Archives for August 2008

Dear Jennifer,

A couple of weeks ago I became quite agitated after reading an article in The Australian’s Higher Education section by Roger Jones of CSIRO. Jones questioned the sceptics drawing attention to flaws in the computer models and then went on to explain what the models were supposed to do, not what they actually do!

I responded to The Australian with the following submission:

Global Warming: Solving an Environmental Problem or Creating a Social Crisis?

Prevention of dangerous climate change, particularly through implementation of a national carbon pollution reduction scheme, has emerged as a primary policy objective of the Rudd government. The rationale for the policy is the scientific assessment of the Intergovernmental Panel on Climate Change (IPCC) and its computer-based projections of global warming. We are told by the IPCC ‘consensus of scientists’ that continued burning of fossil fuels, and a range of other industry activities that increase the concentration of ‘greenhouse gases’ in the atmosphere, will lead to dangerous climate change, possibly passing a ‘tipping point’ causing ‘runaway global warming’.

What does this all mean, really?

The IPCC’s most recent assessment attempts to be helpful to the casual enquirer by having a series of explanations for ‘frequently asked questions’, or FAQs. The first FAQ is ‘What factors determine earth’s climate’? We are informed that, on average, the earth emits 240 w m-2 of radiation to space and that this equates to an emission temperature of -19oC. The earth’s temperature, however, is about 14oC and the -19oC temperature is found at a height of about 5 km above the surface. To quote the IPCC: “The reason the earth’s surface is this warm is the presence of greenhouse gases, which act as a partial blanket for the longwave radiation coming from the earth’s surface. This blanketing is known as the natural greenhouse effect”.

This explanation by the IPCC is clearly misleading, if not wrong. The inference that the greenhouse gases are acting like a blanket suggests that they are increasing the insulating properties of the atmosphere. However, the main gases of the atmosphere are oxygen and nitrogen, non-greenhouse gases, and they are also excellent insulators against the conduction of heat (like a blanket); adding additional trace amounts of carbon dioxide will have no appreciable impact on the insulating properties of the atmosphere.

In its third FAQ, ‘What is the greenhouse effect?’ the IPCC comes to the nub of the issue but provides a different and equally misleading explanation. “Much of the thermal radiation emitted by the land and the ocean is absorbed by the atmosphere, including clouds, and reradiated back to earth. This is called the greenhouse effect”. According to the IPCC’s global energy budget, the surface emits 390 W m-2 of radiation and the energy radiated back to the surface is 324 W m-2. It is difficult to see how an ongoing net loss of longwave radiation energy from the surface of 66 W m-2 can lead to warming! Indeed, we are all aware that between dusk and dawn the earth’s surface cools.

The IPCC has not explained in a scientifically sound and coherent way, how the ‘greenhouse effect’ is maintained. The greenhouse gases do not increase the insulating properties of the atmosphere and the back radiation does not warm the surface. The IPCC explanation of the greenhouse effect is obfuscation and, even to the mildly scientific literate, reflects ignorance of basic processes of the climate system.

How then do we explain to people who are going to be affected by reactionary government policies what are the greenhouse effect and its enhancement by additional carbon dioxide?

A credible explanation has no need for smoke and mirrors. The energy flow through the climate system is predominantly by way of four stages: 1) absorption of solar radiation at the surface; 2) conduction of heat and evaporation of latent energy from the surface to the atmospheric boundary layer; 3) convective overturning that distributes heat and latent energy through the troposphere; and 4) radiation of energy from the atmosphere to space. We will see that it is the characteristics of convective overturning that keep the surface warmer than it would otherwise be.

The Kiehl and Trenberth (1997) global average energy budget of the earth is used by the IPCC and is a useful starting point for explanation of the establishment and maintenance of the greenhouse effect.

Of the 340 units of solar radiation entering the earth’s atmosphere, 67 are absorbed by the atmosphere and 168 are absorbed at the surface. There is thus an ongoing source of solar energy available to the atmosphere and the surface.

