shub

he is implying a position the IPCC itself does not hold.

You claim that the IPCC position is that natural variation has stopped. This is utter nonsense. It's astonishing that you repeat this claim after I've pointed out - twice now - that the quotes from 'IPCC 2007' you provided above clearly indicate that a *combination* of natural variation and anthropogenic forcing is required to explain observed recent climate behaviour.

You then double down:

Natural variability is dialed in, and back out, as an explanation for various portions of the curve, which is indeed shown and predicted to rise monotonically. If one observes the IPCC projections, they all show monotonic projections with various rates of rise.

Here's a standard example of modelled simulations of C20th climate with and without anthropogenic forcings. The black curve represents observed temperatures. You can see that the multi-model mean in panel (a) is *not* monotonic - the interplay between natural and anthropogenic forcings is clearly evident even though it is an average of multiple runs.

Here is a detailed representation of the same model ensembles from AR4 under anthropogenic forcing, but now extended to 2020. Once again, *natural varibility* is very evident. At a guess, I'd say you've confused the centennial-scale multi-model means with the mass of highly variable individual runs.

This is the AR4 statement on the co-existence of natural variation with anthropogenic forcing in modern climate variability:

‘Climate change’ refers to a change in the state of the climate that can be identified (e.g., using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer (see Glossary). Climate change may be due to internal processes and/or external forcings. Some external influences, such as changes in solar radiation and volcanism, occur naturally and contribute to the total natural variability of the climate system. Other external changes, such as the change in composition of the atmosphere that began with the industrial revolution, are the result of human activity. A key objective of this chapter is to understand climate changes that result from anthropogenic and natural external forcings, and how they may be distinguished from changes and variability that result from internal climate system processes.

Internal variability is present on all time scales. Atmospheric processes that generate internal variability are known to operate on time scales ranging from virtually instantaneous (e.g., condensation of water vapour in clouds) up to years (e.g., troposphere-stratosphere or inter-hemispheric exchange). Other components of the climate system, such as the ocean and the large ice sheets, tend to operate on longer time scales. These components produce internal variability of their own accord and also integrate variability from the rapidly varying atmosphere (Hasselmann, 1976). In addition, internal variability is produced by coupled interactions between components, such as is the case with the El-Niño Southern Oscillation (ENSO; see Chapters 3 and 8).

You are still relying on a mix of muddle and misrepresentation instead of coherent argument.

In the hope of re-railing the thread, has everyone seen the latest 'on hold' review of climate scientist and communicator David Karoly's review of his pal's book:

Mann [who is an expert in everything related to climate science except statistics] never imagined that his research would push him out of the ivory towers of academia into the cut-and-thrust world of politics, commentators, and lobbyists. But it certainly did, and this book describes his experiences over the last two decades as a climate scientist, as a communicator, and as a target of frequent attacks. Mann was subjected to what he describes as the ‘Serengeti strategy’, in which predators ‘look for the most vulnerable animal at the edge of a herd’. In his case the predators were climate change ‘confusionists’, politicians and commentators who wish to confuse the public understanding of climate change science and delay action on reducing industrial emissions of green-house gases.

I always thought Karoly would make a good 'zebra of the week'. He was already wounded during the hunt for the small Gergis group. And now he comes back for more action. And now he's started running already.

The WUWT pride is on him. But why do they behave like that? I mean the zebras who want some climate communication; why do they always end up running away, and where do they think they can hide in the Serengeti?

shub

If a "combination of natural variability and CO2" explains temperature changes, how come natural variability explains only the cooling and CO2 only explains the warming?

You just can't see it can you? First off, what if it's not all natural? What about sulphates from Chinese coal, for example? Then as for the natural forcings, how about the historically quiet Solar Cycle 24? And predominantly La Niña conditions over the last decade? Deep ocean mixing?

All these things can offset warming from CO2 forcing. For a while. An unusual combination of events doesn't constitute the killer argument you seem to think.

Put a little bit of pressure and this guy changes his tack. He can't keep his story straight within the space of two comments.

The usual dishonesty.

It doesn't 'topple the theory'. As explained above.

Keyword: denial.

rhoda

It says the theory proposer may take into account things he never mentioned before

Same strawman as shub: *nobody* ever said warming would be monotonic. Nobody ever said natural variation would stop. Shub was talking his usual uninformed, biased crap. One does have to bear this in mind. Closer reading of my responses might be helpful too.

This is getting tiresome.

