Our brothers of the FoS sister group show us satellite temperature trends of the lower troposphere since 1979, the start of the satellite record.
The curve is a combination of two satellite global temperature sets, one by the University of Alabama and the other by Remote Sensing Systems. So far, so good!
The best fit line between January 2002 and February 2010 yields a decline of 0.12 C according to FoS. Proponents of conventional regression analysis have argued that the trend since 2002 is actually a positive one, because the starting point of the trend is highly cherry picked in a local temperature maximum but not in an inflexion point, and because the final peak is not considered. The proponents think the yellow line has a better fit. The positive trend becomes clearer, when only considering the temperatures since early 2008. This shows that any short-term trend is possible depending on the starting point selected. What it tells us is that microtrends within a larger trend are not congruent and are not representative of the larger trend.
Apart from that, March 2010 is the warmest March in the satellite record. But…details! The problem of apparent positive trends is solved by tilting the diagram clockwise by about 16 degrees. This removes all doubts!
Now, even the longer-term trend since 1979 (red line) is negative. Nobody claims that a time axis must be strictly horizontal. The earth itself is also tilted. Think big!
Let us now have a look how our cooling trend since 2002 (or 1979) fits into the large scale, i.e. the start of the instrumental temperature record, which approximately coincided with the start of increased CO2 output. The image below shows the instrumental record of global land/surface temperature anomalies as compiled by NASA's Goddard Institute for Space Studies.
If we consider the graph a set of stairs (see stairs drawing by Kurt Tucholsky to the right below), we are now standing at the top (while new stairs are will be added on in the future). Our reference point is the ground floor, i.e. 1880, which broadly concides with the start of the dramatic increase in CO2 emissions. Although we feel safer downstairs, we go steadily up over time, sometimes two stairs forth and one step back. These are the many micro trends on our journey. The overall trend is up in the long term. In fact, any trend larger than a decade and a half since 1880 has been a positive one. So, what are considered meaningful reference points that characterize the staircase as a whole? Clearly the ground level at the start and the top level at the end. The characterization of any temperature trend, long or short term, relies on its starting and end points, and on the resulting slope. Different trends obviously have different starting and end points. So, even if they coincidentally have the same slopes, they are at different elevation levels, i.e. temperature intervals, and hence they are not equal.
Using Tucholsky’s simple sketch as illustration: standing on the middle stair half way up, we deniers conclude that the staircase is flat, because the stair is flat. We do not consider the stair’s elevation with respect to the starting point, i.e 1880. Well, you got the message: any microtrend within a larger trend is not representative of the large trend – only by coincidence. While this complex explanation is needed to convey something every 9th grader understands, it is required to nail it into the stubborn denier brains. Denial is a defense mechanism that does not follow logic! It is classified as a mechanism of the immature mind, because it conflicts with the ability to learn from and cope with reality (source: Wikipedia).
Let’s now look at absolute temperatures all of which are viewed relative to the same reference point of 1880. The NASA hit list of the hottest years is (1) 2005; (2) a cluster of 2009, 1998, 2002, 2003, 2006, and 2007. The current El Niño (added to the other warming mechanisms) lets predict higher temperatures for 2010. The denialists’ inadmissible equation of short term trend (since 2002) and long term trend (since 1880) explains the apparent contradiction of a flat temperature trend in the hottest decade on record. Last but not least the University of Alabama at Huntsville satellite temperatures on their own for the same time interval as the FoS plot above. Spot the global cooling since 2002.
Last but not least the University of Alabama at Huntsville satellite temperature anomalies on their own for the same time interval as the FoS plot above. Spot the global cooling since 2002 (or whenever)?
But we can easily produce an intermediate downwards trend (since 1979, the start of satellite data) by mirror imaging the diagram about a horizontal axis and reversing the time scale. Now we have global cooling on this scale, as indicated by the falling regression line.
The climate trend and best-fit questions are very well discussed in the video by John Sinclair underneath.
Pecuniae Obediunt Omnia!