Some sense about sensitivity

You need the initial CO2 forcing of 3.7 W/m2 (and add in another 0.5 W/m2 for the other GHGs) plus feedbacks of over 2.2 W/m2/K to get to 3.0C per doubling.
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-8-14.html
If the feedbacks are less than 2.2 W/m2, then we come in right around the current estimates of close to 1.5 C per doubling.
http://s24.postimg.org/7jjj2kcgl/Feedback_Strength.png
So let’s look at the net Radiative forcing to date (2.28 W/m2 in IPCC AR5 in 2012) and assume the feedbacks are operating as expected (0.7C temperature rise at over 2.2 W/m2/K feedbacks),
There is a lot of expected forcings and feedbacks producing almost net energy accumulation or increased OLR to space.
http://s10.postimg.org/vf4h3oizd/Net_Forcing_Feedbacks_Energy_Going.png
2.67 W/m2 is nowhere to be found meaning (either the GHG forcing numbers are wrong, the aerosols negative is much larger than is currently estimated, the feedbacks are actually negative – meaning cloud feedback is strongly negative given there does appear to be some positive water vapor feedback).
http://s15.postimg.org/5ot9zkocr/Net_Forcing_Heat_Accum_vs_Missing_Energy.png

There was a large 0.9W/m2 forcing in a short 13 year time period due to a 5% reduction in cloud cover between 1987 and 2000 (ISCCP). Temps increased by 0.3W/m2 as a result
Therefore Climate sensitivity is less than 0.4W/m2. Close to neutal feedback is the maximum you can have!
And remember the recent paper that found that CO2 forcing may only be half as much as what is accepted currently!

Mr, Courtney, thank you for that link. Like Mr. Hanley, I’ve been having problems understanding that.

“The global warming “crisis” emerged from a belief that small rises in CO2 concentrations result in large knock-on effects, or strong positive feedbacks”.
I suppose the IPCC couldn’t also consider that the sun could also have strong knock-on effects, or strong positive feedbacks?. Even been outside our a cloudy cool morning, where the sun drives off the clouds and then afterwards it gets warmer? Too simple for the modellers to understand.

vukcevic says:
April 24, 2013 at 11:18 am
If CO2 concentration in the early 1700’s was about 280 ppm, and currently 390, gives ratio of 1.4.
That is if you believe the ice cores and not the actual measurements of chemists. The collation by Beck of routine measurements of CO2 made by various scientists would appear to show that the ice cores are a very poor proxy due to diffusion of gas in the ice and effects of the drilling of the core and depressurization. Yet for some reason routine measures by Nobel Laureate chemists are thrown out in favor of the claims of ice core bubbles.

stan stendera says:
April 24, 2013 at 9:08 am
Another hugh crack in the Berlin Wall of climate denial.

I’m afraid I’m not acquainted with Hugh, er, Mr. Crack. Sounds like an eminent climate scientist, no doubt.