Dung

Laken & Calogovic (2011)

Although over centennial and greater timescales solar variability may be one of the most influential climate forcing agents, the extent to which solar activity influences climate over shorter time periods is poorly understood. If a link exists between solar activity and climate, it is likely via a mechanism connected to one (or a combination) of the following parameters: total solar irradiance (TSI), ultraviolet (UV) spectral irradiance, or the galactic cosmic ray (GCR) flux. We present an analysis based around a superposed epoch (composite) approach focusing on the largest TSI increases and decreases (the latter occurring in both the presence and absence of appreciable GCR reductions) over daily timescales. Using these composites we test for the presence of a robust link between solar activity and cloud cover over large areas of the globe using rigorous statistical techniques. We find no evidence that widespread variations in cloud cover at any tropospheric level are significantly associated with changes in the TSI, GCR or UV flux, and further conclude that TSI or UV changes occurring during reductions in the GCR flux are not masking a solar-cloud response. However, we note the detectability of any potential links is strongly constrained by cloud variability.

Sloan & Wolfendale (2011)

A search has been made for a contribution of the changing cosmic ray intensity to the global warming observed in the last century. The cosmic ray intensity shows a strong 11 year cycle due to solar modulation and the overall rate has decreased since 1900. These changes in cosmic ray intensity are compared to those of the mean global surface temperature to attempt to quantify any link between the two. It is shown that, if such a link exists, the changing cosmic ray intensity contributes less than 8% to the increase in the mean global surface temperature observed since 1900.

Dung

'Shorter time periods' per L&C includes the recent warming attributed to CO2 forcing. Long periods means eg the Holocene. Solar influence on climate means stuff like Milankovitch forcing. The study shows that no solar-climate link operating over *shorter* time periods can be demonstrated. In other words, it's one of the ever-growing stack that finds no evidence supporting the Svensmark hypothesis. We are back to CO2 again.

I can't find a downloadable pdf of L&C but S&W is here.

I can see why SW figs 1 & 2 might have confused you but it is explained in the paper itself. The apparent relationship breaks down since the mid-C20th. Once again, there's *no evidence* to support the Svensmark hypothesis:

Figure 2 shows the data from figure 1 with 11 year smoothing applied to illustrate the long term trends (removing the effects of the solar cycle). It can be seen that the CR rate decreased rapidly from 1880 to 1950 when the temperature rise was relatively small. On the other hand the CR rate changed little from 1950-2000 when the temperature rise was bigger (Lockwood and Fr¨ohlich 2007). Hence the variation of the temperature with time matches poorly the variation of the CR rate with time. Such a match would be expected if CR played a significant role in global warming. It can be seen that the CR rate decreased in intensity by 16% from 1880 to 1952 during which time the mean global temperature rose by 0.3◦ while from 1952 to 2000 the CR rate decreased by 3% and the temperature rose by 0.6◦.

Figure 3 shows the values of the temperature anomalies
T, plotted as a function of CR rate, each taken from figure 2. It can be seen that in the early part of the 20th century there was a roughly linear relationship between the two. Linear fits were made to the data in various time ranges starting from 1886. The slopes, d
T/dCR, varied in values from -0.008 to -0.022 ◦C per % change in the Climax NM rate as the end year of the fit varies from the year 1930 to 2000. Cycling through each end year in this time range, the mean value of d
T/dCR was -0.016◦C per % change in the Climax NM rate with root mean square deviation of the readings of 0.003. If there is a causal link between CR and the global temperature, this value of d
T/dCR implies that the 3% change in CR rate observed since 1952 would give a temperature change of 0.05◦C. The observed change in temperature since 1952 is 0.6◦C. Hence less than 8% of the observed rise in temperature since 1952 can be ascribed to CR. We take this as an upper limit on the contribution of CR to GW.

Dung

If you want to believe in an unsupported hypothesis (Svensmark) instead of accepting a theory (CO2-forced AGW) for which vast amounts of supporting evidence exists, that is your privilege.

We are not back to CO2. There happens to be an 800 years lag between temperature and CO2 and you know which one lags I am sure.

CO2, CH4 and water vapour are GHG feedbacks to orbital (Milankovitch) forcing. Of *course* there's a lag. Do you not know that nobody suggests that CO2 is the driver of glacial terminations? You need to stop getting your 'information' from 'sceptic' blogs.

Richard

I have tried to get Spartacus over here but failed however in relation to the 200 ppm saturation point for CO2 he writes:

Anyone who has done analytical chemistry knows the spectroscopic phenomenon of 'self-absorption', absorption of internally-generated EM energy by unexcited molecules. CO2 in air is well into that mode at ~200 ppm.

Illuminate the lower atmosphere with IR energy in the 4 and 14 micron bands and it excites CO2 molecules that would normally absorb thermal radiation from above. That increases DOWN emissivity so more IR in those bands arrives at the Earth's surface. This switches off the states which, when activated by kinetic energy, would emit that radiation.

The same applies to all the other GHGs. Much IR emission from the Earth is shifted to the 'atmospheric window'. Total GHE settles at a constant level. There can be no CO2-AGW. No amount of computer modelling can get over this basic fact.

Could you comment?