De feiten zijn zoals ze zijn,
en modellen zijn natuurlijk geen feiten.
Er zijn er voor zover mij bekend geen die onder de 2 C blijven
Hieronder staan er een aantal studies waar er ook een aantal met een waarde onder de 2 komen.
Even een greep uit de Wiki on Climate Sensitivity.
Zo zijn er echt heel veel studies, die allemaal van andere aannames uitgaan en dan ook met ver uiteenlopende resultaten komen.
The IPCC Fifth Assessment Report stated: Equilibrium climate sensitivity is likely in the range 1.5 °C to 4.5 °C (high confidence), extremely unlikely less than 1 °C (high confidence), and very unlikely greater than 6 °C (medium confidence).
Sample calculation using industrial-age data
Rahmstorf (2008)[12] provides an informal example of how climate sensitivity might be estimated empirically, from which the following is modified. Denote the sensitivity, i.e. the equilibrium increase in global mean temperature including the effects of feedbacks due to a sustained forcing by doubled CO2 (taken as 3.7 W/m2), as x °C. If Earth were to experience an equilibrium temperature change of ?T (°C) due to a sustained forcing of ?F (W/m2), then one might say that x/(?T) = (3.7 W/m2)/(?F), i.e. that x = ?T * (3.7 W/m2)/?F. The global temperature increase since the beginning of the industrial period (taken as 1750) is about 0.8 °C, and the radiative forcing due to CO2 and other long-lived greenhouse gases (mainly methane, nitrous oxide, and chlorofluorocarbons) emitted since that time is about 2.6 W/m2. Neglecting other forcings and considering the temperature increase to be an equilibrium increase would
lead to a sensitivity of about 1.1 °C. However, ?F also contains contributions due to solar activity (+0.3 W/m2), aerosols (-1 W/m2), ozone (0.3 W/m2) and other lesser influences, bringing the total forcing over the industrial period to 1.6 W/m2 according to best estimate of the IPCC AR4, albeit with substantial uncertainty. Additionally the fact that the climate system is not at equilibrium must be accounted for; this is done by subtracting the planetary heat uptake rate H from the forcing; i.e., x = ?T * (3.7 W/m2)/(?F-H). Taking planetary heat uptake rate as the rate of ocean heat uptake, estimated by the IPCC AR4 as 0.2 W/m2,
yields a value for x of 2.1 °C. (All numbers are approximate and quite uncertain.)
Sample calculation using ice-age data
In 2008, Farley wrote: "... examine the change in temperature and solar forcing between glaciation (ice age) and interglacial (no ice age) periods. The change in temperature, revealed in ice core samples, is 5 °C, while the change in solar forcing is 7.1 W/m2. The computed climate sensitivity is therefore 5/7.1 = 0.7 K(W/m2)?1. We can use this empirically derived climate sensitivity to predict the temperature rise from a forcing of 4 W/m2, arising from a doubling of the atmospheric CO2 from pre-industrial levels.
The result is a predicted temperature increase of 3 °C."[26]
Based on analysis of uncertainties in total forcing, in Antarctic cooling, and in the ratio of global to Antarctic cooling of the last glacial maximum relative to the present,
Ganopolski and Schneider von Deimling (2008) infer a range of 1.3 to 6.8 °C for climate sensitivity determined by this approach.[27]
A lower figure was calculated in a 2011 Science paper by Schmittner et al., who combined temperature reconstructions of the Last Glacial Maximum with climate model simulations to suggest a rate of global warming from doubling of atmospheric carbon dioxide of a
median of 2.3 °C and uncertainty 1.7–2.6 °C (66% probability range), less than the earlier estimates of 2 to 4.5 °C as the 66% probability range. Schmittner et al. said their "results imply less probability of extreme climatic change than previously thought." Their work suggests that climate sensitivities >6 °C "cannot be reconciled with paleoclimatic and geologic evidence, and hence should be assigned near-zero probability."[28][29]
Other experimental estimates
Idso (1998)[30] calculated based on eight natural experiments a ? of 0.1 °C/(Wm?2) resulting in a
climate sensitivity of only 0.4 °C for a doubling of the concentration of CO2 in the atmosphere.
