The collapse of arguments for high climate sensitivity

Guest essay by Dr Doug Hoyt

In the past few years, three articles have come out that, taken together, lead one to conclude that climate sensitivity is very low, being less than 1 C for a CO2 doubling compared to the 3 C figure favored by the IPCC.

The first article is by Levitus et al (2005). They conclude that the oceans warmed by 0.06 C between 1948 and 1998. It represented an increase in heat content of 2 x 10^23 joules.

In 2006, Lyman et al. showed that the oceans cooled between 2003 and 2005 with a net loss of energy of 0.32 x 10^23 joules. Climate models do not predict or allow for such cooling of the oceans.

In 2007, Gouretski and Koltermann showed that the early heat content measurements were incorrect because they did not take into account changes in instrumentation. They concluded that between 1955 and 1996 that the oceans only gained 1.28 x 10^23 joules with an uncertainty of 0.8 x 10^23 joules. Essentially the earlier Levitus paper was wrong.

Combining the Lyman and Gouretski papers, the net ocean heat content between 1955 and 2005 seems to be only 0.98 x 10^23 joules with an error of (0.8 + 0.11) x 10^23 joules or 0.91 x 10^23 joules, adding the error terms of the two papers. The net heat content change is therefore essentially statistically indistinguishable from zero. The net warming of the ocean from 1948 to the present seems to be only 0.03 +/- 0.03 C.

The corresponding net radiative imbalance is about 0.1 W/m^2, well below the model predictions which equal 0.85 W/m^2 for 1993 to 2003 (Hansen et al., 2005). Instead of a climate sensitivity of 3 C for a CO2 doubling, the climate sensitivity is only about 0.4 C. There is little or no energy “in the pipeline” and thus a good reason to believe that all the observed warming of the atmosphere has already occurred.

The atmospheric warming of 0.6 C between 1900 and 2000 is presumably forced by 2.7 W/m^2 from all greenhouse gases. The forcing from a doubling of CO2 is about 3.7 W/m^2 which would correspond to a climate sensitivity of 0.8 C for a CO2 doubling if all the warming of the twentieth century was caused by greenhouse gases. Since even the IPCC concedes that half the warming may be coming from other causes (such as solar), the calculated climate sensitivity becomes 0.4 C for a CO2 doubling. This low sensitivity is consistent with the low values derived by Lindzen (0.5 C) and Idso (0.4 C) and others. It is also consistent with the analysis of the oceans discussed above.

There is no hiding of global warming in the oceans is as commonly argued. The results are consistent with the fact that 15 micron thermal radiation from carbon dioxide will only heat the upper 15 microns of the oceans, a topic to which we now turn.

Comments on why the ocean isn’t absorbing thermal infrared energy

The absorption coefficient for liquid water as a function of wavelength is given at (see the figure near the end). Thermal infrared in the Earth’s atmosphere is around 10 to 20 microns where the absorption coefficient (A) is about 1000 cm-1. For the transmission in liquid water (T), we have

T = exp(-A*L)

where L is the depth of penetration. For the case where 1/e or 27% of the incident photons remain unabsorbed and with A=1000 cm-1, then L= 1/1000 cm = 0.01 mm. 98% of the incident photons will be absorbed within 3 times this distance.

So one can see from the figure, than practically no infrared photons penetrate beyond 0.03 mm. A more precise estimate of A is 5000 cm-1 at 15 microns where carbon dioxide is emitting radiation, so 0.006 mm is a more accurate number for the depth of penetration of 98% of the photons arising from carbon dioxide forcing. For the sake of argument, we will say that all the 15 micron thermal radiation at 15 microns arising from increased carbon dioxide in the atmosphere is absorbed in the upper 15 microns of the ocean, based upon electromagnetic theory. Since the liquid water is such an effective absorber, it is a very effective emitter as well. The water will not heat up, it will just redirect the energy back up to the atmosphere much like a mirror, but not exactly a mirror, and this is an important point.

