Nicole Mölders has a very important new research paper that is in press. This paper illustrates the issue of what is an adequate spatial sampling of surface climate variables, including the 2m temperatures.
This is yet another illustration of the inadequacy of the use of 2m temperature trends over land, as applied by NCDC, GISS and CRU to construct a multi-decadal global average surface temperature trend.
As we have shown in a number of peer-reviewed research papers, this temperature has a diverse set of biases and uncertainties which make it quantitatively misleading to use as a diagnostic of global warming, and even to monitor regionally averaged temperature anomalies (e.g. see, see, see and see).
The paper is
PaiMazumder D. And N. Mölders, 2009: Theoretical assessment of uncertainty in regional averages due to network density and design. Journal of Applied Meteorology and Climatology. (in press). [the paper will appear here, as soon as the AMS posts]
The abstract reads
“Weather Research and Forecasting (WRF) model simulations are performed over Russia for July and December 2005, 2006 and 2007 to create a “dataset” to assess the impact of network density and design on regional averages. Based on the values at all WRF grid-points regional averages for various quantities are calculated for 2.8o X 2.8o areas as the “reference”. Regional averages determined based on 40 artificial networks and 411 “sites” that correspond to the locations of a real network, are compared with the reference regional averages. The 40 networks encompass ten networks of 500, 400, 200, or 100 different randomly taken WRF-grid-points as “sites”.
“The real network’s site distribution misrepresents the landscape. This misrepresentation leads to errors in regional averages that show geographical and temporal trends for most quantities: errors are lower over shores of large lakes than coasts and lowest over flatland followed by low and high mountain ranges; offsets in timing occur during frontal passages when several sites are passed at nearly the same time. Generally, the real network underestimates regional averages of sea-level pressure, wind-speed, and precipitation over Russia up to 4.8 hPa (4.8 hPa), 0.7 m/s (0.5 m/s), and 0.2 mm/ d (0.5 mm/d), and overestimates regional averages of 2-m temperature, downward shortwave radiation and soil-temperature over Russia up to 1.9K (1.4K), 19Wm-2 , (14Wm-2 ), and 1.5K (1.8K) in July (December). The low density of the ten 100-sites-networks causes difficulties for sea-level pressure. Regional averages obtained from the 30 networks with 200 or more randomly distributed sites represent the reference regional averages, trends and variability for all quantities well.”
The paper also writes
“In the natural landscape differences between the regional averages derived from the real network and the true regional averages may be even greater than in our theoretical study because the real network was designed for agricultural purposes, i.e. the real network represents the fertile soils within the 2.8o X 2.8o areas. Consequently, it may be even more biased to a soil-type than in the simplified WRF-created landscape assumed in this case study.”