However, the really interesting admission was not that there were other statistically significant periods of warming—periods when CO2 was less likely to be a factor—but the reason for settling on CO2 being chosen as the warming factor in the first place...
H: If you agree that there were similar periods of warming since 1850 to the current period, and that the MWP is under debate, what factors convince you that recent warming has been largely man-made?
PJ: The fact that we can't explain the warming from the 1950s by solar and volcanic forcing—see my answer to your question D [where he referenced Chapter 9 of the IPCC AR4].
Essentially, these scientists chose CO2—and, by extension, man-made CO2—because they were unable to attribute the warming to any other likely factor.
There are, of course, significant problems with this approach, especially in a system as chaotic as Earth's climate. The main problem, of course, is that Jones and his Hockey Team buddies don't seem to have properly investigated other factors—even those which might directly affect their own theory—or, if they suspected that these factors might derail their theory, they attempted to hide them.
To refresh our memories, let us summarise some of the problems...
- The "decline"
The decline—of "hide the decline" fame—is a subset of the "divergence problem". Put simply, this is the fact that the tree-rings that many palaeoclimatologists reply on for temperature reconstructions do not follow modern temperatures; in fact, whilst direct measurements show a rise in temperature, the tree rings show a decline.
Here is the problem shown in two easy-to-understand charts.
If these tree-rings are not a reliable proxy for current temperatures, then why on earth would they be a reliable proxy for past temperatures. And if we cannot reliably build up a picture of past temperatures, then we cannot say that today's warming is unprecedented.
- CO2 climate sensitivity and positive feedbacks
One of the big problems with the whole anthropogenic carbon dioxide disaster theory is that just pumping lots of CO2 into the atmosphere will not warm the planet to disastrous levels—as explained over at Climate Skeptic.
While the climate models are complex, and the actual climate even, err, complexer, we can shortcut the reaction of global temperatures to CO2 to a single figure called climate sensitivity. How many degrees of warming should the world expect for each doubling of CO2 concentrations (the relationship is logarithmic, so that is why sensitivity is based on doublings, rather than absolute increases — an increase of CO2 from 280 to 290 ppm should have a higher impact on temperatures than the increase from, say, 380 to 390 ppm).
The IPCC reached a climate sensitivity to CO2 of about 3C per doubling. More popular (at least in the media) catastrophic forecasts range from 5C on up to about any number you can imagine, way past any range one might consider reasonable.
But here is the key fact — Most folks, including the IPCC, believe the warming sensitivity from CO2 alone (before feedbacks) is around 1C or a bit higher (arch-alarmist Michael Mann did the research the IPCC relied on for this figure). All the rest of the sensitivity between this 1C and 3C or 5C or whatever the forecast is comes from feedbacks (e.g. hotter weather melts ice, which causes less sunlight to be reflected, which warms the world more). Feedbacks, by the way can be negative as well, acting to reduce the warming effect. In fact, most feedbacks in our physical world are negative, but alarmist climate scientists tend to assume very high positive feedbacks.
What this means is that 70-80% or more of the warming in catastrophic warming forecasts comes from feedback, not CO2 acting alone. If it turns out that feedbacks are not wildly positive, or even are negative, then the climate sensitivity is 1C or less, and we likely will see little warming over the next century due to man.
This means that the only really important question in the manmade global warming debate is the sign and magnitude of feedbacks.
Right now, there are some very important—and unanswered—questions regarding feedbacks and general climate sensitivity. Some of these include:
- What is the real sensitvity of climate to CO2 alone? The IPCC seem to be using about 1–1.2°C per doubling, but a recent paper seems to contradict that figure—placing it nearer 0.41°C per doubling.
- Do clouds contribute to negative or positive feedback? This is a colossal issue! Most scientists accept that most of the warmth retention on the Earth is caused by water vapour in the air—indeed, it may account for anywhere between 75% and 95% of the greenhouse effect. You will have encountered this effect yourselves: a clear night is often very cold, whilst a cloudy one can be warm and muggy.
And yet no one really knows whether water vapour has a positive or negative effect on global temperatures! For instance, clouds keep the warmth in but they also reflect sunlight back into space by increasing the Earth's albedo; is this effect positive, negative or, of course, neutral?
Again, a recent paper sheds some more light on this.
