The Intergovernmental Panel on Climate Change recently requested a figure for its annual report, to show temperature trends over the last 10,000 years there seemed to be an evident problem.
Zhengyu Liu from the University of Wisconsin says that data from observation suggests that the Earth is cooling while the physical data suggests the complete opposite.
The problem has been termed the Holocene temperature conundrum. It has tremendously important implications for understanding climate change and evaluating climate models. The authors have however emphasized that this does not negate the evidence of human impact on global climate beginning in the 20th century. The question however remains, who is right? Liu suggests that maybe none of us are completely right, he suggests a data problems or perhaps a model problem, for example some physical mechanisms may be missing from the model.
Liu says that they are certain that during the last 10,000 years, atmospheric carbon dioxide rose by 20 parts per million before the 20th century. He thinks that these physical changes suggest that, the annual mean temperature should have continued to warm, even as regions around the world experienced cooling.
Liu and his colleagues created three models which took two years to complete, they ran simulations of climate influences that spanned from the intensity of sunlight on Earth to global greenhouse gases, ice sheet cover and meltwater changes. Each indicates global warming over the last 10,000 years. However, the bio and geo-thermostats used in last year’s study in the journal Science indicates global cooling beginning around 7000 years ago and continuing until the mark of humans became apparent. Liu says, in the North Atlantic there is cooling and warming data that the climate change community has not been able to figure out. Liu thinks that with the current knowledge in perspective, it is difficult to imagine any physical forces in the last 10,000 years that could have been strong enough to curtail the warming indicated by the increase in global greenhouse gases. Climate scientists are to meet this fall to discuss this baffling issue.
