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Metropolitan State University of Denver Meteorology Professor, Keah Schuenemann, explains:

“The IPCC is organized by the United Nations. Since 1990, they’ve produced five [major] reports [and recent ‘Synthesis Reports’ prepared in advance of the 2022 IPCC ‘Sixth Assessment Report’]. Each [Assessment] “report” is actually a series of books, each almost 1000 pages. The books cover the physical science, the impacts adaptation and vulnerability, and the mitigation of climate change. The IPCC includes climate models from more than twenty different climate laboratories around the world, each with their own supercomputers. Each lab’s model is written independently from the others. They come from China, Norway, the United States, Canada, France, Australia, Germany, Korea, Russia, Japan, and the United Kingdom!

Photo of IPCC Reports
Photo of IPCC Reports, By IPCC used under the fair use standard.

“The IPCC puts the report through a rigorous review process where each sentence is scrutinized. It produces a report that all authors agree on, and that the governments of the member countries agree on. Because of this process, the IPCC reports tend to err on the side of being conservative.

“Here are three examples of the IPCC being conservative. First off, they’ve tended to underestimate how much greenhouse gases we’ll emit. In fact, the carbon dioxide concentration and emission rates measured in the last few years indicate that we are currently on the “worst case scenario” path. This suggests that the IPCC should adjust its scenarios to give a better sample of future emissions in order to imagine a worse worst-case, which it has done for the most recent [IPCC5] report.

Graph of Artic Sept ice extent
Graph from National Snow & Ice Data Center, nsdc.org/icelights/files/2011/02/Decline_chart.png, (CC) by-SA.

“The second example is Arctic sea ice decline. The area of ice covering the Arctic Ocean has been getting pretty small at the end of summer these days. Whenever this bright white ice melts, it reveals a darker ocean surface underneath it.

Graphic of sun's rays bouncing off open artic ocean.
Graphic of sun’s rays bouncing off open arctic ocean. PD by NASA SVS,

Dark ocean water absorbs more sunlight, making the system even warmer and melting even more ice. This is an amplifying feedback. If we graph the Arctic ice area at the end of summer each year, we find it’s decreasing *much quicker* than any climate model projected! This signifies that all of the climate models have underestimated the strength of this self-reinforcing cycle.

Chart of Sea Level Rise models v observations
Sea Level Rise Models vs. Observations, John Cook photo from sks.to/graphics, (CC) by SA

“The last example is sea level rise. Measurements indicate that sea level rise is accelerating faster than projected by climate models. Most recently, the IPCC estimate was 60% below the observed trend. When the fourth report of the IPCC came out, scientists studying glaciers had begun to report that their flow of ice discharge to the ocean was accelerating. Some glaciers were accelerating, others were not, and we didn’t really know why.

Photo of Moulin in Greenland
Moulin in Greenland drains glacial melt-water. Photo from NASA, NSIC, commons.wikimedia.org/, (CC) 0.

Giant meltwater lakes and drainage holes called moulins were observed on the Greenland ice sheet and fears were that the water might be getting to the ground, lubricating the ice sheet and its glaciers and causing it to accelerate its melt. Rather than include these dynamic ice melting processes in their sea level rise projections, the IPCC scientists decided they didn’t have enough information to include this effect properly. So they left it out entirely. This is a good example of their erring on the side of caution.”

Despite the cautious approach to stating scientific fact of the IPCC, one myth distorts the evidence by contending that IPCC reports are alarmist, using inaccurate climate models to exaggerate the danger of global warming in order to cause needless worry. This myth uses the technique of adopting a conspiracy theory in an attempt to discredit your opponents. That is, some people believe the scientists of the IPCC are conspiring to trick people about the effects of global warming. If that were true, it would require collusion between 20 climate laboratories in several countries.

The Fifth  IPCC Report cited 9200 scientific publications. It was drafted by 809 lead and contributing authors (including Montana’s own Dr. Steve Running, retired Regents Professor, Global Ecology, University of Montana who was a Chapter Author of the Intergovernmental Panel on Climate Change when it was awarded the Nobel Peace Prize in 2007), and went through three major iterations over three years after review by 1,089 scientific experts/editors who considered 54,677 comments before the Summary Report was finalized line by line by officials from 195 member governments. If those folks were all conspiring to trick people about the effects of global warming, it would be quite a conspiracy.

This “alarmist accusation myth” also uses cherry picking by citing isolated examples where the IPCC overestimated climate impacts. Dr. Schuenemann acknowledges, “There have been a few examples where the IPCC overestimated climate impacts. But overall, the cautious approach of the IPCC means it’s been systematically underestimating climate impacts.”

In reality, as authors of the peer reviewed article “Climate change prediction: Erring on the side of least drama?” discovered, the IPCC is 20 times more likely to underestimate rather than exaggerate climate impacts.

So, the accusations that the IPCC has been alarmist are themselves exaggerated.

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Page last updated 2/9/2020.



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