Articles Tagged "David Whitehouse"
Sorted by: Date Posted
Wednesday, October 10th 2012, 10:12 AM EDT
The new and improved global temperature database, Hadcrut4, has been updated at last. Previously it had been complete to 2010. Hadcrut4 is a combination of Crutem4 and Hadsst3 – land and ocean data – that includes better sampling of the Arctic – the most rapidly warming region on Earth. When Hadcrut4 first came out it ended in 2010 that was the warmest year in the dataset. This was used in trend analysis to imply a recent temperature increase.
When I first looked at Hadcrut4 I was aware that when the 2011 data was included it would almost certainly show a reduction in global temperature, and hence alter the tone of the implications that were inferred after its debut. Looking at the differences between Hadcrut4 and Hadcrut3, whose data was up to date, I estimated that Hadcrut4 for 2011 would be 0.400. This attracted some criticism. It is pleasing to note therefore that in the updated Hadcrut4 dataset 2011 has a temperature anomaly of 0.399!
Tuesday, October 2nd 2012, 7:25 AM EDT
Much has been written about the record low extent of Arctic sea ice this season. In July it stood at 7.94 million sq km – 2.12 million km below the 1979 – 2000 average, and in September it reached a record low of 3.14 million sq km.
When satellite monitoring of the Arctic ice began in 1979 it was clear that the data had caught a decline already in progress. There is some evidence that the decline may have been taking place since the 1950s, which is before the time that anthropogenic influences came into effect.
In the past few years it is possible that this roughly linear decline may have increased, or have reached a point whereby the behavior of the Arctic ice sheet has changed. 2007 was a record low year for ice extent and it may be that the ice melt-freeze cycle has become noisier. Figure 1.
Thursday, September 20th 2012, 9:48 AM EDT
In the past few years it has been the desire of some scientists to link extreme weather events to climate change. Climate change has become climate disruption.
The idea is to take the real world and compare it to a model one, a world in which mankind has had no influence. There should be a difference due to the increased temperature affecting parameters like humidity that will cause human-induced changes in hot spells, droughts, rainfall, hurricanes etc. The problem is, of course, in modeling the world without humans when we don’t know the way the world would have been without us, or exactly how the world has changed with us.
Friday, September 7th 2012, 10:32 AM EDT
That the Little Ice Age (LIA) – a cooling centred on the 17th Century – took place is beyond doubt. What is questioned however is its spatial extent and its cause. Reading the last document produced by the IPCC on the subject of the LIA one is left in no doubt that it thinks it was a mainly European event.
It states: Evidence from mountain glaciers does suggest increased glaciation in a number of widely spread regions outside Europe prior to the 20th century, including Alaska, New Zealand and Patagonia. However, the timing of maximum glacial advances in these regions differs considerably, suggesting that they may represent largely independent regional climate changes, not a globally-synchronous increased glaciation … hemispherically, the “Little Ice Age” can only be considered as a modest cooling of the Northern Hemisphere during this period of less than 1deg C relative to late 20th century levels.
I note that 1 deg C is a “modest cooling” in this context and that such a description is seldom used to describe the smaller amount of recent warming seen in the instrumental global temperature record. Also note that the most used reference of the strong regional variations in the timing, magnitude and character of the LIA is Jones and Mann 2004. So it is that the LIA is typically considered to be a Northern Hemisphere climate phenomenon characterised by alpine glacial advances and relatively cool temperatures observed between 15th to mid-19th centuries. There are signs however that the IPCC will have to reevaluate its stance on the extent of the LIA.
Wednesday, September 5th 2012, 7:21 AM EDT
2012 started off remarkably coolly due to a lingering La Nina. According to the global temperature dataset Hadcrut3 January was the 15th warmest January on record, February the 22nd, and March the 15th warmest. The same unusual coolness is also seen in the NasaGiss database which has January the 17th warmest on record, February the 15th and March the 15th warmest.
In both datasets the Northern Hemisphere Spring was considerably warmer, though not a record in these combined land and ocean datasets. In Hadcrut3 April was the 5th warmest April, May the 4th warmest and June the 5th warmest. In NasaGiss April was the 5th warmest April on record, May the 2nd and June the 4th. July data is so far only available from NasaGiss and it was the 11th warmest July on record.
