New excuse for the ‘pause’ of global warming #58: Colder eastern Pacific and reduced heat loss in other oceans
New excuse for the “pause” of global warming #58: Colder eastern Pacific and reduced heat loss in other oceans
A paper published today in Geophysical Research Letters finds excuse #58 for the 18-26 year “pause” or hiatus” of global warming: Colder eastern Pacific (30% contribution) and reduced heat loss in other oceans (70% contribution). So increased heat loss in the Pacific, and decreased heat loss in the Southern and subtropical Indian Oceans & subpolar North Atlantic allegedly “explain” the “pause.” Natural ocean oscillations could explain this, but not a steady rise of greenhouse gases. According to the authors, however, “A different mechanism is important at longer timescales (1960s-present) over which the [natural] Southern Annular Mode trended upwards. In this period, increased ocean heat uptake has largely arisen from reduced heat loss associated with reduced winds over the Agulhas Return Current and southward displacement of Southern Ocean westerlies.” Surface warming hiatus caused by increased heat uptake across multiple ocean basinsS. S. Drijfhout The first decade of the twenty-first century was characterised by a hiatus in global surface warming. Using ocean model hindcasts and reanalyses we show that heat uptake between the 1990s and 2000s increased by 0.7 ± 0.3Wm−2. Approximately 30% of the increase is associated with colder sea surface temperatures in the eastern Pacific. Other basins contribute via reduced heat loss to the atmosphere, in particular the Southern and subtropical Indian Oceans (30%), and the subpolar North Atlantic (40%). A different mechanism is important at longer timescales (1960s-present) over which the Southern Annular Mode trended upwards. In this period, increased ocean heat uptake has largely arisen from reduced heat loss associated with reduced winds over the Agulhas Return Current and southward displacement of Southern Ocean westerlies.
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New excuse #57 for the “pause” of global warming: Increase in mid- and upper level clouds
Via email from climate data analyst John McLean of the Dept. of Physics, James Cook University, Australia, comes explanation #57 for the global warming “pause,” related to an “increase in mid- and upper level clouds” after 1997, which increased albedo/reflection of sunlight. McLean also finds that “CO2 played little if any part” in the post-1950 global warming, which the IPCC attributes with alleged “95% confidence” entirely to man-made greenhouse gases. He instead finds post-1950 warming explained by natural shifts in ENSO and cloud cover. As he notes, “This means that there is little if any “missing heat” that (supposedly but improbably) 16 years ago decided to start hiding itself away where no-one could find it.” Email from John McLean [emphasis added, h/t Marc Morano/Climate Depot]: My new paper about late 20th century warming is now available via http://www.scirp.org/journal/PaperInformation.aspx?PaperID=50837#.VFQNL2c4B59 I show that the pattern of global average temperature anomalies since 1950 can be described as a sequence of: (a) ENSO shifting from lots of La Nina events and very few El Ninos to the opposite situation (b) from 1988 to 1997 a reduction in the total cloud cover anomaly (c) after 1997 a decrease in low level cloud but an increase in mid and upper level cloud The temperature data is HadCRUT4, the ENSO data the Troup data from Australia’s Bureau of Meteorology and the cloud cover data the D2 dataset from ISCCP. Of the above it was (b) that caused warming of about 0.45C degrees. When I adjusted the data in the often-quoted energy balance diagram by Trenberth et al, I found that the increase in heat absorbed at the Earth’s surface was about 5 watts per square metre, a figure greater than that given by the IPCC 5AR for the extra heat caused by greenhouse gas emissions. If my hypothesis is correct then CO2 played little if any part. This means that there is little if any “missing heat” that (supposedly but improbably) 16 years ago decided to start hiding itself away where no-one could find it. The paper is being discussed on WUWT: http://wattsupwiththat.com/2014/10/30/new-paper-links-warming-since-1950-to-enso-and-cloud-cover-variations/ and on Bishop Hill: http://bishophill.squarespace.com/blog/2014/10/30/mclean-on-clouds.html
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New excuse #56 for the ‘pause’ in global warming: Satellites underestimate cooling from volcanic aerosols – Published in Geophysical Research Letters
New excuse #56 for the “pause” in global warming: Satellites underestimate cooling from volcanic aerosols
A paper published today in Geophysical Research Letters states, “Understanding the cooling effect of recent volcanoes is of particular interest in the context of the post-2000 slowing of the rate of global warming” and finds “recent volcanic events are responsible for more post-2000 cooling than is implied by satellite databases” which “translates into an estimated global cooling of 0.05 to 0.12 °C.” By way of comparison, the IPCC formula claims post-2000 warming from CO2 was 5.35*ln(400/369) = 0.43W/m2 *(3C/3.7Wm-2) = 0.35C warming, which is at least three times larger than the estimated volcanic cooling found from this paper. Therefore, volcanic cooling would not be sufficient to account for the zero degrees global warming post-2000 (actually post-1996). This implies that either this new paper is incorrect regarding volcanic cooling account for the “pause,” or that the IPCC exaggerates climate sensitivity to CO2. Further, even James Hansen admits there have been no large volcanic eruptions post-2000: “Remarkably, and we will argue importantly, the airborne fraction [of man-made CO2] has declined since 2000 (figure 3) during a period without any large volcanic eruptions.” and as demonstrated by the stratospheric aerosol index of volcanic eruptions: How can volcanic aerosols explain the post-2000 “pause” without an increase of volcanic activity?Total volcanic stratospheric aerosol optical depths and implications for global climate changeD. A Ridley et al Understanding the cooling effect of recent volcanoes is of particular interest in the context of the post-2000 slowing of the rate of global warming. Satellite observations of aerosol optical depth (AOD) above 15 km have demonstrated that small-magnitude volcanic eruptions substantially perturb incoming solar radiation. Here we use lidar, AERONET and balloon-borne observations to provide evidence that currently available satellite databases neglect substantial amounts of volcanic aerosol between the tropopause and 15 km at mid to high latitudes, and therefore underestimate total radiative forcing resulting from the recent eruptions. Incorporating these estimates into a simple climate model, we determine the global volcanic aerosol forcing since 2000 to be −0.19 ± 0.09 Wm−2. This translates into an estimated global cooling of 0.05 to 0.12 °C. We conclude that recent volcanic events are responsible for more post-2000 cooling than is implied by satellite databases that neglect volcanic aerosol effects below 15 km.
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