>The following graph of global temperature anomalies is from the “The Copenhagen Diagnosis, 2009: Updating the world on the Latest Climate Science.” The report was released today with obvious intent. I scrolled as far as Figure 3, then copied it, and closed “The Copenhagen Diagnosis”. I’d had enough. Please feel free to answer the question asked in the title of this post.
Figure 3 of the “The Copenhagen Diagnosis”
UPDATE (November 25, 2009): In the comments, Alessandro noticed what I did. He wrote, “The smoothing is not declared and probably the final part (‘2000) is corrected.” But I will make my case that those smoothed curves are trends of some sort.
As Alessandro mentioned, they don’t identify the smoothed data. Do the smoothed curves represent filtered data or polynomial trends? If you were to look at the long-term surface temperature anomaly graphs (land, sea, and combined) in Chapter 3 of the IPCC AR4…
…(The authors of the “Copenhagen Diagnosis use the IPCC AR4 as a reference) you’d note that the IPCC’s smoothing methods do show plateauing of temperatures toward the end of the data, in 2005. Refer to Figures 3.1, Figure 3.4 Cell A, Figure 3.6, and FAQ3.1 Figure 1.
Figure 3 from the Copenhagen Diagnosis above, however, does not show the decreasing rate of rise. The above graph shows relatively straight lines over the past decade+. This leads me to believe that the smoothed curves are some type of polynomial trend lines. This is confirmed by the discussion of Figure 3 on page 13 of the “Copenhagen Diagnosis”:
“IPCC AR4 presented ‘an unambiguous picture of the ongoing warming of the climate system.’ The atmospheric warming trend continues to climb despite 2008 being cooler than 2007 (Figure 3). For example, the IPCC gave the 25-year trend as 0.177 +/- 0.052 deg C per decade for the period ending 2006 (based on the HadCRUT data). Updating this by including the last two years (2007 and 2008), the trend becomes 0.187 +/- 0.052 deg C per decade for the period ending 2008. The recent observed climate trend is thus one of ongoing warming, in line with IPCC predictions.
“Year-to-year differences in global average temperatures are unimportant in evaluating long-term climate TRENDS. During the warming observed over the 20th century, individual years lie above or below the long-term TREND line due to internal climate variability (like 1998); this is a normal and natural phenomenon. For example, in 2008 a La Niña occurred, a climate pattern which naturally causes a temporary dip in the average global temperature. At the same time, solar output was also at its lowest level of the satellite era, another temporary cooling influence. Without anthropogenic warming these two factors should have resulted in the 2008 temperature being among the coolest in the instrumental era, while in fact 2008 was the 9th warmest on record. This underpins the strong greenhouse warming that has occurred in the atmosphere over the past century. The most recent ten-year period is warmer than the previous ten-year period, and the longer-term warming TREND is clear and unambiguous (Figure 3).” [Caps are mine for emphasis.]
So if these are, in fact, trend lines, the authors of the “Copenhagen Diagnosis” have created a double-edged sword for themselves. Trend lines can be projected forward in time for use in forecasts. That is one of the intents of trend lines. (The trend line options for EXCEL provide the option for extending the trends.) So eyeballing the trend forecasts onto Figure 3, we see a continuous warming over the next decade or two, as the authors intended.
Figure 3 of the “The Copenhagen Diagnosis” With Forward Trend Projections
BUT (BIG BUT) those same trend lines can also be used for projections into the past, for hindcasts. Are they now reinstating the Medieval Warm Period?
Figure 3 of the “The Copenhagen Diagnosis” With Backward Trend Projections
And one last note: As quoted above, the authors of the “Copenhagen Diagnosis” stated, “the IPCC gave the 25-year trend as 0.177 +/- 0.052 deg C per decade for the period ending 2006 (based on the HadCRUT data).”
Actually, the IPCC lists that trend for the period ending in 2005, not 2006. Refer again to FAQ3.1 Figure 1 in AR4 Chapter 3. In the description, they write, “Linear trend fits to the last 25 (yellow), 50 (orange), 100 (purple) and 150 years (red) are shown, and correspond to 1981 to 2005, 1956 to 2005, 1906 to 2005, and 1856 to 2005, respectively.” The specific trend values are listed in the artwork.