Debunking Bloomberg's 'alarming' climate graph: Are we really on track for 4°C global warming by 2100?

By Christopher Monckton of Brenchley

David Burton has already done a wonderful deconstruction of Bloomberg’s absurd global warming attribution graph, by Eric Roston and Blacki Migliozzi, contrived from data by the notoriously unreliable NASA GISS, purporting to demonstrate that 20^th-century global warming was reely ’n’ truly all caused by our sins of emission, honest it was, guv’nor, cross me ’eart an’ ’ope to die.

What that graph really helps to indicate – though its fanatical originators would be horrified if they realized it – is just how little global warming we are likely to see this century, even if no one cuts emissions at all from now on and CO2 concentration continues inexorably to climb.

The usual suspects – such as the British Communist newspapers The Guardian and The Independent, for instance – have been telling us for the past few years that “scientists say” we are on track for 4 C° global warming this century. Well, we aren’t. Here’s why.

Version A of the Bloomberg graph shows the alleged temperature effects of various individual manmade forcings; version B shows the temperature effects of all the individual manmade forcings combined; and version C, scarcely different from B, shows the combined effect of all manmade and natural forcings.

David Burton has already pointed out numerous dodges deployed by GISS in the crafting of this characteristically misleading graph: the truncation of all but the temperature data after 2005 to conceal the rapidly growing and now irremediably serious divergence between prediction and reality, the GISS model’s estimates that in several of the past 100 years the greenhouse forcing actually fell; the model’s use of multiple pseudo-random number generators in the absence of sufficient climate observations; the bizarre choice of a faster greenhouse-gas influence half a century ago than today; the ex-post-facto guesstimates of both individual manmade and combined natural forcings; and the fiddled confidence intervals for greenhouse-gas influences on temperature that are as narrow for 140 years ago as they are for today.

But that’s not all, as the same graph overlaid with the natural 20-to-30-year cooling and then warming phases of the Pacific Decadal Oscillation reveals. The biggest omission from the GISS/Bloomberg graph is synoptic natural variability. Indeed, the graph goes to some lengths to conceal it, not least by removing the decade-lines (here reinstated). GISS also chose a negative or cooling PDO phase as its 30-year baseline, rather than the near-60-year baseline 1890-1946, which includes a full cooling and then warming phase of the PDO (all PDO dates are from JISAO).

The true baseline is a tenth of a degree above the artificially-chosen GISS baseline that makes the net 20^th-century warming look quite a bit more severe than it was.

Note how the cooling phases (starting with green year-lines) show little or no global warming. See also how there was 0.3 C° warming coincident with the PDO warming phase from 1925-1946, when hardly any anthropogenic influence had been felt. See how the 0.7 C° global warming from 1977-2000 coincided with a positive or warming phase of the PDO.

See how little warming there has been since 2000, in the present negative or cooling phase of the PDO, even on the much-fiddled GISS temperature dataset, notwithstanding record increases both in CO2 emissions and CO2 concentration.

In the first PDO-influenced warming period, our influence was not large enough to cause all of the observed warming. Let us assume we caused as much as 0.2 C° of the 0.3 C° warming shown.

In the second PDO-influenced warming period, McKitrick & Michaels (2007) showed that warming over land had been overestimated by double, because the published data show a highly significant regional correlation with growth of population and urbanization that should not have been present if the urban heat-island effect had been properly allowed for. That alone leads to an overstatement of 0.1 C° in global temperature.

In addition, some 0.3 C° of the published terrestrial warming since 1900 arises from data adjustments by NCDC/GISS rather than from a real temperature change. Let us deduct from the record just one-third of that, or 0.1 C°:

Thus, out of the 0.9 C° 20^th-century warming, 0.1 C° was natural; 0.1 C° was attributable to inadequate correction for urbanization; and at the very least 0.1 C° arose from over-enthusiastic tampering with the temperature record in a manner calculated artificially to steepen the apparent warming, leaving at the very most just 0.6 C° of anthropogenic warming over the 20^th century.

Have we been reasonable in making this estimate of anthropogenic warming to date? We can check by reference to the IPCC’s estimates of total manmade forcings. These, given in Fig. SPM.6 of IPCC (2013), come out at 2.3 Watts per square meter since 1750 (or, effectively, since 1880, since our influence before that date was negligible):

The current best estimate of the top-of-atmosphere radiative imbalance caused by this forcing but thus far unresolved by increases in atmospheric temperature is 0.6 W m^–2, so that the 0.6 C° anthropogenic warming realized to date was driven by the remaining 1.7 W m^–2 of radiative forcing, implying a final or post-feedback transient-climate-sensitivity parameter of 0.6/17 = 0.353 Kelvin per Watt per square meter.

Now, the instantaneous or zero-feedback parameter is 0.313 K W^–1 m², and after 100 years the IPCC estimates that this will rise to 0.43 K W^–1 m², or about half, of the 0.86 K W^–1 m² that it expects to obtain at equilibrium.

