SMOOTH OPERATORS

In the IPCC Technical Assessment Report of 2007 many of the graphs used smoothed values of data series. This is perfectly valid as it facilitates seeing trends among the year-to-year fluctuations. The methods used are described in 'Appendix 3.A: Low-Pass Filters and Linear Trends'. They use for annual data as filter which has 13 weights 1/576 [1-6-19-42-71-96-106-96-71-42-19-6-1]. An example of this is in figure 3.8. It is interesting to note that have used a algorithm which allows smoothing right to the end of the data series.


We give below the three main global temperature series using the 13 point filter. At the end of the series we used only the part of the filter which applies retrospectively. This curve appears to shows that the rate of temperature increase has fallen off in recent years.




The same annex also mentions using regression to estimate trends. For simplicity we have done this using 13-year series and the LINEST algorithm in Excel.



Using the 13-year period for trends gives the clear impression that the rate of warming has slowed dramatically. Perhaps as a result of this, it is now being suggested that we need at least 30 years to detect a trend. (Though, it should be noted that I can find no reference to the need for a 30-year trend in IPCC report.) In the following graph we have plotted the 30-year trend lines and the 30-year trend from the average of a model ensemble.



Even using the 30-year trend it is clear that rate of temperature increase has fallen back. This graph also shows that the modelled 30-year trend was close to the observed one for the period 1975 to 2005 but outside that period diverged widely.
Comments

IPCC TECHNICAL ASSESSMENT REPORT 5 – THESIS 3

Thesis: The presentation of sea ice in TAR4 used only a sub-set of the data. It should use a wider range of data with reference both to data which were available at the time of TAR4, and data which have become available since.

The technical summary presents the following set of graphs:



The way the graphs are presented is reminiscent of graphs of return on investment of rivals presented by some of the less honest financial intermediaries. Those for the Arctic are presented as anomalies with a scale set so that the full range fits in the rectangle and it seems as if ice extent has fallen close to zero. For the Antarctic, where the area of ice has been tending to increase, they have used the same scale which conveniently minimises the increasing tendency of Antarctic ice.

The following graph presents the same data, updated to May 2010, but as extent not anomalies.




This very clearly shows that on average there are similar areas of sea ice in the Arctic and Antarctic, that the variation is much larger in the Antarctic than the Arctic and the loss of sea ice in the Arctic is only partially balanced by the gain in the Antarctic. A linear regression through the average values suggests that the Arctic has lost 50,000 km2 per year whereas the Antarctic has gained 14,000 km2 per year. The average total area of sea ice 23.9 million km2 so this loss represents a rate of 0.15% a year.

The Synthesis Report also mentions the break-up of the Larsen B ice shelf. This was an area of ice partly floating and partly resting on land and joined to the main Antarctic ice shelf. It was located on the most northerly (i.e. warmest) point of the Antarctic. The area of the ice shelf was 3250 km2 and its weight was 72 billion tons. The loss of the ice shelf has become iconic and it has been compared to the area of Rhode Island or to the trillions of 20 lb bags which could be filled (though not in the IPCC report). In relation to the area of the Antarctic ice sheet it represents only 0.02% of the area or 0.003% of the volume.

We do recognise that the minimum area of sea ice is a useful metric. The albedo (reflectivity) of ice is high and that of sea water is low. In summer, when ice is at a minimum and sunlight at a maximum, the albedo effect is important and the fears that the low Arctic minimum of 2007 could lead to a progressive reduction in sea ice area were valid.

At the time of the TAR4 there was little information available on ice depth and volume. From October 1998 daily values of ice thickness are available from the US Navy polar ice prediction system(PIPS). The forecast values of ice thickness use weather forecasts, and buoys and ice concentration data from the Special Sensor Microwave Image (SSM/I) are used to initialize the system's forecast. The results are available as GIF images. A typical one is given below.





