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« Phytoplankton love carbon dioxide | Main | More science with Guardian characteristics »

Observations are the darnedest things

One of the more iconic figures from the IPCC's Fifth Assessment Report was SPM10, which purports to show the relationship between cumulative carbon dioxide emissions and temperature.

These projections are produced by Earth System Models (ESMs), with input from the various carbon dioxide concentration forecasts (RCPs). On this basis the IPCC says that their best estimate of climate sensitivity to cumulative emissions is 2.4°C per gigatonne of carbon dioxide. However, as always seems to be the case with IPCC pronouncements, as soon as you start considering observations, these statements start to appear rather problematic.

In a post at Judy Curry's Nic Lewis notes that a recent paper that used climate model projections scaled to match observations to estimate the same value came up with a rather lower estimate of 0.7–2.0°C per GT. But even more intriguingly, he says that even this figure may be an overestimate. The carbon cycle is an area of huge uncertainty - readers no doubt recall the recent discoveries about the size of the climate effect of phytoplankton. Lewis explains that recent estimates of the amount of carbon dioxide sequestered on land have been substantially higher than earlier ones. And the question of how these carbon sinks will change in a warmer planet is even murkier. What certainly seems true is that the IPCC's existing ESMs don't consistently reproduce past changes in carbon dioxide concentrations, most overestimating it considerably. Their estimates of how much carbon is sequestered in various sinks also vary wildly. This makes their projections of future carbon dioxide concentrations at least highly debatable - some might even say "worthless".

With these uncertainties in mind, Nic has created his own simple ESM, with its key parameters constrained by observations. This means it has a climate sensitivity to carbon dioxide of 1.7°C per doubling and a TCR of 1.35. With these figures and with the carbon sinks constrained to recent observations too, he produces this figure, with the original IPCC results at the top, and with his own estimates below.

If he's right, then we should expect warming of only around 1°C per GT of carbon dioxide, not 2.4.

Observations are the darnedest things, aren't they?

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Reader Comments (30)

Still up.

Dec 1, 2015 at 9:19 AM | Unregistered CommenterAila

You can always pick your observations.
It's feelings that count (that's physics, that is).

And such observations as described here don't make climatologists feel important. So other observations can be provided.

Calling NOAA.

Dec 1, 2015 at 9:20 AM | Registered CommenterM Courtney

This makes the COP circus more likely as everyone knows the limit temp increases won't be reached so they can play knowing they'll win anyway, and be able to claim it as their legacy

Dec 1, 2015 at 9:23 AM | Registered Commenteromnologos

wait. Gigaton, or Teraton?

Dec 1, 2015 at 9:31 AM | Unregistered CommenterClimateOtter

'The carbon cycle is an area of huge uncertainty ' never has so much 'certainty, been built on the quick sand of that which is in reality poorly known. You can speculate that climate ‘sciences’ failure to evolve because of the very real fear that with added knowledge and decreased speculation, what is becomes actually ‘settled ‘ is not something that is ‘useful ‘ to ensure future careers, funding and political outlooks.

The bottom line may simply be that ‘problems’ offer opportunities that no ‘problems’ do not .

Dec 1, 2015 at 9:45 AM | Unregistered Commenterknr

Matt Ridley was allowed onto R4 Today this morning to give the low sensitivity message, but only in the graveyard slot just before the 9.00 am end, and was faced with the usual "but you're not a scientist" response.

Dec 1, 2015 at 9:59 AM | Unregistered CommenterMikky

knr +10

Please excuse a stab at draft 2:

'Never in the field of human polity was so much certainty drawn from so little theory by so many . . .'

Dec 1, 2015 at 10:00 AM | Unregistered CommenterOld Forge

The climate shows no signs at all of positive feedback for warming during interglacials. We are in an interglacial, therefore the feedback sensitivity will be a maximum of 1.2 (Hansen) or 0.6C (Herman Harde - using later HITRAN CO2 data)

Obviously Hansen's figure is used by IPCC as it is higher. So this suggests likely warming will be around 0.2-0.5C for a doubling of CO2. And for those still deluded by the "CO2 must done it" (from which they get figures like 1.7C) - it means everything we've seen was just natural (with perhaps a bit of CO2 warming - but far too small to make a significant difference).

Put simply the CO2 warming is too small to discriminate from natural variation within a century long period. In other words "Our children will never know what global warming is" (and we'll certainly never see it).

Dec 1, 2015 at 10:01 AM | Registered CommenterMikeHaseler

I get so exasperated with this stuff: a graph purporting to show that CO2 is THE temperature control knob in the IPCC admitted chaotic climate system. It's all just curve fitting nonsense.

Take a miniscule amount of geological time, use scant data that's been thrashed to an inch of its life, make some spurious adjustments where needed. Then squint a bit and ooh look there's a bit of correlation for a short period of hindcasting time.

