by Craig and Sherwood Idso
Special Issue
This week we announce the release of our newest major report, Carbon Dioxide and Earth’s Future: Pursuing the Prudent Path. Based on the voluminous periodic reports of the Intergovernmental Panel on Climate Change (IPCC), the ongoing rise in the atmosphere’s CO2 concentration has come to be viewed as a monumental danger — not only to human society, but to the world of nature as well. But are the horrific “doomsday scenarios” promulgated by the climate alarmists as set-in-stone as the public is led to believe? Do we really know all of the complex and interacting processes that should be included in the models upon which these scenarios are based? And can we properly reduce those processes into manageable computer code so as to produce reliable forecasts 50 or 100 years into the future? At present, the only way to properly answer these questions is to compare climate model projections with real-world observations. Theory is one thing, but empirical reality is quite another. The former may or may not be correct, but the latter is always right. As such, the only truly objective method to evaluate climate model projections is by comparing them with real-world data.
In what follows, we conduct just such an appraisal, comparing against real-world observations ten of the more ominous model-based predictions of what will occur in response to continued business-as-usual anthropogenic CO2 emissions: (1) unprecedented warming of the planet, (2) more frequent and severe floods and droughts, (3) more numerous and stronger hurricanes, (4) dangerous sea level rise, (5) more frequent and severe storms, (6) increased human mortality, (7) widespread plant and animal extinctions, (8) declining vegetative productivity, (9) deadly coral bleaching, and (10) a decimation of the planet’s marine life due to ocean acidification. And in conjunction with these analyses, we proffer our view of what the future may hold with respect to the climatic and biological consequences of the ongoing rise in the air’s CO2 content, concluding by providing an assessment of what we feel should be done about the situation.
Click on the links below to read the report, or download the full report in a pdf file (2.5 mb in size) below.
Carbon Dioxide and Earth’s Future: Pursuing the Prudent Path
1. Unprecedented Warming of the Planet
2. More Frequent and Severe Floods and Droughts
3. More Frequent and Severe Hurricanes
4. Rising Sea Levels Inundating Coastal Lowlands
5. More Frequent and Severe Storms
7. Widespread Plant and Animal Extinctions
8. Declining Vegetative Productivity
10. Marine Life Dissolving Away in Acidified Oceans
Executive Summary
As presently constituted, earth’s atmosphere contains just slightly less than 400 ppm of the colorless and odorless gas we call carbon dioxide or CO2. That’s only four-hundredths of one percent. Consequently, even if the air’s CO2 concentration was tripled, carbon dioxide would still comprise only a little over one tenth of one percent of the air we breathe, which is far less than what wafted through earth’s atmosphere eons ago, when the planet was a virtual garden place. Nevertheless, a small increase in this minuscule amount of CO2 is frequently predicted to produce a suite of dire environmental consequences, including dangerous global warming, catastrophic sea level rise, reduced agricultural output, and the destruction of many natural ecosystems, as well as dramatic increases in extreme weather phenomena, such as droughts, floods and hurricanes.
As strange as it may seem, these frightening future scenarios are derived from a single source of information: the ever-evolving computer-driven climate models that presume to reduce the important physical, chemical and biological processes that combine to determine the state of earth’s climate into a set of mathematical equations out of which their forecasts are produced. But do we really know what all of those complex and interacting processes are? And even if we did — which we don’t — could we correctly reduce them into manageable computer code so as to produce reliable forecasts 50 or 100 years into the future?
Some people answer these questions in the affirmative. However, as may be seen in the body of this report, real-world observations fail to confirm essentially all of the alarming predictions of significant increases in the frequency and severity of droughts, floods and hurricanes that climate models suggest should occur in response to a global warming of the magnitude that was experienced by the earth over the past two centuries as it gradually recovered from the much-lower-than-present temperatures characteristic of the depths of the Little Ice Age. And other observations have shown that the rising atmospheric CO2 concentrations associated with the development of the Industrial Revolution have actually been good for the planet, as they have significantly enhanced the plant productivity and vegetative water use efficiency of earth’s natural and agro-ecosystems, leading to a significant “greening of the earth.”
In the pages that follow, we present this oft-neglected evidence via a review of the pertinent scientific literature. In the case of the biospheric benefits of atmospheric CO2 enrichment, we find that with more CO2 in the air, plants grow bigger and better in almost every conceivable way, and that they do it more efficiently, with respect to their utilization of valuable natural resources, and more effectively, in the face of environmental constraints. And when plants benefit, so do all of the animals and people that depend upon them for their sustenance.
Likewise, in the case of climate model inadequacies, we reveal their many shortcomings via a comparison of their “doom and gloom” predictions with real-world observations. And this exercise reveals that even though the world has warmed substantially over the past century or more — at a rate that is claimed by many to have been unprecedented over the past one to two millennia — this report demonstrates that none of the environmental catastrophes that are predicted by climate alarmists to be produced by such a warming has ever come to pass. And this fact — that there have been no significant increases in either the frequency or severity of droughts, floods or hurricanes over the past two centuries or more of global warming — poses an important question. What should be easier to predict: the effects of global warming on extreme weather events or the effects of elevated atmospheric CO2 concentrations on global temperature? The first part of this question should, in principle, be answerable; for it is well defined in terms of the small number of known factors likely to play a role in linking the independent variable (global warming) with the specified weather phenomena (droughts, floods and hurricanes). The latter part of the question, on the other hand, is ill-defined and possibly even unanswerable; for there are many factors — physical, chemical and biological — that could well be involved in linking CO2 (or causing it not to be linked) to global temperature.
If, then, today’s climate models cannot correctly predict what should be relatively easy for them to correctly predict (the effect of global warming on extreme weather events), why should we believe what they say about something infinitely more complex (the effect of a rise in the air’s CO2 content on mean global air temperature)? Clearly, we should pay the models no heed in the matter of future climate — especially in terms of predictions based on the behavior of a non-meteorological parameter (CO2) — until they can reproduce the climate of the past, based on the behavior of one of the most basic of all true meteorological parameters (temperature). And even if the models eventually solve this part of the problem, we should still reserve judgment on their forecasts of global warming; for there will yet be a vast gulf between where they will be at that time and where they will have to go to be able to meet the much greater challenge to which they aspire.
Idso – CO2 and Earth’s Future 1-31-11 (PDF 2.5MB)
h/t to Bob Feguson, SPPI
eadler says:
February 3, 2011 at 4:49 am
“The executive summary of the Idso’s book shows how flawed the thinking is.”
Well said!
I agree 100% with you.