Communicating Climate Science
Mojib Latif
Figure:
http://orssengo.com/GlobalWarming/ClimateModelGmst.gif
There is a broad scientific consensus that the climate of the 21st century will warm in response to the anthropogenic emission of greenhouse gases (GHGs) into the atmosphere, but by how much remains highly uncertain. This is due to three factors: natural variability, model error, and emission scenario uncertainty. We as climate scientists should stress this uncertainty when talking to the public. Dealing with uncertainty is an integral part of our daily life, and we are used to assess the risk of certain steps we take. Nobody would board, for instance, an aircraft that will crash with a probability of only ten percent. Emphasizing in the public discourse too much the consensus – which is an artificial construct – can be very dangerous, and the climate research community can lose its credibility when not clearly stating publicly the uncertainties.
Atmospheric carbon dioxide (CO2) levels have skyrocketed since the start of industrialization and reached values unprecedented in man’s history. The globally averaged surface air temperature of the planet has warmed during the 20th century, global sea level has risen, and many mountain glaciers and Arctic sea ice have considerably retreated. There is overwhelming scientific evidence that a significant share of 20th century warming is driven by the increase of GHGs. They will continue to accumulate in the atmosphere over the next years and possibly even decades, which together with the inertia of the climate system will support further warming. But what else do we really know about the climate of the 20th and 21st century?
Surface air temperature (SAT) during the 20th century displays a gradual warming and superimposed short-term fluctuations (the figure shows observed annual Northern Hemisphere and Arctic SAT as red lines). The upward trend contains the climate response to enhanced atmospheric GHG levels but also a natural component. The temperature ups and downs around the trend – which are particularly pronounced in the Arctic – mostly reflects natural variability. The scientific challenge is to quantify the anthropogenic signal in the presence of the background climate noise. Natural climate variations are of two types, external and internal. External fluctuations need a forcing, a change in the boundary conditions. Volcanic eruptions and fluctuations in solar output are examples. The Philippine volcano Mt. Pinatubo, for instance, caused a short-lived drop of global SAT in 1991; and an increase of the solar radiation reaching the earth may have contributed to the mid-century warming during 1930-1940. The anthropogenic influence is also considered as external.
One way to estimate the external contribution to the 20th century SAT change is to run climate models with observed natural and anthropogenic forcing. The average over all IPCC models is the consensus (black lines). The spread (gray shading), however, is large, partly because natural variability can be also produced internally by the climate system itself. A well-known example of an internal fluctuation is El Niño, a warming of the Equatorial Pacific occurring on average about every 4 years. The record event of 1997/1998 “helped” to make 1998 the warmest year to date globally . The last year also happened to be an El Niño year, which supported, for instance, weak Atlantic hurricane activity. The event still persists and was partly responsible for January 2010 being one of the warmest Januarys on record. Different initial states yield different realizations of internal variability in models even under identical external forcing, one reason for the spread, as integrations are performed in ensemble mode with different start conditions.
To some extent, we need to “ignore” the natural fluctuations, if we want to “see” the human influence on climate. Had forecasters extrapolated the mid-century warming into the future, they would have predicted far more warming than actually occurred. Likewise, the subsequent cooling trend, if used as the basis for a long-range forecast could have erroneously supported the idea of a rapidly approaching ice age. The detection of the anthropogenic climate signal thus requires at least the analysis of long records, because we can be easily fooled by the natural fluctuations, and we need to understand their dynamics to better estimate the internal noise level.
The spread also reflects model error. Climate models are based on basic physical principles. As such they are fundamentally different to empirical models which are used, for instance, in economic forecasting. Climate models, however, are far away from being perfect. Errors in annual mean SAT, for instance, typically amount to several degrees in some regions . Limitations in computer resources dictate the use of either reduced or relatively coarse-resolution models. As a consequence many important processes cannot be explicitly simulated; they must be parameterized. Some processes like cloud formation or some radiation processes are not completely understood and differently represented in the models, which adds to the uncertainty.
One way to compare models is by means of the climate sensitivity which is defined as the equilibrium change in globally averaged SAT in response to a doubling of the pre-industrial atmospheric CO2 concentration (from 280 to 560ppm ). IPCC AR4 stated that the value ‘…is likely to be in the range 2°C to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C’. In the IPCC definition likely refers to an outcome or result when its likelihood is greater than 66% probable. Very unlikely means a probability of less than ten percent. Thus there is a non negligible probability that the climate sensitivity is either considerably smaller or larger than 3°C. Apparently, just communicating the consensus, the best estimate, is inappropriate. The uncertainty in climate sensitivity itself is in my opinion a good reason to demand reductions of global GHG emissions, because the possibility of ‘a dangerous interference with the climate system’ cannot be ruled out with high confidence.
To predict the future climate we have to consider both natural variability and anthropogenic forcing. The latter is taken into account by assuming scenarios about future GHG and aerosol emissions. The scenarios cover a wide range of the main driving forces of future emissions, from demographic to technological and economic developments. IPCC AR4 published only climate projections based on such scenarios with no attempt to take account of the likely evolution of the natural variability. This by definition yields relatively smooth trajectories if the results are averaged over many models. In the real world, the natural variations will introduce a large degree of irregularity, and even short-term cooling may occur during the next years . This could have been explained better to the public, as in some media reports the existence of Global Warming has been questioned after for more than ten years no global SAT record has been observed. Had we emphasized more the uncertainty, that debate which confused many people could have been avoided. Albert Einstein once said that we should make ‘things as simple as possible, but not simpler’.
Mojib Latif is a Professor of Climate Physics at Kiel University and Head of the Ocean Circulation and Climate Dynamics Division of the Helmholtz Centre for Ocean Research, Germany. He is Contributing Author of the IPCC Reports 2001 (TAR) and 2007 (AR4).

Ian W says:
April 24, 2013 at 6:33 pm
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further to the point made by Ian.
I have commented many tiimes on this old experiment data. I have suggested that those experiments should today be replicated, ie., use the same equipment, take the samples in the same manner from the same location at the same time of year.
It would be interesting to see how data extracted from such replicated experimentation compares with the original results.

I know there is a lot of debate about climate sensitivity, but I want to add something new to the discussion. I thought it might be useful to take a step back for a moment and look at the big picture. If we accept that Earth’s climate has changed dramatically in the past, which it has, then isn’t this the strongest evidence we have for a higher climate sensitivity? If the Earth’s climate had remained relatively stable over millions of years, then this would tend to suggest a low sensitivity. But we know it hasn’t.
50 million years ago there was no ice at either pole and crocodiles lived off the coast of Greenland (bones from these animals have been found there) along with a variety of subtropical plants (fossils have also been found). A cimate sensitivity of 2C per doubling of CO2 will not create a warm enough habitat for crocodiles in the arctic. This would suggest that our models are not sensitive enough to forcing of CO2.
Any thoughts?

Rachel says:
April 25, 2013 at 4:40 am
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I am not aware of any crocodiles in Greenland from the Eocene but what you are probably thinking of is this period, 94 Mya to about 60 Mya. Crocodile fossils have been found originating from this period in the Arctic on both sides of the warm inland sea which covered North America from Texas to Inuvik at the time.
It is highly likely that a small gulf stream-like ocean current flowed up this inland sea to the Arctic ocean given the way ocean currents organize themselves today (which is how the crocodiles got up there and who knows what they did in the 6 months of no sunlight – reptiles need to warm up in the sun for example – they probably migrated south down the inland sea in the winter months).
http://upload.wikimedia.org/wikipedia/commons/6/64/94_mya_Texas_Geology.JPG
Obviously, it was warmer then, maybe up to 9.0C globally but note how much of the continents were flooded by shallow ocean (much of our oil comes from this period when shallow oceans covered 30% of the continents). Does it need to caused by CO2 or can the continental alignments and the shallow oceans increase temperatures by 9.0C on their own, leaving no highly reflective glacial ice at the same time further increasing the Earth’s temperature?