At the surface there is a net accumulation of radiation energy because the incoming solar radiation (168 units) exceeds the net loss of longwave radiation (66 units).

In the atmospheric layer there is absorption of 417 units (390 of emission from the surface, less 40 that go directly to space, plus absorption of 67 of solar radiation) and an emission of 519 units (324 back to the surface and 195 direct emission to space). The net effect of the interaction between the greenhouse gases and radiation is a tendency to cool the atmosphere because it is continually losing energy.

Overall there is a dichotomy, with radiation processes firstly tending to warm the earth’s surface and secondly tending to cool the atmosphere. Air is an excellent insulator against conduction of heat and will not transfer heat through the atmosphere, as is necessary for energy balance. Also, the thermodynamic properties of air (potential temperature increases with height) ensure that turbulent motions of the atmosphere will mix energy downward, not upward as required.

The process for transferring energy from the surface to the atmosphere, necessary to achieve overall energy balance of the climate system, was explained by Herbert Riehl and Joanne Malkus (the latter better known as Joanne Simpson) in a 1958 paper, On the heat balance of the equatorial trough zone (Geophysica). Riehl and Malkus noted that boundary layer air, rising buoyantly in the protected updraughts of deep tropical convection clouds, converts heat and latent energy to potential energy. Away from the convection, compensating subsidence converts potential energy to heat.

What is implied in the Riehl and Malkus model is that deep tropical convection, and the transfer of energy from the surface to the atmosphere, will not take place without buoyant updraughts within deep convection clouds. That is, there is a need for the temperature of the atmosphere to decrease with altitude and that the rate of decrease of temperature must be sufficient to allow buoyancy of the air ascending in the updraughts. From well-known thermodynamic laws, the rate of decrease of temperature must be at least 6.5oC/km to allow the buoyancy forces of convection to overcome the natural stratification of the atmosphere.

The climate system will come into energy equilibrium when temperatures are such that the net solar radiation absorbed is balanced by the longwave radiation to space. At equilibrium, the greenhouse effect (ie, that the average surface temperature of 14oC is greater than the -19oC blackbody emission temperature of earth) is an outcome from the need for convective overturning of the atmosphere.

Additional warming of the surface will come about when the greenhouse effect is enhanced. The fundamental question is how much warming will additional greenhouse gas concentrations cause and will it be dangerous?

An increase in the atmospheric carbon dioxide concentration reduces the emission of longwave radiation to space and increases the back radiation at the surface. An increase in back radiation adds energy to the surface, which will further warm the surface. However there is a constraint on the surface temperature rise because of the commensurate increase in rate of energy loss from the surface: both the rate of infrared emission and the rate of evaporation of latent heat increase with temperature.

The increase in radiation emission from the surface can be calculated from the well-known Boltzmann equation and is 5.4 units/oC at 15oC. The earth’s surface is mainly ocean or freely transpiring vegetation and evaporation will increase near exponentially with temperature according to the Claussius-Clapeyron relationship and is 6.0 units/oC at 15oC. According to the IPCC, the radiative forcing from doubling of carbon dioxide concentration is 3.7 units.

The actual surface temperature increase is derived from the ratio of the radiation forcing (3.7) to the natural rate of increase in surface energy loss with temperature (5.4 + 6.0). The direct surface temperature rise from a doubling of carbon dioxide is therefore 3.7/(5.4 + 6.0) = 0.3oC.

A 0.3oC global temperature increase towards the end of the 21st century from a doubling of current carbon dioxide concentration is not obviously dangerous. However, what also needs to be taken into account is the positive feedback. A warming of the surface temperature will cause a warming of the overlying atmosphere, an increase in the water vapour concentration (another naturally occurring greenhouse gas), a further increase in back radiation, and an incremental increase in surface temperature. Each successive incremental surface temperature increase will cause another incremental temperature increase through the positive feedback amplification.