But to prevent Anthony complaint, a few links to peer reviewed studies as I have done would be useful.
Khwarizmi,
Peru [AKA: “Mars” in other threads] needs to get a life, too. His On/Off switch is permanently wired around, and there’s no turning him off or getting a straight answer from him. Here’s a question I’ve repeatedly asked him, that he’s never answered:
“Show us where the increase in CO2 has caused any global harm. Be explicit, and avoid models, conjecture, and throwing CO2 in with other causes. Show the actual damage, and show convincingly that any putative harm is due specifically to CO2. Above all, avoid any argumentum ad ignorantium fallacies” [which is what the alarmist crowd thrives on].
All Peru does is throw up links from Un-Skeptical Science, fakeclimate, climateregress, and similar echo chambers inhabited by true believers. He can’t think for himself, because he gives links to pal-reviewed “studies” that were hand-waved through the corrupt climate peer review system, and that are never almost read.
Fair warning: Peru is indistinguishable from a ‘bot. Makes eadler look normal. Peru is the poster boy for incurable cognitive dissonance. Word up, Khwarizmi.☺
SMOKEY:
I have answered you in other treads countless times, showing, with links to peer-reviewed paleoclimate studies, observations of sea level rise, ice sheet meltdown and greenhouse signatures such as stratospheric cooling, not to mention the studies about ocean acidification, the harm that excess CO2 is doing to the planet.
And I will continue to do so, mainly not because I want to convert you from your your cognitive dissonance (that makes you make a pathetic projection of yourself on me and other free-thinking people), but because other people that (unlike you) are not extremists but confused by the so-called “skeptic” arguments can found information that reveals the true state of the planet and society.
And stop saying things like:
“All Peru does is throw up links from Un-Skeptical Science, fakeclimate, climateregress, and similar echo chambers inhabited by true believers.”
I posted links to peer-reviewed studies, not to the sites (realclimate, skeptical science, climateprogress,etc) you are saying I am linking. Readers can search here at WUWT if I do so.
By the way, those “true believer” sites also base their conclusion on that peer-reviewed studies, but those are second-hand sources and I think is better to link to the first-hand information, that is, studies and data.
“He can’t think for himself,”
Like you?
“because he gives links to pal-reviewed “studies” that were hand-waved through the corrupt climate peer review system, and that are never almost read.”
So you claim that the entire scientific community is corrupted and all data is fabricated?
And we should instead believe in people like you, that cannot even tell the difference between regional and global climate change (like you about recent Greenland warming)?
Well, I was just letting Khwarizmi know about Mr Mars. But speak of the devil and he appears.
Ho hum. I note that as always, Peru can’t answer my question:
Show us where the increase in CO2 has caused any global harm. Be explicit, and avoid models, conjecture, and throwing CO2 in with other causes. Show the actual damage, and show convincingly that any putative harm is due specifically to CO2. Above all, avoid any argumentum ad ignorantium fallacies.
For true believers, facts are not required. Faith is enough.
Smokey says:
February 3, 2011 at 12:59 pm
“Well, I was just letting Khwarizmi know about Mr Mars. But speak of the devil and he appears.
Ho hum. I note that as always, Peru can’t answer my question:
Show us where the increase in CO2 has caused any global harm. Be explicit, and avoid models, conjecture, and throwing CO2 in with other causes. Show the actual damage, and show convincingly that any putative harm is due specifically to CO2. Above all, avoid any argumentum ad ignorantium fallacies.
For true believers, facts are not required. Faith is enough.”
Your question is itself nonsense, and seems to show ignorance of science.
What do you mean by “global harm”? Does this mean that harm must extend across the entire globe?
How do you determine that an invisible gas is doing harm without a model of what is happening? It is impossible. All science is based on models.
CO2’s harm is entirely indirect, and it works through modification of mechanisms which are naturally existing. Your question seems to disallow showing how CO2 acts in this way.
Also there is a difference between arguing from ignorance and a using a process of elimination to help determine the cause of an effect. The latter is a legitimate form of argument.
Based on your interest in the subject, it seems that you must have been exposed to the mainstream science which explains how CO2 is warming the globe. Based on your question, it appears you have found a flawed rationale which enables you to ignore the findings of main stream science, so you don’t have to discuss the results of this research.
It is very similar to the arguments put forward by the Idso’s in their executive summary.
eadler says:
“What do you mean by ‘global harm’? Does this mean that harm must extend across the entire globe?”
Exactly. That is the CO2=CAGW conjecture.
Supply evidence of global harm, or admit that CO2 is harmless.
Evidence of global harm due to greenhouse gases (mainly CO2):
Arctic sea ice area:
http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1177
(see fig 3: observations vs. models)
Arctic sea ice volume:
http://www.accuweather.com/blogs/climatechange/story/44710/the-decline-of-arctic-sea-ice.asp
http://upload.wikimedia.org/wikipedia/commons/thumb/5/51/Plot_arctic_sea_ice_volume.svg/1000px-Plot_arctic_sea_ice_volume.svg.png
Greenland melting:
http://www.arctic.noaa.gov/reportcard/greenland.html
Greenland plus antartica (accelerating melting)
http://thingsbreak.files.wordpress.com/2009/10/increasing-rates-of-ice-mass-loss-from-the-greenland-and-antarctic-ice-sheets-revealed-by-grace.pdf
http://thingsbreak.files.wordpress.com/2009/09/extensive-dynamic-thinning-on-the-margins-of-the-greenland-and-antarctic-ice-sheets.pdf
Extensive glacier meltdown worldwide:
http://www.igsoc.org/annals/50/50/a50a018.pdf
http://nsidc.org/sotc/glacier_balance.html
Sea level rise closely tracking IPCC worst case scenario:
http://www.pik-potsdam.de/~stefan/Publications/Nature/rahmstorf_etal_science_2007.pdf
Consecuence of warm sea surface temperatures in the tropical Atlantic (extreme Amazon drought):
http://mudancasclimaticas.cptec.inpe.br/~rmclima/pdfs/publicacoes/2008/Marengoetal2008.pdf
Aragonite undersaturation in the Arctic Ocean (a consecuence of ocean acidification + sea ice melt):
http://www.whoi.edu/beaufortgyre/pdfs/yamamoto-kawai_aragonite_science2009.pdf
This is only a little collection of climate change + ocean acidification impacts. Now I go to sleep (is 2
From Peru : You wasted your time putting together all those links, because what we were looking for was a global effect caused by CO2. Your links simply show that the planet warmed recently – the sort of thing it does due to natural forces.
