Post by Sara Ganetis on Aug 29, 2013 14:36:40 GMT
I heard on NPR this morning a brief story (click here to listen) about a Nature article published online yesterday titled, "Recent global-warming hiatus attributed to equatorial Pacific surface cooling" by Kosaka and Xie (2013) which can be accessed here.
While I admittedly haven't thoroughly read the article in its entirety, I'll attempt to summarize it here. The authors used the GFDL coupled model run with analysis shown for the 60-year period (1950-2010) with a few differences. In the HIST run they essentially ran it forced with observations of atmospheric composition and radiative forcing. The Pacific Ocean-Global Atmospheres (POGA) experiments were conducted in which they only changed the radiative forcing of the equatorial Pacific and left the rest of the atmosphere and ocean free to evolve on its own. For POGA-H, the radiative forcing in the equatorial Pacific was set to the same as the historical period. For POGA-C, or the control, the radiative forcing in the equatorial Pacific was fixed at its 1990 value. Figure 1 from their text (below as Attachment 1) provides some results from their simulations with the main point being that POGA-H performed similarly to observations (panel a), there is a coupled response between the global-mean surface air temperature (SAT) to anomalies on the equatorial Pacific (panel b) and POGA-H was able to simulate the negative seasonal global temperature trends from 2002-2012 (panel c). So the global-mean surface air temperature is sensitive to what is happening in the equatorial Pacific Ocean and the authors provide dynamical reasons behind what may cause such anomalies in their text. The study also highlights that while the global-mean SAT hasn't accelerated its warming, it may be due to the cooler equatorial Pacific waters absorbing radiation. In Figure 3 of their text (below as Attachment 2) they compare the POGA-H with HIST radiation imbalance at the top of the atmosphere (TOA) and net ocean heat content anomalies. With the exception of a few blips due to the effects of volcanic eruptions, there is a net positive radiative imbalance at the TOA and consistently positive and trending more positive ocean heat content anomalies. Isolating the importance of the equatorial Pacific, the authors provided in their Extended Data Figure 7 (Attachment 3 below) that there is low-frequency decadal variability in the SST anomaly field. The main message is that the global-mean surface air temperature may not be reflecting the overall warming that is occurring due to the regulation of the ocean and the fact that a decadal variability in the anomaly field naturally exists. They assert that after this low-frequency variability changes sign in the equatorial Pacific, that the global-mean SAT should stop its 'hiatus' and continue showing a warming trend.
While I admittedly haven't thoroughly read the article in its entirety, I'll attempt to summarize it here. The authors used the GFDL coupled model run with analysis shown for the 60-year period (1950-2010) with a few differences. In the HIST run they essentially ran it forced with observations of atmospheric composition and radiative forcing. The Pacific Ocean-Global Atmospheres (POGA) experiments were conducted in which they only changed the radiative forcing of the equatorial Pacific and left the rest of the atmosphere and ocean free to evolve on its own. For POGA-H, the radiative forcing in the equatorial Pacific was set to the same as the historical period. For POGA-C, or the control, the radiative forcing in the equatorial Pacific was fixed at its 1990 value. Figure 1 from their text (below as Attachment 1) provides some results from their simulations with the main point being that POGA-H performed similarly to observations (panel a), there is a coupled response between the global-mean surface air temperature (SAT) to anomalies on the equatorial Pacific (panel b) and POGA-H was able to simulate the negative seasonal global temperature trends from 2002-2012 (panel c). So the global-mean surface air temperature is sensitive to what is happening in the equatorial Pacific Ocean and the authors provide dynamical reasons behind what may cause such anomalies in their text. The study also highlights that while the global-mean SAT hasn't accelerated its warming, it may be due to the cooler equatorial Pacific waters absorbing radiation. In Figure 3 of their text (below as Attachment 2) they compare the POGA-H with HIST radiation imbalance at the top of the atmosphere (TOA) and net ocean heat content anomalies. With the exception of a few blips due to the effects of volcanic eruptions, there is a net positive radiative imbalance at the TOA and consistently positive and trending more positive ocean heat content anomalies. Isolating the importance of the equatorial Pacific, the authors provided in their Extended Data Figure 7 (Attachment 3 below) that there is low-frequency decadal variability in the SST anomaly field. The main message is that the global-mean surface air temperature may not be reflecting the overall warming that is occurring due to the regulation of the ocean and the fact that a decadal variability in the anomaly field naturally exists. They assert that after this low-frequency variability changes sign in the equatorial Pacific, that the global-mean SAT should stop its 'hiatus' and continue showing a warming trend.
Fig. 1 (Attachment 1) Fig. 3 (Attachment 2) Extended Data Fig. 7 (Attachment 3)
Nature article: www.nature.com/nature/journal/vaop/ncurrent/full/nature12534.html
NPR New story: www.npr.org/2013/08/29/216415005/a-cooler-pacific-may-be-behind-recent-pause-in-global-warming
Your comments: Below
Nature article: www.nature.com/nature/journal/vaop/ncurrent/full/nature12534.html
NPR New story: www.npr.org/2013/08/29/216415005/a-cooler-pacific-may-be-behind-recent-pause-in-global-warming
Your comments: Below
