It has some to do with Catastrophic predictions that don't materialize.
#3 | Posted by BellRinger
That's a "science denier" way of thinking.
Several projections from early IPCC reports have not materialized as predicted, primarily due to underestimations of the rate and severity of climate change impacts. The 1990 First Assessment Report (FAR) projected a range of sea-level rise between 8 and 29 cm by 2030 under a business-as-usual scenario, with a best estimate of 18.3 cm; observations closely track this best estimate and lower bound, indicating the projection was reasonably accurate despite some overestimation of greenhouse gas concentrations.
However, the 1995 Second Assessment Report (SAR) projected that the Arctic sea ice pack would remain stable until at least 2050 or beyond, a prediction that has been dramatically contradicted by observations showing the Arctic is on track for an ice-free state in the coming decades.
Similarly, the 1995 SAR and earlier reports projected "little change" in the extent of the Greenland and Antarctic ice sheets over the next 50"100 years, but current ice loss is trending at least 100 years ahead of these projections.
The 2001 report projected a sea-level rise of 2 mm per year and a worst-case scenario of up to 1.9 feet by 2100, based primarily on thermal expansion, but observed sea-level rise has averaged 3.3 mm per year since 1990, with projections now ranging from 2.4 to 6.2 feet by 2100 when ice sheet melt is included.
This underestimation occurred because the IPCC excluded the contribution of melting ice sheets to sea-level rise due to scientific disagreement, a practice described as "consensus by omission".
Furthermore, the 2007 report projected a worst-case temperature rise of 4.3 to 11.5F by 2100, but current projections indicate a rise of 6.3 to 13.3F, with a high probability of 9.4F, largely due to higher-than-expected CO emissions and the omission of feedback mechanisms like permafrost thaw.
While some early projections, such as those for atmospheric CO concentrations in the IS92a scenario from the 1995 SAR, have closely matched observations, the overall trend shows that the IPCC has consistently underestimated the pace of climate change, particularly in areas involving ice sheet dynamics, sea-level rise, and feedback loops.
The most recent assessments have begun to acknowledge these uncertainties and include low-confidence, high-impact scenarios, reflecting a growing recognition of the limitations of earlier models.
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