For A = 5000 cm-1 at 15 microns, the implied water emissivity is 0.9998 implying that, of the incident radiation, only 0.02% of it will ultimately be absorbed in the water. The emitted radiation will closely follow a blackbody emission curve whereas the incident flux from carbon dioxide is confined to a band centered at 15 microns. The implication of this is that much of the radiation emitted will escape directly to space through the IR windows, so it could be viewed as a negative feedback. About 40% of the energy will escape this way. Alternatively, this mechanism implies that climate will be less sensitive to greenhouse gas warming than it would be to an equal solar radiation forcing. In addition, there are many moist areas over land and clouds are also moist, so this negative feedback or reduction in climate sensitivity is also operable nearly everywhere.

The above mechanism works because the initially absorbed infrared energy cannot be transferred to the ocean depths by conduction (too slow), by convection (too small an absorption layer compared to the size of convective cells), or by radiation (too opaque). It must escape by the fastest way possible meaning upwards radiation away from the water. Also since the surface layer where the absorption occurs is cooler than the water just below it, there can be no net transfer of energy by conduction, convection, or radiation downwards because it would violate the laws of thermodynamics.

Consequently, the only way to explain the ocean heating in depth is for the solar radiation to change and decreasing clouds between 1985 and 2000, as measured by ISCCP, indicate increasing solar radiation occurred at the same time that the ocean heating is reported to have occurred. Ocean warming papers do not even mention the ISCCP data that has a similar geographic distribution to the water warming. Simply put, where clouds decrease in amount, the water warms. It has nothing to do with carbon dioxide.

A handy plot of the ISCCP results can be found as Figure 3 at where clouds are shown to decrease for 1987-2000. In a paper by Willis, his Figure 4b, covering 1992-2003, is the one that should be compared to Figure 3. Although the dates do not exactly overlap, the spatial patterns are very similar. There is a need to plot both variables over the exact same time interval, but it is unlikely it would change the major conclusions presented here. Clouds have large natural variations going up and down entirely independent of any greenhouse effect. The climate models do not predict these variations and apparently climate scientists are unaware of these variations and thus do not consider them.

In summary then, the net warming of the oceans since 1948 is small and statistically indistinguishable form zero. The best estimate for climate sensitivity is about 0.4 C for a CO2 doubling and you get this answer using either ocean temperatures or atmospheric temperatures. There is no delayed warming “in the pipeline”. The theoretical interaction of thermal radiation with water shows it cannot be the source of any observed ocean warming. The slight warming and cooling cycles in the oceans seem to arise from fluctuations in cloud cover that may be unforced oscillations, or perhaps may be forced by, for example, cosmic ray variations.

In essence the climate models are wrong in their physics, and wrong in predicting large future warming.

Major references with abstracts:

Levitus, S., Antonov, J. and Boyer, T. 2005. Warming of the world ocean, 1955-2003. Geophysical Research Letters 32: 10.1029/2004GL021592.

The abstract reads:

We quantify the interannual-to-decadal variability of the heat content (mean temperature) of the world ocean from the surface through 3000-meter depth for the period 1948 to 1998. The heat content of the world ocean increased by ~2 × 1023 joules between the mid-1950s and mid-1990s, representing a volume mean warming of 0.06°C. This corresponds to a warming rate of 0.3 watt per meter squared (per unit area of Earth’s surface). Substantial changes in heat content occurred in the 300- to 1000-meter layers of each ocean and in depths greater than 1000 meters of the North Atlantic. The global volume mean temperature increase for the 0- to 300-meter layer was 0.31°C, corresponding to an increase in heat content for this layer of ~1023 joules between the mid-1950s and mid-1990s. The Atlantic and Pacific Oceans have undergone a net warming since the 1950s and the Indian Ocean has warmed since the mid-1960s, although the warming is not monotonic.

Lyman, J. M., J. K. Willis, and G. C. Johnson (2006), Recent cooling of the upper ocean, Geophys. Res. Lett., 33, L18604, doi:10.1029/2006GL027033

The abstract reads:

“We observe a net loss of 3.2 (± 1.1) X 10**22 J of heat from the upper ocean between 2003 and 2005. Using a broad array of in situ ocean measurements, we present annual estimates of global upper-ocean heat content anomaly from 1993 through 2005. Including the recent downturn, the average warming rate for the entire 13-year period is 0.33 ± 0.23 W/m2 (per unit area of the Earth’s surface). A new estimate of sampling error in the heat content record suggests that both the recent and previous cooling events are significant and unlikely to be artifacts of inadequate ocean sampling.”