Given that almost three-quarters of the anthropogenic forcing has arisen in the 70 years since 1950, so that much of the centennial forcing has not yet occurred, the implicit value 0.353 K W^–1 m² that we have derived on the back of an envelope for the transient sensitivity parameter is indeed in the right ballpark, suggesting that 0.6 C° is a reasonable estimate of the anthropogenic warming of the 20^th century.

Armed with this information, we can proceed to work out whether we are going to see anything like the imagined 4 C° warming in the next 85 years.

The CO2 forcing for the remainder of the 20^th century is 5.35 times the logarithm of the proportionate change in concentration, which is now 0.04% of the atmosphere by volume and, on business as usual, is projected by the IPCC to rise to 0.07%.

Thus, the CO2 forcing would be 5.35 ln 7/4, or 3.0 Watts per square meter. Since the IPCC’s current estimate is that CO2 accounts for five-sixths of all anthropogenic forcings, this should be increased by a fifth to 3.6 W m^–2.

Next, one must allow for temperature feedbacks amounting to 1.55 Watts per square meter per Kelvin of direct warming:

That gives equilibrium warming of 1.8 C° as a result of 20^th-century forcings.

If the forcings were to occur at once rather than spread over the coming century, only half of this, or 0.9 C°, would occur within a century, and the rest within 1000-3000 years (Solomon et al., 2009).

However, since the forcing will build up slowly over the century, perhaps with a slight increase in the top-of-atmosphere radiative imbalance as well, in practice only about a third of equilibrium warming is at all likely to appear by 2100. That is just 0.6 C°, of which precisely none has occurred in the first 15 years of the century.

One might add a little to this to allow for some further warming caused by past emissions, or take quite a bit away to allow for the strongly canceling influence from manmade particulate aerosols, the tiny parasols that increase the opacity of the atmosphere and shelter us somewhat from the Sun.

Murphy et al. (2009) go as far as to imagine that the negative aerosol forcing almost cancels out the CO2 forcing altogether.

If they are right, and if the increasing industrialization of China, India and Africa continue to increase particulate aerosols in step with CO2, very little warming can be expected in the 21^st century:

So far, every step of our calculation has been rooted in mainstream, established climate science, published data and peer-reviewed papers.

Can one go still further? In one respect, no. As Roy Spencer pointed out with characteristic focus and concision in response to my previous posting, merely because the energy budget diagrams use the Stefan-Boltzmann equation at the Earth’s surface we must not assume that we can derive the Planck climate-sensitivity parameter from them. We must apply the equation at the characteristic-emission surface, which is the locus of all points at or above the Earth’s surface at which, under the assumption of a pre-existing radiative equilibrium, incoming and outgoing radiative fluxes are equal. We cannot take advantage of the far lower surface sensitivity parameter that obtains at the surface.

What if we assume that temperature feedbacks are net-zero, an assumption powerfully suggested by 810,000 years of near-perfect thermostasis, with global temperature varying by little more than 3 C° either side of the long-run mean (a variance about the same as that of your home thermostat)?

The “consensus” would have us believe that the temperature changes of the past 810,000 years, covering an interval of at most 6.5 C°, were driven by tiny forcings amplified by hefty feedbacks. It is no less likely, however, that the forcings from events such as supervolcano explosions and Milankovitch cycles were large and the feedbacks small – perhaps even net-negative.

If the feedbacks were net-zero, the instantaneous and equilibrium warmings in response to the 3.6 W m^–2 manmade forcings expected in the remainder of this century, assuming none of the strongly negative forcings from aerosols, land-use changes and ozone effect that the GISS/Bloomberg graph assumes, will simply be 0.313 x 3.6 Watts per square meter, or 1.1 C°, of which about half would arise over a century because the change in concentration is not instantaneous but is spread over the next 85 years.

Result: about 0.5-0.6 C° of global warming, not much different in the medium term from the high-feedback case.

Whichever way you stack it, it is difficult to make a serious case for even 1 C° of anthropogenic warming by 2100, even on business as usual.

I shall probably not be around in 85 years’ time to find out. Yet perhaps the scholars of the future, peering at these postings at WattsUpWithThat, may one day marvel that, armed with nothing more than common sense, an ambition to find the truth rather than make a fast and dishonest buck, a pocket calculator and the simple model in Monckton of Brenchley (2015: just go to scibull.com, the website of the Science Bulletin of the Chinese Academy of Sciences, and click “Most Read Articles”, as more than 30,000 others have done), we were able to reach a far more reliable estimate of this century’s global warming than the billion-dollar brains of the profiteers of doom.

4 C° global warming by 2100? Fuggedaboudid. Will someone tell the sanctimonious global-government wannabes in Washington DC, London, Bonn, Rome, and – above all – Paris?