Wie funktionierte das Klima im Eozän?

Das frühe Eozän vor 50 Millionen Jahren wird immer gerne als Beweis dafür angeführt, dass das CO2 ein äußerst stark erwärmendes Klimagas wäre. Wenn man sich dann etwas tiefer in die Literatur einliest, wird schnell klar, dass hier noch sehr viele Fragen offen sind. Unter anderem können viele Modelle die Eozän-Hitze nur unter Annahme extrem hoher CO2-Konzentrationen modellieren, die jedoch fernab der Wirklichkeit liegen, wenn man sich die geologischen CO2-Rekonstruktionen betrachtet. Henrik Carlson und Rodrigo Caballero von der Universität Stockholm haben nun in einem Artikel eine Alternative ausgelotet: Wie wäre es, wenn ein Großteil der Erwärmung nicht auf das Konto vom CO2, sondern durch Ausdünnen der Wolken verursacht worden wäre? Eine spannende Geschichte, die starken Einfluss auf die wichtige Frage der CO2-Klimasensitivität hat. Hier der Abstract aus Climate of the Past Discussions, erschienen Mitte Februar 2017:

Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene
Recent work in modelling the warm climates of the Early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO2 concentrations or more modest CO2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth’s climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO2, and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the low CO2-thin clouds or LCTC scenario) . The two simulations have almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has ~ 11 % greater global-mean precipitation. The LCTC simulation also has cooler midlatitude continents and warmer oceans than the high-CO2 scenario, and a tropical climate which is significantly more El Niño-like. We discuss the potential implications of these regional changes for terrestrial hydroclimate and vegetation.


Sie haben schon einmal von Watergate gehört? Na klar. Und Sie kennen als Klimainteressierter natürlich auch die Climategate-Episode. Nun gibt es nicht nur bei den Klimawissenschaften Aktivisten und Interessenskonflikte, sondern auch bei der Bienenzucht. Genau, Sie haben richtig gehört, Bienenzucht. Der dazugehörige Skandal heißt entsprechend Beegate. Interesse geweckt? Im Risk Monger-Blog können Sie den Fall nachlesen, mit vielen Parallelen und sogar Berührungspunkten zur Klimadiskussion:


Almost ten years ago, when there were indications of stresses on honeybee populations (known as colony collapse disorder – CCD), different activists were jockeying for the right to claim this crisis for their campaigns. Climate activists wanted to show bees were suffering because of warmer weather; biodiversity campaigners saw land-use issues as the source for the crisis; anti-GMO stalwarts wanted us to know there was something unknown in the pollen; anti-EMF  fear-mongers wanted to highlight the confusion bees suffered due to our love of mobile technology. Nobody mentioned the main causes (cold winters and Varroa mite) … seriously, who would donate to that???

In an early blog, the Risk-Monger had predicted that the anti-pesticides lobby would win this issue as their own … and how right he was! It doesn’t matter that there was no science behind the bees and pesticides campaigns; it doesn’t matter that the campaigners lied and fear-mongered their way to the top; it doesn’t matter that farmers, the environment and bees suffered from the consequences of their self-serving dogmatic bias. The organic food lobby, that funded these cosmopolitan zealots, focused the campaign on the most advanced, least detrimental line of crop protection products: neonicotinoids (neonics)

Watching this crisis unfold, the Risk-Monger saw an enormous amount of unethical, unscientific and unacceptable behaviour from the save-the-bees groups. This is the story of BeeGate – how activist scientists and seasoned campaigners used Age of Stupid tactics to trick policymakers, seduce the media and terrify the public – litigious liars and lamentable fear-mongers have caused incomprehensible damage to the public trust in dialogue, science and policy. Winning might be everything to these activists, but destroying food security and trust in policy and science hardly merits such hypocrisy!

In 2014, I leaked a confidential activist strategy document that showed how a group of anti-pesticide scientists aligned with the IUCN conspired to ban neonics – putting policy first and looking for evidence later. That was only the first part of the scandal. I then showed in Part 2 how the scientists were conflicted and funded by interest groups that would benefit from an increase in organic food sales. After that I revealed how activists worked their way onto the EFSA Bee Risk Assessment Working Group to game the RA process to ensure that the available field trial data would not comply, leading to EFSA’s limited advice that would result in a precautionary ban on neonicotinoids.

Weiterlesen im Risk Monger-Blog


Der Newsletter ‘Klarsicht’ ist im Februar 2017 mit seiner zweiten Ausgabe erschienen, in der es vor allem um das vorindustrielle Klima der Vorzeit geht. Lesenswert! Das kostenlose pdf des Heftes finden Sie hier.