Worse, you have shot yourself in the foot, because the first link, and the chart you draw attention to, show that the actual measurements bear no resemblance whatsoever to the climate models. The article itself even says “Climate models have done a poor job predicting the recent record loss of arctic sea ice (Figure 3). None of the models used to formulate the official word on climate, the 2007 United Nations IPCC report, foresaw the shocking drop of 2007-2008.“.
In other words, what you are looking at – the loss of ice – was, as far as the climate models can tell, not caused by CO2.
Peru says: [ … ]
Mike Jonas is right. Peru’s regional citations are easy to debunk, because they show no global harm caused by the rise in a harmless and beneficial minor trace gas. And despite what eadler claims, the very small 0.7° rise over the past century is not harmful, it is beneficial. Only a deluded alarmist would believe that a little extra natural warmth is a bad thing.
Deconstructing Peru’s failed attempts to show global damage from CO2:
#1 – 6: FALSE. The Arctic, and Greenland, etc. are specific regions. They are not global, and they were cherry-picked to avoid the Antarctic. The Antarctic ice cover is growing, therefore global CO2 rise can not be the cause. QED
Glaciers melting: FALSE. Many glaciers are growing, falsifying the conjecture that CO2 is causing glacier retreat. Global CO2 does not cherry-pick glaciers.
Sea Level rise accelerating. FALSE. The rise in sea level – an effect of the planet’s emergence from the LIA – is slowing. This is an indisputable fact, and it debunks a major claim of the increasingly desperate CO2=CAGW crowd. Also, ocean heat content is falling while harmless, beneficial CO2 rises.
SST is completely normal. Claiming it shows global damage is FALSE. Again, cherry-picking limited regions like the Amazon and the tropical Atlantic shows no global harm. They are routine natural fluctuations as shown in the link, which verify the null hypothesis. These natural fluctuations have all happened repeatedly in the past, prior to the industrial revolution and throughout the Holocene.
The latest wild-eyed shreik from the CAGW crowd is over the claim of “ocean acidification.” It has no basis in fact, since the oceans have essentially unlimited buffering capacity; they can never become acidic. The entire “acidification” scare, including the aragonite scare, was debunked here.
Nothing posted by Peru shows global harm from CO2. Nothing. Thus, the alternative hypothesis [CO2=CAGW] fails against the null hypothesis. There is nothing out of the ordinary happening. It is all within the limits of natural climate variability. Any putative warming from CO2 is too small and insignificant to measure, and is therefore inconsequential.
Smokey says:
February 4, 2011 at 12:49 am
Here I deconstruct the Smokey response to my my examples:
“#1 – 6: FALSE. The Arctic, and Greenland, etc. are specific regions. They are not global, and they were cherry-picked to avoid the Antarctic. Antarctic ice cover is growing, therefore global CO2 rise can not be the cause. QED”
There is a slight increase in wintertime SEA ice cover in the Antarctic Ocean, that was predicted as a consecuence of a warming Antarctic Ocean. But the Antarctic Ice Sheet is NOT growing, instead is melting at an accelerating speed, as I shown before:
“Greenland plus antartica (accelerating melting)
http://thingsbreak.files.wordpress.com/2009/10/increasing-rates-of-ice-mass-loss-from-the-greenland-and-antarctic-ice-sheets-revealed-by-grace.pdf
http://thingsbreak.files.wordpress.com/2009/09/extensive-dynamic-thinning-on-the-margins-of-the-greenland-and-antarctic-ice-sheets.pdf ”
“Glaciers melting: FALSE. Many glaciers are growing, falsifying the conjecture that CO2 is causing glacier retreat. Global CO2 does not cherry-pick glaciers.”
You don’t show in the link absolutely nothing showing that glaciers are not melting. You only showed a link about the melting history of the Jacobshavn Glacier.
“Sea Level rise accelerating. FALSE.”
I did not claim that SLR is accelerating. I only showed that the near constant rate of sea level rise is tracking the worst case scenario of the IPCC models.
“The rise in sea level – an effect of the planet’s emergence from the LIA – is slowing. This is an indisputable fact, and it debunks a major claim of the increasingly desperate CO2=CAGW crowd.”
There is an apparent slowdown only in the Universisty of Colorado data. In the CSIRO and AVISO data not:
http://www.cmar.csiro.au/sealevel/sl_hist_last_15.html
http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/
Even in the University of Colorado data, what is shown is a near constant rate of sea level rise, interrupted by a pause during the 2007-2008 La Niña (and after it a return to the previous rate of SLR):
http://sealevel.colorado.edu/current/sl_ib_ns_global.jpg
“Also, ocean heat content is falling while harmless, beneficial CO2 rises”
Not according to the best study about it, that track ocean heat down to 2000 meters:
Global hydrographic variability patterns during 2003–2008
http://archimer.ifremer.fr/doc/2009/publication-6802.pdf
That shows a near constant rate of warming of 0.77 +/- 0.11 W/m^2
“SST is completely normal. Claiming they show global damage is FALSE. Again, cherry-picking limited regions like the Amazon and the tropical Atlantic shows no global harm.”
Well, only if you ignore the drought in the Amazon, the massive coral bleaching in Tropical Atlantic, the Indian Ocean and the West Pacific, the warm water induced melting of the the Greenland and West Antarctic ice sheets, the extreme precipitation events when sea surface temperatures are at record or near record levels resulting in a massive liberation of water vapor (just as an example you have the Queensland Floods, the Brazilian Floods, the Pakistan floods, etc), the very active hurricane seasons that result from very warm sea surface temperatures (like the 2005 and 2010 Atlantic hurricane seasons and the 2010-2011 Australian hurricane season), etc.
“The latest wild-eyed shreik from the CAGW crowd is over the claim of “ocean acidification.” It has no basis in fact, since the oceans have essentially unlimited buffering capacity; they can never become acidic”
Unlimited buffering capacity?? From what parallel universe you come from? What you are saying violate the laws of physics and chemistry. And as an empirical example, where was the “unlimited buffering capacity” when 2 years ago the Arctic become aragonite undersaturated? Was taking a vacation on skepticland??
Mr Smokey, I challenge you to answer to the data and studies any data or studies that refutes the data and studies I posted. You have not done that for months.
And please, formulate what your “null hypothesis” is. A null hypothesis in statistics is a statement that some variables are not related. What are your variables that you claim are not related?
Peru obviously either didn’t read the entire Idsos’ article, or he failed to understand that Drs Idso have completely debunked the CO2=CAGW conjecture. Peru also fails to understand the concept of the null hypothesis, which is simply a function of the scientific method – something alarmists continually ignore and carefully avoid.
