This just in: Uncertainty of "CO2 caused" warming is twice IPCC estimates

That would mean that "unequivocal" anthropogenic global warming is no longer "unequivocal."



Just published in Geophysical Research Letters (GRL):



Uncertainties of global warming metrics: CO2 and CH4

Geophysical Research Letters by Andy Reisinger, Malte Meinshausen, Martin Manning and Greg Bodeker





Abstract: We present a comprehensive evaluation of uncertainties in the Global Warming Potential (GWP) and Global Temperature Change Potential (GTP) of CH4, using a simple climate model calibrated to AOGCMs and coupled climate-carbon cycle models assessed in the IPCC Fourth Assessment Report (AR4). In addition, we estimate uncertainties in these metrics probabilistically by using a method that does not rely on AOGCMs but instead builds on historical constraints and uncertainty estimates of current radiative forcings. While our mean and median GWPs and GTPs estimates are consistent with previous studies, our analysis suggests that uncertainty ranges for GWPs are almost twice as large as estimated in the AR4. Relative uncertainties for GTPs are larger than for GWPs, nearly twice as high for a time horizon of 100 years. Given this uncertainty, our results imply the possibility for substantial future adjustments in best-estimate values of GWPs and in particular GTPs.



Also just in from the settled science:

Decadal changes in tropical convection suggest effects on stratospheric water vapor in GRL by George Tselioudis, Eric Tromeur, William B. Rossow and C. S. Zerefos





Analysis of satellite observations of tropical Weather States derived from a cluster analysis of ISCCP cloud property retrievals, shows that the deep convection Weather State increased in frequency from 1983 to about 2000 and remained at a nearly constant level after that. The sharpest deep convection increase occurred between 1993 and 2000. This convection variability is driven by changes that occur in the Indian Ocean and the Western-Central Pacific regions, which are the regions where the majority of deep tropical convection occurs. Analysis modifications to account for satellite coverage changes during the period under examination do not alter these findings. Previous studies showed that stratospheric water vapor increased from 1980 to 2000 and dropped after that to lower levels that persist until today, and that this change could explain part of the recent global temperature variability. Since tropical deep convection is an important mechanism affecting stratospheric water vapor concentrations, the observed decadal changes in tropical deep convection could explain in part the stratospheric water vapor variability patterns.