Climate scientists have long been building models and analyzing available data to determine the effect of human activity on the global environment, but what about the time before humans? Was Earth in a warming or cooling period before human activity became a factor?
A new study calls the evidence that's available to answer this question a "climate conundrum."
Zhengyu Liu with the University of Wisconsin, Madison, and his colleagues at other institutions began looking into this topic further when the Intergovernmental Panel on Climate Change approached them for information for its annual report.
“We have been building models and there are now robust contradictions,” Liu said in a statement. “Data from observation says global cooling. The physical model says it has to be warming.”
The study published this week by Liu and other researchers in the Proceedings of the National Academy of Sciences found a consistent trend of warming in the current Holocene epoch, which covers the present to the last 11,700 years. Their findings are contrary to other studies that indicated the Earth was cooling before humans came on the scene.
This, according to the university's news release, is the Holocene temperature conundrum.
“The question is, ‘Who is right?’” Liu said. “Or, maybe none of us is completely right. It could be partly a data problem, since some of the data in last year’s study contradicts itself. It could partly be a model problem because of some missing physical mechanisms.”
One of these mechanisms, according to the news release, is volcanic activity. But the study authors said there is not enough evidence to support that volcanic activity during this epoch would have contributed to major cooling.
While information about the state of the climate before human activity can help scientists create improved climate models for future predictions, the study authors said that it doesn't change stance the majority of the scientific community holds regarding humanity's impact on climate change in the 20th century.
Given the discrepancy over whether the Earth was warming or cooling 10,000 years ago, Liu told the university that scientists will be meeting this fall to "look back critically and see what is missing."
"I think it is a puzzle," Liu said.
In other climate change news, Yale's Environment blog cited a recent study that says the media gives a disproportionate voice to those who are skeptical of man-made global warming. A study published last month in the journal Environmental Science and Technology surveyed more than 1,800 scientists, 90 percent of whom agreed that greenhouse gases as a result of human activity is the "dominant driver of recent global warming."
The respondents were also asked about the number of times they are contacted by the media. According to the study, those who consider humanity's impact on climate change "insignificant" seemed to have the most media coverage about their viewpoint on climate change.
(H/T: Tech Times via Reddit)
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