As I have written a zillion times, most of the projected warming from CO2 is not from CO2 directly but from positive feedback effects hypothesized in the climate. The largest of these is water vapor. Water is (unlike CO2) a strong greenhouse gas and if small amounts of warming increase water vapor in the atmosphere, that would be a positive feedback effect that would amplify warming. Most climate modellers assume relative humidity stays roughly flat as the world warms, meaning total water vapor content in the atmosphere will rise. In fact, this does not appear to have been the case over the last 50 years, as relative humidity has fallen while temperatures have risen. Further, in a peer-reviewed article, scientists suggest certain negative feedbacks that would tend to reduce atmospheric water vapor.
So, whilst this would suggest that water vapour would have a negative, rather than positive, feedback effect on global temperatures, we still don't really know.
- Why don't we know? Because, as Dr Roy Spencer points out in no uncertain terms, no one is seriously trying to answer these questions.
In fact, NO ONE HAS YET FOUND A WAY WITH OBSERVATIONAL DATA TO TEST CLIMATE MODEL SENSITIVITY. This means we have no idea which of the climate models projections are more likely to come true.
This dirty little secret of the climate modeling community is seldom mentioned outside the community. Don’t tell anyone I told you.
This is why climate researchers talk about probable ranges of climate sensitivity. Whatever that means!…there is no statistical probability involved with one-of-a-kind events like global warming!
There is HUGE uncertainty on this issue. And I will continue to contend that this uncertainty is a DIRECT RESULT of researchers not distinguishing between cause and effect when analyzing data.
And yet we are apparently still willing to spend $78 billion per year to avoid 0.01°C of warming in 2100. Or, to put it another way...
This is over $7 trillion a year per degree of avoided warming, again using even the EPA’s overly high climate sensitivity numbers. For scale, this is almost half the entire US GDP.
Which is why, as I have said many times, the Precautionary Principle is utter bullshit—it assumes that the cost of acting is near-zero when it quite obviously is not.
- Climate models do not produce new data
Far too many people seem to believe that climate models produce data—they do not. They produce models that need to be verified with the real world and, so far, these models have not been very good at doing so.
There are many reasons for this. One of the major ones is that we do not know all of the factors to be included, e.g. the Pacific Decadal Oscillation (PDO)—which has been blamed for the recent lack of warming—was only noticed in 1997.
One of the other reasons is that—as the HARRY_READ_ME.txt file showed—scientists are not particularly good or thorough programmers. Nor are they good or thorough archivers of data.
And another reason is that we simply have not been measuring the climate long enough to understand some of the massive forces at work. The climate may not be inherently unknowable, but we certainly don't know enough at this stage.
An illustration of this last point is the reason that I started this essay. Having waded through the above, you might remember that Phil Jones maintained that the climate scientists attributed the Earth's warming to man-made CO2 because they couldn't "explain the warming from the 1950s by solar and volcanic forcing".
Now, it is true that the sunlight level—or Total Solar Irradiance (TSI)—was, if you smooth for seasonal variations, pretty static over the period in question. However...
Via The Englishman, I am pointed to this detailed article at Irish Weather Online, which has some interesting revelations regarding TSI and the PDO.
The influence of the sun has been discounted in the climate models as a contributor to the warming observed between 1975 and 1998. Those who support the theory of anthropogenic global warming (AGW), now known as anthropogenic climate change (even more recently described as climate disruption) so that recent cooling can be included in their scenario, always deny that the sun has anything to do with recent global temperature movements.
The reason given is that Total Solar Irradiance (TSI) varied so little over that period that it cannot explain the warming that was observed. I don’t yet accept that TSI tells the whole story because it is ill defined and speculative as regards it’s representation of all the different ways the sun could affect the Earth via the entire available range of physical processes.
Despite the limitations of TSI as an indicator of solar influence I think there are conclusions we can draw from the records we do have. Oddly, I have not seen them discussed properly anywhere else, especially not by AGW enthusiasts.
Helpfully, however, the author has included a graph showing the TSI over the last few hundred years. [Click the image for bigger version.]
It is true that, as the alarmists say, since 1961 the average level of TSI has been approximately level if one averages out the peaks and troughs from solar cycles 19 through to 23.
However, those solar cycles show substantially higher levels of TSI than have ever previously occurred in the historical record.
Because of the height of the TSI level one cannot simply ignore it as the IPCC and the modellers have done.
Indeed not. Because here is a smoking gun as far as solar irradiance is concerned...
The critical issue is that having achieved such high levels of TSI by 1961 the sun was already producing more heat than was required to maintain a stable Earth temperature. On that basis alone the theory of AGW cannot be sustained and should now die.
