Addressing Questions Regarding the Recent GIA Correction

Edited: 2015-05-04

[Update, 2011/06/20: Media Matters has published a story on the attention our GIA correction has received.]

Regarding the Fox News article by Maxim Lott (derived from previous blogs, e.g., Heartland Institute/Forbes) that questions our application of the glacial isostatic adjustment (GIA) correction to the altimeter-based global mean sea level (GMSL) time series and rate estimates, we would like to direct interest to our Frequently Asked Questions (FAQ) page that discusses the GIA effect and also the differences between our global mean sea level estimates from altimetry and regional/local relative sea level measured by tide gauges. These FAQs were updated in May with content partially derived from the discussion with Mr. Maxim, but much of this important content unfortunately did not get published in the Fox News article or in recent blogs.

We would also suggest consulting the other unaffiliated sea level research groups around the world that independently estimate global mean sea level from altimetry and also apply the scientifically well-understood GIA correction. Their current GMSL rate estimates are listed on the left sidebar of our site for reference. Note that our current rate estimate is actually the lowest of the groups, which does not support the claim that we "doctor the sea level data" to artificially support pro-climate change opinions. Instead, we strive to produce estimates of the global mean sea level time series and rate using the best available information to address the following questions:

  1. How is the volume of the ocean changing?
  2. How much of this is due to thermal expansion?
  3. How much of this is due to addition of water that was previously stored as ice on land?

As the science of sea level change becomes better understood through peer-reviewed research, we include these advances in our global mean sea level estimates. This includes continuously improving some our applied altimetry corrections, such as better satellite orbits, ocean tides, and sea state bias models (all of which, along with the GIA correction, were updated and documented in our last 2011_1 release). For further study, we encourage interested parties to consult the references supplied in the FAQs and cataloged in our library and to also contact other research groups and scientists specifically studying global and regional sea level change.