## Monckton Myth #3: Linear Warming

#### Posted on 18 January 2011 by dana1981

In his recent response to Steketee's article in *The Australian*, Monckton's argument #5 reads as follows:

In the 40 years since 1970, global temperatures have risen at a linear rate equivalent to around 1.3 °C/century. CO2 concentration is rising in a straight line at just 2 ppmv/year at present and, even if it were to accelerate to an exponential rate of increase, the corresponding temperature increase would be expected to rise merely in a straight line. On any view, 1.3 °C of further “global warming” this century would be harmless. The IPCC is predicting 3.4 °C, but since the turn of the millennium on 1 January 2001 global temperature has risen (taking the average of the two satellite datasets) at a rate equivalent to just 0.6 °C/century, rather less than the warming rate of the entire 20th century. In these numbers, there is nothing whatever to worry about – except the tendency of some journalists to conceal them.

This paragraph contains a number of erroneous statements. Firstly, according to both GISTEMP and HADCRUT3 (satellite data only began in 1979), the global temperature trend since 1970 is 1.6–1.7°C per century. Secondly, the atmospheric CO_{2} concentration has been accelerating (not linear). The rate of increase in atmospheric CO_{2} in the 2000's (2.2 parts per million by volume [ppmv] per year) was in fact 47% faster than the rate of increase in the 1990s (1.5 ppmv per year). Monckton uses these incorrect assertions to create the support for his incorrect argument - that if we continue with business-as-usual, global temperatures over the next century will increase at a constant, linear rate (or slower).

### Temperature Response to CO_{2}

Monckton claims that an exponential increase in atmospheric CO_{2} concentration would result in a linear increase in global temperature. But of course that depends on what the exponent is in the exponential increase. Monckton is referring to the logarithmic relationship between radiative forcing (which is directly proportional to the change in surface temperature at equilibrium) and the atmospheric CO_{2} increase. Note that we are not currently at equilibrium as there is a planetary energy imbalance, and thus further warming 'in the pipeline' from the carbon we've already emitted. Therefore, estimates of the rate of warming due to CO_{2} thus far will will be **under**estimates, unless accounting for this 'warming in the pipeline' (which Monckton does not).

This logarithmic relationship means that each doubling of atmospheric CO_{2} will cause the same amount of warming at the Earth's surface. Thus if it takes as long to increase atmospheric CO_{2} from 560 to 1120 ppmv as it did to rise from 280 to 560 ppmv, for example, then the associated warming at the Earth's surface will be roughly linear. So the question then becomes, how fast do we expect atmospheric CO_{2} to rise over the next century?

### How Fast will Atmospheric CO_{2} Rise?

The IPCC addressed this question by examining a number of different anthropogenic emissions scenarios. Scenario A1F1 assumes high global economic growth and continued heavy reliance on fossil fuels for the remainder of the century. Scenario B1 assumes a major move away from fossil fuels toward alternative and renewable energy as the century progresses. Scenario A2 is a middling scenario, with less even economic growth and some adoption of alternative and renewable energy sources as the century unfolds. The projected atmospheric CO_{2} levels for these scenarios is shown in Figure 1.

*Figure 1: Atmospheric CO _{2} concentrations as observed at Mauna Loa from 1958 to 2008 (black dashed line) and projected under the 6 IPCC emission scenarios (solid coloured lines). (*

*IPCC Data Distribution Centre*

*)*

In short, following the 'business as usual' approach which Monckton argues for, without major steps to move away from fossil fuels and limit greenhouse gas emissions, we will likely reach 850 to 950 ppmv of atmospheric CO_{2} by the year 2100. It will have taken approximately 200 years (from 1850 to 2050) for the first doubling of atmospheric CO_{2} from 280 to 560 ppmv, but it will only take another 70 years or so to double the levels again to 1120 ppmv. This will result in an accelerating rate of global warming, not a linear rate. Under Scenarios A2 and A1F1, the IPCC report projects that the global temperature in 2095 will be 2.0–6.4°C above 1990 levels (2.6-7.0°C above pre-industrial), with a best estimate of 3.4 and 4.0°C warmer (4.0 and 4.6°C above pre-industrial average surface temperatures), respectively.