Being unable to grasp the concept, Peru can not understand why it must be that if the null remains unfalsified, then any alternative hypothesis that shows no measurable global difference from the null, such as CO2=CAGW, must necessarily fail.
The null hypothesis is the statistical hypothesis which states that there are no differences between observed and expected data. And we find that in fact, there are no differences between the climate during the Holocene and the current climate; none. What is happening now has happened repeatedly in the past. In fact, the current climate is especially benign compared with the extremes of the Holocene – when CO2 was quite low.
The purpose of the null is to test whether the alternative hypothesis shows any measurable difference between the two. As I’ve repeatedly shown, there is no quantifiable global difference between the alternative CO2=CAGW hypothesis and the null hypothesis. Therefore, the alternative hypothesis fails, and is reduced to a falsified conjecture. QED
As Dr Roy Spencer notes, no one has falsified the hypothesis that the observed temperature changes are a consequence of natural variability. IMHO, Dr Spencer has forgotten more than Peru will ever learn about the subject. So I’ll accept Dr Spencer’s conclusion over Peru’s repeatedly falsified conjectures and cherry-picked regional examples of natural climate variability.
Peru wastes much time and effort furiously typing links that go un-read, convinced against all the evidence that a minor trace gas controls the climate.
As if.
We could be in the depths of the next major Ice Age, and Peru would still be claiming with wild-eyed certainty that CO2 will cause runaway global warming. Cognitive dissonance in action. The null hypothesis proves that in current and projected concentrations, CO2 is a harmless and beneficial trace gas.
Mr Smokey:
Finally you have stated what your “null hypothesis” is. To be scientific, you should have been explicit since the beginning. Science is about hypothesis and evidences, and the hypothesis must be formulated explicitly, not using vague terms such as “the” null hypothesis. There can be dozens of different null hypotheses depending on what aspect on a system as complex as climate you focus.
So:
“As Dr Roy Spencer notes, no one has falsified the hypothesis that the observed temperature changes are a consequence of natural variability”
The “null hypothesis” is that current climate change is just the result of natural variability. We will test this focusing in the main drivers of natutal variability:
1)Milanktovich cycles: these are 3 astronomical cycles:
-eccentricity: the period is 100 000 years between more circular and more elliptic orbits of the earth around the sun
-obliquity: the period is 41 000 years between a more tilted (24º) and less tilted (24º)earth axis of rotation
-precession: is caused mainly by the “rotation” in the direction of the earth axis with respect to the “fixed” stars.It last approximately 22 000 years.
The combination of theses cycles does not alter global Earth insolation , but affects strongly regional (masinly more or less insolation in the polar regions) and seasonal insolation(seasons less or more extreme). When the polar insolation is bigger and the seasons are more extreme, ice sheets melts as a response to warmer summers. When polar insolation drops and seasons are more mild, ice build up in the poles mainly because less snow and ice melts in the summer, allowing ice to build up year after year.
Could this be driving modern polar warming?
Well, see fig 1 here:
Palaeoclimatic insights into future climate challenges
http://rsta.royalsocietypublishing.org/content/361/1810/1831.full.pdf
Well there is a significant correlation between high lkatitude insolation and polar temperature IN THE PAST, but high latitude insolation in both hemispheres is dropping, specially in the Northern Hemisphere were modern warming is more strong.
This is confirmed by this paper:
Recent Warming Reverses Long-Term Arctic Cooling (Kaufman et al.)
http://www.see.ed.ac.uk/~shs/Climate%20change/Data%20sources/Kaufman%20Schneider%20recent%20warming.pdf
Data can be found here:
http://www.ncdc.noaa.gov/paleo/pubs/kaufman2009/kaufman2009.html
In short a series of proxies (mainly lake sediments, but also ice cores and some tree rings) show a long term cooling in the Arctic of –0.22°C +/- 0.06°C per 1000 years, just as expected from declining summer insolation, until the 20th century, when a relatively rapid warming erased 2000 years of cooling.
Result: the null hypothesis 1, astronomical cycles, is falsified. We should be cooling as a consecuence of Milancktovich cycles, in effect, other reconstructions show that the maximum holocene temperatures occurred at the time of maximum insolation in Northern Hemisphere between 6000 and 10 000 years ago, during the Holocene Thermal Maximum (HTM).
See here:
Holocene thermal maximum in the western Arctic (0–180W)
http://esp.cr.usgs.gov/research/alaska/PDF/KaufmanAger2004QSR.pdf
Peru, you were doing fine until you claimed the null hypothesis is falsified. It isn’t, of course, and your erroneous conclusion probably comes from misunderstanding the concept of the null. I’ve explicitly stated the same definition of the null hypothesis at least a half-dozen times. The definition applies to all null hypotheses.
You said:
“Climate change, manmade or natural, does not occur spontaneously. It occurs because there is an extrnal forcing in the Climate System.”
That is incorrect. External forcings are not necessary. The need for a forcing agent is one of the central misunderstandings of the climate alarmist crew. Prof Richard Lindzen explains:
What we currently observe are only very small changes, on the order of tenths of a degree, over more than a century. Specifically, ≈0.7°C.
That is a very minor cyclical rise. During the last ten millennia temperatures have often risen and fallen by more than 10°C, on decadal time scales – when CO2 levels were very low. The current warming cycle is insignificant and beneficial in comparison.
No extraneous entities such as CO2 are necessary to explain the minor changes that are always occurring. CO2 may have a minor effect, but it is too small to actually measure. Most of the current *mild* warming cycle is due to natural variability.
The preposterous 3°C sensitivity claimed by the IPCC/Hansen contingent is based on evidence-free belief based on erroneous model assumptions. If climate sensitivity to CO2X2 were 3°, global temperatures would closely track changes in CO2. They demonstrably do not, indicating that the sensitivity number is at most ≈one-third of what is claimed by the UN/IPCC.
My comment was only part 1.
Now part 2: other external forcings in addition to greenhouse gases and Milanktovich cycles:
2)The Sun: this one of the widepsread “skeptic” arguments, blaming recent warming on the Sun. Let’s see:
http://solarscience.msfc.nasa.gov/images/bfly.gif
Hmm. Certainly solar activity increased in the firt half of the 20th century, increasing steadily from the depths of the Maunder Minimum in the 1600-1700 and the Dalton Minimum in early 1800s, so it can explain part of the warming between 1800s and mid 1900s. Indeed low solar activity in the 1600 sto 1800s is main hypothesis that explains the origins of the Little Ice Age.