The amplification follows standard mathematical treatment and, as long as the ratio r is less than unity, the gain is given by [1 / (1 – r)]. Here r is the ratio of natural increase in back radiation with temperature (4.8 units/oC – estimated from a standard radiation transfer model) to the natural increase of surface energy loss with temperature (as previously, 11.4 units/oC). The natural gain is 1.7 and increases the surface temperature rise from a doubling of carbon dioxide concentration from 0.3oC to 0.5oC.

A 0.5oC increase in global temperature over the coming century is within recent short-term temperature variability and is less than the apparent global temperature rise of the past century. Moreover, both the direct forcing of surface temperature and the amplification gain are tightly constrained by the magnitude of the natural increase of surface energy loss with temperature increase. It is not immediately apparent how ‘runaway global warming’ could come about with such a constraint.

A fundamental question arises as to why the IPCC global temperature projections for doubling carbon dioxide concentration, based on computer models of the climate system, lead to estimates of about 3oC, or about six times the above estimate.

A clue to the conundrum can be found in published descriptions of the performance of the computer models used in the IPCC fourth assessment. Isaac Held and Brian Soden, writing in the Journal of Climate (2006) note that the rate of increase of evaporation in the computer models, on average, only increases at about one-third of the rate expected from the Claussius Clapeyron relationship. Additionally, Frank Wentz and colleagues, writing in the journal Science (2007), have confirmed the under-specification of evaporation increase with temperature and, from satellite based observations, have determined that global evaporation does indeed comply with the Claussius Clapeyron relationship.

It is clear from the above formulation of the surface temperature rise and the associated amplification gain that each is sensitive to the specification of evaporation increase with temperature. Substitution of the average evaporation specification of computer models into the formulation will boost the projected temperature rise from the above expected value of 0.5oC to 1.5oC, the lower end of IPCC projections. When the specification of evaporation increase with temperature is very low, as in the more extreme models, then the feedback amplification gain increases to a value of about ten; the temperature sensitivity of the computer model becomes highly exaggerated and model would likely simulate the behaviour of runaway global warming. The behaviour, of course, is false and arises only because of the significant under-specification of evaporation.

Despite the many claims that the IPCC projections of human-caused global warming are sound, the consensus of climate scientists and that the science is settled, there are disturbing shortcomings to both the essential explanations and to the computer modelling. The shortcomings are disturbing because the projections and their associated predictions of diabolical impacts on environmental systems are the only rational justification given for wholesale government restructuring of our industrial base and lifestyles.

This is the first time in human history that there has been a conscious move at the national level to discard the tools that have underpinned security, wellbeing and comfort. We are deliberately abrogating energy usage from proven and widely available sources on the basis of a perceived environmental threat which is poorly articulated and substantiated only by recourse to obviously deficient computer modelling.

Why am I reminded of Charles MacKay’s 1841 tome, “Extraordinary popular delusions and the madness of crowds’?

William Kininmonth
Melbourne, Australia.

William Kininmonth is a former head of Australia’s National Climate Centre; a consultant to the World Meteorological Organization; and author of Climate Change: A Natural Hazard (2004, Multi-Science Publishing)

P.S. The four important papers underpinning my analysis are:

Riehl, H and J. Malkus, 1958. On the heat balance of the equatorial trough zone. Geophysica, v6, Nos 3-4 pp503-538 (This paper describes how heat and moisture from the tropical boundary layer is distributed through the troposphere by way of deep buoyant convection, thus offsetting net radiation loss of energy of the troposphere. Buoyant convection requires a decrease of temperature with altitude, thus the surface must be warmer than the effective emission temperature of the troposphere – the greenhouse effect!)

