date: Thu, 20 Dec 2007 16:39:06 -0000 from: "Robert Matthews" subject: Re: BBC Focus magazine to: "Phil Jones" Great - thanks ! I see the story has been picked up on CC-NET; perhaps you should post this really handy rebuttal on there, before this story "gets legs" and is picked up by all the usual suspects (It's the Christmas silly season, and the papers are desperate for stories.....). Robert ----- Original Message ----- From: [1]Phil Jones To: [2]Robert Matthews Sent: Thursday, December 20, 2007 4:32 PM Subject: Re: BBC Focus magazine Robert, This story has been doing the rounds for the last 18 months. There is nothing new in it. It's been wrong every time it's been used. It comes from people who have no comprehension of the climate system. I was surprised this time, as I thought this writer ought to have know better. Just look at the global temperature series that you now have the associated errors for. There is a lot of variability on the annual timescale. A lot of this is just natural variability of the climate system. The trend is upwards. Some of the variability of the global temperatures is caused by El Nino/La Nina events. El Nino tends to make the world warmer and La Nina cooler. A measure of El Ninos is the Southern Oscillation Index (the difference in pressure between Darwin and Tahiti). When you regress this against global temperature you can explain quite a bit of the high-frequency variance due to the major El Ninos and La Ninas that have occurred since the mid-19th century. I wrote about how to do this in 1990 (see the pdf). The upshot of this is that 1998 is about 0.15 deg C too warm because of the 1997/98 El Nino influence - this El Nino being the biggest of the 20th century. So 1998 could be considered the problem, not the later years. There hasn't been much of an influence either way for the last 6-7 years. So if 1998 is reduced by 0.15, we would have all 7 warmest years as the warmest 7. Another way of looking at this is that all 7 years (2001-7) have a global temperature anomaly above 0.4 deg C. The only year before this with a value above 0.4 is 1998 (with 0.52). The last 7 years contain the second through eight warmest years in the series. Finally, as a climatologist, I wouldn't look at a temperature trend over such a short period as 10 years. I know, as you now do, that the global temperature series has error estimates. Given these errors, it would be impossible to get a statistically significant trend for any 10 year set of global temperature data chosen from any period in the global temperature record. It is likely that you will get a few periods that might be significant, but then you have to consider that you'd expect about 5% of samples significant. So, knowing this, put the global T numbers for 1998 to 2007 into an excel spreadsheet and calculate the trend. It isn't significant - it definitely isn't allowing for the errors. Despite this the trend is POSITIVE. So despite starting with the warmest year, a linear trend fit through the 10 years from 1998 to 2007 gives a POSITIVE trend. So the world is warming.... It will continue to, it just won't be a monotonic increase. It hasn't been like this in the past, and it won't be like that in the future. There is a case for the temps to have risen in a series of steps --- well to my eye anyway. The 1998 record will get broken - we just need the next reasonable sized El Nino. Cheers Phil At 16:07 20/12/2007, you wrote: Hi Phil Thanks again for your help with the global warming figures. As it happens, the New Statesman has just published a piece about whether global warming is still continuing (it's here: [3]http://www.newstatesman.com/200712190004 ). I'd very much welcome your views on it. Best wishes Robert ----- Original Message ----- From: [4]Phil Jones To: [5]Robert Matthews Sent: Tuesday, December 18, 2007 10:07 AM Subject: Re: BBC Focus magazine Robert, The attachment has the information you are after. This also has the full press release - all the background information that journalists could have asked for on Dec 13. This should have gone out from the World Met Organization from Geneva on Dec 13 as well. The error ranges are shown in 2 different ways. 1 . Figure 1 (95% confidence values - so 'true' value will be in the range 19 times out of 20) with the global T values ranked from highest to lowest. 2. Figure 2 (top panel for the Globe, but also with the NH and SH there as well). These are the same values (and ranges) as in Figure 1 but plotted as a time series (the usual way). You'll see the errors are larger further back in time - especially in the 19th century. This is because there are fewer obs and the coverage gets sparser as regions drop out. 2007 has slightly wider error bars as we've estimated December. There are plots for smaller regions - the tropics, extratropics (30-90degrees N or S), arctic and antarctic sea ice areas, and some more local series for the UK. Cheers Phil At 18:24 17/12/2007, you wrote: Dear Professor I'm putting together a piece about the current rate of global warming, and was very interested in the data presented at Bali as summarised by the BBC News website here: [6]http://news.bbc.co.uk/1/hi/sci/tech/7142694.stm As the values are point-estimates extracted from a large number of measurements, presumably they should have some kind of standard deviation error bars associated with them. I wondered if you either knew the approximate size of these error bars (or even a graph showing them)? Thanks so much for your help with this. Best wishes Robert ------------------------------------------------------------------------------ Robert Matthews Science Consultant, BBC Focus Magazine 47 Victoria Road, Oxford, OX2 7QF UK Email: [7]rajm@physics.org [8]www.focusmag.co.uk Tel: (+44)(0)1865 514 004 / Mob: 0790-651 9126 ----------------------------------------------------------------------------- Prof. Phil Jones Climatic Research Unit Telephone +44 (0) 1603 592090 School of Environmental Sciences Fax +44 (0) 1603 507784 University of East Anglia Norwich Email p.jones@uea.ac.uk NR4 7TJ UK ---------------------------------------------------------------------------- __________ NOD32 2729 (20071218) Information __________ This message was checked by NOD32 antivirus system. [9]http://www.eset.com Prof. Phil Jones Climatic Research Unit Telephone +44 (0) 1603 592090 School of Environmental Sciences Fax +44 (0) 1603 507784 University of East Anglia Norwich Email p.jones@uea.ac.uk NR4 7TJ UK ---------------------------------------------------------------------------- __________ NOD32 2738 (20071220) Information __________ This message was checked by NOD32 antivirus system. [10]http://www.eset.com