Klimamodellerne forkerte?

Frank123 skrev:
@Jørgen Petersen

Ja du har fuldkommen ret.

Det jeg finder interessant er at nu er det officielt fra dansk side, DMI og selveste Klimaforsker Martin Stendel, at klimamodellerne er forkerte og vi får ovenikøbet også forklaringen på hvorfor de er forkerte.

Climate models published since 1973 have generally been quite skillful in projecting future warming. While some were too low and some too high, they all show outcomes reasonably close to what has actually occurred, especially when discrepancies between predicted and actual CO2 concentrations and other climate forcings are taken into account.

Models are far from perfect and will continue to be improved over time. They also show a fairly large range of future warming that cannot easily be narrowed using just the changes in climate that we have observed.

Nevertheless, the close match between projected and observed warming since 1970 suggests that estimates of future warming may prove similarly accurate.

The latest assessment report from the Intergovernmental Panel on Climate Change (IPCC) estimates that climate sensitivity has a "likely" range of 1.5 to 4.5C.

The new study, published in Nature, refines this estimate to 2.8C, with a corresponding range of 2.2 to 3.4C. If correct, the new estimates could reduce the uncertainty surrounding climate sensitivity by 60%.

The narrower range suggests that global temperature rise is "going to shoot over 1.5C" above pre-industrial levels, the lead author tells Carbon Brief, but "we might be able to avoid 2C". Meeting either limit will likely require negative emissions technologies that can remove CO2 from the atmosphere, he says.

The new estimate is another "brick in the wall" of scientists' understanding of climate sensitivity, another scientist tells Carbon Brief, and "the best-informed views will be reached by multiple lines of evidence".

New study on climate sensitivity not what poor media headlines, deniers are saying

Emergent constraint on equilibrium climate sensitivity from global temperature variability

Earth to warm 2 degrees Celsius by the end of this century, studies say

One study used statistical analysis to show that there is a 95% chance that Earth will warm more than 2 degrees at century's end, and a 1% chance that it's below 1.5 C.

Kjeld Jul skrev:
Niels-
Nogle forskere mener at klimasensiviteten er ubetydelig,men det er fåtallet. Flere forskninger og simple regneeksempler indikerer, at den blot er mindre end tidligere antaget.
Det har jeg også skrevet en del om i en anden tråd
Men lad os nu se temperatur udviklingen de næste dekader.
Klimamodeller skal man tage med forbehold - det er det belæg for.

Climate sensitivity in its most basic form is defined as the equilibrium change in global surface temperature that occurs in response to a climate forcing, or externally imposed perturbation of the planetary energy balance. Within this general definition, several specific forms of climate sensitivity exist that differ in terms of the types of climate feedbacks they include. Based on evidence from Earth's history, we suggest here that the relevant form of climate sensitivity in the Anthropocene (e.g. from which to base future greenhouse gas (GHG) stabilization targets) is the Earth system sensitivity including fast feedbacks from changes in water vapour, natural aerosols, clouds and sea ice, slower surface albedo feedbacks from changes in continental ice sheets and vegetation, and climate-GHG feedbacks from changes in natural (land and ocean) carbon sinks. Traditionally, only fast feedbacks have been considered (with the other feedbacks either ignored or treated as forcing), which has led to estimates of the climate sensitivity for doubled CO2 concentrations of about 3°C. The 2×CO2 Earth system sensitivity is higher than this, being ∼4-6°C if the ice sheet/vegetation albedo feedback is included in addition to the fast feedbacks, and higher still if climate-GHG feedbacks are also included. The inclusion of climate-GHG feedbacks due to changes in the natural carbon sinks has the advantage of more directly linking anthropogenic GHG emissions with the ensuing global temperature increase, thus providing a truer indication of the climate sensitivity to human perturbations. The Earth system climate sensitivity is difficult to quantify due to the lack of palaeo-analogues for the present-day anthropogenic forcing, and the fact that ice sheet and climate-GHG feedbacks have yet to become globally significant in the Anthropocene. Furthermore, current models are unable to adequately simulate the physics of ice sheet decay and certain aspects of the natural carbon and nitrogen cycles. Obtaining quantitative estimates of the Earth system sensitivity is therefore a high priority for future work.

Jørgen Petersen skrev:
At klimasesitiviteten, som vist i Scafetta-grafen, er blevet kraftigt nedjusteret, kan således kun afvises, hvis du kan påvise konkrete fejl i udarbejdelsen af denne graf. Sådanne fejl er endnu ikke blevet påvist.

Jørgen Petersen skrev:
@ Niels K Sørensen

Den temperaturstigningen, som der har været fra år 1850 til år 1950, var på ca. 1/3 grad, og den har stort set ikke noget med CO2 at gøre. I år 1950 var CO2 indholdet i atmosfæren på ca. 300 ppm, hvorfor stigningen i CO2 indholdet fra 1865 til 1950 kun var på ca. 20 ppm. Dette kan umuligt skabe nogen nævneværdig temperaturstigning. Den resterende stigning i atmosfærens CO2 indhold, som var på ca. 110 ppm, burde i så fald have forårsaget en langt langt langt kraftigere stigning i temperaturen end hvad vi konkret har oplevet i perioden fra 1950 til i dag.

I øvrigt vil afvigelser imellem hvad en prognose siger og hvad den faktiske virkelighed viser, altid skyldes fejl i prognoserne. Virkeligheden er som den er. Dette betyder, at du kun kan afvise Scafetta-grafen, hvis du kan påvise konkrete fejl i udarbejdelsen af denne graf. Teoretisk ævl omkring vanskelighederne ved at beregne den fremtidige udvikling på klimaområdet kan ikke bruges til at afvise Scafetta-grafen.

At klimasesitiviteten, som vist i Scafetta-grafen, er blevet kraftigt nedjusteret, kan således kun afvises, hvis du kan påvise konkrete fejl i udarbejdelsen af denne graf. Sådanne fejl er endnu ikke blevet påvist.

Her ud over er der god grund til at glæde sig over den temperaturstigning, som vi har haft i de sidste 100 eller 200 år, og det ligegyldigt om de er naturlige eller menneskeskabte. Denne temperaturstigning har vi haft meget stor gavn af.