Jae or Steve or Jan,

Or anyone who can help. You are all much more current with this than I am. I'm having a look at the tropical cyclones that start off near the Kimberley and then travel over land, sometimes intensifying, right down the the Bight. Current reading (eg Emanuel at al ) suggests that the cyclones can rejuvenate by taking heat energy from soil by wetting it to increase thermal conductivity ahead of the eye. It seems to me that there just is not enough reserve water in a cyclonic system to carry it for 5-7 days over the hot dry deserts of central WA in Summer. If you took a cat 4 or 5 cyclone and calculated its contained water content, roughly how many tonnes would it hold? For how long could it give typically heavy cyclonic rain, without uptake of water (hypothetical), before running out?

The topic seems obliquely relevant to this thread because it's part of the mass equations for water in and out of air and so has the ability to affect humidity/transparency subjects.

I'm playing the whore a bit and posting on several blogs, with some of the references and explanation on Climate Audit, Ryan M's thread "Great Depression! Global hurricane activity reaches new lows." See posts 107 and 127. I'm sorry I get out of my depth sometimes, but that's how one learns. Would be pleased if you could help.

Not to mention the partisan nature of science funding dispensed by Big Government and Big NGOs administered by jerks.

jae #11

"If there were any serious positive feedback, the Earth would have gone bananas many times in the geologic past. That’s the simplest demonstration that the modelers are wrong, IMHO."

I agree entirely. The paleo record has been abused utterly by those with an extremist AGW agenda. The stomatal index/stomatal density issue is just one example of how the supposed CO2 sensitivity of the past has been pumped up on dubious grounds. For every paper which identifies decrease in stomatal density with rising CO2 there is almost one equivalent paper which fails to find an effect or identifies all the situations both physical and genetic where it doesn't apply. A technique of limited specificity and severe qualification was rapidly blown up into one that had widespread general applicability.

If CO2 sensitivity had been as high as is claimed then not only would all corals etc have been long rendered extinct due to the stresses of so-called ocean acidification (at pCO2 less than ~2500 ppmv - the very same effect we are supposedly threatened with right now) but so-called coral bleaching from high SSTs (the very same effect effect we are also supposedly threatened with right now) would have also finished them off altogether. And yet the fossil record shows coralline algae are relatively robust organisms with large rates of genetic diversification under past periods of very high pCO2.

How did we fall into this startling abyss of 'science as fascism'? I blame an unholy conjunctive effect of 1960s green hippie ideology post Rachel Carson (and yes, I too inhaled - big time ;-), the rise of post WWII post-modernism and a late 20th century woeful decline in academic standards, almost exclusively in the English speaking countries (note well).

DG: I'm glad Roy Spencer is publishing articles that strongly question this sacred "positive water vapor feedbaack" notion, using empirical data. Otherwise, these jokers would have little resistance to their ASSUMPTION of "dangerous" positive feedback. There is no empirical evidence for this, as far as I know--it's all an assumption that is put into the models. These guys seem to have more faith in model results in real-world data.

If there were any serious positive feedback, the Earth would have gone bananas many times in the geologic past. That's the simplest demonstration that the modelers are wrong, IMHO.

http://geotest.tamu.edu/userfiles/216/Dessler20...
"The existence of a strong and positive water-vapor
feedback means that projected business-as-usual greenhousegas
emissions over the next century are virtually guaranteed to produce warming of several degrees Celsius. The only way that will not happen is if a strong, negative, and currently unknown feedback is discovered somewhere
in our climate system."

How does such barf mulch get past peer review to publication? Not one mention of cloud feedbacks. It is not unlike "this is the smoking gun we've been looking for" (Hansen et al 2005).

How many mulligans are they allowed?

Nope.

As Zhang et al (2001) showed, for a constant annual rainfall (water supply) ETa actually goes up with increasing plant biomass in the landscape. This has now been well established for about a decade. As I said Zhang et al (2001) is one of the most cited papers in geography. There are numerous other papers to support this concept.

FYI, the so-called 'Stomatal Index' or Stomatal Density' method of CO2 proxy measurement has taken a pounding in recent years from critical reviews. It is, in fact one of the key reasons for shonky AGW bandwagon over-estimates of CO2 sensitivity from the paleo record, principally because one man, Dana Royer, built his entire career on it (ignoring to this day all those niggling little papers which kept popping up showing the flaws in the method).

You might recall I posted info and references on that subject on Jennifer Marohasy's blog more than 18 months ago. Very, very quickly to recap please refer e.g.:

http://www.co2science.org/articles/V6/N45/B2.php

Steve Short,

one of the proxies that the paleo crowd use for CO2 is the size of the pores in leaves and other vegetation surfaces. Generally the more CO2 the smaller the pores. This REDUCES evapotranspiration increasing the ability of plants to grow better in drier periods.

As the CO2 level has increased worldwide this should translate to lower evapotranspiration world wide.

Anyone see any papers evaluating the gross change this would have??

I would add that there has definitely been a greening of the earth, so, it would be interesting if the increased vegetation balances the reduced evapo'.

Over the continents actual evapotranspiration (ETa) is much more important than potential (e.g. pan) and actual evaporation in terms of latent heat transfer to the atmosphere.

