At each time step the distribution of LOESS fits was evaluated and the maximum probability, hence the most likely value for long-term CO2, and the associated 68 and 95 percentile ranges were determined (Fig. 1 and Supplementary Data 2).

Our new compilation and probabilistic treatment reveals that for the last ∼420 Myrs, CO2, on the whole, has been elevated compared to pre-industrial values (278 p.p.m.). The highest CO2 values of ∼2,000 p.p.m. were reached during the Devonian (∼400 Myrs ago) and Triassic (220–200 Myrs ago), with individual estimates ranging up to a maximum of ∼3,700±1,600 p.p.m. at 215 Myrs. In contrast, values close to pre-industrial are found during much of the Carboniferous (∼300 Myrs ago) and late Cretaceous (∼80 Myrs ago). A linear fit to either the entire CO2 compilation, or a resampling of our LOESS fit to reflect the original data density, reveals that long-term average CO2 has declined over the last 420 Myrs by ∼3.4 p.p.m. per Myrs (Fig. 1).

Radiative forcing through the last 420 million years
Radiative forcing from CO2 change can be calculated using equation (6). This can then be combined with the radiative forcing from the increase in solar output defined by equation (3) (Fig. 2a); the temporal evolution of the simple sum of these terms (ΔFCO2,sol) is shown in Fig. 2b. As has been noted elsewhere with prior Phanerozoic CO2 compilations (for example, refs 31, 32), there is a good first-order agreement between CO2 levels and the occurrence of greenhouse/icehouse states (Fig. 1): CO2 is high during greenhouse climate states and low during icehouse climates. Our data support previous work suggesting that, when ΔFCO2,sol is considered, icehouse states generally occur when climate forcing drops below approximately +1–2 Wm−2 (refs 31, 32). This treatment also reveals that for the last 420 Myrs, despite a gradual 4% increase in solar luminosity (equivalent to +9 Wm−2 of radiative forcing), there has been very little long-term change in ΔFCO2,sol (despite shorter-term fluctuations of up to 10 Wm−2), with a linear fit to all the data suggesting only a slight decrease of 0.004 Wm−2 per Myrs (±0.001 1 s.e.m.; P=0.0003; red line on Fig. 2b); a linear fit to our LOESS fit resampled with the original data density yields a slightly higher negative slope (−0.008±0.001 1 s.e.m.; P<0.0001; black line Fig. 2b). This indicates that the long-term decrease in CO2 over the last 420 Myrs has largely compensated for the increase in solar output over the interval. In terms of shorter-term radiative imbalances, 95% of the ΔFCO2,sol values are within ±7 Wm−2 and 68% within +5/−3 Wm−2 (Fig. 3). Thus, even on multi-million-year timescales (and sometimes shorter) the external radiative forcing (not considering the action of additional feedbacks internal to the climate system such as the ice-albedo feedback) has not varied beyond ±2.0% of the total incoming radiation (∼340 Wm−2).

Regardless of the ultimate cause for the observed relative stability in ΔFCO2,sol over the last 420 million years, business-as-usual emission scenarios (for example, representative concentration pathway RCP8.5)39 for fossil fuel emissions suggest that atmospheric CO2 could peak in 2,250 AD at ∼2,000 p.p.m. CO2 values as high as this were last seen in the Triassic around 220–200 Myrs ago (Figs 3 and 4). However, because of the steady increase in solar output over time, in terms of radiative forcing by the end of this century RCP8.5 is similar to the early Eocene, and by 2,250 AD exceeds what is recorded in the geological record for at least 99.9% of the last 420 Myrs (Figs 3 and 4).

Here is a presentation by idiot and AGW denier Salby:

Quote:


https://judithcurry.com/2016/08/10/murry-salbys-latest-presentation/

Pure male bovine excrement!

Satellite spectrometry shows the gaps in the IR spectrum from earth at each of the GHGs like CO2 and Methane, nitrous oxide, CFCs etc.

Bullshyte.

Ajax wrote on Apr 7^th, 2017 at 7:42am:


This man is sane. The other numpty not so.