Priestley, C.H.B., 1966. The limitation of temperature by evaporation in hot climates. Agricultural Meteorology, 3 pp241-246 (This paper explains, supported by data, why deserts are hotter than vegetated lands. Essentially, the earth’s surface loses energy by way of conduction, evaporation and emission of infrared radiation; for dry surfaces there is a shift in energy loss to conduction and radiation at higher temperatures whereas for wet surfaces there is a shift to evaporation of latent heat at a lower temperature. This analysis clearly makes a nonsense of the IPCC claim of a linear relationship between surface temperature increase ΔTs and radiation forcing ΔF, that is, (ΔTs/ΔF = λ). From surface energy balance (or conservation of energy), ΔTs = ΔF*[4*σ*Ts4 + A*L*(dqs/dT)]. Here (dqs/dT) is the rate of increase of water vapour saturation specific humidity with temperature (the Claussius Clapeyron relationship); the first term in the brackets on the right hand side is the rate of increase of surface infrared emission with temperature; and the second term is the rate of increase of latent heat exchange with temperature. For a dry surface, the rate of increase of infrared emission with temperature is approximately linear over short temperature ranges – earth’s surface happens to be approximately 70 percent water and a large part of the remainder is transpiring vegetation.)

Held, I.M. and B.J. Soden, 2006. Robust response of the hydrological cycle to global warming. J of Climate, v19 pp5686-5699 (The paper identifies that, in the GCM used in the IPCC fourth assessment, the rate of increase of surface evaporation is on average only one third the Claussius Clapeyron relationship (dqs/dT). The authors use this deficiency to explain why the rate of convective overturning of the models decreases as temperature increases. The important point is that the GCM apparently significantly under-estimate surface evaporation and latent heat exchange with temperature increase.)

Wentz, F.J., L. Ricciardulli, K. Hilburn and C. Mears, 2007 How much more rain will global warming bring? ScienceExpress 31 May (published later in Science, 13 July 2007). (This paper confirms, from satellite data over recent decades, that global precipitation (and hence evaporation and latent heat exchange) increases with temperature according to the Claussius Clapeyron relationship. Thus the under-estimation of evaporation in GCM also implies an underestimation of precipitation increase with warming. The authors do not recognise that under-estimation of evaporation and latent heat exchange will also lead to overestimation of surface temperature rise! I have quantified the over-estimation of global temperature rise in the analysis that follows.)

Bishop Hill blog has put together the story of the Amman and Wahl paper that purported to support the ‘hockey stick’ reconstruction of paleoclimate, cited in IPCC AR4:

There has been the most extraordinary series of postings at Climate Audit over the last week. As is usual at CA, there is a heavy mathematics burden for the casual reader, which, with a bit of research I think I can now just about follow. The story is a remarkable indictment of the corruption and cyncism that is rife among climate scientists, and I’m going to try to tell it in layman’s language so that the average blog reader can understand it. As far as I know it’s the first time the whole story has been set out in a single posting. It’s a long tale – and the longest posting I think I’ve ever written and piecing it together from the individual CA postings has been a long, hard but fascinating struggle. You may want to get a long drink before starting, and those who suffer from heart disorders may wish to take their beta blockers first.

Read the entire blog post entitled: ‘Caspar and the Jesus paper’

Two new papers examining the link between Hurricanes and climate have been published in the Journal of Climate.

In the July edition, Gabriel A. Vecchi and Thomas R. Knutson have a paper entitled: ‘On Estimates of Historical North Atlantic Tropical Cyclone Activity’

The Abstract states:

