The orthodoxy has been that as a consequence of greenhouse gas emissions global temperatures will continue to increase. But what is really meant by global temperatures? According to James Hansen from NASA's Goddard Institute for Space Studies even defining surface air temperature is not easy:
"I doubt that there is a general agreement how to answer this question [of what is surface air temperature]. Even at the same location, the temperature near the ground may be very different from the temperature 5 ft above the ground and different again from 10 ft or 50 ft above the ground. Particularly in the presence of vegetation (say in a rain forest), the temperature above the vegetation may be very different from the temperature below the top of the vegetation. A reasonable suggestion might be to use the average temperature of the first 50 ft of air either above ground or above the top of the vegetation. To measure SAT we have to agree on what it is and, as far as I know, no such standard has been suggested or generally adopted. Even if the 50 ft standard were adopted, I cannot imagine that a weather station would build a 50 ft stack of thermometers to be able to find the true SAT at its location."
He is also ambiguous when it comes to daily mean surface air temperatures:
"Again, there is no universally accepted correct answer. Should we note the temperature every 6 hours and report the mean, should we do it every 2 hours, hourly, have a machine record it every second, or simply take the average of the highest and lowest temperature of the day ? On some days the various methods may lead to drastically different results."
Read more here: http://data.giss.nasa.gov/gistemp/abs_temp.html
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"you seem to confuse computer model predictions with reality. We cannot predict weather more than a week ahead, if at that, so where on earth do you get the idea that we can do that for weather 100 years ahead?"
You seem to confuse the weather and climate :).
PeteD
True it is not a blog, but it is not a paper. Which journal was it published in?
Louis: "PeterD
Because it is not a paper per se, but a blog opinion."
You mean this http://www.aip.org/history/climate/co2.htm paper?
As I wrote, Louis, this is material from Weart's book. It's not a blog at all.
Thanks for posting this. I despise the way that the media and NASA report the latest temperature trends and pretend that the temperature of something as vast as the entire planet is a concept that everyone has come to agreement on, and that we have the ability to measure it with absolute accuracy.
Louis does a runner - it's normal behaviour Peterd - he never engages. Would also involve him confronting his demons.
JR You sure about that? How long have we been recording sea ice quantities? I have seen reports of no ice at 81 degrees in 1922. How do we predict something we no damn all about? Last northern summer Arctic ice was very low but Top Gear drove from Resolute Bay to the North Pole. At the same time explain why Antarctica is getting larger and colder.