Archive for July, 2015

New observational hint at max. 1.3 °C climate sensitivity

July 21, 2015

In a previous blog “CO2 and temperatures: da stelle mer uns janz dumm” I presented a “zero-dollar” model using past global temperatures and CO2 data to estimate the climate sensitivity using the 1850-1945 and 1945-2013 periods, and found the effective climate sensitivity (which should be close to the equilibrium climate sensitivity ECS) to be about 1.34°C.  This means that a doubling of atmospheric CO2 mixing ratio with respect to the pre-industrial level would cause a global warming of at most 1.34°C. This is a number much lower than the “consensus” values of the IPCC which suggest a most probable warming of 3°C (1.5 to 4.5 °C range). Many authors disagree with the IPCC estimation. Lewis and Curry for instance find in their recent paper “The implication for climate sensitivity of AR5 forcing and heat uptake estimation” values of 1.33°C for the transient climate response TCR and 1.25 to 2.45 °C (i.e. a central value of 1.85°C) for the equilibrium climate sensitivity ECS. Let me just recall that the lower TCR gives the heating due to a CO2 doubling at the moment where this doubling occurs (assuming this doubling takes 70 years to realize), whereas the ECS gives the far in the future lying definitive warming if all feed-backs and readjustments are finished. Dr. Roy Spencer from the UAH presented in his blog yesterday a new calculation using the 15 years of data from the CERES instruments which are carried by successive NASA satellites. CERES measures out-going and incoming radiation fluxes (in W/m2), and is the best (and practically only) source for these extremely important data. Dr. Spence found in several previous papers that when the globe changes its surface temperature, the atmosphere reacts with a delay of about 4 months with its changes in radiative flux. So he took the available 15 years of CERES data, computed yearly means and plotted these data versus the 4 month time shifted global temperatures of the HadCRUT4 series, with a linear regression of flux (t) = a*T(t-4) + b (t = time in months). This gives the following figure: spencer_sensitivity_2015 This linear regression tells us that dF = 2.85*dT (a change of global temperature of 1 °C (or 1 K) corresponds to a forcing of 2.85 W/m2 (and vice-versa). The parameter 2.85 represents the climate feedback lambda. Now the effective climate sensitivity ECS is defined as ECS = F2xCO2/lambda where F2xCO2 is the radiative forcing caused by a doubling of atmospheric CO2, and lambda = feedback factor. Let us accept that F2xCO2 = 5.25*ln(2) = 3.71 W/m2; the number 5.35 is the “consensus” value, which remains subject to discussions, but is more or less accepted by both climate alarmists and realists. So we have: ECS = 3.71/2.85 = 1.3 °C When CO2 mixing ratio reaches 560 ppmV (i.e. the double of the concentration at pre-industrial time, about 1850), we should have a total warming of max. 1.3°. As the globe warmed by about 0.8° since that time, there would be max. 0.5° of coming warming in the pipe-line.   Conclusion: All these ECS values derived from observations (and not climate models!) are rather low. Dr. Spencer says that the 1.3°C should be taken as a maximum, and that the real ECS could possibly be much lower (Prof. Lindzen suggested 0.7 – 1°C). Should we worry? No! And should we desperately try to avoid any CO2 emissions? Neither!

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Big geothermal heat flux may aid West Antarctic Ice base melting

July 15, 2015

There is a new very interesting paper by A. Fisher and al. from UC of Santa Cruz on the problem of geothermal heat flux at the base of the West-Antarctic ice sheet. Fisher an his collaborators drilled a 25cm diameter hole through the ice sheet up to the underlying lake Whillans. The red square shows the location of the drilling.

Fisher_paper_01

They  lowered a heavy 200 kg probe with thermistor sensors through the bore hole and the lake water into the mud at the bottom of the lake. This probe partially entered the mud , so that one thermistor was located about 0.8m deep in the mud (TS1), and the other(TBW) just at the interface between the soil and the bottom of the lake. The next table shows the data for two measurements (GT-1 and GT-2):

Fisher_paper_02
The important quantity is the heat-flux q, which is about 280 mW/m2. One part of the heat-flux goes up through the ice sheet, and another one (180 W/m2) essentially causes the ice at the base to melt. This number of 180 seems low, but it corresponds to a melt of approx. 10% of the ice created by snow fall!

The large measured heat-flow comes at a surprise, for usual accepted values for Antarctica (which were derived from various models) are closer to 50 mW/m2.

Fisher_paper_03

So we have here again a nice argument not to neglect measurements, and not to rely exclusively on theoretical modelling. This new paper shows a natural phenomenon contributing to the WAIS (West Antarctica Ice Sheet) melt, and not the usual suspected culprit of (anthropogenic) global warming. It remains to be seen, if other measurements at other locations deliver results pointing in the same direction.

This paper follows one of Amanda Lough showing that large volcanoes exist below the WAIS, and that this volcanic activity may also be a contributor to increasing ice melt.

To conclude, here is a figure from Wikipedia showing the heat fluxes over the full globe: note that this flux is highest at the ocean ridges, as should be expected!

Earth_heat_flow

The total heat power streaming from the interior to the surface of the earth is estimated to be about 46 TW; this has to be compared to 17 TW power released by human activity (see the meteoLCD energy widgets).