I don’t care what denier crap you come up with, Ajax, the case for AGW through emission of GHGs from burning of fossil fuels is pretty watertight.

I don’t care what denier crap you come up with, Ajax, the case for AGW through emission of GHGs from burning of fossil fuels is pretty watertight.

And I don’t “hate life” the very idea is ridiculous!

AGW won’t bother me much in the time I have left, but it will bother young people I love and that is something I would like to do something about.

Deniers know AGW is happening—just look around, the melting or Arctic ice, the retreat of glaciers etc—but are afraid of the consequences so turn to denialism.

I am not that cowardly!

Quote:
The primary source of energy in the Earth’s climate system is incoming solar radiation, termed total solar irradiance, or TSI. At equilibrium, because of the requirement of energy conservation, the Earth’s radiative budget must balance such that TSI is equal to outgoing longwave radiation at the top of the atmosphere (a state known as radiative equilibrium). Since the radiation emitted by a body is a function of surface temperature, the Earth’s ‘effective temperature’ (TE) is the temperature at which radiative equilibrium is achieved assuming the Earth acts like a blackbody, and can be calculated (in K)

where Fs is the TSI (currently ∼1,368 Wm−2), σ is the Stefan–Boltzmann constant (5.67 × 10−8 W m−2 K−4), A=0.29 (ref. 1) is the Earth’s average planetary albedo (the fraction of incoming radiation scattered or reflected back out of the atmosphere by clouds, particulates in the atmosphere and the Earth’s surface),

However, at the temperatures and pressures typical of the Earth’s surface, water vapour and clouds act as feedbacks rather than drivers of the greenhouse effect,

Quote:
As a result, there has been an increase in TSI of ∼400 Wm−2 since the formation of the Earth.

in early Cambrian/Ordovician time the sun was much weaker than now.

Quote:
Following ref. 4, and assuming an effective emissivity, ɛ, of the Earth of 0.6 (that is, 40% of longwave radiation is absorbed by greenhouse gases in the atmosphere), equation (1) can be used to define the following equation that describes S for today’s climate (where the surface temperature=287.1 K) in the absence of any climate feedbacks (for example, water vapour, sea-ice etc.), also known as the Planck response (hence the subscript ‘P’)

. Since the combined effect of the greenhouse gas and other climate feedbacks (for example, water vapour, lapse rate, sea-ice etc.) is positive

yet there is a longstanding view that, despite the increase in solar output, Earth’s surface temperature was, for much of geological time, warmer, not colder, than today

Oh good, you had a skim and found some bits you think you can refute with your usual junk. Does your cute HS science diagram apply to Ordovician time, Devonian etc?

I think the paper stands as is. It covers a lot of geological time and has a lot of footnotes where you could find stuff like error bars and all that. It necessarily has to assume some things or leave it to footnotes.

You could learn a lot from it if you were so inclined.

Are we Venus?

We are not Venus so the equation is substantially true.

Try and understand the paper as a whole.

If you have quibbles, read the 80 footnoted papers cited.

If, in Ordovician times, sky high CO2 levels, the Sun was the same brightness as now, we would look a lot like Venus.

Now look at the end, at the predicted CO2 levels next century and join the dots.

Well, good for you re the solar panels!

Modern nuclear is much safer than the older tech as in Fufushima and Chernobyl.

We do have to move away from burning fossil fuels for energy tho.

We do have good places to store waste tho: deserts and old mines like Mt Painter and the Broken Hill mines, only one being worked today IIRC from my trip there about 10 years ago.

Oh puhlease how many times must you be told the planet is dynamic and that the natural climate system has both negative and positive feedbacks?

Still ignoring the facts eh Monk.
What a waste of space YOU are.

As for your sidekick, Dropkick... it doesn't even maintain track of what it says.  Let alone posting anything that has any real meaning.

It doesn't matter how many times you tell him the reports and articles and papers referenced on the JoNova site are mostly from real experts and scientists...  same with other sites he call "denialist" now that is ironic coming from him.

He just closes his eyes, puts his hands over his ears, sings "lalala I cant hear you" at the top of his voice, whilst stomping around in ever decreasing circles.