Over the continents there is a definite 30 year downward trend in potential (pan) evaporation (which would dictate evaporation off free water surfaces only). Roderick et al (2007) recently reviewed the data for Australia and New Zealand and showed this effect is most likely due principally to decreasing wind speeds rather than increasing near surface temperature.

Average wind speeds are decreasing by about 8 mm/y on the continents and increasing by a comparable amount over the oceans.

With respect to cloud (frequency/structure), the most recent studies are showing a small trend towards a decrease in cloud coverage but a marked increase in average cloud albedo.

One possible reason for this is the increasing mass of biogenic organic compounds (principally isoprenes) and inorganic compounds as well over the ocean (principally of sulfur) entering the lower atmosphere, presumably due to increasing biomass as CO2 rises (CO2 fertilization effect).

This could be expected to increase cloud density/albedo due to higher nucleation rates as is being found.

Plant biomass on the continents is rising due to the CO2 fertilization effect, hence ETa is rising (for each unit of rainfall). Soils exhibit far weaker nutrient limitations than water bodies. Plant biomass in the oceans should also rise but more slowly due to N, Fe and Si limitation constraints.

There is indirect evidence to show cyanobacterial biomass in oceans which is comparable to, or exceeds continental biomass, is probably also rising. This is certainly the case for the great Southern Ocean from 30 S to the the coast of Antarctica.

All I know is that the 30-year average data show a very smooth, very high correlation (R^2 = 0.98) between average temperature and average absolute humidity.

One should expect that they have the same cause and if one takes into account (only) the solubility pump atmospheric CO2 level has the same cause too.

Steve S:

"Actually, looking at the situation in a bulk, overall average sense, the primary determinants of the average annual actual evapotranspiration on the continents are not surface or air temperature at all but principally only the average annual precipitation (rainfall) and the proportions and types of vegetation (forest, herbaceous or grassland)."

All I know is that the 30-year average data show a very smooth, very high correlation (R^2 = 0.98) between average temperature and average absolute humidity.

Actually, looking at the situation in a bulk, overall average sense, the primary determinants of the average annual actual evapotranspiration on the continents are not surface or air temperature at all but principally only the average annual precipitation (rainfall) and the proportions and types of vegetation (forest, herbaceous or grassland).

One of the most cited papers of all time in geography is:

Zhang, L. Dawes, W.R. and Walker, G.R. (2001) Response of mean annual evapotranspiration to vegetation changes at catchment scale. Water Resour. Res. 37, 701-708

Zhang et al. (2001) studied over 250 catchments worldwide, of which 96 were within Australia, covering a wide range of soil and climate types.

Zhang et al’s model is based on empirical measurements from catchments with the following characteristics:
• rainfall the dominant form of precipitation (not irrigation);
• slopes of catchments gentle; and
• soil depth relatively thick (>2 m).

Zhang et al. (2001) found, following on from extensive earlier studies, that for a wide range of climates, mean annual ETa may be well predicted from mean annual precipitation (Pa) using an equation which only takes into account the proportion of woody vegetation (trees, shrubs) and proportion of grasses and low herbaceous species covering e.g. the catchment for which mean annual precipitation is known.

The Zhang et al. (2001) algorithm shown above is now used widely for the prediction of mean annual evapotranspiration at a coarse geographic scale using the following values for the 'w' factor:
• 2 for plantations, native forests and woodland
• 1 for native shrub lands and heath lands (including swamps), horticultural trees and shrubs and perennial crops;
• 0.5 for annual crops, pasture and native grasslands; and
• 0.1 for bare ground and built-up areas.

My company (an environmental/mining engineering consultancy) has found from our own studies in catchment hydrology that where the geomorphic/geologic character of the landscape (catchment) is such that all precipitation resides above about 2 m depth in the lithology sufficiently long to be potentially subject to ET processes, the Zhang et al (2001) algorithm works extremely well.

Some catchments are more porous however and a fraction of precipitation may penetrate to depths greater than ~2 m (to become groundwater) too rapidly to be subject to ET processes. In that case ET only 'works' on an 'effective' fraction of total precipitation.

Geoff: Yes, that sentence is incorrect. Perhaps I should have said that ... the rate and amount of water vapor ENTERING the air from the water surface is a function of the temperature of the air-water interface. Even over land there is a surprising amount of evaporation, provided the soil is moist or that there is a lot of vegetation. And all that evaporation keeps temperatures lower, so that you almost never see temperatures above 33 C over heavily vegetated areas, anywhere. But 40 C is common in the summer in dry areas, like West Texas, Eastern Oregon, Phoenix, etc.

jae,
Could you please be a bit more precise in the last sentence? Rain determines in part the amount of water in the air, but rain is not solely caused by the temperature at the water-air interface, especially if we are over land. Thanks Geoff.

It has always puzzled me how someone could posit that the addition of heat over an ocean would cause FEWER clouds. Additional heat evaporates more water in a system that is already near saturation (Clausius-Clapeyron relationship). My empirical data for moist areas show that the AVERAGE absolute humidity level at all common temperatures is 60-80% of saturation---and that the degree (%) of saturation INCREASES with temperature almost logarithmically. To me, this clearly shows that higher temperatures will cause a higher degree of saturation, which would tend to cause more cloudiness.

Maybe some of the problem is the view that the air "holds" water, when in fact, the amount of water in the air is determined only by the temperature at the water-air interface.