. If it cleans the Earth of all the idiots like PSCCP, even if it is at the cost of all the decent people, I don’t think I’ll mind that much. In fact, I won’t, I’ll be dead too! Yohoho!

  6. #6 Ender
    April 6, 2011

    PSCCP is real? Surely not? No one could be that… could they?

    PSEIR is real though. If he wasn’t, where did the powerful Easter Island Stone Head lobby come from then?

  7. #7 Ender
    April 6, 2011

    Shit. He is real. :(

    I went to his website. It’s just so… You kind of want to reach out and just give him a big hug – like when your daughter is afraid of the monsters in the cupboard – but then you read further and wonder if he’d think your comfort was a socialist plot by big pharma to get gays into his American Constitution.

    PSCCP: Don’t panic! The world is not that bad. Take it from one Christian to another. Jesus will not recognise the man you are today as the man He wants you to be. Let go of your fear, your hate, your anger, and let God’s love comfort you. He will protect.

  8. #8 kermit
    April 6, 2011

    PSCCP – And of course, as the droughts and floods and forest deaths and storms continue to get worse, and the food riots start (oops – they already started), and the gas in the US gets to $5.00, $6.00 per gallon… you’ll blame us.

    Raskolnikov – problem is, it will also wipe out the elephants, the whales, the other apes, the Amazon rain forest, the coral reef ecosystems. High price to pay to get rid of stupid(1) people. We know that conservative-authoritarian brains work a little differently than the rest of us. Can’t we, like, engineer a virus to attack certain genetic markers? Or have I said too much already?

    (1) That is, folks without a shred of decency, nor any concern for reality other than social constructs; with a complete lack of introspective self-assessment; and utterly devoid of curiosity.

  9. @ Kermit. We do blame you for high gas prices. Allow us to drill anywhere anytime for any oil out there and flood the market to bring down the prices.

    @Clam: You really have never read a history book have you? According to the Wolrd Book Encyclopedia the Soviet communists did acheive socialism in their country. There is not that much difference between the two. Germany and Russia hated each other anyway. Both communism and its derived form of economics – socialism, are evil and must be destroyed at all costs.

    Yes I am real. Yes I have a website. Yes I am a constitutional patriot who believes in the INDIVIDUAL, not the collective. Yes I believe socilaism and governmet run medicine is a bad thing. Yes I believe in real true freedom only brought about by the only person who can give rights to man – GOD! Yes I think we should return to old world values and traditions and destroy this marxist plot before it kills us all. So sue me. Wait. I don’t do fascist bloodsucking lawyers like the American Communist Lickers Union. Better luck next time. Enjoy your revolution while it lasts. One day When Jesus comes back your revolution will burn, He will rule the world, and we will rule with Him. Enjoy your temporary happiness in destruction and socialism. I know I will enjoy my permanent happiness knowing it will all burn one day. Enjoy your temporary revolution. I look forward to the day when it all becomes meaningless and is destroyed and not even recorded in the history books.

  10. #10 Problem Solving Creationist Capitalist Patriot
    April 6, 2011

    @ kermit

    So, you are one of those marxist Bill Ayers population control mass genocide terrorists? Go ahead and make your virus. Hope you have fire insurance. You’ll need it in hell.

  11. @ ender

    You cannot be christian and socialist at the same time.

    You cannot be christian and gay at the same time.

    That’s like Che being a rich capitalist.

  12. #12 Lyle
    April 7, 2011

    If its to late then lets follow: ecclesiastes viii. 15 (AV) Then I commended mirth, because a man hath no better thing under the sun, than to eat, and to drink, and to be merry

    Stop worrying then and enjoy what time you have left, following: isaiah xxii. 13 (AV) Let us eat and drink; for to morrow we shall die.

    If we can’t affect something then don’t worry about it, for in the long run as was said we are all dead anyway.

  13. #13 Ender
    April 7, 2011

    @PSCCP – then it’s lucky I’m neither a socialist nor gay.

    Relax. Let Jesus’ love be the balm to calm your fears. Do not fret, our survival is guaranteed – though some of us may wish it were not when they see the judgement of the Lord – but unless you cease this foolish a-historical a-theological path you are travelling down then Satan will take you for one of his own. Abandon your foolish materialism and renounce Mammon and your capitalist fervour. Did the Lord not say – that which you do for the least of my brother you do for Me?

  14. #14 Problem Solving Creationist Capitalist Patriot
    April 7, 2011

    I will not renounce God’s blessings of capitalism.

    Capitalism rewards success. Socialism punishes success. Did God not reward people and make them wealthy before? Remember the megatons of gold that Solomon was blessed with? Remember how Abraham was blessed and was wealthy?

    Satan invented socialism and its tyranical overlords who oversee all transactions.

    I realize what the bible says about THE LOVE OF money being the root of all evil. It also says THOU SHALT NOT STEAL which is what socialism is guilty of. Government does not have the authority to confiscate God’s blessing on any man.

    Renounce your satanic following to karl marx. Abandon your desire to steal from people and redistribute it as the tyrants in government see fit.

    Charity is encouraged, socialism is to be destroyed. Only through capitalism can charity occur in the first place. Charity is what Jesus taught – individual sovereign people giving freely of their own will to another independent sovereign individual. What you think Jesus taught is Jesus telling ceasar to kill the rich, steal their belongings, and then redistribute them only to those who bow at the altar of the government who distributes other people’s stuff. That is socialism. It always ends up with a tyrant overlord in charge and usually ends up in bloody war. As it should. Treason against the human race is punishable.

    Socialism has never worked anywhere it has been tried. Sooner or later it always fails. You cannot tax people into poverty and then expect to keep things running. The money is not made in a magic pot. It doesn;t just spring up from the ground. You do not know how reality works.

    You also have a twisted view of scripture. Seek help. Read it as it is written, not how karl marx thought it should read.

  15. #15 elkern
    April 8, 2011

    Wow, isn’t there a “law” (like Godwin’s) about people who are so far out-there that you can’t tell whether they are making it up (for fun, profit, or political points)?

    For a good time, check out:

    http://www.geocentricity.com/

  16. #16 Wayne Williamson
    April 8, 2011

    thanks for the article…to the trolls I have to say…why oh why would you even read such gloom and doom stuff when your religion already has it built in….

  17. #17 Gar Lipow
    April 15, 2011

    @elkern There is such a law. It is called “Poe’s law”. Google can yield more information.

  18. #18 Wow
    April 18, 2011

    ALthough poe’s law isn’t about people yanking chains by pretending to be extreme/mad/insane but that no matter how extreme/mad/insane your parody is, SOMEONE on the planet believes something as or more mad than that.

    It’s often misrepresented as a “I was only joking”.

  19. #19 Steve Bloom
    April 18, 2011

    James, I assume you must have blogged this at some point, but just to note that Jim Hansen thinks +2C is a recipe for disaster since among other effects it’s enough to push the ice sheets over the edge. Frankly, looking at the scale and pace of polar climate change so far, I’m finding it harder and harder to think we haven’t already done so.

  20. #20 elkern
    April 20, 2011

    Gar & Wow -

    Thanks for filling in that blank spot in my memory. PSCCP’s reference (above, #14) about “God’s blessings of capitalism” triggered my question, though it may be more like an example of “Poe’s Correlary”.

    Googling “Poe’s Law” also got me to the Conservipedia page – which describes it (Poe’s Law) as some kind of liberal conspiracy, and gallops right to “proof” that evolution is wrong.

    I only wish they were joking – because that would be a pretty good one.