January 18, 2008
Temperature Trends 1990-2007: Hansen, IPCC, Obs
Posted to Author: Pielke Jr., R. | Climate Change | Prediction and Forecasting | Scientific Assessments
The figure below shows linear trends in temperature for Jim Hansen's three 1988 scenarios (in shades of blue), for the IPCC predictions issued in 1990, 1995, 2001, 2007 (in shades of green), and for four sets of observations (in shades of brown). I choose the period 1990-2007 because this is the period of overlap for all of the predictions (except IPCC 2007, which starts in 2000).
Looking just at these measures of central tendency (i.e., no formal consideration of uncertainties) it seems clear that:
1. Trends in all of Hansen's scenarios are above IPCC 1995, 2001, and 2007, as well as three of the four surface observations.
2. The outlier on surface observations, and the one consistent with Hansen's Scenarios A and B is the NASA dataset overseen by Jim Hansen. Whatever the explanation for this, good scientific practice would have forecasting and data collection used to verify those forecasts conducted by completely separate groups.
3. Hansen's Scenario A is very similar to IPCC 1990, which makes sense given their closeness in time, and assumptions of forcings at the time (i.e., thoughts on business-as-usual did not change much over that time).
The data for the Hansen scenarios was obtained at Climate Audit from the ongoing discussion there, and the IPCC and observational data is as described on this site over the past week or so in the forecast verification exercise that I have conducted. This is an ongoing exercise, as part of a conversation across the web, so if you have questions or comments, please share them, either here, or if our comment interface is driving you nuts (as it is with me), then comment over at Climate Audit where I'll participate in the discussions.Posted on January 18, 2008 11:54 AM
Posted by: lucia at January 18, 2008 08:49 AM
Is that GISS Met Station Data? Or Land Ocean?
I've pretty much convinced myself that the principle of comparing like to like requires us to compare computations to Land-Ocean data whenever possible. The reason I think this is:
1)the GCMs compute surface temperatures including areas over both the land and the ocean.
So, in periods of warming, measurements over land will rise faster (and this is even without considering any heat island effects.)
Of course, as a practical matter, if we distrust the measurements over the oceans, I'd go with the land based only measurements.
Posted by: lucia at January 18, 2008 08:58 AM
Lucia- Thanks (and congrats for getting a comment through;-) I showed Met Stations, Land/Ocean trend is 0.22.
Posted by: Roger Pielke, Jr. at January 18, 2008 09:45 AM
Just for clarity, can you repeat what the scenarios are for the IPCC values for 1990, 1995, 2001, and 2007?
The scenario for 2001 and 2007 is A1F1, right?
Posted by: Mark Bahner at January 20, 2008 11:56 AM
Posted by: Roger Pielke, Jr. at January 20, 2008 02:51 PM
A comment sent in by email from Roger Cohen:
"I think your focus on identifying metrics to track "projections" by the
I believe the number one metric remains global average temperature
To establish a basis for agreement on how to deal with global average
Roger W. Cohen
Posted by: Roger Pielke, Jr. at January 21, 2008 11:32 AM
*If* global temperature would be a good way to track "global warming" the only accurate way to do it would be without any subjective corrections for, e.g., UHI.
That means MSU. Period.
Posted by: Harry Haymuss at January 25, 2008 10:02 AM
Hansen, the IPCC and observational temperature data are being compared and analyzed here through a well read bar chart showing a linear trend in global temperature. Even a layman can gather some idea from this chart.
Posted by: Philips at January 28, 2008 04:17 PM
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