Monday, July 30th 2012, 2:33 PM EDT
The second series of papers from the BEST consortium analysing global land temperatures have been published. They contain some interesting analyses, and the good thing is that all the working and code is posted online even if the papers have not yet passed peer-review! It includes the first analysis of global land temperature 1750 – 1850. However, the papers suffer from being too ambitious in the face of sparse data, and the conclusions reached by Professor Muller in this accompanying article in the New York Times is too far reaching considering the data he has been studying, and the analysis he presents.
Wednesday, July 18th 2012, 9:11 AM EDT
Anyone who has seen the raw temperature output from a weather station must have wondered at the marvel of averages. The output is all over the place – large fluctuations in temperature from hour to hour and day and night. Yet from those measurements the result is just one number – the monthly average – that finds its way into climate data.
Picking meaningful information from the variable set that are weather stations often seems more art than science; truncated sequences, gaps, changes of equipment, changes of sites, changes in the local environment, to name but a few factors that have to be taken into consideration, or sometimes not taken into consideration.
A new analysis of some of the statistical methods used in getting something out of temperature readings from weather stations carried out by Steirou and Koutsoyiannis of the National Technical University of Athens has been gaining some publicity as its conclusions are startling. The researchers say that the statistical manipulation of the data to correct errors often introduces even greater errors, as well as exaggerating positive trends.
Tuesday, July 10th 2012, 4:43 PM EDT
Fig. 1. Measures of El Nin˜o and of the Southern Oscillation, 1866–2003. The grey curve is a commonly used index of El Nin˜o, the sea surface temperature (SST) anomaly in the NINO3 region of the eastern equatorial Pacific (908W–1508W, 58S–58N). The black curve is the sea level pressure (SLP) at Darwin, Australia, an index of the atmospheric Southern Oscillation. The close relationship between the two indices is evident. (Departures in the earliest part of the record are more likely due to data quality problems than to real structural changes in ENSO.)
The El Nino phenomena is among the most fascinating yet least understood topics of climate science. Every few years a wave of heat and surface pressure changes sweeps across regions of the Pacific. It lasts nine months to two years and has a worldwide effect.
Some believe that the frequency of El Ninos is changing as a result of climate change. I have recently heard it said many times that it is the increased frequency of El Nino and the associated La Nina that has resulted in the flatness of the global annual average temperature in the past decade or so. If true it’s an important observation.
Trenberth and Hoar in 1996 said there is a tendency for more frequent El Nino and fewer La Nina since the late 1970’s which they think is linked to decadal changes throughout the Pacific basin due to global warming. They note a non-El Nino warming between 1990-95 “connected to” the El Nino, which they say is unprecedented in the previous 113 years, and suggest it is linked to increases in greenhouse gasses.
Tuesday, June 26th 2012, 5:01 PM EDT
Schneider et al 2012 in a poster presentation to the two-day, “Taking the temperature of the Earth Conference,” that ends today, has the clever idea of looking at the temperatures of lakes and reservoirs around the world. They point out that in situ observations of lake surface temperatures are very rare on a global scale, but infrared imagery from space can be used to infer water surface temperatures of lakes and reservoirs.
They provide data for 169 of the largest inland water bodies world- wide using three satellite-borne instruments. Together they provide daily to near-daily data from 1981 through to the present, allowing them to calculate 25-year trends of nighttime summertime/dry-season surface temperature.
Monday, June 18th 2012, 9:28 AM EDT
In terms of global temperature 2012 is turning out to be a very interesting year. Monitoring this year’s temperature is however less thorough than for many years as the newly established Hadcrut4 database is still not updated beyond the end of 2010, and the dataset it’s replacing, HadCrut3, though still being updated, has not had a new entry since March 2012. This is a rather poor performance on behalf of the UK Met Office.
What Hadcrut3 does show is that the first three months of 2012 were way outside the top ten starts to any year in their database. January was the 16th warmest, February the 22nd and March the 15th warmest.
NASA’s Giss dataset started the year in the same way; January was the 17th warmest January, February the 16th and March the 15th. Then the Boreal Spring started to get considerable warmer. April was the 5th warmest on record and May the second warmest ever, after 2010.