More learned about water — science still not settled

Scientists have long debated the impact on global climate of water evaporated from vegetation. New research from Carnegie’s Global Ecology department concludes that evaporated water helps cool the earth as a whole, not just the local area of evaporation, demonstrating that evaporation of water from trees and lakes could have a cooling effect on the entire atmosphere. These findings, published on 14 September in Environmental Research Letters, have major implications for land-use decision making.

The researchers even thought it was possible that evaporation could have a warming effect on global climate, because water vapour acts as a greenhouse gas in the atmosphere.

Using a climate model, they found that increased evaporation actually had an overall cooling effect on the global climate.

Increased evaporation tends to cause clouds to form low in the atmosphere, which act to reflect the sun’s warming rays back out into space. This has a cooling influence.

The only thing I understand about climate models is that they reflect our (human) understanding of the climate. The IPCC expresses our understanding of many climate processes as “poor”. That’s a good guide when considering the output of climate models, in my opinion.

But how different this is from the usual tale we hear from defenders of CAGW, that increased water vapour leads inevitably to increased warming. But there’s a sting in the tail of the lead author’s comments.

“This shows us that the evaporation of water from trees and lakes in urban parks, like New York’s Central Park, not only help keep our cities cool, but also helps keep the whole planet cool,” Caldeira said. “Our research also shows that we need to improve our understanding of how our daily activities can drive changes in both local and global climate. That steam coming out of your tea-kettle may be helping to cool the Earth, but that cooling influence will be overwhelmed if that water was boiled by burning gas or coal.”

Boil your water by approved means and there’ll be no effect on global temperature!

There must be some scientific reason for that, but we’ll just have to trust them.

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Richard C (NZ)

Richard T, great that you’ve opened up this avenue of investigation. You say:- But how different this is from the usual tale we hear from defenders of CAGW, that increased water vapour leads inevitably to increased warming This is exactly the problem I see with climate science, they just assume certain actions take place without finding out what other disciplines already know. Climate science assumes that DLR (down-welling long-wave radiation from clouds and GHG’s) “warms the earth” (geologic material including ocean) according to AGW and to NASA here:- High, thin clouds primarily transmit incoming solar radiation; at the same time, they trap some of the outgoing infrared radiation emitted by the Earth and radiate it back downward, thereby warming the surface of the Earth That action they say causes increased evaporation, increased water vapour and increased warming. I’ve yet to find a peer-reviewed paper that actually measures ocean evaporation by DLR (could be done by experiment in a lab) by I have come across 2 papers that investigate evaporation from forest and willows, one paper being from our own NZ Forest Research Institute (FRI). I’ve documented this here at CCG but it bears… Read more »

Richard C (NZ)

From the EurekAlert article (linked in the post):-

Evaporative cooling is the process by which a local area is cooled by the energy used in the evaporation process

What Pierce, Rowe and Stewart along with Iritz and Landroth indicate is that “the energy used” is NOT radiative energy (it’s a “minor influence” only).

Richard C (NZ)

From the EurekAlert article (linked in the post):-

Increased evaporation tends to cause clouds to form low in the atmosphere, which act to reflect the sun’s warming rays back out into space. This has a cooling influence.

From what I can gather so far, this supports Spencer-Braswell 2011 but is contrary to Dessler 2011.

Also at odds with Trenberth because according to him “clouds don’t cause climate change”

Might be a bit wrong here – have to think about it some more.

Richard C (NZ)

The Carnegie Institution for Science, Department of Global Ecology study focuses on LOW cloud but the Spencer – Braswell vs Dessler – Trenberth argument is about the NETT effect of all clouds. The argument however is being couched in warmist terms by Team cheerleaders i.e in a “warming world” blah-de-blah, see this Live Science article: Clouds: The Wild Card of Climate Change”:- “Currently, all of the Earth’s clouds exert a net cooling effect on our planet. But the substantial and opposing influences of clouds begs the question: What will be the net effect of all of the Earth’s clouds on climate as the Earth continues to warm in the future? Will clouds accelerate warming or help offset, or dull, warming?” And, “Most scientists doubt that the net cooling effect of clouds will ever be large enough to completely offset ongoing warming. [What on-going warming? And “most scientists” – who cares?] But many scientists say that if warming were to increase cooling clouds or decrease warming clouds, the current net cooling effect of clouds on the Earth’s climate would probably increase. [The author (Lily Whiteman, National Science Foundation) omits the negative feedback loop here… Read more »

Richard C (NZ)

More from Live Science, this time by Stephanie Pappas, LiveScience Senior Writer:-

Within days of the editor’s resignation, Dessler published a study refuting Spencer’s claims in the journal Geophysical Research Letters.

