| NIEUW 05-05, vanaf heden is er de rubriek Flitspost in de linker kolom. De links hier leiden naar een nieuwe pagina waar korte artikels geplaatst worden |
A - Do you agree that according to the global temperature record used by the IPCC, the rates of global warming from 1860-1880, 1910-1940 and 1975-1998 were identical?
An initial point to make is that in the responses to these questions I've assumed that when you talk about the global temperature record, you mean the record that combines the estimates from land regions with those from the marine regions of the world. CRU produces the land component, with the Met Office Hadley Centre producing the marine component.
Temperature data for the period 1860-1880 are more uncertain, because of sparser coverage, than for later periods in the 20th Century. The 1860-1880 period is also only 21 years in length. As for the two periods 1910-40 and 1975-1998 the warming rates are not statistically significantly different (see numbers below).
I have also included the trend over the period 1975 to 2009, which has a very similar trend to the period 1975-1998.
So, in answer to the question, the warming rates for all 4 periods are similar and not statistically significantly different from each other.
Here are the trends and significances for each period:
| Period | Lenght (years) | Trend (ºC per decade) | Significance |
| 1860 - 1880 | 21 | 0,163 | Yes |
| 1910 - 1940 | 31 | 0,15Â | Yes |
| 1975 - 1998 | 24 | 0,166 | Yes |
| 1975 - 2009 | 35 | 0,161 | Yes |
| 1995 - 2009 | 15 | 0,12Â | No |
| 2002 - 2009 | 8 | - 0,12 | No |
Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.
C - Do you agree that from January 2002 to the present there has been statistically significant global cooling?
No. This period is even shorter than 1995-2009. The trend this time is negative (-0.12C per decade), but this trend is not statistically significant.
D - Do you agree that natural influences could have contributed significantly to the global warming observed from 1975-1998, and, if so, please could you specify each natural influence and express its radiative forcing over the period in Watts per square metre.
This area is slightly outside my area of expertise. When considering changes over this period we need to consider all possible factors (so human and natural influences as well as natural internal variability of the climate system). Natural influences (from volcanoes and the Sun) over this period could have contributed to the change over this period. Volcanic influences from the two large eruptions (El Chichon in 1982 and Pinatubo in 1991) would exert a negative influence. Solar influence was about flat over this period. Combining only these two natural influences, therefore, we might have expected some cooling over this period.
(Jones doet voorkomen dat alle natuurlijke factoren bekend en ingecalculeerd zijn, dit is grote bull.... , zie mijn opmerkingen bij vraag H)
E - How confident are you that warming has taken place and that humans are mainly responsible?
I'm 100% confident that the climate has warmed. As to the second question, I would go along with IPCC Chapter 9 - there's evidence that most of the warming since the 1950s is due to human activity.
G - There is a debate over whether the Medieval Warm Period (MWP) was global or not. If it were to be conclusively shown that it was a global phenomenon, would you accept that this would undermine the premise that mean surface atmospheric temperatures during the latter part of the 20th Century were unprecedented?There is much debate over whether the Medieval Warm Period was global in extent or not. The MWP is most clearly expressed in parts of North America, the North Atlantic and Europe and parts of Asia. For it to be global in extent the MWP would need to be seen clearly in more records from the tropical regions and the Southern Hemisphere. There are very few palaeoclimatic records for these latter two regions.
Of course, if the MWP was shown to be global in extent and as warm or warmer than today (based on an equivalent coverage over the NH and SH) then obviously the late-20th century warmth would not be unprecedented. On the other hand, if the MWP was global, but was less warm that today, then current warmth would be unprecedented.
We know from the instrumental temperature record that the two hemispheres do not always follow one another. We cannot, therefore, make the assumption that temperatures in the global average will be similar to those in the northern hemisphere.
(Jones geeft dus toe dat er duidelijk een Middeleeuwse warme periode was op het Noordelijk halfrond, slechts door gebrek aan data is niet duidelijk of het globaal was. Dit is dan dus nogmaals de doodsteek voor Mann's hockey stick waar Jones toch zelf aan mee werkte. Lees hier verder over deze spagaat.)
H - If you agree that there were similar periods of warming since 1850 to the current period, and that the MWP is under debate, what factors convince you that recent warming has been largely man-made?