Throughout the period 1961 to about 2001, there was a steady cumulative net warming effect within the oceans from the sun. The fact that TSI was, on average, level during that period is entirely irrelevant and misleading.
It is hardly likely that such a high level of TSI compared to historical levels is going to have no effect at all on global temperature changes and indeed during most of that period there was also an enhanced period of positive Pacific Decadal Oscillation that imparted increasing warmth from the oceans to the atmosphere. My link [...] contains details of my view that the sun drives the various oceanic oscillations which in turn drive global temperature variations with all other influences including CO2 being minor and often cancelling themselves out leaving the solar/oceanic driver supreme.
It could be said that the increase in TSI from a little over 1363 to a little under 1367 Watts per square metre over the 400 year period shown is pretty insignificant. However a square metre is a miniscule portion of the surface of the planet so that even a tiny increase or decrease in the heat being received on average over each such tiny area translates into a huge change in total heat budget for the entire planet. The smallness of the apparent range of variation is a function of the smallness of the area subdivision used rather than an indication of insignificance. It is fortunate for us that the sun is not more variable.
One square metre is, indeed, a tiny proportion of the planet's surface: the Earth has a surface area of approximately 510,072,000 km2 which is (and feel free to correct me on this: all these noughts get me confused) 510,072,000,000 m2. Or over five hundred and ten billion square metres.
The small increase from 1363 Watts per m2 to 1367 Watts per m2 would lead to an energy increase of some 2,040,288,000,000 Watts—or a little over 2 trillion Watts.
To put that into perspective, a large coal-fired power station produces about 700 MW, which is 700,000,000 Watts: so, this small increase in solar output is equivalent to the output of about 2,915 large coal-fired power stations.
Amongst other things [this link] shows how the negative PDO from 1961 to 1975 cancelled out the warming effects of solar cycles 18 and 19 by imparting less warmth from oceans to air and led to a slight cooling trend during those years despite the relatively high TSI levels. The switch to a positive PDO from 1975 to 2001 allowed the solar warming influence in the air to resume. We now have both a falling TSI and a negative PDO which is an entirely different (indeed opposite) scenario to the one which led to the concerns about runaway warming.
If the current scenario continues for a few more years then real world observations will resolve most of the disputed issues. For the past 10 years the real world has been moving in the direction predicted by the solar driver theory and in my articles I have described the oceanic mechanism that transfers solar input to the atmosphere and then to Space.
If global temperatures were to resume warming despite a reduction in solar activity and/or a negative PDO then the alarmist position might be vindicated. The alarmist camp is predicting such a resumption of warming. The Hadley Centre suggested 2010 but others have more recently suggested 2015. If there is no resumption of warming by 2015 then AGW is dead as a theory. It would not count in favour of AGW if any resumed warming were accompanied by increased solar activity or a positive PDO because that would put the solar driver back in control.
So, it's a wait and see policy...
The trouble, of course, is that if this theory is correct, we humans are very much luckier than we would suppose. Because, as far as we can ascertain, a change of just 4 Watts per square metre in TSI means the difference between the mini-Ice Age and a warming planet. That is not a pleasant thought, as the author ennumerates in his conclusion.
The whole of modern civilisation has been made possible by a period of solar stability within a band of less than 4 Watts per square metre. It will not be a result of anything we do if solar changes suddenly go outside that band. On a balance of probability it is more likely that the TSI will soon drop back from the recent unusual highs but remaining within the band of 4 Watts per square metre. It would need the arrival of the next ice age to go significantly below 1363 but even a reduction down to 1365 from present levels could introduce a dangerous level of cooling depending on where the tipping point currently lies.
A period of several decades of reduced solar activity will quickly need more emissions producing activity to SAVE the planet yet nonetheless the populations of most living species will be decimated. At present human population levels a repeat of the Little Ice Age a mere 400 years ago will cause mass starvation worldwide.
Indeed. The last severe reduction in temperature, at the end of the Mediaeval Warm Period, caused widespread famine across the entirety of the Northern hemisphere and caused millions of deaths over a number of years.
The AGW risk analysis process (if anyone ever bothered with one) is seriously flawed.
The whole article is worth reading—even though I have quoted much of it here—and chimes with some of the other bits and pieces that I have been looking into recently.
If the author is correct, let us sincerely hope that our societies are more ready for the temperature downturn than those of 1315...