Definite Evidence Found that Human-Caused Climate Change is Affecting the Seasons
In the July issue of Science magazine, a group of climate scientists — Benjamin D. Santer, Stephen Po-Chedley, Mark D. Zelinka, Ivana Cvijanovic, Céline Bonfils, Paul J. Durack, Qiang Fu, Jeffrey Kiehl, Carl Mears, Jeffrey Painter, Giuliana Pallotta, Susan Solomon, Frank J. Wentz, and Cheng-Zhi Zou — reported that anthropogenic (human-caused) climate change has become clearly observable, and that a human-caused signal in the seasonal cycle of tropospheric temperature can also be measured. They use satellite data and the anthropogenic “fingerprint” predicted by climate models — based on studies that use pattern information to separate human and natural influences on climate — to show the extent of these human-caused effects. They conclude that human influences are identifiable in the changing seasonal cycle.
They wrote: “At least three lines of evidence suggest that human activities have affected the seasonal cycle. First, there are seasonal signals in certain human-caused external forcings, such as stratospheric ozone depletion and particulate pollution. Second, there is seasonality in some of the climate feedbacks triggered by external forcings. Third, there are widespread signals of seasonal changes in the distributions and abundances of plant and animal species. These biological signals are in part mediated by seasonal climate changes arising from global warming. All three lines of evidence provide scientific justification for performing ‘fingerprint’ studies with the seasonal cycle.”
Their studies showed that “the model fingerprint of externally forced seasonal cycle changes is identifiable with high statistical confidence in five out of six satellite temperature datasets.” The evidence of human-caused temperature increases and other climate change far outweighs any normal variation or random fluctuations. They conclude that their “results suggest that attribution studies with the seasonal cycle of tropospheric temperature provide powerful and novel evidence for a statistically significant human effect on Earth’s climate. We hope that this finding will stimulate more detailed exploration of the seasonal signals caused by anthropogenic forcing.”
Previously Friederike Otto, an associate professor at the University of Oxford’s Climate Research Programme had said, “There are a lot of observations that the seasonal cycle is changing, and it is also one of the things that is most noticeable in everyday life with trees flowering earlier.” She claimed that “so far this has been tricky to disentangle formally and with high statistical significance from natural variability.” The study by Santer, et al begins to provide that ‘high statistical significance’ that validates the testimonies of indigenous peoples in many areas of the world about changing seasons and resulting mismatches of animal and plant life because of the rapidity of human-caused climate change. Over a decade ago, indigenous people in Greenland discussed on KPFK’s “American Indian Airwaves,” the fact that they could hear water running under the ice-cap in the winter! Now science has validated that such unnatural changes are due to human-caused impacts on the climate, mainly through so-called “greenhouse gas” emissions, such as CO2 and methane, that trap solar heat in the atmosphere.–Summary by Michael Novick for Change Links