The fact that we can't explain the warming from the 1950s by solar and volcanic forcing - see my answer to your question D.
(Dit is een ontstellende uitspraak, het komt neer op 'we weten het niet dus het moet door de mens komen'. Jones weet donders goed dat er talloze factoren zijn die nagenoeg onbegrepen en niet te modelleren zijn zoals bijvoorbeeld waterdamp, wolkenvorming, oceaanwarmtebuffer, kosmische invloeden. En welk scala aan onbekende factoren zullen er nog meer bestaan? Deze uitspraak heeft niets met wetenschap te maken)
K - How much faith do you have - and should we have - in the Yamal tree ring data from Siberia? Should we trust the science behind the palaeoclimate record?First, we would all accept that palaeoclimatic data are considerably less certain than the instrumental data. However, we must use what data are available in order to look at the last 1,000 years.
I believe that our current interpretation of the Yamal tree-ring data in Siberia is sound. Yamal is just one series that enters some of the millennial long reconstructions that are available.
(Weer een niet te volgen redenatie, er is te weinig betrouwbare boomring data maar we moeten toch wat om tot 1000 jaar terug te kijken. Het doel (1000 jaar) is heiliger dan betrouwbaarheid, een leuke werkverschaffing maar ga dit dan niet publiceren en vertel dat de resultaten generlei waarde hebben.
Sallie Baliunas en Willie Soon van Harvard Smithsonian hebben in 2003 al een prima analyse gedaan en daarbij een breed scala van meer dan 20 verschillende proxies gebruikt i.p.v. de 12 Yamal bomen die Michael Mann gebruikte. Zij vonden een significante MWP warmer dan nu en een significante kleine ijstijd. Hun werk kwam echter niet door de peer review van Jones en zijn club)
N - When scientists say "the debate on climate change is over", what exactly do they mean - and what don't they mean?It would be supposition on my behalf to know whether all scientists who say the debate is over are saying that for the same reason. I don't believe the vast majority of climate scientists think this. This is not my view. There is still much that needs to be undertaken to reduce uncertainties, not just for the future, but for the instrumental (and especially the palaeoclimatic) past as well.
(Deze opmerking is cruciaal. Let goed op Al Gore, Jaqueline Cramer, Diederik Samson Femke Halsema, en hele onwetende volkstammen met u: het debat is nog lang niet gevoerd en er is geen consensus)
Q - Let's talk about the e-mails now: In the e-mails you refer to a "trick" which your critics say suggests you conspired to trick the public? You also mentioned "hiding the decline" (in temperatures). Why did you say these things?This remark has nothing to do with any "decline" in observed instrumental temperatures. The remark referred to a well-known observation, in a particular set of tree-ring data, that I had used in a figure to represent large-scale summer temperature changes over the last 600 years.
The phrase 'hide the decline' was shorthand for providing a composite representation of long-term temperature changes made up of recent instrumental data and earlier tree-ring based evidence, where it was absolutely necessary to remove the incorrect impression given by the tree rings that temperatures between about 1960 and 1999 (when the email was written) were not rising, as our instrumental data clearly showed they were.
This "divergence" is well known in the tree-ring literature and "trick" did not refer to any intention to deceive - but rather "a convenient way of achieving something", in this case joining the earlier valid part of the tree-ring record with the recent, more reliable instrumental record.
I was justified in curtailing the tree-ring reconstruction in the mid-20th Century because these particular data were not valid after that time - an issue which was later directly discussed in the 2007 IPCC AR4 Report.
The misinterpretation of the remark stems from its being quoted out of context. The 1999 WMO report wanted just the three curves, without the split between the proxy part of the reconstruction and the last few years of instrumental data that brought the series up to the end of 1999. Only one of the three curves was based solely on tree-ring data.
The e-mail was sent to a few colleagues pointing out their data was being used in the WMO Annual Statement in 1999. I was pointing out to them how the lines were physically drawn. This e-mail was not written for a general audience. If it had been I would have explained what I had done in much more detail.
R - Why did you ask a colleague to delete all e-mails relating to the Fourth Assessment Report of the IPCC?
This was an e-mail sent out of frustration at one FOI request that was asking for the e-mail correspondence between the lead authors on chapter six of the Working Group One Report of the IPCC. This is one of the issues which the Independent Review will look at.