To derive areas and volumes the graphic images were downloaded analysed. The projection used is not an equal area project so the areas derived were approximate. They were based pro-rata on a scanned image of Greenland. During the analysis it was found that the colours representing thickness range 0.5 to 0.75 were never present. It should also be noted that occasionally there were anomalous values, for example for a few days the Caspian and Aral seas were included.

The following graph shows the area and volume of sea ice from October 1998 to May 2010. These figures only apply for ice greater than 0.75 m thick and consequently the areas are less than those of ice extent in the above graph.





In general the volume and area show similar variation but after the low summer minimum of 2007 the ice area recovered well in 2008 but the volume. This is reflected in the chart on ice thickness.





This shows that minimum ice thickness was less in 2008 than in 2007, giving some support to those who said the ice that year was “rotten”. It is interesting to note that the ice thickness is bi-modal; one maximum occurs in May when the ice area has just passed its maximum and the second in September near to the point when it is at its minimum. This can be seen more clearly in the following graph where compare average thickness with current ice thickness.

The shape of the graph suggests that ice thickness is belatedly reaching its spring maximum. How it will develop in the coming months is something we will follow with interest. What these graphs do show is that Arctic sea ice is recovering in terms of volume, are and thickness.



In these “theses” we generally do not concern ourselves with short term effects so to counter that remember that during the last inter-glacial sea levels were 6 m higher than at present. Although melting sea ice does not affect sea levels we can none-the-less expect more melt independent of any anthropogenic effect.

IPCC TAR5: The presentation of graphs data in TAR5 was biased to give an exaggerated impression of ice loss. In TAR5 the presentation should be more balanced. It should use a wider range of metrics to assess changes in sea ice.
Comments

IPCC TECHNICAL ASSESSMENT REPORT 5 – THESIS 2

Thesis: That the discussion of sea level rise in IPCC TAR4 has much to recommend as a model for other topics.

Those of you who have already seen our first thesis, on global temperatures, may have got the impression that we were out to ‘get’ the IPCC. This is not the case. We are self-financed and have no agenda. As we say on our Home Page: “We are trying to prove only one thing: rational debate is possible when participants have access to the facts.”

In TAR4 the increase in sea level is presented in the following graph.





This graph appears as Figure 3 in the Summary for Policy Makers and elsewhere (We have extracted the sea levels from a compound graph which also showed Global Average Temperatures and Northern Hemisphere snow cover). It combines levels from tide gauges (circular dots) and satellite measurements (the red line).

In the summary the accompanying text says: “Global average sea level rose at an average rate of 1.8 [1.3 to 2.3] mm per year over 1961 to 2003. The rate was faster over 1993 to 2003: about 3.1 [2.4 to 3.8] mm per year. Whether the faster rate for 1993 to 2003 reflects decadal variability or an increase in the longer term trend is unclear.” Similar words appear in the Technical Summary and the Synthesis report. What is commendable in this case is that even in the condensed Summary for Policy Makers there is no attempt to attach a high level of significance to the higher rate of sea level rise for the ten years preceding the preparation of the report.

The Technical Summary also states (Paragraph 3.3.3): “The tide gauge record indicates that faster rates similar to that observed in 1993 to 2003 have occurred in other decades since 1950.” This is supported by the following figure in Chapter 5 of the main report.





This contrasts markedly to the global temperature graph we discussed in the previous ‘thesis’. (http://www.climatedata.info/Discussions/Discussions/opinions.php?id=5404421343497121129 ).

There are two areas where the increase could be presented in a wider context in TAR5.

Firstly since TAR4 was written there is more evidence of sea level changes in the last couple of thousand years.





The blue crosses represent relative sea level rise for Vidarholmi in Iceland as calculated by Gehrels et al. No adjustment has been made for post glacial rebound but this is unlikely to have varied substantially over the period of the estimates. The figure before 100 AD may have been modified by compression in the salt marsh sampling area but even so the levels after that date suggest that recent rates of rise are by no means extraordinary.