Andronova and Schlesinger (2001) found that the climate sensitivity could lie between 1 and 10 °C, with a 54 percent likelihood that it lies outside the IPCC range.[31] The exact range depends on which factors are most important during the instrumental period: "At present, the most likely scenario is one that includes anthropogenic sulfate aerosol forcing but not solar variation. Although the value of the climate sensitivity in that case is most uncertain, there is a 70 percent chance that it exceeds the maximum IPCC value. This is not good news," said Schlesinger.
Forest, et al. (2002)[32] using patterns of change and the MIT EMIC estimated a 95% confidence interval of 1.4–7.7 °C for the climate sensitivity,
and a 30% probability that sensitivity was outside the 1.5 to 4.5 °C range.
Gregory, et al. (2002)[33]
estimated a lower bound of 1.6 °C by estimating the change in Earth's radiation budget and comparing it to the global warming observed over the 20th century.
Shaviv (2005)[34] carried out a similar analysis for 6 different time scales, ranging from the 11-yr solar cycle to the climate variations over geological time scales. He found a typical sensitivity of 0.54±0.12 K/(W m?2)
or 2.1 °C (ranging between 1.6 °C and 2.5 °C at 99% confidence) if there is no cosmic-ray climate connection, or a typical sensitivity of 0.35±0.09 K/(W m?2) or 1.3 °C (between 1.0 °C and 1.7 °C at 99% confidence), if the cosmic-ray climate link is real. (Note Shaviv quotes a radiative forcing equivalent of 3.8 Wm?2. [?Tx2=3.8 Wm?2 ?].)
Frame, et al. (2005)[35] noted that the range of the confidence limits is dependent on the nature of the prior assumptions made.
Annan and Hargreaves (2006)[36] presented an estimate that resulted from combining prior estimates based on analyses of paleoclimate, responses to volcanic eruptions, and the temperature change in response to forcings over the twentieth century. They also introduced a triad notation (L, C, H) to convey the probability distribution function (pdf) of the sensitivity, where the central value C indicates the maximum likelihood estimate in degrees Celsius and the outer values L and H represent the limits of the 95% confidence interval for a pdf, or 95% of the area under the curve for a likelihood function. In this notation their estimate of sensitivity was
(1.7, 2.9, 4.9) °C.
Forster and Gregory (2006)[37] presented a new independent estimate based on the slope of a plot of calculated greenhouse gas forcing minus top-of-atmosphere energy imbalance, as measured by satellite borne radiometers, versus global mean surface temperature. In the triad notation of Annan and Hargreaves their estimate of sensitivity was
(1.0, 1.6, 4.1) °C.
Royer, et al. (2007)[38] determined climate sensitivity within a major part of the Phanerozoic. The range of values
—1.5 °C minimum, 2.8 °C best estimate, and 6.2 °C maximum—is, given various uncertainties, consistent with sensitivities of current climate models and with other determinations.[39]
Lindzen and Choi (2011)
find the equilibrium climate sensitivity to be 0.7 C, implying a negative feedback of clouds.[40]
Skeie et al. (2013) use the Bayesian analysis of the OHC data and conclude
that the equilibrium climate sensitivity is 1.8 C, far lower than previous best estimate relied upon by the IPCC.[41]
Aldrin et al. (2012) use a simple deterministic climate model, modelling yearly hemispheric surface temperature and global ocean heat content as a function of historical radiative forcing and combine it with an empirical, stochastic model.
By using a Bayesian framework they estimate the equilibrium climate sensitivity to be 1.98 C.[42]
Lewis (2013) estimates by using the Bayesian framework that the equilibrium
climate sensitivity is 1.6 K, with the likely range (90% confidence level) 1.2-2.2 K.[43]
ScienceDaily reported on a study by Fasullo and Trenberth (2012),[44] who tested model estimates of climate sensitivity based on their ability to reproduce observed relative humidity in the tropics and subtropics. The best performing models tended to project relatively high
climate sensitivities, of around 4 °C.[44]
Previdi et al. 2013 reviewed the 2×CO2 Earth system sensitivity, and concluded it is higher if the ice sheet and the vegetation albedo feedback is included in addition to the fast feedbacks,
being ?4–6 °C, and higher still if climate–GHG feedbacks are also included.[45]
Lewis and Curry (2014) estimated that equilibrium
climate sensitivity was 1.64 °C, based on the 1750-2011 time series and "the uncertainty ranges for forcing components" in the IPCC's Fifth Assessment Report.[46]
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