BUT solar activity peaked in the 1950s, and then bagan a slow decline. Certainly solar activity CANNOT be the cause of modern (post 1970s) warming. To close, the warmest decade on record, the 2000s, occurred after solar cycle 23 (the weaker since solar cycle 20 in the 1970s) that was followed by the deepest solar minimum in a century.
Result: null hypothesis 2, the sun caused recent warming, is falsified.
3) Volcanic activity: big volcanic eruption emit vast quantities of sulfate aerosols that reach the stratosphere, that can cool the planet for years. So a reduction in volcanic activity should cause warming (or more exactly less cooling). So how have volcanoes behaved?
http://www.ncdc.noaa.gov/paleo/pubs/crowley2000/crowley_fig3.pdf
In the recent times (second half of 20th century) there has been an increase in volcanic activity compared to mid century. So the first half of the 20th century warming can have been caused by a reduction in volcanic activity (together with increased solar activity) but again the effect in late 20th century sould be cooling, not warming.
Result: null hypothesis 3, reduced volcanic activity, is falsified.
Now finally there are the variations due to non-forced, internal variability.
There are mainly ocean cycles, like ENSO, PDO and AMO. Of these, ENSO is by far the most important. Could the Medieval Warm Period and Current Warm Period be the result of a series of significant El Niños and the Little Ice Age the result of a dominance of La Niñas?
Here enter the coral proxies. Here are some interesting papers:
El Niño-Southern Oscillation and tropical Pacific climate during the last millennium
http://eas8001.eas.gatech.edu/papers/Cobb_Nature_2003.pdf
And a nice PPT:
Fossil coral snapshots of ENSO and tropical Pacific climate over the late Holocene
http://shadow.eas.gatech.edu/~kcobb/cobb_iowa.pdf
Result:
During the Medieval Warm Period, the Pacific was dominated by LA NIÑA. The Pacific was in the COOL mode!
This is the main reason to call the Medieval Warm Period instead the Medieval Climate Anomaly, because while the North Atlantic basin was warm, the Tropical Pacific was cool.
And instead, the strongest ENSO activity with strong El Niños occurred in the 17th century, in the middle of the Little Ice Age.
The hypothesis that ENSO caused warming and cooling periods in the past (the MWP and the LIA), instead of external forcing is falsified. Indeed, some models can explain this counterintuitive fact by showing that the Tropical Pacific cools in response to increased insolation (like in the MWP) and warms in response to reduced insolation (like in the LIA or during a period of high volcanic activity).
In the late 20th century, there was an increased ENSO activity. An hypothesis is that high ENSO activity lead to warming, and reduced ENSO activity lead to cooling. This is the hypothesis of Bob Tisdale in the blog Climate Observations. An interesting hypothesis, but paleoclimate studies are inconsistent with it.
This data are strongly against the idea that unforced variation could explain current warming, because in the past the behave in the opposite way to explain global climate change.
All this leaves us with the alternative hypothesis: Greenhouse gases.
They have none of the problems shown above, and explain some facts that none of them can, like stratospheric cooling. Stratospheric cooling is predicted only by greenhouse gas forcing, while ocean cycles will not affect it and increased insolation wil cause stratospheric warming, not cooling.
Finally, greenhouse gases explain why (in the last 65 million years) the Earth was ice free for millions of years, and only in the middle to late Terciary ice ages began.
Trends, Rhythms, and Aberrations in Global Climate 65 Ma to Present
http://pangea.stanford.edu/research/Oceans/GES206/readings/Zachos2001.pdf
Without the influence of greenhouse gases, this cannot be explained.
The so-called “null hypothesis” fails completely to explain the past climate in the millions of years of our planet.
From Peru : Your analysis to date has shown that while Milankovitch cycles correspond with long term climate, and solar variability corresponds with events like the MWP and LIA, they do not correspond well with the last 40 years, yet the shorter-term ENSO cycle which does correspond extremely well with recent decades cannot be used to explain the long term climate.
You seem to be fixated on the idea that only one of the three can apply. Has it ever occurred to you that all three operate all the time?
Has it also ever occurrred to you that the computer models and the CO2 hypothesis cannot explain any of the climate cycles – certainly not the very long term where temperature and CO2 do not correlate at all; certainly not the MWP and LIA which the models cannot reproduce and for which CO2 is certainly no explanation; and certainly not recent decades in which there was cooling around the start of the 20th century (after the start of the industrial age) and again from the 1940s to 1970s (at a time of very rapid industrial expansion), while the period between these two periods of cooling gave us as rapid a warming as the last 30 years of the 20thC.
Even before you add in the lack of statistically significant warming over the last 15 years (Phil Jones) , the CO2 hypothesis has collapsed. (I will not flatter it by calling it a theory, since testing of it has been studiously avoided by its proponents).
The null theory (natural variability) is alive and well.
Mike Jonas says:
February 5, 2011 at 2:57 pm
“You seem to be fixated on the idea that only one of the three can apply [Milanktovich + solar+ ENSO, you understand me very well, thanks].
(…)
Has it ever occurred to you that all three operate all the time?”
Yes, of course. But ENSO acted against solar+volcanic forcing in the past, resulting in Pacific cooling during the Medieval Climate Anomaly and Pacific warming during the Little Ice Age. Some models suggest that increased insolation favors La Niña (Pacific cooling) and reduced insolation favors El Niños (Pacific warming).
In the laste 20th century, solar+volcanic forcing are both cooling forcings on the top on long term Milanktovich cooling forcing. ENSO may be blamed for recent warming, but the correlation breaks down in the past as I have shown before, so the hypothesis that El Niños cause long term warming is falsified by paleoclimate data. El Niños actually causes just short term warming (El Niño years are warmer, La Niña years are cooler).
“Has it also ever occurrred to you that the computer models and the CO2 hypothesis cannot explain any of the climate cycles”
Ocean cycles like ENSO and PDO are not the task of the climate models that simulate long term warming or cooling trens as a result of external forcings. In those models ENSO and the other ocean cycles are added as random variability. However, as I said above, NINO anomalies correlate inversely with insolation, and some models reproduced this.
“certainly not the very long term where temperature and CO2 do not correlate at all, certainly not the MWP and LIA which the models cannot reproduce and for which CO2 is certainly no explanation;”
Huh?
