30 January 2013
A paper recently published in Global Environmental Change by Brysse, et al., (2012) examined a number of past predictions made by climate scientists, and found that that they have tended to be too conservative in their projections of the impacts of climate change. The authors thus suggest that climate scientists are biased toward overly cautious estimates, erring on the side of less rather than more alarming predictions, which they call "erring on the side of least drama" (ESLD).
In this paper, Brysse et al. examined research evaluating past climate projections, and considered the pressures which might cause climate scientists to ESLD.
Conservative Climate Projections
While we have recently shown that the Intergovernmental Panel on Climate Change (IPCC) temperature projections have been exceptionally accurate, several other projections in the IPCC reports have been far too conservative.
Sea Level Rise
For example, Rahmstorf (2007) and more recently Rahmstorf et al. (2012) showed that sea level is rising at a rate inconsistent with all but the highest IPCC scenarios (Figure 1). Rahmstorf et al. (2012) concluded, “The satellite-based linear trend 1993–2011 is 3.2 ± 0.5 mm yr-1, which is 60% faster than the best IPCC estimate of 2.0 mm yr-1 for the same interval.”
The main reason these sea level rise projections have been too low and that the IPCC almost certainly underestimates future sea level rise is that their models do not include the effects of dynamic ice processes from chunks of ice breaking off into the ocean ("calving"), then melting. The IPCC approach in attempting to account for these processes considers recent contributions to sea level rise from ice sheet melt, then "assume that this contribution will persist unchanged." This is certainly a conservative approach, and the primary reason their sea level projections have been low. [more]