Daily Archives: June 7, 2016

A Case for Pro-Brexit

happy-bouncing-smilie

“If there are two better reasons for voting Leave in the referendum, I’m hard pushed to think of them.” click here for one person’s view

Schmidt Analysis Actually Confirms Discrepancy between Model Estimates and Mesaured Temperatures

For those of you who wonder about the discrepancies between global model estimates and measured global temperatures and are not afraid of the deep weeds of mathematics and statistics this post by Steve McIntyre is well worth reading. Ever since John Christy presented graphs like the one below his analyses have been under assault. McIntyre’s post comments on and responds to the latest counter analysis put forward by Gavin Schmidt. It seems that Mr. Schmidt has confused bias with uncertainty. The two are not the same.

Pages from christyjr_epa_2014_publiccomment  

Drought Predictions Unsupported, Overstated

P. C. D. Milly, K. A. Dunne. Potential evapotranspiration and continental drying Nature Climate Change (2016) doi:10.1038/nclimate3046

By various measures (drought area1 and intensity2, climatic aridity index3, and climatic water deficits4), some observational analyses have suggested that much of the Earths land has been drying during recent decades, but such drying seems inconsistent with observations of dryland greening and decreasing pan evaporation5. ‘Offline analyses of climate-model outputs from anthropogenic climate change (ACC) experiments portend continuation of putative drying through the twenty-first century3, 6, 7, 8, 9, 10, despite an expected increase in global land precipitation9. A ubiquitous increase in estimates of potential evapotranspiration (PET), driven by atmospheric warming11, underlies the drying trends4, 8, 9, 12, but may be a methodological artefact5. Here we show that the PET estimator commonly used (the Penman–Monteith PET13 for either an open-water surface1, 2, 6, 7, 12 or a reference crop3, 4, 8, 9, 11) severely overpredicts the changes in non-water-stressed evapotranspiration computed in the climate models themselves in ACC experiments. This overprediction is partially due to neglect of stomatal conductance reductions commonly induced by increasing atmospheric CO2 concentrations in climate models5. Our findings imply that historical and future tendencies towards continental drying, as characterized by offline-computed runoff, as well as other PET-dependent metrics, may be considerably weaker and less extensive than previously thought.

Additional discussion at WUWT

Why Global Warming will not Affect Antarctica

For a layman’s explanation click here.

Kyle C. Armour, John Marshall, Jeffery R. Scott, Aaron Donohoe, Emily R. Newsom. Southern Ocean warming delayed by circumpolar upwelling and equatorward transport. Nature Geoscience (2016) doi:10.1038/ngeo2731

The Southern Ocean has shown little warming over recent decades, in stark contrast to the rapid warming observed in the Arctic. Along the northern flank of the Antarctic Circumpolar Current, however, the upper ocean has warmed substantially. Here we present analyses of oceanographic observations and general circulation model simulations showing that these patterns—of delayed warming south of the Antarctic Circumpolar Current and enhanced warming to the north—are fundamentally shaped by the Southern Ocean’s meridional overturning circulation: wind-driven upwelling of unmodified water from depth damps warming around Antarctica; greenhouse gas-induced surface heat uptake is largely balanced by anomalous northward heat transport associated with the equatorward flow of surface waters; and heat is preferentially stored where surface waters are subducted to the north. Further, these processes are primarily due to passive advection of the anomalous warming signal by climatological ocean currents; changes in ocean circulation are secondary. These findings suggest the Southern Ocean responds to greenhouse gas forcing on the centennial, or longer, timescale over which the deep ocean waters that are upwelled to the surface are warmed themselves. It is against this background of gradual warming that multidecadal Southern Ocean temperature trends must be understood.