Tag Archives: NCAR

The Sixth US National Climate Assessment

Politics, , , , , , , , , , , , , , , , , , , , , , , , , ,

The Fifth US National Climate Assessment was published in November 2023 during the Biden/Harris administration. Here’s the announcement by Zeke Hausfather on X/Twitter:

The “NCA5” report begins as follows:

The Global Change Research Act of 1990 mandates that the US Global Change Research Program (USGCRP) deliver a report to Congress and the President not less frequently than every four years that “integrates, evaluates, and interprets the findings of the Program and discusses the scientific uncertainties associated with such findings; analyzes the effects of global change on the natural environment, agriculture, energy production and use, land and water resources, transportation, human health and welfare, human social systems, and biological diversity; and analyzes current trends in global change, both human-induced and natural, and projects major trends for the subsequent 25 to 100 years.”

You may well have noticed that Kamala Harris lost the subsequent election? Hence the Sixth US National Climate Assessment will be prepared during the term of the current Trump/Vance administration.

The first move by Trump et al. was for the US Department of Energy to commission a “Climate Working Group” to produce a report catchily entitled “A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate“, which was published in July 2025. The authors of the report were listed alphabetically as John Christy Ph.D., Judith Curry Ph.D., Steven Koonin Ph.D., Ross McKitrick Ph.D. and Roy Spencer Ph.D.

Regular readers will recognise some or all of those names, and it will not surprise you to learn that there was plenty of pushback from a wide range of climate scientists. In particular, the “Climate Experts’ Review of the DOE Climate Working Group Report“, led by Andrew Dessler and Robert Kopp was published at the end of September 2025. This report begins as follows:

Continue reading The Sixth US National Climate Assessment →

Reanalysis of Arctic Climate

Temperature, , , , ,

For years now I’ve been using the convenient tools provided at the NCEP/NCAR reanalysis web site to generate custom maps and time series illustrating the climate of the Arctic. By way of example see last December’s “Post-Truth Global and Arctic Temperatures“:

Prompted in part by the obvious difficulty the different models are currently having in generating accurate short term forecasts for the “New Arctic”, I’ve been recently been comparing assorted reanalysis products. For example the UCAR Climate Data Guide points out that:

NCEP Reanalysis (R2) is better than NCEP-NCAR (R1) but still a first generation reanalysis. It is best to use 3rd generation reanalyses, specifically, ERA-Interim and MERRA.

I recently discovered that Richard James has performed a similar analysis for the Arctic, which can be viewed at:

Arctic Winter Warmth

wherein I mentioned the NOAA ESRL Web-based Reanalysis Intercomparison Tool, which allows you to produce plots and timeseries for arbitrary areas of Planet Earth using NCEP/NCAR, ERA Interim, MERRA-2 and numerous other reanalysis products. Here’s one little example:

NCEPr1-ERA-T2m

which makes it evident that NCEP-NCAR (R1) and ERA Interim have different ideas about surface temperatures in the Arctic. So does MERRA-2!

MERRA2-ERA-T2m

For a graphic example of the differences between the three products here is my version of Richard’s Arctic winter temperature comparison (note that currently ERA data is only available up to January 2017):

NCEPr1-T2-Oct-Jan-2017

MERRA-T2-Oct-Jan-2017

Era-T2-Oct-Jan-2017

Can you spot the difference? In conclusion, here’s the Era Interim version of the High Arctic autumnal 925 hPa temperature trend graph at the top:

ERA-SON-80N-T925