It totally falls down when you expand the time period and even more importantly as soon as you start to make predictions/projections/extrapolations from your useless graph.

I also hate the way hindcasts (easy) and forecasts (hopelessly wrong) are just merged on the same graph with little delineation suggesting to a layman, "oh well they were nearly spot on". No, you've used a crowbar to curve fit the matching bit and lo and behold the resulting forecast is rubbish. Quelle surprise.

As usual, even then the most basic "correlation does not equal causation" doesn't get a look in. Virtually from the start of this boondoggle even the correlation part has dropped by the wayside but that hasn't stopped anybody one bit.

Meanwhile these trivial effects are being dwarfed by processes we haven't begun to understand (oceans, clouds etc).

And yet our leaders are all in Paris equating the threat from this non event with imminent World War 3.


Dec 1, 2015 at 10:24 AM | Registered CommenterSimonW

Observations, eh? Ok, let's take a look.

1. Satellites show no atmospheric warming for 18 years 9 months and nothing statistically significant for over 20 years. **That's NO warming in the very place AGW theory posits / demands / insists there should / must / will be atmospheric warming.**

2. During that 18-20 year period we're told humanity has put approximately 1/3rd of all the CO2 we ever have done into the atmosphere, yet it has had effectively zero impact on atmospheric temperatures.
**That should be AGW theory stone dead right there**

3. But it gets worse. If we really have put 1/3rd of all the CO2 we ever have done into the atmosphere over the last 20 years and if it really hasn't had any worthwhile impact on atmospheric temperatures, (the very place it should have the greatest impact) then it also follows that the other 2/3rds of CO2 that we've put there over the past 150-odd years has also had - wait for it - zero impact on atmospheric temperatures.
**That's the 'future warming is locked in due to the cumulative effects and half life of CO2' fox shot right there, too.**

So no atmospheric warming. No cumulative atmospheric warming. No weather extremes. (according to the IPCC) Seriously, based on actual observations...WHAT is there left of AGW theory?

Dec 1, 2015 at 11:03 AM | Unregistered CommenterCheshireRed

Re: Aila

> Still up.

Pulling an all-nighter?

Dec 1, 2015 at 11:19 AM | Unregistered CommenterTerryS

ClimateOtter ,
Yes indeed, the GtC units in my post should all read TtC : 1 teraton= 1000 gigatons

Dec 1, 2015 at 11:24 AM | Unregistered CommenterNic Lewis

The percent of each years aliquot of human emitted CO2 that becomes sequestered appears to be rising slightly. Is it any wonder that rising CO2 recruits additional sequestration mechanisms and/or accelerates present ones?

Dec 1, 2015 at 11:51 AM | Unregistered Commenterkim

As I'm fed up seeing stupid figures for climate sensitivity, I've written a: Global Warming for Dummies to explain in the simplest possible terms why these figures are just daft.

Dec 1, 2015 at 11:59 AM | Unregistered CommenterMikeHaseler

So when, if ever will the main stream take notice and/or endorse it? We'll take it as read that there will be many who will never accept it and/or fight it tooth and nail. What does the climate have to do to sway minds?

Me, I think that this year's El Nino and what happens in the next three years will be key. The warmists need a sharp and sustained uptick in temperatures after this much predicted super El Nino.

Dec 1, 2015 at 12:31 PM | Unregistered CommenterTinyCO2

Alia, it's way too early to stay up waiting for Santa. COP21 isn't going to make all your wished come true. Now go to bed like a good kiddie... or alternatively make some well thought out comments like an adult.

Dec 1, 2015 at 12:42 PM | Unregistered CommenterTinyCO2

@ Nic Lewis
I think ClimateOtter's point was that His Grace's final sentence should have read "If he's right, then we should expect warming of only around 1°C per GT teraton of carbon dioxide, not 2.4."

And yet, even that is a troubling value. CO2 warming is logarithmic. I don't doubt your superior expertise, but I'm definitely missing a point. Could you expand on it?

Equally, without the date values for your simplified ESM, I'm having difficulty appreciating its significance. I'm embarrassed to admit my ignorance, but I can't be the only person this ignorant. Any chance you could add them?

In an related issue, the top and bottom axes of the first graph have the same titles, but different values. I suspect the top title should read "Cumulative total antrhropogenic CO2 emissions from 1870 (GtCO2)
Alternatively, i'm missing a point again, and help from you, Nic or a reader will be appreciated.

Dec 1, 2015 at 1:28 PM | Unregistered Commenterleo Morgan

And those are upper bound estimates.

Dec 1, 2015 at 1:31 PM | Unregistered CommenterJamesG

MikeHaselar, has it precisely:

"stupid figures for climate sensitivity"

How can you estimate a nebulous presumption?

GIGO =Total bollocks.

Dec 1, 2015 at 2:43 PM | Unregistered CommenterAthelstan.

leo Morgan

Noted re ClimateOtter's point.

