Monday, January 14, 2013

New paper confirms findings of Lindzen & Spencer of very low climate sensitivity to CO2

A paper under review for Earth System Dynamics uses a novel technique based on satellite data and surface air temperatures to find that global warming due to increased CO2 is is much less than claimed by the IPCC. According to the author, the findings confirm those of Spencer & Braswell and  Lindzen & Choi that a doubling of CO2 levels would only lead to an increase in top of the atmosphere temperature of 0.67°C, or global surface temperature of about 0.18°C, instead of the alleged 3°C claimed by IPCC computer models. 

The observations indicate a climate feedback parameter of 5.5 Wm−2 K−1, which is in very close agreement to that found by Spencer and Braswell (2010) of 6 Wm−2 K−1, as well as that found by Lindzen and Choi (2011). A climate feedback parameter of 5.5 Wm−2 K−1 corresponds to global warming at the surface of only [1 Wm-2]/[5.5 Wm−2 K−1] = 0.18 °C per doubling of CO2 levels [or 3.7/5.5 = 0.67°C at the top of the atmosphere], far less than the 3°C global warming claimed by the IPCC.

From the paper:

"An unusually high value of the climate feedback parameter of 6 Wm−2 K−1 is suggested by the phase plane plots in Spencer and Braswell (2010). This corresponds to a very low climate sensitivity that disagrees with the majority of the other estimations of the climate sensitivity (Knutti and Hegerl, 2008; Randall et al., 2007; Huber et al., 2011). A discussion of the various methods for estimation of the climate sensitivity is beyond the scope of this work. Here we discuss a method for estimating the value of the climate feedback parameter from satellite radiative flux data and leave the question how to relate the result from this method to the equilibrium climate sensitivity to future work."

"Another issue to be considered in future work should be that the large value of the climate feedback parameter according to this work disagrees with much of the literature on climate sensitivity (Knutti and Hegerl, 2008; Randall et al., 2007; Huber et al., 2011). However, the value found here agrees with the report by Spencer and Braswell (2010) that whenever linear striations were observed in their phase plane plots the slope was around 6 Wm−2 K−1. Spencer and Braswell (2010) used middle tropospheric temperature anomalies and although they did not consider any time lag they may have observed some feedback processes with negligible time lag considering that the tropospheric temperature is better correlated to the radiative flux than the surface air temperature. The value found in this study also agrees with Lindzen and Choi (2011) who also considered the effects of lead-lag relations."

Earth Syst. Dynam. Discuss., 4, 25-47, 2013

Estimation of the climate feedback parameter by using radiative fluxes from CERES EBAF

P. Björnbom
KTH Royal Institute of Technology, c/o Pehr Björnbom, Kometvägen 1, 18333 Täby, Sweden
 Abstract. Top-of-the-Atmosphere (TOA) net radiative flux anomalies from Clouds and Earth's Radiant Energy Systems (CERES) Energy Balanced and Filled (EBAF) and surface air temperature anomalies from HadCRUT3 were compared for the time interval September 2000–May 2011. In a phase plane plot with the radiative flux anomalies lagging the temperature anomalies with 7 months the phase plane curve approached straight lines during about an eight months long period at the beginning and a five year period at the end of the interval. Both of those periods, but more clearly the latter one, could be connected to the occurrence of distinct El Niño Southern Oscillation (ENSO) episodes. This result is explained by using a hypothesis stating that non-radiative forcing connected to the ENSO is dominating the temperature changes during those two periods and that there is a lag between the temperature change and the radiative flux feedback. According to the hypothesis the slopes of the straight lines equal the value of the climate feedback parameter. By linear regression based on the mentioned five year period the value of the climate feedback parameter was estimated to 5.5 ± 0.6 W m−2 K−1 (± two standard errors).

 Discussion Paper (PDF, 609 KB)   Supplement (213 KB)   Interactive Discussion (Open, 0 Comments)   Manuscript under review for ESD   

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