Lower climate sensitivity is getting some mainstream discussion. Last week at WUWT, we had this story: BREAKING: an encouraging admission of lower climate sensitivity by a ‘hockey team’ scientist, along with new problems for the IPCC which is now the most read story on WUWT in the past week.
This morning, WUWT carried this essay from Chip Knappenberger: The yearly lukewarm report which spurred some communication from Andrew Rekvin at NYT about the similar story he just posted today: A Closer Look at Moderating Views of Climate Sensitivity.
Andy just sent me a fascinating exchange from Gavin Schmidt of NASA and the Realcimate blog. Gavin sent sent this note as part of a group e-mail exchange and this is what Revkin forwared to me (and has now posted at Dot Earth):
Andy, I think you may be slightly misrepresenting where the ‘consensus’ on this issue has been. While there have been occasional papers that have shown a large tail, and some arguments that this is stubborn – particular from constraints based on the modern tranisent changes – there has always been substantial evidence to rule these out. Even going back to the 2-11deg C range found in the initial cpdn results in 2005, many people said immediately that the high end was untenable (for instance).
Indeed, the consensus statements in the IPCC reports have remained within the 1.5 – 4.5 range first set by Charney in 1979. James’ work has helped improve the quantifications of the paleo constraints (particular for the LGM), but these have been supported by work from Lorius et al (1991), Kohler et al (2010), etc. and therefore are not particularly radical.
By not reflecting that, you are implying that the wishful thinking of people like Ridley and Lindzen for a climate sensitivity of around 1 deg C is tenable. It is not, and James’ statement was simply alluding to that. For reference, James stated that his favored number was around 2.5 deg C, Jim Hansen in a recent letter to the WSJ quote 2.5-3.5 (based on the recent Palaeosens paper), and for what it’s worth the CMIP5 GISS models have sensitivities of 2.4 to 2.7 deg C. None of this is out of the mainstream.
I sent Schmidt and the group this reply:
In policy circles, including popular calculations of emissions trajectories necessary to avoid a high change of exceeding 2 degrees C. of warming, the hot tail has not been trimmed (unless I’m missing something?).
To me, that says the climate science community — including the Intergovernmental Panel on Climate Change science working group — has not adequately conveyed the reality you state here.
======================================================
Anthony: This essay from Pat Michaels is relevant also:
So…for us beginners…does Gavin think there is a possibility the correct number is less than 2.0 already?
This assumes all warming is due to CO2. Where’s the proof?
Revkin awakes?
Let them debate all they want. The practical impact is along the lines that the WEATHER experienced in Portland OR may move north to Seattle in the worst case. It is well known that Portland has no growing season and is in perpetual drought, right? Good Grief.
I find it funny that these guys are allowed to ‘favour’ certain values, and that is ok. I personally favour the lower range of CS, probably less than 1.5 – but presume I will now be chastised by others for not backing that up!
Seriously though – the lower range in the first graph looks far more realistic and that is based purely on the fact that earth today ‘may’ have warmed by around 0.5degC since the industrial revolution (and I am not 100 percent convinced of that, due to the vagaries of the station record, etc). Nevertheless, I am still skeptical about the whole CS issue and it being basically ‘assigned’ or ‘correlated’ to being due to CO2.
Wait… Hansen said 2.5-3.5? Where did he say that? That’s incredibly tame compared to his previous statements.
Also, Gavin Schmidt is gabbin’ sh!t as per usual, since he was riding the 3+ train hard until just recently.
Revkin awakes”, the pink slips tend to focus one’s mind
This observation by Revkin is highly significant. This is what I attempted to point out in my reviews of the drafts of the IPCC 2013 report regarding the apparent absence of any visually obvious trend in the latest NVAP-M time series of global water vapor. While the influence of the IPCC has been diminished for all the well known reasons, it’s still relied on by governments around the world. Scientific integrity demands that the IPCC present objective facts untouched by political or other agendas.
Oh, and as a fun side note the global SIA is above baseline for the first time in awhile, which is neat since Gavin, Mikey, and crew love pointing out lows all the time.
I have my own version of the above chart which shows where the actual observations to date are and that which takes into account Gavin’s comment about the transient warming timeline.
This one goes out to the year 2100 when CO2 will be about 700 ppm and is several years past the time when equilbrium temperatures are reached in the 3.0C per doubling proposition.
http://s3.postimage.org/e3u9d69ub/Zoom_in_RSS_UAH_Hadcrut4_Warming_Dec_12.png
Going from memory, the IPCC AR4 estimate was 2.0 to 4.5. I don’t recall an estimate of 1.5 to 4.5.
Gavin’s statements:
..“I think you may be slightly misrepresenting where the ‘consensus’ on this issue has been…
..the consensus statements in the IPCC reports have been….
Gavin should know better. Climate scientists in general should know better. “Consensus” is not a tenet of the scientific method.
Michael Crichton once stated:
I regard consensus science as an extremely pernicious development that ought to be stopped cold in its tracks. Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled. Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you’re being had.
