In den Klimamodellen ist die Erde immer noch eine Scheibe

Wussten Sie, dass alle Klimamodelle bisher eine flache Erde annehmen? Schwer zu glauben, aber leider wahr. Eine Studie von Michael Prather und Juno Hsu in PNAS erläutert, dass durch diese Vereinfachung in den Computersimulationen mächtige Verzerrungen auftreten:

A round Earth for climate models

Sunlight drives the Earth’s weather, climate, chemistry, and biosphere. Recent efforts to improve solar heating codes in climate models focused on more accurate treatment of the absorption spectrum or fractional clouds. A mostly forgotten assumption in climate models is that of a flat Earth atmosphere. Spherical atmospheres intercept 2.5 W⋅m−2 more sunlight and heat the climate by an additional 1.5 W⋅m−2 globally. Such a systematic shift, being comparable to the radiative forcing change from preindustrial to present, is likely to produce a discernible climate shift that would alter a model’s skill in simulating current climate. Regional heating errors, particularly at high latitudes, are several times larger. Unlike flat atmospheres, constituents in a spherical atmosphere, such as clouds and aerosols, alter the total amount of energy received by the Earth. To calculate the net cooling of aerosols in a spherical framework, one must count the increases in both incident and reflected sunlight, thus reducing the aerosol effect by 10 to 14% relative to using just the increase in reflected. Simple fixes to the current flat Earth climate models can correct much of this oversight, although some inconsistencies will remain.

Significance

Early climate and weather models, constrained by computing resources, made numerical approximations on modeling the real world. One process, the radiative transfer of sunlight through the atmosphere, has always been a costly component. As computational ability expanded, these models added resolution, processes, and numerical methods to reduce errors and become the Earth system models that we use today. While many of the original approximations have since been improved, one—that the Earth’s surface and atmosphere are locally flat—remains in current models. Correcting from flat to spherical atmospheres leads to regionally differential solar heating at rates comparable to the climate forcing by greenhouse gases and aerosols. In addition, spherical atmospheres change how we evaluate the aerosol direct radiative forcing.

Die Autoren betonen, dass die dadurch entstehenden Fehler in der Größenordnung des Treibhausgasantriebs liegen. So werden die solare Einstrahlung und das Aerosol- Forcing verfälscht. 

Wenn also in Zukunft jemand unbequeme Klimakritiker wieder als „Flachwelt-Anhänger“ persönlich beschimpft, ist die Antwort im Prinzip klar: Die wirklichen „Flat Earther“ sind die Klimamodellierer, die durch ihre eingeschränkte Computerrechenleistung noch immer flache Welten simulieren, dies aber bislang nicht an die große Glocke hängten…