*Figure 2: Global surface temperature projections for IPCC Scenarios. Shading denotes the ±1 standard deviation range of individual model annual averages. The orange line is constant CO2 concentrations at year 2000 values. The grey bars at right indicate the best estimate (solid line within each bar) and the likely range. (Source: **IPCC**).*

### Life in the Fast Lane

Monckton claims that these projected amounts of warming have not been borne out in the surface temperature changes over the past decade. But there are many factors which impact short-term global temperatures, which may conceal the long-term warming caused by increasing atmospheric CO_{2}. So if we want to know if the IPCC projections are realistic, rather than examining noisy short-term temperature data, we should examine how much atmospheric CO_{2} is increasing.

When we look at this data, we find that observed CO_{2} emissions in recent years have actually been tracking close to or above the worst case (A1F1) scenario.

*Figure 3: Observed global CO2 emissions from fossil fuel burning and cement production compared with IPCC emissions scenarios. The coloured area covers all scenarios used to project climate change by the IPCC (**Copenhagen Diagnosis**).*

### What Lies Ahead

So if we continue in a business-as-usual scenario, we should expect to see atmospheric CO_{2} levels accelerate rapidly enough to more than offset the logarithmic relationship with temperature, and cause the surface temperature warming to accelerate as well. Monckton's claim of a "straight line" increase in global temperature ignores that in his preferred 'business as usual' scenario, we are currently on pace to double the current atmospheric CO_{2} concentration (390 to 780 ppmv) within the next 60 to 80 years, and we have not yet even come close to doubling the pre-industrial concentration (280 ppmv) in the past 150 years. Thus the exponential increase in CO_{2} will outpace its logarithmic relationship with surface temperature, causing global warming to accelerate unless we take serious steps to reduce greenhouse gas emissions. In fact, to continue the current rate of warming over the 21st Century, we would need to achieve IPCC scenario B1 - a major move away from fossil fuels toward alternative and renewable energy.

As for what amount of global warming is "harmless" and "dangerous" we will examine this question later on in another upcoming Monckton Myth.