In this study, an estimate of the expected number of Atlantic tropical cyclones (TCs) that were missed by the observing system in the presatellite era (between 1878 and 1965) is developed. The significance of trends in both number and duration since 1878 is assessed and these results are related to estimated changes in sea surface temperature (SST) over the “main development region” (“MDR”). The sensitivity of the estimate of missed TCs to underlying assumptions is examined. According to the base case adjustment used in this study, the annual number of TCs has exhibited multidecadal variability that has strongly covaried with multidecadal variations in MDR SST, as has been noted previously. However, the linear trend in TC counts (1878–2006) is notably smaller than the linear trend in MDR SST, when both time series are normalized to have the same variance in their 5-yr running mean series. Using the base case adjustment for missed TCs leads to an 1878–2006 trend in the number of TCs that is weakly positive, though not statistically significant, with p 0.2. The estimated trend for 1900–2006 is highly significant (+4.2 storms century−1) according to the results of this study. The 1900–2006 trend is strongly influenced by a minimum in 1910–30, perhaps artificially enhancing significance, whereas the 1878–2006 trend depends critically on high values in the late 1800s, where uncertainties are larger than during the 1900s. The trend in average TC duration (1878–2006) is negative and highly significant. Thus, the evidence for a significant increase in Atlantic storm activity over the most recent 125 yr is mixed, even though MDR SST has warmed significantly. The decreasing duration result is unexpected and merits additional exploration; duration statistics are more uncertain than those of storm counts. As TC formation, development, and track depend on a number of environmental factors, of which regional SST is only one, much work remains to be done to clarify the relationship between anthropogenic climate warming, the large-scale tropical environment, and Atlantic TC activity.

The paper concludes:

Overall, our findings suggest that it is possible that Atlantic TC counts may have significantly increased since the late nineteenth century, although the evidence is decidedly mixed, with some other activity measures showing either no change or a decrease with time. Total storms per year and U.S. landfalling activity show no increasing trend, and average TC duration shows a significant decrease over time. Further, attribution of an increase in tropical storm counts to any particular mechanism (including increasing greenhouse gasses or natural decadal variations) would require further dynamical analysis to complement any observational results. It is noteworthy that in our adjusted record of TCs the sensitivity of basin-wide storm counts to local SST is smaller for the longest time scales (e.g., trend since 1878) than for the pronounced multidecadal variability, although the current observational “best estimate” would be that this sensitivity is positive. Additional study is needed to reconcile these findings with climate simulations of past and future Atlantic storm activity. Future work should also focus on including more ship-track information where possible and examining assumptions about landfall detection in earlier years, and historical tropical cyclone database reconstructions should be extended to include other basins.

See also Discovery Channel News: Warming Won’t Drive More Hurricanes, Study Says

In the August edition of the Journal of Climate, Philip J. Klotzbach and William M. Gray have a paper entitled: ‘Multidecadal Variability in North Atlantic Tropical Cyclone Activity’

The Abstract states:

Recent increases in Atlantic basin tropical cyclone activity since 1995 and the associated destructive U.S. landfall events in 2004 and 2005 have generated considerable interest into why there has been such a sharp upturn. Natural variability, human-induced global warming, or a combination of both factors, have been suggested. Several previous studies have discussed observed multidecadal variability in the North Atlantic over 25–40-yr time scales. This study, using data from 1878 to the present, creates a metric based on far North Atlantic sea surface temperature anomalies and basinwide North Atlantic sea level pressure anomalies that shows remarkable agreement with observed multidecadal variability in both Atlantic basin tropical cyclone activity and in U.S. landfall frequency.

The paper concludes:

This paper expounds upon previous research by highlighting Atlantic basin multidecadal variability in both large-scale atmospheric–oceanic fields as well as Atlantic basin TC (tropical cyclone) activity. Using an index of basinwide SLP (sea level pressure) and far North Atlantic SSTs (sea surface temperatures), positive and negative periods for the AMO (Atlantic multi-decadal oscillation) can be clearly delineated. When the AMO is in its positive phase, TC activity in the Atlantic basin is heightened, especially for MH (major hurricane) activity. Landfalling hurricanes along the U.S. coastline also become more frequent, with the most dramatic increases in a positive AMO phase being seen for the U.S. East Coast and the Florida Peninsula. Additional research involving potential physical drivers of the AMO should be conducted.