He went on further to say:
Let’s be clear: the work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science, on the contrary, requires only one investigator who happens to be right, which means that he or she has results that are verifiable by reference to the real world. In science consensus is irrelevant. What are relevant are reproducible results. The greatest scientists in history are great precisely because they broke with the consensus. There is no such thing as consensus science. If it’s consensus, it isn’t science. If it’s science, it isn’t consensus. Period.
So…for us beginners…does Gavin think there is a possibility the correct number is less than 2.0 already?
yes. the only people who are certain about the number are the people who think it is certainly below 1.
‘Wait… Hansen said 2.5-3.5? Where did he say that? That’s incredibly tame compared to his previous statements.”
In a new paleo paper. Not sure if it is out there for everyone to read. Its broadly consistent with what he has said before in his LGM work.
There is a debate in climate science. That debate is about sensitivity. If you want to join that debate you can. specifically the debate is over the range of estimates.
All warming before 1950 (including the 5 previous periods of greater warming than now – Holocene Climatic Optimum (9,000 to 5,000 years ago), Egyptian, Minoan, Roman, and Medieval (850 to 1250 AD) was natural, and all warming since was anthropogenic? The Eemian warming 125,000 years ago was natural, and the current warming which is 8 degrees C cooler with sea level 10 meters lower is not? With all the much greater warming of the past obviously due to natural climate change, why is not the current much more moderate warming also a part of that natural cycle? I can’t recall anything special after 1950, although the remarkable cooling through the mid-1970s while CO2 increased steadily triggered the short-lived “Global Cooling” panic. So there it is, the recent history of CO2 driven warming after 1950 – mostly cooling for the first 25 years, then moderate warming, but not as much as fast as in the 1930s, for the next 20 years, and finally no warming for the last 17 years.
“Me thinks global warming panics should be made of sterner stuff.”
I think Gavin Schmidt is misrepresenting Annan’s estimate.
Annan’s 2.5 deg estimate appears to have been made before including the halt in temperature increase, the reduction of aerosol forcing the increase of black cabon forcing and the discovery of statistics errors in multiple papers.
“Yeah, I should probably have had a tl;dr version, which is that sensitivity is still about 3C.
The discerning reader will already have noted that my previous posts on the matter actually point to a value more likely on the low side of this rather than higher, and were I pressed for a more precise value, 2.5 might have been a better choice even then. But I’d rather be a little conservative than risk being too Pollyanna-ish about it.”
http://www.blogger.com/comment.g?blogID=9959776&postID=1573684829816144955
When the history of science masquerading as politics is written, this episode will warrant a chapter. That scientific mistakes have been made is not the issue (science is all about identifying mistakes and moving forward), no the more interesting aspect is how and why the known scientific uncertainties were misrepresented to the public. When a scientist involved in the IPCC process calls out his colleagues for lying about inflated climate sensitivities to help motivate political action, that is far more damning than making a simple math-error.
I note that they are assuming that 100% of the warming since CO2 was at 270, is due to CO2.
majormike1 says:
February 4, 2013 at 10:57 am
”All warming before 1950 (including the 5 previous periods of greater warming than now – Holocene Climatic Optimum (9,000 to 5,000 years ago), Egyptian, Minoan, Roman, and Medieval (850 to 1250 AD) was natural, and all warming since was anthropogenic?”
of course! How else can you forcefully describe a CO2 based climate sensitivity and correlate it to human growth/emissions! Thats what I love about the warmists – it’s only natural when it suits them, but anthropogenic at all other times!
It is increasingly clear that the earth has entered a cooling trend which will last until 2030 and probably beyond. It is also clear that the climate sensitivity is below the low end of the model ranges.The models are simply structured incorrectly so that their average range is an average of improperly structured models. For a discussion of this see my post “Global Cooling -Timing and Amount.” on my blog
http://climatesense-norpag.blogspot.com/
an earlier post on that site on 11/18/12 “Global Cooling Climate and Weather forecasting” provides links to the relevant data suggesting cooling.
The best discussion of climate sensitivity is seen in John Kehr’s The Inconvenient SKEPTIC on page 230 he persuasively estimates the sensitivity to a doubling from 380 ppm to be 0.7 degrees. Look at the Eemian Interglacial cooling phase ice core temp v CO2 for example. and also the SST temp trend trend v CO2 for the last ten years which would both produce negative sensitivities. The modellers simply picked a time frame which produced a sensitivity to match their preconceptions.
I should have added a reference to my post above:
http://julesandjames.blogspot.co.uk/2013/02/a-sensitive-matter.html
Steven Mosher says:
February 4, 2013 at 10:50 am
>>yes. the only people who are certain about the number are the people who think it is certainly below 1.<<
But logically Steven, and taking the ice core records as 'read' – it must be less than one, possibly even negative! – because CO2 increase always lags the temperature in the ice cores. Until it precedes it (or can be seen to definately accelerate the initial warming, i.e provide a positive AND increasing feedback), logically (on a pure CO2 based CS assumption) actual CS to CO2 must be very small! (and I am ignoring the logarithmic effect of CO2 too!).