The LIA and MWP are predicted by climate models as a result of forcing (mainly solar+volcanic aerosols) see here:
http://www.ncdc.noaa.gov/paleo/pubs/crowley.html
A nice collection of graphs based on this study is here:
http://www.skepticalscience.com/Do-critics-of-the-hockey-stick-realise-what-theyre-arguing-for.html
(note that the skepticalscience article is based on the Thomas J. Crowley article data I liked just before)
“and certainly not recent decades in which there was cooling around the start of the 20th century (after the start of the industrial age) and again from the 1940s to 1970s (at a time of very rapid industrial expansion), while the period between these two periods of cooling gave us as rapid a warming as the last 30 years of the 20thC”
Indeed a there is a pretty good match between radiative forcing and global temperatures:
http://pubs.giss.nasa.gov/docs/2005/2005_Hansen_etal_1.pdf
(see fig 1)
There is a slight mismatch in the 1940s, when the Earth warmed more than expected from the models. This could have been caused by:
a)natural unforced variability: in effect there was a significant El Niño after 1940:
http://i33.tinypic.com/10miuxx.jpg (credit to Bob Tisdale for the plot)
b) Some forcings maybe are not well reconstructed. In particular, there could have been a drop in cooling sulfate emissions or an increase in warming black carbon emissions that were not included in the forcing reconstruction. The aerosol forcing (mainly sulfate + black carbon) is the forcing where the uncertainty in the reconstruction is higher. Greenhouse gases forcing near certain instead, because these gases have been carefully measured for decades.
“Even before you add in the lack of statistically significant warming over the last 15 years (Phil Jones),”
That fact is meaningless. The last 15 years show a warming trend with statistical significance barely below 95%, and that just show that for short time periods the noise of natural variability mask the overlying trend.
” the CO2 hypothesis has collapsed. (I will not flatter it by calling it a theory, since testing of it has been studiously avoided by its proponents)”
What has collapsed in all those decades of research is the hypothesis that climate can be explained without CO2 . The CO2 hypothesis is, as I have shown with detail in my previous posts, the only one that explains the history of past and present climate change. If you want a test for the CO2 influence on climate read my previous comments, that are only a small bit of the mountains of evidence accumulated in decades supporting it.
“The null theory (natural variability) is alive and well.”
As I have shown in my previous comments, this “null theory” a walking dead keep alive like a zombie by the so-called “skeptics”.
From Peru : “the hypothesis that El Niños cause long term warming is falsified by paleoclimate data”
My immediately previous post – the one you were replying to : “From Peru : Your analysis to date has shown that while Milankovitch cycles correspond with long term climate, and solar variability corresponds with events like the MWP and LIA, they do not correspond well with the last 40 years, yet the shorter-term ENSO cycle which does correspond extremely well with recent decades cannot be used to explain the long term climate.
You seem to be fixated on the idea that only one of the three can apply. Has it ever occurred to you that all three operate all the time?”
Maybe you didn’t notice, but I wasn’t disagreeing with your analysis of Milankovitch, solar variation and ENSO. I was, however, disagreeing with your idea that only one of the three can be responsible for all of our climate. Look at all three together, and climate cycles on all time scales start to make more sense. Of course, other natural factors need to be taken into account too. So, for example, when you say “the hypothesis that El Niños cause long term warming is falsified by paleoclimate data“, your statement seems entirely reasonable. (I don’t know for sure what the paleoclimate data shows, but I would certainly expect El Niños to have only a short term influence).
Now let’s look at the main paper you cited : Crowley “Causes of Climate Change Over the Past 1000 Years”.
http://www.ncdc.noaa.gov/paleo/pubs/crowley.html
Crowley purports to have done a model reconstruction of climate change over the last 1000 years, and to have shown that whereas the natural factors explained most of the temperature changes prior to the “late 20th century”, the warming of the late 20th century could only be explained by CO2. (I hope you wll agree that that is a fair summary). But the temperature history that he uses (figure 1) http://www.ncdc.noaa.gov/paleo/pubs/crowley2000/crowley_fig1.jpg shows a negligible MWP about 0.5 deg C cooler than today. Without a MWP cooler than today, he has no case.
Rather than have us cite opposing papers, I’ll quote what the AGW proponents had to say about the MWP, and what Dr David Deming had to say about them in a statement to congress:
Michael Mann to Phil Jones:
http://www.eastangliaemails.com/emails.php?eid=319&filename=1054736277.txt
“it would be nice to try to “contain” the putative “MWP”, even if we don’t yet have a hemispheric mean reconstruction available that far back“.
Jonathan Overpeck to Keith Briffa
http://www.eastangliaemails.com/emails.php?eid=742&filename=1158153059.txt
“I don’t think our team feels it is valid to say, as they did in TAR, that “It is also likely that, in the Northern Hemisphere,… 1998 was the warmest year” in the last 1000 years.“.
Edward Cook to Keith Briffa:
http://www.climate-gate.org/cru/mail/1052774789.txt
“Of course he [Bradley] and other members of the MBH camp [Michael Mann et al] have a fundamental dislike for the very concept of the MWP, so I tend to view their evaluations as starting out from a somewhat biased perspective“.
Keith Briffa to Edward Cook:
http://www.eastangliaemails.com/emails.php?eid=310
“Can I just say that I am not in the MBH camp – if that be characterized by an unshakable “belief” one way or the other , regarding the absolute magnitude of the global MWP.”
Dr David Deming to Congress:
http://epw.senate.gov/hearing_statements.cfm?id=266543
“I had another interesting experience around the time my paper in Science was published. I received an astonishing email from a major researcher in the area of climate change. He said, “We have to get rid of the Medieval Warm Period.””
The picture painted is one of scientific bias regarding the MWP, and the material above from Overpeck, Mann, Cook and Briffa has been certified as genuine.
Mike Jonas says:
February 6, 2011 at 11:09 am
“Maybe you didn’t notice, but I wasn’t disagreeing with your analysis of Milankovitch, solar variation and ENSO. I was, however, disagreeing with your idea that only one of the three can be responsible for all of our climate.”
Not worry, I undestand that you that one should consider all these factors togethener.
“Look at all three together, and climate cycles on all time scales start to make more sense”
I’m sorry, but this is not the case.
All the not-greenhouse external (natural) forcings have a cooling influlence in the last 50 years. Milanktovich cycles caused reduced high latitude insolation in the last millenia. The solar activity is slowly declining since the 1950s. Volcanic activity, after a pause in the early and mid 20th century, returned, causing episodes of cooling in the late 20th century (Mt Agung, El Chichon and Pinatubo).
Take all these together and we sould have been cooling in the late 20th century and early 21st century. But we are warming….
“So, for example, when you say “the hypothesis that El Niños cause long term warming is falsified by paleoclimate data“, your statement seems entirely reasonable. (I don’t know for sure what the paleoclimate data shows, but I would certainly expect El Niños to have only a short term influence).”
