GRACE’s warts – new peer reviewed paper suggests errors and adjustments may be large

That's a spicy meatball! Credit: U of Texas Center for Space Research

GRACE’s warts – new peer reviewed paper suggests errors and adjustments may be large“. Anthony Watts copies-and-pastes a post from CO2 Science (the website for those tired of “alarmist global warming propaganda”). They report that denialists can safely ignore any troubling conclusions based on the Gravity Recovery and Climate Experiment (GRACE) satellite, because there are “errors and biases” and “the GRACE data time series is still very short”. And of course any adjustments to correct these things are simply ‘tricks’.

Actually, that’s what the GRACE scientists themselves are saying in their 2010 Geophysical Journal International article, Uncertainty in ocean mass trends from GRACE. CO2 Science is taking routine scientific discussion about how to improve data analysis out of context and trying to use it to discredit that very effort. Here’s Quinn & Ponte’s abstract:

Ocean mass, together with steric sea level, are the key components of total observed sea level change. Monthly observations from the Gravity Recovery and Climate Experiment (GRACE) can provide estimates of the ocean mass component of the sea level budget, but full use of the data requires a detailed understanding of its errors and biases. We have examined trends in ocean mass calculated from 6 yr of GRACE data and found differences of up to 1 mm yr−1 between estimates derived from different GRACE processing centre solutions. In addition, variations in post-processing masking and filtering procedures required to convert the GRACE data into ocean mass lead to trend differences of up to 0.5 mm yr−1. Necessary external model adjustments add to these uncertainties, with reported post-glacial rebound corrections differing by as much as 1 mm yr−1. Disagreement in the regional trends between the GRACE processing centres is most noticeably in areas south of Greenland, and in the southeast and northwest Pacific Ocean. Non-ocean signals, such as in the Indian Ocean due to the 2004 Sumatran-Andean earthquake, and near Greenland and West Antarctica due to land signal leakage, can also corrupt the ocean trend estimates. Based on our analyses, formal errors may not capture the true uncertainty in either regional or global ocean mass trends derived from GRACE.

So the controversy is… what exactly? That is a cool warty globe though.

One thought on “GRACE’s warts – new peer reviewed paper suggests errors and adjustments may be large

  1. I imagine it’s to back up a previous ham-handed attempt at criticizing a paper that used GRACE to estimate Antarctic ice mass loss: http://wattsupwiththat.com/2010/06/29/amazing-grace/

    Several commenters attempted to shed light on the basic physics of ice and glaciers (such as why you don’t need temperatures above freezing to lose ice mass), but it was drowned out by Steven’s tantrums. Buried in the actual article itself (which Steven and the others did not read) was an error analysis that took into account PGR and the ocean signals mentioned above. Of course, that doesn’t matter, because it “could have been changes in magma”.

    [No, not the magma!!! – Ben]

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