Absolutely the climate crowd has not rejected the high end of the spectrum. I had a spat with GS in January of 2011 in which I referred to CAGW, which he denied he was saying. But CAGW is the basis of all proposed action, and requires in excess of 3C of heating by 2100. You cannot say that a >3C rise is unrealistic and claim that we have to act now to stop the world from burning up and the biosphere dying.
The alarm coming from >3C of rise is politically and socially useful. If the IPCC and Hansen and Gore had to admit that the chances were slim to none for a big temp rise, all the steam would go out of their whistle, and the monies out of their grants.
Fig. 4 of the draft AR5 report keeps the blue-gray colour around the Scenarios for the same reason, to make the potential disaster still a possiblity with current observational data. It is a visual trick equivalent to Mann’s Nature Trick. It has the same effect as the non-denial of catastrophic temperature rises: it keeps the alarm up.
If the IPCC were forced to drop its Scenario A from AR5, we’d be a long way towards the end of the Global Warming hysteria. That is what would happen if >2.5C were considered unrealistic.
After 25 years you’d think the “scientists” at the IPCC would have to modify their projections. In any business, scientific or otherwise, additional work is used to tighten projections. Apparently climatology is not a business of any kind – but we knew that: it is politics, where nothing that happens is ever different from what you said would happen.
It would seem to me that with every passing year that the temperatures don’t rise, their sensitivity numbers have to be adjusted downward. Of course, they could have done that by including the period from 1945 to 1975 in their calculations where temperatures were falling as human CO2 emissions were ramping up.
To my mind their entire notion of climate sensitivity to human CO2 emissions goes right out the window when a few questions are asked:
1. What was responsible for the warming from 1912 to 1940? It clearly could not have been human CO2 emissions. Most of the rural areas of the US weren’t even electrified until the 1930’s and then most of the power was hydro. Why do we have significant warming without significant increases in CO2 emissions?
2. What was responsible for the cooling until the 1940’s to 1970’s when global human CO2 emissions were ramping up? Why do we have significant cooling while we have significant increases in global CO2 emissions?
3. Why have temperatures not risen since 1998 when we have a period of both increased air clarity due to emissions controls across most of the world and CO2 emission rates continuing to increase?
4. Why did the temperatures cool so drastically from the early 14th century to the late 19th century while world population was increasing and our CO2 emissions generally increasing? This is also a period of rather massive deforestation and land use change from forest / plains to agricultural.
5. Why have we still not “recovered” fully to the climate of the Medieval Warm Period despite massive amounts of human CO2 emissions generated since that time?
There is only one roughly 30 year period where temperature rise correlates with CO2 emissions. Why are data changed retroactively in such a way as the trend of the changes (in every database of surface temperatures) always act to validate the AGW hypothesis? Why do we have several hundred years of temperature data that show no correlation of temperature change with atmospheric CO2, one roughly 30 year period when they do correlate, and a global alarm sounded that the CO2 is going to cause grave consequences?
Why are the people sounding the alarm that industrial activity and its requisite energy production will cause temperatures to rise to catastrophic levels the same ones who were claiming in the 1970’s that industrial activity and its requisite energy production was going to trigger another ice age?
From a person on the sidelines looking at what is going on, it appears that the goal is to reduce industrial activity and energy production in certain areas but not other areas and then finding some grave economic consequence in order to justify those policy decisions. In other words, it appears that there is an attempt to develop problems that can be used to justify the desired course of action.
It’s the climatology version of the old Jon Stewart “clown nose on, clown nose off” game.
“Look at meeeeee! I turned off the air conditioning at a Senate hearing! I got arrested at a coal plant! I called for war crimes trials for skeptics! I compared coal trains to Auschwitz! Wheee! What fun!”
“Oh, but now I’ve taken off the clown nose, and so I am a Very Serious Person full of Integrity and Reason and Rigorous Intellectual Honesty. I practice Science — and nothing is more important than my work, I’m Saving the World, and so my Gravitas causes the very Earth to shake beneath my irreproachable feet.”
‘But logically Steven, and taking the ice core records as ‘read’ – it must be less than one, possibly even negative! – because CO2 increase always lags the temperature in the ice cores. ”
Nope.cant be less than 1 or you cant get out of an iceball earth.
The lag has nothing to do with it. The lag was predicted before it was discovered and is what one would expect if AGW is true.
Mosher: “cant be less than 1 or you cant get out of an iceball earth.”
I would agree, but at the same time I’ll point out that Earth’s atmospheric system is quite dynamic, and there’s no evidence to suggest that I seen saying climate sensitivity is absolutely static with time.
Climate sensitivity to CO2 might have be different in the past and may be in the future, depending on ambient conditions of the time….and there are many factors that change with time. Then there’s feedbacks, which are also not static/linear with time.