“I said, ‘Let’s quantitatively measure how much energy the clouds are trapping and how much energy it takes to change the climate, and see if the clouds are trapping enough energy to change the climate,’” Dessler said. “The answer is, they’re not.”

[McIntyre (using Dessler’s data) says implicitly, they are]

The changes Spencer saw in his model are explained by El Niño/La Niña cycles, Dessler said, not caused by clouds.

The El Niño/La Niña cycles seem to be a point-of-difference for the Team but I can’t yet get my head around how this fits into the controversy given the deficiency in Dessler’s paper (lag vs instantaneous CLD forcing – temperature relationship).

Richard C (NZ)

The El Niño/La Niña point-of-difference. Spencer responds to this:- The changes Spencer saw in his model are explained by El Niño/La Niña cycles, Dessler said, not caused by clouds. With this:- In his paper, Dessler dismissed all of the evidence we presented with a single claim: that since (1) the global temperature variations which occurred during the satellite record (2000-2010) were mostly caused by El Nino and La Nina, and (2) no one has ever demonstrated that “clouds cause El Nino”, then there could not be a clouds-causing-temperature-change contamination of his cloud feedback estimate. But we now have clear evidence that El Nino and La Nina temperature variations are indeed caused in large measure by changes in clouds, with the cloud changes coming months in advance of the temperature changes. And this:- At the heart of this debate is whether cloud changes, through their ability to alter how much sunlight is allowed in to warm the Earth, can cause temperature change. We claim they can, and have demonstrated so with both phase space plots of observed temperature versus Earth radiative budget variations here [SB10], and with lag-regression plots of the same data… Read more »

Richard C (NZ)

Phase Shift in Spencer’s Data

Dr David Stockwell

The LW and SW_clr components lead the global surface temperature. There are three possible explanations:

1. Changes in cloud cover actually do drive changes in global temperature due to gamma-ray flux (GRF) or other effects, or

2. The changes in cloud cover are caused by changes in global temperature, with the derivative mechanism described above.

3. Both 1 and 2.

Spencer argues that it is impossible to distinguish between 1 and 2. Both Spencer and Lindzen both consider the lags important because correlation is greatly improved (and determines whether feedback is positive to negative). Neither seem to have mentioned the 3 month phase relationships emerging from integral/derivative system dynamics.

I can’t see how it is possible perform a valid analysis without this insight.

Richard C (NZ)

I’ve Looked at Clouds from Both Sides Now -and Before October 8th, 2011 by Roy W. Spencer, Ph. D. …sometimes, the most powerful evidence is right in front of your face….. I never dreamed that anyone would dispute the claim that cloud changes can cause “cloud radiative forcing” of the climate system, in addition to their role as responding to surface temperature changes (“cloud radiative feedback”). (NOTE: “Cloud radiative forcing” traditionally has multiple meanings. Caveat emptor.) But that’s exactly what has happened. Andy Dessler’s 2010 and 2011 papers have claimed, both implicitly and explicitly, that in the context of climate, with very few exceptions, cloud changes must be the result of temperature change only. Shortly after we became aware of Andy’s latest paper, which finally appeared in GRL on October 1, I realized the most obvious and most powerful evidence of the existence of cloud radiative forcing was staring us in the face. We had actually alluded to this in our previous papers, but there are so many ways to approach the issue that it’s easy to get sidetracked by details, and forget about the Big Picture. Well, the following graph is the… Read more »


It seems that any effort to save the environment will collide with other development projects and above all urbanization. I was surprised when I found the other day that the drainage systems we all have in our gardens contribute a great deal to the way water circulates in the environment and that their design may have a damaging impact upon the eco-friendliness of our homes’ exteriors.

