Klimarealister, arkæologi og the Heartland Institute

Det betyder jo, at isen den gang, f.eks. for 4000 år siden, har været trukket længere tilbage, end den er nu. Det må jo så også betyde, at jordens temperatur den gang var højere, end den er nu. Fundene viser, at sne og is er kommet og gået på de steder hen over årtusinderne.

Det betyder jo så igen, at den opvarmning, vi observerer i vores tid, nok ikke er "uden fortilfælde", som man ellers ønsker at hævde.

De danske klimarealister skriver

Det betyder jo, at isen den gang, f.eks. for 4000 år siden, har været trukket længere tilbage, end den er nu. Det må jo så også betyde, at jordens temperatur den gang var højere, end den er nu. Fundene viser, at sne og is er kommet og gået på de steder hen over årtusinderne.

Det betyder jo så igen, at den opvarmning, vi observerer i vores tid, nok ikke er "uden fortilfælde", som man ellers ønsker at hævde.

Jeg er ikke i stand til at afgøre sandhedsværdien af dette udsagn.

Peter Villadsen skrev:
Man ser tydeligt, at det kun var lidt varmere end nu. De temperaturstigninger vi går mod i dette århundrede overgår de temperaturer, der er set siden sidste istid.

delphi skrev:

Peter Villadsen skrev:
Man ser tydeligt, at det kun var lidt varmere end nu. De temperaturstigninger vi går mod i dette århundrede overgår de temperaturer, der er set siden sidste istid.

Suk!

Summary: Holocene climate is characterized by two initial millennia of fast warming followed by four millennia of higher temperatures and humidity, and a progressively accelerating cooling and drying for the past six millennia. These changes are driven by variations in the obliquity of the Earth's axis. The four millennia of warmer temperatures are called the Holocene Climatic Optimum which was 1-2°C warmer than the Little Ice Age. This climatic optimum was when global glaciers reached their minimum extent. The Mid-Holocene Transition, caused by orbital variations, brought a change in climatic mode, from solar to oceanic dominated forcing. This transition displaced the climatic equator, ended the African Humid Period and increased El Niño activity.

delphi skrev:
Fjolser der lever i den vildfarelse at tro der har været et temperaturspænd over de sidste 10.000 år i niveauet 0,4 grad - det er jo til at åbne og sk*** i.

Paleoclimatologists have long suspected that the "middle Holocene," a period roughly from 7,000 to 5,000 years ago, was warmer than the present day. Terms like the Altithermal or Hypsithermal or Climatic Optimum have all been used to refer to this warm period that marked the middle of the current interglacial period. Today, however, we know that these terms are obsolete and that the truth of the Holocene is more complicated than originally believed.

What is most remarkable about the mid-Holocene is that we now have a good understanding of both the global patterns of temperature change during that period and what caused them. It appears clear that changes in Earth's orbit have operated slowly over thousands and millions of years to change the amount of solar radiation reaching each latitudinal band of Earth during each month. These orbital changes can be easily calculated and predict that the Northern Hemisphere should have been warmer than today during the mid-Holocene in the summer and colder in the winter. The combination of warmer summers and colder winters is apparent for some regions in the proxy records and model simulations. There are some important exceptions to this pattern, however, including colder summers in the monsoon regions of Africa and Asia due to stronger monsoons with associated increased cloud cover during the mid-Holocene, and warmer winters at high latitudes due to reduction of winter sea ice cover caused by more summer melting.

In summary, the mid-Holocene, roughly 6,000 years ago, was generally warmer than today during summer in the Northern Hemisphere. In some locations, this could be true for winter as well. Moreover, we clearly know the cause of this natural warming, and we know without doubt that this proven "astronomical" climate forcing mechanism cannot be responsible for the warming over the last 100 years.

Jørgen Petersen skrev:
Med andre ord var det væsentligt varmere unde Holocæn Klimatisk Optima end nu. Det kan man tydeligt se ud fra de planter og dyr som levede dengang.

Årsagen til denne opvarmning er sådan set ligegyldig. Det afgørende er, at denne varme var der, og at denne varme var en kæmpe fordel for såvel planter, dyr og mennesker.

Nedenfor ses estimering af opvarmningen for forskellige breddegrader.

Under Holocæn Klimatisk Optima

Peter Villadsen skrev:
Der er med hensyn til vandstandsstigninger ingen sammenligning mellem drivhusgas opvarmning som vi ser nu og opvarmningen i Holoceme.
Baggrunden er som tidligere vist, at Holocen opvarmningen hovedsageligt var på højere breddegrader på den nordlige halvkugle, hvor den nuværende opvarmning er global.

Så ingen sammenligning mulig - det er helt indlysende.