James Hansen, one of the world's best climate scientists, is getting little bothered by the nonsense running through the conservative blogs and mainstream media. Today he released response (PDF warning) to address this issue.
Big Correction or Little Correction?
Below is what Hansen calls the more-or-less-automatic US temperature graph. The green line visible on the right illustrates the difference between the correction and the old data:
Below is the comparison of global averages. As you can (or actually can't) see there is no discernible green line. This is because the old and the new line match so closely the difference isn't detectable to the naked eye in this graph. Clearly there was no major revision to global temps like many blogs are saying.
So it seems that a mistake is incredibly small.
Who or What Made the Mistake?
If you read Hansen's PDF you will understand that these graphs are "more-or-less-automatic"-ally generated from "near-real-time data streams" distributed by NOAA. Apparently NOAA changed the format of the near-real-time data streams and failed to notify NASA. So NASA's automated process took the data like nothing had ever happened and generated a graph. An article at the conservative blog American Thinker claims it was a Y2K bug:
It's a wild and technical story of compromised weather stations and hack computer algorithms (including, get this - a latent Y2K bug)This is clearly incorrect. The bug was a result of a lack of communication between two agencies.
US *Global* Warming
Many blogs are making a big deal about 1934 and using this year to debunk the entire theory of global warming. Yet in a 2001 paper James Hansen said the following:
The U.S. annual (January-December) mean temperature is slightly warmer in 1934 than in 1998 in the GISS analysisSo even here there is nothing new. 1934 has been officially ranked hotter than 1998 since at least 2001. Well, at least in the U.S. Yet the differences are so minor that the heat crown could belong to either one. From the same paper:
In comparing temperatures of years separated by 60 or 70 years the uncertainties in various adjustments (urban warming, station history adjustments, etc.) lead to an uncertainty of at least 0.1°C. Thus it is not possible to declare a record U.S. temperature with confidence until a result is obtained that exceeds the temperature of 1934 by more than 0.1°C.But this is for the USA only. If you look at GLOBAL temperatures 1934 is cooler than 1998 by a wide margin.
The Hottest *Global* Year
The UK's Climate Research Unit ranks 1998 while NASA ranks 2005 as the warmest. The difference is because CRU doesn't estimate arctic temperatures in areas where there aren't surface stations to take readings. The arctic is a key difference due to a concept called polar amplification which is the theory that the north pole will heat up faster than the south pole. Polar amplification is one of many smoking guns of global warming.
American Thinker, Revised Temp Data Reduces Global Warming Fever, Marc Sheppard, August 09, 2007
Hansen, J.E., R. Ruedy, Mki. Sato, M. Imhoff, W. Lawrence, D. Easterling, T. Peterson, and T. Karl, 2001: A closer look at United States and global surface temperature change. J. Geophys. Res., 106, 23947-23963, doi:10.1029/2001JD000354.
New York Times, Opinionator