Richard C (NZ)

New paper shows clouds have a large negative-feedback cooling effect A paper published last week in the journal Meteorological Applications undermines a key assumption of the theory of man-made global warming, finding that the cooling effect of clouds far outweighs a supposed ‘greenhouse’ warming effect. Alarmists claim clouds have an overall ‘positive-feedback’ warming effect upon climate due to ‘back-radiation’ of the ‘greenhouse’ gas water vapor. This new paper based on satellite measurements finds instead that clouds have a large net cooling effect by blocking solar radiation and increasing radiative cooling outside the tropics. The cooling effect is found to be -21 Watts per meter squared, more than 17 times the supposed warming effect from a doubling of CO2 concentrations [1.2 W/m2]. Another key assumption of the AGW theory topples in the face of real-world data showing the net feedback from clouds is strongly negative. Combining satellite data and models to estimate cloud radiative effect at the surface and in the atmosphere Richard P. Allan, 2011 Abstract: Satellite measurements and numerical forecast model reanalysis data are used to compute an updated estimate of the cloud radiative effect on the global multi-annual mean radiative energy… Read more »

Richard C (NZ)

Multi-institutional study group finds strong negative-feedback cooling effect from clouds The Newsletter of the multi-institution Climate Process Team on Low-Latitude Cloud Feedbacks on Climate Sensitivity outlines their significant findings to date: 1. Clouds have a strong negative-feedback cooling effect on climate in both the tropics and extra-tropics 2. A warmer climate enhances [increases] boundary layer clouds resulting in increasing negative-feedback 3. Due to this strong negative-feedback, global climate sensitivity is only 0.41 K/(W m-2) – HALF the 0.8 K/(W/m2) + assumed by the IPCC Introduction: The Climate Process Team on Low-Latitude Cloud Feedbacks on Climate Sensitivity (cloud CPT) includes three climate modeling centers, NCAR, GFDL, and NASA’s Global Modeling and Assimilation Office (GMAO), together with 8 funded external core PIs led by Chris Bretherton of the University of Washington (UW). Its goal has been to reduce uncertainties about the feedback of low-latitude clouds on climate change as simulated in atmospheric general circulation models (GCMs). To coordinate this multi-institution effort, we have hired liaison scientists at NCAR and GFDL, had regular teleconferences and annual meetings, and developed special model output datasets for group analysis. The cloud CPT web site provides links to all… Read more »

Richard C (NZ)

Watts:- “Oh dear, now we have three peer reviewed papers (Lindzen and Choi, Spencer and Braswell, and now Richard P. Allan) based on observations that show a net negative feedback for clouds, and a strong one at that. What will Trenberth and Dessler do next? Maybe the editor of Meteorological Applications can be persuaded to commit professional suicide and resign? The key paragraph from the new paper: …the cloud radiative cooling effect through reflection of short wave radiation is found to dominate over the long wave heating effect, resulting in a net cooling of the climate system of −21 Wm−2. After all the wailing and gnashing of teeth over the Spencer and Braswell paper in Remote Sensing, and the stunt pulled by its former editor who resigned saying the peer review process failed, another paper was published last week in the journal Meteorological Applications that agrees well with Spencer and Braswell. This new paper by Richard P. Allan of the University of Reading discovers via a combination of satellite observations and models that the cooling effect of clouds far outweighs the long-wave or “greenhouse” warming effect. While Dessler and Trenberth (among others) claim… Read more »

Richard C (NZ)

Alan Siddons on the negative-feedback cooling effect of clouds email from Alan Siddons: Someone asked me today to comment on the recent Richard P Allan paper, which is discussed on WUWT [and originally posted on The Hockey Schtick]. Allan’s finding is that clouds have a negative influence on the earth’s temperature (duh). But here is what wrote back. Hope you like it. Alan ————————————————————————————— Anthony Watts offers an important statement about the Allan paper: While Dessler and Trenberth (among others) claim clouds have an overall positive feedback warming effect upon climate due to the long-wave back-radiation, this new paper shows that clouds have a large net cooling effect by blocking incoming solar radiation and increasing radiative cooling outside the tropics. Now, I always focus on the basic claim that back-radiating greenhouse gases make the earth’s surface warmer. The earth’s SURFACE. Liquid clouds are often included as greenhouse agents because at nighttime they’re thought to reflect heat rays back to the earth and at least retard surface cooling if not actually raise the temperature. In other words, the same heating mechanism, that of back-radiation, is attributed to clouds because ‘radiative forcing’ theory assumes that… Read more »

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