In CMIP5 models, a combination of emerging "warming in the pipeline" from past forcing, and an increasing airborne fraction of cumulative CO2 emissions - due mainly to a projected weakening of the lank carbon sink - approximately cancel with out the logarithmically-declining relationship of CO2 forcing with CO2 concentration. That leads to total warming being approximately a linear function of cumulative CO2 emissions - a constant TCRE.

In my model, these countervailing effects are substantially weaker, hence the greater downward curvature of the solid lines in my figure compared with the dashed CMIP5 models lines - my model's TCRE declines with total emissions.

It is not possible to add date values to the x-axis, as the relationship between date and cumulative emissions differs between RCP scenarios. But for each RCP projection line, each decade's mean value is shown by a dot, with squares for 2040-49 and diamonds for 2090-99. The dot where the coloured lines all start is for 2000-09 (for my model, it lies on the pink HadCRUT4 horizontal line).

The top and bottom axis titles in the SPM.10 graph are correct. The bottom one is in gigatons of carbon, the top one in gigatons of CO2.

Dec 1, 2015 at 2:44 PM | Unregistered CommenterNic Lewis

Thanks, Nic.

Dec 1, 2015 at 3:35 PM | Unregistered CommenterLeo Morgan

Even Hansen has published a paper admitting that the airborne fraction is decreasing, not increasing. "Remarkably, and we will argue importantly, the airborne fraction has declined since 2000 (figure 3)"

Dec 1, 2015 at 4:43 PM | Unregistered Commentermichael hart

you don't know because you re not a scientist..but there is something you have to know :
a scientist doesn't know better than you do!

Dec 1, 2015 at 5:10 PM | Unregistered Commenterlemiere

is nice to plot a wishful thinking graph, but what is the mechanism.

or in David Deutsch's words: what is the HARD TO VARY explanation?

Just like the Greek Gods WIZZARD CO2 makes it happen, and they have well a 100 myths to "explain"

Dec 1, 2015 at 5:42 PM | Unregistered CommenterVenusNotWarmerDueToCO2

Dec 1, 2015 at 11:03 AM | Unregistered CommenterCheshireRed

You are absolutely right,
"AGW theory stone dead right there", "CO2' fox shot right there, too". "So no atmospheric warming. No cumulative atmospheric warming. No weather extremes. (according to the IPCC) Seriously, based on actual observations...WHAT is there left of AGW theory?"
The presenting of our kind of logic/solution to fellow readers or to politicians brings no response because we do not understand that the climate debate is a whole new kind of debate which we have not yet accepted. In this new kind of debate conclusive evidence is not only ignored, it is positively discouraged. The debate is not a search for an answer but a search for more debate and they have been successful in finding no answer but finding more debate for decades.
The debate today has become simply a beauty competition between competing theories, these theories are admired or torn to shreds and if you don't like it then don't worry there will be another one along in a minute.
All the time this garbage passes for debate; the troughers get richer and the people get poorer.
The big problem is science of course and even the most intelligent and well qualified scientists and mathematicians seem to ignore simple facts and empirical evidence.
If empirical evidence provides you with an answer then the search should be over, but not for our scientists.

Dec 1, 2015 at 5:53 PM | Registered CommenterDung

SimonW at 10:24 AM has said everything that needs to be said about IPCC pseudoscience.

Dec 1, 2015 at 8:27 PM | Unregistered CommenterChristopher Hanley

Christopher Hanley
I'll endorse that comment.
The AGW hypothesis, and most especially its CO2 component, is falling apart at the seams. As TinyCO2 says, without a sustained major hike in temperature off the back of the current El Nino, the Climateers are going to end up looking singularly stupid within the next five years. If indeed they don't already.
Even the environmental activists are going to start slinking away or at the very least start yelling "Sustainability" because you can be sure that the eco-fascists and the hedge fund managers and the other parasites sucking on the public teat or definitely not going to go quietly into that outer darkness.
Let us, please, be ready for the next scam so we have a chance to shoot it down before it reaches cruising altitude!

Dec 1, 2015 at 9:16 PM | Registered CommenterMike Jackson

This plot belongs in the Guardian, right next to its staff's conversion between centigrade and fahrenheit. Cumulative emission (always positive) is an increasing function. Temperature is not.

Dec 1, 2015 at 11:30 PM | Unregistered CommenterIan

Somewhat off topic:-
I need help PLEASE!
I have NOT been paying attention of late and for the very first time in this blog have I seen Climate Sensitivity expressed in DEG/GT(co2).
To me it has always been deg/doubling of co2.
When and why has this changed? ( I did say I have not been paying attention!)
Thanks in anticipation.

Dec 2, 2015 at 7:31 AM | Unregistered CommenterRealOz

@ RealOz
I'd had exactly the same problem, plus more.
See my questions in the comment above, and Nic's reply which fully covers it.

Dec 2, 2015 at 10:24 AM | Unregistered CommenterLeo Morgan

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