Gouretski, V. and Koltermann, K.P. 2007. How much is the ocean really warming? Geophysical Research Letters 34: 10.1029/2006GL027834.

The abstract reads:

We use a global hydrographic dataset to study the effect of instrument related biases on the estimates of long-term temperature changes in the global ocean since the 1950s. The largest discrepancies are found between the expendable bathythermographs (XBT) and bottle and CTD data, with XBT temperatures being positively biased by 0.2–0.4°C on average. Since the XBT data are the largest proportion of the dataset, this bias results in a significant World Ocean warming artefact when time periods before and after introduction of XBT are compared. Using bias-corrected XBT data we argue reduces the ocean heat content change since the 1950s by a factor of 0.62. Our estimate of the ocean heat content increase (0–3000 m) between 1957–66 and 1987–96 is 12.8·1022 J. Because of imperfect sampling this estimate has an uncertainty of at least 8·1022 J.

Ellis T.D., et al., 2004. Evaluation of cloud amount trends and connections to large scale dynamics. 15th Symposium of Global Change and Climate Variations, Paper No. 5.7, American Meteorological Society.

This paper shows the trends in cloud cover for 1987-2001. The spatially patterns are very similar to the spatial patterns for ocean warming.

Willis, J. K., D. Roemmich, and B. Cornuelle (2004), Interannual variability in upper ocean heat content, temperature, and thermosteric expansion on global scales, J. Geophys. Res., 109, C12036, doi:10.1029/2003JC002260.

This paper shows the spatial patterns of ocean warming for 1992-2003, which are very similar to the spatial patterns of cloud change shown by Ellis (2004).

Hansen et al., 2005. Earth’s Energy Imbalance: Confirmation and Implications. Science, 308, 1431-1435.

This is the paper that claims a 0.85 W/m^2 energy imbalance for the Earth. It has now been completely debunked by the papers listed above and by basic physics.

Hansen et al., 1985. Climate response times: Dependence on climate sensitivity and ocean mixing. Science, 229, 857-859.

This paper was not mentioned in the above, but it is the primary paper upon which the idea of a high climate sensitivity, a slow response time, and “in the pipeline” ideas originate. Of the many problems with this paper, a major one is that it assumes tritium atoms and infrared photons transport energy in an identical manner. If they don’t, the entire paper is nonsense.

54 thoughts on “The collapse of arguments for high climate sensitivity”

  1. Gerard Roe published a paper, In defense of Milankovich, which implies changes in CO2 forcing have less effect on temperature than changes in solar forcing.

    His abstract
    “The Milankovich hypothesis is widely held to one of the cornerstones of climate science. Surprisingly, the hypothesis remains not clearly defined despite an extensive body of research on the link between global ice volume and insulation changes arising from variations in the earth’s orbit. In this paper, a specific hypothesis is formulated. Basic physical arguments are used to show that, rather than focussing on the absolute global ice volume, it is much more informative to consider the time rate of change of global ice volume. This simple and dramatically logical change in perspective is used to show that the available records support a direct, zero lag, antiphased relationship between the rate of change of global ice volume and summertime insulation in the northern high latitudes. Furthermore, variations in atmospheric CO2 appear to lag the the rate of change of global ice volume. This implies only a secondary role for CO2 – variations in which produce a weaker radiative forcing than the orbitally induced changes in summertime insulation – in driving changes in global ice volume.

  2. Seasonally-resolved energy balance models having air−surface, land−ocean and Northern and Southern Hemisphere resolution are used to elucidate the possible relative importance of several 70-443 external factors on the climate of the past century. The model used here allows a direct comparison of observed and simulated temperatures from the same physical domains—over land and sea separately in each 70-444 hemisphere. The availability of independent temperature records in two hemispheres significantly increases the number of independent degrees of freedom in the 70-445 data available to ‘verify’ the simulations. Independent volcanic effects are found in both hemispheres, while similar responses for the more globally distributed CO2 and tentatively identified solar forcings are found in the two hemispheres. The empirically derived CO2 equilibrium doubling response for 70-446 air surface temperature is 1.6plusminus0.3°C, although the statistical significance of this result is uncertain.

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