The green circles show estimates of sea level on the coast of Israel calculated by Sivan and Toker. They are based on archaeological evidence from different broadly defined time periods (e.g. Hellenic or Crusader). The dating and levels are not given to a high degree of accuracy but also suggest that rapid sea level changes might have occurred in the past.

The red line, provided for comparison, is the increase since 1702 based on tide gauges by Jevrejeva et al. This confirms that the rate of sea level increase accelerated around 200 years ago and is not a recent phenomenon.

The second point is that in the previous interglacial sea levels were about 6 m higher than they are today and in other interglacial periods levels were from 3 m to 20 m higher. It is therefore possible than in coming centuries many coastal locations on earth might experience sea level rises of the same order of magnitude as those estimated by Sivan and Toker. That said there are many coastal cities in the world, such as Marseilles, Akko (Acre) and Naples, which existed well before the start of the present era and which have adapted to sea level changes.

IPCC TAR5: The TAR4 dealt with sea level changes accurately and in a responsible way. However the IPCC TAR5 could be improved by expanding information on the context of the projected level changes.

References:
Gehrels et al., Rapid sea-level rise in the North Atlantic Ocean since the first half of the nineteenth century. The Holocene 2006; 16; 949

Shivan and Toker, The Sea’s ups and downs. http://newmedia-eng.haifa.ac.il/?p=2330

Jevrejeva, S., J.C. Moore, A. Grinsted and P.L. Woodworth. 2008. Recent global sea level acceleration started over 200 years ago?, Geophysical Research Letters, 35
Comments

IPCC TECHNICAL ASSESSMENT REPORT 5 – INTRODUCTION

At the start of 2010 the IPCC attracted a lot of criticism for three projected climate change impacts which were poorly supported. These were that Himalayan glaciers might disappear by 2035, that African agricultural yields could fall by 50% and that 40% of the Amazonian rain-forest could react drastically to changes in precipitation. In each case the source of the claim was speculative and lacking sound evidence. The IPCC’s response was that in such a major series of documents it was well nigh impossible to avoid a few mistakes. To some extent this is true but the fact the errors all erred on the side of exaggerating the effects of climate change says much about the IPCC’s lack of balance.

We believe however that there are more serious criticisms which can be leveled against the IPCC.

Science is only as good as its data and in many cases the data presented by the IPCC tell only part of the story.

Since we are criticising the IPCC we should make out own position clear. So where do we stand? We believe that the science and data show unequivocally that temperatures today are higher than would have been case were it not for greenhouse gases emitted by human activity. On the other hand we do not believe that the more extreme forecasts of increased temperatures and their impact have been proven. We also believe that there are good reasons for reducing use of fossil fuels, of which effect on the climate is but one.

We also believe that climate modelling is important for the future. In the past, design of anything affected by weather, urban drainage or water supply for example, has been based on a statistical analysis of past data. It is now clear that a fundamental assumption of such analysis, that the events analysed are independent of each other, is invalid. To be able to predict natural and anthropogenic changes in climate should become the new paradigm for engineering design.

Our position, and that of those who have studied the science and share our views, is similar to that of Martin Luther, the 15th century reformer. He was, and remained all his life, a Christian but he thought that the activities and excesses of the Roman Catholic Church at that time were acting against the faith he accepted. We believe that there is a powerful analogy with the IPCC at the present time. Its performance is such that far from leading the population to accept their assertion that unless radical and immediate action is taking the world will suffer gravely they, by bias and distortion in their arguments, have left many people refusing to accept that humans have any influence on the climate.

Martin Luther put his case by pinning 95 Theses to the door of a church (today he would probably have been a blogger). What we are going to do is to publish a series of ‘theses’ where we highlight some aspects of the IPCC Technical Assessment Report of 2007 (TAR4) which could be improved in the next report (TAR5).

There remains one important question: Why should you believe us? The answer is you won’t have to. For reach of our theses we will give chapter and verse on the section of IPCC TAR4 we are commenting on and the source of the data we use to propose improvements.
Comments
See Older Posts...