You get it. El Niño/La Niña doesn’t create heat, only redistribute it between the ocean and the atmosphere. So they have a strong short term influence, but the long term effect is negligible. The paleoclimate data I referred is this:
El Niño-Southern Oscillation and tropical Pacific climate during the last millennium
http://eas8001.eas.gatech.edu/papers/Cobb_Nature_2003.pdf
Fossil coral snapshots of ENSO and tropical Pacific climate over the late Holocene
http://shadow.eas.gatech.edu/~kcobb/cobb_iowa.pdf
That show that during the Medieval Climate Anomaly (aka Medieval Warm Period) the Pacific was dominated by La Niña cooling and during the Little Ice Age the Pacific was dominated by El Niño warming. Exactly the opposite you expect if warming episodes were caused by a series of strong El Niños and cooling episodes by a series of strong La Niñas.
Ocean cycles (the main source of non-forced, internal variability) then have a negligible long term effect, leaving us only with external forcings as drivers of climate. And all natural forcings have a cooling influence in the last 4o years. This leaves us only with antropogenic forcings as a cause of recent warming.
Then you said:
“Now let’s look at the main paper you cited : Crowley “Causes of Climate Change Over the Past 1000 Years”.
http://www.ncdc.noaa.gov/paleo/pubs/crowley.html
Crowley purports to have done a model reconstruction of climate change over the last 1000 years, and to have shown that whereas the natural factors explained most of the temperature changes prior to the “late 20th century”, the warming of the late 20th century could only be explained by CO2. ”
Yes, you get it.
“But the temperature history that he uses (figure 1) http://www.ncdc.noaa.gov/paleo/pubs/crowley2000/crowley_fig1.jpg
shows a negligible MWP about 0.5 deg C cooler than today. Without a MWP cooler than today, he has no case.”
This is not true. A MWP warmer than today imply that climate sensitivity is bigger than climate models assume. The MWP was caused by increased solar insolation (thanks to greater solar activity and lower volcanic activity). This forcing was however small compared to current greenhouse forcing, so it is expected that today temperatures are warmer than Medieval ones.
If this was not the case, it means that the climate is more sensitive to radiative forcing than current climate models assume. This in turn means that today warming is only a fraction of the warming that greenhouse gases already emitted will cause (more “warming in the pipeline”). And greenhouse gases will continue to grow, and will hit 1000 ppm by late 21st century if emission are not controlled.
In short, if the criticisms of the “hockey stick” are right, current antropogenic warming (and is antropogenic as I explained above) is worse than predicted.
A summary of this reasoning is here:
http://www.skepticalscience.com/Do-critics-of-the-hockey-stick-realise-what-theyre-arguing-for.html
(Note that I am not believing blindly in what skepticalscience or any other says. I check data and papers for myself. The reasoning, however, is straightforward, and pretty obvious)
From Peru : “All the not-greenhouse external (natural) forcings have a cooling influlence in the last 50 years. Milanktovich cycles caused reduced high latitude insolation in the last millenia. The solar activity is slowly declining since the 1950s. Volcanic activity, after a pause in the early and mid 20th century, returned, causing episodes of cooling in the late 20th century (Mt Agung, El Chichon and Pinatubo).
Take all these together and we sould have been cooling in the late 20th century and early 21st century. But we are warming….”
You left out ENSO.
From Peru : “A MWP warmer than today imply that climate sensitivity is bigger than climate models assume. The MWP was caused by increased solar insolation (thanks to greater solar activity and lower volcanic activity). This forcing was however small compared to current greenhouse forcing, so it is expected that today temperatures are warmer than Medieval ones.
If this was not the case, it means that the climate is more sensitive to radiative forcing than current climate models assume…..”
This touches on one of the fundamental errors in the IPCC Report. If you look at the way that they analyse solar variation, you will see that they allow only for the direct effect of the variation in solar irradiation. They do not allow for any possible feedbacks. On this basis, the effect of solar variation is relatively small.
Now, if you look at the way that they analyse CO2, you will see that the climate sensitivity is basically calculated by correlating the observed temperature changes with the level of atmospheric CO2, after deducting the (relatively small) effect of natural forcings such as solar variation. This gives them a climate sensitivity of around 3.
But the papers they use for the direct effect of CO2 – Schwartz etc and I think Hansen – put sensitivity at about 1.2. The difference between the value they need and the calculated 1.2 is assumed to be provided by feedbacks from water vapour and clouds.
IPCC Report AR4 8.6.2.3 : “Using feedback parameters from Figure 8.14, it can be estimated that in the presence of water vapour, lapse rate and surface albedo feedbacks, but in the absence of cloud feedbacks, current GCMs would predict a climate sensitivity (±1 standard deviation) of roughly 1.9°C ± 0.15°C (ignoring spread from radiative forcing differences). The mean and standard deviation of climate sensitivity estimates derived from current GCMs are larger (3.2°C ± 0.7°C) essentially because the GCMs all predict a positive cloud feedback (Figure 8.14) but strongly disagree on its magnitude.”
There are a number of problems with this. To my mind, the main two are:
1. They have no mechanism for clouds. They have simply manipulated numbers in the models until they can get what appears to be a reasonable match. The fact that there is so much disagreement between models also suggests that they might be on the wrong track. A natural expectation is that increased water vapour would lead to more clouds, which would be more likely to cool than to warm – in other words, cloud feedback is likely to be negative. Instead, they put in a high positive figure for cloud feedback – note that it supposedly delivers more warming than the CO2 itself does.
2. They have not considered the possibility that solar variation could itself have feedbacks. By contrast, they have happily assumed a clouds feedback for CO2-induced warming, in the absence of any mechanism or of any evidence from observations of the real world. [I should also note that the feedbacks to CO2 warming are assumed to be generic – ie. if the sun warmed the planet then the feedbacks would be the same anyway. But it is possible that there are different types of feedback to solar variation, for example interaction with GCRs or a reaction of the atmosphere to UV.]
The end result is a very high probability that they have severely overstated climate sensitivity. Note that if there are any positive feedbacks to solar variation, then the MWP becomes quite easy to explain.
The Skeptical Science article that you cited uses the same logic as the IPCC Report.
Mike Jonas says:
“This touches on one of the fundamental errors in the IPCC Report. If you look at the way that they analyse solar variation, you will see that they allow only for the direct effect of the variation in solar irradiation. They do not allow for any possible feedbacks. On this basis, the effect of solar variation is relatively small”
This and all you have said after show that you don’t understood the concept of climate sensitivity. Climate sensitivity is, to say it simple, how much the planet temperature changes in response to a change in radiative forcing. This forcing could be be the result of solar variation, aerosols emissions or greenhouse gases. The point is that the climate sensitivity show the planet response to ANY forcing, no matter if it is solar, aerosols or greenhouse.