MattJat 08:16 AM on 18 January, 2011dana1981at 08:22 AM on 18 January, 2011littlerobbergirlat 08:56 AM on 18 January, 2011Ron Crouchat 10:34 AM on 18 January, 2011WheelsOCat 10:41 AM on 18 January, 2011dana1981at 10:57 AM on 18 January, 2011Philippe Chantreauat 11:24 AM on 18 January, 2011NETDRat 12:58 PM on 18 January, 2011dana1981at 14:16 PM on 18 January, 2011dana1981at 14:20 PM on 18 January, 2011NETDRat 14:23 PM on 18 January, 2011Moderator Response:[Daniel Bailey] Read the Tamino post located at the link dana1981 provided you with. You'll find your answer there.NETDRat 15:02 PM on 18 January, 2011Moderator Response:[Daniel Bailey] If you want us to take you seriously you'll have to do better than that. Tamino is a professional time-series analyst who has proven his worth in the climate blogging wars over the years. Dismissive handwaving of his work costs you dearly in the credibility department here. A proper way forward would be for you to publish your work in a peer-reviewed body, as Tamino has done in the past. And in the spirit of teaching the teacher, you could post your claims at Tamino's place,Open Mind.dana1981at 15:35 PM on 18 January, 2011Chemwareat 17:08 PM on 18 January, 2011Ian Loveat 19:46 PM on 18 January, 2011barryat 20:20 PM on 18 January, 2011Alexandreat 21:26 PM on 18 January, 2011Chemwareat 21:32 PM on 18 January, 2011_{2}] is a function of economic activity and CO_{2}sequestration mechanisms. Economic + physical chemistry modeling, anyone ? I'm not at work right right now, but I'll have another play tomorrow with TC2D - I'm intrigued to see which simple equations best describe the data.Dikran Marsupialat 23:51 PM on 18 January, 2011MarkRat 00:06 AM on 19 January, 2011MarkRat 00:20 AM on 19 January, 2011NETDRat 01:51 AM on 19 January, 2011apsmithat 02:20 AM on 19 January, 2011Dikran Marsupialat 02:43 AM on 19 January, 2011Albatrossat 03:29 AM on 19 January, 2011"CO2 concentration isThat first claim has been shown to be demonstrably false. The second claim is a "what if", but in the real world the appropriate mathematical and statistical treatment of the data (and appropriate nomenclature, as noted by Dikram @24) show that the we are already there. This really is a no brainer and it is disturbing that people are willing to go out on a limb and shred their own credibility by trying to defend Monckton's fallacies.rising in a straight lineat just 2 ppmv/year at present and, even if itwere to accelerate to an exponential rate of increase, the corresponding temperature increase would be expected to rise merely in a straight line."NETDRat 03:32 AM on 19 January, 2011dana1981at 04:12 AM on 19 January, 2011WheelsOCat 05:07 AM on 19 January, 2011Dikran Marsupialat 05:18 AM on 19 January, 2011Riccardoat 05:40 AM on 19 January, 2011BKseaat 07:18 AM on 19 January, 2011archiesteelat 08:34 AM on 19 January, 2011Chemwareat 10:50 AM on 19 January, 2011_{2}] - which this comparison confirms. I would suggest you have a play with TC2D: it is quite surprising how well a quadratic fits the data, especially given the limited degrees of freedom of a quadratic.MarkRat 11:24 AM on 19 January, 2011muoncounterat 12:45 PM on 19 January, 2011Dikran Marsupialat 21:06 PM on 19 January, 2011NETDRat 01:02 AM on 20 January, 2011Moderator Response:[Daniel Bailey] Sure looks like a Thelma & Louise to me: Yup, no problem.NETDRat 02:30 AM on 20 January, 2011Moderator Response:[Daniel Bailey]"Apparently CO2 has very little effect.Incorrect; seehere. To address the rest of your misconceptions, use the search function in the upper left corner to find many posts addressing those issues.dana1981at 03:28 AM on 20 January, 2011dana1981at 03:30 AM on 20 January, 2011NETDRat 03:45 AM on 20 January, 2011jhudsyat 04:15 AM on 20 January, 2011Dikran Marsupialat 05:15 AM on 20 January, 2011NETDRat 06:45 AM on 20 January, 2011Albatrossat 07:06 AM on 20 January, 2011"The warming in the pipeline argument is probably not true since the heat which is supposedly building up in the ocean isn't building up at all."Again, you need to back this up with some actual facts (and not some half-baked paper published in a dodgy journal by Knox and Douglass). For now, you have simply made an unsubstantiated assertion."See the "missing heat" argument which Trenberth seems to be losing."Trenberth has not "lost" the heat. Just because one cannot find something because of incomplete data sampling, doesn't mean that it is not there. Maybe it is time to resurrect "DSCOVR (Deep Space Climate Observatory) that George Bush Jnr. scrapped."Even if the missing heat is hiding at the bottom of the ocean it isn't going to do much warming until it comes to the surface is it?"Well, actually that may already be happening (seehere), and it will most certainly be something for future generations to worry about.muoncounterat 07:08 AM on 20 January, 2011dana1981at 07:45 AM on 20 January, 2011NETDRat 08:07 AM on 20 January, 2011Moderator Response:The original post is about Monckton's claim of linearwarming. muoncounter showed you (again) the nonlinearwarmingcaused by nonlinear increases in CO2. You keep saying the extra (more than linear) increases are not a problem, without addressing the actual problem of more than linear increases in warming. The difference of even "just" one more degree of warming on top of the linear warming is quite important in consequences. If you want to arguethatis not important, type "It's not bad" in the Search field at the top left of the page.muoncounterat 08:51 AM on 20 January, 2011Delta Tand_{S}=Delta F =. The big triangle is 'Delta'. And since you clearly don't see the importance of any of this, those red dots are actual temperature anomalies (shifted to 0 in 1880). Sure looks like the red stuff is coming up between two of the blues, matching the rate of change pretty well. That's what's called a match of observation to model -- and it's a sign that the model is pretty good. Thank you for demonstrating so admirably the total failure of this denialist argument and the total abandonment of reality that is needed to cling to it. But I do agree with you, this discussion isover.Neutrinoat 09:44 AM on 20 January, 2011marginallychanges the outcome. Yet if I run the numbers on the two i get significantly different results. Today CO2 (from mlo) is 389.78ppm, in 2100(90 years from now) your linear projects it to be 516.50ppm and your quadratic projects 673.20ppm, a 30% difference! Now the radiative forcing(as I understand it) is proportional to the ln of the change in the CO2(ie ∆F = 5.35*ln(C/Co)). If we take today as the baseline and look 90 years into the future there is asignificantdifference between the two. For your linear: ∆F = 5.35*ln(516.50/389.78) = 1.51 For your quadratic: ∆F = 5.35*ln(673.20/389.78) = 2.92 SoIfCO2 is raising at your quadratic rather than your linear then we should expect to see almostdoublethe temperature rise over the next 90 years. To say that is a trivial difference just seems plain wrong to me.