Climate sensitivity could be obtained in two ways:
1)Theoretically, computing with the help of a climate model the temperature change resulting directly from the forcing plus all feedbacks.
2)Using past climate (paleoclimate): this is much simpler. Just divide the temperature change in a past time period by the forcing change.
climate sensitivity =ΔT/ΔF
The past temperatures are obtained from climate proxies (ice cores, tree rings, corals, lake sediments, etc) and the instrumental record (for recent times). The past forcings are obtained from other proxies like sunspots and C-14 isotopes for solar activity, ice core bubbles for greenhouse gases , ash and sulfates in sediments for volcanic activity.
The 3ºC per doubling of CO2 is obtained mainly by the second method. This method do NOT use any climate modelling, and do NOT divide the temperature change in direct effect + feedback. Both effects are considered in the simple division. The value obtained, 3ºC per doubling of CO2 is the same that 0.8ºC /(W/m^2).
The most useful climate sensitivity value is the second. You can convert it to sensitivity to CO2 increase by the formula:
ΔF = 5.35*ln([CO2]/[CO2]o)
But don’t be fooled: the climate sensitivity to CO2 is equal to the climate sensitivity to solar variation, aerosol dimming or any other forcing.
The immdiate consecuence of all this is that if the climate sensitivity to solar variation is greater than climate scientists so far had estimated (as would be implied by a warmer Medieval Warm Period) then NECESSARILY the climate sensitivity to CO2 increase (that is after all the same quantity) is bigger.
Climate Sensitivity is defined in the IPCC Report, Annex I, Glossary, page 943, as follows:
“Climate sensitivity
In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in the annual mean global surface temperature following a doubling of the atmospheric equivalent carbon dioxide concentration.“
Mike Jonas says:
February 15, 2011 at 11:04 am
“Climate Sensitivity is defined in the IPCC Report, Annex I, Glossary, page 943, as follows:
Climate sensitivity:In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in the annual mean global surface temperature following a doubling of the atmospheric equivalent carbon dioxide concentration.”
That’s just a matter of the form used to show the value of climate sensitivity (i.e. units). You can express the climate sensitivity in this units:
form 1: ºC/(doubling of CO2)
form 2: ºC/(W/m^2)
You can use the units you want. The IPCC chose the first option of the 2 forms above. You can convert the first form into the second using this equation:
ΔF (W*m^-2) = 5.35*ln([CO2]/[CO2]o)
Again, climate sensitivity is the global temperature response to ANY radiative forcing (solar, greenhouse, aerosols, etc). Don’t be fooled by the units chosen!
Deg C per doubled CO2 is “Climate Sensitivity”. Deg C per Wm-2 is called the “climate sensitivity factor”. They are not interchangeable:
IPCC Report 9.6.1 : “Methods to Estimate Climate Sensitivity
The most straightforward approach to estimating climate sensitivity would be to relate an observed climate change to a known change in radiative forcing. Such an approach is strictly correct only for changes between equilibrium climate states. Climatic states that were reasonably close to equilibrium in the past are often associated with substantially different climates than the pre-industrial or present climate, which is probably not in equilibrium (Hansen et al., 2005). An example is the climate of the LGM (Chapter 6 and Section 9.3). However, the climate’s sensitivity to external forcing will depend on the mean climate state and the nature of the forcing, both of which affect feedback mechanisms (Chapter 8). Thus, an estimate of the sensitivity directly derived from the ratio of response to forcing cannot be readily compared to the sensitivity of climate to a doubling of CO2 under idealised conditions. An alternative approach, which has been pursued in most work reported here, is based on varying parameters in climate models that influence the ECS in those models, and then attaching probabilities to the different ECS values based on the realism of the corresponding climate change simulations. This ameliorates the problem of feedbacks being dependent on the climatic state, but depends on the assumption that feedbacks are realistically represented in models and that uncertainties in all parameters relevant for feedbacks are varied. Despite uncertainties, results from simulations of climates of the past and recent climate change (Sections 9.3 to 9.5) increase confidence in this assumption.”
[my emphasis]
Note that although they say confidence has been increased, and although they formally quantify their confidence about just about everything in the report, as far as I can see they still do not quantify their confidence in this matter. I suspect therefore that their “increased” confidence is still very low.
I contend that feedbacks are not realistically represented in models. The IPCC acknowledges that it does not know how clouds work, yet relies on a positive cloud feedback for more than 40% of the claimed 1.5-4.5 deg C per doubled CO2 climate sensitivity. This reliance is illogical, since the natural expectation is that increased atmospheric water vapour would most likely lead to increased cloud cover. No mechanism is offered by which clouds might operate in a diametrically opposite manner.
Which I think has brought our dialogue full circle.
Mike Jonas says:
February 17, 2011 at 5:06 am
“Deg C per doubled CO2 is “Climate Sensitivity”. Deg C per Wm-2 is called the “climate sensitivity factor”. They are not interchangeable”
Huh?
Your IPCC quote says:
“The most straightforward approach to estimating climate sensitivity would be to relate an observed climate change to a known change in radiative forcing.”
Climate sensitivity is the temperature response to “a change in radiative forcing”, not just change in CO2. You could express it either in sensitivity to a doubling of CO2 or sensitivity to a change in W*m^-2.
The numbers and units could be diffrerent, but it is the SAME quantity!
It is true that “an estimate of the sensitivity directly derived from the ratio of response to forcing cannot be readily compared to the sensitivity of climate to a doubling of CO2 under idealised conditions” but this is because under real conditions equilibrium climate state (“ideal conditions”) is almost never reached.
This means that only a fraction of the warming (or cooling) has happened. So if you do the simple division:
climate sensitivity (ºC /(W*m^-2)) = ΔT(ºC)/ ΔF (W*m^-2)
The numerator (the change in temperature) is less than the equilibrium response to the forcing, so this result is an UNDERestimate of climate sensitivity: it is a lower bound.
The other form of estimating climate sensitivity is using climate models. These have the advantage that the feedback parameters (that dominate the climate sensitivity value) could be varied depending on the mean climate state (for example glacial vs. interglacial) and the type of forcing (for example shortwave vs. longwave), but this has the problem that the resulting climate sensitivity is model dependent.
Since I have little skills in climate modeling, I will stick to the first method, that is, dividing the temperature change by the climate forcing. And since the results are empirical (as opposed by the theorethical assumptions of the climate models) I think this method is more trustworthly than climate modelling. Of course I must caution of the uncertainties of the method, and I will.